Application of GSM in high speed trains: measurements and simulations

The paper presents results of measurements and simulations concerning the application of the European GSM system in high speed trains travelling at up to 500 km/h. The aim is to answer the question to what extent GSM (performance specified up to 250 km/h) can cope with the high velocities which are demanded for future railways. Measurements along railway lines have shown that a railway mobile radio channel results in better performance (Rice channel) than standard mobile radio channels (Rayleigh or weak Rice channel, see GSM-Recs). BER and block error rate of GSM traffic channels up to 500 km/h are simulated. Comparison of the results at 250 km/h and 500 km/h shows that the GSM high velocity problem can be solved either by increasing the SNR by about 2 dB or by increasing the Rice parameter c by about 6 dB (numerical values for profile RA=rural area; railway channel with c=6 dB against standard channel with c=0 dB), i.e. the BER at 500 km/h (railway channel) is not worse than the BER at 250 km/h (standard channel). A simple example shows that the benefit in the transmission of telegrams consisting of blocks of decoded bits can be much higher, The desired channel performance, i.e. a strong direct path (high Rice parameter), can be achieved by careful radio coverage planning along the railway line. This means a GSM standard receiver is sufficient to cope with the GSM high velocity problem and no additional means are needed.<
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