Single Frequency Network System Coverage and Trial Testing of High Speed Railway Television System

Lin Gui, Wengeng Ma, Bo Liu, Hingkan Lu and Peixin Shen

IEEE Transactions on Broadcasting, Vol 56, No 2, June 2010 pp 160 - 170

A survey of passengers on Chinese high speed trains showed that 57% of passengers would most like to have real-time televsion available while travelling.  With 12,000 km of high speed railway line under construction, satisfying the television requirement is a major undertaking.

The researchers decided to use a standard digital television broadcasting technology and to determine what would be necessary to apply this to a high speed railway. A single frequency network was selected.

The coverage of the television network has been designed to match that of the GSM-R network serving the railway.  This reduces construction and maintenance costs and has been shown to be a very workable approach.  Traditional modulation/demodulation processes can not work successfully because there is strong multipath interference with opposite Doppler shift from adjacent base stations. 

To investigate the impact of multipath interference the authors proposed a simplified channel model with train mounted antennas designed for high front to back ratios and analysis of two strong signals.  The two path model is easier to analyse and provided a basis for the practical design.

Theoretical analysis of the model showed that reliable coverage should be feasible with this design approach.  A trial system was installed and tested on a train.  The results showed that with omni-directional antennas there are always some zones where reliable reception is not possible and these zones are in the middle of the coverage overlap area.  When directional coverage and diversity receivers were used, the performance over the entire test route was very good, except for two or three points.  Each of the points with interference lasts no longer than one second and was considered tolerable.

The full paper is available from the IEEE.