CDMA 原理及硬件结构

OUTLINE

一、信道结构二、呼叫过程 MS 初始化状态 MS 空闲状态 系统接入状态 MS 控制业务信道状态

三、 MOTOROLA BSS 系统结构

信道结构

Forward CDMA Channel 　 Structure

1 、 Pilot Channel

导频不含信息，只是用来搜索 Pilot PN offset.

2 、 Sync Channel

用来完成 MS 的时钟同步和长码同步。 Walsh 32

同步信道 1 帧 =26.67ms

3 、 Paging Channel

寻呼信道 1 帧 =20ms

寻呼模式： 非时隙寻呼模式：移动台在所有的时间内监视寻呼信道

时隙寻呼模式：移动台仅在配置的寻呼信道时隙中监视寻呼信道。由于移动台没有必须在所有的时间内监视寻呼信道，所以在时隙模式内操作的移动台能够保留电池能量。

Paging Channel 中有关长码掩码 (LCM) 的消息

41---------------29 28--24 23-21 20--------------9 8--------------0

11000110001101 00000 PCN 000000000000 pilot pn offset

PCN:paging channel number( 共三位 walsh1-walsh7)

在长码掩码中包含有两个未知项， PCN 和 pilot pn offset 。所以在手机接受的寻呼信道信息中知道了 PCN 和 pilot pn offset ，手机即可产生相同的长码掩码。

4 、 Forward Traffic Channel

语音编码 1 帧 =20ms 。（话音功率普密度为 20-40ms ）功率控制比特（ 800bps ）在前向业务信道通过打孔方式加入，即把一个话音比特用一个功率控制比特来代替。功率控制比特由 BTS 的 MCC 板产生。

前向业务信道的长码掩码结构

41---------32 | 31-----------0

1100011000 | ESN

与反向业务信道的长码掩码结构相同

在 IS-95A RATE SET 1:9.6K 4.8K 2.4K 1.2K

数字基带信号的速率与功率成正比

Rate X Eb = Power

Reverse CDMA Channel 　 Structure

1 、 ACCESS CHANNEL

对应每一个前向 Paging 信道，反向可以有 32 个 Access Channel , 即每个小区最多可以由 32*7 个 Access Channel 。

接入信道 1 帧 =20ms

接入信道的传输速率固定在 4800bps

2 、 Reverse Traffic Channel

所有反向信道所加的短码片直为 0 ，反向信道中加短码的目的只是为了扩频

呼叫过程Power up

Mobile station

initilization state

Mobile station

idle state

Mobile station idle handoff operation with NGHBR_CONFIG equal to ‘011’ or unable to receive paging channel message

Ends use of the traffic channelMobile station has

fully acquired system timing

Initialization task

SystemAccessState

Mobile stationControl on theTraffic channel

Receive an acknowledgment to an access channel transmission other than an origination message or a page response message

Directed to a traffic channel

Receives a paging channel message requiring an acknowledgment or response originates a call or partners registration

移动台初始化状态Power up or any other state

System determination

substate

Pilot channel acquisition

substate

Sync channel Acquisition

substate

Thinking change substate

Ms idle state

CDMA system select

Acquires pilot channel

Recieves sync channel message

在移动台初始化状态，移动台完成系统选择、导频信道捕获、同步信道捕获、计时变化等工作

移动台从同步信道消息中提取并存储系统的基本参数消息，包括系统标识（ SID ）、网络标识 (NID) 、导频 PN 序列偏置索引、寻呼信道速率等，以及定时信息，包括长码状态值、系统时间、出现闰秒的时间、夏令时指示灯

在计时变化子状态，移动台完成：

1 、长码同步

2 、时钟同步

Sync Channel Message

移动台空闲子状态

Idle Procedures

•Paging Channel Monitoring

•Acknowledgement Procedures

•Registration => GOTO System Access State

•Idle Handoff

•Address Recognition for Other than Page Messages

•Authentication, Encryption, Privacy

在寻呼信道上发给移动台的总共有 6 条开销消息•系统参数消息•相邻列表消息•CDMA 信道列表信息•扩展的系统参数信息•全球服务该导信息•接入参数信息

以上前五个信息是配置信息，移动台连续地接受在寻呼信道上的这些不同的信息，并且将这些信息放到那些需要更新和加载进入移动台的内存中。

系统参数消息

在系统参数消息中主要包含：登记消息、寻呼模式消息、切换消息和功率控制消息等。

有关登记消息

1. 区域登记： REG_ZONE;TOTAL_ZONE;ZONE_TIMER 等

2. 开机登记： POWER_UP_REG

3. 关机登记： POWER_DOWN_REG

4. 参数变化登记： PARAMETER_REG

5. 周期性登记： REG_PRD

6. 距离登记： REG_DIST

接入参数消息

在此消息中包含有系统接入时所需

的参数：

INIT_PWR;NOM_PWR;PWR_STEP;

NUM_STEP;ACC_CHAN ；

PROBE_BKOFF;BKOFF 等

系统接入子状态The MS transmits on the Access Channel using a random access procedure. Many parameters of the random access procedure are supplied by the BS in the Access Parameters Message.

Power (EDIT SECTOR MSRPC)

IP = -73 - Mean Input Power (dBm) + NOM_PWR + INIT_PWR

NOM_PWR: Nominal transmit power offset (-8 to +7 dB)

INIT_PWR: Initial power offset for access (-16 to +15 dB)

PWR_STEP: Power increment (0 to 7 dB)

以上参数由数据库定义， IP 的大小影响手机的接入速度。

Number (EDIT SECTOR MACC)

NUM_STEP: Number of access probes (1 to 16).

MAX_REQ_SEQ: Maximum number of access probe sequences for an Access Channel request (1 to 15).

MAX_RSP_SEQ: Maximum number of access probe sequences for an Access Channel response (1 to 15).

PAM_SZ:Access Channel Preamble length, less 1,in frames.

MAX_CAP_SZ: Maximum Access Channel message capsule size, less 3, in frames.

移动台控制业务信道子状态

Traffic Channel initilization

Substate

Waiting for Order Substate

Waiting for Mobile Station Answer

Substate

Mobile station terminated call and mobile station receive a Base Station Acknowledgment Order on the Forward Traffic Channel

Enter from system access state

Receive a maintenance order or an alert with information message

MS user answers call

MS originated call and ms receive a Base Station Acknowledgment Order on the Forward Traffic Channel

Receive Release Order

Receive Release Order

Release substate

Conversation substate

Receive maintenance order

MS user initiates disconnect or ms receive Release Order

Receive Alert with information Message

功率控制及功率参数定义

MCC:

Eb/No<(Eb/No)set PCB=0 增功率

Eb/No>(Eb/No)set PCB=1 降功率

XC:

Fer < (Fer)target ， (Eb/No)set 减小

Fer < (Fer)target ， (Eb/No)set 增加

MOTOROLA BSS 系统结构

BSS System

System Interconnection

Signal Flow

BSS System

MM

MSC

BTS

BTS

BTS

OMCR UNO

XC

CBSC

MM

•MSC Interworking

•H/O Arbitration

•Central BSS FM

•Channel Allocation

•Page Distribution

•BSS Init. & Download

MM 为双接点 PUMA 平台，两个主机接点级备份，即运行两套独立的软件系统。

1 、路由部分 ROC

2 、处理器部分 CPU 、 SSC

3 、适配器部分 TOKEN RING CARD 、 EthNET CARD 、

SS7 CARD 等SSC: 通过 SCSI 、 ServerNET 来直接控制 I/O设备；

SSC 中含有 SP ,具有 SP 的功能。 SP 功能：1 、当MM 初始化时， SP 引导主机 BOOT;

2 、系统正常工作时，可 telnet 到 SP 平台上作操作维护和故障诊断。

XC

XC Functions

The Transcoder (XC) provides:

• Speech transcoding (PCM <-> CELP)

• Span line interfaces supporting EI, TI and JT1

• Span line grooming with subrate multiplexing on BTS

connections

• BTS link termination

• Switching of signaling links

- MM and MSC

- BTSandMM

- XCandMM

• Optional echo cancellation

协议转换功能

BSAP BSAP

Physical interface(Toking Ring Fiber and E1 Span line)

TCP/IP LAPD

BSAPBSAP

LAPDTCP/IP

MM FEP BTS

FEP: 完成联路层协议转换 TCP/IPLAPD

LAPD:Link Access Protocol ‘D’ (LAPD) is the transport software used to insure application data sent and received reliably.

OMCR &UNO

OMC-RThe OMC-R provides maintenance and control for 1 to 8 BSSs.• Operations and maintenance functions: - Database management » BSS configuration database control for the Transcoder and BTS devices - Fault management » Monitor and/or filter system events » Produce event logs and call detail logs » Command line interface for event management - Performance management » Usage measurement » Performance reports

UNO

• The UNO provides a Graphical User Interface (GUI) for system

maintenance.

- Terminals provide multiple user interfaces to the system for

day to day operations

- Single terminal can provide multiple jobs to be open at the

same time

• Receives and filters information from the OMC-R to provide:

- Alarm management

- Performance management

- BTS download manager

System Interconnection

DSU

Signal Flow