Apostolos Rizos

PR-Shaped, Coded Linear Modulations and Low-Complexity Approaches for their Detection

ABSTRACT:

In this thesis we investigate the combination of Partial Response (PR) Shaping and Trellis Coded Modulation (TCM), to obtain bandwidth efficient signals that are suitable for wireline high-bit-rate data transmission. PR shaping introduces correlation between successive symbols, hence decreasing the bandwidth occupancy of the signal. The penalty is that, in general, it also reduces the Euclidean distance between the transmitted signals, thus increasing the symbol error probability. We investigate the trade-off between bandwidth efficiency and reduced Euclidean distance and indicate the cases where PR-TCM schemes are advantageous compared to more traditional full response schemes. A significant part of our research focuses on receiver schemes for a PR-TCM encoded signal. The complexity of the optimum receiver for PR-TCM is relatively large, and increases significantly with the use of a large constellation size. We propose the use of reduced-complexity schemes, namely the M- and T- algorithms and the family of RSSE/DFSE detectors, for the detection of PR-TCM signals and show that one can obtain near-optimum performance at a much lower computational cost. With respect to the system design of a PR-TCM scheme, we indicate how an efficient PR shaping pulse may be obtained, and show that the best approach for detection at the receiver is the transformation of the shaping pulse into a well-defined short target response, followed by a low-complexity sequence estimation scheme. We also search for the optimum TCM code that is matched to each PR target response. Finally, we investigate the performance of a PR-TCM scheme in a non-AWGN channel case. We show that the detection framework proposed above can be directly applied in a dispersive time- invariant ISI channel. In the case of a time-varying fading channel, a different approach has to be taken and we examine its performance compared to the bound obtained by the ideal, non-realizable scheme.

Thesis Committee:
Prof John Proakis Advisor
Prof Masoud Salehi
Prof Milica Stojanovic