OTF000001 Digital Microwave Communication Principle ISSUE 1.01
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Transcript of OTF000001 Digital Microwave Communication Principle ISSUE 1.01
www.huawei.com
Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Digital Microwave Communication Principle
Page3Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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.
Page4Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Learning Guide
Before this course, you may refer to these references
first:
SDH Principle
Network Communication Technology
Electromagnetism Basics
Page5Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Objectives
Upon completion of this course, you will be able to: Describe the concept and characters of digital microwav
e communication Describe the theory and function of every parts in the digi
tal microwave system List the networking application for digital microwave sys
tems List the fadings in microwave propagation List the common technologies of antifading
Page6Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
Page7Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Transmission Methods for Communication
Fiber
Microwave
Satellite
MUX MUXRadioTer.
RadioTer.
Coaxial Cable
Page8Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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 license
No frequency license required
Performance affected by weatherand landform
Performance stable, less influence from outside
Low transmission capacity High transmission capacity
Page9Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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).
Page10Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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.
Page11Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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)
1950’s
1970’s
1980’s
1990’s to now
Page12Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
20
1 30
40
50
1.5
2.5GHzregion
networks
long-distance backbone network
area and local network, boundary
network
2834Mbit/
s28
34140155Mbit/s
3.3
11 GHz
GHz
34140155Mbit/s
Page13Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Frequency Band and Radio Channel (cont.) The central frequency, T/R spacing and channel spacing
are defined in every frequency band.
f0(central freq.)
Frequency scope
Channel spacing
f1 f2fn f1
’ f2’ fn
’
Channel spacing
T/R spacing T/R spacing
Low frequency band
High frequency band
Protectionspacing
Adjacent T/R
spacing
Protectionspacing
Page14Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Frequency Band and Radio Channel (cont.)
f0(7575M)Frequency scope ( 7425 - 7725MHz )
28M
f1=7442 f5 f1’=7596 f2
’ f5’
T/R spacing: 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 28
7597 196 28
7250--7550 7400 161 3.5
……. …… …… …… ……
Page15Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Modulation modes for Digital MW The microwave carrier is digital modulated by the
baseband signal.
Digital base band signalIntermedia frequency
(IF) signal
Base bandSignalrate
Channelbandwidth
modulation
Servicesignal
Page16Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Modulation modes for Digital MW (cont.) The frequency carrier signal can be described as:
Amplitude Shift Keying (ASK): A is variable, Wc and φ are constant Frequency Shift Keying (FSK): Wc is variable, A and φ are constant
Phase Shift Keying (PSK): φ is variable, A and Wc are constant Quadrature Amplitude Modulation (QAM): A and φ are variable, Wc
is constant
A*COS ( Wc*t+φ )
Amplitude Frequency
Phase
PSK and QAM are commonly used in digital
MW
Page17Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
MW Frame Structure
Radio frame complementary overhead (RFCOH):
RFCOH
ATPC64Kb/s
DMY64Kb/s
MLCM11.84Mb/
s
RSC864Kb/
s
WS2.24Mb/
s
XPIC16Kb/
s
ID32Kb/s
INI144Kb/
s
FA288Kb/
s
15.552Mb/s
SOH Payload
STM-1 155.52Mb/s
171.072Mb/s
RSC : MW service control MLCM: Multi-level coded modulation IN: N:1 switch instruction DMY: Dummy ID: Identification XPIC: Cross polarization interference counteract FA: Frame synchronization ATPC: Automatic transmitter power control WS : Wayside services
Page18Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
MW Frame Structure (cont.) RFCOH and STM-1 data are blocked by multi-frame, there
are six rows in a multi-frame, 3564 bits per rows. A multi-frame consists of two sub-frames, and 1776 bits for one row in a sub-frame. The other 12 bits are used as FS.
Multi-frame 3564bit
Sub-frame 2
1776bit ( 148 units )
FS
6bit
Sub-frame 1
1776bit ( 148 units )
FS
6bit
6rows
C1IIC1IIC1IIC1II
C2IIbIIIIIIII
IIIIIIIIIIII
IIIIIIIIIIII
IIIIIIIIIIII
IIIIIIIIIIII
C1IIC1IIC1IIC1II
C2IIbIIaIIIII
IIIIIIIIIIII
IIIIIIIIIIII
IIIIIIIIIIII
IIIIIIIIIIII
12bit first unit 12bit 148th unit
I : STM-1 date bit C1,C2: 2 Level error correction monitor bit FS: Frame sync. a,b: other RFCOH
Page19Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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?
Page20Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
Page21Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Types of Digital MW Equipment
Digital MW
PDH SDH
split-mount MW
Trunk MW
All-outdoor MW
medium, low capacity
( 2 ~ 16E1 ,34M )
Large capacity( STM-0 , STM-1 , 2 x STM-
1 )Discontinued
Analog MW
Modes
Capacity
Structure
Multiplexing
Page22Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
……
Page23Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
All-outdoor MW Equipment
All-outdoor MW equipment
IF and baseband signal processing unit
IF cable
RF signal processing unit
Service and power cable
Page24Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Split-mount MW Equipment
split-mount MW equipment
Antenna
RF unit or Outdoor unit(ODU)
IF Cable
Indoor Unit
Page25Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Split-mount MW Equipment (cont.)
Antenna: focus RF signal sent by ODU, enlarge signal gain
ODU: RF signal processing , conversion 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.
Page26Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Split-mount MW Equipment - Installation
Antenna
(ODU) IF cable
中频口
Separate installation
Soft waveguide
IDU IF interface
Antenna
ODU
IDU
Direct installation
IF cable
IF interface
Page27Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
Page28Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Antenna (cont.)
Several channels in one frequency band can share one antenna.
TxRx
TxRx
Channel
Channel
1
1
n
n
1
1
n
n
Page29Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Antenna Aligning
Side viewSide lobe
Rear lobe
Top viewRear lobe
Side lobe
Main lobe
Main lobe
Page30Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Antenna Aligning
CorrectWrongWrong
Page31Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
Page32Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Antenna Specifications (cont.)
Cross polarization discrimination (XPD) The suppressive intensity of power received from expected polari
zation (Po) to the other polarization (Px). It should more than 30db. Formula is:
XdB = 10lgPo/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.
Page33Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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.
Page34Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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.
Page35Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Outdoor Unit (cont.)
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.
Page36Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Outdoor Unit (cont.)
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.
Page37Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Indoor Unit
Accessing service like E1 or STM-1 Processing RFCOH Conversion signals between baseband and IF
Cab
le in
terfa
ce
From/to
ODU
Tx IF
Rx IF
modulation
demodulation
Multiplex of
microwave frame
Demultiplex of microwav
e frame
Service accessing
IF unitService channel
Service channe
l
DC/DC convert
Monitor and control unit
Interface of OM
Page38Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Questions
What are the classification of digital MW equipment ?
What components are there in the split-mount digital MW equipment ? What are the functions of them?
What are the main parameters of antenna ?
What are the parameters of ODU transmitter and receiver ?
Page39Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
Page40Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
Page41Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Common Networking Application
RingPoint to point
link
Add / drop link
Tree
Page42Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Types of Digital MW Stations
The digital MW station includes terminal station, relay station and pivotal station
Terminal station
Terminal station
Terminal station
Pivotal station
Pivotal station
Relay station
Page43Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Types of Relay Stations
Relay station
Active
Passive • Parabolic reflectors
• Plane reflector
• Regenerative relay
• IF relay
• RF relay
Page44Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
direction to round the obstacles.
Page45Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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.
Page46Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Passive Relay (actual picture)
Plane reflectors Parabolic reflectors
Page47Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Application of Digital MW
Supplement for optical network (the last
mile access)Backhaul
transmission for
mobile BTS
Critical link backup
VIP customer
access
Emergency communication( large activit
y, crisis )
Special transmission
situation (river, lake,
island)MicrowaveMicrowaveapplicatioapplicatio
nn
Page48Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Questions
Which network application are commonly used by digital MW?
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?
Page49Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
Page50Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Contents
4. Microwave Propagation and Antifading
Technologies
4.1 Microwave Propagation and fading
4.2 Antifading Technologies
Page51Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
Page52Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Factors Affect MW Propagation (cont.)
Atmosphere and weather:
Atmosphere absorption mainly affect the microwave whos
e frequency is over 12 GHz.
Refraction, reflection, dispersion in the troposphere.
Scattering and absorption loss caused by rain, fog and sno
w. It mainly affect the microwave whose frequency is over
10 GHz.
Page53Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Classification of the Fading
mechanism
Absorption loss
Fading of rain and fog
Scintillation fading
K facter fading
Duct Type fading
Sustained duration
Received level
Effect
Fast Fading
Slow Fading
Upward Fading
Downward fading
Flat fading
Frequency selective fading
Fading in free space
Fading
Page54Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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 gainA = Free space loss
M = Fading Margin
PTX
distance
GTX GRX
PRX
A
MReceiving threshold
G
d
G
f
PRX = Receiving power
Page55Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Absorption Loss
It is mainly caused by atmosphere.
Page56Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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.
Page57Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
Page58Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Scintillation Fading
The particle cluster formed in local atmosphere for pressure, temperature or humidity is different as other area, and the electric wave is scattered by it.
sketch map of Scintillation fading
Page59Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Duct Type Fading
When electric waves pass the atmospheric waveguide, super reflection occurs.
sketch map of Duct Type fading
Page60Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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 propagation
paths
Ground
Page61Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Flat Fading
1 h
Receive level in free space
Threshold (-30dB )
Signal interruption
Upward fading
Fast fading Slow
fading
Page62Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Frequency Selective Fading
Freq. (MHz)
Rece
ivin
g p
ow
er
(dB
m)
Normal
Flat Selective fading
Frequency selective fading will cause the in-band distortion and decrease system original fading margin.
Page63Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Contents
4. Microwave Propagation and Antifading
Technologies
4.1 Microwave Propagation and fading
4.2 Antifading Technologies
Page64Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Antifading Technologies
Types Improving effects
Antifading technologies related with
device
Adaptive EqualizationWave shape
distortion
Cross Polarization Interference Counteract
Wave shape distortion
Automatic Transmit Power Control
Power reduction
Forward Error Correct Power reduction
Antifading technologies related with
system
Diversity receive technologies
Wave shape distortion and Power
reduction
Page65Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Adaptive Frequency Equalization
Signal spectrum
Multi-path fading
Slope frequency domain
equalization
Spectrum after
equalization
Page66Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Adaptive Time Equalization
BeforeEqualization
… …T T T
AfterEqualization
C-n C0 Cn
Ts-Ts-2Ts Ts-Ts-2Ts
Page67Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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
receiverdemodulator
ATPC
receiver
ATPC
transmitter
modulator
demodulator
Page68Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
XPIC
XPIC is cross-polarization interference counteracter.
Direction of electric field
Horizontalpolarization
Verticalpolarization
Frequency configuration in U6GHz band ( ITU-R F.384-5 )
30MHz 80MHz
60MHz
340 MHz
1 2 3 4 5 6 7 8
680MHz
V (H)
H (V)
1’ 2’ 3’ 4’ 5’ 6’ 7’ 8’
30MHz
80MHz 60MHz
340MHz
680 MHz
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’
Page69Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Diversity Reception
Diversity reception is used to minimize the
effects of fading. It includes:
Space diversity (SD)
Frequency diversity (FD)
Polarization diversity
Angle diversity
Page70Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Frequency Diversity
The merit is only need one set of feeder and antenna, but its demerit is that utilization of frequency band is low.
f1
f2
Page71Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Space Diversity
The merit is saving frequency resource, but demerit is system is complex and need two or more sets of feeder and antenna.
f1
f1
Page72Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Other Antifading Methods
blocking the reflected wave by some terrain or obstacles.
Page73Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
Other Antifading Methods (cont.)
Different height antennas in one hop.
Page74Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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?
Page75Copyright © 2010 Huawei Technologies Co., Ltd. All rights reserved.
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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