GSM-R: The best choice for railway communications

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GSM-R: The best choice for railway communications [Copy link]

GSM-R is a digital wireless communication system developed specifically for railway applications. Experts believe that GSM-R has the advantages of being more adaptable to the characteristics of railway transportation, more mature technical advantages, and more in line with the development of integrated communication signal technology.

　　The operating frequency

　　GSM-R system can operate in the entire frequency range of 876 to 960 MHz, but CEPT (European Postal and Telecommunications Conference) has designated a dedicated frequency band for the railway communication system of European countries, namely the GSM-R frequency band of UIC (International Union of Railways): 876 to 880 MHz for mobile station to base station (uplink), and 921 to 925 MHz for base station to mobile station (downlink).

　　GSM-R chooses to work in the 900MHz band for the following reasons: it is suitable for communication of 500km/h high-speed moving bodies (maximum Doppler shift is 415Hz); it is resistant to electric railway spark interference (the frequency of sparks is mostly concentrated in 400-800MHz); the typical coverage distance is about 5-10 kilometers, which is the minimum range to ensure system capacity and service quality for high-speed trains; it is more suitable for communication in tunnels (relative to 450MHz and 1800MHz bands).

　　System structure and coverage

　　GSM-R can form a network with both planar coverage and chain coverage, which can be used for both regional coverage and national coverage. For example, chain coverage is used along the railway line, and planar coverage is used in stations and hubs. In order to meet the high reliability of railway transmission, chain coverage generally adopts a dual redundant overlapping cell structure, with every two base stations (BTS) overlapping one cell; planar coverage adopts a multi-cell (or multi-sector) cellular structure, with each base station (BTS) covering one cell. Of course, an overlapping coverage cell structure can also be used.

　　Functional Features

　　GSM-R is based on the GSM platform. Therefore, in addition to the handover and roaming features of GSM, GSM-R also has the following proprietary features:

　　Functional Addressing (FA): A way for fixed (mobile) users to dial mobile users on trains.

　　Location Dependent Addressing (LDA): A way for mobile users on trains (such as train drivers) to call fixed users (dispatchers). For example, when the train driver calls a fixed user (dispatcher), the system addresses the fixed user (dispatcher) based on the current location (control area/cell) of the mobile user (train driver) and automatically transfers the call to the dispatcher in the control area where the train is currently located.

　　Voice Broadcast Service (VBS): VBS can be used to broadcast messages or issue emergency calls (point-to-multipoint calls, the caller speaks and many called parties can only listen) within a specified area (can span multiple cells). The definition and selection of areas can be set dynamically, which has great flexibility.

　　Voice Group Call Service (VGCS). Mobile or fixed users can dial the group call ID number to establish a call with group members in the specified area. All members of the group can answer the call through the same service channel; members of the group can also

　　send a call request through push-to-talk (PTT). The system establishes an uplink to provide call service based on the principle of "first request, first served".

　　Enhanced Multi-Level Precedence and Pre-emption (eMLPP). Many communication applications such as railway emergency calls or automatic train control require that the network can quickly establish calls regardless of the load condition. If congestion occurs in a radio cell (all radio frequencies and service channels are occupied), eMLPP can immediately disconnect low-priority calls and give priority to high-priority calls.

　　Suitable for railway communications

　　GSM-R, in addition to the above-mentioned functional characteristics, is also reflected in the following railway business applications.

　　Train Control System (TCS): It is a train automatic protection/train automatic control system that uses GSM-R as a transmission means, and can even realize automatic train operation (driving).

　　Railway maintenance communication: Use GSM-R to establish business contact communication (new roadside telephones and tunnel telephones) for maintenance personnel along the railway. And be able to quickly determine the location of maintenance personnel based on their functions and locations.

　　Train diagnosis: If a train breaks down, the diagnostic data will be transmitted to the next maintenance center via GSM-R. This enables the maintenance station to make relevant preparations for maintenance in a timely manner, thereby greatly shortening the maintenance time.

　　Passenger services: including train timetable information and online ticket (seat reservation) services. The train timetable information service based on train automatic control and GSM-R can provide passengers and passengers with dynamic location and timetable information of the train at any time; ticket machines based on GSM-R connection can provide online ticket (seat reservation) services.

　　Freight tracking service: Using a simple GSM module with a GPS receiver, the precise location of the truck (container) can be indicated, the exact location of the transported goods can be grasped in real time, and this data can be sent to its customers.

　(Source: China Communication Equipment Business Network)