Iterative Channel Estimation of Multipath-faded Hybrid Data Transmission for Multimedia Satellite Broadcasting

†Summary Two schemes of iterative feedback channel estimation of the hybrid data transmission technique are proposed for coherent detection in a frequency-selective fast Rayleigh fading channel. Analyzed hybrid data transmission technique for multimedia satellite TV communications is that the main-channel data and subchannel data are simultaneously transmitted using QPSK modulation and 2ASK modulation, respectively, but the latter modulation timing is offset by half the main-channel QPSK symbol length in time. In a frequency-selective fast Rayleigh fading channel, two candidates of the iterative feedback channel estimation are proposed. One of the proposed channel estimation feeds back the re-modulated main-channel symbols only, and another feeds back the re-modulated both main-channel symbols and sub-channel symbols. The BER performances achievable by the use of two candidates are evaluated by means of computer simulations. The channel estimation using only remodulated main-channel symbols can minimize BER performances of the main-channel if Eb/N0 is lower than a change-over point. The channel estimation using both remodulated main-channel and sub-channel symbols can minimize BER performances of the sub-channel and can achieve almost the same main-channel BER performances as the only re-modulated main-channel symbols, if Eb/N0 is higher than a change-over point. Therefore, if Eb/N0 is higher than the point, the iterative channel estimation using both re-modulated main-channel and sub-channel symbols is considered to be the optimum, while if Eb/N0 is lower than the point, the channel estimation using only remodulated main-channel symbols is considered to be the optimum.