<p> Overview of the wireless communication system of Guangzhou Metro Line 5

1 System Overview The wireless communication system of Guangzhou Metro Line 5 uses the digital trunking wireless communication system based on TETRA standard of Dimetra IP produced by Motorola. The system uses TDMA technology, ACELP voice coding technology, π? 4-DQPSK modulation technology, in addition to meeting the traditional voice communication needs, but also uses the wireless data transmission channel provided by the wireless system, can transfer data between the ground system and the vehicle system information.

2 System functions Motorola Dimetra IP system has powerful functions, mainly providing services for dispatchers, wireless users, and network managers.
2.1 Basic system functions The Dimetra IP system can realize group calls, private calls (that is, single calls), emergency calls, multicast group calls, busy queuing and callback, priority queuing, dynamic reorganization, dynamic base station allocation, and cross-zone group calling , Time-limited calling, system main prompt tone and signal display and other functions.
2.2 System management function Dimetra IP system has a powerful network management function, its purpose is to configure, operate and maintain the system, in order to achieve high availability of the system and effective operation of the system. Network management functions include fault, configuration, statistics, performance and security management.
2.3 Data transmission function The Dimetra IP system supports data services such as status information services, emergency alarms, short data services, and packet data.
2.4 Virtual private network function Dimetra IP system supports virtual private network VPN (virtual private networks) technology, including providing multiple relatively independent (virtual and private for the use unit) dispatcher, user management terminal and multiple independent user IP networks Access. The concept and content of virtual private network VPN are concentrated on: VPN user management and billing terminal, mobile management for VPN users, dispatch and command center for VPN users, packet data transmission application of VPN users.
2.5 All the GPIOM equipment of the dispatching station of the recording function system can output the audio signal of the dispatcher's call, and provide a recording interface. The secondary development of the recording device can record the dispatcher's call.
2.6 Basic functions of dispatching station The dispatching station of Dimetra IP system supports group calls to main trains, receives RTT requests, initiates and receives emergency calls, initiates emergency calls to talk groups, initiates and receives private calls, and sends to vehicle stations or other user stations Short text information, refresh train information, receive short text information, receive status information, talk to other dispatchers, etc.
2.7 Main functions of user station:
The user station has functions such as group scan, priority monitoring, direct mode operation, emergency call, and speed dialing.

3 Equipment composition 3.1 Network construction method The Guangzhou Metro Line 5 wireless trunking communication system uses a single switching control device and multiple base stations to form a wired and wireless TETRA network. The main equipment is composed of central switching control equipment, base station, dispatching station, vehicle-mounted station, portable station, dispatching station, optical fiber repeater station, leaky coaxial cable and antenna.
3.2 The equipment constitutes the central switching equipment. The central switching equipment mainly includes: switching control equipment, data transmission console, centralized alarm, CAD server, TETRA network management terminal, recording equipment, printer, dispatch desk, etc.
The data transmission console receives the vehicle state information sent by the data locomotive platform and sends the passenger train display information to the data locomotive platform through the system's packet data gateway. The data transmission console is connected to the main control system through an RS422 interface.
The centralized alarm terminal uniformly receives the alarm information from the TETRA system, base station power supply, and fiber optic repeater, and transmits it to the upper alarm system. At the same time, it can be directly managed and configured directly with the fiber optic repeater. Base station power alarm, RS232 protocol is used for management and configuration of optical fiber repeater. Alarm information of repeater and base station power are uploaded to OCC through 10M Ethernet interface provided by RS232 / IP converter and transmission subsystem Alarm terminal.
The CAD server is a secondary development device. The cables connected to it are network cables, ATS signals, clock signals, power cables, etc.
The Dimetra IP system network management terminal can provide network management users with graphical user interfaces (GUI) for different network management applications. The network management terminal can be located at the main station or a remote station. The network management terminal of the Dimetra system is connected to the Ethernet switch in the central wireless equipment cabinet through the Ethernet interface.
The recording device is used to record the conversation of the talk group related to the dispatching station. The cables connected to the recording equipment include audio cables and power cables. [

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