Impact of carrier frequency offset, Doppler spread and time synchronisation errors in OFDM based single frequency networks

The orthogonal frequency division multiplexed (OFDM) scheme allows all transmitters in a radio broadcasting network to transmit identical signals in the same frequency block, forming a so called single frequency network (SFN). The simultaneous transmission creates a severe artificial multipath propagation, which translates into intersymbol interference (ISI). The extra large symbol duration needed in SFN to prevent ISI has raised doubts concerning the performance at high carrier frequencies and high mobile receiver speed. Normally the receiver in an SFN is experiencing a diversity gain of receiving several signals. However, if the received signals are exposed to different carrier offsets and Doppler spread it will lead to interchannel interference (ICI), resulting into performance degradation. A method to analyse the performance including ISI and ICI is presented. The increased outage probability caused by the presence of frequency offsets at the transmitter sites and Doppler spread is then evaluated. Furthermore, the frequency offset and time synchronisation errors at the receiver is also investigated.