Digital Microwave Communication Principles-A .ppt

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Digital Microwave Communication

Principles

Page 2Copyright © 2006 Huawei Technologies Co., Ltd. All rights reserved. Page 2Page 2

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.


ObjectivesObjectives

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


Contents

1. Digital Microwave Communication Overview

2. Digital Microwave Communication Equipment


Transmission Methods in Current Communications Networks

Optical fiber communication

Microwave communication

Satellite communication

MUX/DEMUX MUX/DEMUX

Micro

wave T

E

Micro

wave T

E

Coaxial cable communication


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.


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.


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)

85432 10

20

1 30

40

50

1.5 GHz

2.5 GHz

Long haul trunk

network2/8/34 Mbit/s

11 GHz

GHz

34/140/155 Mbit/s

2/8/34/140/155 Mbit/s

3.3 GHz

Regional network

Regional network, local network, and boundary

network


Digital Microwave Communication Modulation (1)

　 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.

Digital baseband signal IF signal

Base

band sig

nal

rate

Channel b

andw

idth

Modulation

Service signal

transmitted


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?


Contents



3. Digital Microwave Networking and Application


Microwave Equipment Category

System Digital microwave

PDH SDH

Split-mount radio

Trunk radio

All outdoor radio

Small and medium capacity (2–16E1,

34M)

Large capacity (STM-0, STM-1, 2xSTM-

1)Capacity

Structure

(Discontinued)

Analog microwave

MUX/DEMUX Mode


Trunk Microwave Equipment

• High cost, large transmission capacity, more stable performance, applicable to long haul and trunk transmission

• RF, IF, signal processing, and MUX/DEMUX units are all indoor. Only the antenna system is outdoor.

SDH microwave equipment

BRU: Branch RF Unit

MSTU: Main Signal Transmission Unit (transceiver, modem, SDH electrical interface, hitless switching)

SCSU: Supervision, Control and Switching Unit

BBIU: Baseband Interface Unit (option) (STM-1 optical interface, C4 PDH interface)

P

M1

M2

……


All Outdoor Microwave Equipment

• All the units are outdoor.

• Installation is easy.

• The equipment room can be saved.

All outdoor microwave equipment

IF and baseband processing unit

IF cable

RF processing unit

Service and power cable


Split-Mount Microwave Equipment (1) The RF unit is an outdoor unit

(ODU). The IF, signal processing,

and MUX/DEMUX units are

integrated in the indoor unit

(IDU). The ODU and IDU are

connected through an IF cable.

The ODU can either be directly

mounted onto the antenna or

connected to the antenna

through a short soft waveguide.

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

Antenna

ODU (Outdoor

Unit)

IF cable

IDU (Indoor Unit)


Split-Mount Microwave Equipment (2)

Unit Functions

Antenna: Focuses the RF signals transmitted by ODUs and increases the signal g

ain.

ODU: RF processing, conversion of IF/RF signals.

IF cable: Transmitting of IF signal, management signal and power supply of OD

U.

IDU: Performs access, dispatch, multiplex/demultiplex, and modulation/demod

ulation for services.


Split-Mount Microwave Equipment – Installation

antenna (separate mount)

ODU

IF cable

中频口

Separate Mount

Soft waveguide

IDU IF port

antenna (direct mount)

ODU

IDU

Direct Mount

IF cable

IF port


Microwave Antenna (1)

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.

Parabolic antenna Cassegrainian antenna


Different frequency channels in same frequency band can share one antenna.

Microwave Antenna (2)

TxRx

TxRx

Channel

Channel

1

1

n

n

1

1

n

n


Antenna Adjustment (1)

Side view Side lobe

Main lobeHalf-power angle Tail lobe

Top view

Main lobe

Side lobe

Half-power angle Tail lobe


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.

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.

Antenna Adjustment (2)Antenna Adjustment (2)

Side lobe position

AGCVoltage

detection point

VAGC

Main lobe position

Angle


Antenna Adjustment (3)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.

CorrectWrongWrong


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.

Split-Mount Microwave Equipment – ODU (2)


Questions

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?


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


Contents



3. Digital Microwave Networking and Application


Common Networking Modes of Digital Microwave

Ring network Chain network

Add/Drop network

Hub network


Application of Digital Microwave

Complementary networks to optical networks (access the services from

the last 1 km)

BTS backhaul transmission

Redundancy backup of

important links

VIP customer access

Emergency communications

(conventions, activities, danger

elimination, disaster relief, etc.)

Special transmission conditions (rivers,

lakes, islands, etc.)

Microwave Microwave applicationapplication


Questions

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?


Protection Modes of Digital Microwave Equipment (1)

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.

Hybrid coupler


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.


Switching control unit

Switching control unitRFSOH

PP

MM11

MM22

MM33

PP

MM11

MM22

MM33

chch11

chch22

chchPP

chch33

chch11

chch22

chchPP

chch33



Configuration

Protection ModeRemark

sApplication

1+0 NP Non-protection Terminal of the network

1+1 FD Channel protection Inter-frequency Select the proper

mode depending on the geographical

condition and requirements of the

customer

1+1 SD Equipment protection and channel protection

Intra-frequency

1+1 FD+SD Equipment protection and channel protection

Inter-frequency

N+1 FD Equipment protection and channel protection

Inter-frequency

Large-capacity backbone network


Questions

What protection modes are available for the microwave?

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Digital Microwave Communication Principles-A .ppt

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