Synchronizability of OFDM signals

This paper deals with symbol timing and carrier phase estimation for orthogonal frequency division multiplexed signaling (OFDM) in satellite/terrestrial systems. For transmission over frequency selective channels, a synchronizer at the receiver estimates the phase rotation of each individual carrier; the synchronizer can not distinguish between the phase shift introduced by the channel and by a symbol timing delay. It is shown that for transmission over a nondispersive channel (e.g. fixed satellite link) this algorithm performs suboptimal as compared to a synchronizer which separately estimates the unknown phase and timing. A lower bound on the timing error variance and phase error variance for both synchronizers is calculated. The BER degradation due to imperfect estimation of the timing and phase is given.