A.understanding MW Link

Training Module on MW radio engineering

Learning today……

    

Understanding Microwave link : applications, configuration, operating parameters, system calculations Line of Sight requirements and Antenna Heights Antenna Installation alignment and its parameters, safety and quality MW Link Installations and commissioning : standard practices : NEC’s approach Concluding : General site issues: questions & answers

excerpt from the Scientific American

July 1892

In the specification to one of his recent patents, Thomas A. Edison says: “I have discovered that if sufficient elevation be obtained to overcome the curvature of the earth’s surface and to reduce to the minimum the earth’s absorption, electric signaling between distant points can be carried on by induction without the use of wires.” MICROWAVE PATH ENGINEERING – OVER 110 YEARS AGO!

1

Basic characteristics

• Operates on a “Line-of-sight" principle • Use Two antennas aimed directly at one another • Transmit Digitally modulated Microwave Frequencies through free space from one terminal to another • Typically transmit simultaneously in both directions (Full Duplex)

Line of sight Point to Point MW link 400

300

200

100

0 .5

1 .0

1 .5

2 .0

2 .5

3 .0

3 .5

4 .0

4 .5

5 .0

D is ta n c e ( m ile s )

T y p ic a l P a th P r o file

Deployment and applications FWS (Point-to-Point Transport) and FWA (BWA, Access) Hops POP – Point of Presence

ClearBurst MB Point-to-Multipoint FWA (Fixed Wireless Access) Broadband Links

155 Mbit/s So net/SDH FWS (Fixed Wireless Sys tem) Hop

Nodal (Hub) Site CPE

CPE

CPE

PB X

CPE – Customer’s Premises Equipment:

- Sonet/SDH (PTP) - ATM Switch

- Frame Relay - Video

Conference

- LAN/IP - POTS

- Base Station - Sonet/ SDH

- T1/E1 - ISDN

FWS and FWA (BWA) Radio Hops Long Distance 2xT1/E1 Unlicensed Hop

Access Hops

Short Distance SONET/SDH Hop

Short Distance 4xT1/E1 Hops

OC-12 or STM-4 Fiber Ring X X

NMS system

Transport Hop Sonet/SDH NxOC-3 or NxSTM-1 Backbone FWS (Radio-Relay) Hop

GSM Network layout

Fiber and MW transmission media in GSM/CDMA Networks

FWS Microwave Applications PCS/Cellular Site Interconnection (North American Hierarchy)

1

z (N 8 GH

18 G Hz (

1) x DS

MTSO (MSC) - Switching Office BTS - Base Station BSC - Base Station Controller 23 GHz (OC-3)

DS3 )

38 G

BTS

Hz ( Nx

BTS

DS1 )

BTS

BSC (DS3 or OC-3NxO C-3 ) or 155 (Nx0 C

MTSO (MSC)

BTS -3) Self-Healing

Ring

BSC

Access and metro /transport networks

Core Network Topologies

Some Attributes of Digital Microwave Radios • •

Superior availability - route security (no cable cuts) Rapidly expandable and upgradeable, in-service if protected

•

High quality - no multihop “noise” addition

•

Rapid deployment over difficult terrain and into urban areas

•

Economical - no copper or fiberoptic cable deployment

•

Robust to fading and interference

•

Insensitive to antenna feeder system and long-delayed on-path echoes

•

Highly efficient data and broadband transport

•

Exacting in-service visibility of radio hop performance with NMS

•

Seamless interconnectivity to an ever-expanding digital transport (fiberoptics and other), PABX/MSC switch, and LAN/IP world.

Typical Electromagnetic spectrum M o b ile R a d io V H F T e le v is io n F M B r o a d c a s t R a d io S h o r tw a v e R a d io M o b ile R a d io F ib e r O p tic s A M B r o a d c a s t R a d io

V is ib le L ig h t

U H F T e le v is io n M ic r o w a v e s

1M H z

1000m (3 0 0 K H z )

10M H z

100m (3 M H z )

100 M H z

10m (3 0 M H z )

1G H z

1m (3 0 0 M H z )

10G H z

10cm (3 G H z )

100G H z

1cm (3 0 G H z )

10

1m m (3 0 0 G H z )

12

10

14

Transport and Access Bands Network Management Element Manager SNMP Interface

Capacity NxOC-3/STM-1 3xDS3/OC-3/STS-3 4xDS3, 4xE3/STM-1

1:N

Backbone Transport Broadband Wireless Access (FWA)

DS3 or 28 T1 E3 or 16 E1 16 T1

Backbone & Access

8 E1 4 T1/E1

Access

Unlicensed

2 T1/E1 T1/E1 8 6 Frequency Band: 2 Typical Path Lengths: >15-60mi/25-100km

11 13 10 18 37 42 GHz 23 26 7-15mi/12-25km 5-10mi/8-17km 1-5mi/2-8km

Example of capacity and frequency bands

CEPT PDH Hierarchy VF/data/LAN/IP and teleconferencing circuits 1 2. ..

1st Order

2.048 Mbit/s (30/31 Ch)

30/31*

PCM Channel Banks

E1

1 2 3 4

M2-8

8.448 Mbit/s (120 Ch)

2nd Order

E2

1 2 3 4

E3 M8-34 3rd Order

34.368 Mbit/s (480 Ch)

E4

*30 VF Channels with signaling channel or 31x64 kbit/s Data Channels (no signaling) E3 16 x 2.048 Mbit/s E1 Trunks

1 2. .. 16

M2-34 SkipMux mux Skip

1 2 3 4

M34-140 Radio MUX

140 Mbit/s (1920 Ch)

34 Mbit/s (480 Ch) PDH -Plesiochronous (asynchronous) Digital Hierarchy

CEPT Hierarchy is the international TDM digital standard everywhere except North America (USA, Canada), Taiwan, Korea and Japan.

TDM: CEPT PDH Hierarchy PDH - Plesiochronous Digital Hierarchy Designation

No. of E1 Trunks

Bit Rate (kbit/s)

Line Code

Voice Channel Equivalent

E0 E1 E2 E3 E4

30/31 = 1E1 1 4 16 64/63*

64 2,048 8,448 34,368 139,264

AMI HDB3 HDB3 HDB3 CMI

1 30 120 480 1920/1890*

CEPT PCM Analog-Digital PCM Quantizing Code is A-Law AMI, HDB3, & CMI codes are bipolar. Cable types: 120Ω Twisted Pair, 75Ω Coax (Length/type assigned for 6 dB maximum loss) Ref: ITU-T G.703, G.704

*63 E1 (1890 VF ch) are mapped in Synchronous Digital Hierarchy (SDH)

SDH Fundamentals: Rates Line Rate (Mbit/s)

SDH Signal

PDH Signal # E1 (2048 kbit/s)

VF

Transport

Radio or Fibre

2.048

VC - 12

1

30

34.368

VC - 3

16

480

51.84

Sub-STM-1*

21

630

139.264

VC - 4

64

1,920

155.52

STM - 1

63

1,890

622.08

STM - 4

252

7,560

2488.32

STM - 16

1,088

30,240

1:N Radio or Fibre

9953.28

STM - 64

4,032

120,960

Fibre

Ref.: ITU-R Rec. F.750-3 (1997)

SDH Synchronous Digital Hierarchy PDH Plesiochronous Digital Hierarchy *Sub-STM-1 RR-STM, STM-0 = 51 Mbit/s for Radio Relay)

SDH Fundamentals: Mux Pointer Processing SDH Synchronous Digital Hierarchy STM Synchronous Transport Module VC Virtual Container TU Tributary Unit TUG Tributary Unit Group AU Administration Unit AUG Administration Unit Group ATM Asynchronous Transport Mode RRRP Radio-Relay Reference Point NNI Network Node Interface Sub-STM-1 = RR-STM (52 Mbit/s for radio) = STM-0

Multiplexing Aligning Mapping

DS1

VC11

TU11

E1 DS1

VC12

TU12

DS2

VC2

x3 x1

TUG-2

x1

E3 DS3 x1

E4 ATM

TU-2

x4

VC3 x1

x1

VC3

x7

TU-3

TUG-3

x3

AU3

Sub-STM-1

x3

AUG

x1

VC4

Note: Bold indicates commonly available multiplexer interface

RRRP

AU4

x3

STM-N

NNI

Basic Building blocks of MW Link

Basic Building blocks of MW Link

Classical Design Waveguide

Waveguide

RF f [GHz]

Circulator, Filter (CBN)

Circulator, Filter (CBN)

RF = Radio frequency e.g. 7.5 GHz, 18.7 GHz

TX

RX

Transmitter

Receiver

IF = Intermediate frequency e.g. 140 MHz Modulator 16 - 128 QAM

Demodulator 16 - 128 QAM

BB = Baseband e.g. 155 Mbit/s Channel

Channel

Basic blocks of radio

IDU

Important to know…

IDU Functional blocks

ODU configuration

ODU Layout

• Outdoor Units (ODUs) are software configurable so that capacity upgrades can be made without climbing towers. • Indoor Units (IDUs) support capacities of 2/4E1, 4/8E1, 16E1, E3, 4/8DS-1, or DS3 and are frequency independent so that they can be used with any ODU of like capacity. – – – – – – –

Minimal Installation time Single coaxial cable connection between IDU and ODU Dual polarity DC input of (±21.6 to ±60 VDC) Adjustable transmit output power Frequency/channel setting via keypad or laptop PC Diagnostic loopbacks accessible via laptop PC Capacity to store 25 different channel plans

ODU functional modules

Link Block Diagram

Line Interfac e DEMUX

RX FPGA DEMUX Frame Frame Sync Private Link

TX MUX FPGA

DEMOD

TX IF PLL TX IF

310MHz

MOD

AGC

DEMOD Lock Low BER (>1e-9) AGC High BER (>1e-3) ODU Communication

Synth Up Conv. Osc Unlock Synth TX Offset Voltage Synth TX Main Loop Unlock Synth TX Offset Loop Unlock ALC

N le p rx o

LIU Input

MUX PLL

Near End RF Plug-in

N le p rx o

Near End SP

70MHz

DEMUX

MUX

DEMOD

PA

1778MH z

LNA

≈

RX Synth

Synth Up Conv. Osc Unlock Synth TX Offset Voltage Synth TX Main Loop Unlock 310MH Synth TX Offset Loop Unlock z

TX IF PLL TX IF

MOD

AGC

DEMOD Lock AGC RX FPGA Low BER (>1e-9) DEMUX Frame High BER (>1e-3) ODU Communication Frame Sync Private Link

ALC

N x le p ro

Line Interfac e

≈

Far End RF Plug-in

N le p rx o

LIU Input

PA

2158MH z IF LO RT 1848 PLL

Synth Rx Main Loop Unlock Synth Rx Offset Loop Unlock Synth Rx Offset Loop Voltage

Far End SP MUX PLL TX FPGA

TX Synth

70MH z

TX Synth

PA

2158MH z IF LO RT 1848 PLL 1778MH z

Synth Rx Main Loop Unlock Synth Rx Offset Loop Unlock Synth Rx Offset Loop Voltage

≈

PA

LNA

RX Synth

≈

Link Block Diagram

IDU-Indoor Unit

ODU Components

Signals on IF cable –IDU-ODU

Protection and Diversity Protection Schemes and Diversity Arrangements

Protection and Diversity The Need for Protection and Diversity 

In the past, short traffic interruptions without traffic disconnect in microwave links were often acceptable to many private users.



Expectations changed with the digital microwave transport of MSC-cell site data, ATM, high speed data transfer, teleconferencing, imaging (medical, etc.), and such technology as the new digital mobile trunking systems.



Excessive numbers of short fade hits (circuit interruptions) are now barely tolerable, except in LAN/IP transport and access (millimeterwave) hops impacted by rain cells, long-term outages (traffic disconnects) are usually unacceptable.

Protection Schemes



Equipment degradation, failure: – 1+1, hot-standby or on-line modules …HS – 1:N, one standby for >2 modules ……..HS



Antenna system misalignment, failure: – Split transmitters + RCS* ………….HS+ST – Two-dish hybrid diversity** ….HD, SD+ FD – Self-healing ring (loop) architecture …..SR

*Reverse Channel Switch command from far end receivers ** If FD is permitted 87

Protection Types



1+1 hot-standby protection …………………….HS



1+1 on-line (paralleled elements) protection ...HS



1:N module protection ………………………….HS



1:N multiline protection …………….HS or HS+FD



Split transmitters with RCS* ……….……...HS+ST



Self-healing ring (or loop) architecture …….….SR

*Reverse Channel Switch command triggered by the dual failure (outage) of both far-end receivers

Protected & Diversity - Dual Antenna

1+0 Equipment Protection - "1+1 HSB" Configuration f1 f1a

f1` f1b

Station A PR

Ch. 1 (STM-1) RPS

Station B f1a

f1a

PR

MD TX

RX DM

MD TX

RX DM

OP

f1a

PR

f1b

C B N

C B N

10dB

f1a

OP

f1b

PR

DM RX

TX

MD

DM RX

TX

MD

f1b

OP

OP

f1b

10dB

RPS

Ch. 1 (STM-1)

1+0 Equipment Protection - Space Diversity f1 f1a

f1` f1b

Station A PR

Station B f1a

f1a

CBN

MD TX MD TX Ch. 1 (STM-1) RPS

OP

f1a

PR

f1b

C B N

DM RX DM RX OP

f1b

CBN

PR

RX DM RX DM f1a

C B N

OP

f1b

PR

TX

MD

TX

MD

f1b

OP

RPS

Ch. 1 (STM-1)

Typical spacing for SD

Frequency (GHz)

Minimum Spacing (m)

Ideal Spacing (m)

6,8

4,5

10

7

4,5

10

13

2,5

5

15

2,0

5

Microwave Radio Technology - Space Diversity

∆

∆

MD STM-1

DM +

TX RX RX

CBN Main CBN Div

CBN Main CBN Div

TX RX RX

MD STM-1

+ DM Length compensation

SD +HSB

Block Diagram - 2+0 Configuration with XPIC horizontal f1a Ch. 1 (STM-1)

MD

H

TX

140 MHz

CBN

DM RX

V

f1b

f1b horizontal

f1 OP1 OP2 f1

TX

RX DM PW

f1a Ch. 2 (STM-1)

f1b 2 Waveguide pro Station

TX

140 MHz

Ch. 1 (STM-1)

f1a

PW

MD

140 MHz

CBN f

MD

TX

CBN

CBN

DM RX vertical f1b

MD

140 MHz

Ch. 2 (STM-1)

RX DM f1a vertical

H

V

H

V

Clock synchronization Data compensation

Microwave Radio Technology - Frequency Diversity

f f1

f3

f3a

MD TX MD TX Channel 1

RPS

f3b

f1a

DM RX DM RX f1b

CBN

f1 f1a

f3 f3a

f1’ f1b

f3’ f3b

Hot-Standby & Space Diversity Hot Standby Terminal

Hot Standby Terminal with Space Diversity Receivers

*

* Power splitters in digital radios are always asymmetrical, not 3/3 dB as in analog radios, as data are errorlessly switched - not combined as are analog radio basebands. A 3/3 dB RF receiver splitter provides no protection benefits over the 1/7 dB splitter, and will lower fade margins 2 dB for 58% more outage time.

Splitter/Combiners Waveguide Coupler

Primary Path Insertion Loss

Standby Pass Insertion Loss

6 dB unequal coupler

1.6 dB

6.4 dB

3 dB equal splitter

3.5 dB

3.5 dB

RFD Configurations

1+0

2+0

1+1 HH

1+1 HS

Hybrid module for NEC radios

Ring (Loop) Protection (SR) Benefits of Ring Protection  Cost-effective method of providing T1/E1 trunk redundancy in mixed radio, fiberoptics, span lines.  Protects against Path, Site, and Equipment Failures with non-protected radio repeaters - lowers costs ~40%.  Only protection from long-term periods of unavailability due to fiber cuts, power fades such as heavy rain at higher frequencies, infrastructure failures, etc.  Operation, fault location, testing, and maintenance are simplified.  A ring-closure microwave hop (perhaps longer or with degraded performance) or other T1/E1 trunk for ring closure (fiber, leased line) is necessary.

Component mountings- IF Module



The IF Module (IFM) consists of the following items:  TX IF assembly  RX IF assembly  DC-DC converter

dB

dB

2 * Syn

IF 2 * Syn

dB DC

dB

dB

High integrated RF Module

RF Diplexer

dB

CPU

DC

Modulare ODU-Design

Antenna

Some more configurations..  Operation mode 1+0 with integrated antenna

Frequencies 7 up to 38 GHz

In some cases of interest in an offer because of the lowest price IDU STM-1

EOW DPU

f1

Power Supply Modulator Demodulator

coax. cable

ODU

H OP

V

Broad Band Filter

Operation mode 1+0 with separate antenna IDU 155-16/128 LS STM-1

EOW DPU

Power Supply Modulator Demodulator

f1

coax. cable

wave guide

ODU Broad Band Filter

H OP

V

Frequencies 7 up to 38 GHz

Operation mode 1+1 HSB with integrated antenna Frequencies 7 up to 38 GHz Master-IDU EOW DPU

Power Supply Modulator Demodulator

coax. cable

f1

ODU

1,3 dB H BK

Slave-IDU EOW DPU

Power Supply Modulator Demodulator

Coupler

ODU

6,3 dB

V

Operation mode 1+1 HSB with integrated antenna Frequencies 7 up to 38 GHz Master-IDU EOW DPU

Power Supply Modulator Demodulator

coax. cable

f1

ODU

1,3 dB H BK

Slave-IDU EOW DPU

Power Supply Modulator Demodulator

Coupler

ODU

6,3 dB

V

Operation mode 4+0 or 2x(1+1) dual polarized CCDP with XPIC Frequencies 7 up to 38 GHz

4 x IDU 155-16/128 LS EOW

STM-1

DPU

Power Supply Modulator Demodulator

ODU f1

Waveguide

f3

H

EOW

STM-1

DPU

Power Supply Modulator

Coupler

ODU

OMT

OP1

OP2

OP3

OP4

f1

f3

V

Demodulator

ODU LX – Adjacent Channels ODU S – 1 Ch. to be left EOW

STM-1

DPU

Power Supply Modulator

ODU

Demodulator

Wave guide

EOW

STM-1

DPU

Power Supply Modulator Demodulator

Coupler

ODU

Operation mode 4+0, coupler version in dual polarized CAP 4 x IDU EOW

STM-1

DPU

Power Supply Modulator Demodulator

Frequencies 7 up to 38 GHz ODU f3

f1

Waveguide H

OP2

OP1

EOW

STM-1

DPU

EOW

STM-1

DPU

Power Supply Modulator

Coupler

ODU

OMT

STM-1

DPU

OP4

f2

f4

V

Demodulator

Power Supply Modulator Demodulator

ODU Wave guide

EOW

OP3

Power Supply Modulator Demodulator

Coupler

ODU

Frequency Patterns - Transmission via 2 Polarizations Orthomode transducer (OMT) f1a

V: vertical

 1.TX Polarization f1 MD

90°

CBN

DM RX f1b

H horizontal

f1a

 2.TX Polarization f1 MD CBN

DM RX

Waveguide H H

f1b Waveguide V

H

V

V

Operational parameters and system planning

    

Microwave Frequency Required Necessary Antenna Gain Maximum Distance between terminals Receive Signal Level Margin Link availability

Understanding operating parameters

Understanding operating parameters

Understanding Threshold for receivers

Terms of Microwave Radio Technology - System Overview

TX

CBN waveguide

CBN waveguide

Output power

Max. power e.g. +31 dBm [1.25 W]

RX

Input power System attenuation (e.g. 71.7 dB)

Antenna CBN waveguide gain e.g. e.g. 41.4 dB 5.3 dB

Antenna CBN Free space attenuation e.g. 143.9 dB gain waveguide (Distance d = 50 km) e.g. e.g. (Frequency: f = 7.5 GHz) 41.4 dB 5.3 dB

System gain

Fading margin

a = 92.4 + 20 ⋅ log( d[km]⋅ f[GHz]) 0

min. power e.g. -73 dBm [50 pW]

System Gain, Net Path Loss EIRP = P0 - Lf + Ga (FCC/ETSI Constraints) Ga FREE SPACE LOSS (NO FADE)

Lf

Transmitter Output Interface

P0 3

2

1

Repeater Station

NET PATH LOSS (NPL) SYSTEM GAIN (to 10-3 BER or Top of LOF) Bay Antenna Port

RSL IN 1

Top of Bay Antenna Port

SYSTEM GAIN. dB

NPL - NET PATH LOSS. dB

XMTR Power Out - RCVR RSL In (for 10-3 BER) at the Antenna Ports. Typically 100 dB

Waveguide In Site A to Waveguide Out at Site B. Typically 60 dB (Excluding Fade Activity)

2

3

Receiver Input Interface

Terminal Station RECEIVER RSL INPUT. dB RSL = XMTR Power Out - NPL THERMAL FADE MARGIN. dB TFM = System Gain - NPL

Receive signal level calculation RSL(dBm) = Tx power(dBm) + Tx antenna gain(dBi) Free Space Loss(dB) – Branching Loss – Feeder cable loss + Rcv antenna gain (dBi) where Free Space Loss(dB) = 32.4 + 20logF +20logD For example: where: DPath is Kms, Given: Distance F of is 10MHz Kms, Radio Frequency is 7 GHz, Tx Power is 20 dBm, dBi

and

Antenna Gain(both sides) is 38

•Free Space Loss = 32.4+20log(10)+20log(7000) = 32.4+20+76.90 = 129.30 dB •RSL(dBm) = 20 dBm + 38 dBi – 129.3 dB + 38 dBi = - 33.3 dBm

Receive signal level margin

• Directly determines the availability of the link by providing threshold “cushion” against signal fade due to environmental conditions, i.e. rain, snow, hail, etc. • Rain data for geographic location is needed to calculate availability once RSL margin is known.

Technology Technical Topics that define Digital Radio Hops            

System Gain, Net Path Loss RF Signal, Noise, and Interference Levels Static and Dynamic Thresholds Microwave Spectral Efficiency QAM, QPSK Modulation DSSS, OFDM/COFDM Signal Spreading Microwave Spectrum Calculations Co-Channel Dual Polarization (CCDP) Latency ATPC and DTPC Frequency Bands, Interference, Terrain Scatter Frequency Band Selection

ATPC and DTPC DTPC – Dynamic Transmit Power Control (TRuepoint, Galaxy 23) ATPC – Automatic Transmit Power Control (all other radios) ATPC or DTPC, features that reduce transmit powers except with farend receiver alarms during deep fades, are occasionally assigned to some microwave links for one of the following reasons:  Prevents receiver front-end overload in higher frequency links assigned high rain fade margins  Complies with FCC (and other) EIRP constraints in short hops,