# Structure of GSM-R

## GSM-R 的网络结构

电路交换部分(打电话部分):

![](/files/-Lf5hdxfOcfJjpXJ6bpw)

组成: 移动台(Mobile station, MS)，Base station subsystem(BSS)，Network switching subsystem(NSS)，Operation Support Subsystem(OSS)

> 这里的移动台分为: 1. OPH(Operational Purpose Handheld)(手持机)(比传统手机多两个键: PTT(push to talk)、紧急呼叫键)； 2.机载台(CIR)(Cab Integrated Radio)

### BSS(Base subsystem)

#### BTS(Base transceiver station):

由 天线、耦合系统(连接天线与收发信机的部分)、收发信机(TRX)、公共功能单元(BCF, base station control function) 构成

> A BTS is controlled by a parent BSC via the "base station control function" (BCF). The BCF is implemented as a discrete unit or even incorporated in a TRX in compact base stations.

一个 TRX 管理一个 TDMA 帧 = 1个频点 = 8个时隙 = 8个用户

一个`基站小区`有一个 TRX

一个`铁路位置区`至少有4个`基站小区` = 4个频点 = 4个TRX

> 按照概念的从大到小: 服务区 -> PLMN -> 若干MSC区 -> 若干位置区 -> 若干基站区

#### BSC(Base station controler):

由 处理单元、交换机矩阵单元、中继控制单元 组成

#### TRAU(Transcoder and Rate Adaptation Unit， 转码器 和 速率适配单元)

由 编(译)码器、控制器、外部PCM接口 组成

把`RPE-LTP编码`转为`PCM编码`

把`13kbit/s`转为`64kbit/s`

把BSC过来的`1线120个用户`转为`4线，毎线30个用户`，送给GMSC/VLR

### NSS(Network subsystem)

#### MSC(mobile switching center)

每个路局放一个，共19个

#### HLR(home location register)

#### VLR(visitor location register)

放置上，靠近MSC

#### AuC(authentication center)

#### EIR(Equipment Identity Register)

存储 IMEI(International Mobile Equipment Identity)

#### GCR(Group Call Register)

存储`移动用户组的ID`、`要呼叫的小区`信息 ...

放置上，也靠近MSC

#### IWF(inter-working function，互连功能)

MSC上的模块，可以让`GSM-R系统`与其他网络连接

#### SmS-SC(短消息服务中心)

在铁路上，并不被使用

### OSS(Operate subsystem)

OMC-R: 管理BSS, R is for radio

OMC-S: 管理NSS, S is for switch

OMC-F: 管理FAS, F is for FAS

## Question and Answer

### 简述 TRAU 的组成与功能

**组成**: 编(译)码器、控制器、外部PCM接口

**功能**:

把`RPE-LTP编码`转为`PCM编码`

把`13kbit/s`转为`64kbit/s`

把`1线120个用户`转为`4线，毎线30个用户`


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