Coded Decision-Directed Channel Estimation for Coherent Detection in Terrestrial DMB Receivers

This paper proposes a coded decision-directed (DD) channel-estimation method with two-dimensional averaging for T-DMB receivers. Since the noncoherent differential demodulation of existing T-DMB receivers can not track channel variation, it may not work well in fast-fading channels. To overcome this problem, coherent detection based on channel estimation is introduced. The proposed method re- modulates the output of the soft-decision Viterbi decoder for coded DD channel estimation to obtain more accurate decision symbols than hard-decision symbols. To both mitigate the effects of noise and smooth incorrectly-estimated coefficients, the estimated channel coefficients are two- dimensionally averaged. The enhanced accuracy leads to the high-performance DQPSK demodulation robust to Doppler spread and noise. The proposed method may also contribute to the launch of the future T-DMB service of providing a higher data rate. Simulation results show that the proposed scheme performs much better than the conventional method, especially at high speed-moving receivers.