otf100001 digital microwave communication principle issue 1.01

5/28/2018 OTF100001 Digital Microwave Communication Principle ISSUE 1.01

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Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved.

Digital MicrowaveCommunication

Principle


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Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved. Page1

Foreword

This course is developed for the requirement from OptiX RTN

equipments.

This course mainly introduce the basic knowledge of digital

microwave communication. Engineers can have a basic to

understand the further OptiX RTN equipments after finish the

course.


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Learning Guide

Before this course, you may refer to these references first:

SDH Principle

Network Communication Technology

Electromagnetism Basics


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Objectives

Upon completion of this course, you will be able to:

Describe the concept and characters of digital microwave

communication

Describe the theory and function of every parts in the digital

microwave system

List the networking application for digital microwave

systems

List the fadings in microwave propagation

List the common technologies of antifading


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Contents

1. Digital Microwave Communication Overview

2. Digital Microwave Equipment Introduction

3. Networking and Application of Digital Microwave

Equipment

4. Microwave Propagation and Antifading Technologies


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Transmission Method for Communication

Fiber

Microwave

Satellite

MUX MUX

RadioTer.

RadioTer.

Coaxial Cable


7/75Copyright 2006 Huawei Technologies Co., Ltd. All rights reserved. Page6

Fiber and Microwave transmission

Easy to cross the space, few land

needed, avoid the private land

Optical cable construction,

large land used.

Microwave (MW) Optical Fiber

Low investment, short period,

easy to maintain

High investment, long

Construction period

Anti-natural disaster strongly ,

easy to be restored fast

Outside cable maintenance,

natural disaster influence

Need to apply the frequency

licenseNo frequency license required

Performance affected by weather

and landform

Performance stable, less

influence from outside

Low transmission capacity High transmission capacity



Microwave (MW) Definition

Microwave (MW)

A kind of electromagnetic wave.

Radio frequency range is from 300MHz to 300GHz.

Be regard as plane wave.

The electric field and magnetic field exist at vertical of

transmission direction of plane wave. So it is called as

Transverse Electric and Magnetic field wave (TEM).



Digital MW communication concepts

The communication that use microwave as carrier is

microwave communication.

The microwave communication with digital baseband signal

is Digital microwave communication.

There is an intermediate frequency between digital

baseband signal and radio frequency signal.



Developing of MW communication

Note: capacity less than 10M is considered as low capacity, from

10~100M is medium capacity, and more than 100M is large capacity.

155M

34/140M

2/4/6/8M

480 tone

channels

SDH Digital

MW system

PDH Digital

MW System

Medium, low

capacity Digital

MW System

Analog MW

System

Capacity/ch

1950s

1970s

1980s

1990s to now



Frequency Band and Radio

Channel The common frequency bands :

7G/8G/11G/13G/15G/18G/23G/26G/32G/38G (by ITU-R rec. )

85432 10 201 30 40 50

1.5 2.5GH

zregion

networks

long-distance

backbone networkarea and local network,

boundary network

2834

Mbit/

s28

34

140155Mbit/

s

3.3 11 GHz

GH

z

34140155

Mbit/s


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Channel (cont.) The central frequency, T/R spacing and channel spacing are

defined in every frequency band.

f0(central freq.)

Frequency scope

Channe

l

spacingf1 f2 fn f1 f2

fn

Chann

el

spacing

T/R

spacing T/R spacing

Low frequency bandHigh frequency

band

Protection

spacing

Adjacent

T/R

spacing

Protection

spacing


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Channel (cont.)

f0(7575M)

Frequency scope74257725MHz

28M

f1=7442 f

5

f1

=7596 f2

f5

T/Rspacing:

154M

f2

=7470

Freq. scope F0 (MHz) T/R spacing (MHz)channel spacing(MHz)High site / low site

7425--7725 7575 154 28 Fn , Fn

7575 161 7

7110--7750 7275 196 287597 196 28

7250--7550 7400 161 3.5

.


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Modulation modes for Digital MW

The microwave carrier is digital modulated by the baseband

signal.

Digital base band signalIntermedia frequency

(IF) signal

Base band

Signal

rate

Channel

bandwidthmodulation

Servicesignal


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Modulation modes for Digital MW

(cont.) The frequency carrier signal can be described as:

Amplitude Shift Keying (ASK): A is variable, Wc and are constant

Frequency Shift Keying (FSK): Wc is variable, A and are constant

Phase Shift Keying (PSK): is variable, A and Wc are constant

Quadrature Amplitude Modulation (QAM): A and are variable, Wc isconstant

A*COSWc*t+Amplitude Frequenc

yPhas

e

PSK and QAM

are commonly

used in digital

MW


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MW Frame Structure

Radio frame complementary overhead (RFCOH):

RFCOH

ATPC

64Kb/s

DMY

64Kb/s

MLCM

11.84Mb/s

RSC

864Kb/s

WS

2.24Mb/s

XPIC

16Kb/s

ID

32Kb/s

INI

144Kb/s

FA

288Kb/s

15.552Mb/s

SOH Payload

STM-1 155.52Mb/s

171.072Mb/s

RSCMW service controlMLCM: Multi-level coded modulation IN: N:1 switch instructionDMY: Dummy ID:

Identification

XPIC: Cross polarization interference counteract FA: Frame

synchronizationATPC: Automatic transmitter power control WSWayside services


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MW Frame Structure (cont.)

RFCOH and STM-1 data are blocked by multi-frame, there are sixrows in a multi-frame, 3564 bits per rows. A multi-frame consistsof two sub-frames, and 1776 bits for one row in a sub-frame. Theother 12 bits are used as FS.

Multi-frame 3564bit

Sub-frame 2

1776bit148 units

FS

6bit

Sub-frame 1

1776bit148 units

FS

6bit6rows

C1IIC1IIC1IIC1II

C2IIbIIIIIIII

IIIIIIIIIIII

IIIIIIIIIIII

IIIIIIIIIIII

IIIIIIIIIIII

C1IIC1IIC1IIC1II

C2IIbIIaIIIII

IIIIIIIIIIII

IIIIIIIIIIII

IIIIIIIIIIII

IIIIIIIIIIII

12bit first unit 12bit 148thunit

ISTM-1 date bit C1,C2:2 Level error correction monitor bit FS:Frame sync. a,b:

other RFCOH


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Questions

What is microwave? What is digital microwave communication

What are the frequency bands commonly used in digital MW?

What are the concepts in digital MW frequency band arrangement ?

What modulation modes is commonly used? What modulation

modes are used in digital MW?


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Contents




Equipment



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Types of Digital MW Equipment

Digital MW

PDH SDH

split-mount MW

Trunk MW

All-outdoor MW

medium, low

capacity216E1

34M

Large capacity

STM-0STM-12 x STM-1 Discontinued

Analog MWModes

Capacity

Structure

Multiplexing


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Trunk MW Equipment

SDH MW Equipment

BRU: Branch of RF unit

MSTU: Main signal transceiver

unit (transceiver, modem, SDH

electric interface, hitless module)

SCSU: surveil, control, switch unit

BBIU: baseband interface unit(optional: STM-1 optical interface,

C4 PDH interface)

P

M1

M2


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All-outdoor MW Equipment

All-outdoor MW equipment

IF and baseband signal

processing unit

IF cable

RF signal processing unit

Service and power cable


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Split-mount MW Equipment

split-mount MW equipment

Antenna

RF unit or Outdoor unit(ODU)

IF Cable

Indoor Unit


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Split-mount MW Equipment (cont.)

Antenna: focus RF signal sent by ODU, enlarge

signal gain

ODU: RF signal processingconversion between IF

signal and RF signal.

IF cable: Transmission for IF service signal , ODU

management signal and supply power for ODU.

IDU: service access and distribute, multiple, modem

and so on.


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Split-mount MW Equipment -

Installation

Antenna

(ODU) IF cable

Separate installation

Soft

waveguide

IDU IF interface

Antenna

ODU

IDU

Direct installation

IF cable

IF interface


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Antenna

The antenna propagates the electric wave from transmitter

into one direction, and receive the electric wave. Paraboloid

antenna and Kasai Green antenna are usually used.

The common diameter of antenna are: 0.3, 0.6, 1.2, 1.8, 2.4, and

3.0m, etc.

Paraboloid antenna Kasai Green antenna


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Antenna (cont.)

Several channels in one frequency band can share

one antenna.

Tx

Rx

Tx

Rx

Channel Channel

1

1

n

n

1

1

n

n


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Antenna Aligning

Side viewSide

lobe

Rear lobe

Top view

Rear lobe

Side

lobe

Main lobe

Main lobe


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Antenna Aligning

CorrectWrongWrong


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Antenna Specifications

Antenna gain

The input power ratio of isotropic antenna (Pio) to surface

antenna (Pi) when getting the same electric field intensity

at the same point.

It can be calculated by formula( unit: dB) :

Half power angle (3 dB beam width)

From the main lobe deviates to both sides, the points

where the power decrease half are half power point. The

angle between the two half power points is half power

angle.

Approximate calculation formula

is:

2D

P

PG

i

io

D

)70~65( 005.0 Half power angle


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Antenna Specifications (cont.)

Cross polarization discrimination (XPD)

The suppressive intensity of power received from expected

polarization (Po) to the other polarization (Px). It should more than

30db. Formula is:

XdB10lgPo/Px

Antenna protection ratio

It is the ratio of the receiving attenuation in antenna other lobes to

the receiving attenuation in antenna main lobe. The 180 degree

antenna protection ratio also be called as the front / rear protection

ratio.


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Outdoor Unit

The main specifications of transmitter

Working frequency band:

One ODU can cover one frequency band or some part of a

frequency band.

Output power:

The power at the output port of transmitter.

The typical range of power is from 15 to 30 dBm.


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Outdoor Unit (cont.)

The main specifications of transmitter (cont.)

Frequency stability

The oscillation frequency stability of microwave device is from 3

to 10 ppm.

Transmitting frequency spectrum frame

A restricted frequency scope is frequency spectrum frame.


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The main specifications of receiver

Work frequency band:

The receiving frequency of local station is the same with the

remote station.

Frequency stability

The requirement is from 3 to 10ppm.

Noise Figure

The noise figure of digital microwave receiver is from 2.5 to

5dB.


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The main specifications of receiver (cont.)

Passband

The typical value is 1 to 2 times of transmission code element

rate. Selectivity

The suppressing ability against interference beyond transmission

bands

Automatic gain control (AGC) range Automatic control the gain to keep the same IF output power

level when receiving RF power level shift in a range because of

fading.


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Indoor Unit

Accessing service like E1 or STM-1

Processing RFCOH

Conversion signals between baseband and IF

Cableinte

rface

From/to

ODU

Tx IF

Rx IF

modulat

ion

demodul

ation

Multiplex of

microwave

frame

Demultiplex

of microwave

frame

Service

accessing

IF unitService

channel

Service

channelDC/DC convert

Monitor and

control unit

Interface

of OM


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Questions

What are the classification of digital MW equipment

What components are there in the split-mount digital MW

equipmentWhat are the functions of them?

What are the main parameters of antenna

What are the parameters of ODU transmitter and receiver


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Summary

Classification of digital microwave equipment

Functions of the components in split-mount digital MW

equipment

Parameters of antenna

Parameters of ODU

Function of IDU


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Contents




Equipment



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Common Networking Application

RingPoint to point

link

Add / drop

link

Tree


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Types of Digital MW Stations

The digital MW station includes terminal station, relaystation and pivotal station

Terminal

station

Terminal

station

Terminal

station

Pivotal

station

Pivotal

stationRelay

statio

n


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Types of Relay Stations

Relay

station

Active

Passive Parabolic reflectors

Plane reflector

Regenerative relay

IF relay

RF relay


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Active Relay Stations

RF direct station: Amplifying MW signal at RF band bidirectionally without

frequency shift.

Regenerative relay station:

It extends the MW propagation distance and change directionto round the obstacles.


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Passive Relay Stations

Parabolic reflectors: It consists of two parabolic antennas which are connected

back to back with a section of waveguide.

Plane reflectors:

A metal panel with a smooth surface and effective acreage.


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Passive Relay (actual picture)

Plane reflectors Parabolic reflectors


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Application of Digital MW

Supplement

for optical

network (the

last mile

access)Backhaul

transmission

for mobileBTS

Critical link

backupVIP customer

access

Emergency

communication

large activity,

crisis

Special

transmission

situation (river,

lake, island)Microwave

application


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Questions

Which network application are commonly used by digitalMW?

What types of stations are there in the digital MW system?

What types of the relay stations are there?

What are the applications for digital MW system?


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Contents




Equipment



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Contents


4.1 Microwave Propagation and fading

4.2 Antifading Technologies


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Factors Affect MW Propagation

Landform: The reflection from land affect receiving signal from main direction

4 types of the landform:

A: mountainous region (or the region of dense buildings) B: foothill (the fluctuation of ground is gently)

C: flatland

D: large acreage of water

Direct

Reflection

Direct

Reflection


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Factors Affect MW Propagation (cont.)

Atmosphere and weather:

Atmosphere absorption mainly affect the microwave whose

frequency is over 12 GHz.

Refraction, reflection, dispersion in the troposphere.

Scattering and absorption loss caused by rain, fog and snow.

It mainly affect the microwave whose frequency is over 10

GHz.


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Classification of the Fading

mechanism

Absorptionloss

Fading of rain and fog

Scintillation

fadingK facter fading

Duct Type fading

Sustained

duration

Received

levelEffect

Fast Fading

Slow Fading

Upward

Fading

Downward fading

Flat

fading

Frequency selective

fading

Fading in free

space

Fading


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Free Space Fading

Formula: A = 92.4 + 20 log d + 20 log f d = distance in km f = frequency in GHz

Power

Level

PTX= Output power

G = Antenna gain

A = Free space loss

M = Fading Margin

PTX

distance

GTX GRX

PRX

A

MReceiving threshold

G

d

G

f

PRX= Receiving

power


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Absorption Loss

It is mainly caused by atmosphere.


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Rain & Fog Fading

Generally, different frequency band has different loss.

less than 10 GHz, its fading caused by rain and fog is not

serious.

over 10 GHz, relay distance is limited by fading caused by

rains.

over 20GHz, the relay distance is only about several

kilometers for the rain & fog fading.


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K Factor Fading

A equivalent radius: Re=KR (R is the real radius of

earth).

the value of K is depend on the local meteorological

phenomena

Re

R


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Scintillation Fading

The particle cluster formed in local atmosphere forpressure, temperature or humidity is different as other area,

and the electric wave is scattered by it.

sketch map of Scintillation fading


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Duct Type Fading

When electric waves pass the atmospheric waveguide,super reflection occurs.

sketch map of Duct Type fading


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Multi-Path Propagation and Fading

The receiving paths

includes direct path and

other reflection paths.

Multi-path fading is caused

by the signals interference

from different propagationpaths

Ground


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Flat Fading

1 h

Receive

level in

free space

Threshol

d

(-30dB )

Signal

interruption

Upwardfading

Fast

fading Slow

fading


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Frequency Selective Fading

Freq. (MHz)

Receivingpower(dB

m)

Normal

Flat Selective fading

Frequency selective fading will cause the in-band distortionand decrease system original fading margin.


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Contents


4.1 Microwave Propagation and fading

4.2 Antifading Technologies


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Antifading Technologies

Types Improving effects

Antifading

technologies

related with

device

Adaptive Equalization Wave shape distortion

Cross Polarization Interference

Counteract

Wave shape distortion

Automatic Transmit PowerControl Power reduction

Forward Error Correct Power reduction

Antifading

technologies

related with

system

Diversity receive technologiesWave shape distortion

and Power reduction


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Adaptive Frequency Equalization

Signal

spectrumMulti-path fading

Slope

frequency

domain

equalization

Spectrum

after

equalization


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Adaptive Time Equalization

BeforeEqualizatio

n

T T T

After

Equalization

C-n C0 Cn

Ts-Ts-2Ts Ts-Ts-2Ts


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Automatic Transmit Power Control

ATPC is used to reduce interference to adjacent system,upward-fading, DC power consumption and refine characteristic

of residual error rate.

modulator transmitter

receiverdemodulato

r

ATPC

receiver

ATPC

transmitte

r

modulator

demodulator


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XPIC

XPIC is cross-polarization interference counteracter.

Direction ofelectric

field

Horizontal

polarization

Vertical

polarization

Frequency configuration in U6GHz bandITU-R F.384-5

30MH

z 80MHz

60MHz

340MHz

1 2 3 4 5 6 7 8

680MH

z

V (H)

H (V)

1 2 3 4 5 6 7 8

30MH

z80MHz

60MHz

340MH

z

680MHz

1 2 3 4 5 6 7 8

V (H)

H (V)

1X 2X 3X 4X 5X 6X 7X 8X

1 2 3 4 5 6 7 8

1X 2X 3X' 4X 5X 6X 7X 8X


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Diversity Reception

Diversity reception is used to minimize the effects of

fading. It includes:

Space diversity (SD)

Frequency diversity (FD)

Polarization diversity

Angle diversity


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Frequency Diversity

The merit is only need one set of feeder and antenna, butits demerit is that utilization of frequency band is low.

f1

f2


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Space Diversity

The merit is saving frequency resource, but demerit issystem is complex and need two or more sets of feeder

and antenna.

f1


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Other Antifading Methods

blocking the reflected wave by some terrain or obstacles.


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Other Antifading Methods (cont.)

Different height antennas in one hop.


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Questions

What are the factors which affect microwave propagation?

What types of the fading are there in microwave

propagation?

What types of antifading technologies can be used?


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Summary

Digital microwave communication definitions.

Frequency bands and radio channel arrangement

Structure and function of digital microwave equipment

Application of digital microwave communication

Microwave propagation and fading

Antifading technologies


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Thank youwww.huawei.com

otf100001 digital microwave communication principle issue 1.01

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