4 Railway communication functionality

22.2893GPPMobile communication system for railwaysRelease 17TS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

4.1 Bulk Transfer of CCTV archives from Train to Ground

4.1.1 Description

The video surveillance system in trains consists of multiple cameras which are recording and encoding the video feeds 24/7 either into the video recorders or into internal memory of the cameras themselves. The amount of video recordings is excessive, which exceeds rather fast the physical storage capacity that is available in video recorders and/or in cameras. The regulations in different countries are ruling retention time for recordings until up to 31 days or even more. However, the recordings need to be stored in the physical storages located in the vehicles for only seven days.

Next, an example estimation is provided to illustrate the offload performance with different uplink speeds, when the train is commuting from Helsinki to Kemijärvi. The parameters for the calculation are provided in Table 1, whereas the offload results for uplink speeds of 400 Mbps, 750 Mbps and 1000 Mbps are provided respectively in Figure 1.1.1-2, Figure 1.1.1-3 and in Figure 1.1.1-4.

Station Arrives Departs Stop time Time between stations

HELSINKI 18:52

PASILA 18:57 19:00 0:03 0:08

TIKKURILA 19:41 19:44 0:03 0:44

RIIHIMÄKI 20:19 20:22 0:03 0:38

HÄMEENLINNA 20:46 20:48 0:02 0:26

TAMPERE 21:38 22:11 0:33 1:23

PARKANO 23:03 23:06 0:03 0:55

SEINÄJOKI 0:08 0:10 0:02 1:04

KOKKOLA 1:37 1:39 0:02 1:29

YLIVIESKA 3:10 3:12 0:02 1:33

OULU 4:42 5:00 0:18 1:48

KEMI 6:08 6:12 0:04 1:12

ROVANIEMI 7:47 7:55 0:08 1:43

MISI 8:31 8:32 0:01 0:37

KEMIJÄRVI 9:00 9:05 0:05 0:33

Table 4.1.1-1. The parameters for the offload calculation for the train route between Helsinki and Kemijärvi.

Figure 4.1.1-2. The offload results with uplink speed of 450 Mbps.

Figure 4.1.1-3. The offload results with uplink speed of 750 Mbps.

Figure 4.1.1-4. The offload results with uplink speed of 1000 Mbps.

Based on the example estimations presented in the figures 4.1.1-1 – 4.1.1-4, the required throughput speed for the offload should be at least 1 Gbps.

Hence, in order to meet the requirement regarding the retention time and to minimize the required physical storage in the train, FRMCS needs to provide the means to transfer the CCTV archives from train to ground, i.e. enable means for CCTV offload.

In a CCTV offload system, FRMCS provides means for transferring video surveillance data between a mobile communication unit in the train and ground communication units located at the depot and at the stations and/or stops alongside the predetermined route of the train. Whenever the train approaches the stations and/or stops or arrives into the depot, FRMCS facilitates the communication between the ground and mobile communication unit. The mobile communication unit in the train forwards the video surveillance data from the video recorder and/or directly from video surveillance cameras. The generic offload procedure between the ground and mobile communication units could be e.g as described in the following;

– The ground communication unit is monitoring whether a transmission signal from the mobile communication unit is available and that the signal quality is sufficient for synchronization.

– Upon successful synchronization, the ground communication unit requests offload from the mobile communication unit and the connection between the ground communication and mobile communication unit is established as soon as the sufficient signal quality is acknowledged by the FRMCS and mobile communication unit.

– The transfer of CCTV archives from train to ground is started.

– The ground communication system forwards the offloaded data further to the ground storage.

– The transfer of CCTV archives continues as long as sufficient connection between the train and ground system is available and/or aborted by the FRMCS.

Rail-bound mass transit requires the same functionality, however, the CCTV offload is even more challenging due to the shorter stop times of commuter trains.

4.1.2 Requirements

[R4.1.2-1] FRMCS shall facilitate the CCTV offload from train to ground when, during the train stops the stations and/or stops, stations, and whenever the train arrives into the stops and at the depot.

[R4.1.2-2] The FRMCS shall be able to support that CCTV archives can be transferred into the ground system in a time and resource efficient way in dedicated places such as stations, train stops or train depots.

[R4.1.2-3] The CCTV offload shall be initiated by the ground communication unit, once the sufficient signal quality is available between the ground and mobile communication units.

[R4.1.2-4] The transfer of CCTV archives shall not affect mission critical communication.

4.2 Bulk transfer of multimedia from ground to train

4.2.1 Description

The offering of multimedia services to the passengers is becoming default service during long travels in airplanes and more and more, also in trains. In order to minimize the excessive consumption of network capacity between train and ground, a bulk transfer of multimedia databases from ground to train during stops at the stations and depots is optimal solution. The bulk transfer of multimedia is done when the train stops at the stations, stops and depot, ideally with minimum of one gigabit transfer speed. Hence, the multimedia content can be more versatile and updated in regular basis. The actual content is also consumed in-train network operated by the FRMCS and hence it does not give burden to the link budget between train and ground. The multimedia may contain movies, TV shows, cached webpages etc.

The bulk transfer of multimedia is facilitated by the FRMCS, which provides means for transferring the multimedia databases data between ground communication units, located at the depot, stations and/or stops alongside the predetermined route of the train. Whenever the train approaches the stations and/or stops or arrives into the depot, FRMCS facilitates the communication between the ground and mobile communication unit, if bulk transfer of multimedia transfer is requested. The ground communication unit uploads the multimedia databases from ground into the mobile communication unit in the train, where the data is stored in the train multimedia data storage. The generic procedure for the bulk transfer of multimedia between the ground and mobile communication units could be e.g as described in the following;

– The ground communication unit is monitoring whether a transmission signal from the mobile communication unit is available and that the signal quality is sufficient for synchronization.

– Upon successful synchronization, the mobile communication unit requests multimedia upload from the mobile communication unit and the connection between the ground communication and mobile communication unit is established as soon as the sufficient signal quality is acknowledged by the FRMCS and mobile communication unit.

– The transfer of multimedia databases from ground to train is started.

– The mobile communication system forwards the transferred multimedia databases further into the in-train storage.

– The transfer of multimedia archives continues as long as sufficient connection between the train and ground system is available and/or aborted by the FRMCS.

4.2.2 Requirements

[R4.2.2-1] FRMCS shall facilitate the transfer of multimedia archives from ground to train.

[R4.2.2-2] The FRMCS shall be able to support that multimedia databases can be transferred from ground to train in a time and resource efficient way, when the train stops at the stations, train stops and at the depot.

[R4.2.2-3] FRMCS shall facilitate communication capabilities provided by the train.

[R4.2.2-4] The transfer of multimedia databases shall not impact mission critical communication.

4.3 Massive Inter-carriage data transfer

4.3.1 Description

The inter-carriage links between train vehicles enable sufficient capacity to enable massive data transfer throughout the train required e.g. for transfer of CCTV archives, multimedia databases and live streaming as well as for control, operational, and passenger services. Mobile communication unit in train provides connection between carriages of the train used, e.g. for the transfer of CCTV archives to a central node in the train form which the connection to the ground system will take place.

4.3.2 Requirements

[R4.3.2-1] The FRMCS shall facilitate the onboard communication between carriages of a train, e.g. to collect CCTV content at one place on the train for transfer to the ground system.

[R4.3.2-2] The Inter-carriage links shall support at least the same throughput speed as the mobile communication unit of FRMCS providing the link between train and ground system.

[R4.3.2-3] The onboard communication between carriages of a train shall not impact mission critical communication.

4.4 Coexistence of automated train control with other train applications

4.4.1 Description

Train automation can be divided into control and operations. Both types consist of distributed applications that rely on dependable communication. Typically, control applications such as for automated train control are of higher priority than operational applications, and the latter are typically of higher priority than passenger services. One of the main challenges is to guarantee the premium priority of control-related communication over other types of communication, especially since the data bandwidth consumed for control is typically dwarfed by data traffic stemming from the other two application areas. Another challenge is to guarantee the super priority of operational data communication over passenger-related communication. Driverless trains are not the only source of automation in mass transit, and thus not the only source of dependable machine-type communication. For instance, mass transit train control (MTTC) including communication-based train control (CBTC) is also used for trains exhibiting lower grades of automation, if assisted by rail-to-rail-side wireless communication, which is at the core of driverless trains.

Communication services for MTTC have to coexist with other high-priority and low-priority communication services. This coexistence is done assigning priorities to the communications, see below an example of how these priorities can be allocated:

– The MTTC communication service might have the highest priority (train control).

– The CCTV communication service might have high-priority, but lower than MTTC.

– (High data rate) data communication services such as passenger internet access might be of low priority.

– Emergency calls need to be established on demand with a priority suitable to guarantee call success independent of already running communication services.

NOTE: This kind of emergency calls is using the train and rail infrastructure and not the public emergency services. An example for a train emergency system are microphone/speaker boxes that are integrated into the walls of the passenger area.

The setup of high data rate communication services with low priority does not have an impact on the communication services for train control. Furthermore, the start-up of a communication service for train control will acquire sufficient resources in the 5G network, even if high data rate communication services with low priority are already running.

4.4.2 Requirements

[R4.4.2-1] High priority communication services, especially their end-to-end latency and availability, shall not be affected by communication services of lower priority running in parallel.

[R4.4.2-2] The start-up of high-priority communication services shall not be affected by already running services with different priorities.