BTS 3012

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle Contents

Issue 03 (2006-11-16) Huawei Technologies Proprietary i

Contents

1 System Architecture...................................................................................................................1-1 1.1 Hardware Architecture ..................................................................................................................................1-2

1.1.1 Composition.........................................................................................................................................1-2 1.1.2 Cabinet .................................................................................................................................................1-2 1.1.3 Antenna Subsystem..............................................................................................................................1-6 1.1.4 O&M Subsystem..................................................................................................................................1-6

1.2 Software Architecture....................................................................................................................................1-7 1.2.1 Composition.........................................................................................................................................1-7 1.2.2 Signaling Processing Software.............................................................................................................1-8 1.2.3 Baseband Signal Processing Software .................................................................................................1-8 1.2.4 O&M and Transmission Device Control Software ..............................................................................1-8

1.3 Logical Architecture......................................................................................................................................1-9 1.3.1 Composition.........................................................................................................................................1-9 1.3.2 Common Subsystem ..........................................................................................................................1-10 1.3.3 DTRU Subsystem ..............................................................................................................................1-11 1.3.4 DAFU Subsystem ..............................................................................................................................1-11 1.3.5 Antenna Subsystem............................................................................................................................1-11

1.4 Bus Structure...............................................................................................................................................1-12

2 Common Subsystem..................................................................................................................2-1 2.1 Composition ..................................................................................................................................................2-2

2.1.1 BTS Common Subsystem ....................................................................................................................2-2 2.1.2 Cabinet Top Access Subsystem............................................................................................................2-2

2.2 Functions.......................................................................................................................................................2-3 2.3 DTMU...........................................................................................................................................................2-4

2.3.1 Introduction..........................................................................................................................................2-4 2.3.2 Working Environment..........................................................................................................................2-4 2.3.3 Functions and Principles ......................................................................................................................2-5

2.4 DCCU............................................................................................................................................................2-6 2.4.1 Introduction..........................................................................................................................................2-6 2.4.2 Working Environment..........................................................................................................................2-6 2.4.3 Functions and Principles ......................................................................................................................2-7

2.5 DCSU............................................................................................................................................................2-7

Contents HUAWEI BTS3012 Base Station

Technical Manual - Architecture and Principle

ii Huawei Technologies Proprietary Issue 03 (2006-11-16)


2.6 DEMU...........................................................................................................................................................2-8 2.6.1 Introduction..........................................................................................................................................2-8 2.6.2 Working Environment..........................................................................................................................2-9 2.6.3 Functions and Principles ......................................................................................................................2-9

2.7 DATU..........................................................................................................................................................2-10 2.7.1 Introduction........................................................................................................................................2-10 2.7.2 Working Environment........................................................................................................................2-10 2.7.3 Functions and Principles ....................................................................................................................2-10

2.8 DCMB.........................................................................................................................................................2-11 2.8.1 Introduction........................................................................................................................................2-11 2.8.2 Working Environment........................................................................................................................2-11 2.8.3 Functions and Principles ....................................................................................................................2-11

2.9 DELC ..........................................................................................................................................................2-11 2.9.1 Introduction........................................................................................................................................2-11 2.9.2 Working Environment........................................................................................................................2-12 2.9.3 Functions and Principles ....................................................................................................................2-12

2.10 DMLC .......................................................................................................................................................2-12 2.10.1 Introduction......................................................................................................................................2-12 2.10.2 Working Environment ......................................................................................................................2-12 2.10.3 Functions and Principles ..................................................................................................................2-13

2.11 DSAC ........................................................................................................................................................2-13 2.11.1 Introduction......................................................................................................................................2-13 2.11.2 Working Environment ......................................................................................................................2-14 2.11.3 Functions and Principles ..................................................................................................................2-14

2.12 DCTB........................................................................................................................................................2-14 2.12.1 Introduction......................................................................................................................................2-14 2.12.2 Working Environment ......................................................................................................................2-15 2.12.3 Functions and Principles ..................................................................................................................2-15

3 DTRU Subsystem.......................................................................................................................3-1 3.1 Components...................................................................................................................................................3-2 3.2 Functions.......................................................................................................................................................3-2 3.3 DTRU............................................................................................................................................................3-3


3.4 DTRB............................................................................................................................................................3-4 3.4.1 Introduction..........................................................................................................................................3-4 3.4.2 Working Environment..........................................................................................................................3-4

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle Contents

Issue 03 (2006-11-16) Huawei Technologies Proprietary iii

3.4.3 Functions and Principles ......................................................................................................................3-5

4 DAFU Subsystem.......................................................................................................................4-1 4.1 Components...................................................................................................................................................4-2 4.2 Functions.......................................................................................................................................................4-2 4.3 DDPU............................................................................................................................................................4-3


4.4 DCOM...........................................................................................................................................................4-4 4.4.1 Introduction..........................................................................................................................................4-4 4.4.2 Working Environment..........................................................................................................................4-4 4.4.3 Functions and Principles ......................................................................................................................4-5

5 Antenna Subsystem...................................................................................................................5-1 5.1 Components...................................................................................................................................................5-2 5.2 Antenna .........................................................................................................................................................5-2

5.2.1 Working Principles...............................................................................................................................5-2 5.2.2 Types ....................................................................................................................................................5-3 5.2.3 Specifications.......................................................................................................................................5-4 5.2.4 Functional Principles of the RET System ............................................................................................5-7 5.2.5 Diversity...............................................................................................................................................5-8

5.3 Feeder............................................................................................................................................................5-8 5.4 TMA..............................................................................................................................................................5-8

5.4.1 Features................................................................................................................................................5-8 5.4.2 Working Principles...............................................................................................................................5-9

6 O&M Subsystem........................................................................................................................6-1 6.1 Introduction...................................................................................................................................................6-2 6.2 Hardware Structure .......................................................................................................................................6-2 6.3 Software Structure.........................................................................................................................................6-3 6.4 Functions.......................................................................................................................................................6-3

7 System Signal Procedure ..........................................................................................................7-1 7.1 DL Signal Flow .............................................................................................................................................7-2 7.2 UL Signal Flow .............................................................................................................................................7-2 7.3 Signaling Processing Flow............................................................................................................................7-3 7.4 Clock Signal Flow.........................................................................................................................................7-4 7.5 Combined Cabinet Signal Flow ....................................................................................................................7-5

8 Configuration and Networking...............................................................................................8-1 8.1 Configuration of the BTS3012......................................................................................................................8-2

8.1.1 Configuration Principles ......................................................................................................................8-2 8.1.2 Configuration Features.........................................................................................................................8-2 8.1.3 System Capacity...................................................................................................................................8-3

Contents HUAWEI BTS3012 Base Station


iv Huawei Technologies Proprietary Issue 03 (2006-11-16)

8.2 Board Configuration......................................................................................................................................8-3 8.2.1 DTRU...................................................................................................................................................8-3 8.2.2 DAFU...................................................................................................................................................8-3 8.2.3 DTMU..................................................................................................................................................8-4 8.2.4 DCCU ..................................................................................................................................................8-4 8.2.5 DCSU...................................................................................................................................................8-4 8.2.6 DEMU..................................................................................................................................................8-4 8.2.7 DATU...................................................................................................................................................8-4 8.2.8 NFCB...................................................................................................................................................8-4 8.2.9 DMLC..................................................................................................................................................8-5 8.2.10 DELC.................................................................................................................................................8-5 8.2.11 DSAC.................................................................................................................................................8-5

8.3 Typical Configuration....................................................................................................................................8-5 8.3.1 S4/4/4 ...................................................................................................................................................8-5 8.3.2 O6 ........................................................................................................................................................8-6

8.4 Networking Types .........................................................................................................................................8-7 8.4.1 Transmission Mode..............................................................................................................................8-8 8.4.2 Networking Modes...............................................................................................................................8-8 8.4.3 Principles of Networking .....................................................................................................................8-8 8.4.4 Star Networking ...................................................................................................................................8-8 8.4.5 Chain Networking................................................................................................................................8-9 8.4.6 Tree Networking ..................................................................................................................................8-9 8.4.7 Ring Networking................................................................................................................................8-10

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle Figures

Issue 03 (2006-11-16) Huawei Technologies Proprietary v

Figures

Figure 1-1 Composition of the BTS3012 system ...............................................................................................1-2

Figure 1-2 BTS3012 cabinet under full configuration .......................................................................................1-4

Figure 1-3 Software architecture ........................................................................................................................1-8

Figure 1-4 Logical architecture of the BTS3012..............................................................................................1-10

Figure 2-1 Boards in the BTS3012 common subsystem ....................................................................................2-2

Figure 2-2 Boards in the BTS3012 cabinet top access subsystem......................................................................2-3

Figure 2-3 DTMU working environment ...........................................................................................................2-5

Figure 2-4 DTMU structure................................................................................................................................2-5

Figure 2-5 DCCU working environment............................................................................................................2-6

Figure 2-6 DCCU structure ................................................................................................................................2-7

Figure 2-7 DCSU working environment ............................................................................................................2-8

Figure 2-8 DCSU structure.................................................................................................................................2-8

Figure 2-9 DEMU working environment ...........................................................................................................2-9

Figure 2-10 DEMU structure..............................................................................................................................2-9

Figure 2-11 DATU working environment ........................................................................................................2-10

Figure 2-12 DATU structure.............................................................................................................................2-10

Figure 2-13 DCMB working environment .......................................................................................................2-11

Figure 2-14 DELC working environment ........................................................................................................2-12

Figure 2-15 DELC structure.............................................................................................................................2-12

Figure 2-16 DMLC working environment .......................................................................................................2-13

Figure 2-17 DMLC structure............................................................................................................................2-13

Figure 2-18 DSAC working environment ........................................................................................................2-14

Figure 2-19 DSAC structure.............................................................................................................................2-14

Figure 2-20 DCTB working environment ........................................................................................................2-15

Figure 2-21 DCTB structure.............................................................................................................................2-15

Figure 3-1 DTRU subsystem under full configuration.......................................................................................3-2

Figures HUAWEI BTS3012 Base Station


vi Huawei Technologies Proprietary Issue 03 (2006-11-16)

Figure 3-2 DTRU working environment ............................................................................................................3-3

Figure 3-3 Function structure of the DTRU .......................................................................................................3-4

Figure 3-4 DTRB working environment ............................................................................................................3-5

Figure 3-5 Functional structure of the DTRB ....................................................................................................3-5

Figure 4-1 DAFU subsystem under full configuration.......................................................................................4-2

Figure 4-2 Logical location of the DAFU subsystem.........................................................................................4-2

Figure 4-3 DDPU working environment ............................................................................................................4-3

Figure 4-4 Functional structure of the DDPU ....................................................................................................4-4

Figure 4-5 DCOM working environment ...........................................................................................................4-5

Figure 4-6 Functional structure of the DCOM ...................................................................................................4-5

Figure 5-1 Antenna subsystem ...........................................................................................................................5-2

Figure 5-2 Antenna composition ........................................................................................................................5-3

Figure 5-3 Types of antenna ...............................................................................................................................5-4

Figure 5-4 Horizontal radiation pattern ..............................................................................................................5-5

Figure 5-5 Vertical radiation pattern...................................................................................................................5-6

Figure 5-6 Functional structure of the RET........................................................................................................5-7

Figure 5-7 Functional structure of the TMA ......................................................................................................5-9

Figure 6-1 Hardware structure of the BTS3012 O&M subsystem .....................................................................6-2

Figure 6-2 Software structure of the BTS3012 O&M subsystem.......................................................................6-3

Figure 7-1 DL signal flow ..................................................................................................................................7-2

Figure 7-2 UL signal flow ..................................................................................................................................7-3

Figure 7-3 Signaling processing flow.................................................................................................................7-4

Figure 7-4 Clock signal flow..............................................................................................................................7-4

Figure 7-5 Combined cabinet signal flow ..........................................................................................................7-5

Figure 8-1 Cabinet configuration in an S4/4/4 site.............................................................................................8-6

Figure 8-2 O6 cabinet configuration ..................................................................................................................8-7

Figure 8-3 Star networking.................................................................................................................................8-8

Figure 8-4 Chain networking..............................................................................................................................8-9

Figure 8-5 Tree networking..............................................................................................................................8-10

Figure 8-6 Ring networking .............................................................................................................................8-11

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle Tables

Issue 03 (2006-11-16) Huawei Technologies Proprietary vii

Tables

Table 2-1 Mapping between the boards and the slot numbers in the common subsystem..................................2-2

Table 2-2 Mapping between the boards and the slot numbers in the cabinet top access subsystem...................2-3

Table 6-1 Functions of the BTS3012 O&M subsystem......................................................................................6-3

Table 8-1 Configuration principles .....................................................................................................................8-2

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle 1 System Architecture

Issue 03 (2006-11-16) Huawei Technologies Proprietary 1-1

1 System Architecture

About This Chapter

The following table lists the contents of this chapter.

Title Description

1.1 Hardware Architecture Describes the architecture of the BTS3012 hardware.

1.2 Software Architecture Describes the architecture of the BTS3012 software.

1.3 Logical Architecture Describes the logical architecture of the BTS3012 including its compositions and the subsystems.

1.4 Bus Structure Describes four types of buses in the BTS3012.

1 System Architecture HUAWEI BTS3012 Base Station


1-2 Huawei Technologies Proprietary Issue 03 (2006-11-16)

1.1 Hardware Architecture This section describes the BTS3012 hardware architecture.

It has the following sections:

Composition Cabinet

1.1.1 Composition Figure 1-1 shows the BTS3012 system and its relation with other relevant devices, such as the Base Station Controller (BSC) and the Operation and Maintenance Center (OMC).

Figure 1-1 Composition of the BTS3012 system

Abis

Um

MS

BTS3012cabinet

BTS3012 system

BSC

MMI

Environmentmonitoring equipment

Antenna subsystem

Site maintenanceterminal system

Remote sitemaintenance system

The BTS3012 system consists of the following parts:

BTS3012 cabinet Antenna subsystem O&M subsystem

1.1.2 Cabinet The BTS3012 cabinet is the core of the BTS system. It has the following subracks:

DAFU subrack DTRU subrack FAN subrack Common subrack



Cabinet top subrack

The BTS3012 cabinet also has a BBU/transmission unit.

Figure 1-2 shows the BTS3012 cabinet under full configuration.




Figure 1-2 BTS3012 cabinet under full configuration

Wiring & Air Inlet

Wiring

DCOM

DDPU

DDPU

DCOM

DDPU

DTRU

DTRU

DTRU

DTRU

DTRU

DTRU

Wiring

FAN

Air Inlet

DMLC

Powerand EMC

Transmission Unit

DCOM

DELC

DELC

DSAC

Transmission Unit

DTMU

DTMU

DEMU

DCCU

DCSU

DATU

DSAC: Signal Access Card for DTRU BTS DELC: E1 Signal Lightning-Protection Card for DTRU BTS DMLC: Monitor Signal Lightning-Protection Card for DTRU BTS DCOM: Combining Unit for DTRU BTS DDPU: Dual-Duplexer Unit for DTRU BTS DTRU: Double-Transceiver Unit FAN (NFCB): NodeB Fan Controlling and Monitoring Board DTMU: Transmission Timing & Management Unit for DTRU BTS DEMU: Environment Monitoring Unit for DTRU BTS DATU: Antenna and TMA Control Unit for DTRU BTS DCSU: Combined Cabinet Signal Connection Unit for DTRU BTS DCCU: Cable Connection Unit for DTRU BTS



DAFU Subrack The DAFU subrack consists of the DDPU and the DCOM.

Under full configuration, the subrack consists of maximum six boards. There are maximum six DDPUs. The DCOM is used only when the cell is configured with more than four carriers.

The interfaces of the DDPUs and the DCOMs are on the front panel. The boards of the DAFU subrack connect with other boards or units in the cabinet through cables.

The DAFU subrack performs the following functions:

Receiving and transmitting the RF signals Controlling the low noise amplification

DTRU Subrack One DTRU subrack supports up to six DTRUs.

The DTRU performs the following functions:

Modulation, frequency up-conversion, filtering, RF hopping, signal amplification, and combiner output to convert the baseband signals of two carriers to the RF signals.

RF signals dividing, diversity receiving, RF hopping, and demodulation of two carriers. Signaling processing, channel coding, interleaving and deinterleaving, modulation, and

demodulation. Amplification of output power. Transmit diversity, 4-way diversity receive. Transmit-combining and Power Boost Technology (PBT).

FAN Subrack The FAN subrack has only one FAN box inside it. The FAN box contains one fan monitoring board and four fans. The fan monitoring board detects the temperature at the air inlets at the bottom of the cabinet, and adjusts the speed and working status of the fans.

The rear part of the cabinet top and the air inlets at the bottom of the cabinet form a ventilation circuit, cooling the entire cabinet. The fans take the N+1 redundancy backup strategy. When one fan fails, the other fans run at full speed. In normal temperature, the fans can meet the heat dissipation requirements.

Common Subrack The common subrack is in the lower part of the cabinet. It consists of the following components:

Transmission/Timing/Management Unit for DTRU BTS (DTMU) The DTMU is an entity for basic transmission and control in the BTS3012. It works as a main controller.

Environment Monitoring Unit for DTRU BTS (DEMU) The DEMU monitors the environment in the equipment room and collects information on environment monitoring and alarms.

Antenna and TMA Control Unit for DTRU BTS (DATU)




The DATU feeds the TMA and transmits the remote electrical tilt unit (RET) control signals.

Combined Cabinet Signal Connection Unit for DTRU BTS (DCSU) The DCSU transfers signals for the combined cabinet and cabinet group between the common subrack and the cabinet top subrack.

Cable Connection Unit for DTRU BTS (DCCU) The DCCU converts the input and output signals of the common subrack.

Common Module Backplane for DTRU BTS (DCMB) The DCMB is the backplane in the BTS3012 common subrack.

Cabinet Top Subrack The cabinet top subrack is on the top of the cabinet. It consists of the following components:

Monitor Signal Lightning-Protection Card for DTRU BTS (DMLC) The DMLC provides lightning protection for various routes of input and output signals.

E1 Signal Lightning-Protection Card for DTRU BTS (DELC) The DELC provides lightning protection for E1 signals.

Signal Access Card for DTRU BTS (DSAC) The DSAC has two C1BUS3 ports for the DTMU to communicate with the external equipment and supports six-route Boolean value input.

Cabinet top Backplane for DTRU BTS (DCTB) The DCTB is the backplane in the BTS3012 cabinet top subrack.

BBU/Transmission Unit Baseband Unit (BBU)/transmission unit is under the common subrack. The space for the BBU is reserved. The built-in SDH and the microwave transmission device can be installed in the reserved space.

1.1.3 Antenna Subsystem The antenna subsystem receives the UL signals and transmits the DL signals. The subsystem consists of:

Antenna Tower-Mounted Amplifier (TMA) Feeder Jumper Remote Control Unit (RCU) Smart Bias-Tee (SBT)

The TMA is optional depending on network planning and actual requirements.

1.1.4 O&M Subsystem The O&M subsystem performs remote operation and maintenance through the OMC. It performs near end operation and maintenance through the MMI. Both require the support of the BTS3012 O&M program.



The O&M software is the common control part of the BTS3012 software. It is the core of the BTS3012 O&M. All the other BTS3012 software has interfaces with the O&M software.

The following are the functions of the O&M program:

Downloading the BTS3012 software Initializing the BTS3012 Monitoring and managing the BTS3012 running status Collecting alarms Tracing the resource usage and interfaces

1.2 Software Architecture This section describes the software architecture of the BTS3012.

It has the following sections:

Composition Signaling Processing Software Baseband Signal Processing Software O&M and Transmission Device Control Software

1.2.1 Composition The BTS3012 software is distributed in each module of the BTS.

The software performs the following functions:

RL hierarchical protocol Abis interface protocol procedure Radio channel real-time management Internal connection protocols Transmission device control BTS3012 operation and maintenance MMI management

The BTS3012 software system has the following parts:

Signaling processing software Baseband signal processing software O&M and transmission device control software

Figure 1-3 shows the BTS3012 software architecture.




Figure 1-3 Software architecture

Signalingprocessing software

Baseband signalprocessing software

O&M and transmissiondevice control software

1.2.2 Signaling Processing Software Data, voice, and signaling are transmitted between the BTS and the BSC.

The signaling processing software is the control part of the DTRU. It performs the following functions:

Transparently transmitting layer 3 messages of the Um interface to the Abis interface Managing the radio resources together with the BSC LAPD at the Abis interface LAPDm at the Um interface Operating and maintaining the DTRU

Signaling processing is the core of the BTS service processing function.

The software runs on the DTRU.

1.2.3 Baseband Signal Processing Software The baseband signal processing software performs the following functions:

Coding and decoding of the voice, data and signaling on the radio channel Demodulating the received signals Processing the signals at the Um interface together with the hardware circuit of the

digital signal processing part on the DTRU

The baseband signal processing software runs on the DTRU.

1.2.4 O&M and Transmission Device Control Software The O&M software is the common control part of the BTS software. It is the core of the BTS O&M system. All the other BTS software has interfaces with the O&M software.

The O&M software performs the following functions:

Loading the BTS software Initializing the BTS Monitoring and managing the BTS running status



Collecting alarms Tracing the resource usage and interface messages

The transmission device control software is a module of the O&M software. It controls the transmission links between the BSC and the BTS.

The transmission device control software supports flexible link configuration between the BTS and the BSC, through the star, tree, and chain networking.

Each site supports up to 36 TRXs. The transmission device control software also enables the DTMU to perform the remote loopback test.

The O&M software runs on the DTMU.

1.3 Logical Architecture This section describes the logical architecture of the BTS3012 including its composition and the common subsystem.

1.3.1 Composition The BTS3012 communicates with the BSC and the MS through the Abis interface and the Um interface respectively. It processes the Um interface protocol and the Abis interface protocol to perform information conversion between the BSC and the MS.

As shown in Figure 1-4, the logical architecture of the BTS3012 system has the following subsystems:

Common subsystem DTRU subsystem DAFU subsystem Antenna subsystem

Figure 1-4 shows the logical architecture of the BTS3012.




Figure 1-4 Logical architecture of the BTS3012

TMA TMA

DTRU DAFU

TMA TMA

DTRU DAFU

TMA TMA

DTRU DAFU

DATU

Extensioncabinet/group

MS

Um

DATU

Fiber

E1

Abis

NFCB

Optical transmissionequipment (optional)

DTMU

DEMU

E1

BITSMonitor

Pro

tect

ion

for s

igna

l

Commonsubsystem

DTRUsubsystem

DAFUsubsystem

Antennasubsystem

Electric tilt antenna

Electric tilt antenna& TMA feed

& TMA feed

The signal lightning protection part performs lightning protection of signals including E1 signals, monitoring signals, and Boolean value signals. The DELC, DMLC, and DSAC perform this function.

1.3.2 Common Subsystem The common subsystem manages the whole BTS by providing interfaces for the reference clock, power supply, transmission, maintenance, and external alarm collection.

The subsystem consists of the BTS common subsystem and the cabinet top access subsystem.

BTS Common Subsystem The BTS common subsystem performs the following functions:

Introducing the E1 signal into the BTS Introducing the SDH into the BTS Providing clock for the BTS Collecting and monitoring the environmental alarm Synchronizing clocks

Cabinet Top Access Subsystem The cabinet top access subsystem performs the following functions:

Providing E1 lightning protection Providing signal lightning protection Introducing the signals into the BTS



For details about the common subsystem, see 2 "Common Subsystem."

1.3.3 DTRU Subsystem The DTRU subsystem has two parts, the baseband part, and the RF part.

The baseband part consists of four modules: SCP, DSP, CUI, and power supply. The RF part consists of the transceiver and the PAU.

The DTRU subsystem performs the following functions:

Processing the baseband signals Receiving and transmitting the RF signals Amplifying the power Transmit diversity and 4-way diversity receive PBT

For details about the DTRU subsystem, see 3 "DTRU Subsystem."

1.3.4 DAFU Subsystem The DAFU subsystem communicates with the DTMU through the CBUS3.

The DAFU subsystem performs the following functions:

Transmitting the combined TRXs Transmit and receive duplex Detecting alarms and reporting antenna and feeder standing wave and low noise

amplification Lower noise amplification gain control Detecting and reporting the transmit power at antenna port Detecting and reporting board temperature Detecting software in-position status Software upgrade without impacting system performance

For details about the DAFU subsystem, see 4 "DAFU Subsystem."

1.3.5 Antenna Subsystem The antenna subsystem receives and transmits signals over the air interface.

It has the following components:

Antenna Feeder TMA (optional) RCU SBT

For details about the antenna subsystem, see 5 "Antenna Subsystem."




1.4 Bus Structure The BTS3012 has four types of buses:

Data buses between the DTMU and the DTRU (DBUS1–DBUS6) Control buses

− CBUS1 between DTMUs − CBUS2 between the DTMU and the DTRU − CBUS3 between the DTMU and the DDPU, DEMU, NFCB, DATU, and the external

alarm box Clock buses for the frame clock (FCLK), the 1/8-bit clock (OBCLK), the RF reference

clock (SREF), the frame number (FN), the DBUS clock (DBUSCLK), and the DBUS frame header (DBUSFS)

Hopping buses between the DTRUs in a cabinet

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle 2 Common Subsystem


2 Common Subsystem

About This Chapter


Title Description

2.1 Composition Introduces the components of the BTS3012 common subsystem.

2.2 Functions Introduces the functions of the BTS3012 common subsystem.

2.3 DTMU Introduces the features, working environment, and functions and principles of the DTMU.

2.4 DCCU Introduces the features, working environment, and functions and principles of the DCCU.

2.5 DCSU Introduces the features, working environment, and functions and principles of the DCSU.

2.6 DEMU Introduces the features, working environment, and functions and principles of the DEMU.

2.7 DATU Introduces the features, working environment, and functions and principles of the DATU.

2.8 DCMB Introduces the features, working environment, and functions and principles of the DCMB.

2.9 DELC Introduces the features, working environment, and functions and principles of the DELC.

2.10 DMLC Introduces the features, working environment, and functions and principles of the DMLC.

2.11 DSAC Introduces the features, working environment, and functions and principles of the DSAC.

2.12 DCTB Introduces the features, working environment, and functions and principles of the DCTB.

2 Common Subsystem HUAWEI BTS3012 Base Station



2.1 Composition The BTS3012 common subsystem consists of the BTS common subsystem and the cabinet top access subsystem.

2.1.1 BTS Common Subsystem The BTS3012 common subsystem is located under the FAN subrack.

The common subsystem consists of the following components:

DTMU DEMU DATU DCSU DCCU

Figure 2-1 shows boards in the BTS3012 common subsystem.

Figure 2-1 Boards in the BTS3012 common subsystem

0 2

DTM

U

DTM

U

D

EM

U

DCS

U

DCC

U

DATU

1 3 4 5 6 7

Table 2-1 lists boards and their slot numbers.

Table 2-1 Mapping between the boards and the slot numbers in the common subsystem

Board Slot No.

DTMU 0, 1

DEMU 2, 3, 4, 7

DATU 2, 3, 4, 7

DCSU 5

DCCU 6

2.1.2 Cabinet Top Access Subsystem The cabinet top access subsystem is on the top of the cabinet.

This subsystem consists of the following components:



DMLC DELC DSAC

Figure 2-2 shows boards in the BTS3012 cabinet top access subsystem.

Figure 2-2 Boards in the BTS3012 cabinet top access subsystem

D

M

L

C

D

E

L

C1

D

E

L

C

D

S

A

C0

Table 2-2 lists boards and their slot numbers.

Table 2-2 Mapping between the boards and the slot numbers in the cabinet top access subsystem

Board Slot No.

DMLC 0, 1, 2

DELC 0, 1, 2

DSAC 3

2.2 Functions The BTS3012 common subsystem provides interfaces for the primary reference clock, power supply, transmission, maintenance, and external alarm collection. It controls and manages the whole BTS.

The common subsystem performs the following functions:

Providing E1 signals access and lightning protection Collecting and monitoring environmental alarms Providing clock for BTS Providing signal lightning protection Accessing Boolean value Controlling electrical antenna and feeding the TMA




2.3 DTMU 2.3.1 Introduction

DTMU is the Transmission & Timing & Management Unit for the BTS3012.

It has the following features:

Backup between the active and standby boards. Backup between the clock modules of the active and standby boards. Backup of the E1 port and main control unit.

The DTMU also performs the following functions:

Managing the BTS3012. Providing the external GPS input. Providing the BITS synchronized clock input. Providing terminal MMI maintenance of the 10 M network port. Connecting the BTS and the BSC. Providing 4-route or 8-route E1 input. Providing four or eight E1 transmissions between the active and the standby boards. Supporting 8-route digital alarm input. Two routes are lightning arrester failure alarm

detection. Supporting 4-route extended digital control signal output. Monitoring the external fan control panel and power module. Supporting transmission modes of 75-ohm and 120-ohm impedance.

The E1 interface accords with the G.703/G.704.

2.3.2 Working Environment Figure 2-3 shows the working environment of the DTMU.



Figure 2-3 DTMU working environment

DSAC

TBUSDBUS

E1 CBUSDELC

DTMU

Monitor、BITS

E1

Monitor、BITS

Common subsystem

DBUS/TBUS/CBUS

Optical transmission equipmentOptical Fiber

2.3.3 Functions and Principles The DTMU consists of three modules:

BTS Interface Unit (BIU) Main Control Unit (MCU) Main Clock Board (MCK)

Figure 2-4 shows the structure of the DTMU.

Figure 2-4 DTMU structure

MCK

OML

DBUS

CBUS2

Clock

BIU DTRU

DTMU

BSC

MCUMMI

LMT

Abis

Externalsynchronized clock

Subrack number and clock

The DTMU performs the following functions:




BIU − Connects the BTS and the BSC − Four or eight-E1 backup between the active and the standby DTMUs − Exchanges the TS data between the E1 and the DBUS − Provides clock source that synchronizes with the upper level clock

MCU − Supports multi communication protocols including the UART and the HDLC − Controls the BIU and provides communication between the BSC and the BTS − Provides platform for the MCK software

MCK − –Provides high-accuracy clock source with system clock based on it − –Judges the status of the phase-lock, provides software phase-lock, DA adjustment,

and generates the subrack number − –Transmits clock signals between the active and the standby DTMUs and the

synchronizes signals

2.4 DCCU 2.4.1 Introduction

The DCCU has the following features:

3V3 as the power in and out parts –48 V power supply EMI filtering

2.4.2 Working Environment Figure 2-5 shows the working environment of the DCCU.

Figure 2-5 DCCU working environment

DCMB DCCU

NFCB

Power

DCTB



2.4.3 Functions and Principles The DCCU consists of the signal conversion unit and the EMI filtering unit.

Figure 2-6 shows the structure of the DCCU.

Figure 2-6 DCCU structure

DCCU

EMI

DCMB

-48 V

DCTB

NFCB

Signalconversion

filtering

The DCCU performs the following functions:

Signal conversion part The signals from the DCMB are transmitted to the DCCU through three 2 mm-connectors, and then to the FAN subrack and cabinet top through the connectors on the front panel.

EMI filtering part The –48 V power goes through the EMI filter to the DCMB for the use of other boards in the common subrack.

2.5 DCSU 2.5.1 Introduction

The DCSU provides DIP switches for configuration of other boards in the subrack. The DIP switches are about 3 cm to 4 cm from the front panel, arrayed from top to bottom according to the function areas.

For details about the DIP switches on the DCSU, see the BTS3012 Base Station Hardware Description Manual – Boards.

2.5.2 Working Environment Figure 2-7 shows the working environment of the DCSU.




Figure 2-7 DCSU working environment

DCMB DCSUDTRB

DCTB

2.5.3 Functions and Principles The DCSU transfers signals for combined cabinet and cabinet group.

Figure 2-8 shows the structure of the DCSU.

Figure 2-8 DCSU structure

DCSU

DCMBTo DTRB

To DCTB

Input signals forcombined cabinet

Output signals forcombined cabinet

2.6 DEMU 2.6.1 Introduction

The DEMU is placed in the common subrack. It provides 32-channel Boolean value input, 4-channel analog value input, and 6-channel Boolean value output.

The DMLC is required on the top of the cabinet if the DEMU is configured.



2.6.2 Working Environment Figure 2-9 shows the working environment of the DEMU.

Figure 2-9 DEMU working environment

DMLC DEMUCBUS3Monitor signal

Common subsystem

DBUS/TBUS/CBUS

2.6.3 Functions and Principles The DEMU has the following circuits:

Power circuit MCU control circuit Analog signal detecting circuit Boolean value input and output circuit Board serial port circuit Board power and voltage detecting circuit

Figure 2-10 shows the structure of the DEMU.

Figure 2-10 DEMU structure

MCUcontrol circuit

Board power andvoltage detecting

circuit

Powercircuit

Analog signaldetecting circuit

Boolean value inputand output circuit

Board serial portcircuit

-48 V

24 V/12 V/5 V/3.3 V




The DEMU monitors the environment in the equipment room and collects information on environment monitoring and alarms. It maintains the environment in the equipment room to ensure the normal operation of the equipment.

2.7 DATU 2.7.1 Introduction

The DATU is placed in the common slot of the common subrack. There are maximum two DATUs under full configuration.

2.7.2 Working Environment Figure 2-11 shows the working environment of the DATU.

Figure 2-11 DATU working environment

CBUSTBUS

DTRU DAFU

DBUS

DATUCBUS3TMA TMA

MSBais Tee

Bais Tee

DTRU subsystem

Electric tilt antenna, TMA feed

DAFU subsystem Antennasubsystem

DBUS/TBUS/CBUS


2.7.3 Functions and Principles Figure 2-12 shows the structure of the DATU.

Figure 2-12 DATU structure

DTMU DATUSMAoutput

DDPU

The DATU performs the following functions:

Transmitting the Remote Electrical Tilt unit (RET) control signals.



Feeding of the Tower Mounted Amplifier (TMA). Communicating with the DTMU through CBUS3 for control and alarm report.

2.8 DCMB 2.8.1 Introduction

The DCMB is the backplane in the BTS3012 common subrack with the DTMU, DCCU, DCSU, DATU, and DEMU placed in it. The DATU and the DEMU are placed in slots 2, 3, 4, and 7.

2.8.2 Working Environment Figure 2-13 shows the working environment of the DCMB.

Figure 2-13 DCMB working environment

DCMB

DTMU

DCCU

DEMU

DATU

DCSU

2.8.3 Functions and Principles The DCMB performs the following functions:

Providing slots for two DTMUs, one DEMU, two DATUs, one DCCU, and one DCSU, and connections between these boards.

Providing –48 V power distribution from the DCCU to the common subsystem.

2.9 DELC 2.9.1 Introduction

The DELC is placed in slots 0 to 2 of the cabinet top subrack with the DMLC.

The DELC is mandatory and there is one DELC in minimum configuration.




Without the DMLC, there are maximum three DELCs, supporting up to 12 routes of protected E1 signals. Each DMLC provides lightning protection for 4-channel E1 signals sent to the DCCU.

2.9.2 Working Environment Figure 2-14 shows the working environment of the DELC.

Figure 2-14 DELC working environment

DELCE1

Abis

DTMUDCCUDCTB

2.9.3 Functions and Principles Figure 2-15 shows the structure of the DELC.

Figure 2-15 DELC structure

DB374-routeE1

Lightningprotection

circuit

DB25 connectorDELC

E1DCCU

One DELC provides lightning protection for 4-route E1 signals. Three DELCs (under full configuration) provide 12-route E1 signal lightning protection.

2.10 DMLC 2.10.1 Introduction

The DMLC and the DELC are placed in slots 0 to 2 of the cabinet top subrack. The DMLC and the DELC can be placed in each other's slots.

The DMLC is optional with one card under full configuration.

2.10.2 Working Environment Figure 2-16 shows the working environment of the DMLC.



Figure 2-16 DMLC working environment

Common subsystem

DMLC DEMUCBUS3

DBUS/TBUS/CBUS

Monitor signals

2.10.3 Functions and Principles Figure 2-17 shows the structure of the DMLC.

Figure 2-17 DMLC structure

Boolean value inputlightning protection

Boolean value output

Analog inputlightning protection

DMLC

DEMU

DDF

Externaldevice

The DMLC provides lightning protection for various routes of input and output signals:

Thirty-two-route Boolean value input Six-route Boolean value output Four-route analog input Smoke/water/access control/infrared/humidity/temperature sensor signal input

2.11 DSAC 2.11.1 Introduction

The DSAC is placed in slot 3 of the cabinet top subrack. The number of the DSAC under full configuration is one.

The DSAC cannot be placed in the slots of the DMLC & DELC.




2.11.2 Working Environment Figure 2-18 shows the working environment of the DSAC.

Figure 2-18 DSAC working environment

DSAC

DTMU

DCCUDCTB

2.11.3 Functions and Principles Figure 2-19 shows the structure of the DSAC.

Figure 2-19 DSAC structure

Front panel

CBUS3×2alarm input

Failurealarminput

Controlsignaloutput

Signalprotection

Backplanesignal input

DCTB

DSAC

Boolean value

The DSAC performs the following functions:

Six-route Boolean value input and four-route output of the main node. Two-route CBUS3 output. Two-route input of lightning protection arrester failure alarm. Access protection of BITS clock input.

2.12 DCTB 2.12.1 Introduction

The DCTB is placed in the cabinet top subrack. It is mandatory and has four slots in it.

The DMLC and the DELC can be placed in each other's slots in slots 0 to 2.



The DSAC is placed in slot 3.

2.12.2 Working Environment Figure 2-20 shows the working environment of the DCTB.

Figure 2-20 DCTB working environment

DCTB

DMLC

DELC

DSAC

Monitor signal

E1 signal

CBUS3 signalDCSU

DCCU

2.12.3 Functions and Principles Figure 2-21 shows the structure of the DCTB.

Figure 2-21 DCTB structure

DCTB

DCCU

DEMU

DCSU

DMLC

DELC

DSAC

The DCTB performs the following functions:

Connecting signal cables between the cabinet top subrack and the boards, such as the DCCU, DCSU, and the DEMU

Supporting two-combined cabinet and three-cabinet group of the BTS3012

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle 3 DTRU Subsystem


3 DTRU Subsystem

About This Chapter


Title Description

3.1 Components Introduces the components of the DTRU subsystem.

3.2 Functions Describes the functions of the DTRU subsystem.

3.3 DTRU Describes the features, working environment, and functions and principles of the DTRU.

3.4 DTRB Describes the features, working environment, and functions and principles of the DTRB.

3 DTRU Subsystem HUAWEI BTS3012 Base Station



3.1 Components The DTRU subsystem consists of the Double-Transceiver Unit (DTRU) and the DTRU Backplane (DTRB). The BTS3012 can be configured with up to six DTRUs, as shown in Figure 3-1.

Figure 3-1 DTRU subsystem under full configuration

NBBIDTRU DTRU DTRU DTRU DTRU DTRU

1 2 3 4 50

3.2 Functions The DTRU subsystem performs the following functions:

The RF transmitting part Performs modulation, up-conversion, filtering, RF hopping, signal amplification, and combiner output to convert the baseband signals of the two carriers to the RF signals.

The RF receiving part Performs RF signals dividing, diversity receiving, RF hopping, and demodulation of the two carriers.

The baseband processing part Performs the following functions: − Signaling processing − Channel coding − Interleaving and deinterleaving − Modulation and demodulation − Transmit diversity and 4-way diversity receive

Output power amplification RF signals combination and PBT



3.3 DTRU 3.3.1 Introduction

The DTRU is placed in the DTRU subrack. One DTRU module can process two carriers. The DTRU can also be configured in the BTS30 or BTS312 cabinets.

3.3.2 Working Environment Figure 3-2 shows the working environment of the DTRU.

Figure 3-2 DTRU working environment

DBUS/TBUS/CBUS

CBUS2

CBUS3

DTRU DCOM/DDPU

FH_BUS

CBUS2

CBUS3

DTRU DCOM/DDPU

CBUS2

CBUS3

DTRU DCOM/DDPU

DTRU subsystem DAFU subsystem

3.3.3 Functions and Principles The DTRU can be functionally divided into three modules:

DTRU Baseband and RF Unit (DBRU) DTRU Power Amplifier Unit (DPAU) DTRU Power Supply Unit (DTPS)

Figure 3-3 shows the functional structure of the DTRU.




Figure 3-3 Function structure of the DTRU

DTMU

DTPS

DTRU

-48 V DC

DPAU

DBRUDAFU

DBRU The DBRU is the main functional module of the DTRU. The DBRU performs modulation/demodulation, data processing, and combining/dividing between the baseband signals and the RF signals.

DPAU The DPAU performs the following functions:

Amplifying the Tx signals transmitted from the DBRU to the required level. Coupling the output power signals for loopback test and power detection. Detecting the temperature of the power amplifier. Supporting combination of transmit signals and PBT.

DTPS The DTPS is the power supply board of the DTRU. The DTPS converts the –48 VDC power input into +28 VDC for the DPAU.

3.4 DTRB 3.4.1 Introduction

The DTRB is also placed in the DTRU subrack. The DTRB has six slots. Each slot has one DTRU.

3.4.2 Working Environment Figure 3-4 shows the working environment of the DTRB.



Figure 3-4 DTRB working environment

DTRB

DTRU

DTRU

DTRU

DTRU

DTRU

DTRU

3.4.3 Functions and Principles Figure 3-5 shows the functional structure of the DTRB.

Figure 3-5 Functional structure of the DTRB

DTMU

DTRB

DBUS,TBUS,CBUS

DTRU

DTRU

DTRU

DCSU

The connections between the DTRB, DCSU, DTRU, and DTMU are as follows:

The DTRB connects the DCSU and the DTRU. The DTRU connects to the DTMU through the DTRB and the DCSU. The DTRB connects to the DCSU and the DCSU connects to the DTMU.

The slot number and the rack number of the DTRU are determined by the DTRB. All the in-position signals are transmitted to the DCSU through the DTRB.




The clock signals of the BTS system are sent from the DTMU to the DTRB through the DCSU. The DTRB then sends the clock signals to each DTRU.

The uplink or downlink control bus and the data bus of the DTRU connect to the DCSU through the DTRB.

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle 4 DAFU Subsystem


4 DAFU Subsystem

About This Chapter


Title Description

4.1 Components Introduces the components of the DAFU subsystem.

4.2 Functions Introduces the functions of the DAFU subsystem.

4.3 DDPU Describes the features, working environment, and functions and principles of the DDPUs.

4.4 DCOM Describes the features, working environment, and functions and principles of the DCOMs.

4 DAFU Subsystem HUAWEI BTS3012 Base Station



4.1 Components The DAFU subsystem consists of the Dual-Duplexer Unit for the DTRU BTS (DDPU) and the Combining Unit for the DTRU BTS (DCOM). The DDPUs and DCOMs are placed in the DAFU subrack. They can be placed in each other's slots.

Figure 4-1 shows the DAFU subsystem under full configuration.

Figure 4-1 DAFU subsystem under full configuration

NBBI

D

C

O

M

D

D

P

U

D

C

O

M

D

D

P

U

D

C

O

M

D

D

P

U

1 2 3 4 50

4.2 Functions Figure 4-2 shows the logical location of the DAFU subsystem.

Figure 4-2 Logical location of the DAFU subsystem

TMA TMA

DTRU DAFU

Antennasubsystem

DAFUsubsystem

TMA TMA

DTRU DAFU

TMA TMA

DTRU DAFU

DTRUsubsystem

The DAFU subsystem performs the following functions:

Outputting transmit power after combing the signals from multiple TRXs Transmitting and receiving signals through a duplex Detecting and reporting antenna VSWR alarms and the low noise amplifier alarms



Controlling low noise amplification Detecting and reporting the transmit power of antenna ports Detecting and reporting the board temperature Detecting whether a board is in position Upgrading the software without affecting the system performance

4.3 DDPU 4.3.1 Introduction

The DDPU sends multiple channels of RF Tx signals from the DTRU to the antenna through the duplex. The DDPU also sends the signals from the antenna back to the DRTU after the signals are amplified by the duplexer.

4.3.2 Working Environment Figure 4-3 shows the working environment of the DDPU.

Figure 4-3 DDPU working environment

DAFUsubsystem

TMA TMACBUS2

CBUS3

DTRU DDPU

Antennasubsystem

CBUSTBUS

FH_BUS

Um

MSTMA TMA

CBUS2

CBUS3

DTRU DDPU

TMATMACBUS2

CBUS3

DTRU DDPU


DTRUsubsystem

DBUS

DBUS/TBUS/CBUS

4.3.3 Functions and Principles Figure 4-4 shows the functional structure of the DDPU.

4 DAFU Subsystem HUAWEI BTS3012 Base Station



Figure 4-4 Functional structure of the DDPU

Duplexer

1/4 ATT

Processingthe detected

alarmsCommunication

interface

Duplexer

1/4 ATT

TX/RX ANT A

TX1 Power coupling

RX1ARX2ARX3A

RX4A

RX1BRX2BRX3BRX4B

LNA

TX2

BUS

DC -48V

TX/RX ANT B

DDPU

DDLC

Power coupling

The DDPU consists of the Dual-Duplexer for PGSM (DDUP) and the Dual LNA & Control Unit for the DTRU BTS (DDLC).

The DDPU performs the following functions:

Sending multiple channels of the RF signals from the DTRU to the antenna Sending signals from the antenna to the DTRU after amplification and quartering Detecting the antenna and feeder standing wave alarms Controlling the low noise amplification Lighting protection supported by the ANT port

4.4 DCOM 4.4.1 Introduction

The DCOM is placed in the DAFU subrack. It can be placed in the DDPU slot. The DCOM combines two carriers into one channel (the 2-in-1 function). The DCOM is required when the DTRU are not sufficient.

4.4.2 Working Environment Figure 4-5 shows the working environment of the DCOM.



Figure 4-5 DCOM working environment

DAFU

DTRU

DAFU subsystem

CBUSTBUS

FH_BUS

CBUS2

CBUS3

DTRU


DTRU subsystem

DBUS

DDPUDCOM DDPU

Um

MSTMA TMA

CBUS2

Antennasubsystem

DBUS/TBUS/CBUS

4.4.3 Functions and Principles The DCOM consists of a 3 dB electrical bridge and a 2-in-1 combiner with large power.

Figure 4-6 shows the functional structure of the DCOM.

Figure 4-6 Functional structure of the DCOM

Load of largepower

3-dB electricalbridge

TX1

TX2

TX1+TX2

The DCOM combines two channels of the Tx signals from the DTRU and sends them to the DDPU. The Tx signals from the DTRU can be combined signals of the carriers with different or same frequencies.

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle 5 Antenna Subsystem


5 Antenna Subsystem

About This Chapter


Title Description

5.1 Components Introduces the components of the antenna subsystem.

5.2 Antenna Introduces the working principles, types, specifications, RET, feeder, and TMA of the antenna.

5.3 Feeder Describes the features and working principles of the feeder in the antenna subsystem.

5.4 TMA Describes the features and working principles of the TMA in the antenna subsystem.

5 Antenna Subsystem HUAWEI BTS3012 Base Station



5.1 Components As shown in Figure 5-1, the antenna subsystem consists of the following parts:

Antenna Feeder Jumpers TMA

Figure 5-1 Antenna subsystem

Antenna

TMA

Antennasupport

Jumper

JumperFeeder

Jumper

The antenna subsystem serves as a channel for transmitting and receiving the RF signals. It transmits the RF signals after modulating them and receives signals from the MS.

5.2 Antenna The antenna is the terminating point of transmission and the starting point of reception. The type, gain, azimuth angle, and front-to-rear ratio of the antenna affect system performance. Network planners can set these parameters based on the actual network requirements such as capacity and coverage.

5.2.1 Working Principles An antenna works as a type of converter. It converts the current transmitted over the transmission cables into the electromagnetic wave and vice versa.

In mobile communication systems, the antenna consists of an array of element antennas, as shown in Figure 5-2.



Figure 5-2 Antenna composition

Elementantenna

Feedingnetwork

Antennaconnector

Directional antenna Omnidirectional antenna

Feedingnetwork

Elementantenna

Feedingnetwork

Antennaconnector

The elements of the antenna are as follows:

The element antenna is a half-wave element. Feeding network is an equal power division network.

The antenna connector is a DIN connector (7/16'') usually installed at the bottom or back of the antenna.

An antenna cover encloses the element antennas and the feeding network to protect the antenna from damage. The antenna cover is made of glass reinforced plastic. It has higher intensity and smaller loss to waves.

The antennas work outdoors, so there is an exhaust outlet for drainage at the bottom of the antennas.

5.2.2 Types The types of the BTS3012 antenna are as follows:

By radiation features in horizontal directions, the BTS3012 antennas are classified into omnidirectional antennas and directional antennas

By polarization features, the BTS3012 antennas are classified into single polarization antennas and dual polarization antennas

Most omnidirectional antennas are single polarization ones. Directional antennas can be either single polarization or dual polarization ones.

For an omnidirectional antenna, the wave energy is the same in all horizontal directions but varies in vertical directions.

For a directional antenna, the wave energy varies in horizontal directions and vertical directions.




Single polarization antennas are vertical polarization antennas. The polarization of their elements is vertical.

As shown in Figure 5-3, dual polarization antennas are usually 45° polarization antennas. Their elements cross in pairs. In a pair, one element deviates rightward from the vertical by 45°, and the other element deviates, leftward by 45°.

Figure 5-3 Types of antenna

Omnidirectionalantenna

Single polarizationantenna

Dual polarizationantenna

A dual polarization antenna equals to the combination of two single polarization antennas. Dual polarization antennas are being used widely as they are economical.

5.2.3 Specifications

Polarization Polarization means the direction of the electric field vector in the maximum radiation direction of the antenna.

The waves radiated from an antenna are made up of an electric field vector and a magnetic field vector. The two vectors differ in special directions.

The polarization of an antenna refers to the direction of the electric field vector in the maximum radiation direction of the antenna. It is usually identical with the direction of its elements.



Horizontal Radiation Pattern The pattern is a curve that the far zone radiated electric field of the antenna changes with the angle in a horizontal plane. It reflects the radiation features of the antenna on the horizontal plane. For example, the ideal horizontal radiation pattern of an omnidirectional antenna is a circle.

The electric filed amplitudes in a horizontal radiation pattern are normalized according to the electric filed amplitude in the maximum radiation direction.

Figure 5-4 shows the horizontal radiation pattern of a –65° antenna.

Figure 5-4 Horizontal radiation pattern

Horizontal Lobe Width The width refers to the angle between the two directions in the horizontal radiation pattern in which the radiation power is 3 dB less than the maximum radiation power. The 65° antenna is the antenna with a horizontal lobe width of 65°.

Vertical Radiation Pattern The pattern is a curve that the far zone radiated electric field of the antenna changes with the angle in a vertical plane. It reflects the radiation features of the antenna on the vertical plane.

Generally, the electric field amplitudes in a vertical radiation pattern are normalized according to the electric field amplitudes in the maximum radiation direction. For a directional antenna, the side lobe above the main lobe should be as small as possible to reduce interference on communications quality.

Figure 5-5 shows the vertical radiation pattern of a –65° antenna.




Figure 5-5 Vertical radiation pattern

Vertical Lobe Width The width refers to the angle between the two directions in the vertical radiation pattern of the antenna. In the angle, the radiation power is 3 dB less than the maximum radiation power.

Gain Gain refers to the power density ratio of a certain point in the maximum radiation direction to the same point of the ideal point source antenna at the same input power. It indicates the radiation capability of the antenna in a specific direction. In general, the higher the gain, the smaller the lobe width and the more the concentrated wave energy.

Echo Loss It refers to the ratio of the reflected power to the incidence power at the antenna connector. It indicates the matching features of the antenna.

Front-to-Rear Ratio This specification applies only to directional antennas. The front-to-rear ratio of an antenna is the ratio of the power density in the forward maximum radiation direction to that in the backward maximum radiation direction of the antenna. It reflects the suppression capability of the antenna to backward interference.

Passive Inter-Modulation Passive inter-modulation means the inter-modulation between passive components such as connectors, feeders, antennas, and filters due to their non-linearity in high power conditions.

Passive components are usually linear but they may have more or less non-linearity when working in high power conditions. The possible factors for non-linearity are:

Contact of different metal materials Uneven contact surface of the same material



Loose contact Magnetic materials

Power Bearing Capability The power bearing capability of an antenna is the maximum transmit power the antenna can bear. Transmitted signals exceeding the power bearing capability may damage the antenna.

Antenna Isolation To reduce the transmitter's negative effect on the receiver, there must be enough isolation between two antennas, and between two polarization directions of a dual-polarization antenna. In the GSM system, the antenna isolation must be greater than 30 dB.

5.2.4 Functional Principles of the RET System

Overview of the RET Adjusting the antenna tilt is an important way to optimize the network. Most antennas need this operation.

There are two ways to adjust the antenna tilt:

Setting the tilt with an adjustable mechanical bracket. This way is called the mechanical tilt. Maintenance engineers will adjust the bracket on site.

Setting the tilt electrically by adjusting the phase of the internal shifter of the antenna. This way is called the electrical tilt. You can adjust the tilt through remote control. This requires no onsite operations, thus cuts costs, and increases the efficiency.

Working Principles of the RET The RET system consists of four parts: antenna, remote control unit (RCU), splitter, and central control unit (CCU).

The RCU is the driver motor. One antenna needs one RCU. One CCU can control multiple RCUs. The splitter divides the control signals and power signals from the CCU to multiple branches and then sends them to multiple RCUs.

Figure 5-6 shows the functional structure of the RET.

Figure 5-6 Functional structure of the RET

BTS CCU SplitterRCU Antenna1

RCU Antenna2

…




5.2.5 Diversity The wave propagation has the following features:

The average value of the field strength varies slowly with place and time. Such variation, called slow fading, accords with the logarithmic normal distribution.

The instantaneous value of the field strength features a selective fading along the transmission paths. Its fading pattern, called fast fading, accords with the Rayleigh distribution.

Fast fading and slow fading variations affect the quality of mobile communication. In some cases, they may even lead to communication interruption. Diversity technology is one of the most effective measures against fast fading. Appropriate diversity reception and combination can effectively eliminate fading in signal transmission when the two channels of the fading signals share little correlation.

Diversity is categorized into polarization diversity and space diversity. The BTS3012 antenna subsystem can use the polarization diversity and space diversity at the same time.

The BTS3012 uses two antennas to implement diversity receive. Two omnidirectional antennas or two single polarization directional antennas can implement space diversity receive. One dual polarization directional antenna can implement polarization diversity receive.

Theoretically, for space diversity, if the distance between two antennas is over 10 wavelengths, the diversity effect is superior. The polarization diversity facilitates antennas installation and saves space. Therefore, it is being used widely.

5.3 Feeder To reduce the transmission loss between the feeder and antenna, Huawei BTS3012 adopts the low-loss RF cables. The specifications of main feeders are 7/8-inch and 5/4-inch. 1/2-inch super-flexible cables are used between:

Antennas and main feeders Antennas and TMAs Cabinets and lightning arresters

The lightning arrester in the BTS3012 antenna system is optional.

5.4 TMA The section describes the following aspects of the TMA:

Features Working Principles

5.4.1 Features The tower mounted amplifier (TMA) is a low noise amplification module installed on the tower top. The TMA is optional. The triplex TMA is usually used and installed close to the antenna. The triplex TMA consists of triplex filter, low noise amplification, and feeder.



The triplex filter can be considered as the combination of two duplex filters.

The signals received are processed by the TMA as follows:

The triplex filter filters the signals from the antenna to remove the outband interference. The low noise amplification amplifies the weak signals. The feeder transmits the amplified signals to the indoor units.

As the TMA compensates the loss of the BTS feeder, the noise coefficient must be low. As the strength of signals that the antenna receives changes according to the distance between the MS and the BTS, large dynamic range and alarm bypass are required. As the TMA feeds by the core of the receiving feeder, a feeder isolation device is required. Because the TMA is placed outdoor, it is waterproof, with the working temperature between –40 °C and +70 °C.

5.4.2 Working Principles The TMA amplifies the weak signals received by the antenna to improve the receiver sensitivity, improve the UL coverage, and reduce the transmission power of the MS, thus improving the voice quality.

Figure 5-7 shows the functional structure of the TMA.

Figure 5-7 Functional structure of the TMA

Lower noiseamplification

Sendingfilter

Receivingfilter

Bypass

DC

BTS

TMA

Feeder

Receivingfilter

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle 6 O&M Subsystem


6 O&M Subsystem

About This Chapter


Title Description

6.1 Introduction Introduces the functions of the O&M subsystem.

6.2 Hardware Structure Introduces the hardware structure of the BTS3012 O&M subsystem.

6.3 Software Structure Introduces the software structure of the BTS3012 O&M subsystem.

6.4 Functions Describes the functions of the BTS3012 O&M subsystem.

6 O&M Subsystem HUAWEI BTS3012 Base Station



6.1 Introduction The O&M subsystem performs remote operation and maintenance through the OMC and terminal operation and maintenance through the MMI. Both require support of the BTS O&M program.

The O&M program is the common control part of the BTS software. It is the core of the BTS O&M function. All other programs of the BTS have interfaces with the O&M program.

The functions of the O&M program are:

Downloading the BTS3012 software Initializing the BTS3012 Monitoring and managing the BTS3012 running status Collecting alarms Utilizing resources and tracing interface messages

6.2 Hardware Structure The BTS3012 O&M program runs on the DTMU. One end of the DTMU connects to the BSC and LMT, the other end connects to the boards.

The DTMUs work in active or standby mode. The boards manage, monitor, and control all the equipment of one BTS.

Figure 6-1 shows the hardware structure of the BTS O&M.

Figure 6-1 Hardware structure of the BTS3012 O&M subsystem

DTMU

BSC

MMI

DCOMDCOM DCOM

DDPUDDPU DDPU

DTMU DTMU

Low rate DCL

High rate DCL

DTRU

DTRU

DTRU

DTRU

DTRU

DTRU

High rate DCLHigh rate DCL

Low rate DCL Low rate DCL

High rate DCL

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle 6 O&M Subsystem


6.3 Software Structure The BTS3012 O&M program consists of the L3 module, modules of various link layers, the communication port I/O module, the common module, and the transmission equipment control module.

Figure 6-2 shows the software structure of the O&M subsystem.

Figure 6-2 Software structure of the BTS3012 O&M subsystem

LAPD High rate DCL Low rate DCL MMI

I/O I/O I/O I/O

Abis DAFU MMIStandby DTMU Extended DTMU

DTMU link

I/O

L 3

BIU

Transmissionequipment

control module

The BTS3012 O&M program performs the following functions:

Providing interfaces with all the other programs in the system. Adopting the message-oriented and data-structure-oriented designs which help to

enhance the system reliability and expandability. Performing sub-channel multiplexing and demultiplexing on the radio channels and

timeslot switching at the Abis interface or the BS interface. Monitoring the running status of the BIU module on the DTMU and reporting the status

through indicators on the DTMU or the O&M module.

6.4 Functions Table 6-1 lists the functions of the BTS3012 O&M subsystem.

Table 6-1 Functions of the BTS3012 O&M subsystem

Functions Description

Configuration management Manages the configuration of modules such as the DTRU and the DDPU.

Software download Downloads the software for the boards such as the DDPU and the NFCB.

Board in-position test Tests the in-position information for boards.

Warm backup The DTMUs uses the active/standby mode.

6 O&M Subsystem HUAWEI BTS3012 Base Station



Functions Description

Abis interface management Performs the E1 timeslots switching, L1 connection and signaling link L2 management, DBUS extension, and optimization of Abis bandwidth allocation strategy.

Fault management Manages faults for the DBUS and the CBUS2.

Transmission management Provides flexible ways of TS switching on the BIU to implement various networking modes.

Air interface management Configures the parameters for the physical channels and logical channels at the air interface, including the cell attribute, TRX attribute, and channel attribute.

Test management Manages the link test at the Abis interface, the DTRU channel test, and site/cell/TRX/board self-detection.

Status management Ensures that the states of the logical objects and physical objects of the BTS3012 are consistent in the BSC, DTMU, and boards.

Event report management Gives complete and correct reports in case of errors or alarms.

Alarm management Provides extended alarm branch number and alarm combination, shield, report of boards, modules, and environment according to alarm severity levels.

Equipment management Manages the software download, startup, and initialization, and alarms processing of boards

Site management Configures sites, physical boards, and dynamic data.

Interface tracing Traces the messages in the interfaces through the BTS log.

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle 7 System Signal Procedure


7 System Signal Procedure

About This Chapter


Title Description

7.1 DL Signal Flow Describes the downlink (DL) signal flow.

7.2 UL Signal Flow Describes the uplink (UL) signal flow of the UL services of the BTS3012.

7.3 Signaling Processing Flow Describes the signaling processing of the BTS3012.

7.4 Clock Signal Flow Describes the signal flow of the BTS3012 clock.

7.5 Combined Cabinet Signal Flow

Describes the signal flow of BTS3012 combined cabinets.

7 System Signal Procedure HUAWEI BTS3012 Base Station



7.1 DL Signal Flow Figure 7-1 shows the DL signal flow of the BTS3012.

Figure 7-1 DL signal flow

DTMU

DTRU

DDPU

Um

BSC

BTS3012 cabinet

MS

Abis

Antennasubsystem

The DL signal flow is as follows:

Step 1 The DTMU receives the service data from the BSC, exchanges and processes it, and then transfers it to the DTRU.

Step 2 The DTRU performs digital filtering, up conversion, and filter amplification of the signals and sends the signals to the DDPU.

Step 3 The duplexer in the DDPU filters the signals sent from the DTRU and transmits the signals through antennas and feeders.

----End

7.2 UL Signal Flow Figure 7-2 shows the signal flow of the UL services of the BTS3012.



Figure 7-2 UL signal flow

DTMU

DTRU

DDPU

Um

BSC

BTS3012 cabinet

MS

Abis

Antennasubsystem

The UL signal flow is as follows:

Step 1 The antenna receives the signals transmitted from the MS. After being amplified by the TMA, the signals are transmitted to the DDPU through the feeder. The TMA is optional. It is used to compensate the feeder loss and enhance receiver sensitivity of the DDPU antenna port.

Step 2 The DDPU receives the signals and transmits the signals to the DTRU after they are filtered by the duplexer and amplified by the LNA.

Step 3 The DTRU receives the signals and transmits the signals to the DTMU after amplification and down conversion. The DTMU then transmits the signals to the BSC through the Abis interface.

----End

7.3 Signaling Processing Flow Figure 7-3 shows the signaling processing flow of the BTS3012.

7 System Signal Procedure HUAWEI BTS3012 Base Station



Figure 7-3 Signaling processing flow

BTS3012 cabinet

DDPUDTRUDTMU

BSCAbis

The signaling processing flow is as follows:

Step 1 The Abis interface board receives the signaling data from the BSC and transmits the data to the DTMU.

Step 2 The DTMU performs decision and processing on the signaling and transmits the signaling to the DTRU and DDPU.

Step 3 The DTRU and DDPU report board status to the DTMU.

Step 4 The DTMU obtains the status of the BTS3012 by collecting and analyzing the status of all boards and transmits the information to the BSC through the Abis interface.

----End

7.4 Clock Signal Flow Figure 7-4 shows the signal flow of the BTS3012 clock.

Figure 7-4 Clock signal flow

DTMUBoards in themain cabinet

Boards in theextension cabinet

AbisClock distribution

cable betweencabinets

The clock signal flow is as follows:

Step 1 The external reference clock is transmitted to the clock module in the DTMU through the Abis interface.



Step 2 The clock module performs phase lock and frequency division on the clock signals to generate different clock signals for BTSs.

Step 3 The clock signals are transmitted to the modules in the main cabinet such as the DTRU and the DDPU.

Step 4 The clock signals are transmitted to the modules in the extension cabinets through the clock distribution cable.

----End

7.5 Combined Cabinet Signal Flow Figure 7-5 shows the signal flow of the BTS3012 combined cabinet.

Figure 7-5 Combined cabinet signal flow

Maincabinetin themain

cabinetgroup

Maincabinetin themain

cabinetgroup

Maincabinet in

theextensioncabinetgroup

Data cable

Clock cable

Control cableClock cable

Control cableData cable

Clock cable

Control cable

Extensioncabinet in

theextensioncabinetgroup

The connection of the signal cables between combined cabinets is as follows:

The main and extension cabinets are connected by the data cables, control cables, and clock cables.

The main and extension combined cabinets are connected by the clock cables and control cables.

The main and extension cabinets and combined cabinets require the DIP switches.

HUAWEI BTS3012 Base Station Technical Manual - Architecture and Principle 8 Configuration and Networking


8 Configuration and Networking

About This Chapter


Title Description

8.1 Configuration of the BTS3012

Describes the configuration principles, configuration features, and capacity of the BTS3012.

8.2 Board Configuration Describes the configurations of the BTS3012 boards.

8.3 Typical Configuration Takes site configurations S4/4/4 and O6 (omnidirectional cell with six TRXs) as an example to show configuration methods.

8.4 Networking Types Lists different network topologies of the BTS3012.

8 Configuration and Networking HUAWEI BTS3012 Base Station



8.1 Configuration of the BTS3012 This section describes the configuration of the BTS3012.

It has the following parts:

Configuration Principles Configuration Features System Capacity

8.1.1 Configuration Principles Table 8-1 lists the configuration principles of the BTS3012 cabinet.

Table 8-1 Configuration principles

Number of TRXs in the Site Configuration

< 12 Single cabinet

12–24 Combined cabinets

> 24 Cabinet group

The following configuration principles are also applied:

The minimum antenna rule Use minimum number of antennas for cell configuration.

The minimum cabinet rule Use minimum number of cabinets for cell configuration.

The complete synchronous cell rule All TRXs of a synchronous cell are configured in the same cabinet group.

The basic cabinet priority rule TRXs are configured in the basic cabinet in preference, and the number of TRXs in the basic cabinet is not less than that in any extension cabinet.

8.1.2 Configuration Features The configuration of the BTS3012 is as follows:

The BTS3012 supports the omnidirectional coverage and the directional coverage. The BTS3012 supports the combination of two cabinets to form one group and the

combination of three cabinet groups. The BTS3012 supports the transmit diversity and 4-way diversity receive. In regular configuration, three sectors need three DDPUs. The DCOM combines two carriers into one channel (the 2-in-1 function). The DCOM is

required when the DTRUs are not sufficient.



8.1.3 System Capacity The capacity of the BTS3012 is as follows:

The BTS3012 uses DTRU. One single cabinet supports up to 12 TRXs under full configuration.

One BTS3012 supports up to six cells. The BTS3012 supports the omnidirectional cell and the sectorized cell. The maximum

site configuration is 36 TRXs. The maximum number of carriers is eight in a cell with a pair of dual polarization

antennas or two omnidirectional antennas of a single sectorized cell. One site supports up to 36 TRXs.

8.2 Board Configuration This section describes the configuration of the BTS3012 boards.

The boards are:

DTRU DAFU DTMU DCCU DCSU DEMU DATU NFCB DMLC DELC DSAC

8.2.1 DTRU One BTS3012 cabinet can be configured with up to six DTRUs.

The features of the DTRU are as follows:

One DTRU has two TRXs. The output power of each TRX can be configured flexibly when the DTRU supports two

TRXs.

8.2.2 DAFU The DAFU subrack consists of the DDPU module and the DCOM module. The DDPU and the DCOM can be placed in each other's slots.

Under full configuration, the subrack consists of maximum six boards. There are maximum six DDPUs. The DCOM is used only when the cell is configured with more than four carriers.




The interfaces of the DDPUs and the DCOMs are on the front panel. The boards of the DAFU subrack connect with other boards or units in the cabinet through cables.

8.2.3 DTMU The DTMU is placed in slots 0 and 1 of the common subrack. The number of the DTMU under full configuration is two and in minimum configuration is one.

The main features of the DTMU are as follows:

Working in the active/standby mode Providing four or eight E1 connections Near-end MMI maintenance with 10 Mbit/s network port Supporting 8-route digital alarm input. Two routes are lightning arrester failure alarm

detection Supporting 4-route extended digital control signal output

8.2.4 DCCU The DCCU is placed in slot 6 of the common subrack. The DCCU is mandatory. Only one DCCU is required.

The DCCU has no active parts. It only performs signal transfer without board power calculation.

8.2.5 DCSU The DCSU is placed in slot 5 of the common subrack. It is mandatory and only one DSCU is required.

The DCSU transfers signals for the combined cabinet.

8.2.6 DEMU The DEMU is placed in slot 2 in the common subrack..

The DEMU is optional built-in module. The number of the DEMU under full configuration is one.

8.2.7 DATU The DATU is placed in the slots 2, 3, 4, and 7 of the common subrack. It can be placed in the slots of the DEMU or other extended functional boards.

The DATU is optional built-in module. The number of the DATU under full configuration is two.

8.2.8 NFCB The NFCB is placed in the FAN subrack. It is mandatory. The number of the NFCB for full configuration is one.



8.2.9 DMLC The DMLC is placed in slot 0 to slot 2 of the cabinet top subrack. It can be placed in the DELC slot. .

The DMLC is optional. The number of the DMLC under full configuration is one.

8.2.10 DELC The DELC is placed in slot 0 to slot 2 of the cabinet top subrack. It can be placed in the DMLC slot.

The DELC is mandatory. The number of the DMLC under full configuration is three and in minimum configuration is one.

8.2.11 DSAC The DSAC is placed in slot 3 of the cabinet top subrack. It cannot be placed in the slots of the DMLC or the DELC.

The DSAC is mandatory. The number of the DMLC under full configuration is one.

8.3 Typical Configuration The following takes the site configuration S4/4/4 (three directional cells, each cell having four TRXs) and O6 (omnidirectional cell with six TRXs) as an example to show the configuration method.

8.3.1 S4/4/4

Configuration of Antenna Parts Antenna

Each cell is configured with two sets of single polarization antennas. A total of six such antennas are required for the three cells. Alternatively, cell is configured with one set of dual polarization antenna, and three sets of such antennas are required for the three cells.

RF cable set The BTS S4/4/4 configuration cables are used.

Configuration of Cabinet Only one cabinet is required for the S4/4/4) configuration, as shown in Figure 8-1.




Figure 8-1 Cabinet configuration in an S4/4/4 site

Wiring & Air Inlet

Wiring

DDPU

DDPU

DTRU

DTRU

DTRU

DTRU

DTRU

DTRU

Wiring

FAN

Air Inlet

DMLC

Power and EMC

Transmission Unit

DDPU

DELC

DELC

DSAC

Transmission Unit

DTMU

DTMU

DEMU

DCCU

DCSU

DATU

8.3.2 O6

Configuration of the Antenna Parts Antenna

Two sets of single polarization antennas are configured, both of which are receiving/transmitting antennas. Alternatively, one set of dual polarization antenna is configured.

RF cable set The BTS O6 configuration cables are used.



Configuration of Cabinet Figure 8-2 shows the cabinet configuration of BTS.

Figure 8-2 O6 cabinet configuration

Wiring & Air Inlet

Wiring

DDPU

DCOM

DTRU

Wiring

FAN

Air Inlet

DMLC

Power and E MC

Transmission Unit

DELC

DELC

DSAC

Transmission Unit

DTMU

DTMU

DEMU

DCCU

DCSU

DATU

DTRU

DTRU

8.4 Networking Types This section contains the following topics:

Transmission Mode Networking Modes Principles of Networking




Star Networking Chain Networking Tree Networking Ring Networking

8.4.1 Transmission Mode The BTS3012 allows for flexible networking modes with multiple built-in transmission functions. It supports transmission modes such as E1 and STM-1. It also supports satellite and microwave transmission.

8.4.2 Networking Modes The networking mode can be as follows:

Star Networking Chain Networking Tree Networking Ring Networking

8.4.3 Principles of Networking When the transmission traffic is within the allowed limit, E1 transmission is adopted.

Chain networking and tree networking are not preferred as the two networking modes affect the usage of the transmission bandwidth of the upper-level BTSs, thus affecting the reliability of the lower-level BTSs.

8.4.4 Star Networking

Application Scenario The star networking is commonly used. In densely populated cities, this networking is quite popular.

Figure 8-3 shows the star networking.

Figure 8-3 Star networking

BTS

BSC

BTS

BTS



Advantages In the star networking, every SITE directly connects to the BSC with E1. This facilitates the maintenance, construction, and capacity expansion of the network.

Because the signals are directly transmitted to the BSC, the reliability of the link is improved.

Disadvantages Compared with other networking modes, star networking requires much more transmission cables.

8.4.5 Chain Networking

Application Scenario The chain networking is suitable for the belt-shaped loosely populated areas, such as highways and railways.

Figure 8-4 shows the chain networking.

Figure 8-4 Chain networking

BTSBSC BTSBTS

Advantages The chain networking can reduce cost in transmission equipment, construction, and transmission link lease.

Disadvantages The chain networking has the following disadvantages:

Because signals travel many nodes, the transmission reliability is low. Faults in the upper-level BTSs may affect the lower-level BTSs. The number of levels in a chain network cannot exceed five.

8.4.6 Tree Networking

Application Scenario Tree networking is suitable for the complicated networks and sites such as vast areas with centralized hotspot and small areas with a lot of intersections.

Figure 8-5 shows the tree networking.




Figure 8-5 Tree networking

BTS

BSC

BTS

BTS

BTS

Advantages The number of transmission cables that the tree networking requires is less than that the star networking requires.

Disadvantages The tree networking has the following disadvantages:

Because signals travel many nodes, the transmission reliability is low. It is difficult for maintenance and engineering. Faults in the upper-level BTSs may affect the lower-level BTSs. Capacity expansion is difficult. The number of levels in the tree cannot exceed five.

8.4.7 Ring Networking

Application Scenario The ring networking is commonly used. With good self-healing capability, ring networking must be used as much as possible.

Figure 8-6 shows the ring networking.



Figure 8-6 Ring networking

BTSBSC BTSBTS

Advantages The ring networking has strong self-healing capability. If a point of the link breaks, the ring network can break into a chain network, and the service is not interrupted.

In practice, the above several networking modes are used together. Using the networking mode reasonably can improve the service quality and save the investment on the transmission equipment.

BTS 3012

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