A study of CPFSK trellis modulation codes on Gaussian and non-Gaussian channels

Liyanapathirana, Ranjith (1995) A study of CPFSK trellis modulation codes on Gaussian and non-Gaussian channels. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (26MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The objectives of this study are to find improvements to CPFSK trellis modulation codes on AWGN channels, and to investigate the effectiveness of using suboptimum coherent phase detection of CPFSK signals on non-Gaussian channels. A simplified, time-invariant, finite-state trellis is introduced for M-CPFSK signals. Based on this, a matrix representation is formulated for M-CPFSK with h ≤ 1/M. A class of fixed-h binary nonlinear CPFSK trellis modulation codes is constructed and analysed. Numerical results indicate that, for a given complexity, binary nonlinear CPFSK schemes can be designed so that they achieve the maximum memory length allowed by the number of trellis phase states. When h = 1/M, the optimum binary nonlinear CPFSK schemes exhibit coding gains of upto 2.2 dB compared with MSK signalling. The suboptimum coherent phase detection technique for CPFSK is a detection technique that has been directly adapted from PSK. Implementation of this detector is much simpler than that of the correlation receiver. Based on a code search subject to a set of heuristic design rules, self-transparent 4-CPFSK and 8-CPFSK trellis modulation codes with h ≤ 1/M are found for the carrier phase offset channel. It is found that the best self-transparent codes for M-CPFSK with h ≤ 1/M are identical with the optimum codes for the classical Gaussian channel found in the literature. Using the conventional method of computing an equivalent minimum distance, the performance of suboptimum coherent detection of CPFSK is evaluated on carrier phase offset channels. It is found that 8-CPFSK trellis modulation codes are more susceptible to carrier phase offsets than 4-CPFSK trellis modulation codes. Channel cutoff rate bounds are calculated for coherent PSK and suboptimum coherent CPFSK on (i) the AWGN channel and (ii) the mobile satellite channel modelled as a Rice fading channel with a steady line-of-sight component. It is shown that suboptimum coherent detection of 4-CPFSK is inferior to 4-PSK, but suboptimum coherent detection of 8-CPFSK with h ≥ 1/4 and 16-CPFSK with h ≥ 1/8 offer better coding potential than coherently detected 8-PSK and 16-PSK, respectively. This makes suboptimum coherent detection of 8-CPFSK and 16-CPFSK more attractive alternatives to PSK signalling on mobile satellite channels.

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