Digital Microwave Communication Principles-A .ppt
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04/12/13
Digital Microwave Communication Principles www.huawei.com
HUAWEI TECHNOLOGIES CO., LTD.
Huawei Confidential
Foreword
This course is developed to meet the requirement of Huawei Optical Network RTN microwave products.
This course informs engineers of the basics on digital microwave communications, which will pave the way for learning the RTN series microwave products later.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 2
Objectives
After this course, you will be able to explain:
Concept and characteristics of digital microwave communications
Functions and principles of each component of digital microwave equipment
Common networking modes and application scenarios of digital microwave equipment
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 3
Contents 1.
Digital Microwave Communication Overview
2.
Digital Microwave Communication Equipment
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 4
Transmission Methods in Current Communications Networks Coaxial cable communication
Optical fiber communication
Microwave communication
Microwave TE
Microwave TE
MUX/DEMUX
MUX/DEMUX
Satellite communication
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 5
Definition of Microwave
Microwave
Microwave is a kind of electromagnetic wave. In a broad sense, the microwave frequency range is from 300 MHz to 300 GHz. But In microwave communication, the frequency range is generally from 3 GHz to 30 GHz.
According to the characteristics of microwave propagation, microwave can be considered as plane wave.
The plane wave has no electric field and magnetic field longitudinal components along the propagation direction. The electric field and magnetic field components are vertical to the propagation direction. Therefore, it is called transverse electromagnetic wave and TEM wave for short.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 6
Concept of Digital Microwave Communication
Digital microwave communication is a way of transmitting digital information in atmosphere through microwave or radio frequency (RF).
Microwave communication refers to the communication that use microwave as carrier .
Digital microwave communication refers to the microwave communication that adopts the digital modulation.
The baseband signal is modulated to intermediate frequency (IF) first . Then the intermediate frequency is converted into the microwave frequency.
The baseband signal can also be modulated directly to microwave frequency, but only phase shift keying (PSK) modulation method is applicable.
The electromagnetic field theory is the basis on which the microwave communication theory is developed.
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Page 7
Microwave Frequency Band Selection and RF Channel Configuration (1)
Generally-used frequency bands in digital microwave transmission:
7G/8G/11G/13G/15G/18G/23G/26G/32G/38G (defined by ITU-R Recommendations) 1.5 2.5 GHz GHz Regional network 3.3 GHz Long haul
trunk network
2/8/34 Mbit/s
11 GHz
Regional network, local network, and boundary network
34/140/155 Mbit/s 2/8/34/140/155 Mbit/s 1
2
3
4
5
8
1 0
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2 0
3 0
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GHz 4 0
5 0
Digital Microwave Communication Modulation (1) 英 Digital baseband signal is the unmodulated digital signal. The baseband
signal cannot be directly transmitted over microwave radio channels and must be converted into carrier signal for microwave transmission.
Channel bandwidth
Baseband signal rate
Digital baseband signal
Modulati on
IF signal
Service signal transmitted
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Page 9
Questions
What is microwave?
What is digital microwave communication?
What are the frequently used digital microwave frequency bands?
What are the frequently used modulation schemes? Which are the most frequently used modulation schemes?
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 10
Contents 1.
Digital Microwave Communication Overview
2.
Digital Microwave Communication Equipment
3.
Digital Microwave Networking and Application
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Page 11
Microwave Equipment Category Analog microwave
Digital microwave
System MUX/DEMU X Mode
PDH
SDH
Capacity
Small and medium capacity (2–16E1, 34M)
Large capacity (STM-0, STM-1, 2xSTM1) (Discontinued)
Trunk radio Structure
Split-mount radio All outdoor radio
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Page 12
Trunk Microwave Equipment • High cost, large transmission capacity, more stable performance, applicable to long haul and trunk transmission
MSTU: Main Signal Transmission Unit (transceiver, modem, SDH electrical interface, hitless switching)
P M1
SCSU: Supervision, Control and Switching Unit
M2 …
• RF, IF, signal processing, and MUX/DEMUX units are all indoor. Only the antenna system is outdoor.
BRU: Branch RF Unit
SDH microwave equipment
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
BBIU: Baseband Interface Unit (option) (STM-1 optical interface, C4 PDH interface)
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All Outdoor Microwave Equipment • All the units are outdoor.
RF processing unit
IF cable
• Installation is easy.
IF and baseband processing unit
• The equipment room can be saved.
Service and power cable
All outdoor microwave equipment
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Page 14
Split-Mount Microwave Equipment (1) The RF unit is an outdoor unit
(ODU). The IF, signal processing, and MUX/DEMUX units are
Antenna
integrated in the indoor unit (IDU). The ODU and IDU are
IF cable
connected through an IF cable.
The ODU can either be directly mounted onto the antenna or connected to the antenna
ODU (Outdoor Unit)
through a short soft waveguide.
IDU (Indoor Unit)
Although the capacity is smaller than the trunk, due to the easy installation and maintenance, fast network construction, it’s the most widely used microwave equipment.
Split-mount microwave equipment
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Page 15
Split-Mount Microwave Equipment (2)
Unit Functions
Antenna: Focuses the RF signals transmitted by ODUs and increases the signal gain.
ODU: RF processing, conversion of IF/RF signals.
IF cable: Transmitting of IF signal, management signal and power supply of ODU.
IDU: Performs access, dispatch, multiplex/demultiplex, and modulation/demodulation for services.
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Page 16
Split-Mount Microwave Equipment – Installation Direct Mount
Separate Mount
antenna (direct mount) antenna (separate mount)
ODU
Soft waveguide IF cable
IF cable
OD U
英英英 IDU
IF port
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IF port
IDU
Page 17
Microwave Antenna (1)
Parabolic antenna
Cassegrainian antenna
Antennas are used to send and receive microwave signals. Parabolic antennas and cassegrainian antennas are two common types of
microwave antennas. Microwave antenna diameters includes: 0.3m, 0.6m, 1.2m, 1.8m,2.0m, 2.4m, 3.0m, 3.2metc.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 18
Microwave Antenna (2) Different frequency channels in same frequency band can share one antenna.
T x R x T x R
Chann el 1
Chann el 1
1
1
n
n
n
n
x
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Page 19
Antenna Adjustment (1) Side lobe Half-power angle
Side view
Main lobe
Tail lobe
Side lobe Half-power angle
Top view
Main lobe
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Tail lobe
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Antenna Adjustment (2) During antenna adjustment, change the direction vertically or horizontally. Meanwhile, use a multimeter to test the RSSI at the receiving end. Usually, the voltage wave will be displayed as shown in the lower right corner. The peak point of the voltage wave indicates the main lobe position in the vertical or horizontal direction. Large-scope adjustment is unnecessary. Perform fine adjustment on the antenna to the peak voltage point.
When antennas are poorly aligned, a small voltage may be detected in one direction. In this case, perform coarse adjustment on the antennas at both ends, so that the antennas are roughly aligned.
VAGC
AGC Voltage detection point
Angle Side lobe position Main lobe position
The antennas at both ends that are well aligned face a little bit upward. Though 1–2 dB is lost, reflection interference will be avoided. Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 21
Antenna Adjustment (3)
During antenna adjustment, the
two wrong adjustment cases are show here. One antenna is aligned to another antenna through the side lobe. As a result, the RSSI cannot meet the requirements.
Wrong
Wrong
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Page 22
Correct
Split-Mount Microwave Equipment – ODU (2)
Specifications of Transmitter
Working frequency band
Generally, trunk radios use 6, 7, and 8 GHz frequency bands. 11, 13 GHz and higher frequency bands are used in the access layer (e.g. BTS access).
Output power
The power at the output port of a transmitter. Generally, the output power is 15 to 30 dBm.
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 23
Questio ns
What types are microwave equipment classified into?
What units do the split-mount microwave equipment have? And what are their functions??
How to adjust antennas?
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Page 24
Summary
Classification of digital microwave equipment
Components of split-mount microwave equipment and their functions
Antenna installation and key specifications of antennas
Functional modules and key performance indexes of ODU
Functional modules of IDU
Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved.
Page 25
Contents 1.
Digital Microwave Communication Overview
2.
Digital Microwave Communication Equipment
3.
Digital Microwave Networking and Application
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Page 26
Common Networking Modes of Digital Microwave Ring network
Chain network
Add/Drop network Hub network
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Page 27
Application of Digital Microwave
BTS backhaul transmission
Complementary networks to optical networks (access the services from the last 1 km) Special transmission conditions (rivers, lakes, islands, etc.) Microwave application
Redundancy backup of important links VIP customer access
Emergency communications (conventions, activities, danger elimination, disaster relief, etc.)
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Page 28
Questio ns
What are the networking modes frequently used for digital microwave?
What are the types of digital microwave stations?
What is the major application of digital microwave?
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Page 29
Protection Modes of Digital Microwave Equipment (1)
Hybrid coupler
With one hybrid coupler added between two ODUs and the antenna, the 1+1 HSB can be realized in the configuration of one antenna. Moreover, the FD technology can also be adopted.
The 1+1 HSB can also be realized in the configuration of two antennas. In this case, the FD and SD technologies can both be adopted, which improves the system availability.
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Page 30
Protection Modes of Digital Microwave Equipment (2)
N+1 (N≤3, 7, 11) Protection In the following figure, Mn stands for the active channel and P stands for the standby channel. The active channel and the standby channel have their independent modulation/demodulation unit and signal transmitting /receiving unit.
When the fault or fading occurs in the active channel, the signal is switched to the standby channel. The channel backup is an inter-frequency backup. This protection mode (FD) is mainly used in the all indoor microwave equipment.
Products of different vendors support different specifications.
ch1 ch2 ch3
M1 M2
M1 M2
M3
M3
ch1 ch2 ch3
chP
P
P
chP
Switching control unit
RFSOH
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Switching control unit
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Protection Modes of Digital Microwave Equipment (3) Configurati on
Protection Mode
Remark s
Application Terminal of the network
1+0
NP
Non-protection
1+1
FD
Channel protection
1+1
SD
Equipment protection Intraand channel frequency protection
1+1
FD+SD
Equipment protection Interand channel frequency protection
N+1
FD
Equipment protection Interand channel frequency protection
Interfrequency
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Select the proper mode depending on the geographical condition and requirements of the customer
Large-capacity backbone network
Page 32
Questions
What protection modes are available for the microwave?
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Page 33
Thank you www.huawei.com
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