CDMA-3GCN I 01 200904 Principle of Telecommunication

3GCNCDMA2000 Core Network

Training Material

Principle of Telecommunication

ZTE UNIVERSITYZTE University, DameishaYanTian District, Shenzhen,P. R. China518083Tel: (86) 755 26778800Fax: (86) 755 26778999URL: http://ensupport.zte.com.cnE-mail: [email protected]

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Publishing Date (MONTH/DATE/YEAR) : 07/20/2009

Contents

1 Overview of Signaling Network and Voice Network ...............................................................1

1.1 Signaling Network..............................................................................................................1

1.1.1 Network Level Structure ..........................................................................................1

1.1.2 Functions of Signaling Points ..................................................................................1

1.2 Voice Network....................................................................................................................2

2 CDMA Overview .........................................................................................................................5

2.1 Development of Wireless Communication.........................................................................6

2.1.1 The First Generation Analog Cellular Mobile Communication .................................6

2.1.2 The Second Generation Digital Cellular Mobile Communication .............................6

2.1.3 The Third Generation Mobile Communication - IMT2000........................................8

2.2 Basic Concepts of CDMA ................................................................................................10

2.2.1 Multiple Accesses Technology ...............................................................................10

2.2.2 CDMA-related Concepts........................................................................................12

2.3 CDMA Features ...............................................................................................................13

3 CDMA Network Architecture ...................................................................................................17

3.1 System Architecture.........................................................................................................17

3.2 An Introduction to Network Entities..................................................................................19

3.2.1 BTS Subsystem.....................................................................................................19

3.2.2 Mobile Switching Subsystem.................................................................................19

3.2.3 Operation and Maintenance Management Subsystem (OMM)..............................21

3.3 Interfaces and Protocols ..................................................................................................22

3.3.1 Interfaces...............................................................................................................22

3.3.2 Interface Protocols.................................................................................................24

4 Numbering Plan .......................................................................................................................29

4.1 Numbering Plan...............................................................................................................29

4.2 MDN ................................................................................................................................29

4.3 IMSI and MIN...................................................................................................................30

4.4 Equipment Number..........................................................................................................31

4.5 Temporary Local Directory Number (TLDN) ....................................................................31

4.6 Electronic Sequence Number (ESN) ...............................................................................31

5 CDMA Key Technologies.........................................................................................................33

5.1 Basic Concept .................................................................................................................33

5.1.1 Walsh Code ...........................................................................................................33

5.1.2 Pseudo-random Sequence Number ......................................................................33

5.1.3 Number Application ...............................................................................................35

5.1.4 Number-based Channels.......................................................................................35

5.2 Key Technologies ............................................................................................................36

5.2.1 Power Control Technology.....................................................................................36

5.2.2 Diversity Technology..............................................................................................38

5.2.3 Handoff Technology...............................................................................................38

5.2.4 Voice Coding Technology ......................................................................................41

5.2.5 Channel Modulation Technology............................................................................41

5.2.6 Soft Capacity .........................................................................................................43

6 Services and Functions ..........................................................................................................45

6.1 CDMA Services ...............................................................................................................45

6.1.1 Telecommunications Services ...............................................................................45

6.1.2 Supplementary Services........................................................................................45

6.1.3 WIN Service ..........................................................................................................47

6.1.4 Value-added Service .............................................................................................47

6.2 Network Functions...........................................................................................................47

6.2.1 Network Functions for Supporting Services ..........................................................47

6.2.2 Network Functions for Supporting the Running of the Cellular System.................48

6.2.3 Additional Network Functions for Call Processing .................................................49

6.2.4 Authentication Function.........................................................................................49

6.2.5 Roaming Function between Different Modes ........................................................49

6.2.6 International Roaming ...........................................................................................49

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CDMA-3GCN_I_01_200904

Principle ofTelecommunication

After you have completed this course, you will be able to:>> Know the overview of signaling network and voice net-

work.

>> Know the CDMA overview.

>> Master CDMA network architecture.

>> Know the numbering plan.

>> Know the CDMA key technologies.

>> Know the services and functions.

1

1 Overview of Signaling Network and Voice Network

Key Points

Signaling network

Voice network

1.1 Signaling Network

1.1.1 Network Level Structure

The SS7 signaling network adopts a three-level structure, consisting of

HSTP, LSTP. and SP. The two-level structure is also can adopted,

consisting of HSTP&LSTP and SP. The structure is shown in Figure 1.1-1.

HSTP&LSTPFirst-level HSTP

Second-level

LSTP

Third-level SP SP

Figure 1.1-1 Structure of SS7 Signaling Network

The signaling points of the CDMA network consists of MSC, VLR, HLR,

authorization center, service control point and the mobile special service

center.

1.1.2 Functions of Signaling Points

The HSTP (high-level signaling transfer point) transfers the signaling

CDMA-3GCN_I_01_200904 Principle of Telecommunication

2

messages of the second-level LSTP (low-level signaling transfer point)

and the third-level SP it connects to. HSTP should adopt the stand-alone

signal transfer point (STP) devices, and provides the functions required

by MTP, SCCP, TC and OMAP.

LSTP is the second-level STP, which transfers the signaling message of

the third-level SP connected with it. An LSTP can be independently set

up, or set up together with an SP. LSTP is implemented by stand-alone

STP devices, or the integrated STP devices combined with SP. When the

stand-alone STP devices are adopted, LSTP meets all the function

requirements of HSTP. With integrated STP devices, LSTP meets all the

function requirements of the stand-alone STP, and the function

requirements of ISUP and MAP in the No .7 signaling mode.

The third-level SP is the source or destination in the signaling message

transfer of the signaling network. Based on different functions, it should

meet the function requirements of MTP, TUP, ISUP, SCCP, TC, MAP and /

or OMAP.

1.2 Voice Network

The digital mobile communication network adopts a three-level structure,

namely, TMSC1, TMSC2 and local MSC.

In a large region, TMSC1 is established, and different TMSC1s are

connected like a mesh. In a province, one or two TMSC2s are

established, and TMSC2s are connected with the associated TMSC1. The

whole network is divided into several local MSCs, and each local MSC

has one or several MSCs which are connected with associated TMSC2.

The connection is shown in Figure 1.2-1.

The mesh networks at the same level are connected, as shown in Figure

1.2-2.

Chapter 1 Overview of Signaling Network and Voice Network

3

TMSC1

Local MSC

TMSC2

Figure 1.2-1 Three-Level Voice Network Structure

TMSC1

TMSC1

Figure 1.2-2 Mesh Network Connection


4


5

2 CDMA Overview

Key points

The development history and trend of mobile communication

What is CDMA system?

CDMA features.

The objective of mobile communication is to implement communication

at any time, any place and between any people.

The wireless mobile communication technology is basically focused on

the innovative development of mobile communication bands, reasonable

and efficient use of frequency resources, as well as compact, light and

multifunctional design. Ever since 1970s when the “Cellular” theory was

sponsored by the Bell laboratory in America, cellular communication has

been widely used. Theoretically, the essence of the cellular system is to

repeatedly use wireless channels in different geographic locations, which

is frequency division multiplexing. Divide the service area into a number

of abstract hexagonal cellular cells, while two nonadjacent cells use the

same frequency. The cell size is determined according to the user

density. In this way, spectrum utilization can be greatly enhanced and

the system capacity can thus be effectively raised. Meanwhile, based on

the development of microelectronic technology, computer technology,

communication network technology, signal coding technology and digital

signal processing technology, the development of mobile communication

has gained a great leap forward on such aspects like switching, signaling

network system and wireless modulation and coding technology. Thus,

the cellular mobile communication system has experienced a series of

changes, from analog to digital, from Frequency Division Multiple Access

(FDMA) to Time Division Multiple Access (TDMA) and Code Division

Multiple Access (CDMA), and the evaluation from the first generation

cellular mobile communication system to the third generation mobile

communication system.


6

2.1 Development of Wireless Communication

2.1.1 The First Generation Analog Cellular Mobile Communication

In late 1970s, the first generation cellular mobile communication system

was developed on the basis of the cellular networking technology. It

created the first case for the commercialization of cellular mobile

communication system. The first cellular system AMPS (Advanced Mobile

Phone Service) was realized in Chicago in 1979. During the same period,

other systems were also under development, including TACS in UK and

NMT in North Europe.

The first generation communication featured FDMA and analog

modulation (FM). Voice transmission was achieved through analog

signals. It was restricted by a series of factors, such as low frequency

unitization, small capacity, lack of unified international standards and

effective anti-interference / anti-attenuation measures, complicated

equipment, high cost, poor voice quality and security. Apart from this, it

required a protection band and could be intercepted easily by number

cloning. The number of subscribers was also limited. Non-voice and

digital communication services were impossible. Therefore, it could not

satisfy the requirements of market development. These fatal

disadvantages hindered its further development and it was inevitably

replaced by digital cellular mobile communication step by step.

2.1.2 The Second Generation Digital Cellular Mobile Communication

Developed in the 1990s, the mobile phone system featuring TDMA and

narrow-band CDMA is called as the second generation mobile

communication system. There are two typical product categories:

2.1.2.1 TDMA system

The major feature of TDMA series products is the adoption of TDMA and

FDMA technologies to implement mobile communication. The mature

and representative systems include Pan-European GSM, American

D-AMPS and Japanese PDC. Their common features were presented by

digitalization, TDMA, better voice quality, excellent security, data

transmission capability and the function for automatic roaming. Each of

Chapter 2 CDMA Overview

7

them had their own advantages and shortcomings: The PDC system

uses high spectrum utilization, but only available in Japan. The D-AMPS

system has the largest capacity but its equipment is very complicated.

The GSM technology maturity is based on open standards and widely

used around the world.

2.1.2.2 N-CDMA system

The CDMA wireless technology is an innovative digital cellular technology

developed after the communication technologies like GSM. The N-CDMA

series is the narrowband CDMA based on IS-95 and developed under the

sponsorship of Qualcomm.

Featuring digital transmission was based on a series of key technologies,

including spreading communication, power control, soft capacity, soft

handoff, voice activation; voice coding, multiple access, diversity

receiving and RAKE receiving. Hence the CDMA system has obtained

more advantages and has pushed the mobile communication technology

to a new development stage.

The advanced technologies have granted the CDMA system with

overwhelming advantages over the TDMA system, such as high

spectrum utilization, wide coverage, large system capacity, simple

frequency planning, high voice quality, fine anti-resistance, small

radiation power, power saving, long standby time, strong penetration

capability, excellent indoor coverage, high security and excellent

prevention against number cloning.

The development of CDMA is a progressive process. Most commodities

available on the market are developed on the basis of the IS-95A

narrowband N-CDMA technology. This system features low cost, high

quality, interconnection, supports IP and data services, implements

Wireless Intelligent Network (WIN) service and provides convenient and

efficient communication services to users. On the aspects of

communication technologies and people’s requirements, the future

wireless communication world will be a broadband-based, integrated

data and multimedia network. The broadband CDMA technology will be

an important support to this network.


8

2.1.3 The Third Generation Mobile Communication - IMT2000

2.1.3.1 Development Motive of the Third Generation Cellular Mobile Communication System

Represented by AMPS and TACS, the first generation cellular mobile

communication system provided a solution to mobile conversation and

greatly satisfied the requirements of terminal users, but many problems

existed in this system. For example, poor conversation quality, low

spectrum utilization and security and so it was replaced by the second

generation cellular mobile communication system represented by GSM

and IS95. Compared to the first generation, great improvement was

achieved in terms of conversation quality, spectrum utilization, security

and confidentiality. It satisfied people’s requirements in a certain period.

Along with the continuous development of mobile communication and

the expansion of mobile communication scale, the disadvantages of the

second generation were also exposed gradually.

1. Insufficient radio frequency resources

The rapid increase of mobile terminal users made the frequency

resources of the system relatively insufficient. The development of

mobile communication surprisingly exceeded expectations. To

expand system capacity, the cell of some central cities was shrunk

less than 500 meters in diameter that resulted in frequent handoff

and serious interference and thus the conversation quality became

fairly poor.

Low frequency utilization was another key reason for frequency

resource insufficiency. Compared to the first generation mobile

communication, the second generation raised the frequency

utilization, but compared with the third generation with the CDMA

technology as the core; its frequency utilization is still very low.

2. Unable to meet the requirements for new services

The second generation features the voice-oriented design, with its

main objective focused on providing quality and efficient voice

services. Along with the development of the Internet and electronic

commerce, data service will become the main stream. In the future,


9

various broadband information services such high-speed data,

low-speed image and television will become the application used

most frequently by terminal users. But the second generation was

designed mainly for voice services, which cannot provide high-speed

data service.

2.1.3.2 Third Generation Cellular Mobile Communication System

This system (3G) is also called as IMT-2000, which means that its

working band is 2000MHz and its highest service rate can go up to

2Mbit/s. Based on the broadband W-CDMA technology, it is a multimedia

and intelligent system that is able to raise multiple transmission rates,

integrate terrestrial cellular system, cordless system, cellular mobile

communication system and satellite system, and thus implement global

services in real sense. It provides a centralized platform for the

integration and allocation of various services. The 3G system has three

main features:

1. Seamless Global Roaming.

2. High-speed transmission; High-speed mobile environment: 144kbit/s;

Walking slow-speed mobile environment: 384kbit/s; Indoor still

environment: 2Mbit/s.

3. Seamless service transfer, namely, service interworking is available

among fixed network, mobile network and satellite network.

2.1.3.3 Evolution from 2G to 3G

As described above, two development directions are undergoing. Figure

2.1-1shows the evolution of the N-CDMA system based on IS-95A to the

3G system.


10

IS 95-A 14.4kb p s

IS 95-B64kb p s

cd m a2000 1XP h ase I 144kb p s

cd m a2000 1X E V D O P h ase II 2M b p s

2 G 3 G

Figure 2.1-1 Evaluation from 2G to 3G

IS-95A embedded the IP protocol in the mobile station, so the network

does not require additional IP layer on the packet transmission layer. In

this way, the hardware will be compatible with all subsequent standard

networks based on the IP. The data transmission rate of the IS-95A

network is 14.4kbit/s; In the IS95-B network, the data transmission rate

is raised to 64kbit/s through core network and wireless network

upgrading. A set of data basic equipment is added to the Base Station

Controller (BSC) to promote the CDMA system into a packet mode

network. CDMA2000 1X is the first stage of CDMA2000. It has effectively

doubled the original voice capacity and raised the data transmission rate

to 144kbit/s. It may provide a typical rate of 130kbit/s for terminal

users. CDMA2000 1XEVDV is the second stage of CDMA2000. It

intended to integrate the capability of the first stage to the same carrier

and still maintain the capability of packet data service transmission at

the split carrier. In this stage, three modes of services are provided:

realtime, non-realtime and combined realtime/non-realtime. 2Mbit/s

data transmission rate can also be provided in this stage.

2.2 Basic Concepts of CDMA

2.2.1 Multiple Accesses Technology

It is known that the first concern of any transmission system is how to

establish channel connection between terminal users within the network


11

and within the electric wave coverage of the wireless communication

environment. The essence of this problem is multi-access mobile

communication. Currently this mode is used by FDMA in the analog

system, TDMA and CDMA in the digital system. The theoretical basis of

multi-access connection implementation is the signal splitting technology,

namely, implementing appropriate signal design at the sending end, so

that the signals sent from individual stations are different and while the

receiving end has the identifying capability to detach and select the

corresponding signal from the combined signals.

FDMA stands for Frequency Division Multiple Access. In this case, signal

power is centralized to a relatively narrow channel in frequency domain

for transmission. Different signals are allocated to channels of different

frequency. Interference to and from adjacent channels is restricted

through bandpass filter. So, only the energy for useful signals is allowed

through the specified narrow channel, while signals of other frequencies

are excluded out.

TDMA stands for Time Division Multiple Access. One channel consists of

a series of periodic timeslots. The energy for different signals is assigned

to a different timeslot. Interference from adjacent channels can be

restricted through timed channel selection. Only the energy for useful

signals is allowed through the specified timeslot.

CDMA stands for Code Division Multiple Access. Each signal is assigned

with a pseudo-random binary code for spreading. The energy for

different signals is assigned to a different pseudo-random sequence. In

the receiver, signals are detached with a correlator. The correlator only

receives selected binary sequence and compresses its spectrum. The

bandwidth of any signals mismatching the binary sequence of this user

will be compressed. As a result, only the information of useful signals

can be identified and extracted.

Figure 2.2-1 illustrates the correspondence among FDMA, TDMA and

CDMA in frequency domain and time domain.


12

FDMA TDMA CDMA

Figure 2.2-1 FDMA, TDMA and CDMA Time Domain and Frequency Domain

2.2.2 CDMA-related Concepts

CDMA is based on the frequency spreading technology, namely,

modulating the information data of certain signal bandwidth to be sent

with a high-speed pseudo-random code whose bandwidth is far greater

than the signal bandwidth, so that the bandwidth of the original data

signal can be spread and then sent out via carrier modulation. Using the

same pseudo-random code, the receiving end completes the correlated

processing, converts the broadband signal into the original narrowband

signal of the original information data (namely dispreading) and

implements information communication.

Note

The spreading technology means converting the bandwidth of the

original signal to a much wider bandwidth for transmission in order to

enhance the anti-interference feature of the communication system. The

mathematical model is based on the Shannon formula in the information

theory. In the case of white noise interference, the channel capacity is:

C = B log2(1 + S / N)

B: channel bandwidth; S: signal average power; N: noise average

power;

C: channel capacity.

The above formula shows: Even if the signal-noise ratio (S/N) is low,

increasing the bandwidth B can still ensure high quality communication

without lowering system capacity.

Time TimeFrequency

Frequency Time Frequency


13

CDMA is a self-interference system. All users occupy the same

bandwidth and frequency. Its working mechanism can be illustrated with

a contract example.

Let us assume that bandwidth is analogous to a big house, and there

are a large number of people present in the house speaking different

languages. They can hear their companion’s voices but also suffer

interference from conversations of other people. In this house, the air

can be imagined as the broadband’s carrier, while the different

languages can be regarded as codes. If the number of people is steadily

increased over time, we can reach at a time when we are overwhelmed

by the background noise. If the signal strength of other users can be

controlled, more users can be accommodated and high conversation

quality can be ensured at the same time.

2.3 CDMA Features

The CDMA mobile communication network is combined through multiple

technologies such as spreading, multiple accesses, cellular networking

and frequency reuse. It is the coordination of three-dimension signals

among frequency domain, time domain and code domain. Therefore it

features excellent performance against interference and multi-path

attenuation, high confidentiality and security. The same frequency can

be reused in multiple cells. Its carrier-to-interference ratio (C/I) is

smaller than 1. Trade-off optional is available between capacity and

quality. These attributes grant the CDMA system with very important

advantages over other systems.

1. Wide coverage

In the mobile communication system field, a comparison between

CDMA and GSM systems may reveal that the coverage radius of the

former is theoretically 2 times of that of a standard GSM system. To

cover 1000 km2, only 50 BTSs are required in the CDMA system, but

200 BTSs are needed in the GSM system. Less BTSs for the same

coverage means a big decrease of equipment investment for

network operators.


14

2. Large capacity

In the same spectrum utilization, the capacity of CDMA is 4-5 times

of that of GSM or 10 times of that of an analog network.

3. High voice quality

The CDMA system ensures high voice quality. The noise chip can

dynamically adjust the data transmission rate and select a different

level for transmission, according proper threshold. Meanwhile the

threshold may change according to the background noise level.

Therefore, good conversation quality can still be ensured even in the

case of high background noise. The voice quality provided by the 8K

code of CDMA’s variable noise chip is no worse than the 13K code of

GSM. The 13K code provides voice service almost as good as wired

telephone and can even do better than wired telephone on the

aspect of background noise. Meanwhile, the soft handoff technology

is integrated in the system, which means “First connect then

disconnect”, so the defect “easy call failure” of hard handoff is

completely avoided.

Note

Soft handoff is the handoff of a terminal at the same frequency but

between different channels. The channel handoff within the same

BTS between different sectors is called as softer handoff. To the

opposite, the handoff at different frequencies and between different

channels is called as hard handoff.

4. Green mobile phone

In the CDMA system, different power control technologies are used,

so the average power is decreased a lot compared to that of the

GSM system and the radiation is also lowered, which ensures that

the system can be used safely.

5. High frequency utilization

In the CDMA system, different pseudo-random codes are used for

user signal modulation. On the aspects of frequency domain, the

spectrum of all signals are overlaid, therefore the spectrum


15

utilization is very high.

6. Simple frequency planning and easy expansion

Users can be identified according to different sequence codes,

therefore, different CDMA carriers can be used in adjacent cells and

the network can be flexibly planned and easily expanded.

7. Secure connectivity

8. Excellent performance against interference and multi-path

attenuation


16


17

3 CDMA Network Architecture

Key points

The basic architecture and some functions of the CDMA network.

Descriptions of individual interfaces and the information transferred

over them.

Protocols related with the CDMA network.

3.1 System Architecture

The CDMA cellular mobile communication system consists of four

independent subsystems: Mobile Station (MS), Base Transceiver

Subsystem (BSS), Mobile Switching Subsystem (MSS) and Operation &

Maintenance Subsystem (OMM). MS and BSS can communicate directly,

while the communication between BSS and MSS is implemented through

the standard A interface. Other interfaces, such as B, C, D, E, H, M, N, O

and P represent the interfaces among the functional entities. When

different functional entities are configured in each physical unit, some

interfaces will become internal interfaces that may not follow the unified

interface standard. Ai, Di and Pi are the system’s interfaces to

interconnect with other communication networks. Figure 3.1-1shows the

architecture and interfaces of the CDMA system:


18

MSCA AiBSCBTS Abis

MS

OMC HLR

C

Um

AUC H

Q Q

D VLR

B

VLR

G

SC

N

SCSMESME M M M

PSTN

PSPDN

ISDN

Pi

Di

EIR IWFMSC

F LE

Figure 3.1-1 Network Architecture of the CDMA Cellular Mobile Communications

System

BSC Base Station Controller Base station controller

BTS Base Transceiver Station Base station transceiver

MSC Mobile services Switching Center MSC

OMC Operation and Maintenance

Center

Operations & maintenance

center

AUC Authentication Center Authentication Center

EIR Equipment Identification Register Equipment Identification

Register

HLR Home Location Register HLR

VLR: Visitor Location Register VLR

MS Mobile Station Mobile station

ISDN Integrated Services Digital

Network

Integrated service digital

network

PSTN Public Switched Telephone

Network

Public Switching Telephone

Network

PSPDN Public Switched Public Data

Network

Public Switched Public Data

Network

PLMN Public Land Mobile Network Public land mobile network

SC Short Message Center Short message center

Chapter 3 CDMA Network Architecture

19

3.2 An Introduction to Network Entities

3.2.1 BTS Subsystem

The BTS Subsystem (BSS) is the assembly of radio equipment and radio

channel control equipment, serving one or more cellular cells. In certain

radio coverage, it is controlled by the Mobile Switching Center (MSC) to

implement channel assignment, user access and paging, and

information transfer. Normally, the BSS consists of one or more BSCs

and BTSs. The BTS is responsible for radio transmission and BSC for

control and management.

3.2.1.1 Base Transceiver

The Base Transceiver (BTS) belongs to the radio part of a base station

system. Controlled by BSC, it serves the radio transceiving equipment of

a certain cell, implements the conversion between BSC and radio

channels, radio transmission through air interface between BTS and MS

and related control, and communicates with BSC through the Abis

interface.

3.2.1.2 Base Station Controller

One end of the Base Station Controller (BSC) can be connected with one

or more BTSs, while its other end can be connected with MSC and OMC.

Oriented to radio network, BSC implements radio network management,

radio resource management and radio BTS monitoring and management.

It also controls the establishment, connection and disconnection of radio

connection between MS and BTS, controls the positioning, handoff and

paging of MS, provides voice coding and rate adjustment and carries out

operation and maintenance of the BSS.

3.2.2 Mobile Switching Subsystem

The Mobile Switching Subsystem (MSS) implements the main switching

functions of the CDMA network. Meanwhile it manages the database for

user data and mobility.

3.2.2.1 Mobile Switching Center

MSC is the core of the CDMA network. It controls and implements voice


20

channel connection for MSs within its coverage, namely serving as an

interface between CDMA and other networks. The functions MSC carries

out include call connection, charging, BSS-MSC handoff, assist radio

resource management and mobility management. Besides, each MSC

also implements the GMSC function for call route establishment to the

MS, namely, to query the location information of each MS.

MSC gets all data required for call request processing from three

databases, VLR, HLR and AUC.

3.2.2.2 Visitor Location Register

The Visitor Location Register (VLR) is a dynamic user database, storing

the related user data of all MSs (visitors) within the MSC’s management

range, including user ID, MS’s location area information, user status and

services available for the user.

VLR gets and stores all necessary data from the HLR of a mobile

subscriber. Once the mobile subscriber leaves the control area of the

VLR, it will be registered in another VLR, and the previous VLR will

delete its data log.

3.2.2.3 Home Location Register

The Home Location Register (HLR) is a static database, storing the data

for mobile subscriber management. Each mobile subscriber should be

registered in its HLR. It stores two kinds of information: parameters

related with the mobile subscriber, including the subscriber’s ID, access

capability, user type and supplementary service; current location

information of the subscriber for call route establishment. For example:

the address of MSC or VLR. No matter where the mobile subscriber

roams, its HLR should provide all related parameters and input the latest

location into the database.

3.2.2.4 Authentication Center

The Authentication Center (AUC), a functional entity managing the

authentication information related with mobile stations (MS). It

implements MS authentication, stores the MS authentication parameters,

generates and sends the corresponding authentication parameters


21

according to the requests of MSC or VLR, including A-KEY, SSD, ESN,

MIN and AAV, and then calculates all random numbers to get the

authentication result.

3.2.2.5 Short Message Center

The Short Message Center (SC) is responsible for receiving, storing and

forwarding short messages between the CDMA mobile subscribers and

fixed line users or between mobile subscribers. It serves as a postal

office, receiving mails from every place, sorts them out and then

distribute them to the corresponding users. Through SC, the messages

can be sent to destination more reliably.

The short message services include point-to-point server and cell

broadcast service.

Note

Currently the MSC of ZTE features the functions of the Intelligent

Network (IN) Service Switching Point (SSP) to process IN service

requests at the Service Control Point (SCP).

For convenient management, MSC is always combined with VLR.

Besides, the signaling to AUC must pass HLR first, so HLR and AUC are

normally combined together to minimize network load.

3.2.3 Operation and Maintenance Management Subsystem (OMM)

The Operation & Maintenance Center (OMC) provides equipment

operators with network operation and maintenance services. The OMC

helps the operators manage subscriber information, make network

planning and improve the efficiency and service quality of the whole

system. OMC includes OMC-S and OMC-R, depending on the part for

maintenance. OMC-S is responsible for the maintenance on the MSS side

while OMC-R is responsible for the maintenance on the BSS side. Its

specific functions include: maintenance test, obstacle check and

handling, system status monitoring, realtime system control, office data

modification, performance management, subscriber tracking, alarm and

traffic measurement.


22

3.3 Interfaces and Protocols

According to the Open System Interconnection (OSI) model, we can

analyze the CDMA network on the aspects of interface, protocol and

interface functions in detail.

3.3.1 Interfaces

As shown in Figure 3.1-1, various interfaces exist in the CDMA system.

They can divide into the following categories according to different

subsystems: Air interface Um between mobile terminals and the BSS; A

interface between BSS and MSS, and other interfaces between internal

entities of the network.

3.3.1.1 Air interface

The Um interface is defined as the communication interface between MS

and BTS. It is the key distinguishing factor between CDMA network and

GSM network and is also the most important interface in CDMA network.

This interface grants compatibility to MSs from different suppliers and

networks of different operators, enables MSs to roam, ensures the

frequency efficiency of the cellular system, and adopts a series of

anti-interference technologies and interference preventing measures.

Obviously, the Um interface implements the physical connection from

MS to the fixed part of the CDMA system, i.e. the wireless connection.

Besides, it transfers information for radio resource management,

mobility management and connection management.

3.3.1.2 Interface between BSS and MSS – A interface

The A interface is located between MSC and BSC. Its physical link is

implemented through standard PCM digital transmission link of

2.048Mbit/s. It transfers information for MS management, BTS

management, mobility management and connection management.

3.3.1.3 BSS internal interface (Abis)

An interface between BSC and BTS is called the Abis interface. BSC on

the Abis interface provides signaling control information for BTS

configuration, monitoring, and testing and service control. Please refer


23

to related documentation about the BTS side.

3.3.1.4 MSS internal interfaces

Figure 3.3-1 Internal Interfaces of the Network

In Figure 3.3-1, the MSS part contains the names of interfaces between

equipment entities. They will be described one by one in the coming

part.

1. B interface

As an internal interface between VLR and MSC, the B interface is

used by the MSC to request the current location information of the

MS from VLR or notify the VLR to update the location information of

the MS.

2. C interface

As an interface between HLR and MSC, the C interface transfers

information for route selection and management. Once a call is

required to a MS, the Gateway MSC (GMSC) will request the roaming

number of the called MS from the HLR of the called side. The

physical link of the C interface is 2.048Mbit/s standard PCM digital

transmission cable.

3. D interface

As an interface between HLR and VLR, the D interface exchanges


24

information related with MS location and user management. It

ensures that the MS can establish and receives calls within the entire

service area. Its physical link is 2.048Mbit/s standard digital link.

4. E interface

It is the interface controlling different MSCs of adjacent areas. When

the MS moves, during a call, from the control area of one MSC to

that of another MSC, this interface can be used to exchange related

handoff information to activate and complete handoff, and thus to

complete the cross-cell channel handoff process without interrupting

the communication. Its physical link is implemented through

2.048Mbit/s standard digital link between MSCs.

5. N interface

This interface is used to transfer route information related to the

called subscriber between MC and HLR. Its physical link is

implemented through 2.048Mbit/s standard digital link.

6. Q interface

It is an interface between MS and MSC transferring short messages.

Note

In the CDMA System; Um, A interface and other interfaces on the

network side are all open interfaces. The Abis interface is normally used

as an internal interface. If MSC and VLR are combined, the B interface

will be used as an internal interface. All open interfaces are compliant

with standard protocols.

3.3.2 Interface Protocols

A protocol is the common language among various functional entities. It

transfers messages through interfaces to establish an effective

information transmission channel to complete all communication and

management functions of the CDMA system. Different interfaces may

require different physical links to complete their own functions. When

the hierarchical protocol structure is adopted for the system’s interfaces,

the interworking with ISDN can be considered. Therefore, the interfaces


25

match the OSI reference model. The purpose of this structure is to allow

the isolation of different signaling protocols, describing protocols

according to continuous independent hierarchy. Each layer of protocol

provides specified service at the agreed service access point for its

upper layer protocol. Figure 3.3-2 shows the protocol structure of the

CDMA network.

Figure 3.3-2 CDMA Network Protocol Structure

On the BTS side, the IS-95 protocol of Qualcomm is used for the CDMA

system.

At the A interface, related standards stipulated by the Ministry of

Information Industry. The signaling model is shown in Figure 3.3-3:


26

A 口 BSC MSC

DTAP BSSMAP DTAP BSSMAP

Allocation function Allocation function

SCCP SCCP

MTP MTP

DTAP: Direct Transfer Application Part

BSSMAP: BSS Mobile Application Part

SCCP: Signaling Connection Control Part

MTP: Message Transmission Part

Figure 3.3-3 Signaling Protocol Reference Model of A Interface

The third layer consists of DTAP and BSSMAP. DTAP messages are

transparent to the A interface, therefore the A interface supports various

air interfaces to implement call processing and mobility management,

while radio resource management is mapped into a BSSMAP message

and then transferred through the A interface.

Layer 2: Based on the MTP of SS7 signaling.

Layer 1 features digital transmission at the rate of 2048 Kbit/s.

On the network side, the functional entities communicate through SS7

MAP protocol, which reflects the SS7 signal protocol structure.

M T P

S C C P

M A P

T C A P

IS U P T U P

Figure 3.3-4 SS7 Signaling Hierarchical Structure


27

Note

Concepts related with the SS7 signaling system are widely used in the

CDMA network. Information transfer is implemented through the MAP

application layer among MSC, VLR, HLR, AUC and SC. Due to its

important position, SS7 will be described separately in this set of

textbooks.


28


29

4 Numbering Plan

Key points

Understand the meanings of each number in the CDMA network

Remember the numbering rules for each number.

In the CDMA network, different numbers are used in different places.

Because of the roaming feature of mobile subscribers, these numbers

must be accepted and identified at any switching equipment. Therefore,

in mobile communication, it is necessary to give a unified numbering

plan for different numbers to enable entities in the network to

distinguish and identify mutually.

4.1 Numbering Plan

In CDMA networking, we use the following numbering plan:

1. E.164: The international public telecommunication numbering plan.

All country codes (CC) are assigned by ITU in Recommendation

E.164.

2. E.212: International identification plan for mobile terminals and

mobile users

All mobile country codes (MCC) are assigned by ITU in

Recommendation E.212.

4.2 MDN

The Mobile Directory Number (MDN) is the standard international

telephone number used to identify a given subscriber. It consists of a CC

Country Code), an MAC (Mobile Access Code ) and an SN (Subscriber

Number).

The MDN number is based on the ITU-T E.164 standard.


30

Structure of the MDN:

CC: Country Code

MAC: Mobile Access Code.

SN: Subscriber Number.

In Wireless Local Loop (WLL) application, MDN can be of different

structures depending on network operators in different countries.

The standard structure for WLL will be:

MDN is sent by MSC/VLR to HLR to setup the call procedure. Usually, we

dial only the Office Code + ABCD therefore; MSC/VLR transforms the

dialed number into the above MDN format and then sent via SS7 link.

4.3 IMSI and MIN

The International Mobile Subscriber Identity (IMSI) is a unique identifier

allocated to each mobile subscriber. It consists of a MCC (Mobile Country

Code), a MNC (Mobile Network Code) and a MSIN (Mobile Station

Identification Number).

The IMSI number is based on the ITU-T E.212 standard.

This number should be written into the MS.

Chapter 4 Numbering Plan

31

MCC: Mobile country code

MNC: Mobile network code

MSIN: Mobile subscriber identification number, a 10-digit decimal

number.

MIN is defined following the AMPS standard to ensure the CDMA/AMPS

bimodal operation, and is the last 10 digits of IMSI, namely MSIN, as

required by this system.

IMSI number may vary in context depending on operators in different

countries.

4.4 Equipment Number

In CDMA networking, we use MSCIN/VLRIN/HLRIN/SCIN to identify the

networking entities and realize international routing of SS7 messages.

In CDMA networking, MSCIN/VLRIN/HLRIN/SCIN is based on the ITU-T

E.212 standard.

4.5 Temporary Local Directory Number (TLDN)

To call a mobile subscriber, VLR allocates a temporary number to the

mobile subscriber for the network to select a route.

4.6 Electronic Sequence Number (ESN)

ESN is the unique number used to identify a MS. One unique SN (Serial

Number) is allocated to every individual bimodal MS. It consists of 32

bits, and the equipment serial number is set by the MS manufacturer.

Note

The GT number is the address information of the SCCP layer. It will be

described in the description of SS7 signaling.


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33

5 CDMA Key Technologies

Key points

Application of codes in the CDMA system

Key technologies on CDMA.

5.1 Basic Concept

CDMA stands for code division multiple accesses. Various code

sequences may be involved in this technology. Different coding

processes are required for different sources and channels. The following

description is focused on several different codes.

5.1.1 Walsh Code

The Walsh code is originated from the Walsh function through

complicated resolution process. The process is not described in this

textbook. The point is on the attributes of Walsh code.

The Walsh function is a non-sine complete orthogonal function system.

Its possible value could be selected from +1 and –1 (or 0 and 1). It is

suitable to be used to denote and handle digital signals. Thanks to its

excellent correlation, the Walsh function can be used as address code in

CDMA communication. In IS-95, the 64-order Walsh code is used for

channel discrimination. In the CDMA system, each forward code channel

is spread with 1.2288Mbit/s 64-order function to make all forward code

channels mutually orthogonal. The code channels spread with 64-order

Walsh function n (n=0—63) can be defined as Code channel No.n.

5.1.2 Pseudo-random Sequence Number

In the communication theory, white noise is a random process. Its

transient value is subject to normal distribution. Its power spectrum is

even in a very wide range. The pseudo noise (PN) sequence, similar with


34

the white noise sequence, appears random but it is actually a regular

periodic binary sequence. In the CDMA communication technology, the

address code is selected from a pseudo random sequence. From all

pseudo sequences, the m sequence is selected as the address code. Its

various phases can be used to discriminate different subscribers. This

method is used in the current CDMA cellular system.

IS-95 also uses the self correlation of the PN code, while the m

sequence has the best self correlation, therefore the PN code of the m

sequence is selected as the address code. The near orthogonal

attributes of m sequences in different phases are used to allocate a

phase for the channel of each subscriber.

The periodic donation of the m sequence is:

P = 2 n – 1 (n is the length of the shift register).

In the CDMA system, the long code and short code of the m sequence

are used: long code n=42, short code n=15.

Note

Orthogonal: a mathematics concept. If the integral of two functions

product comes to zero in a period, it can be called as orthogonal.

Correlation: can be divided as self correlation and mutual correlation.

The former is the comparison of the same signal at different time

segments, reflecting the change of wave form and the phase. Mutual

correlation refers to the relationship between two signals and is used to

indicate the difference of wave form and the phase between two signals.

The self correlation of the m sequence pseudo-random code is

approximately 1, while that of mutual correlation is approximately 0.

This is the optimal code type.

The “m” in the m sequence should not be used in its upper case. In the

pseudo sequences, the M sequence is another spreading communication

sequence.

Chapter 5 CDMA Key Technologies

35

5.1.3 Number Application

5.1.3.1 Walsh code —— identifying forward channel

In the CDMA system, each forward code channel is spread with

1.2288Mbit/s 64-order function to make all forward code channels

mutually orthogonal.

5.1.3.2 PN 215 short number —— identifying BTS, 242 long number —— reversely identifying MS: forward identifying scrambler

Among forward channels, the m sequence of a length of 242 –1 is used to

harass the codes on the service channel. The m sequence of a length of

215 –1 is used for orthogonal modulation of the forward channel.

Different m sequences are used by different BTSs for modulation. Their

phase deviation is 64 bits at least. So, totally 512 different phases can

be available at most.

Among reverse channels, the m sequence of a length of 242 –1 is used

for spreading directly. Along with the mask value change, the phase of

the m sequence also changes. Every subscriber will be allocated with a

mask calculated through the MS Electronic Serial No. (ESN). Namely,

every subscriber will be randomly allocated with a phase of PN code

(with the length as 242 –1) and this phase is not repeated. Because of

the dual correlation attributes of the m sequence, any two subscribers

are approximately orthogonal. The PN code of 215 –1 is also used for

orthogonal modulation of reverse service channels. But it is unnecessary

to identify the BTS at the reverse channel, m sequences of the same

phase are used for all BTSs, so the phase deviation is 0.

5.1.4 Number-based Channels

5.1.4.1 Forward channel

1. Pilot channel: A channel continuously transmitting signals at

the forward CDMA channel. It is used for synchronization and

handoff of all working MSs within the coverage of the BTS.

2. Intra-frequency channel: This channel is for convolution

coding, code symbol repetition, interleaving, spreading and

modulation. In the coverage of the BTS, the active MS can get


36

initial clock synchronization through this channel.

3. Paging channel: This channel is for convolution coding, code

symbol repetition, interleaving, scrambling, spreading and

modulated spreading signals. The BTS sends system information

and MS paging messages through this channel.

4. Service channel: Transfer subscriber service data. The relationship

between channels and Walsh code is illustrated in Figure 5.1-1:

Figure 5.1-1 Relationship between Channels and Walsh Code

5.1.4.2 Reverse channel

1. Access channel: The channel used by the MS to originate

communication with the BTS and by the responding BTS to send

paging channel messages. The access channel transmits a coded,

interleaved and modulated spreading signal. It is discriminated

exclusively through the public long number mask.

2. Reverse service channel: used to transmit subscriber information

and signaling information during call connection.

5.2 Key Technologies

5.2.1 Power Control Technology

This is the core technology of the CDMA system. If all subscribers in the

cell transmit signals at the same power, the signals transmitted from a

near MS to the BTS are stronger, and the signals transmitted from a far


37

MS to the BTS are weaker. As a result, strong signals override weak

ones. This is called “Near/Far Effect” in the mobile communication. The

CDMA system is a self-interfering system. All mobile subscribers share

the same bandwidth and frequency. The “Near/Far Effect” is very

obvious. The purpose of CDMA power control is to wipe out this effect to

ensure that the system can provide high communication quality without

generating interference to other subscribers.

Power control includes forward power control and reverse power control,

while reverse power control can also be divided into open loop power

control only involved with MSs and closed loop power control involved

with MSs and BTS.

5.2.1.1 Reverse Open Loop Power Control

In this power control mode, the MS adjusts its transmitting power

according to its receiving power in the cell, so that the signals

transmitted by all MSs have the equal power when reaching the BTS.

This main purpose is to implement such effects as shadow compensation;

therefore, it features a large dynamic scope, at least in the range of

–32dB ~ +32dB according to the IS-95 standard.

Open loop power control is based on a rough estimation of the sending

level of a MS, while the MS estimates the sending level by measuring

the receiving power, without modulation via any forward link.

5.2.1.2 Reverse Closed Loop Power Control

The design purpose of closed loop power control is to enable the BTS to

correct the open loop power of the MS rapidly so that the MS can

maintain the optimal transmitting power. During closed loop power

control at a reverse service channel, the MS will refer to the received

effective power control bit at the forward service channel to adjust its

average output power.

5.2.1.3 Reverse Power Control

During forward power control, the BTS adjusts the transmitting power of

each MS according to measurement results. Its purpose is to allocate

light forward link power for MSs with low path attenuation and allocate


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heavy forward link power for those MSs with high BER and far from the

BTS.

The BTS decides whether to increase or decrease the transmitting power

according to the forward FER report from the MS.

5.2.2 Diversity Technology

This technology enables the system to receive two or more input signals

at the same time and the attenuation statuses of these input signals are

not related to each other. The system demodulates these signals

respectively and then adds them together. In this way, more useful

signals can be received to overcome attenuation.

The mobile communication channel is a multi-path attenuation channel.

Its attenuation can be divided into fast attenuation and slow

attenuation.

The diversity technology is an effective method to overcome multi-path

attenuation. It enables the receiver to combine several received signals

carrying the same information but of independent attenuation attributes,

before making a decision. Attenuation is related with frequency, time

and space, therefore the diversity technology involves space diversity,

time diversity and frequency diversity.

5.2.2.1 Time diversity (RAKE receiving technology)

The mobile communication channel is a multi-path attenuation channel.

The RAKE receiving technology is to receive a line of signals for

demodulation separately and then, overlay them for output to achieve

enhanced receiving effects. The multi-path signal is not a negative factor,

but can be a favorable factor in the CDMA system.

5.2.2.2 Frequency diversity

The CDMA bandwidth transmission is the specific application of

frequency diversity.

5.2.3 Handoff Technology

The following types of handoff may be involved when the MS


39

implements communication via the service channel:

5.2.3.1 Soft handoff

Soft handoff happens between CDMA channels of the same frequency

but in adjacent cells. In this type of handoff, when the MS starts to

communicate with a new BTS, the communication with the original BTS

is not immediately cut off. Soft handoff is only available for CDMA

channels of the same frequency. It can provide path diversity at the BTS

border for forward service channels and reverse service channels. Figure

5.2-1 shows a soft handoff between different BTSs within the same BSC;

while Figure 5.2-2 shows a soft handoff between different BSCs within

the same MSC.

Figure 5.2-1 Soft handoff Within the Same BSC

Figure 5.2-2 Soft handoff between Different BSCs within the Same MSC

5.2.3.2 Softer handoff

The handoff between CDMA channels in different sectors but with the same

frequency and within the same BTS is called as softer handoff. Figure 5.2-3

reflects the softer handoff process.


40

Figure 5.2-3 Softer Handoff Process

5.2.3.3 Hard handoff

In this handoff mode, the MS will first get disconnected from the original BTS

and connected with a new BTS. The handoff normally happens at CDMA channels

of different frequencies or between different MSCs, as shown in Figure 5.2-4.

Figure 5.2-4 Hard Handoff

5.2.3.4 Handoff from CDMA to analog

In this handoff, the MS transfers from a CDMA service channel to an

analog voice channel.


41

5.2.4 Voice Coding Technology

At present, the voice coding of the CDMA system falls in two types:

Code-Excited Linear Prediction (CELP), 8 kbps and 13 kbps. The voice

quality of 8kbps voice coding is as good as the 13kbps voice of GSM, or

even better. The voice quality of 13 kbps voice coding is as good as that

of the fixed toll call. The CELP is based on the same principles as the

PELPC, just different in that the pulse position and amplitude are

replaced by a vector code table.

5.2.5 Channel Modulation Technology

Reverse CDMA channels include access channels and reverse service

channels. These channels are used at the same CDMA frequency

through direct sequence spreading CDMA technology. Data transmission

is implemented in the unit of frame 20ms. Any data, before transmission,

will be processed in a series of links: convolution coding, block

interleaving, 64-order orthogonal modulation, direct sequence spreading

and baseband filtering.

Forward CDMA channels include pilot channel, intra-frequency channel,

paging channel (7 at most) and a number of service channels. Each

code channel will be orthogonally spread through a Walsh function and

then spread through a 1.2288Mchip/s PN sequence.

The following part describes the digital spectrum spreading mechanism

and the changes of signal spectrum after spreading, as shown in Figure

5.2-5 and Figure 5.2-6.


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Cell coding

Walsh code

Channelcoding

(spreading)Carrier

modulationCarrier

demodulationChanneldecoding

(dispreading)

Cell decoding

Cell decoding

PN pseudo-random code

Channeldecoding

(dispreading)Carrier

demodulationCarrier

modulationChannelcoding

(spreading)

Cell coding

Walsh codeForwardreceiving

Forwardtransmission

Backwardtransmission

Backwardreceiving PN pseudo-

random code

Figure 5.2-5 Digital Spectrum Spreading


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Signal Pulse noise White noise

Signal spectrum after despreadSignal spectrum before despread

S（f）

f0

Signal

Noise

S（f）

Signal

Noise

White noise White noise

f0

S(f)

Signal spectrum before spread

Signal

S（f）

f0

Signal spectrum after spread

Signal

f0 f0

Figure 5.2-6 Signal and Noise Spectrum Change

5.2.6 Soft Capacity

In the CDMA network, two methods are available for dynamic capacity

adjustment:

1. Raise FER to get more available channels by lowering voice quality.

2. Cell breath function: Adjust the pilot value of the BTS to adjust the

cell’s coverage.


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45

6 Services and Functions

Key points

An introduction to the main services of the CDMA network

Major functions

6.1 CDMA Services

6.1.1 Telecommunications Services

The CDMA network can offer the following telecommunications services

to the subscribers:

1. Voice service

The voice codec adopts EVRC. 8K QCELP should be supported in the

area where the GreatWall Network is deployed to support the

subscribers of the existing subscribers of the GreatWall Network.

2. SMS service

The following SMS services should be supported:

· MS-originated SMS

· MS-terminated SMS

· Cell broadcast SMS (IS824)

· Chinese (GB13000) SMS

6.1.2 Supplementary Services

6.1.2.1 Types of Supplementary Services

The following supplementary services can be offered to the subscribers.


46

Table 6.1-1 Types of Supplementary Services

Service Name Remarks

Call Forward Busy (CFB)

Call Forward Default (CFD)

Call Forward No Answer (CFNA)

Call Forward Unconditional (CFU)

Call Transfer (CT)

Call Waiting (CW)

Calling Number Identification Presentation

(CNIP)

Calling Number Identification Restriction (CNIR)

Conference Call (CC)

Message Waiting Notice (MWN) It is used in the voice

mailbox service.

3-Way Calling (3WC)

Voice Message Retrieval (VMS) It is used in the voice

mailbox service.

6.1.2.2 Operations of Supplementary Services

1. Operation definition

Seven service operations are defined in the CDMA system.

1) Provision: An operation implemented by the service provider to

make the service available to the subscriber.

2) Cancellation: Reverse operation of provision. It is the operation

implemented by the service provider to make the service

unavailable to the subscriber.

3) Registration: An operation implemented by the service provider or

subscriber to make the service executable. Registration involves

the input of necessary information.

4) Erasure: An operation implemented by the service provider or

subscriber to delete the information entered for registration.

5) Activation: It is used to make the subscriber enter the "Ready to

provide service" status.

6) Deactivation: Reverse operation of activation.

Chapter 6 Services and Functions

47

7) Request: Service execution process.

2. Subscriber operation

Among the above operations, provision and cancellation are

generally implemented by the operator; the registration, erasure,

activation, deactivation, and request operations can be performed

by the subscriber through the MS.

6.1.3 WIN Service

The WIN provides basic IN service platform in the CDMA system by

using the IN mode. The following WIN services need be implemented:

· Pre-Paid Charging

· VPN

· Freephone

6.1.4 Value-added Service

The voice mailbox provided by the CDMA network should provide

services such as message leaving, message operations, auto answer,

timed delivery, message notification, and bulletin board.

The SMS service platform provided by the CDMA network should provide

the subscribers with application-oriented wireless service data, for

example, weather forecast and stock market information.

The CDMA network should provide other value-added services as

required.

6.2 Network Functions

6.2.1 Network Functions for Supporting Services

Supporting the call processing for establishing communication with

networks such as PSTN and PLMN after the roaming.

Authenticating registration and call setup.

Supporting the telecommunications services and supplementary services


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described in Section 5.1.

Taking measures to protect the important signaling units exchanged

between the MS and the BS to avoid any unauthorized users from

getting them.

Supporting WIN and providing WIN-related services as required.

Supporting voice mailbox and SMS service and providing other

value-added services as required.

6.2.2 Network Functions for Supporting the Running of the Cellular System

6.2.2.1 Roaming

Roaming means that the MS leaves its home mobile service local

network. The MS judges whether it is roaming according to the SID, and

can prompt the subscriber of the roaming status.

To enable the network to keep track of the location of the MS, the MS

should implement location registration. The registration modes include

power-up registration, power-down registration, periodical registration,

distance-based registration, zone-based registration, parameter-change

registration, implicit registration, ordered registration, and so on.

6.2.2.2 Handoff

Handoff refers to the process of transferring the ongoing call from a cell

to another cell. Handoff is used for radio propagation, service

distribution, activation operation maintenance and clearing device fault.

There are two handoff modes in the CDMA system: soft handoff and

hardware handoff.

1. Soft handoff

With the soft handoff, the MS uses the same frequency to connect

with the new cell before disconnecting itself from the old cell.

The soft handoff falls into the four types:

· Handoff between two sectors in the same BS

· Handoff between two cells in different BSs

Chapter 6 Services and Functions

49

· Three-party handoff between the cells/sectors in different BSs

· Handoff between different BSCs (optional)

2. Hard handoff

During the hard handoff, the traffic channel is interrupted

instantaneously.

Hard handoff falls into two types:

· Handoff between different channels in the same MSC

· Handoff between different MSCs

6.2.3 Additional Network Functions for Call Processing

The function of encrypting user voice channel should be provided. The

implementation of this function does not affect the purchase of the

devices, deployment/running of the system and whole network, or other

functions.

In the MS->network direction, after the voice channel is set up, the

system should support the sending of the DTMF signals of the users

(converting the DTMF signals to the signaling messages for transfer over

the radio interface).

6.2.4 Authentication Function

Both the MS and the system should support the authentication function.

The CAVE algorithm is used as the authentication algorithm.

Both the MS and the system should support THE SSD updating. The

system should support the sharing and non-sharing of SSD.

6.2.5 Roaming Function between Different Modes

The MS in the CDMA system can work in two modes: CDMA mode and

AMPS mode. The dual-mode MS can automatically roam between the

coverage area of the CDMA network and that of the AMPS network.

6.2.6 International Roaming

The system should support the international roaming service. To support


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international roaming, the system should support at least the following

functions:

· Analyzing the IMSI/MIN to check whether the subscriber is an

international roaming subscriber, and implementing the

corresponding processing.

· Sending international TLDN (including CC).

· Conducting conversion between China SS7, ITU SS7, and ANSI SS7

at the international gateway office.

· The charging system provides proper the charging format conversion

functions.

· Determining whether to implement authentication and whether to

share SSD according to the subscribers in different countries.

The MS can support the international roaming service. To support

international roaming, the MS should support at least the following

functions:

· Proper voice codec; EVRC is required in China.

· Adopting the numbering plan that follows the MIN-based IMSI

principles.

· Supporting proper frequency configuration.

CDMA-3GCN I 01 200904 Principle of Telecommunication

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