Day1.2 WCDMA RAN Dimensioing

Radio Network Dimensioning

Contents •Scope of RAN Dimensioing •Input parameters for RAN dimensioing •Link Budget Parameters Cell Range Calculation

•Load Calculation

Contents •Scope of RAN Dimensioing •Input parameters for RAN dimensioing •Link Budget Parameters Cell Range Calculation

•Load Calculation

WCDMA Network Architecture

GPRS GSM/WCDMA mobile

3G SGSN

RAN

Internet TCP/IP)

Circuit Switched Core Network GGSN

SRR

RNC USIM card

PS Core Network

GSM/WCDMA mobile

WCDMA BTS

HLR MSC MGW

WCDMA BTS WCDMA mobile

RNC

CBC

(PSTN/ISDN)

IN SCP

UTRAN Elements and Interfaces UTRAN WCDMA BTS

Uu

RNC WCDMA BTS

Iub User Equipment (UE)

Iur 

WCDMA BTS

RNC WCDMA BTS

Iu

Core Network (CN)

Example: What affects performance in WCDMA • support of 3GPP QoS-parameters and mechanisms in UE • UE support of different CH-types • internal delays generated by UE • UE memory [effects TCP kbps] • UDP vs. TCP •supported HTTP/WAP-version

• internal processing/queuing delays. • protocol processing and transmission delays, 3GPP QoSsupport

• 3GPP QoS-support

• Iu-transmission resource dimensioning, topology/distances

• internal delays in WAPgateways/httpproxies/servers/etc.

• packet core capacity

• application server capacity

• configurati configuration on of RT traffic limits

• geographical location [e.g. localized content caching vs. centralized servers]

• configuration of interactive queue weights • used HLR QoS-profiles

• supported HTTP/WAP-version • support of optimization features

• support of optimization features

3G-SGSN

IP/MPLS/IPoATM-backbone GGSN

RNC

• RNC internal delays, 3GPP QoSsupport

• internal processing/queuing and L1 delays

• internal BTS-delays

• RNC capacity

• memories/buffe memories/bufferr sizes [TCP-effect]

• interleaving/propagation delays

• HO thresholds

• transmission/rou transmission/router ter capacity

• site locations,

• cell's traffic load thresholds

• geographical locations/distance, number of hop

• antenna directions/height/quality

• interference/transmission power thresholds

• cable length/quality

• used packet scheduling criteria

• BTS-capacity

• used RLC buffer payloa payload d thresholds [TCP-effect] • used DCH bit rate allocation steps • allocation of dedicated NRT-capacity

Application Servers (co-located or remote)

= terminal/NW element HW and SW effects = application software effects = network planning/dimensioning effects

RAN Dimensioing Scope RN C Iub

Node B

CAP/MAP CAP/MAP (E1) (E1)

Iu-CS (ATM )

Iub

MSS Mc RANAP (SIGTRAN)

BSSAP (E1)

Abis

Border  Gateway (BG)

2G / 3G HLR

MAP (SIGTRAN)

New Connect

MGW

Iu-PS

LI G

Gb 2G SGSN

SS7 (E1)

PSTN/PLM N Network

3G SGSN IP/ATM/TD M Backbone

Backbone network (IP based)

Packet Internet network

GGS N

Packet

Inter-PLMN network Network

Exist Connect

CDS BS C

BTS Charging Gateway (CG)

SMS

IN/SCP

Domain Name Server 

Domain Host Configuration Protocol (DHCP)

Fire Wall

Packet Intranet network

Network planning process & relation to business planning

 Network  dimensioning

marketing

business plan

transmission  plan

 Network  optimization

coverage  plan  parameter   planning

traffic assumptions

Code & freq. & interference plan final NW topology/ architecture

Radio Network Dimensioning Overview

COVERAGE

CAPACITY

COMPROMISE BETWEEN COVERAGE AND CAPACITY

Coverage VS Capacity Dimensioning: Cell Breathing [1/2] • This diagram shows

This diagram shows when some cells are loaded 

cells are unload  Cell A Cell A

CellB CellB

CellC

Cell breathing

CellC

Resu lts =>  Coverage Holes! 

Coverage VS Capacity Dimensioning: Fixed Uplink Load - To avoid Coverage holes [2/2] "actual" Loading,

This diagram shows a Fixed Uplink Load design

(ie from the traffic inputs defined in dimensioning)

• No (or minimum) coverage holes problems • More cells required

CellB Cell A

Cell A CellB CellC

eg. Actual UL load = 8%

CellC CellD

Cell-H

into account. (Note: dimensioning assumes

CellF CellE

• Traffic mobility taken

uniform traffic distribution)

CellG

eg. Fixed UL load = 30%

Results => No or  Min Coverage Holes! 

Input parameters – overview Input Categories 





CAPACITY RELATED 

Spectrum Available



User Profile and Traffic Growth Forecast



Traffic Density Map

COVERAGE RELATED 

Coverage Regions



Area Type Information



Gives an Estimation of the Equipment Necessary to Meet the Network Requirements



Network Dimensioning Activities 

Radio Link Budget Calculation



Cell Size Calculation



Capacity Calculation



Number of Node B, RNC calculation



Iub, Iur and Iu transmission Capacity

QUALITY RELATED 

MS Class



Indoor Coverage



Location Probability



Blocking Probability

Capacity Related Input The number of subscribers, user profile and spectrum available are the main requirements for  capacity dimensioning Traffic forecast should be done by analysing the offered Busy Hour traffic per subscriber for different service bit rates in each rollout phase. Traffic data: •Voice :  –Erlang per subscriber during busy hour of the network  –Codec bit rate, Voice activity

•RT data :  –Erlang per subscriber during busy hour of the network  –Service bit rates •NRT data :  – Average throughput (kbps) subscriber during busy hour of the network  –Target bit rates  Asymmetry between UL an DL traffic for NRT Services (Downloading 1/10) should be taken into consideration. Network and Subscribers evolution forecast is also needed.

Coverage Related Input  Accurate coverage area information should be available

• Total coverage area for each rollout phase (km 2) • Percentage of the area for each morpho class (Dense Urban, Urban, Suburban and Rural)

DENSE URBAN

URBAN

SUBURBAN

Coverage Related Input  Area type information must be as accurate as possible:

• coverage area for each rollout phase • percentage of the area for each morpho-class (DU,U,SU,R) • building penetration loss and fading margin

MorphoClass

Dense Urban Urban Sub Urban Rural Road

Build Pen Loss

18 dB 15 dB 12 dB 10 dB

Stand Deviation

Car Loss

Stand Deviation

11 dB 10 dB 9 dB 9 dB 6 dB

7 dB

• propagation models for path loss calculation • correction factors for the Propagation Model Service Scenarios should be defined: which kind of service is to be offered and where (big impact on the number of sites).

Quality Related Input Blocking Probability: is blocking of call attempts due to lack of available resources and for CS Services is usually between 1-2% In the propagation models there is no place to cover the local fluctuations (slow fading) of the strength of the electromagnetic waves, caused mainly by shadowing. It should be done separately. Fade margin is a function of location probability and standard deviation

Quality Related Input Penetration Losses Signal levels inside the buildings are estimated by applying “building penetration loss” margins. BPL may vary in different area types.

signal level increases with floor  number :~1,5 dB/floor (for 1st ..10th floor)

Pindoor  = -3 ...-15 dB rear side : -18 ...-30 dB

Pindoor  = -7 ...-18 dB

Pref  = 0 dB

-15 ...-25 dB

no coverage

Summary of Dimensioning Inputs Dense Urban

Urban

Suburban

Rural

Voice

# of subs & mErl per sub

# of subs & mErl per sub

# of subs & mErl per sub

# of subs & mErl per sub

CS data

# of subs & mErl per sub

# of subs & mErl per sub

# of subs & mErl per sub

# of subs & mErl per sub

PS data

# of subs & kbps per sub

# of subs & kbps per sub

# of subs & kbps per sub

# of subs & kbps per sub

km2

km2

km2

km2

Location probability

%

%

%

%

Standard deviation

dB

dB

dB

dB

Fade margin

dB

dB

dB

dB

Penetration loss

dB

dB

dB

dB

Area correction factor 

dB

dB

dB

dB

MS / Node B antenna height

m

m

m

m

Coverage area

RF Dimensioning Process

RF Dimensioning Process Flow Radio link specific : - Data rate (processing gain) - Average Eb/No - SHO gain in dB Inter ference Margin 1st guess of amount of traffic per CU

Load factor  calculation

Max. traffic per CU

If too low capacity

Link Budget Calculation Max. allowed path loss

Cell Range Calculation Max. Cell Range in each area type

Capacity Estimate No. of sites / Total supported traffic in each area type

Equipment specific : - MS Power class - MS/BS calc. sensitivity - Antenna gain etc

Propagation specific : - Antenna height - BPL and BPL deviation - Area correction factor  - Lognormal shadowing margin Service specific : -blocking rate - throughput factor 

If fulfill the operator need

Equipment Requirement BS HWs / Transmission / RNC

WCDMA Link Budget

Link Budget Overview  Antenna gain Noise figure Body loss Cable losses Building penetration loss

WCDMA Link Budget MS transmit power = 21 dBm

Antenna Gain (example):

• 18 dBi, X-pol, 650 horizontal beamwidth, variable electrical tilt

Cable Losses

Body proximity Loss

• 3 dB for voice services • 0 dB for data services

WCDMA Link Budget

Soft HO Softer HO

Soft HO MDC gain is actually the gain due to less power  requirement when multiple radio links are there (relative to that of a single link ) This gain is mainly in DL and in UL this gain is negligible

WCDMA Link Budget MDC Gain: In DL there is some combining gain due to UE maximal ratio combining:

• Soft/softer handovers are included • Average is calculated over all the connections taking into account the average difference of the received signal branches (and UE speed)

• Nokia recommended value = 1.2 dB MHA gain is used to compensate for the cable losses

WCDMA Link Budget Total noise power in the receiver is a function of:

• Boltzman’s constant • Temperature • Bandwidth  –Thermal Noise = kTB

• Noise figure Nokia recommended values:

Noise Figure

Node B

MS

3 dB

8 dB

WCDMA Link Budget Processing gain is a function of the system chip rate and service bit rate

Service bit rate

Processing Gain

Voice 12.2 kbps

24.98 ~ 25 dB

CS 64 kbps

17.78 ~ 18 dB

PS 128 kbps

14.77 ~ 15 dB

PS 384 kbps

10 dB

WCDMA Link Budget Interference margin calculated from the UL/DL loading ( ) values. This parameter shows in DL how much the BTS "sensitivity" is decreased due to the network load (subscribers in the network) & in UL indicates the loss in link budget due to load.

IMargin =  10  Log 10 1   

dB

WCDMA Link Budget In order to meet the defined quality requirements (BLER) a certain average bit-energy divided by total noise+interference spectral density (Eb/N0) is needed. Eb/No depends on:

• Service • MS speed • Radio channel

Service bit rate

UL Eb/No [3kph]

DL Eb/No [3kph]

Voice 12.2 kbps

4.4

7.9

CS 64 kbps

2.0

5.0

PS 64 kbps

2.0

5.0

PS 128 kbps

1.4

4.7

PS 384 kbps

1.7

4.8

WCDMA Link Budget Soft handover gain is the gain against shadow fading. This is actually the gain in required Eb/No relative to that of a single link and it is averaged over all radio links in the SHO area

• Nokia recommended value = 2 dB IPL Correction Factor. This parameter describes the ratio between the maximum and the average pathloss. Usually all subscribers are not located at the cell edge but are distributed through the whole cell coverage area. That is why some gain can be added in power budget calculation.

• Nokia recommended value = 6 dB

IPL Correction Factor 

Worst case scenario

Reality – MS distributed over the whole area

Users at the cell edge require high power; users close to the base station need much less power at the same time

WCDMA Link Budget UL Power Control Headroom is the parameter to describe the margin against fast fading. This parameter is needed because at the cell edge the UE does not have enough power to follow the fast fading dips. This is especially important for the slow moving UEs.

• Nokia recommended value = 1.8 dB

Cell Range CELL SIZE  Antenna height Node B  Antenna height UE Correction factor

12.2kbits 30.00 1.50 0.00

64kbits 30.00 1.50 0.00

128 kbits 30.00 1.50 0.00

Outdoor location prob. Outdoor standard deviation Slow fading margin Outdoor cell size

95% 7.00 7.27 2.27

95% 5.00 4.51 2.36

95% 5.00 4.51 1.93

Indoor location prob. BPL Indoor standard deviation Slow fading margin Intdoor cell size

95% 18.00 12.00 14.64 0.43

95% 18.00 12.00 14.64 0.37

95% 18.00 12.00 14.64 0.31

In car location prob. Car PL In car standard deviation Slow fading margin In car cell size

95% 5.00 8.00 8.70 1.49

95% 5.00 8.00 8.70 1.29

95% 5.00 8.00 8.70 1.06

In the dimensioning process, the cell range [R] is set by the shortest radio link (service class with lowest cell range). The number of sites can be determined by the following relation: # of sites = coverage area / site area where: site area = K * R 2

Sector

K value

Omni

2.6

1

0.65

2

1.30

3

1.95

6

2.60

Load Calculation

Load Calculation Load factor ( ) predicts the amount of noise rise by treating interference as wideband noise.

It is based on Eb/No, number of users, their service bit rate and activity, other cell to own cell interference ratio, the amount of uplink noise rise and orthogonality factor.

Load Calculation In order to meet the defined quality requirements (BLER) a certain average bit-energy divided by total noise+interference spectral density (E b/N 0 ) is needed. So for every user  j  and for given bit rate R   j  we have:

  E b   W   I  j       N 0   j  R j  I tot   I  j , where I  j  is the received signal power of user j  j  is not active all the time, that is why the special activity factor  Of course subscriber  should be introduced:

  E b   W   I  j 1        N 0   j  R j  I tot   I  j   j

 j

Load Calculation Using the previous equation we can express the load caused by one subscriber as a part of  the total load:

 I  j

 load  j  I tot 

, where:

load  j

1 W   R j

 1

 E b

 N 0  j



1   j

For N subscribers, the load caused in the  N  cell (so called load factor ) is:

  

 load  j  j

Little i  The load factor calculation the other cell interferences takes into account the interference from other cells. This can be introduced by means of the little i value, which describes how much two cells overlap (bigger overlapping  more inter-cell interferences).

Sector

Little i 

Omni

0.55

3 0.65 * Nokia recommended values

Iother 

Intereference in DL

Interference in UL

Orthogonality Orthogonality [ ] is a measure how w ell separate code signals are uncorrelated In DL the own cell interference are reduced by factor (1- ). This is due to the synchronised orthogonal channelisation codes, which are used in DL.

Nokia recommended value: [ ] = 50%

Load Calculation  After introduction of the little i  the load factor in the cell will be:  N 

 

 1  i  load  j  j

In DL the own cell interference is reduced by factor (1- ). This is due to the synchronised orthogonal channelisation codes, which are used in DL:  N 

  DL

 1    j   i   load  j  j

• Ortogonality factor  j is between 0.4 and 0.9 Typical values:

• ITU vehicular subscriber (Macro Cell) • ITU pedestrian subscriber (Micro Cell)

 j=0.6  j=0.9

Power Rise For UEs located in the other cells the power increase caused by Fast Loop PC procedure is harmful for the own cell interference conditions

No n -fad in g c h an n el

Received power 

Fad in g c h an n el  

Transmitted power 

Power rise

 Average transmitted power 

Nokia recommended value: [p w r _ r i s e ]  = 0.7 dB

Load Calculation Because of power rise in the UL load calculation, the little i should be corrected (little i is multiplied by p w _ r i s e  parameter)  N 

 UL

 1   pw _ rise  i    load  j  j

UL load affects the noise level at the Node B receiver. Noise Rise  A typical cell load value for dimensioning ranges from 30% to 70 %. 18 16 14 12        B        d 10        /      s      s 8      o        l

6 4 2 0          0          1

         0          2

         0          3

         0          4

         0          5

         0          6

         0          7

         0          8

         0          9

         5          9

         8          9

loading/%

50% is a good compromise between the number of sites and the offered capacity.

Interference Margin vs Load Factor  The graph shows relationship between the interference margin and the load factor.

IMargin [dB] 20

Nokia recommends loading between 30% to 70% for optimum performance

10 6 3 1.25 25%

50%

75%

99%

50% uplink loading represents a good Load factor  trade-off between coverage and capacity

Cell Loading Calculation 1. Traffic per Cell Erlang or kbit/s

Traffic per cell is usually defined in terms of Erlang for  voice and real time (RT) data services and in terms of  kbits/s for non real time (NRT) data

2. Traffic Channels

3. Physical Channels (=traffic channels*SHO)

4. Interfering Channels (=physical channels*activity factor)

5. Fractional Load

The blocking probability is typically assumed to be 2% for  circuit switched services.

Cell Loading Calculation 1. Traffic per Cell Erlang or kbit/s

Evaluation of the physical channel requirement per carrier  for each service class. This is completed separately for  UL and DL.

2. Traffic Channels

Soft handover overhead (SHO) 3. Physical Channels (=traffic channels*SHO)

4. Interfering Channels (=physical channels*activity factor)

• Nokia value = 40% assumption: 30% = 2-way connections 5% = 3-way connections

5. Fractional Load

Therefore: (1 * 0.65) + (2 * 0.30) + (3 * 0.05) = 1.4 Evaluation of interfering channels per cell for each service class. This requires a direct multiplication of the physical channel requirement with the corresponding service activity factor.

Cell Loading Calculation 1. Traffic per Cell Erlang or kbit/s

2. Traffic Channels

3. Physical Channels (=traffic channels*SHO)

4. Interfering Channels (=physical channels*activity factor)

5. Fractional Load

The fractional load for each service are evaluated separately for both uplink and downlink The table below shows an example calculation:

Code Channels Calculation 1. Traffic per Cell Erlang or kbit/s

Hardware Channels

2. Traffic Channels

3. Physical Channels (=traffic channels*SHO)

4. Interfering Channels (=physical channels*activity factor)

5. Fractional Load

HW channels are implemented on channel cards (WSP cards) The signal processing unit (WSP) in the Node B performs RX and TX code channel processing, coding and decoding functions.  Amount of WSPs shall be planned according to the traffic on the BTS.

Channels Calculation 1. Traffic per Cell Erlang or kbit/s

2. Traffic Channels

Hardware Channels

The code channels (HW channels) needed for  different services are as follows:

3. Physical Channels (=traffic channels*SHO)

Service

4. Interfering Channels (=physical channels*activity factor)

Code Channel

Voice

1

64 kbps service (RT/NRT)

4

128 kbps service (RT/NRT)

4

384 kbps service (RT/NRT)

16

5. Fractional Load

Code channel requirement for common channels: Configuration USING WSPC

Code Channel

1+1+1

16

2+2+2

32

3+3+3

48

BTS Power  The link budget provides the average BTS TX power per connection for each service class. The BTS TX power per connection is defined from the average DL isotropic path loss. The total BTS TX power is obtained by summing up the TX power required for all service classes and common channels For dimensioning, the amount of power allocated for common channels is 20% of  the maximum BTS TX power.

TRAFFIC NODE B POWER COMMON CHANNELS

Dimensioning Results

Dimensioning Results TRAFFIC TRAFFIC Erlang or kbit/s Erlang or kbit/s

TRAFFIC CHANNELS TRAFFIC CHANNELS

Limiting factors: PHYSICAL CHANNELS PHYSICAL CHANNELS

Required HW channels (BTS processing capacity) INTERFERING CHANNELS INTERFERING CHANNELS

Load

Required BTS TX power

FRACTIONAL LOAD FRACTIONAL LOAD



FRAC. LOAD OF THE FRAC. LOAD OF THE SERVICE CLASSES SERVICE CLASSES

TOTAL LOAD TOTAL LOAD UL & DL UL & DL

REQUIRED BTS TX REQUIRED BTS TX POWER  POWER 

The following criteria should be considered:

• Uplink load < Maximum uplink load • DL load < 1 • BTS TX power < Maximum BTS TX power  • Number of channel units < Max number of channel units

Dimensioning Results

RF DIMENSIONING RESULTS Number of base stations Configuration of base stations Number of subscribers per area mErl / subs for voice and RT data mErl / sub for NRT data

Iub/Iur/Iu INTERFACE DIMENSIONING RNC DIMENSIONING

Link Budget

Link Budget Exercise…

Cell Loading Calculation

UL Fractional Load Calculation

DL Fractional Load Calculation