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High Speed Train Testing

HIGH SPEED TRAIN TESTING

 

High Speed Train Testing in Japan

 

High-speed trains (HSTs) are a major focus in China, Japan and many European countries. However, high Doppler shift and the consequent decrease in the demodulation performance can adversely affect the performance of mobile devices being used by high-speed train passengers.

 

LTE designed for usage at high speeds of up to 350km/h, may be fast in ideal conditions. However, there are a number of challenges such as rapidly changing radio environment and ‘spotty’ coverage that can affect the speed of LTE.

 

Problems resulting from these challenging conditions include high call drop rates and interrupted streaming. Data connectivity is particularly important for VoLTE calls which use an LTE data bearer with a QoS.

 

To ensure maximum performance of mobile devices used by high-speed train passengers, IoTAS have developed our own high speed train solution against specifications GPP TS 36.104 V8.2.0 and ETSI TR 125 913 V9.0.0.

Challenges

 

High speed trains are challenging due to the positioning of antennas at the side of the track, which means radio signals change very quickly. Challenges arising from these unfavorable conditions include:

 

  • Spotty Coverage
    • Train carriages act like a faraday cage with holes (windows).
    • Mountains, deep cuttings, viaducts and passing trains cause additional path loss.
    • Tunnels cause a rapid change of radio environment. Leaky feeders may not work well in long tunnels or at very high speeds.
    • Antenna are often placed next to the tracks, so the mobile use is moving at full speed towards and away from the Antenna.
  • Frequent handovers required to maintain connectivity. These may occur several times per minute, when the train is travelling at full speed for each mobile user. This causes high levels of signaling traffic.
  • Multipath and Doppler shift effect reduces receiver demodulation performance and lower data throughput speed and can effect QoS required for VoLTE calls.
  • Higher frequencies are more easily attenuated by the metal carriage whilst lower frequencies pass through more easily.

Problems Often Seen

 

Failure to effectively test LTE capability on high-speed trains can affect the performance of mobile devices for the end user in a number of ways:

 

  • Handover failures
  • Cell reselection failures
  • Slow call setup times
  • High call drop rates
  • Problem with voice call quality
  • Carrier Aggregation is challenging
  • Interruption of streaming services

IoTAS Test Areas

 

To ensure that the performance of mobile devices used by high-speed train passengers is at maximum performance IoTAS testing shall be conducted so as to cover:

 

  • System access and registration
  • Idle mode cell reselections
  • PS data handovers
  • Voice call setup performance (VoLTE and CSFB)
  • Data throughput performance (against a reference device)
  • Simultaneous PS data and VoLTE (long call)
  • Ping time
For more information about high speed train testing please get in touch.