Repeat-punctured turbo trellis-coded modulation.

Abstract

Ever since the proposal of turbo code in 1993, there has been extensive research carried out to improve both the performance and spectrum efficiency. One of the methods used to improve the spectrum efficiency was to combine turbo code with a trellis-coded modulation scheme, called turbo trellis-coded modulation (TTCM). The scheme is used in various applications such as deep-space communication, wireless communication and other fields. It is a well established fact that an increase in an interleaver size of a TTCM system results in an improved performance in the bit error rate (BER). In this thesis repeat-punctured turbo trellis-coded modulation (RPTTCM) is proposed. In RPTTCM, the effect of repeat-puncture is investigated on a TTCM system, repetition of the information bits increases the interleaver size, followed by an appropriate puncturing scheme to maintain the respective code rate. The TTCM and RPTTCM systems are simulated in an Additive White Gaussian Noise (AWGN) channel. To understand how the RPTTCM scheme will perform in a wireless channel, the Rayleigh flat fading channel (with channel state information known at the receiver) will be used. The BER performance bound for the TTCM scheme is derived for AWGN and Rayleigh flat fading channels. Thereafter repeat-punctured is introduced into the TTCM system. The BER performance bound is then extended to include repeat-puncturing. The performances of the TTCM and RPTTCM systems are then compared. It was found that the RPTTCM system performed better at high signal-to-noise ratio (SNR) in both AWGN and Rayleigh flat fading channels. The RPTTCM scheme achieved a coding gain of approximately 0.87 dB at a BER of for an AWGN channel and 1.9 dB at a BER of for a Rayleigh flat fading channel, for an information size of N=800.