CDMA-DSS I 01 200904 Principle of Telecommunication-37

CDMA-DSS_I_01_200904Principle of Telecommunication

中兴通讯学院

Objects

• Knowing the structure of the signaling network and digital mobile communication network

• Knowing the development of mobile communication

• Knowing the basic knowledge of CDMA key technologies

• Familiarizing with CDMA network structure• Familiarizing with ZXDSS network structure

Contents

• Brief introduction to the signaling network and digital mobile communication network

• Development of mobile communication• CDMA key technologies• Basic structure of CDMA network• Composition of ZXDSS network

Signaling Network--Network Level Structure

The signaling network in China generally uses three-level structure, which is composed of Level-1 High-level Signaling Transfer Point (HSTP), Level-2 Low-level Signaling Transfer Point (LSTP) and Level-3 Signaling Point (SP). It can also use two-level structure, composed of HSTP&LSTP, and SP.

HSTP&LSTP Level-1 HSTP

Level -2 LSTP

Level-3 SP SP

Signaling Network--Functions of the Signaling Points

Level-1 HSTP transfers signaling messages tandemed from level-2 LSTP and level-3 SP. HSTP should use stand-alone signaling transfer point equipment, which should satisfy functions specified by Message Transfer Part (MTP), Signaling Connection Control Part (SCCP), Transaction Capability (TC) and Operation Maintenance Application Part (OMAP) in No.7 signaling method.

Level-2 LSTP transfers signaling messages tandemed from level-3 SP. LSTP can use stand-alone signaling transfer point equipment or it can use signaling transfer point equipment integrated with the SP.

Level-3 SP is the source point or destination point for transmitting signaling messages in the signaling network. According to the differences in functions, it should satisfy MTP, TUP, ISUP, SCCP,

TC, and MAP and /or OMAP functions.

Digital Mobile Communication Network

The digital mobile communication network in China generally uses a three-level structure: TMSC1, TMSC2, and MSC.

TMSC1

MSC

TMSC2

TMSC1

TMSC1

Contents



First Generation Analog Cellular Mobile Communication

In late 1970s, the first generation cellular mobile communication system was developed on the basis of cellular networking technologies, which started the commercialization of the cellular mobile communication system. The first cellular system AMPS (Advanced Mobile Phone Service) was developed in Chicago in 1979. Other standards in this phase included TACS in Britain and NMT in northern Europe.

Second Generation Digital Cellular Mobile Communication

The mobile phone system using TDMA and narrowband CDMA was developed in 1980s, which is called the second generation mobile communication system. Typical products included the following two types: TDMA System

Main feature of TDMA product is that it used time division multiple access and frequency division multiple access technology to realize mobile communication.

Narrowband CDMA System CDMA is a kind of new digital cellular technology

developed after GSM technology. N-CDMA series are mainly the N-CDMA based on IS-95 developed by Qualcomm Company.

Third Generation Mobile Communication----IMT2000

With the increase of users and development of digital communication, second generation mobile phone system became deficient. Firstly, it cannot provide broadband information services, such as high-speed data, low-speed images, and TV pictures because of narrow bandwidth; secondly, the GSM did not realize the real global roaming, especially in America and Japan, it is not widely applied. With the development of science & technology and communication services, an integrated service system combining current mobile phone system functions and multiple services is required. Therefore, ITU requires to realize the commercial third generation mobile communication system in 2000, which is IMT-2000.

Key Features of IMT-2000

Including many systems High-degree consistency of designs worldwidely Compatibility of services and fixed networks in IMT-

2000 High quality Small portable terminals are worldwidely used

Technical Standards for Third Generation mobile Communication System

1. Qualcomm Company raised broadband CDMA2000 proposal reversely compatible with the IS-95 system.

2. For IMT-2000 development targets, Europe supported to use broadband packet switching network as the core, evoluted the current network mode layering by functions to port-to-port client-server mode, and developed WCDMA standards reversely compatible with GSM. This solution made it easier to smoothly develop from GSM to third generation system, therefore it is supported by many GSM suppliers.

3. China submits TD-SCDMA technology to ITU-R.

Evolution from 2G to 3G Currently there are two main standards: GSM and IS-95

CDMA, therefore, evolution from 2G to 3G includes evolution of GSM and evolution of IS-95 CDMA.

Evolution of GSM generally developed to GPRS (2.5G) phase firstly, and then evoluted to WCDMA. Evolution of IS-95 CDMA firstly developed to cdma2000-1X (single carrier, and highest speed is 384kb/s), and then developed from cdma2000-1X to cdma2000-1XEV.

GSM GPRS

EDGE

WCDMA

IS-95A cdma2000-3x

IS-95B

cdma2000-1x

PDC

1 XEV_DO 1 XEV_DV

1 XEV

Contents



Multiple Access FDMA: Frequency Division Multiple Access

In a relatively narrowband channel in the frequency domain, signal power is concentrated for transmission, and different signals are distributed to channels with different frequencies; the interferences to/from adjacent channels are limited by band-pass filters. In this way, only energies of useful signals can pass in the specified narrowband, while signals in other frequencies are excluded.

TDMA: Time Division Multiple Access A channel is composed of a succession of periodical time slots, energies of different

signals are distributed to different time slots; the interference of adjacent channels are restricted by time gating, therefore, only the energies of useful signals can pass in the specified time slot.

CDMA: Code Division Multiple Access Each signal is allocated with a pseudorandom binary for spectrum spread, energies

of different signals are distributed to different pseudorandom sequences. In the receiver, signals are separated by a correlator; the correlator receives only the selected binary sequences and compresses it spectrum, bandwidths of signals which do not comply with the binary sequences will not be compressed. Therefore, only the information of useful signals is identified and extracted.

Multiple Access Technologies

FDMA

TDMA

CDMA

Power

TimeFrequency

Power

TimeFrequency

Power

TimeFrequency

CDMA Basic Concepts CDMA is a technology of modulating the information

data by using a high-speed pseudorandom code. The information data have certain signal bandwidths, while the bandwidth of the pseudorandom code is much higher than the signal bandwidth. This technology is based on spectrum spread. After modulation, the bandwidth of the original data signals are spread, and then it is modulated and sent by the carrier wave. The receiving end uses the same pseudorandom code and processes the received bandwidth signals, converts them from broadband signals to narrowband signals, realizing information communication.

CDMA Characteristics

1. Large coverage

2. Large capacity

3. High voice quality

4. Environmental friendly

5. High frequency usage rate

6. Simple frequency planning, easy expansion

7. Strong disguise and security

8. Strong anti-interference capability and anti-multipath capability

CDMA Key Technologies--Soft Handoff

Soft handoff is particular in CDMA mobile communication system. Its principle is as follows: When the mobile stations are at the area between neighboring BTSs controlled by a same, MS establishes wireless connection at the same time when maintaining the wireless connection with source BTS, and then it releases the wireless connection with the source BTS. The soft handoff happened on different sectors of a same BTS that is controlled by a same BSC are called even soft handoff.

CDMA Key Technologies--Power Control

If all users in the cell transmit in the same power, the signals of MSs near the base station are stronger when reaches the base station, while those of MSs far from the base station are weaker, causing the strong signals cover the weak signals. In the CDMA system, power of a user signal is higher, which is good for correct receiving. But interference on other uses in the sharing bandwidth is increased, even useful signals are flushed. This deteriorates other users’ communication quality and decreases system capacity. To overcome this problem, the required power of transmitter should be adjusted in real time according to communication distances. This is the “power control”.

CDMA Key Technologies--Rake Receiving

Wireless signals transmitted by wireless transmitter will be reflected when encounters obstacle. Because of reflected wave, direct wave, and mobile BTS, different transmission paths for the signal are generated from transmitter and receiver, and there are delays between signals in different paths reaching the receiver. When the delay between signals in two paths meets certain conditions, these two signals are considered as uncorrelated signals. CDMA system uses this feature to construct multipath receiving on the receiver, and it is called RAKE receiving.

RAKE receiver uses multiple despreaders to perform proper delay on received signals, which correspond to multiple paths. And then, it performs demodulation and despreading on these delayed signals, finally generates the signals.

CDMA Key Technologies--Variable Bit Rate Coding

It fully utilizes voice activation factors, decreases transmitting power and increases system capacity. There are three standard voice coding technologies for CDMA, which have good background noise suppression function.

Contents



Structure of CDMA Cellular Mobile Communication System

MS

Internet

PSTN

PDS / PHR

PDSN /AAA

MSC / VLR

PDC

PCF

BSC

HLR / AUC

SC

OtherMSC

OMC

BTS

DAS

SCP

DSS System

Dispatching Console

Management Console

C

EAi

T1

T2

QAAbisUm

N

PLMN

E

A10/A11

A10d/A11d

Composition of the Subsystem--Base Station Subsystem (BSS)

Base Transceiver System (BTS) BTS is the wireless part of base station system. It is controlled by

base controller, and it serves a cell. BTS completes conversion between BSC and wireless channel, realizes wireless transmission between BTS and MS by air interfaces and related control function. It communicates to BSC by Abis interface.

Base Station Controller (BSC) One end of BSC connects to multiple BTSs, and another end con

nects to OMC. BSC faces the wireless network, accomplishes wireless network management, wireless resource management, and wireless base station monitoring management. Besides, it controls the management on establishing, connecting, and releasing of wireless connection between MS and BTS, controls MS locating, handoff, and paging. It provides also voice coding, and rate adaption functions; meanwhile, it completes operation & maintenanc

e function on base station subsystem.

Composition of the Subsystem--Mobile Switching Subsystem (MSS)

Mobile Switching Center (MSC) Visit Location Register (VLR) Home Location Register (HLR) Authentication Center (AUC) Message Center (MC)

Composition of the Subsystem--Packet Data Switching Subsystem (PDSS)

PDSN (Packet Data Serving Node) HA (Home Agent) AAA (Authentication, Accounting, Authorization

Server) AN-AAA (Access Network-Authentication,

Accounting, Authorization Server)

Composition of the Subsystem--GoTa

PDS PDS is the PTT Dispatcher Server, which is the

overall control point of trunk calls; it processes trunk dispatching calls.

PHR PHR is the PTT Home Register; it completes PTT

service authentication, authorization, accounting, location update, and dynamic group management. Meanwhile, it provides service handling of PTT group, and PTT users for trunk users.

DAS DAS is the dispatching Agent Server, provides PTT

virtual dispatching special network service for trunk users

Composition of the Subsystem--Operation & Maintenance Center (OMC)

OMC provides operation and maintenance services on the network for operators, it manages subscribed users’ information, and plans the network, so as to improve the overall working efficiency and service quality for the system.

Contents



Composition of ZXDSS System ZXDSS is used to realize trunk dispatching services. T

he ZXDSS dispatching service system launches, controls, and manages the trunk dispatching services, which is the control center for trunk dispatching services in GoTa digital trunk system.

BSC/PDC

PHR DACO&M Console O&M

Server

Fi rewal l

Ethernet

DAC

DSS System

IP Network

Billing Interface Server

DAS PDS

PDS Alarm Box

PHR Alarm Box

Composition of the ZXDSS System

PDS (PTT Dispatching Server), controls trunking calls and distributes trunking voice flow messages.

PHR (PTT Home Register), completes service authentication, authorization, and accounting, location update and dynamic group management, fleet group and user service management.

DAS (Dispatching Agent Server), is the agent for service management and dispatching. It provides dispatching management services for fleet users together with DAC (Dispatching Agent Client).

OMC is composed of operation maintenance server and operation maintenance client, it maintains and manages the whole dispatching service system.

Services of ZXDSS System--Essential Services of ZXDSS System

Group Call Private Call Broadcast Call Mobility Management Floor Management Accounting Management Trunk Service Management

Services of ZXDSS System--Supplementary Services of ZXDSS System

Short Number Dialing Subscriber Number Presenting Format Configuration Pre-emptive Priority Call Wireless Grouping Incoming Call Prompt When Busy Late Entry Time-limited Call Routing Management Function Based on Location Priority Management Dispatch Emergency Call Number Display Talker Identification, Display and Limitation Terminal Status Query Private Call Forwarding Conversation Status Promption Selection of Dispatching Area

Indication for Exceeding Dispatching Area Function Number Addressing Cross Fleet Call Call Limitation Trunking Prepaid Service Group Watching Function End-to-end Encryption Location Function Number Upgrading Function Maximum Talking Duration Limitation Fleet Callback Request Function Groups (Users) Expired License-Controlled Trunk Function Daylight Saving Function Lawful Interception Function

Interfaces of ZXDSS System

PDS

PHR

PDC DAS

Dispatching Console

Management Console

Accounting

Center

Billing

Center

A11d/A10d

RADIUS

IP

HTTP

PDSOMC

PHR OMC

SNMP

IP

Interfaces of ZXDSS System

Interface between PDS and PDC Interface between PDS and PHR Interface between DAS and PDS Interface between DAS and PHR Interface between DAC and DSS Interface between PDS and OMC Interface between PHR and OMC

CDMA-DSS I 01 200904 Principle of Telecommunication-37

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