1 overview

 

GSM-R is a digital railway command and dispatch communication system specially developed by UIC and ETSI for the wireless mobile communication of European railways. It is based on the public network GSM, and adds the corresponding special dispatch communication function of railway.Railway in our country is based on this standard, and formulate the corresponding railway GSM - R digital mobile communication system development and construction planning, norms and standards, successively in qinghai-tibet railway, daqin line, JiaoJiXian respectively by nortel, huawei, Siemens GSM - R system test section was established, with the function of the GSM - R system of our country railway, regulations and standards for further verification, perfect.

 

Basic functions of the system

 

GSM-R system not only provides voice and data services, but also provides special functions such as functional addressing, location-based addressing, broadcast calling, emergency calling and direct mode for railway application.The railway application features are:

 

1) Dispatching and communication: train dispatch, freight dispatch, traction power supply dispatch, shunting operation communication of marshalling station, etc.

 

2) Construction maintenance communication.

 

3) Special communication: public works, electricity, power supply, water and electricity, maintenance, public security and other special communications.

 

4) Train and ground data: using GPRS, it can carry out data communication services such as train control system information transmission, locomotive synchronous control information transmission, train tail information transmission, scheduling command transmission, shunting wireless locomotive signal and monitoring information transmission, wireless train number transmission, stopping and stability information at the station, and transmission of vehicle access information.

 

5) Passenger Service: GPRS is adopted to provide transmission channels for passenger information service, mobile Internet, passenger train ticket sales, etc., and application terminals are provided by relevant professionals.

 

Basic composition of the system

 

GSM-R system is generally composed of seven subsystems: switching subsystem (SSS), base station subsystem (BSS), general packet wireless service system (GPRS), mobile intelligent network system (IN), fixed subscriber access switch (FAS) system, operation and maintenance subsystem (OMC) and terminal subsystem.Some data include FAS into SSS subsystem.The structure of GSM-R system is shown in the figure below:

3.1 Switching Subsystem (SSS)

 

The switching subsystem includes: gateway mobile switching center (GMSC), mobile switching center (MSC), access location register (VLR), home location register (HLR), authentication center (AUC), group call register (GCR), network interconnection function module (IWF), short message center (SMSC), acknowledgement center (AC), fixed subscriber access switch (FAS) and other equipment.

 

3.2 Base Station Subsystem (BSS)

 

Including base station transceiver (BTS), base station controller (BSC), encoding, decoding and rate mismatch unit (TRAU), cell broadcast short message center (CBC) and other equipment.

 

3.3 General Packet Radio Service Subsystem (GPRS)

 

Realize the packet wireless data transmission service of GSM-R system.It mainly includes gateway support node GGSN, business support node SGSN, packet control unit PCU, domain name server DNS and other devices.

 

3.4 Mobile intelligent network subsystem (IN)

 

The services provided by the intelligent network system include: function addressing, location-based addressing, dynamic call group based on train number function number, automatic acquisition of dispatching center IP address, flexible call restriction, etc.It mainly includes service exchange point (SSP), intelligent peripherals (IP), service control point (SCP), service management system (SMS) and other devices.

 

3.5 Fixed subscriber access switch (FAS) subsystem

 

Including the Ministry of Railways FAS, Railway Bureau FAS, Railway Sub-bureau FAS and Station FAS.

 

3.6 Operation and Maintenance Subsystem (OMC)

 

It includes wireless network management subsystem (OMC-R), switched network management subsystem (OMC-S), digital service management subsystem (OMC-D), repeater and repeater management subsystem (OMC-T), FAS network management system, etc.

 

3.7 Terminal subsystem

 

Including fixed terminal, mobile terminal and other equipment.

 

Fixed terminal includes: dispatch terminal, station terminal and other user telephones, as well as equipment such as call recording and recording system.

 

Mobile terminal: composed of mobile device and SIM card.Including: locomotive integrated communication equipment, train control data transmission equipment, portable platform, etc.

 

4. Network mode

 

In China's Railway GSM-R Digital Mobile Communication Development and Construction Plan, the planning of China's railway GSM-R network is described in detail.

 

4.1 Core Network

 

The GSM-R core network adopts the secondary network structure, and sets up the Mobile Service Regional Connecting Center (TMSC) and the Local Network Terminal Bureau (MSC).

 

The whole road plans to set up six regional junction centers (TMSC) in Shenyang, Beijing, Shanghai, Wuhan, Chengdu and Lanzhou, which will be responsible for the junction of circuitry exchange information and the transfer of long-distance incoming and outgoing traffic.Depending on the volume of calls, the TMSC can be set up independently, or it can be used as both a mobile terminal office and a mobile service switching center of a junction center.

 

MSC is based on specific lines, business model and user capacity, etc., and the location of MSC is selected reasonably. Generally, MSC is located in each road bureau or branch office with large volume of business.Each MSC and GMSC of each mobile service local network is connected with at least two TMSCs, and the network between the TMSCs is mesh network.If there is a large volume of business between any two mobile terminals, direct relay can be established.Set a direct relay between two MSCs adjacent to the coverage area.The national GSM-R network structure is shown in the following figure.

 

  

 

4.2 Wireless Network

 

GSM-R wireless network is composed of some cells (a base station or the area covered by a certain sector of the base station) along the railway and in the station. Each cell has one or several base station transceivers, the number of which is determined by the communication density.A base station controller is responsible for managing a certain number of cells.The base station is connected to the mobile switch/access location registry (MSC/VLR), which is connected to all the links and provides an interface with other networks.

 

In general, BTS is set at each station. In the interval, it is set reasonably according to the field strength coverage prediction and the topography and landforms along the line.In the mountainous area, tunnel, cutting and other weak field areas, optical fiber direct discharge, RF direct discharge station or leakage coaxial cable and other technical measures are generally adopted.

 

Here are the two basic ways of networking:

Fig. 1 Logical block diagram of radio station in station station

 

Fig. 2 Logical block diagram of station platform with wire station