Rno Principles - Interim Version

Radio Network Optimisation Principles Instructor: Dr Tony Vernon

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

1

Overview of entire five day course What will be learned over the next five days Why this is important in the context of radio network optimisation

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

2

Overview of Day 1

First, Second and Third Generation Networks Introduction to Generic Radio Access Networks Radio Propagation Theory Multiple Access Schemes The GSM 2G Air Interface UTRAN – The UMTS 3G Radio Access Network The Upgrade Migration Path 2G > 2.5G > 2.75G > 3G

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

3

Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks

1st Generation Analog Networks Coverage on Regional Basis

Town 2

Town 1

Out of Town High Sites Cell Radii 5-20km Mobile coverage targeted No express indoor coverage Later deployments reduced cell size and emphasised indoor reliability (1990-)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Town 3

Town 4

4

Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks

2nd Generation Digital Networks Smaller cell size Sectorisation to reduce interference

Town 1

Tighter frequency reuse More robust, digital modulation schemes Advanced understanding of differing requirements for Urban, Suburban and Rural/Road coverage Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

5

Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks

2nd Generation Digital Networks (cont.) The ‘Air Interface Wars’ IS-95 CDMA advocated by Qualcomm + acolytes GSM advocated by LM Ericsson + acolytes Claim & counter-claim for spectral efficiency, immunity from interference, adaptability to different coverage scenarios etc. GSM now by far the dominant 2G standard, 80.79% of all connections to cdmaOne (=IS95 CDMA) 0.22%* *source: GSM Association http://www.gsmworld.com/news/statistics/pdf/gsma_stats_q2_08.pdf

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

6

Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks

3rd Generation Mobile Networks 3G rollout less driven by coverage scenario, more oriented toward usage scenario

Source: Morawek, R and Özcelik, H “General UMTS Network Architecture” http://www.morawek.at/roman/papers/umts.pdf Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

7

Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks

3rd Generation Mobile Networks (cont.) Development of 3G standards started in early ’90s, at launch of the first 2G GSM and cdmaOne networks Another air interface ‘Holy War’ with wideband CDMA prevailing for the air interface and GSM RAN behind this A number of multiple access schemes standardised by the ITU, of which 3GSM (UMTS) and the CDMA 2000 variants are most widespread China, which adopted GSM in the 2G era, has mandated TD-SCDMA as its preferred 3G standard, which may aid the rollout of this air interface to other territories Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

8

Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks

2G Standards offered a single (low) data rate everywhere The ITU mandated “graceful degradation”, or gradually falling bit rate for 3G, with increasing distance from the 2Mb/s Radio Base Station Up to 2Mb/s close to site (~10m) Up to 768kb/s in vicinity of site (~100m)

768kb/s

384kb/s

Up to 384kb/s in general area of site (~1km) Up to 144kb/s (2B+D ISDN) elsewhere Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

144kb/s

9

Day 1 Section 2 – Introduction to Radio Access Network

Section Overview Objective of Radio Network Planning (RNP) Operator Perspective of RNP RNP Technology and Automation Relationship between RNP and Frequency Planning Radio Propagation Principles (Reflection, Refraction, Diffraction, Absorbtion, Multipath)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

10

Day 1 Section 2 – Introduction to Radio Access Network

The Radio Access Network governs one third of the users’ overall experience and 100% of users’ quality of service

Both users and the operator interact with external networks via the Network Subsystem Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

ers rib

Su bs c

E

BS S/ MS R A /U N

OSS S NS l na s ter Ex twork Ne

The operator interacts with the network and users via the Operations Subsystem

Operator

Adapted from Mouly & Pautet, ‘The GSM System’

11

Day 1 Section 2 – Introduction to Radio Access Network

Operator view of RNP Base Station Subsystem defines 100% of users’ technical experience with the operator (ignoring NSS faults) Operator can differentiate itself from other mobile networks in the territory by investing in the RAN CAPEX sunk into RAN precedes operating profits with no direct ‘return on investment’ Many 3G networks built on top of existing 2G properties 2G site topology not necessarily suitable for 3G Operators in mature markets outsourcing their RNP Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

12

Day 1 Section 2 – Introduction to Radio Access Network

RNP Technology – Rudimentary Calculate approximate cell radius for differing ‘clutter’ types Clutter maps common for at least rural, suburban, urban and dense urban Perform ‘best fit’ of cell coverage areas to clutter map, bearing in mind handover overlap Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

13

Day 1 Section 2 – Introduction to Radio Access Network

RNP Technology – Sophisticated Signal from each sector computed from clutter type in which it is located

Town 2

Town 1

Not necessary to maintain site raster or orientation Software fits sites so that entire region to be served has coverage at least to minimum field strength

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Town 3

Town 4

14

Day 1 Section 2 – Introduction to Radio Access Network

Simple (Omni) Frequency Planning GSM900 = 124 ARFCNs Operator allocation = e.g 45 ARFCNs Divide up into 7 ‘reuse’ groups 6 ARFCNs per site = (6 x 7) + 3 spare for special purposes A connection suffers interference from up to 6 neighbours Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

15

Day 1 Section 2 – Introduction to Radio Access Network

Simple (Sector) Frequency Planning Operator allocation = e.g. 45 ARFCNs Divide frequencies per site by number of sectors, e.g. (2 x 3 x 7) + 3 Connection is now interfered by only 3 other neighbours Sectorisation reduces capacity Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

16

Day 1 Section 2 – Introduction to Radio Access Network Serving Site

Adjacent Site

Signal Strength

Reuse Site

Reuse Site

Adjacent Site

Interference approximately constant over service area of site =

+

+

-14

-13

-12

-11

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

-10

-9 -8 -7 -6 -5

Interference ‘wash’ from more distant reuse sites -4

-3

-2 -1 0 1 2 3 Distance from Site (km)

4

5

6

7

8

9

10

11

12

13

14 17

Day 1 Section 2 – Introduction to Radio Access Network

Interferer Man-made and Natural Interference

Direct Path

Diffraction

The signal arrives at the mobile terminal via a variety of paths Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Reflections

Refraction

Sources of interference are less well defined. 18

Day 1 Section 3 Radio Propagation Theory

Introduction Radio Propagation Environment Frequency Division Fast and Slow Fading Propagation Loss Propagation Models Doppler Effect Fresnel Zone

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

19

Day 1 Section 3 Radio Propagation Theory

Introduction

I

E

I

Rr

V~

I

R

H

Power expended against the radiation resistance flows away from the antenna in the form of lines of electric potential, E and magnetic induction, H, i.e. Electromagnetic Radiation

I Simple Dipole Antenna

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Current flow in the antenna for a given electrical stimulus is determined by the real and ‘radiation’ resistance of the antenna 20

Day 1 Section 3 Radio Propagation Theory

Radio Propagation Environment Dominant secondary Electromagnetic energy scatterers is scattered from objects in the area of the terminal known as Dominant Primary Water Secondary Scatterers scatterers tower

Close to the terminal, e.g. 30-40m, smaller objects reflect signal, linking to the terminal’s antenna. These are called Primary Scatterers

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Tall building

Other mast

Base site

21

Day 1 Section 3 Radio Propagation Theory

Frequency Division Secondary scatterers link signal from the base site far outside its main service area Coverage Zone Interference Zone

Minimum distance at which ‘red’ frequency can be reused

Pool of frequencies used by the operator is subdivided so that e.g. (f1,f2,f3) are not used within 3 cell radii etc. Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

22

Day 1 Section 3 Radio Propagation Theory

Fading Effects -80

Very Slow Fading

-82

Slow Fading -84

Power -86 (dBm)

Fast Fading

-88 -90 -92 0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Frame Number Acknowledgement: University of Bristol TSUNAMI II Testbed

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

23

Day 1 Section 3 Radio Propagation Theory

Fading Effects (cont.) Fast Fading – due to primary scatterers near MS Slow Fading – caused by secondary scatterers randomly becoming obstructions that cause signal loss Very Slow Fading – used to be relevant when cell sizes were 20km+, caused by random losses when signal diffracts over landscape. Very Slow Fading now absorbed into ‘propagation model’ or factored out as small cell size in modern networks means that topography does not vary significantly within cell coverage area Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

24

Day 1 Section 3 Radio Propagation Theory

Fast Fading Many random, small E-field contributions rand[-j..j]

Object within 30-40m of the terminal link signal in to the antenna

Received Power

rand[-1..1]

|| (rand[-1..1] + rand [-j..j]) ||

Distance/Time Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

25

Day 1 Section 3 Radio Propagation Theory

Slow Fading ‘Propagation’ Loss

Loss 1

Loss 2 Loss 3

Loss 4

A large number of objects, either primary or secondary scatterers, obstruct the path between base site and MS. Each has a random loss between 0dB and Lmax dB Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

26

Day 1 Section 3 Radio Propagation Theory Slow Fading (cont.) BS

L1

rand[0..Lmax]

L2

L3

L4

rand[0..Lmax] rand[0..Lmax] rand[0..Lmax]

L5

L6

rand[0..Lmax] rand[0..Lmax]

L7

L8

L9

rand[0..Lmax] rand[0..Lmax] rand[0..Lmax]

L10

MS

rand[0..Lmax]

900 800

For L=5dB and 10000 samples

Classic ‘Lognormal’ distribution

700 Number of Samples

Slow fading is the outcome of a large number of linked fading processes, and the overall loss is Sum(L1..L10)

600 500 400 300 200 100 0 1 3

5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 Slow Fading Loss (dB)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

27

Day 1 Section 3 Radio Propagation Theory

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

28

Day 1 Section 3 Radio Propagation Theory

Propagation Model As terminal moves away from base station, an increasing average number of objects obstruct the signal

Total propagation loss = free space loss (≥ 1/r²) + obstruction loss (1/[r→r²])

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

29

Day 1 Section 3 Radio Propagation Theory

Propagation Model (cont.) Huygens Principle: each point on a wavefront can be regarded as a source of secondary ‘wavelets’ The envelope of these wavelets, at a later instant, gives a divergent wave with the BS antenna at its centre.

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

30

Day 1 Section 3 Radio Propagation Theory

Propagation Model (cont.) The space between BS and MS antenna can be divided up into a number of ‘Fresnel Zones’, the edges of which correspond to a path length increment of half a wavelength over the direct path between BS and MS p+3λ/2 p+2λ/2 p+λ/2 Resultant p

Huygens wavelets over odd number zones contribute to an increasing resultant amplitude until their edge-toedge phase difference is λ/2

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

31

Day 1 Section 3 Radio Propagation Theory

Propagation Model (cont.) a Received amplitude

b

b

c a d

c d e

e

Obstruction

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

As an obstruction intrudes into the path between BS and MS, the main Fresnel Zones are obstructed and received amplitude at the MS reduces 32

Day 1 Section 3 Radio Propagation Theory

Propagation Model (cont.) Overall progation loss = free space loss (1/r²) + obstruction loss (1/r) + Fresnel loss (1/[/[r→r²])

Free Space Loss A + Br²

Power Received at MS

Free Space + Obstruction Loss C + Dr[2-3] Free Space + Obstruction + Fresnel Loss E + Fr[3.5-5] Distance from Site

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

33

Day 1 Section 3 Radio Propagation Theory

Doppler Effect

MS/UE Locus Dominant secondary scatterers

Frequency domain is spread by Doppler

Primary scatterers

f

f-fd

f

f+fd

Time domain is ‘smeared’ by Doppler

Doppler effect increases bit error rate and reduces handover reliability Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

34

Day 1 Section 4 Multiple Access Schemes

A ‘multiple access scheme’ determines how mobile terminals and base stations share the transmission resources to send and receive voice and packet data Four multiple access schemes dominate (in order of increasing complexity CSMA Carrier Sense Multiple Access FDMA Frequency Division Multiple Access TDMA Time Division Multiple Access CDMA Code Division Multiple Access

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

35

Day 1 Section 4 Multiple Access Schemes

CSMA Carrier Sense Multiple Access Base stations and mobiles share all network resources in common Before transmitting, a base station scans and listens on F1-Fn for other sites transmitting on that frequency. If a ‘clash’ is detected, the BS waits a random interval before trying again Mobile Terminals do the same, possibly on a different set of frequencies f1-fn Commonest example - Ethernet Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

F1-Fn

f1-fm F1-Fn

f1-fm f1-fm F1-Fn f1-fm 36

Day 1 Section 4 Multiple Access Schemes

Frequency Division Multiple Access F1,F2,F3 F1,F2,F3

F16,F17,F18 F1,F2,F3

FDMA tries to solve the ‘distant clash’ problem of CSMA by setting a minimum spacing at which a given frequency is used

F13,F14,F15 f1,f2 ,f3

F4,F5,F6 F7,F8,F9

F10,F11,F12

F1,F2,F3

The handset receiving on F1,F2,F3 should not be able to hear or be interfered by the base stations where this frequency group is reused, as a number of cell spacings now intervene

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

37

Day 1 Section 4 Multiple Access Schemes

Time Division Multiple Access Fn+Fn+1+Fn+2 combined into a digital allocation FG

FA

FB FC

FA Where in FDMA each MS used F1, F2 or F3 100% of the time, in TDMA all three MSs use FA 33.3% of the time.

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

FA

FE fA

fA

FD

FA

fA

38

Day 1 Section 4 Multiple Access Schemes

Time Division Multiple Access (cont.) In TDMA a number of narrow FDMA allocations F1

F2

F3

FA are combined into a much wider bandwidth TDMA channel

Frequency

The wider frequency allocation permits a higher digital modulation rate, and therefore a higher carrier bit rate. Each MS shares the frequency resource for a percentage of the time, therefore a TDMA ‘channel’ is a combination of frequency, start and stop times, known as a ‘timeslot’.

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Transmit Power

Frequency

MS1

MS2

MS3

MS1

MS2

MS3

Time 39

Day 1 Section 4 Multiple Access Schemes

Time Division Multiple Access (cont.) Advantages: Reduced Base Station complexity – many FDMA transceivers (TRXs) channels replaced by single TDMA TRX, also reduced combiner complexity Extra data can be incorporated in each TDMA timeslot to permit ‘channel estimation’ on uplink and downlink Digital modulation schemes much more robust against interference, e.g. 8dB margin for GMSK vs 25dB for FM As all information streams are digital, circuit and packet switched data can much more easily be incorporated Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

40

Day 1 Section 4 Multiple Access Schemes

Time Division Multiple Access (cont.) Disadvantages: TDMA modulation schemes (usually a variant of MSK for 2G systems) are much more complex than simple FM modulation and demodulation Capacity can only be added in blocks corresponding to the number of timeslots in a single TDMA carrier, or Absolute Radio Frequency Channel Number (ARFCN). This may be inappropriate for low-traffic rural sites.

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

41

Day 1 Section 4 Multiple Access Schemes

Code Division Multiple Access FA+FB+..+FG combined into one allocation, F F

F

F

F F

f F

In CDMA all BSs share a single frequency allocation. Voice or packet data in low bitrate digital form is multiplied with a much higher bitrate ‘spreading code’. At the receiver the incoming signal is multiplied by a synchronised version of the spreading code and the original information recovered.

F

f F

F

f

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

42

Day 1 Section 4 Multiple Access Schemes

Code Division Multiple Access (cont.)

FA

FB

FC

FD

FE

F Entire Operator Allocation

FG

Frequency

Frequency -f

User Data

f f

-f

f

User Data

RX

TX Spreading Code Spreading Code -f Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

f

-f

f 43

Day 1 Section 4 Multiple Access Schemes

Code Division Multiple Access (cont.) Advantages: Simple BS design, need only one wideband TX and RX Secure – in order to intercept the signal, an eavesdropper needs to know not only the baseband encryption but also the ‘scrambling code’ Wide flexibility in matching user data rate to air interface User data is spread over a wide range of RF frequencies, which reduces vulnerability to frequency-dependent fading. Also allows possibility for use of ‘rake’ receiver to increase the recovered signal by channel matching Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

44

Day 1 Section 4 Multiple Access Schemes

Code Division Multiple Access (cont.) Disadvantages: Increased complexity relative to FDMA and TDMA Requires contiguous block of frequencies at least as large as the baseband spectrum of the spreading code High-power wideband RF amplifiers tend to be inefficient All base stations and all MSs interfere with each other, there is no possibility of setting aside special frequencies or groups of frequencies to manage difficult sites IPR issues – Qualcomm holds many key CDMA patents Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

45

Day 1 Section 5 The GSM Air Interface

GSM, developed in 1980’s by Groupe Spéciale Mobile GSM has a hybrid TDMA-with-FDMA air interface, with origins in UK military comms Aim of GSM was originally to develop a Europe-wide mobile communications system using 900 MHz spectrum that had recently (1982) been harmonised for EU use. The system was designed to access the ISDN. System developed in tandem with the Digital Cellular System, which was an upbanded version of GSM for 1800 MHz frequencies. Systems were referred to as GSM900 and DCS1800 Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

46

Day 1 Section 5 The GSM Air Interface

GSM channel structure First generation systems tended to have FM channels spaced at 25kHz. 8 of these are combined for a single 200 kHz GSM channel

200 kHz

25 kHz

Frequency

Frequency

Gaussian Minimum Shift Keying (GMSK) modulation used, channel width is 260 kHz with 200 kHz channel spacing Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

47

Day 1 Section 5 The GSM Air Interface

GSM Timeslot Structure 8 timeslots of 15/26ms are grouped into 60/13ms frames 60/13ms 4.615ms

15/26ms 577µs

TS0

TS1

TS2

TS3

TS4

TS5

TS6

TS7

Information 57 bits

Training Sequence 26 bits

Information 57 bits

Tail 3 bits

Tail 3 bits

Time

Guard Period 8.25 bits

Signalling 1 bit Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

48

Day 1 Section 5 The GSM Air Interface

GSM Physical and Logical Channels One view is that a physical channel is a combination of frequency, start and stop time (i.e. timeslot) in the frame Broadcast

TACH 1

TACH 2

TACH 3

TACH 4

TACH 5

TACH 6

TACH 7

Time

In successive frames, a physical channel supports one or more logical channels. For example, the TACH/F physical channel ‘multiframe’ has 26 Traffic Channel (TCH) bursts, 1 Slow Associated Channel (SACCH) burst and 1 idle burst T T T T T T T T T T T T T S T T T T T T T T T T T T T I Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

49

Day 1 Section 5 The GSM Air Interface

GSM Broadcast and Common Control Channel At least one basic physical channel on the first GSM carrier, the ‘C0’ carrier, must carry the Broadcast and Common Control Channel 7

0

1

2

3

4

5

6

7

BCCH+ CCCH

TCH

TCH

TCH

TCH

TCH

TCH

TCH

BCCH+ CCCH

TCH

BCCH+ CCCH

TCH

TCH

TCH

TCH

TCH

BCCH+ CCCH

TCH

BCCH+ CCCH

TCH

BCCH+ CCCH

TCH

TCH

TCH

BCCH+ CCCH

TCH

BCCH+ CCCH

TCH

BCCH+ CCCH

TCH

BCCH+ CCCH

TCH

0

Extra BCCH+CCCH blocks are needed in cases of low, medium, high and very high signalling load Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

50

Day 1 Section 5 The GSM Air Interface

51 Frame Structure and Schedule for BCCH+CCCH

time

time/8 TCH

FCCH

SCH

BCCH

CCCH

The Broadcast Control Channel, BCCH, transmits information about the cell The Frequency Correction and Synchronisation Channels FCCH and SCH allow the MSs to find and lock to the cell The Common Control Channel CCCH controls MS access Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

51

Day 1 Section 5 The GSM Air Interface

Frame Structure and Schedule for TACH/F and /H time/8

time

TACH/F

TACH/H, even timeslots

TACH/H, odd timeslots Traffic Burst Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Slow Associated Burst

Idle 52

Day 1 Section 5 The GSM Air Interface

Frame Structure and Schedule for TACH/8 (No.0 shown)

Traffic Burst

Slow Associated Burst

Idle

Traffic and Associated Channel/8, TACH/8 is also known as Standalone Dedicated Control Channel, SDCCH Normally used for call setup and Short Message Service Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

53

Day 1 Section 5 The GSM Air Interface

Structure of GSM Common Control Channel, CCCH On the downlink, the CCCH is shared between the Paging Channel, PCH, and the Access Grant Channel, AGCH

time

time/8 TCH

FCCH

SCH

BCCH

PCH

AGCH

MSs listen to a pre-determined paging channel. When an incoming call arrives the MS transfers to the AGCH In low traffic cells, the AGCH ‘steals’ idle PCH blocks. In high traffic cells, between 2 and 7 blocks are reserved Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

54

Day 1 Section 5 The GSM Air Interface

Structure of GSM Common Control Channel, CCCH (cont.) For low traffic cells, four TACH/8 channels and their SACCHs can be combined onto the BCCH+CCCH BPC

time

time/8 TCH

FCCH

SCH

BCCH

PAGCH

TACH/8

This configuration avoids having to set aside a BPC on a single TRX site for 8 x TACH/8, leaving seven BPCs for traffic Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

55

Day 1 Section 5 The GSM Air Interface

Structure of GSM Common Control Channel, CCCH (cont.) The uplink portion of the BCCH+CCCH BPC is used by the Random Access Channel, RACH. MSs send ‘Access Bursts’ on the uplink RACH in response to pages and to request channels for outgoing calls. For the normal configuration, all uplink timeslots are used by the RACH In the low traffic configuration, the uplink timeslots corresponding to the 4 x TACH/8 channels are not used

time

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

time/8

RACH/H 56

Day 1 Section 5 The GSM Air Interface

Allowed GSM Channel Combination Types Low Traffic Cell, 1 TRX: BPC 0: FCCH, SCH, BCCH, PAGCH/3, RACH/H, 4xTACH/8 BPC 1-7: TACH/F Medium Traffic Cell, 4 TRXs: C0: FCCH, SCH, BCCH, PAGCH/F, RACH/F, 7xTACH/F C1-3: 23xTACH/F, one BPC of 8xTACH/8 High Traffic Cell, 16 TRXs: C0 BPC 0: FCCH, SCH, BCCH, PAGCH/F, RACH/F C0 BPC 2,4,6: BCCH, PAGC/F, RACH/F C1-15: 120xTACH/F, Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

57

Day 1 Section 6 The UMTS Radio Access Network

UTRAN Architecture WCDMA Characteristics Intra and Inter-System Handover in UMTS UTRAN Channel Structure UMTS coverage planning issues UTRAN Evolution

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

58

Day 1 Section 6 The UMTS Radio Access Network

UTRAN Architecture Core Network Iu

Iu Iur

Serving RNC

Iub

Drift RNC

Iub

Iub

Iub

Iub

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

59

Day 1 Section 6 The UMTS Radio Access Network

Designed in support for future transmit diversity, interference cancellation, smart antennas and other advances Robust interference averaging to permit high spectral efficiency

WCDMA characteristics

Support for IP packet data handling, both instantaneously and explicitly through introduction of HSPA extension modes Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Flexible multiplexing of user data, from low bitrate voice to very high bitrate packet Built-in capability to handle multiple services with different QoS and bitrate requirements Many operating modes available to the planner to give high spectral efficiency from macrocell to pico and even femtocell 60

Day 1 Section 6 The UMTS Radio Access Network

Intra and Inter-System Handover in UMTS

3G

3G Intersite Soft Handover

Intersite Hard Handover

3G FII

F

F

F 2G F

F sector 2 Intersystem Handover Intersector Softer Handover

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

F sector 1

FA

61

Day 1 Section 6 The UMTS Radio Access Network

UTRAN Channel Structure Voice

Logical Channel 2G CN

2G BTS

Physical Channel

MS

Fixed Data Voice

Music streaming Video Streaming Downloads www etc.

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Logical Channel(s) 3G CN

3G RBS

Channel code 1

Channel code 2

UE Channel code 3

+control

Transport channel = f (logical channel, transport format)

More physical channels 62

Day 1 Section 6 The UMTS Radio Access Network

UTRAN Channel Structure (cont.) Logical Channel

Broadcast Control Channel (BCCH)

Transport Channel

Broadcast Channel (BCH) Forward Access Channel (FACH)

Paging Control Channel (PCCH)

Paging Channel (PCH)

Common Control Channel (CCCH)

Random Access channel (RACH) Forward Access Channel (FACH)

Common Traffic Channel (CTCH)

Forward Access Channel (FACH)

Dedicated Traffic Channel (DTCH) & Dedicated Control Channel (DCCH)

Forward Access Channel (FACH) Dedicated Channel (DCH) Downlink Shared Channel (DSCH) Random Access channel (RACH) Common Packet Channel (CPCH)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

63

Day 1 Section 6 The UMTS Radio Access Network

UMTS Coverage Planning Issues

2G networks could be planned site by site due to their separation in frequency

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Mutual interference cannot be avoided in 3G networks, so sites have to be identified and planned as groups with benign coverage/interference. These groups are known as ‘clusters’. 64

Day 1 Section 6 The UMTS Radio Access Network

UTRAN Evolution Improved throughput, RTT than existing legacy RAN Seamless incorporation of future HSPA modes, LTE IP network transport replaces ATM Use of open specifications, i.e. IETF Control and User planes allowed to scale independently, i.e. better flexibility and reliability Better native handling of user data at intermediate nodes, e.g. MPLS, deep packet inspection etc

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

65

Day 1 Section 6 The UMTS Radio Access Network

UTRAN Evolution (cont.)

ATM-based transport between RNC and NodeB

IP based transport network management at Layer 3

Centralised ‘Radio Network Controller’

Centralised termination of Iu_control interface in RAN server for RANAP

Radio-specific User Data handling in RNC for Radio Link Control, Medium Access Control

Radio independent control interface

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

SHO support on Iur between merged NodeBs 66

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Review of 3G Evolution GSM vs 3GSM GSM Access and Core Network Spreading and Modulation Link Structures High Data Rate Capabilities Migration Scenarios Packet Switched Networks

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

67

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Review of 3G Evolution

3G >

2.5G PSTN

Internet

PSTN

Internet

MSC server

SGSN

ATM MSC/ VLR C7 Signalling

SGSN A

Gb Gb

A

Iu-CS Iu-PS

Frame Relay

Data

ATM

BSC

BSC Abis

RNC

RNC Abis

BTS

BTS

BTS

BTS

EDGE

EDGE

EDGE

EDGE

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Iu-PS

Iu-CS

ATM

IP

Iubis

NodeB

Iubis

NodeB

NodeB

Iubis

NodeB

2.75G 68

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

GSM vs 3GSM 3GSM/ UMTS

Voice: support for half rate, AMR modes being retrofitted to BSS

Voice: native support for half rate, AMR, DTX, DRX

Data capability up to ~400kb/s via GPRS and E-GPRS

Data capability up to 2Mb/s (R99) and > 10MB/s (HSPA)

Some mobility, relocation

Enhanced radio resource management via 3G-SGSN

GSM

Spectral efficiency ~ 53 users/ 5MHz max. Designed to access the ISDN packet capability retrofitted but never fully exploited

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Spectral efficiency ~ 95 users/ 5MHz max. Designed for advanced IP level access to Internet

69

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

GSM Access and Core Network Base Station Controller

Media Gateway

Abis

PSTN

A Abis A

Base Station Controller

Gb

Gb

MSC Server/ Visitor Location Register

Fixed mapping links

Internet

Packet Control Unit Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Home Location Register

Serving GPRS Gateway GPRS Support Node Support Node

70

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Spreading and Modulation

X

Wideband Modulator

Code Generator

Carrier Generator

Transmitter

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Wideband Demodulator

Carrier Generator

De-spreading

Code Sync/ Tracking

Code Generator

Receiver

71

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Spreading and Modulation (cont.) Multiplication of symbol and chip information ‘spreads’ the spectrum over an extent equal to the baseband chip rate The ratio between chip and symbol rate is the ‘processing gain’

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Processing Gain Gp = Chip rate/ Symbol rate

Symbol rate

Chip rate

2 x Symbol rate

72

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Spreading and Modulation (cont.) Received Data

Local Code

Chip De-Spread Data

0

1

0

Symbol

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

73

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G Link Structures

Downlink Acknowledgement: LM Ericsson Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

74

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Link Structure (cont.)

Uplink Acknowledgement: LM Ericsson

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

75

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

High Data Rate Capabilities High Speed Downlink Packet Access Uses all spare power to transmit two new channel types A-DCH

A-DCH

HS-DSCH HS-SCCH

MSs share the High Speed Downlink Shared Channel Control is via the High Speed Shared Control Channel The link is maintained over A-DCHs between sites Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

76

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

High Data Rate Capabilities (cont.)

Total available cell power

Physical channels associated with HS-DSCH and HS-SCCH consume whatever power is left after common and dedicated channel power has been allocated HSDPA

Dedicated channels (power controlled)

Common channels (not power controlled)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

77

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Migration Scenarios All operators have re-engineered for 2.5G GSM-GPRS 3G-MSC

3G-MGW

3G- SGSN

3G Antennas and feeder ATM 2G BTS

3G RBS/ NodeB RNC

C7/FR BSC

Aggregated Transmission

The main hassle is not hardware but software issues Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

78

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Migration Scenarios (cont.) 2G→3G: Straight swap of BSS for hybrid 2G/3G kit 2.5G→3G: GPRS capability can be upgraded, MSC, SGSN, MGW→3G-SGSN, 3G-MSC, 3G-MGW, add RNCs and Iur, 2G BTS unlikely to be upgradable so replace with new and upgrade transmission to site 2.75G→3G: Probably only need software upgrade in MSC, SGSN, and MGW, add RNCs and Iur, EDGE BTSs likely software or easily hardware upgradable to 3G. Power at each site may need upgraded due to extra loading from 3G RBS. Transmission to sites can probably cope but again may need upgraded Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

79

Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Packet Switched Networks BSC

Very large ATM switch, interfaces IP domain, VPNs and Internet to the SGSN(s) and BSS/UTRAN

IP Domain

Packet Data Protocol

Serving GPRS Gateway GPRS Support Node Support Node

RNC

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

IP Mobility Management, RRM, tracks MSs and UEs at cell level, terminates Packet Data Protocol, performs MSC-like functions in packet domain 80

Overview of Day 2

Basics of Radio Network Planning Radio Network Pre-planning Radio Network Parameter Planning Antenna and Feeder Cable Design

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

81

Day 2 Section 8 Basics of Radio Network Planning

Scope of RNP Cell Shape Elements in a Radio Network Radio Network Planning Process Radio Cell and Wave Propagation Wave Propagation Effects and Parameters

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

82

Day 2 Section 8 Basics of Radio Network Planning

Scope of RNP

RNP occupies the stratum between service area definition and radio network optimisation

No

Define Service Area

Management & Strategy

Select Sites based on local clutter criteria

Radio Planning

All sites acquired?

Site Acquisition & Civils Construction

Yes Simulate coverage and quality Radio Planning Coverage/ quality criteria met? Yes

No

Optimisation Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

83

Day 2 Section 8 Basics of Radio Network Planning

Cell Shape

Due to signal propagation limitations, real-world cell shapes are far different from the idea RNP scenario

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

84

Day 2 Section 8 Basics of Radio Network Planning

Elements in a Radio Network GSM Air Interface

3G Air Interface

Uu Interface Terminal Equipment

Subscriber Identity Module

2G MS Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Mobile Equipment Terminal Equipment

Radio, channel funtionalities User applications

Cu Interface USIM

3G UE 85

Day 2 Section 8 Basics of Radio Network Planning

Elements in a Radio Network (cont.) For a 3G RBS, the term NodeB describes the collection of radio equipment for all sectors. These must be grouped together as a functional unit to permit softer handover

TRXs Single sector shown

Combiner & Filter

BTS Manager Baseband Unit Transmission Power Supply

Generic 2G BTS Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

TRX

RF Filter

Power Supply

Wideband Power Amplifier

Application Manager and Signal Processor Summing and Multiplexing

Input Combiner ATM Multiplexer and Interface Unit

Nokia UltraSite 3G RBS 86

Day 2 Section 8 Basics of Radio Network Planning

Channel Configuration in GSM

Rural Configuration: Single TRX Site, Omni Antennas, Low Capacity

Urban Configuration: 2-4 TRX per sector Site, Sector Antennas, Medium Capacity

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Suburban Configuration: 2-4 TRX per sector, Sector Antennas, LowMedium Capacity

Dense Urban Configuration: 8-16 TRX per sector Site, Sector Antennas, High Capacity

87

Day 2 Section 8 Basics of Radio Network Planning

Radio Network Planning Process Two key steps – site idenfication/selection and coverage simulation Define ‘search radii’, within which option sites are to be identified Simulate area coverage and quality using ‘hot option’ sites (not necessarily best radio quality) Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Town 2

Town 1

Town 3

Town 4

88

Day 2 Section 8 Basics of Radio Network Planning

Radio Cell and Wave Propagation

b2

b3

b1 F(bi,x)

For each location, calculate: Coverage Best Server Mutual Interference Probability Assignment Probability Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

bn

89

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters In free space, electromagnetic wave loss depends only on frequency and distance between transmitter and receiver

Lfs[db] = 10*log(F0/F1) = 32.4 + 20*log(d/km) + 20*log(f/MHz) Antenna Effective Aperture 2f f Half wave dipole

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

90

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.) The propagation of radio waves is more complex, and depends on conditions within the first ‘Fresnel Zone’. This is an ellipsoid of revolution defined by all points where the summed distance between base antenna and MS exceeds free space by half a wavelength

Free space loss can be assumed only if the first Fresnel Zone is unobstructed. This is almost never true. Instead, especially close to the MS there are obstructions due to a) mountains, hills and other terrain profile features and b) buildings trees and other features of the morphostructure. Shadowing and reflections from obstructions in the first Fresnel Zone cause losses that cannot be computed analytically, the planner must choose an appropriate empirical pathloss model Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

91

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.) Rayleigh Fading

Incoming wavefront from base station

N

Field Strength = Σ Ai cos (2πf+∆i)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Received Power

rand[-1..1]

Many random, small E-field contributions from objects 30-40m away from MS

i=1

rand[-j..j]

|| (rand[-1..1] + rand [-j..j]) ||

Distance/Time

92

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.)

A number of objects intervene between base station and MS with random losses between 0 and Lossmax

[0..Lossmax] [0..Lossmax] Number of samples

[0..Lossmax]

Lognormal Distribution

[0..Lossmax]

F ( x; µ , σ ) =

1 xσ 2π

−

e

(ln( x ) − µ ) 2 2σ 2

Loss (dB) Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

93

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.) gheight

The network operator may specify that the network has to be engineered for operation inside buildings and vehicles. This is accounted for as an extra loss on top of that computed from the pathloss model

Flr 11+ - 0.3 dB/flr

Flr 1-10 - 2.7 dB/flr Lin-car ≈ 10 dB Lindoor ≈ 3-15 dB

Lindoor ≈ 7-18 dB

Lindoor ≈ 13-25 dB Lindoor ≈ 17- ∞dB Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

94

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.) The interior of a building is illuminated by only a subset of primary and secondary scatterers

σindoor ≈ 5dB Incoming wavefront

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

The fading statistics of the surrounding environment are superceded by an average set of statistics derived for buildings in the area or country of interest. 95

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.)

Lwater = -5 to -10 dB

For propagation over water, it is usual to remove an amount of pathloss corresponding to the ‘opening’ of the first Fresnel Zone. The propagation loss is then roughly equal to free space loss. The actual loss factor depends on the measured statistics for the area.

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

96

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.)

Summer Winter

For evergreen forests, there is very little difference between summer and winter loss (approx. 6 and 5 dB)

In summer, loss in decidous forest is approx 10dB, in winter approx 5dB

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

97

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.) Why are the fading statistics important? Computer tools calculate average received power

Probability of Received Power

95% of signal samples fall within two standard deviations of the mean value

2σ Received Power (dBm)

If we wish 95% probability of service, we must engineer everywhere for a mean power level 2σ dBm greater than threshold Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

98

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.) Signal Strength

Interference Margin Interference approximately constant over service area of site

Received Power (dBm)

For normal frequency reuse in a GSM system, the background noise level is raised by approximately 2 dB due to system-wide cochannel interference Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Add an ‘interference margin to move the entire received power probability distribution curve up by the amount of the interference introduced

99

Day 2 Section 8 Basics of Radio Network Planning

Wave Propagation Effects and Parameters (cont.) Receiver sensitivity depends on required C/N ratio. When frequencies are reused the the received carrier power must be large enough to combat both noise and interference, i.e. C/(N+I) must exceed the receiver threshold In a normal GSM system, with frequency hopping, dynamic power control and DTC, an interference margin of 2dB is used. Due to the mutual interference of 3G networks, a higher interference margin of 3 dB is used. This varies with traffic, and is called the ‘System Noise Rise’ Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

100

Day 2 Section 9 Radio Network Pre-Planning

Capacity and Quality Site Survey and Site Selection Result of Site Survey Process Frequency Hopping Equipment Enhancements Power Control Handover

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

101

Day 2 Section 9 Radio Network Pre-Planning

Capacity and Quality

Capacity Low bandwidth, bitrate per basic physical channel

Quality High bandwidth, bitrate per basic physical channel

The requirements of capacity and quality conflict in the network design

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

102

Day 2 Section 9 Radio Network Pre-Planning

Capacity and Quality (cont.) Legacy GSM Network, 7 cell repeat

Introduce Half Rate Codec

No change to frequency management structure Full rate codec, 13kb/s, high quality

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

No extra investment in Base Station TRXs etc

Half rate codec, 5.6kb/s, medium/low quality

MSs must support HR 103

Day 2 Section 9 Radio Network Pre-Planning

Capacity and Quality (cont.) Increasing robustness Increasing robustness

12

25

10 Bit Rate (kb/s)

15 10

8 6

8 dB

2.8 dB

AM R 5. 15 AM R 4. 75

AM R 5. 9

AM R 6. 7

AM R 7. 4

H R

AM R 4. 75

AM R 5. 9 AM R 5. 15

0 AM R 6. 7

0 AM R 7. 4

2

AM R 12 .2 AM R 10 .2 AM R 7. 95

5

AM R 7. 95

4

FR

Bit Rate (kb/s)

20

18 dB

Full Rate C/(N+I) for 1% FER

8.5 dB Half Rate C/(N+I) for 1% FER

Channel Coding Source Coding

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

104

Day 2 Section 9 Radio Network Pre-Planning

Capacity and Quality (cont.) 7 cell repeat, 2 TRXs per cell

4 cell repeat, 3-4 TRXs per cell

Introduce AMR Codec

Higher Cell Interference Full rate codec, 13kb/s, high quality

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

AMR codecs, 12.2 – 4.75kb/s, high - low quality

105

Day 2 Section 9 Radio Network Pre-Planning

Site Survey and Selection First Choice Sites

Preliminary Network Design and Analysis Site proposals

Preliminary site selections

● Site survey ● Verification measurements ● Negotiations with owners Detailed network design and analysis Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

106

Day 2 Section 9 Radio Network Pre-Planning

Site Survey and Selection (cont.) The site acquisition process is costly and time consuming Need to consider: Site Access and Availability Installation conditions (antenna mounting and cabling, availability of equipment rooms, possibility of aircon, etc) Available and adequate mains power supply In urban areas: Check antennas can be installed significantly above roof No ‘clipping’ from nearby higher buildings and towers Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

107

Day 2 Section 9 Radio Network Pre-Planning

Results of the Site Survey Process Site too high Site too low Coverage hole

Site missing

Poor handover zone

Ideal coverage scenario Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Multiple street furniture sites

Real-World coverage scenario 108

Day 2 Section 9 Radio Network Pre-Planning

Frequency Hopping Baseband hopping on F1-F4 combats Rayleigh fading for slow moving MSs

Resultant after hopping on F1-F4 Resultant after de-interleaving and error correction

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

109

Day 2 Section 9 Radio Network Pre-Planning

Frequency Hopping (cont.) Need high reliability decoding of the Broadcast and Paging channels, so no frequency hopping on the BCCH/C0 carrier. High quality 7 site or medium quality 4 site repeat F1

F7

F2

F1

F6

F8 F10

F11 F13 F15

F12

F16 F18

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

F5

F3

F9 21 x 200kHz = 4.2MHz

F4

F17 F19

F20

F2

F4 F6

F3

F14

F8 F10

F7 F9

F5

F12

F11

12 x 200kHz = 2.4MHz

F21

110

Day 2 Section 9 Radio Network Pre-Planning

Frequency Hopping (cont.) For the frequencies carrying only traffic channels, these are gathered together in three groups in a 1 x 3 configuration or as a global ensemble in a 1 x 1 configuration and RF/synthesiser frequency hopping employed

1x3 TCH repeat 1x1 TCH repeat

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

111

Day 2 Section 9 Radio Network Pre-Planning

Frequency Hopping (cont.) Power reduction to MS close to the site reduces its C/(N+I) to the minimum acceptable, but also ensured that little interference spills over to MSs in adjacent cells in the same timeslot

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Synthesiser frequency hopping works by trying to average out the C/(I+N) for each MS to the minimum possible 112

Day 2 Section 9 Radio Network Pre-Planning

Equipment Enhancements Two receive antennas are installed at the base location to create RX diversity. With sufficient antenna spacing, the fading processes are uncorrelated between the two antennas. At the receiver, the two received signals are combined bitwise. Where space does not permit two horizontally spaced antennas, a single antenna with two separate cross-polarised brances may be used

For both configurations, GDIVERSITY ≈ 3.5dB in rural areas, and 4.5dB in suburban/urban areas Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

113

Day 2 Section 9 Radio Network Pre-Planning

Equipment Enhancements (cont.) ‘Cell splitting’, where a single existing omnidirectional antenna is changed out for three or more sector antennas, is the simplest form of capacity enhancement. When cells are split, the frequency reuse pattern must be revised.

4 1

2 3

2

1 4

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

114

Day 2 Section 9 Radio Network Pre-Planning

Equipment Enhancements (cont.) If a particularly high site has to be accepted in the planning, the signal coverage may be much larger than intended

The solution is to add a downtilt kit to the top of the antenna, tilting it forward and reducing the coverage area

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

115

Day 2 Section 9 Radio Network Pre-Planning

Equipment Enhancements (cont.) Downtilting can also be used to limit the amount of traffic handled by a cell. The traffic is given by the integral over the area where the site is ‘best server’, i.e. the area where a new call will be assigned to the site, multiplied by the ‘offered traffic’ map

Town 2

Town 1

Town 3

Traffic Erlangs/km² Town 4

0.01 0.1

High Traffic Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

1

10

Lower Traffic 116

Day 2 Section 9 Radio Network Pre-Planning

Equipment Enhancements (cont.) The nature of the constructed network depends on ‘average antenna height’. If a particularly high site is acquired, the antennas must be dropped down the site of the structure

20-30m

In the case of sites which are lower than the specified minimum, a stub mast may have to be constructed to raise the antennas to mimimum height

For a high coverage, medium capacity GSM900 network, the desired antenna height is approximately 30m. For a high capacity GSM1800 or W-CDMA network, average antenna height is 20m Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

117

Day 2 Section 9 Radio Network Pre-Planning

Power Control

MS close to site, downlink power low

Frequency hopping, power control and DTX (Discontinuous Transmission) are essential for good quality with 1 x 3 or 1 x 1 reuse on TCH frequencies User of MS talking, uplink active, downlink inactive due to DTX

MS distant, high power

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

MS in middle of cell, medium power 118

Day 2 Section 9 Radio Network Pre-Planning

Handover During voice calls or data sessions, the MS tries to attach itself to the base site with the lowest pathloss. This ensures that the minimum power necessary to maintain the link is used. This process is called handover. The handover process may fail for a number of reasons, and if so the MS ‘drags’ coverage into adjacent cells Normal Handover Zone

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

119

Day 2 Section 9 Radio Network Pre-Planning

Handover (cont.)

To reduce the number of handovers that would result, a ‘hysteresis’ level is set, which site 2’s received power level must exceed in order to initiate handover. High hysteresis reduces the number of handovers, but increases the risk of coverage dragging. A good compromise value is 3 dB

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Received Power

In the handover zone, shadow fading results in alternating dominance of two base sites. Site 2

hysteresis Site 1

Distance

120

Day 2 Section 10 Radio Network Parameter Planning

Signalling Radio Resource and Mobility Management Basics of Radio Network Optimisation Network Performance Monitoring Network Performance Assessment

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

121

Day 2 Section 10 Radio Network Parameter Planning

Signalling An GSM MS exchanges call setup and control messages with BTS, BSC and MSC. In the same way a 3G UE exchanges similar messages with the RBS, RNC and 3GMSC. These messages can be captured at the radio and network interfaces and used as valuable diagnostic aids 2G MS

BTS

BSC

MSC

RBS

RNC

3G-MSC

3G UE

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

122

Day 2 Section 10 Radio Network Parameter Planning

Radio Resource and Mobility Management Location Area 3 Location Area 1

Location Update Location Update

For paging purposes, sites are grouped into ‘Location Areas’. As the 2G MS or 3G UE moves around, it sends Location Update messages to the Mobility Management function of the network

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Location Area 2 123

Day 2 Section 10 Radio Network Parameter Planning

Radio Resource and Mobility Management (cont.) UE detects mismatch between stored and received Location Areas

RNC

RBS

3G-MSC

Home Location Register

RBS

Location Update Request Radio Resources Reserved

Visitor Location Register

Channel Setup Channel Setup complete Location Update Request Authentication Request Signalling shown for 3G case, 2G similar

Authentication Response

Authentication Information Req Subscriber Information Req

Location Update Successful Radio Resource Release Release

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

124

Day 2 Section 10 Radio Network Parameter Planning

Radio Resource and Mobility Management (cont.)

BA list

Measurement Report

For 2G GSM the BTS sends a Basestation Allocation (BA) list to the MS. The MS uses the BA list as a neighbour list and measures all the frequencies, sending the strongest six back to the BSC in a ‘measurement report’, as potential handover targets. Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

125

Day 2 Section 10 Radio Network Parameter Planning

Radio Resource and Mobility Management (cont.) In both idle and dedicated mode, the MS receives a Basestation Allocation (BA) List from the network This is a list of frequencies and Base Station Identification Codes (BSICs) for neighbouring 2G scrambling codes for 3G base stations In idle mode, the BA list is used by the MS for cell reselection In 2G dedicated mode the MS sends a list of the strongest six received ARFCNs+BSICs to the Radio Resource Management function in the network to permit handover Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

126

Day 2 Section 10 Radio Network Parameter Planning

Radio Resource and Mobility Management (cont.)

Measurement Control Measurement Report Add SHO

Add SHO

In 3G, the UE receives Measurement Control messages from the Radio Resource Management function in the RNC, containing the scrambling codes (SCs) of neighbouring base sites. The UE replies with Measurement Report messages for all decoded SCs, and also requests the RNC to add, drop or modify the serving scrambling codes in Soft Handover. Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

127

Day 2 Section 10 Radio Network Parameter Planning

Radio Resource and Mobility Management (cont.) In 3G dedicated mode, the UE receives a list of neighbouring Scrambling Codes (SCs) via a Measurement Control message from the RNC The Measurement Control message modifies a register in the UE containing SCs the RNC is targeting for handover The UE replies with a Measurement Report message, containing all the validly decoded SCs The UE requests the RNC to add SCs its Active Set, when these would otherwise cause unacceptable interference. When their power level recedes, they can be removed Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

128

Day 2 Section 10 Radio Network Parameter Planning

Basics of Radio Network Optimisation Iur Iubis

L3

Iu

3G-MSC

RNC

Nethawk Occasionally, higher layer messages on the Iu, Iur and Iubis need to be analysed to solve difficult problems Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Analysis of the ‘Layer 3’ Mobility and Radio Resource Management messages between UE and RNC is the majority of RNO 129

Day 2 Section 10 Radio Network Parameter Planning

Basics of Radio Network Optimisation Identify Site Clusters

Test Drive Site Cluster Change Antennas, Downtilts, pans, RAN parameters

Prelaunch Optimisation

Analyse L3 and other signalling data

Identify problem sectors/sites

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

130

Day 2 Section 10 Radio Network Parameter Planning

Network Performance Monitoring Ready parameters, routing tables etc

Gather Key Performance Indicators Analyse and Report

Provision and upload radio network parameter plan, dimension data warehousing and storage Progress reports from site implemenation

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Engineering drivers: performance optimisation and troubleshooting Business drivers: NW expansion and change in offered QoS

Plan coverage / capacity / service / no. of sites enhancement

Schedule

Implementation, logistics, field engineering, site construction and preparation

Project setup

131

Day 2 Section 10 Radio Network Parameter Planning

Network Performance Assessment BSC

MS

MSC Transport Network

BTS

PAIR_INTERFACE

PBTS

PBSC

PMSC

PTRANSPORT_NETWORK

In the 2G case, with only voice and simple data as services, the end-to-end performance is a simple function of the performance of each network element Poverall = f ( PAIR_INTERFACE + PBTS + PBSC + PMSC + PTRANSPORT_NETWORK )

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

132

Day 2 Section 10 Radio Network Parameter Planning

Network Performance Assessment (cont.) AMR12.2 AMR10.2 AMR7.95

FR

AMR7.4 UE

RBS

AMR6.7 AMR5.9

3G Multiservice Environment Voice

RNC

3G-MSC

HR

Transport Network

AMR5.15 AMR4.75 SF8

Video, Streaming, www, downloads etc

SF16 SF32 SF64 SF128

It is impractical to optimise 3G at the individual service level

HSDPA Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

133

Day 2 Section 10 Radio Network Parameter Planning

Network Performance Assessment (cont.) RBS

RNC

3G-MSC

Event Counters

Key Performance Indicators (KPIs) RRC Releases, RAB Setup, Dropped Calls, SF16 Admission Control, etc etc

Call Setup Rate Call Completion Rate

The performance of the network is ‘abstracted’ from the physical services by collecting and processing event counters from RBS, RNC and 3G-MSC Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

PDP Context Activation Rate

134

Day 2 Section 10 Radio Network Parameter Planning

Network Performance Assessment (cont.) Operator needs ability to visualise coverage

Town 2

Town 1

Internal counters for 2G can be e.g. commanded power level, received in call power levels Internal counters for 3G is commanded power level, percentage of calls in SHO, softer HO, handed down to 2G etc

Town 3

Town 4

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

External counters for 2G and 3G are scanner received power level measurements and for 3G, difference between this and RSSI (i.e. Ec/Io) 135

Day 2 Section 10 Radio Network Parameter Planning

Network Performance Assessment (cont.) Capacity only assessed where coverage exists

3G-MSC

Most important counters on the Uu (air) interface, as capacity can be planned on Iu an Iubis

Iubis blocking, configuration etc RNC RBS

Iubis blocking, configuration etc

Capacity can be assessed at either network or cell (hotspot) level

RBS

RBS

Uu blocking rate, Admission Control Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

136

Day 2 Section 10 Radio Network Parameter Planning

Network Performance Assessment (cont.) Quality of Service (QoS) can be set either on the cell or network level Uplink overload

Blocked calls - hardware ‘Soft’ blocking - interference

Downlink overload Call setup failures Hard Handover Failures

QoS Dropped calls

HSDPA MAC-d data retransmissions R99 data retransmissions

Call quality target missed Excess delay and RTT

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

137

Day 2 Section 10 Radio Network Parameter Planning

Network Performance Assessment (cont.)

Starting Parameter Set

Key Performance Indicators Cost Function 1 Cost Function 2

Radio Network Subsystem Simulator

Changed Parameter Values

Cost Function n

We attempt to simplify the optimisation process as a set of ‘cost’ functions that trade off sometimes conflicting parameters Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

138

Day 2 Section 11 Antenna and Feeder Network Design Basics of Antennas

Antenna Selection

Antenna Gain

Current Antenna Use Problems

Directional Diagram

Urban Base Site Antennas

Polarisation

Rural Base Site Antennas

Antenna Diversity

Highway Base Site Antennas

Antenna New Technology

Combining and Distribution Unit

Shaped Beam Technology

Combiner Principles

Intelligent Antennas

Outdoor Antenna Feeder System

Downtilt Planning Downtilt Design

Tower Mounted Amplifiers Feeder Cables

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

139

Day 2 Section 11 Antenna and Feeder Network Design

Basics of Antennas Minimum Radiation Current

Maximum Radiation

Voltage

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

An antenna matches the impedance of the feeder cable, usually 50Ω to free-space impedance of ~ 73Ω. An electric field propagates away from the antenna parallel to the elements and a magnetic field perpendicular 140

Day 2 Section 11 Antenna and Feeder Network Design

Antenna Gain

When n dipole elements are fed by signals in phase, the overall effect at a point in the far field is that the electric field is multiplied by n and the power received by n².

The antenna ‘gain’ is defined relative to the 2.2 dB ‘cardioid’ gain of an individual element, or relative to a fictitious ‘isotropic’ radiator, where all of the power is distributed evenly over 4π solid angle Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

141

Day 2 Section 11 Antenna and Feeder Network Design

Directional Diagram Dipole elements are stacked end on end to form a colinear antenna

RF

From above, the lines of equal electric field strength, or ‘radiation pattern’ form a near perfect circle in the horizontal plane

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

If a long reflector is added close to the colinear, the radiation pattern is biased away from the reflector, creating gain in the horizontal plane 142

Day 2 Section 11 Antenna and Feeder Network Design

Polarisation

E

H TX/RX

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Cellular antennas are usually vertically polarised, parallel to the vertical colinear radiating structures they contain When antenna diversity cannot be used, an antenna with two slant senses of polarisation and separate receive branches may be used to obtain ‘polarisation diversity’ TX/RX

45°

H

E

TX/RX

143

Day 2 Section 11 Antenna and Feeder Network Design

Antenna Diversity

d

By combining the signal from two horizontally spaced antennas, deep fades in the Rayleigh fading processes can be evened out. Combining can either be on a signal level basis or ‘best decoded bit’ at the receiver Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

+

=

144

Day 2 Section 11 Antenna and Feeder Network Design

Antenna New Technology GSM and other 2G technologies not originally designed for ‘advanced’ antenna technologies 3G systems have built-in functionality to assist the lastest generation smart antennas Antenna technology used either to extend coverage range in rural areas or to give immunity to interference in suburban/urban areas Interference reduction in 3G leads directly to capacity gains, but space division multiple access (SDMA) may in future be used to multiply base site capacity Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

145

Day 2 Section 11 Antenna and Feeder Network Design

Shaped Beam Technology

Beam 1 Beam 2

Beam 3 Beam 4

Digital Signal Processing

Range Plan view of shaped beam antenna, four elements

UE falls within extended range of shaped beam 2

RX RX RX RX

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Receiving range of individual sector antenna

146

Day 2 Section 11 Antenna and Feeder Network Design

Intelligent Antennas

UE1

UE2

UEn

Digital Signal Processing

Interferer 1

RX RX

Wanted UE transmits reference information to aid the beamformer

RX Interferer 2

RX Intelligent beamformer creates deep nulls to remove the two interferers, while preserving gain in the direction of the wanted UE

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

147

Day 2 Section 11 Antenna and Feeder Network Design

Downtilt Planning The vertical radiation pattern of the antenna may result in significant overshoot and thus interference in urban areas By vertically downtilting the antenna the interference zone is curtailed. Downtilts between 6°and 10°are used in urban areas

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

148

Day 2 Section 11 Antenna and Feeder Network Design

Downtilt Design Urban areas: It is common to plan with 8° - 10° in the initial phase to create cell dominance in the area close to a site. The downtilt is typically reduced on a site by site basis during optimisation Suburban areas: Dominance is less of a problem, but there is still the potential for interference into nearby urban areas, therefore use 3° - 5° tilt Rural areas: Use a maximum of 4° downtilt for high rural sites. Uptilt if antenna has preset electrical downtilt Consider Remote Electrical Downtilt for easy optimisation Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

149

Day 2 Section 11 Antenna and Feeder Network Design

Antenna Selection Antennas are selected based on the ‘Half Power Beam Width’ (usually abbreviated ‘Beamwidth’) of the horizontal and vertical radiation patterns In rural areas, either omnidirectional 11dB gain antennas or 14-15dB 90° BW types are used

Antenna gain (dBi)

90° 65°

3 6 9 12 15 18

In suburban and urban areas, 17-18dB 65° BW is used Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

150

Day 2 Section 11 Antenna and Feeder Network Design

Antenna Selection (cont.) Why 65°beamwidth?

Nominal Pattern ‘Cloverleaf’ nominal pattern, site at corner, actual measured coverage Hexagonal pattern, site at centre

65°antennas fit very well with the ‘cloverleaf’ repeat pattern used in suburban and urban areas Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

151

Day 2 Section 11 Antenna and Feeder Network Design

Current Antenna Use Problems Site owners nowadays object to normal urban sector antennas One compromise is to build ‘street furniture’ type sites, resembling phone poles or street lighting These sites are aesthetically pleasing, but have poor coverage and performance Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

152

Day 2 Section 11 Antenna and Feeder Network Design

Current Antenna Use Problems (cont.) Street furniture sites are low, typically 10m or less, therefore have poor coverage relative to normal 15-25m high macrocellular sites Street furniture sites must use cross polar antennas, sacrificing 1dB diversity gain, as there is no possibility for horizontal antenna diversity Once constructed, the antenna angular spacing pointing directions cannot be changed, as might be required in optimisation An alternative is to use extremely costly ‘invisible’ sites Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

153

Day 2 Section 11 Antenna and Feeder Network Design

Current Antenna Use Problems (cont.)

Invisibles are extremely expensive, and do not give full access or flexibility with the antenna dowtilt or pans for optimisation Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

154

Day 2 Section 11 Antenna and Feeder Network Design

Urban Base Site Antennas 0° 3 sector sites (very occasionally 4 sectors)

No nearby higher buildings or obstructions

~65°Beamwidth

240°

120°

h=15-25m hant > hclipping

d

Antennas mounted on stub masts sufficiently high to prevent ‘clipping’ of the vertical radiation pattern

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

155

Day 2 Section 11 Antenna and Feeder Network Design

Rural Base Site Antennas Rural site antennas sometimes sectorised but high numbers of omni sites also present – lower requirement for indoor coverage so 90°15dBi gain sector antennas used

3G TX/RX 2G RX

h=15-30m

2G TX/RX 3G RX

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Multi technology rural sites are sometimes complicated by the lack of a multiband omnidirectional colinear

156

Day 2 Section 11 Antenna and Feeder Network Design

Highway Base Site Antennas

90°

65° 33°

Rural sector antenna, reflector bent backwards

Urban sector antenna, straight reflector

Linear highway coverage can be provided with antennas having much smaller beamwidth than rural and urban sites. A beamwidth of 33-36° and gain of 20-21 dBi is used Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

2-sector sites

Highway sector antenna, reflectors bent forwards, two antennas bayed

157

Day 2 Section 11 Antenna and Feeder Network Design

Combining and Distribution Unit Input from/output to Input from/output to Antenna Antenna Hybrid Combiners can combine separate frequencies within a band Frequency 1 Band 1 Band 2 Frequency 2 or frequencies in entirely separate bands 50Ω Load

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

50Ω Load

158

Day 2 Section 11 Antenna and Feeder Network Design

Combiner Principles Diplexers allow sharing of the feeders so only two feeders are required instead of four

GSM Antenna

TX/RX

Both transmit/receive branches are combined on one feeder and both receive branches on the other

WCDMA Antenna

RX TX/RX

RX

Total feeders required are 2 per sector x 3 sectors per site = 6 total feeders GSM BTS Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

UMTS RBS 159

Day 2 Section 11 Antenna and Feeder Network Design

Outdoor Antenna Feeder System The three sectors are connected to the RBS via large diameter low loss feeder cable The feeder cables are run between the RBS and antennas within protective cable trays

Covered cable tray protects feeders

Flexible ‘tails’ at both ends of the feeder cables

Large diameter 7/8” to 1 5/8” cables with flexible jumpers are used to minimise losses between RBS and antennas. Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

160

Day 2 Section 11 Antenna and Feeder Network Design

Tower Mounted Amplifiers TMAs or Mast Head Amplifiers (MHAs) define a low system noise figure MHAs compensate for feeder and combiner losses in the uplink direction, which is important for the higher UMTS frequencies at 2 GHz The uplink is amplified, therefore MSs need less transmit power, especially in indoor settings, extending battery life Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

161

Day 2 Section 11 Antenna and Feeder Network Design

Feeder cables

Outer plastic protective sheath Outer copper conductor Current path on interior of outer conductor (resistive loss) Spacing dielectric, ε+ε’ loss

Air void

Current path on exterior of inner conductor Inner copper conductor

Aim for 3dB max feeder loss 7/8” feeder 3dB = 81m @ GSM900 3dB = 52m @UMTS2100 min bend radius 127mm Diameter 25mm Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

1¼” feeder 3dB = 110m @ GSM900 3dB = 71m @UMTS2100 min bend radius 152mm Diameter 40mm

1⅝” feeder 3dB = 136m @ GSM900 3dB = 86m @UMTS2100 min bend radius 203mm Diameter 51mm 162

Overview of Day 3

Radio Network Design Link Budgets Frequency Planning and Antenna Interference

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

163

Day 3 Section 12 Radio Network Design

Base Station Address Design Design Parameters for Base Station Environment for Antenna Installation Antenna Separation in GSM System Antenna Separation between GSM and UMTS Antenna Installation Interval

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

164

Day 3 Section 12 Radio Network Design

Base Station Address Design Reuse existing 1G, 2G and other technology sites for 3G Where new sites must be built, reuse existing structures e.g. other mobile operators’ masts, other telecoms masts, other structures allowing telecoms, e.g. power pylons Acquisition effort eased by targeting areas where public objections likely to be less, e.g. business parks, industrial estates and business landlords Prefer sites with good clearance above average clutter but invisible from the street, e.g. a 20m mast behind a 15m building is better than a 10m on-street mast Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

165

Day 3 Section 12 Radio Network Design

Environment for Antenna Installation The strongest factor influencing cell coverage and interference range is height above average clutter

30 Height of antenna midpoint over average clutter (m)

Average Clutter Height = 12m

25 20

Average Clutter Height = 15m Average Clutter Height = 20m

15 10

Above average clutter Target antenna height 3-10m

5 Average clutter height

0 -5 -10 -15

0

Target Cell Range Below average clutter 1000 500

1500

2000

Coverage Distance (m)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

2500

3000

3500

Simulations can be done using the COST231 urban propagation model with average clutter height as parameter Antenna heights more than 10m above average clutter contribute more to interference than coverage 166

Day 3 Section 12 Radio Network Design

Environment for Antenna Installation (cont.)

α γ

β α+β+γ < 180 °

Antenna blocking – in order for a site to be accepted, the total blocking angle α+β+γ should be less than 180°and no single blockage should exceed 60°

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

167

Day 3 Section 12 Radio Network Design

Environment for Antenna Installation (cont.) The siting of the antennas must permit for sufficient vertical downtilt, either mechanical or electrical, to permit coverage optimisation

Boresight Horizontal distance from roof edge to antenna (x) 5m 10m 15m 20m 25m 30m

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Min. height of bottom of antenna above rooftop for rural and suburban sites (y) 1.5m 3.0m 4.4m 5.9m 7.4m 8.9m

y

x

Min. height of bottom of antenna above rooftop for dense urban sites (y) 2.3m 4.6m 6.8m 9.1m 11.4m 13.7m

168

Day 3 Section 12 Radio Network Design

Antenna Separation in GSM System Frequency 1 TX

Frequency 2 TX

45 MHz

Frequency 1 RX

Residual interference from frequency 2

Background interference from frequency 2 desensitises receive frequency 1. Horizontal and/or vertical separation is necessary to isolate the two systems

> 1m > 15m > 0.25m

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

169

Day 3 Section 12 Radio Network Design

Antenna Separation between GSM and UMTS GSM TX

~1000 MHz

UMTS RX

Residual interference from GSM

Spatial immunity requirements from GSM to UMTS are broadly similar to the GSM to GSM case, except for the lower antenna coupling on the same face

> 0.5m > 15m > 0.25m

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

170

Day 3 Section 12 Radio Network Design

Antenna Installation Interval

r

During rollout, the actual site pattern will depart from the ideal nominal. However, intersite rules can still be applied depending on whether sectors on neighbouring sites are opposed or interleaved. Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

At the nominal cell planning state, a lookup table approach can be used to determine the maximum cell range, based on the morpho class Cell range

Antenna height=15m Antenna above the clutter. Technology

UMTS

GSM

Dense Urban

650 m

600 m

Sub-urban

1650 m

2000 m

Rural

3650 m

5900 m

Minimum Minimum interleaved site opposed site to site distance to site distance

dopposed

dinterleaved

Technology Dense Urban Suburban Rural

UMTS 900 m 2300 m 5100 m

UMTS 1300 m 3300 m 7300 m

171

Day 3 Section 13 Link Budgets

Understanding the Link Budget Equation

Atmospheric, weather and rain attenuation

Line of Sight (LOS) Path Loss Models

Terrain Factors

The Fresnel Zone Path Loss and Free Space Loss Antenna Gain Frequency Considerations

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Multipath Loss Rician and Rayleigh Fading Co-channel Interference Transmission Line Loss Typical Link Budget Calculation

172

Day 3 Section 13 Link Budgets

Understanding the Link Budget Equation The ‘link budget’ attempts to describe all gains and losses in the end to end path between base site and mobile site and vice versa, relating these to the required signal strength for successful call completion at BTS and MS For the downlink, PRX_MS = PBTS + GANT_BTS + LPATH + LNF > SSREQ_MS For the uplink, PRX_BTS = PMS + GANT_MS + LPATH + LNF > SSREQ_MS SSREQ_MS = SENSMS + RF + IF + BL LNF = Lognormal Fading Margin Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

SSREQ_BTS = SENSBTS + RF + IF RF = Rayleigh Fading Margin 173

Day 3 Section 13 Link Budgets

Line of Sight (LOS) Pathloss Models Pathloss due to terrain and objects around BTS and MS (clutter) can be statistically modelled Non Line of Sight pathloss models are used when there is no visibility between the BTS and the local scattering area around the MS, such as in a microcell Line of Sight pathloss models are used where the BTS antenna can see the locus of the MS LOS models can be further broken down as Point to Area, where only bulk statistics are applied, and Point to Point, where some account is taken of local terrain features Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

174

Day 3 Section 13 Link Budgets

Line of Sight (LOS) Pathloss Models (cont.) Okumura-Hata model: 137.4 + 35.2 log R area

θ2

Modified Deygout model θ1

Pathloss = Fresnel (d1, d2, h = h’1) + Fresnel (d1+d2, d3+d4+d5, h = h”2) + Fresnel (d3, d4, h = -h’3) + Fresnel (d3+d4,d5,h = h’4)

d3

d2

d4 h’3

h”2

θ4

h’4

h’1

d5

T’ d1 T

point Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

M1

R’

M2

M3

M4

R

point 175

Day 3 Section 13 Link Budgets

The Fresnel Zone

Amplitude as obstruction apex clears first Fresnel Zone Unobstructed amplitude

3rd 2nd First Fresnel Zone

d+3λ/2 d+2λ/2 d+λ/2 d

2nd Incoming plane wave

3rd

Amplitude

Obstacle Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Power

Decreasing encroachment 176

Day 3 Section 13 Link Budgets

Path Loss and Free Space Loss If there were no obstruction of the first few Fresnel zones, the signal would propagate as if it were expanding in a sphere, with a d² power law In reality the number of obstructions encountered increases and the lower Fresnel zones are increasingly obscured with increasing distance from the site, so the actual pathloss increases as constant + d3.5-5

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

177

Day 3 Section 13 Link Budgets

Antenna Gain Isotropic pattern GBTS Actual antenna pattern

MS antenna GMS = 0 dB

-5 dBi

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

5 dB loss due to absorbtion from the body

Most antenna gain from focusing the energy in the vertical plane Gain assessed in the link budget as the received power difference between the antenna and the power that would be received from an ideal isotropic radiator In the link budget, the MS is assumed to have a 0 dB gain (isotropic receiver) with a loss of up to 5 dB due to absorbtion from the user’s body 178

Day 3 Section 13 Link Budgets

Frequency Considerations The power P0 received in free space by an MS antenna of gain GMS 2

 λ  P0 = Pt   GBTS GMS  4πd  For real world propagation with MS and BTS heights hBTS and hMS over a conducting plane earth the received power Pr is

 2πhBTS hMS  Pr = 4 P0 sin   λd   2

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

179

Day 3 Section 13 Link Budgets

Frequency Considerations (cont.) Finally for d >> hBTS and hMS the received power is

 hBTS hMS  Pr = Pt GBTS GMS   2  d 

2

which shows a fourth power distance dependency and no frequency dependency. Relative diffraction effects and Fresnel zone losses increase with increasing frequency Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

180

Day 3 Section 13 Link Budgets

Frequency Considerations (cont.) Although plane conducting earth theory gives no frequency dependency for pathloss, empirically it is found that different frequencies have different pathloss characteristics. The ‘Okumura-Hata’ inspired model is Pathloss = A – 13.82 log(hBTS) + ( 44.9 – 6.55 log(hBTS)) log(d) – a(hMS) A vs clutter\frequency

850 MHz

1800 MHz

Urban

146.2

153.8

Suburban

136.4

146.2

Rural

127.1

134.1

Open areas

117.9

124.3

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

a(hMS) = 3.2 ( log(11.75 hMS) ² - 4.97 Where a(hMS) = 0 for the standard MS height 1.5m

181

Day 3 Section 13 Link Budgets

Frequency Considerations (cont.) In urban areas cell sizes can be expected to be very small due to clutter and indoor penetration losses The ‘Okumura-Hata’ model is not valid at these close ranges, and a better approximation by Walfisch and Ikegami can be used Pathloss = B + 38 log(d) – 18 log(hBTS – 17)

B

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

850 MHz

1800 MHz

142.4

153.2

182

Day 3 Section 13 Link Budgets

Atmospheric, Weather and Rain Attenuation 1

Attenuation dB/km

0.1

1 GHz 2 GHz

0.01

0.001

0.0001

0.00001 1

10

100

1000

Rainfall rate, mm/h

The largest effect on propagation at the frequencies of interest, ~1GHz for GSM and 2 GHz for UMTS is from rainfall attenuation, but even at 2 GHz the required rainfall rate for an attenuation of 0.1dB over 10km is 100mm/h Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

183

Day 3 Section 13 Link Budgets

Terrain Factors As far as link budget calculation is concerned, terrain effects consist of estimating an ‘effective’ lognormal standard deviation to superimpose on a point to area signal level prediction

Cell edges

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

?

In the border area up to three sites can serve an MS via handover, so the effect of the lognormal fading process from each BTS is reduced

184

Day 3 Section 13 Link Budgets

Terrain Factors (cont.) A simulation can be performed for 3 sectored sites, assuming 0.5 correlation factor between sites, a fading correlation distance of 30m and handover time of 0.5s and handover hysteresis of 3 dB. Actual LNF margins are: Coverage [%]

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

σ LNF [dB]

75

85

90

95

98

6

- 3.7

- 1.2

0.5

3.0

5.5

8

- 3.4

- 0.2

1.8

4.9

8.1

10

- 3.1

0.7

3.2

6.8

10.7

12

- 3.1

1.3

4.2

8.4

13.1

14

- 3.2

1.8

5.1

9.9

15.3 185

Day 3 Section 13 Link Budgets

Multipath Loss Transmitted Symbol

Received Symbols

Object around the MS link signal in to the antenna

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Symbol presented to the decoder is smeared, effectively causing loss 186

Day 3 Section 13 Link Budgets

Rician and Rayleigh Fading 0

Typical Urban Power Delay Plot Relative Power (dB)

-5 -10 -15 -20 -25 -30 0

500

1000

1500

2000

2500

Tap Delay (ns)

The fading components can be gathered together as a typical urban (TU) channel model against which decoders can be tested Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

187

Day 3 Section 13 Link Budgets

Rician and Rayleigh Fading (cont.) Fading can be combated using frequency hopping in a GSM system and through the spread spectrum nature of UMTS systems However, due to the fact that the BCCH carrier cannot be frequency hopped, an appropriate margin should be added Simulations of decoder and demodulator designs using TU and other channel models show that a margin of 3 dB should typically be added

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

188

Day 3 Section 13 Link Budgets

Signal Strength

Co-channel Interference Interference approximately constant over service area of site

To counteract the near constant ‘backwash’ of interference from co-channel sites, an ‘interference margin’ of 2 dB has been found to be necessary Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

189

Day 3 Section 13 Link Budgets

Transmission Line Loss On the downlink, aim for a total loss of 3 dB Typical loss values per 100m in the GSM900 band for 7/8”, 1¼” and 1⅝” cables are 3.7, 2.7 and 2.2 dB For UMTS2100, the loss per 100m is 5.7, 4.2, 3.5dB As the feeders themselves are bulky and difficult to manipulate, flexible jumpers are added at BTS and antenna ends. These add a loss of 0.5dB each. Each connector in the chain also adds 0.1 dB loss Use masthead amplifiers to negate uplink feeder losses Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

190

Day 3 Section 13 Link Budgets

Link Budget ‘Power budget’ shows whether the uplink or downlink is weakest. We need path balance, so that the coverage of uplink is equal to the downlink Assume normal case, with TMA, and calculate the link budget for 95% outdoor coverage in an urban area with a single site shadow fading standard deviation of 8 dB and a site height of 30m GBTS

BTS

Duplexer Ldup

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Feeders & Jumpers Lf+j

TMA Ltma

Gdiversity Lpath

GMS

MS 191

Day 3 Section 13 Link Budgets

Link Budget (cont.) Power Budget

MS side

BTS side

Sensitivity dBm

(-104+3+2+5=-94)

(-106+3+2+5=-96)

Antenna RX Gain dB

0

18

Diversity Gain dB

0

4.5

Lf+j dB

(3)

(0)

TX Power dBm

40

30

LNF

(4.9)

(4.9)

Antenna TX Gain dB

18

0

Maximum Pathloss dB

144.1

143.6

Maximum Range (km)

1.94

1.88

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

192

Day 3 Section 14 Frequency Planning

Frequency Division and C/I Planning Principles of Frequency Planning Basic Frequency Reuse Compact Frequency Reuse Frequency Hopping Technology Power Control Discontinuous Transmission

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

193

Day 3 Section 14 Frequency Planning

Frequency Division and C/I Planning The aim of frequency planning is to ensure that the combined interference on the cell edge from surrounding re-use cells is such that the required Carrier to Interference ratio is preserved It is equally important for the point to point or point to area model used to predict accurately at both cell edge and reuse distance Required C/I is different for different services and channels Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

194

Day 3 Section 14 Frequency Planning

Frequency Division and C/I Planning (cont.) For idealised geometries, the cells defining a coverage area can be grouped into ‘reuse clusters’ The number of cells in a reuse cluster is given by n=i²+ij+j², for i,j=0,1,2… Hence possible reuse cluster sizes are 1, 3, 4, 7, 9…

j=1

i=2

If the total number of RF carriers is N, then the number of carriers available in each cell is N/n for a hexagon pattern and N/3n for a cloverleaf pattern Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

195

Day 3 Section 14 Frequency Planning

Frequency Division and C/I Planning (cont.) We can show that the distance at which the frequencies are reused is Dreuse= √(3 N) R where R is the hexagon cell edge length Due to rotational symmetry, six nearest reuse cells interfere for hexagonal reuse For cloverleaf reuse, three of the interfering antennas point away from the cell edge of interest The distance of the cell edge to the serving cell is approximated as R and to each interfering cell as √(3 N)R – R (not really valid for N=1) Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

196

Day 3 Section 14 Frequency Planning

Frequency Division and C/I Planning (cont.) 35 30

C/I Hexagon

25

C/I Cloverleaf

C/I Ratio (dB)

20 15

EFR C/I = 8.7dB

10 5

AMR C/I = 3dB

0 -5 0

5

10

15

20

25

30

-10 -15

Channel Conditions TU3, 1% FER, Frequency Hopping

-20 Reuse Cluster Size

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

197

Day 3 Section 14 Frequency Planning

Basic Frequency Reuse

BCCH group forms an ‘overlay’ with C/I > 10dB, giving high reliability broadcast and control channels, and also serving as handover target for cell-edge MSs

Traffic frequency group forms an underlay with N=4 or 3, with cell edge C/I> 3dB for AMR 4.75 Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

198

Day 3 Section 14 Frequency Planning

Compact Frequency Reuse Hop across far higher number of frequencies (upto and including total operator allocation) than TRXs in cell – RF Frequency Hopping Effective Frequency Load (EFL) = (No of TRXs active) / (Total Frequencies in Hopping Set) EFL, Bit Erasure Rate (BER) and Frame Erasure Rate (FER) rises as network traffic rises Main interest is in 1 site / 1 frequency group per cluster (1/1) and 1 site / 3 frequency groups per cluster (1/3)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

199

Day 3 Section 14 Frequency Planning

Compact Frequency Reuse (cont.) 4

Dropped Call Rate (%)

3.5

Even though the BER distribution is worse in 1/1 than 1/3 due to increased clashes, the better interferer diversity of 1/1 reduces FER so that dropped call rate is equivalent

1/1

3 2.5

1/3

2 1.5 1 0.5 0

0

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

2

4 6 8 Effective Frequency Load (%)

10

200

Day 3 Section 14 Frequency Planning

Compact Frequency Reuse (cont.)

1/1 2/2

3/3

Improve interference distribution by using 2/2 and 3/3 advanced reuse technique. Larger numbers of frequencies are collected per site so that there are a larger number of Mobile Allocation Index Offsets available to mitigate co-channel clashes on the same site Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

201

Day 3 Section 14 Frequency Planning

Although 2/2 compact reuse is superior to 1/1, whether it can be deployed or not depends on whether there are sufficient hopping frequencies available to provide adequate MAIO diversity on an individual site

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Dropped Call Rate (%)

Compact Frequency Reuse (cont.) 4 3.5

1/1 Hopping

3 2.5

18% EFL Gain

2/2 Hopping

2 1.5 1 0.5 0 0

1 2 3 4 5 Effective Frequency Load (%)

6

202

Day 3 Section 14 Frequency Planning

Compact Frequency Reuse (cont.) Advantages: - No or minimal frequency planning used - Performance gains not linked to number of TRXs installed at a site as in basic frequency reuse with baseband frequency hopping - Copes easily with poorly defined best server scenarios and oddly shaped cells Disadvantages: - More complicated to set up per site than basic reuse - Some MS handset types, especially older models, may have problems implementing advanced FH Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

203

Day 3 Section 14 Frequency Planning

Frequency Hopping Technology Baseband Frequency Hopping Hybrid Combiner Loss < 36 dB

Tuned Cavity Loss < 0.5dB

TRX

Call Call

RF Frequency Hopping

TRX

Call

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

TRX

TRX

TRX

TRX

TRX

TRX

Call Call Call

204

Day 3 Section 14 Frequency Planning

Frequency Hopping Technology (cont.) CA: Cell Allocation - Set of frequencies assigned to the cell MA: Mobile Allocation – Subset of cell frequencies assigned to MS, 1≤ MA ≤ 64 HSN: Hopping Sequence Number – pattern of frequency hops performed on 0≤ HSN ≤ 63 (3GPP 45.002) MAIO: Mobile Allocation Index Offset, offset within the HS that ensures no two MSs are co-channel Choose HSN so that adjacent intra- and inter-cell frequency clashes are minimised Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

205

Day 3 Section 14 Frequency Planning

Power Control

MS close to site, downlink power low

By monitoring uplink quality reports, the BTS adjusts power levels to achieve QoS, improving interference for cochannel mobiles User of MS talking, uplink active, downlink inactive due to DTX

MS distant, high power

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

MS in middle of cell, medium power 206

Day 3 Section 14 Frequency Planning

Dropped Call Rate (%)

Power Control (cont.) 4 3.5

54% EFL Gain

RF Hopping + DL Power Control

3 2.5

RF Hopping only

2 1.5 1 0.5 0 0

1

2

3

4

5

6

7

Effective Frequency Load (%) Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

207

Day 3 Section 14 Frequency Planning

Power Control (cont.) Average Power Control gain in terms of C/I improvement is around 1.5 – 2.5 dB at 10% outage level Need fast control algorithm up to 0.48s SACCH reporting interval, RNC handover smoothing of reported RXLEV and RXQUAL no good for fast power control Power steps should be small when decreasing power e.g. 1-2 dB, but should be larger when increasing power, e.g. 3-4 dB Dynamic range for DL PC should be 15-20 dB, larger values have not been found to be effective Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

208

Day 3 Section 14 Frequency Planning

Discontinuous Transmission

Dropped Call Rate (%)

4 3.5 31% EFL Gain

RF Hopping + DL PC + DL DTX

3 2.5

RF Hopping + DL PC

2 1.5 1 0.5 0 0

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

1

2

3 4 5 6 Effective Frequency Load (%)

7

8 209

Day 3 Section 14 Frequency Planning

Discontinuous Transmission (cont.) ‘Voice Activity Factor’ is less than 0.5 in most conversations due to pauses etc. Implied interference reduction of 3 dB is reduced to approximately 2.5 due to SACCH and Noise Description frames that must be transmitted even in silence, however this gain is obtained irrespective of network load or location/distribution of MSs (i.e. no near-far effect) RXQUAL measured over 100 bursts for non-DTX operation and only 12 for DTX, so BER estimates may be statistically worse even though network average C/I improves Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

210

Day 4 Overview

Handover Scenarios Radio Network Problem Pinpointing and Solving UMTS System Design

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

211

Day 4 Section 15 Handover Scenarios

Soft and Softer Handover Hard Handover Inter-Frequency Handover Signalling Flows for Handover from/to UTRAN to/from GSM BSS Impact of Handover on Specific CS Services Impact of Handover on QoS for PS Connections Handover Main Challenges

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

212

Day 4 Section 15 Handover Scenarios

Soft and Softer Handover RBS2

UE Served by RBS2 Call data FI

FI

UE Served by RBS1 and RBS2

Call data

UE Served by RBS1

RBS1

Signal Strength

RNC

‘Soft Handover’ Region, UE served by both RBS1 and RBS2

Drop threshold Add threshold

RBS1 removed from ‘active set’

RBS2 added to ‘active set’ UE starts monitoring RBS2

Time

UE stops monitoring RBS1

The RNC sends call data to both RBSs softening the link on FI, on the same UMTS frequency Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

213

Day 4 Section 15 Handover Scenarios

Soft and Softer Handover (cont.) FI

Scrambling Code 1

Channelisation Code 1

Scrambling Code 2

FI

Channelisation Code 2

Despread data synchronised by RNC within 1 symbol

In soft handover, the RNC sends duplicate data to 2 or more RBSs. The UE performs vector addition of the synchronised data, and the RNC selects uplink RLC frames based on quality. Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

214

Day 4 Section 15 Handover Scenarios

Soft and Softer Handover (cont.) Soft Handover advantages: Rayleigh and shadow fading peaks have potential seriously to disrupt both link directions by causing excessive interference; soft handover avoids the very fast signalling that would be required for hard handover Soft Handover disadvantages: Resources duplicated in RBS (channel elements required to support one or more channelisation codes per transport channel), in RNC processing power and transmission links, extra downlink interference causing ‘noise rise’ Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

215

Day 4 Section 15 Handover Scenarios

Soft and Softer Handover (cont.) ‘Softer’ handover takes place between sectors on an RBS Uplink power received on the antennas of each sector is combined in NodeB ‘rake’ receiver RNC sends only one data stream rather than duplicate data stream Soft and Softer handover can occur in any combination Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

216

Day 4 Section 15 Handover Scenarios

Hard Handover Channel resources changed from one cell to another No independent fading process gain on downlink

2

Uplink Performance 1.5 1

3

-8

-6

-4

-2

-0.5 Pathloss Difference between RBSs (dB)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

0

Downlink Performance

2 1

0 -10 -1

0.5 0 -10

Soft Handover Gain vs Hard Handover (dB)

Soft Handover Gain vs Hard Handover (dB)

No macro diversity gain on uplink

-2 -3

-8

-6

-4

-2

0

Downlink SHO gain outperforms uplink due to lack of antenna diversity at UE Pathloss Difference between RBSs (dB)

217

Day 4 Section 15 Handover Scenarios

Inter-Frequency Handover FII

FI

Scenario 1: UMTS to UMTS handover e.g. for capacity reasons on same site, or at RNC/3G-MSC/Iur boundary between sites

RLC slots

FI

Scenario 2: UMTS to GSM handover e.g. for service management reasons on the same site, or between UMTS and GSM sites at 3G boundary

UE creates gap in some timeslots

Power Time

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

FA

UMTS interfrequency measurements, GSM BCCH measurements

Lock to FII scrambling code handover under RNC command Decode at least one GSM BSIC, handover from RNC to GSM BSC

218

Day 4 Section 15 Handover Scenarios

Inter-Frequency Handover (cont.) Soft Handover requires functioning Iur interface; if this is impaired then (hard) interfrequency handover is required IFHO may be used to manage traffic between two layers on the same site if operator is licensed for more than one 3G frequency allocation IFHO and Inter-System Handover to GSM necessary at 3G ‘dead spots’ within network and hand down to 2G GSM at 3G buildout boundary ‘Compressed Mode’ allows inter-frequency/system measurements at the expense of raised interference Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

219

Day 4 Section 15 Handover Scenarios

UTRAN ↔ GSM BSS Signalling Flows for Handover UE

RBS

RNC

3G MSC

Measurement Control: CPICH RSCP events 1e, 1f Measurement Control: CPICH Ec/Io events 1e, 1f Measurement Control: CPICH Ec/Io events 1e, 1f Measurement Report, e.g CPICH Ec/Io event 1f

Decision to Initiate ISHO Attempt

Radio Link Reconfiguration Prepare Radio Link Reconfiguration Ready Radio Link Reconfiguration Commit Physical Channel Reconfiguration Physical Channel Reconfiguration Complete

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

220

Day 4 Section 15 Handover Scenarios

UTRAN ↔ GSM BSS Signalling Flows for Handover (cont.) UE

RBS

Measurement Report

RNC

3G MSC

RSSI Measurements

Measurement Report Compressed Mode Command Measurement Control Measurement Report

Decision to Complete ISHO

Measurement Report Retask compressed mode with decoding of BSIC for best received RSSI

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Return successfully decoded BSIC for highest ranked ARFCN by RSSI

221

Day 4 Section 15 Handover Scenarios

UTRAN ↔ GSM BSS Signalling Flows for Handover (cont.) UE

RNC

3G MSC

2G MSC

BSC

Relocation Required Prepare Handover Request Handover Request Handover Request Acknowledge Prepare Handover Response Relocation Command Handover from UTRAN Command Handover Access (on Um/GSM Air Interface) Process Access Signalling Request Handover Detect Handover Complete (on Um/GSM Air Interface)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

222

Day 4 Section 15 Handover Scenarios

UTRAN ↔ GSM BSS Signalling Flows for Handover (cont.) UE

RNC

3G MSC

2G MSC

BSC

Handover Complete Send End Signal Request Iu Release Command Iu Release Complete Send End Signal Response

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

223

Day 4 Section 15 Handover Scenarios

Impact of Handover on CS Services Fading Process from RBS1

Required Eb/No = 11dB

Fading Process from RBS2

Required Eb/No = 7.7dB (Voice, ITU Pedestrian A, 3km/h) Combined Fading Process

At the link level, handover reduces the required Eb/No for voice, video and CS data services due to fading diversity in the demodulated vector components after the ‘rake receiver Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

224

Day 4 Section 15 Handover Scenarios

Impact of Handover on CS Services (cont.) Normal Soft Handover

Excessive Soft Handover Two way SHO

Three way SHO

At the network level, the lack of buffering due to the real-time nature of CS services require soft handover region overlap but where this is excessive the result is loss of capacity Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

225

Day 4 Section 15 Handover Scenarios

Impact of Handover on CS Services (cont.) Voice: SHO: No delay/interruption, data synchronous over Uu ISHO: delay/interruption under ISHO dependent on speed of response from GSM BSS to UE to get channel physical information for timing advance. NO SYNCHRONOUS HANDOVER specified as GSM frame numbers are not relevant to UE before handover attempt Video: SHO: As voice, no interruption but second order effects from SHO radio link addition/removal Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

226

Day 4 Section 15 Handover Scenarios

Impact of Handover on QoS for PS connections Time=t Time=t+1

RNC PDP Context

(MAC)

Time=t+2

Handover is specified for R99 PS services but is ‘expensive’ in terms of RAN resources, i.e. SF=4 for 384 kb/s FTP service. End-to-end error correction for NRT services operating below the IP layer helps throughput more than handover Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

227

Day 4 Section 15 Handover Scenarios

Impact of Handover on QoS for PS connections (cont.) 300kb/s

Instantaneous Throughput

Session Throughput Hand down to 2G, PDP session stalls

PDP Context relocation to 2G

Session resumes on 2G GPRS

R99 data PDP contexts can hand down to 2G but if care is not taken with NRT parameters the session can stall resulting in low session throughput. Experience has shown that it is better to use 3G-2G handover parameters to prolong 3G session as long as possible. Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

228

Day 4 Section 15 Handover Scenarios

Impact of Handover on QoS for PS connections (cont.) Time=t

Time=t+1

RNC PDP Context Time=t+2

(MAC-d)

MAC-hs

No handover on HSPA channels (HS-DSCH or HS-SCCH but new MAC-hs protocol between UE and RBS to ensure very fast retransmission, with ‘soft combining’ of mac-hs frames at the UE

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

229

Day 4 Section 15 Handover Scenarios

Handover Main Challenges 3G-3G Link Layer: Downlink Power Drift

UE sends downlink fast power control bits Each RBS softening the link experiences different receive errors for the FPC bits As a consequence the power levels for each downlink drift apart – RNC needs to intervene to set a ‘reference’ power level for each downlink Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

230

Day 4 Section 15 Handover Scenarios

Handover Main Challenges (cont.) 3G-3G Link Layer: Uplink Power Control Detection Errors

Power Down Power Up Power Up

Each RBS sends ‘power up’ or ‘power down’ commands depending on the local characteristics of uplink fading

Uplink power control signals are individual to each RBS and do not benefit from MRC as do the data bits Need extra downlink DPCCH power or extra UPC bits per RLC frame – wasteful of power and/or throughput Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

231

Day 4 Section 15 Handover Scenarios

Handover Main Challenges (cont.)

Measurement Control Message

3G-3G Network Layer: 3G-3G and 3G-2G Neighbour Definition Measurement Control: SC1 SC2 SC3 … 3G-3G Neighbour list

ARFCN1 BSIC1 ARFCN2 BSIC2 ARFCN3 BSIC3 … 3G-2G Neighbour list

One of the most important optimisation tasks is 3G-3G and 3G-2G neighbour definition. This will usually be different from the default set of neighbours generated by the planning tool, due to local propagation effects that cannot be modelled. Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

232

Day 4 Section 15 Handover Scenarios

Handover Main Challenges (cont.) 3G-2G Hand-down: Need to set thresholds for 3G Received Signal Code Power (RSCP) and Energy per Chip relative to interference (Ec/Io) so that CS voice calls hand down to 2G quickly at limit of 3G coverage However, need to set NRT threshold so that UE tries to ‘hang on’ to 3G coverage (albeit at bad quality) to stop session stalling and low throughput on handover to GPRS Need separate RT and NRT 3G-2G handover parameters – tuning of these is not generally an optimisation function but has a key impact on network performance Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

233

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Obtaining Basic Information Coverage Capacity Interference Handover Call Drop

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

234

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Obtaining Basic Information UMTS/ UMTS/ UMTS GSM UMTS UMTS GSM Antenna Antenna Antenna Antenna Antenna

GPS Antenna

3G

3G/2G

PS

CS

GPS USB USB

Standard measurement software run on data gathering PC is e.g. TEMS Investigation etc

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

USB

Dual Band Scanner

235

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Obtaining Basic Information (cont.) Laptop – runs measurement software to gather and collate data from the UEs, GPS and scanner GPS – records position information for signal level measurements and events 3G UE – runs short or long Mobile Originated (MO) calls to network test number to assess 3G only quality 3G/2G UE – runs short or long calls to assess hand down (and optionally up) between 3G and 2G network layers PS/CS UEs – optional PS and CS MO data calls, conventionally FTP GETs and CS64 video calls Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

236

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Obtaining Basic Information (cont.) For each area to be investigated, define drive route and check for one-way streets, traffic restrictions etc First drive with scanner only, to verify route and assess basic performance Second drive with 3G and 3G/2G UEs in either short calls to assess call setup and drop reliability on 3G, or long calls to check retainability and neighbour definitions 3G to 3G and 3G to 2G Final drive adds FTP download and CS video call when all outstanding neigbours and site reliability issues resolved Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

237

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Coverage Two basic metrics are Received Signal Code Power (RSCP) and Energy per Chip versus Interference (Ec/Io) RSCP measures ability of the UE to detect a signal. It can be assessed using a UE in scan mode, but better dynamic range when using a dedicated scanner Gather statistics on overall number of signal samples exceeding certain thresholds, e.g. Urban DL Coverage

Suburb DL Coverage

OTSR SU DL Coverage

RSCP >=-86dBm (%)

RSCP >=-94dBm (%)

RSCP >=-99dBm (%)

47.8

68.1

79.2

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

238

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Coverage (cont.)

3G Scanner RSCP Coverage Problems

>=-55dBm >=-87dBm >=-94dBm >=-99dBm >=-107dBm =-86dBm)

Suburb DL Quality (RSCP >=-94dBm)

Suburb DL Quality (RSCP >=-99dBm)

Ec/Io >=-9dB (%)

Ec/Io >=-11dB (%)

Ec/Io >=-9dB (%)

Ec/Io >=-11dB (%)

Ec/Io >=-9dB (%)

Ec/Io >=-11dB (%)

99.9

100.0

99.5

100.0

97.5

99.7

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

240

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Coverage (cont.)

3G Scanner Ec/Io Coverage Problems

>=-4dB >=-6dB >=-8dB >=-11dB =-4dB >=-6dB >=-8dB >=-11dB 1 server (%) 27.8

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

SHO >2 servers (%) 8.7 243

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Capacity (cont.)

Estimated No. of SCs in AS (scanner)

=1 =2 =3 =4 >=5

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

244

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Interference When the active set is full, no more sites can be added in soft handover If the number of clearly receivable pilots exceeds the maximum AS size, usually 3, in any measurement area then this is deemed to be interference Set a value for the maximum percentage of signal samples where AS+1 or more signals fall within a defined power window relative to the stongest, e.g 95%/7 dB =5

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

246

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Handover Identify missing 3G-3G and 3G-2G neighbours from geographically binned scanner data Where pairs of SCs or a SC and GSM ARFCN are detected in a bin, create a paired relationship if none already exists and increment the ‘discovered’ value in the bin For each SC, order the relationships by total number of ‘simultaneously seen’ samples of other SCs (3G-3G) and ARFCNs (3G-2G) Select the top n and m neighbours, where n is the maximum allowed 3G-3G and m the maximum 3G-2G Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

247

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Handover (cont.)

Drive Route

Terrain bins, e.g. 100m x 100m Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Source 10520 10520 10520 10521 10521 10521 10521 10521 10521 10521 10521 10521 10521 10521 10526 10529 10529 10529

Target Samples Distance 17026 45 2.6356 1523 239 5.27237 1524 341 1.36265 20380 44 6.43994 10529 54 7.17444 2158 65 3.58593 20362 107 5.64992 1524 143 6.28139 17026 243 4.32703 1523 350 2.61723 324 530 3.05871 5440 860 3.14835 1304 2468 1.34093 1520 4372 1.27981 1524 30 6.18588 1303 34 4.97901 10521 54 7.17444 5240 61 1.54247

Subset for max 3G-3G neighbours = 8 248

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Call Drop Call setups

Call drops

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

249

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Call Drop (cont.) Call completion ratio is a key optimisation metric Successful Call Setups Call Setup Success Rate = Total Call Attempts

Successful Call Setups − Dropped Calls Call Completion Rate = Successful Call Attempts Successful Call Setups − Dropped Calls Overall Call Completion Rate = Total Call Attempts Call Statistics (2min call) Call Attempts

CSSR (%)

Setup failures

CCR (%)

Call Drops

OCCR (%)

120

90.8

11

92.7

8

84.2

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

250

Day 4 Section 16 Pinpointing and Solving Radio Network Problems

Call Drop (cont.) A key skill in 3G optimisation is inspection of L3 messages UL_DCCH_Message - IntegrityCheckInfo - IntegrityCheckInfo_messageAuthenticationCode: 0011 0101 1101 1000 0100 1001 0001 0100 , Uu_RRC_RRC_MessageSequenceNumber: 2 - UL_DCCH_MessageType - MeasurementReport, Uu_RRC_MeasurementIdentity: 1 MeasuredResults CellMeasuredResults CellSynchronisationInfo CountC_SFN_Frame_difference, Uu_RRC_CountC_SFN_Frame_difference__countC_SFN_High: 0, Uu_RRC_CountC_SFN_Frame_difference__off: 3, Uu_RRC__choice96_Uu_RRC__seq263__tm: 3580 PrimaryCPICH_Info, Uu_RRC_PrimaryScramblingCode: 320, Uu_RRC_CPICH_Ec_N0: 38 CellMeasuredResults CellSynchronisationInfo CountC_SFN_Frame_difference, Uu_RRC_CountC_SFN_Frame_difference__countC_SFN_High: 12, Uu_RRC_CountC_SFN_Frame_difference__off: 251, Uu_RRC__choice96_Uu_RRC__seq263__tm: 2064 PrimaryCPICH_Info, Uu_RRC_PrimaryScramblingCode: 205, Uu_RRC_CPICH_Ec_N0: 10 EventResults IntraFreqEventResults, Uu_RRC_EventIDIntraFreq: RRC_e1b The UE requests removal CellMeasurementEventResults of SC 205 from AS PrimaryCPICH_Info, Uu_RRC_PrimaryScramblingCode: 205

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

251

Day 4 Section 17 UMTS System Design

Network Design Principles RF Coverage Analysis RF Capacity Analysis Calculating Uplink Cell Load Downlink Cell Load Load Sharing Radio Access Network

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

252

Day 4 Section 17 UMTS System Design

Network Design Principles Who are the subscribers? What are they doing and when? Where are they relative to the network coverage? How many subscribers are there in each forecast year?

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

253

Day 4 Section 17 UMTS System Design

Network Design Principles (cont.) Year on Year Growth

CS 12.2 kbps

CS 12.2 kbps

TYPE A

CS 64kbps

CS 64 kbps

0.21

0.34

0.49

0.0370

0.0597

0.0875

TYPE C

PS 384 kbps (PS 128kbps) PS 128kbps (PS 128kbps) PS 1.2 Mbps (PS 500kbps) PS 10 Mbps (PS 2.5 Mbps)

PS 64 kbps (PS 64kbps) PS 32 kbps (PS 32kbps) PS 384 kbps (PS 64kbps) PS 1.2 Mbps (PS 500 kbps)

0.55

0.90

1.31

0.0063

0.0102

0.0149

0.42

0.67

0.98

0.0047

0.0076

0.0112

0.14

0.22

0.33

0.0016

0.0025

0.0037

0.07

0.11

0.16

0.0008

0.0013

0.0019

Voice TYPE A

CS 12.2 kbps CS 64kbps

CS 12.2 kbps CS 64 kbps

550 0.33

620 0.44

751 0.64

30.5556 0.0587

34.4320 0.0781

41.7289 0.1143

TYPE C

PS 384 kbps (PS 128kbps) PS 128kbps (PS 128kbps) PS 1.2 Mbps (PS 500kbps)

PS 64 kbps (PS 64kbps) PS 32 kbps (PS 32kbps) PS 384 kbps (PS 64kbps)

0.41

0.55

0.80

0.0047

0.0062

0.0091

0.50

0.66

0.96

0.0056

0.0075

0.0110

0.33

0.44

0.64

0.0038

0.0050

0.0073

PS 10 Mbps (PS 2.5 Mbps)

PS 1.2 Mbps (PS 500 kbps)

0.08

0.11

0.16

0.0009

0.0012

0.0018

# of 3G Subscribers

08-09

Business User

Traffic Forecast in BH (Data: kbps) (Voice and Video: mErl)

Peak UL rate (across 90% of cell area)

Voice

TYPE B TYPE D TYPE E

HVC

3G Subscriber Traffic Forecast (Data: MB/month/user) (Voice: minutes/month/user)

Peak DL rate (across 90% of cell area)

Service Category

TYPE B TYPE D TYPE E

Who the subscribers are Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

4,299

6,455

12-13

20,503

30,778

16-17

37,390

56,164

08-09

12-13

16-17

08-09

12-13

16-17

230

259

314

12.7778

14.3988

17.4502

What the subscribers are doing

When (e.g. busy hour) 254

Day 4 Section 17 UMTS System Design

Network Design Principles (cont.) Service Category

Peak DL rate (across 90% of cell area)

Peak UL rate (across 90% of cell area)

# of 3G Subscribers

08-09

YAF

Voice TYPE A TYPE C

08-09

12-13

16-17

147 0.15 0.08

6.0000 0.0133 0.0005

6.7612 0.0178 0.0006

8.1940 0.0260 0.0010

0.10

0.13

0.19

0.0011

0.0015

0.0021

0.00

0.00

0.00

0.0000

0.0000

0.0000

0.00

0.00

0.00

0.0000

0.0000

0.0000

CS 12.2 kbps CS 64 kbps

100 0.08

113 0.11

137 0.16

5.5556 0.0147

6.2604 0.0195

7.5871 0.0286

PS 384 kbps (PS 128kbps) PS 128kbps (PS 128kbps) PS 1.2 Mbps (PS 500kbps) PS 10 Mbps (PS 2.5 Mbps)

PS 64 kbps (PS 64kbps) PS 32 kbps (PS 32kbps) PS 384 kbps (PS 64kbps) PS 1.2 Mbps (PS 500 kbps)

0.02

0.03

0.05

0.0003

0.0004

0.0005

0.06

0.08

0.11

0.0007

0.0009

0.0013

0.00

0.00

0.00

0.0000

0.0000

0.0000

0.00

0.00

0.00

0.0000

0.0000

0.0000

PS 1.2 Mbps (PS 500kbps)

PS 384 kbps (PS 64kbps)

1,000

2,500

3,000

11.3778

28.4444

34.1333

TYPE C

TYPE E

Other Subs

16-17

122 0.10 0.06

CS 12.2 kbps CS 64kbps

TYPE D

TYPE B TYPE D TYPE E

DATAC

12-13

Voice TYPE A

TYPE B

TYPE D

Traffic Forecast in BH (Data: kbps) (Voice and Video: mErl)

108 0.08 0.04

CS 12.2 kbps CS 64 kbps PS 64 kbps (PS 64kbps) PS 32 kbps (PS 32kbps) PS 384 kbps (PS 64kbps) PS 1.2 Mbps (PS 500 kbps)

18,975

4,771

8,282

129,617

54,769

41,411

16-17

3G Subscriber Traffic Forecast (Data: MB/month/user) (Voice: minutes/month/user)

08-09

CS 12.2 kbps CS 64kbps PS 384 kbps (PS 128kbps) PS 128kbps (PS 128kbps) PS 1.2 Mbps (PS 500kbps) PS 10 Mbps (PS 2.5 Mbps)

12-13

Busy hour traffic = Monthly Traffic x (0.1/30 days) x (1000 mErl/60 mins)

288,422

142,428

74,540

Remaining user categories Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

255

Day 4 Section 17 UMTS System Design

Network Design Principles (cont.)

Business High Value Customer (HVC) Young (YAF) Other Datacard (data only) Total

Urban 429.9

08-09 Sub urban 343.92

Rural 85.98

Total 4299

Dense Urban 16402.4

4518.5 1291 7590 4743.75 1669.85 1431.3 4969.2 2484.6 22186.75 10380.55

516.4 3795 954.2 662.56 6272.08

129.1 2846.25 715.65 165.64 3942.62

6455 18975 4771 8282 42782

21544.6 51846.8 19169.15 24846.6 133809.55

Dense Urban 3439.2

Where the subscribers are

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Business High Value Customer (HVC) Young (YAF) Other Datacard (data only) Total

Dense Urban 29912 39314.8 115368.8 49849.8 44724 279169.4

12-13 Sub urban Urban 2050.3 1640.24 6155.6 32404.25 16430.7 12423.3 69464.15

2462.24 25923.4 10953.8 3312.88 44292.56

Rural 410.06

Total 20503

615.56 19442.55 8215.35 828.22 29511.74

30778 129617 54769 41411 277078

Urban 3739

16-17 Sub urban 2991.2

Rural 747.8

Total 37390

11232.8 72105.5 42728.4 22362 152167.7

4493.12 57684.4 28485.6 5963.2 99617.52

1123.28 43263.3 21364.2 1490.8 67989.38

56164 288422 142428 74540 598944

256

Day 4 Section 17 UMTS System Design

RF Coverage Analysis Coverage threshold varies from service to service due to different Eb/No requirements Coverage is designed for site overlap at a particular service Whether overlap is actually achieved depends on whether only the 2G site layout is reused or new 3G sites are built

Coverage zone Detection zone Interference zone

If the wrong reference service is chosen, the site ‘raster’ will be too dense, causing too much overlap of the detection and interference zones and loss of capacity Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

257

Day 4 Section 17 UMTS System Design

RF Coverage Analysis (cont.) Low load scenario – coverage boundary nearly equal to service planning boundary

Loaded scenario – increased interference and shortage of DCH power shrinks coverage area – ‘cell breathing’

UE now outside loaded coverage area

Unloaded radius

Loaded radius

Required Eb/Io

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

258

Day 4 Section 17 UMTS System Design

RF Coverage Analysis (cont.) ‘Cell Breathing’ dominates at high system loads When the system is lightly loaded the transmit power capability of the UE at cell edge dominates, i.e. uplink limited When the system is heavily loaded diminishing downlink DCH power available to serve UEs suffering heavy interference dominates, i.e. downlink limited Hence the RF coverage analysis must commence for each year scenario, i.e. 08-09 and 16-17 will have different cell thresholds, therefore different total numbers of sites Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

259

Day 4 Section 17 UMTS System Design

RF Capacity Analysis UMTS capacity is not static as in the 2G case. Whether a call can be added, and whether it will complete successfully, depends on the interference level As different sessions are added in the ‘call mix’ each will have its own Eb/Io and distance v. power characteristic There is no closed-form solution to calculate the capacity, so the overall system capacity must be estimated as the mean of a normal distribution of call scenarios Each call and session mix scenario created via simulation is called a ‘snapshot’ Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

260

Day 4 Section 17 UMTS System Design

RF Capacity Analysis (cont.) voice video data

Admission limit, e.g. system 3dB noise rise

HSDPA

In each simulation snapshot voice, video, data, HSDPA and other sessions are added up to the admission control limit for the network. This is usually set at the overall 3dB noise rise, or site power/channel elements/etc limits, whichever is reached first. After this no more sessions can be added and the snapshot is stored Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

261

Day 4 Section 17 UMTS System Design

RF Capacity Analysis (cont.) HSDPA sessions are rate adaptive to the channel conditions

16_QUAM_5_74

The call closer to the server experiences optimum channel conditions and is allocated 16_QUAM_5_74 The call farthest from the server experiences poor channel conditions and is allocated QPSK_1_38

QPSK_1_38

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Hence sessions allocated lower throughput speeds ‘persist’ for longer and show up disproportionately in simulation snapshots 262

Day 4 Section 17 UMTS System Design

Uplink Cell Load Number of active users in cell

N

1 ηUL = ∑ (1 + i ) W j =1 1+ ( Eb / No) j ⋅ Rj ⋅ vj System Load Factor. As this approaches 1 the system is said to be approaching ‘pole capacity’

‘Other to Own Cell’ interference System chip rate, for UMTS = 3.84 Mc/s

Activity factor = 0.4-0.7 for voice services, 1.0 for data Bit energy to noise requirement for jth user

Bit rate of jth user

Uplink Interference Margin = -10 log (1-ηUL) Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

263

Day 4 Section 17 UMTS System Design

Uplink Cell Load (cont.) 12

Interference Margin (dB)

10 8

i=0.6 i=0.7 i=0.9 i=1.1

Capacity gain at 6dB ‘noise rise’

6 Capacity gain at 3dB ‘noise rise’ 4 2

500 UL Throughput (kb/s) Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

1000 264

Day 4 Section 17 UMTS System Design

Uplink Cell Load (cont.) ‘Other cell to own cell’ interference i is the ratio of the interfering power received from all UEs connected to the cell of interest relative to the total noise power from the cell’s nearest neighbours, second nearest neighbours etc It can be seen that this has a direct influence on the total cell, and therefore system, capacity Reduction of the ‘other to own cell’ interference ratio is one of the key activities of RAN planning, through choice of sites that are otherwise shielded from one another, and optimisation where we downtilt/change antenna directions etc to reduce overspill and therefore i Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

265

Day 4 Section 17 UMTS System Design

Downlink Cell Load Activity factor = 0.4-0.7 for voice services, 1.0 for data N

∑

(Eb

N0 ) j

[(

Bit energy to noise requirement for jth user

) ]

η DL = v j 1 − α j + ij ‘Other to Own Cell’ Downlink Load W Rj interference at j =1 Factor. As with location of jth user System (Uplink) load factor this System chip rate, for Bit rate of jth user Orthogonality factor for jth UMTS = 3.84 Mc/s should be well user, varies from < 0.3 for below 1 for dense urban area to > 0.7 for open area realistic noise rise on the downlink

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

266

Day 4 Section 17 UMTS System Design

Downlink Cell Load (cont.) On the downlink the users and nearly all common channels are separated by orthogonal ‘channelisation’ codes which are multiplied into the base site scrambling code Over an ideal free space path the orthogonal channels would be perfectly separable, but scattering and multipath reduce the orthogonality In an open or rural area with little multipath the orthogonality is very good, with αj approaching 1. In rich multipath environments αj approaches 0 and the load equation reverts to non-orthogonal form as for the uplink Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

267

Day 4 Section 17 UMTS System Design

Downlink Cell Load (cont.) The downlink load factor can also be used to simulate the required RBS wideband PA power N

N rf L ∑ v j PRBS =

j =1

(Eb

N0 )j

W Rj

1 − η DL

where L is the average path loss between UE and RBS and Nrf is the noise spectral density in Watts/Hertz Obviously the snapshot scenario halts when either uplink admission control or RBS power allocation fails Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

268

Day 4 Section 17 UMTS System Design

Load Sharing One option is to redirect suitable traffic from the UMTS network to the 2G GSM network. Suitable load sharing traffic is voice, low bitrate traffic and requested high bitrate traffic which is simulated with a very poor throughput due to repeated retries Improvements in noise rise feed directly to capacity gains, and voice users may be more satisfied on the more mature and better optimised 2G network Voice users are routinely handed down to 2G in UMTS networks today, but in the long term spectrum refarming may have an impact on this practice Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

269

Day 4 Section 17 UMTS System Design

Radio Access Network When further load sharing is no longer possible, the RAN must be upgraded Step 1 – enhanced sectorisation e.g. 3→4, 5 or 6 sector sites. Each extra sector adds available downlink power and if combined with narrowing of the HPBW of the sector antennas reduces the received uplink interference Step 2 – 3G only site buildout; when the existing 2G network is no longer sufficient for the offered traffic then extra UMTS only or 3G/2G sites must be planned Step 3 – some operators intend to introduce ‘femtocells’ Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

270

Day 4 Section 17 UMTS System Design

Radio Access Network (cont.)

3→6 sectors

Interference collected / power radiated over effectively 120°

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Interference collected / power radiated over effectively 60°

271

Day 4 Section 17 UMTS System Design

Radio Access Network (cont.)

Traffic growth

New 3G sites to counteract coverage lost to ‘cell breathing’ Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

272

Day 4 Section 17 UMTS System Design

Radio Access Network (cont.) Base site switches to high power to overcome building penetration loss

Interior of building served by femtocell does not require resources from main site

ADSL or fibre

Femtocells increase network capacity by removing indoor penetration loss overhead from the main RBS sites serving a region Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

273

Day 5 Overview

3G System Design Considerations ITU-R Propagation Models and Prediction Methods Key Performance Indicators

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

274

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures Cell Site Design Search Area Site Qualification Site Acceptance Site Rejection EMF Compliance

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

275

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures Wireless System Procedures Area to be served is divided into cell service areas appropriate to the clutter type, e.g. dense urban, urban, suburban, rural etc Traffic hotspots that are inconsistent with clutter type also lead to ‘densification’ of site raster Added complication in 3G is that cell boundaries are not unique… Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

276

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures (cont.)

Average Path Loss dB

3G RF Design Considerations

Downlink Uplink

1

2

Capacity

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Need to choose coveragecapacity operating point depending on intent of the network If high coverage with low to moderate capacity, operate at position 1 If priority is high capacity, download/streaming, operate at position 2

277

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures (cont.) Methodology – ‘power budget’ for UL and DL Choose system coverage-capacity e.g. 6 dB noise rise Choose reference service, e.g. voice, Eb/No=5dB/8dB Parameter

Uplink

Downlink

Thermal Noise Receiver Noise Figure =Noise Power at Receiver Interference Margin/Noise Rise =Total Noise Power at Receiver Processing Gain Required Eb/No

-108.15 dBm 4 dB -104.15 dBm 6dB -98.15 dBm 24.08 dB 5dB

-108.15 dBm 9 dB -99.15 dBm 6dB -93.15 dB 24.08 dB 8dB

Receiver Sensitivity

-117.23 dBm

-109.23 dBm

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

278

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures (cont.) Methodology – ‘power budget’ for UL and DL (cont.) Parameter Receiver Sensitivity Receiver Antenna Gain Cable Loss Body Loss Low Noise Amplifier Gain Soft Handover Diversity Gain Power Control Headroom Shadow Fading Margin Required Signal Level Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Uplink

Downlink

-117.23 dBm

-109.23 dBm

18 dBi 2.5 dB 0 dB 4 dB 1.5 dB 2 dB 8 dB

0 dBi 0 dB 5 dB 0 dB 3 dB 2 dB 8 dB

-128.23 dBm

-97.23 dBm 279

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures (cont.) Methodology – ‘power budget’ for UL and DL (cont.) Parameter

Uplink

Downlink

-128.23 dBm

-97.23 dBm

21 dBm

33 dBm

Body Loss

5 dB

0 dB

Cable Loss

0 dB

2.5 dB

Transmit Antenna Gain

0 dBi

18 dBi

16 dBm

48.5 dB

-144.23 dBm

-145.83 dBm

Required Signal Level Transmit Power per DCH

=EIRP Maximum Propagation Loss

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

280

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures (cont.) Propagation Models – Free Space Model Pathloss = 32.4 + 20log(d) + 20*log(f) For f in MHz and d in km

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

281

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures (cont.) Propagation Models – Hata Model Hata used data from Okumura, which was valid up to 1920 MHz However, Hata optimised the resolution of his models for the frequency range 150 MHz -1500 MHz The Hata formula has three ‘native’ forms, for urban, suburban and ‘open’ areas An extension of the Hata formula up to 2 GHz is available, and is named COST 231 Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

282

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures (cont.) Propagation Models – Hata Model (cont.) For urban areas:

Urban Pathloss = 69.55 + 26.16 log(f) – 13.82 log(hRBS) + ( 44.9 – 6.55 log(hRBS)) log(d) – a(hUE) With UE height correction factor for small and medium sized cities

a(hUE) = ( 1.1 log(f) – 0.7 ) hUE – ( 1.56 log(f) – 0.8 ) And for large cities

a(hUE) = 8.29 log( 1.54 hUE )² – 1.1 for f ≤ 200 MHz 3.2 log( 11.75 hUE )² – 4.97 for f ≤ 200 MHz The range of validity is: 150 MHz < f < 1500 MHz, 30 m < hRBS < 200 m 1 km < d < 20 km and 1 m < hRBS < 10 m Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

283

Day 5 Section 18 3G System Design Considerations

RF System Design Procedures (cont.) Propagation Models – Hata Model (cont.) For suburban areas:

Suburban Pathloss = Urban Pathloss – 4.78 log(f)² + 18.33 log(f) – 40.94 For open areas:

Open Area Pathloss = Urban Pathloss – 2 log(f/28)² – 5.4 COST231 extension for 1500 MHz < f < 2000 MHz:

COST231 Pathloss = 46.3 + 33.9 log(f) – 13.82 log(hUE) – a(hUE) + (44.9 – 6.55 log(hUE)) log(d) + C Where C = 0 dB for medium cities and suburban areas with medium tree density and C = 3 dB for urban centres Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

284

Day 5 Section 18 3G System Design Considerations

Cell Site Design 3G sites ‘inherit’ their positioning and sector orientation from 2G GSM900 and GSM1800 colocated sites

Irregular site orientations can still be used, provided the inter-site distance is adjusted depending on whether the sectors are ‘opposed’ or ‘interleaved’

Maximum opposed intersite distance

Maximum interleaved intersite distance

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

285

Day 5 Section 18 3G System Design Considerations

Search Area When the ‘ideal’ grid is superimposed on virgin area or interspersed with the existing 2G site raster the planned locations may not be possible or practical By moving to less well fitting locations within a ‘search radius’ it may be possible to build the site Values of search radius between 200m and 500m are possible for UMTS, depending on local clutter

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

286

Day 5 Section 18 3G System Design Considerations

Site Qualification Is the site within the search radius? If not, are there exceptional circumstances, such as only suitable building/tower/object in the nominal site area? If on a building roof, is there sufficient space to mount the antennas and is there a pre-existing equipment room or roofspace outdoors for a rack solution? Are there local planning constraints and if so, can an ‘invisible’ be constructed? Is the site owner positive? Does sufficient power exist at the site or if not, can this be upgraded? Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

287

Day 5 Section 18 3G System Design Considerations

Site Acceptance Approval by radio planner during a site visit, after soft ‘soft’ credentials have been checked by Acquisition α γ

β α+β+γ < 180 °

Antenna blocking – in order for a site to be accepted, the total blocking angle α+β+γ should be less than 180°and no single blockage should exceed 60° Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

288

Day 5 Section 18 3G System Design Considerations

Site Acceptance (cont.) The siting of the antennas must permit for sufficient vertical downtilt, either mechanical or electrical, to permit coverage optimisation

Boresight Horizontal distance from roof edge to antenna (x) 5m 10m 15m 20m 25m 30m

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Min. height of bottom of antenna above rooftop for rural and suburban sites (y) 1.5m 3.0m 4.4m 5.9m 7.4m 8.9m

y

x

Min. height of bottom of antenna above rooftop for dense urban sites (y) 2.3m 4.6m 6.8m 9.1m 11.4m 13.7m

289

Day 5 Section 18 3G System Design Considerations

Site Acceptance (cont.)

Stub masts on sites can be employed to raise the antennas to the required height above average clutter ‘Street Furniture’ solutions at or just above the clutter will have poor coverage Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

30 Average Clutter Height = 12m Height of antenna midpoint over average clutter (m)

‘Average Antenna Height’ is important to contain interference while still yielding the required coverage

25 20

Average Clutter Height = 15m Average Clutter Height = 20m

15 10

Above average clutter Target antenna height 3-10m

5 Average clutter height

0 -5 -10 -15

0

Target Cell Range Below average clutter 1000 500

1500

2000

2500

3000

3500

Coverage Distance (m)

290

Day 5 Section 18 3G System Design Considerations

Site Rejection Candidate sites can be rejected on a number of grounds Physical – insufficient height, excessive height, blockages totalling > 180°, individual blockages > 60° Constructional – unsuitable roof, uneconomic construction, excessive modifications necessary to e.g. equipment room, other operators taking all available positions on object, unable to supply power or upgrade existing Financial – unable to agree economic terms with site owner. Needs input from radio planning re. importance Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

291

Day 5 Section 18 3G System Design Considerations

EMF Compliance Three main approaches: Field monitor/dosimeter approach Zoning approach Limit distance approach In cellular planning, we are only really interested in the ‘limit distance’ approach, as there is never any absolute necessity to be working in front of antennas

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

292

Day 5 Section 18 3G System Design Considerations

EMF Compliance (cont.)

Limit distance is marked out on the roof or otherwise around the antennas

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

293

Day 5 Section 18 3G System Design Considerations

EMF Compliance (cont.) The limit distance can be determined by knowing the number and power of ARFCNs and UARFCNs emitted from the antenna, and the allowed ‘specific absorbtion rate’ FCC Maximum Permissible Exposure Limits 1000

mW/cm²

100 Controlled exposure

10

1 0.1 0.1

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Unontrolled exposure 1

10

100 1000 Frequency (MHz)

104

105

294

Day 5 Section 18 3G System Design Considerations

EMF Compliance (cont.) 2450MHz is not a body absobtion maximum!!!

Ungrounded resonance approximately 70 MHz

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Grounded resonance approximately 35 MHz

295

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Terrain Effects Propagation over Smooth Earth Propagation over Irregular Terrain Diffraction and Microwave Interference Diffraction over Irregular Terrain Site Shielding, Obstacles and Building Effects

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

296

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Terrain Effects Generally choose ITU prediction model depending on whether or not terrain data is available ITU-R P.1546

start

Terrain data available?

Determination of path type, time percentage and frequency, steps 1-3 of Annex 6

Calculation, steps 4-6 of Annex 6 Correction factors, steps 12-17 of Annex 6

Hydrometeor Scatter Inferference Prediction

end Apply procedure of § 5

ITU-R P.452

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Clear air propagation model?

Apply procedure of § 3

297

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth ITU-R P.1546 model for point-to-area prediction Valid from 30 MHz to 3000 MHz Valid for RBS to UE distances from 1 km to 1000 km Valid for transmit antenna heights from 0 to 3000 m and receive antenna heights between 1 and 3000 m Input parameters are system type (analog or digital), channel bandwidth, environment (suburban, urban, rural) Choose ‘percentage time’ operating point, where this emulates propagation variabilities over the entire path length rather than Rayleigh-Rician fading Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

298

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) Propagation characterised for two percentage time (pt) bands, 1-10% and 10-50% and two frequency ranges 100MHz – 600 MHz and 600 – 2000 MHz Operating points and frequencies outside these reference ranges are intrapolated and extrapolated: If pt < 10% set ptlow = 1% and pthigh = 10% If pt ≥ 10% set ptlow = 10% and pthigh = 50% If f < 600 MHz set flow = 100 MHz and fhigh = 600 MHz If f ≥ 600 MHz set flow = 600 MHz and fhigh = 2000 MHz Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

299

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) For hRBS ≥ 10 m (i.e. the normal UMTS height range): Calculate the four ‘soft boundary’ field strengths to be used in the intra/extrapolation: E(flow, d, hRBS,hUE, ptlow), E(fhigh, d, hRBS,hUE, ptlow) E(flow, d, hRBS,hUE, pthigh), E(fhigh, d, hRBS,hUE, pthigh) Calculate dimensionless parameter k, to be used in the future electric field calculations:

k = log(hRBS / 9.375) / log(2) Determine the constants to be used for prediction Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

300

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) f LOW | fHIGH

100 MHz

600 MHz

2000 MHz

Pt %

50

10

1

50

10

1

50

10

1

a0

0.0814

0.0814

0.0776

0.0946

0.0913

0.087

0.0946

0.0941

0.0918

a1

0.716

0.716

0.726

0.8849

0.8539

0.8141

0.8849

0.8805

0.8584

a2

-30.444

-30.444

-29.028

-35.399

-34.160

-32.567

-35.399

-35.222

-34.337

a3

90.226

90.226

90.226

92.778

92.778

92.778

94.493

94.493

94.493

b0

33.6238

40.4554

45.577

51.6386

35.3453

36.8836

30.0051

25.0641

31.3878

b1

10.8917

12.8206

14.6752

10.9877

15.7595

13.8843

15.4202

22.1011

15.6683

b2

2.3311

2.2048

2.2333

2.2113

2.2252

2.3469

2.2978

2.3183

2.3941

b3

0.4427

0.4761

0.5439

0.5384

0.5285

0.5246

0.4971

0.5636

0.5633

b4

1.256E-7

7.788E-7

1.050E-6

4.323E-6

1.704E-7

5.169E-7

b5

1.775

1.68

1.65

1.52

1.76

1.69

1.762

1.86

1.77

b6

49.39

41.78

38.02

49.52

49.06

46.5

55.21

54.39

49.18

b7

103.01

94.3

91.77

97.28

98.93

101.59

101.89

101.39

100.39

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

1.677E-7 3.126E-8

1.439E-7

301

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.)

f LOW | fHIGH

100 MHz

600 MHz

2000 MHz

Pt %

50

10

1

50

10

1

50

10

1

c0

5.4419

5.4877

4.7697

6.4701

5.8636

4.7453

6.9657

6.5809

6.0398

c1

3.7364

2.4673

2.7487

2.9820

3.0122

2.9581

3.6532

3.547

2.5951

c2

1.9457

1.7566

1.6797

1.7604

1.7335

1.9286

1.7658

1.7750

1.9153

c3

1.845

1.9104

1.8793

1.7508

1.7452

1.7378

1.6268

1.7321

1.6542

c4

415.91

510.08

343.24

198.33

216.91

247.68

114.39

219.54

186.67

c5

0.1128

0.1622

0.2642

0.1432

0.1690

0.1842

0.1309

0.1704

0.1019

c6

2.3538

2.1963

1.9549

2.269

2.1985

2.0873

2.3286

2.1977

2.3954

d0

10

5.5

3

5

5

8

8

8

8

d1

-1

1

2

1.2

1.2

0

0

0

0

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

302

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) Calculate the ‘unblended to maximum’ field strength Eu E1+ E 2   pb  10  Eu = pb ⋅ log  E1 E2  10 pb + 10 pb   

(

pb = d 0 + d1 ⋅ k

)

E1 = a0 ⋅ k 2 + a1 ⋅ k + a2 ⋅ log(d ) + 0.1995 ⋅ k 2 + 1.8671 ⋅ k + a3

E 2 = Eref + Eoff

Eref

  log( d ) − b  2  2   − b6 ⋅ log(d ) + b7 = b0 exp − b4 ⋅ 10ξ − 1 + b1 ⋅ exp −  b3    

Eoff

k    c0 c3    C6 = ⋅ k ⋅ 1 − tanh c1 ⋅ log(d ) − c2 −    + c5 ⋅ k 2 c4      

[ [

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

] ]

ξ = log(d )b

5

303

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) Calculate the ‘blended to free space’ field strength Eb E u + E fs   10 pbb Eb = pbb ⋅ log  E E fs u 10 pbb + 10 pbb 

    

where Efs is the free space field strength

Efs = 106.9 – 20 log(d) dB(µV/m) and pbb is a ‘blending coefficient’, set to 8 Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

304

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) Perform intra/extrapolation in frequency to obtain the two values that will be used to estimate percentage time

E(ptlow) = E(flow,ptlow) + (E(fhigh,ptlow) - E(flow,ptlow)) x [log(f/flow)/log(fhigh/flow)] E(pthigh) = E(flow,pthigh) + (E(fhigh,pthigh) - E(flow,pthigh)) x [log(f/flow)/log(fhigh/flow)] where both field strength values are in dB(µV/m)

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

305

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) Calculate the field strength for a given percentage time

E(pt) = E(pthigh) · [(Q(ptlow) – Q(pt))/(Q(ptlow) – Q(pthigh))] + E(ptlow) · [(Q(pt) – Q(pthigh))/(Q(ptlow) – Q(pthigh))] where Q(x) is the inverse complementary cumulative distribution function (here the log-lin frequency axis is effectively coming out of the page)

Q

Q(10) Q(pt)

10 pt

50 Q(50)=0

100 Probability

(not to scale) Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

306

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) The field strength E(pt) is calculated at the ‘assumed clutter height’ R. There are many ways to calculate this parameter, one of which might be e.g. RMS value Now correct for UEs that are at a height less than R by calculating a ‘modified representative clutter height’

R’=R (m) for hRBS≤6.5d + R R’=(1000dR -15hRBS)/(1000d -15) for hRBS>6.5d + R d in km and R,hRBS in m Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

10 Modified Representative Clutter Height for hRBS=30m, R=10m

R

9.5

0

d

10 307

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) The modified representative clutter height is then combined with the UE height to calculate the height correction factor in urban areas: Correction = (6.03 hUE R′) − J (v)

hUE < R

= (3.2 + 6.2 log( f ))log(hUE R′) hUE > R

J (v) = 6.9 + 20 log  

(v − 0.1)2 + 1 + v − 0.1 

v = K nu hdif ϑclutter

K nu = 0.0108 f (MHz) Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

hdif = R′ − hUE

ϑclutter = arctan( hdif / 15) (°) 308

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) ITU-R P.1546 gives a procedure for calculation of field strengths with RBS antenna heights less than 10m, but this need not be used here as all of the heights of interest, even for street furniture sites, exceed 10m For UEs adjacent to land in a rural environment, the UE height correction (3.2+6.2log(f))log(hUE /R’ ) applies The height correction formula is not valid for UE height less than 1m

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

309

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) At a term corresponding to shadow (lognormal) fading For all analog systems and for digital systems with channel bandwidth

σL=K +1.6 log(f (MHz)) For cellular applications, K is 2.1 for urban locations and 3.8 for suburban locations and undulating terrain For digital systems with channel bandwidth > 1 MHz, as is the case for UMTS, σL=5.5 dB is used

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

310

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Smooth Earth (cont.) Limit field strength to that of free space and convert to pathloss:

E(pt)=min(E(pt)|Efs) Basic Transmission Loss = 77.2 – E(pt) 20 log (f ) where f is in MHz and E(pt) is the field strength calculated for 1 W e.r.p Now repeat for the other 9,999,999 points in the propagation prediction…

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

311

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Irregular Terrain From ITU-R P.452 § 3.2 Table 5, we are interested in: Line of sight with sub-path diffraction:

Lb ( p ) = Lb 0 ( p ) + Lds ( p ) + AhRBS + AhUE where Lds(p) is the sub-path diffraction loss for p% time Trans-horizon:

(

)

Lb ( p ) = −5 log 10 −0.2 Lbs + 10 −0.2 Lbd + 10 −0.2 Lba + AhRBS + AhUE

for near trans-horizon, i.e. interference from RBSs within 100km, only retain Lbd(p) term as other losses too high Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

312

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Irregular Terrain (cont.) ITU-R P.452 § 4.2 gives basic line-of-sight propagation loss not exceeded for time percentage p% as Lb 0 ( p ) = 92.5 + 20 log( f ) + 20 log(d ) + ES ( p ) + Ag

where the correction for multipath and focusing effects is

(

)

ES ( p ) = 2.6 1 − e − d 10 log ( p 50 )

and the gaseous absorbtion term Ag = [γ o + γ w (ρ )]d

can be neglected for the frequencies and distances of interest Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

313

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Irregular Terrain (cont.) ITU-R P.526 § 4 gives various formulae for sub- and super-path diffraction in the intermediate zone before trans-horizon propagation In the general case the point with the highest value of v along the path between RBS and UE is found. The diffraction loss for this diffraction point is calculated Along the semi-paths either side of the first, up to two more diffraction paths may be defined, depending on whether there is incursion of the terrain into the Fresnel zone. These losses are calculated and added to the first Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

314

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Propagation over Irregular Terrain (cont.) ν = h 2d λd1d 2

J (v) = 6.9 + 20 log  

(v − 0.1)2 + 1 + v − 0.1 

For each diffraction point considered with v > -0.7 Diffraction point 3

Diffraction point 1 Diffraction point 2 h

hRBS Earth ‘bulge’ hUE

d d1

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

d2

315

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Diffraction and Microwave Interference

Acknowledgement: ITU-R P.452 Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

316

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Diffraction over Irregular Terrain For transhorizon diffraction, the diagram below applies

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

317

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Diffraction over Irregular Terrain (cont.) From the position of the UE, a least squares fit of the terrain profile between UE and RBS is made, yielding an RBS ‘effective height’ hRBSe Maximum terrain height above the smooth earth surface in the transhorizon points hm is then found This height and the horizon interception points are then used to calculate the trans-horizon diffraction loss Lbd(p)

(

)

Lb ( p ) = −5 log 10 −0.2 Lbs + 10 −0.2 Lbd + 10 −0.2 Lba + AhRBS + AhUE

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

318

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Site Shielding, Obstacles and Building Effects The geometry for site shielding by distant and local obstacles is shown:

Acknowledgement: ITU-R P.452

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

319

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Site Shielding, Obstacles and Building Effects (cont.) Clutter local to a UE provides shielding from interference in addition to that provided by the main diffraction obstacle shown Additional clutter loss is obtained by lowering the UE antenna below the local clutter, as specified in ITU-R P.1058 This recommendation also sets out the main clutter classes, the characteristic heights of the clutter Hc and gap width Gc to be used in the ‘height gain model’

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

320

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Site Shielding, Obstacles and Building Effects (cont.) Clutter (ground cover) category

Nominal Height, ha (m)

Nominal Distance, dk (km)

High crop fields, park land, irregularly spaced sparse trees, orchard (regularly spaced), sparse houses

4

0.1

Village Centre

5

0.07

Deciduous trees (irregularly and regularly spaced), mixed tree forest

15

0.05

Coniferous trees (irregularly and regularly spaced)

20

0.05

Tropical rain forest

20

0.03

Suburban

9

0.025

Dense suburban

12

0.02

Urban

20

0.02

Dense urban

25

0.02

Industrial zone

20

0.05

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

321

Day 5 Section 19 ITU-R Propagation Models and Prediction Methods

Site Shielding, Obstacles and Building Effects (cont.) Calculate the basic transmission loss to the nominal clutter height ha. The path length to be used is d-dk, although for d>>dk this correction can be ignored Pathloss due to the main site shielding obstacle, if any, is calculated to height ha at distance ds rather than UE height h at distance dL Add the clutter height correction factor Ah = 10.25 × e

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

−dk

   h  1 − tanh 6 −  − 0.625   − 0.33 h        a  322

Day 5 Section 20 Key Perfomance Indicators

ITU T E800 and ETSI ETR003 Classification of QoS Accessibility, causes of failure and how to improve Retainability, causes of failure and how to improve Mobility, causes of failure and how to improve Quality, causes of failure and how to improve

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

323

Day 5 Section 20 Key Perfomance Indicators

ITU T E800 and ETSI ETR003 Classification of QoS fast

Intrinsic QoS “the collective effect of service performance which determine the degree of satisfaction of a user of the service” Assessed QoS

Perceived QoS

slow fast ‘Kepler Orbit’ view of QoS Flow Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

324

Day 5 Section 20 Key Perfomance Indicators

ITU T E800 and ETSI ETR003 Classification of QoS (cont.) Intrinsic QoS – directly measurable network parameters e.g. PDP packet loss, packet delay, call setup time Perceived QoS – quality perceived by users, assessable as ‘mean opinion score’ for selected services Assessed QoS – Hybrid quality score, part user feedback e.g. coverage quality from a particular area, and compound performance indicators not directly available from the network e.g. minutes per drop, bytes per disconnect

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

325

Day 5 Section 20 Key Perfomance Indicators

ITU T E800 and ETSI ETR003 Classification of QoS (cont.) Intrinsic QoS, adjustable via RAN parameters, does not map directly onto customer perceived QoS due to the existence of different service classes; Conversational: preserve the time relationship between information entities in the stream (e.g. sound and video in sync), conversational pattern, stringent and low delay Streaming: preserve time relationship between entities Interactive: preserve payload and response pattern Background class: destination is not expecting the data within a certain time, preserve payload content Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

326

Day 5 Section 20 Key Perfomance Indicators

ITU T E800 and ETSI ETR003 Classification of QoS (cont.) Major equipment vendors and operators themselves adopt slightly different meanings and nuances for the following KPIs. This leads to confusion when comparing performance e.g. of two networks within the same territory by a national regulator The following treatment generally follows the Ericsson nomenclature for the simple reason that this seems both most self-consistent and forms the bulk of the author’s experience This is not to be construed in any way as an endorsement of Ericsson as a technical authority or equipment vendor Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

327

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve Accessibility describes numerous RAN functions: RRC Connection Attempts and Successes – the UE establishes a point to point signalling link with the RAN RAB Establishment Attempts and Successes – the UE builds a traffic connection with the core network via RNC

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

328

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve (cont.) No RRC Connection Request RRC Connection Reject from RNC to UE RRC Connection Establishment Failure

RRC Connection Setup from RBS, no RBS to RNC Radio Link Restore

RRC connection failure after RRC Connection Setup Complete from UE to RBS No RRC Setup Complete message to UTRAN

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

329

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve (cont.) No RRC Connection request implies failure in previous RRC Connection Release: Only one RRC Connection is possible and even defined per UE If UE does not send RRC Connection Request in response to a page then a previous RRC Connection Release has probably been missed Improvement – this is probably only relevant during testing, when poor coverage is encountered and a call is retried before RRC Connection timeout in the UE Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

330

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve (cont.) No RBS to RNC ‘Radio Link Restore Indicator’ implies that the UE and RBS are failing to synchronise on the uplink If the UE is observed to reach maximum transmit power, this is most likely caused by either uplink and pilot coverage imbalance or less likely by incorrect cell reselection offset value causing idle mode reselection outside UL DPCH range Improvement – A classic initial optimisation problem. Rebalance CPICH(s) on problem site(s) from setup default. Check cell reselection offset values Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

331

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve (cont.) No UE to RBS ‘RRC Connection Setup Complete’ after UE receives RRC Connection Setup and starts transmission implies downlink radio link synchronisation failure The downlink CPICH coverage and DL DPCH coverage may be imbalanced. Alternatively another common reason that this can occur is that too low an initial downlink SIR target has been set in the RBS Improvement – rebalance CPICH coverage or increase Maximum DL DCH power (this has implications for DL capacity of this RBS. Required initial SIR depends on radio environment so RNC defaults for RBS may be unreliable Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

332

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve (cont.) RRC connection failure after the UE to RBS ‘RRC Connection Setup Complete’ message implies poor uplink quality The UE will power down to zero if bad DCH downlink quality is received, this also happens if the CPICH cannot be received correctly so that channel estimates are inaccurate. By identity this will result in poor UL quality. Conversely, the UE may be at maximum TX power in a poor quality channel Improvement – this is usually a feature of trying to connect at the edge of 3G coverage. The solution is to change reselection parameters to select to 2G Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

333

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve (cont.) RRC Connection Reject message with cause value set to ‘congestion’ from RNC to UE implies excessive RNC load In 3G, the RNC has a far larger role than the 2G BSC, and is responsible for synchronising and combining link data. If the RNC area is too large, or traffic unexpectedly rises, then soft capacity will run out before any individual RBS Improvement – redimension the RNC processing power

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

334

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve (cont.) UE sends Radio Bearer Setup Complete message to RNC but it is not received

No Radio Bearer Setup from RNC to UE

Radio Access Bearer Establishment Failure

UE receives Radio Bearer Setup but fails to respond with Radio Bearer Setup Complete

Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

Radio Bearer Setup from RNC not received by UE

335

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve (cont.) No ‘Radio Bearer Setup’ command from RNC to UE implies cell blocking, with insufficient radio or hardware resources at the serving RBS There are a number of reasons that there might be insufficient cell baseband and RF resources. In the optimisation phase, the most likely cause is a uniform pilot setting in an irregular network, causing the RBS to pick up an abnormally high amount of traffic, and the related problem of this causing excessive soft handover connections Improvement – carefully adjust CPICH power and downtilt antennas to reduce soft and softer handover regions Copyright © 2008 Telefocal Asia Pte Ltd. All rights reserved.

336

Day 5 Section 20 Key Perfomance Indicators

Accessibility, causes of failure and how to improve (cont.) Radio Bearer Setup from RNC not received by the UE implies poor downlink quality This is usually symptomatic of a UE at the edge of 3G coverage, but this can be for a number of reasons The most likely cause is failure to perform channel estimates due to poor quality CPICH, i.e. Ec/Io