5 Performance requirements for main line
22.2893GPPMobile communication system for railwaysRelease 17TS
5.1 Environmental conditions
Rail communication is subject to much diverse limitations in urban and sparsely populated areas. Depending on the landscape, the construction of tunnels, e.g. underground or mountain crossing, or the construction of new tracks, the embedding of railway lines within aisles, through uninhabited areas is required. Tunnels are specific and require separate consideration in signal propagation through the changing fill factor. Here, the use of leaky feeder cables is essential.
Crucial constraints for the provision of performance factors are summarized in a non-exhaustive list below:
- Free space;
- Railway corridors in general and especially in hilly terrain;
- Railway corridors through forest areas;
- Underground / tunnel environment;
- Moving trains or objects in a railway station and shunting yards;
5.2 Low latency and high reliability
5.2.1 Overview
In future, for example trains will simultaneously exchange control information and status information with the responsible traffic management system on the ground. This procedure is a key factor for automated operation without a driver. Nonetheless, also traditional voice communication is needed to allow train staff to communicate with the ground staff.
Trains are operated at speeds up to 500 km/h. Under these conditions voice, video and data communication are to be provided. Especially train control communication is of extreme importance to ensure passengers safety.
In normal rail operation and in the context of Grade of Automation (GoA3 and GoA4) video/radar/lidar sensors on trains and on ground will be used to:
- detect hazards on tracks, and
- ensure a safe passenger (dis-)embarkation (e.g., ensure that passengers are not stuck in doors, or between platform and train, when trains depart, and trigger emergency braking or postpone train departure if any hazardous situation is detected).
The relative braking distance of a rail vehicle is an important indicator of the safety, which is significantly influenced by the transmission reliability between train and controller at low speeds up to 40 km/h. This mainly applies to the entry and exit of trains in the station area or displacement manoeuvres within marshalling yards. The reliability and latency of the transmission of the control command signalling of speeds up to 40 km/h has a direct impact on the braking distance.
5.2.2 Scenarios and KPIs for main line
To support this various voice, video and data categories,the following rail communication scenarios under the aspect of train speed shall be considered:
- Voice Communication for operational purposes impacting train safety
- Critical Video Communication for observation purposes with indirect impact on train operation, e.g. passenger surveillance;
- Very Critical Video Communication with direct impact on train safety- related critical train control and operation, e.g. used in driverless (e.g. Grade of Automation – GoA3/GoA4) operation for automated detection of objects (no human in the loop) or video-based remote control (human in the loop);
- Standard Data Communication used for the exchange of train diagnostic information or communication relevant information;
- Critical Data Communication for present rail traffic management systems;
- Very Critical Data Communication for enhanced intelligent rail traffic management systems e.g. full automated train control systems (driverless – remote control); requires high reliable transmission and preservation of the response pattern;
- Messaging for the reliable exchange of short information e.g. train departure procedure;
|
Scenario |
End-to-end latency |
Reliability (Note 1) |
Speed limit |
User experienced data rate |
Payload size (Note 2) |
Area traffic density |
Service area dimension |
|
Voice Communication for operational purposes |
≤100 ms |
99,9% |
≤500 km/h |
100 kbps up to 300 kbps |
Small |
Up to 1 Mbps/line km |
200 km along rail tracks |
|
Critical Video Communication for observation purposes |
≤100 ms |
99,9% |
≤500 km/h |
10 Mbps |
Medium |
Up to 1 Gbps/km |
200 km along rail tracks |
|
Very Critical Video Communication with direct impact on train safety |
≤100 ms |
99,9% |
≤500 km/h |
10 Mbps up to 20 Mbps |
Medium |
Up to 1 Gbps/km |
200 km along rail tracks |
|
≤10 ms |
99,9% |
≤40 km/h |
10 Mbps up to 30 Mbps |
Medium |
Up to 1 Gbps/km |
2 km along rail tracks urban or station |
|
|
Standard Data Communication |
≤500 ms |
99,9% |
≤500 km/h |
1 Mbps up to 10 Mbps |
Small to large |
Up to 100 Mbps/km |
100 km along rail tracks |
|
Critical Data Communication |
≤500 ms |
99,9999% |
≤500 km/h |
10 kbps up to 500 kbps |
Small to medium |
Up to 10 Mbps/km |
100 km along rail tracks |
|
Very Critical Data Communication |
≤100 ms |
99,9999% |
≤500 km/h |
100 kbps up to 1 Mbps |
Small to Medium |
Up to 10 Mbps/km |
200 km along rail tracks |
|
≤10 ms |
99,9999% |
≤40 km/h |
100 kbps up to 1 Mbps |
Small to Medium |
Up to 100 Mbps/km |
2 km along rail tracks |
|
|
Messaging |
– |
99.9% |
≤500 km/h |
100 kbps |
Small |
Up to 1 Mbps/km |
2 km along rail tracks |
|
NOTE 1: Reliability as defined in sub-clause 3.1. NOTE 2: Small: payload ≤ 256 octets, Medium: payload ≤512 octets; Large: payload 513 -1500 octets. NOTE 3: Estimates of maximum dimensions. |
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Table 5.2.2-1 Performance requirements for rail scenarios – main line
NOTE: All values in Table 5.2.2-1 are target values and assumes the use of a dedicated network for rail communication.
End-to-end latency and reliability of the communication scenarios listed in Table 5.2.2-1 shall be applied separately from the individually used priority of the communication.
To support off network communication, data categories, the following rail communication scenarios under the aspect of train speed shall be considered:
- Very Critical Data Communication for enhanced intelligent rail traffic management systems e.g. virtual coupling; requires high reliable transmission and preservation of the response pattern;
|
Scenario |
End-to-end latency |
Reliability (Note 1) |
Speed limit |
User experienced data rate |
Payload size (Note 2) |
Area traffic density |
Service area dimension |
Max required communication range (meters) (Note 4) |
|
Very Critical Data Communication |
≤100 ms |
99,9999% |
≤500 km/h |
100 kbps up to 1 Mbps |
Small to Medium |
Up to 10 Mbps/km |
3 km along rail tracks |
[1000 ~ 3000] |
|
≤300 ms |
99,9% |
≤40 km/h |
100 kbps up to 1 Mbps |
Small to Medium |
Up to 100 Mbps/ km |
3 km along rail tracks |
[1000 ~ 3000] |
|
|
NOTE 1: Reliability as defined in sub-clause 3.1. NOTE 2: Small: payload ≤ 256 octets, Medium: payload ≤512 octets; Large: payload 513 -1500 octets. NOTE 3: Estimates of maximum dimensions. NOTE 4: Relevant for Off-Network MCData Service only, supporting train platooning. All trains in a platoon are driving in the same direction. |
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Table 5.2.2-2 Performance requirements for rail scenarios – off network communication
5.2.3 Communication establishment
The duration of time for establishing a communication between entities, e.g. after network change or loss of communication, the braking distance between vehicles and its impact to the risk integral is crucial. Based on this, the following communication setup times of a communication shall be provided:
|
Type |
FRMCS |
Interworking with GSM-R |
Interworking with LMR |
|
Immediate communication session establishment |
≤1 sec |
≤1 sec + call setup time as defined in table 3-1 [8] |
≤1 sec + LMR call setup time (Note 1) |
|
Normal communication session establishment |
≤3 sec |
≤3 sec + call setup time as defined in table 3-1 [8] |
≤3 sec + LMR call setup time (Note 1) |
|
Note 1: In the interworking, the setup times are considered with 3GPP side only. Extra times may be applied depend on interworking communication technology. |
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Table 5.2.3-1 Communication setup times