ADAPTIVE COHERENT RECEIVERS FOR DIGITAL SIGNALS OVER THE GAUSSIAN CHANNEL WITH UNKNOWN CARRIER PHASE/FADING

Conventionally, it has been assumed that coherent detection over the Gaussian channel has to be achieved with the use of some carrier tracking phase-locked-loop. However, in practice, the phase-locked-loop has limited applications, especially when fading channels are involved. In this thesis, two channel estimation receiver structures for the coherent detection of digital signals transmitted over the Gaussian channel with unknown carrier phase/fading are presented. The two receiver structures concerned are namely the symbol-by-symbol receiver and the sequence estimation receiver while the modulation techniques considered are MPSK and binary orthogonal signalling. The channel estimation receivers have a detector-estimator structure in which the estimator is responsible for generating an accurate channel estimate to facilitate the detector in performing coherent detection. Both receiver structures include an adaptive filter for performing channel estimation. Extensive simulation results and theoretical studies show that the symbol-by-symbol receivers and the sequence estimation receivers perform well under the real world situation of imperfect knowledge of the carrier phase/fading and can achieve a bit error probability performance close to that of perfect coherent detection. The results also indicate that the sequence estimation receivers which utilise a Viterbi-type algorithm to perform efficient metric computations are superior over the symbol-by-symbol receivers in terms of bit error probability performance.

Author dc:creator

• CHUA KENG HONG