| In this dissertation we investigate bandwidth-efficient reliable communication over wireless channels. We consider a generalized serial concatenated trellis coded modulation (SCTCM) system consisting of an outer block or convolutional code, one or more inner codes preceded by interleavers, an optional channel interleaver, and a mapping to a higher-order, Gray-labeled signal constellation.; Bit-interleaved coded modulation (BICM) is a special case of the generalized SCTCM system. We investigate how the choice of interleaver impacts the performance of a BICM system for delay-constrained Rayleigh fading channels. It is shown that convolutional interleavers outperform square transposition interleavers and random interleavers for short interleaver lengths over a wide range of Doppler frequencies.; Next we consider SCTCM systems where the outer code is a repeat or single parity check code, and use one or more rate-1 interleaved accumulate codes as inner codes. Using the union bound, we show that under maximum-likelihood (ML) decoding, there exists a system-dependent threshold, such that if the signal-to-noise ratio (SNR) exceeds this threshold, the bit error probability goes to zero as the blocklength goes to infinity.; For finite blocklengths and ML decoding, we derive a probabilistic performance bound which improves on the conventional union bound.; We compute SNR thresholds for a non-ML, message-passing decoder using density evolution, assuming infinite blocklengths. For the particular case of an outer parity check code and one inner accumulate code, we derive a stability condition, which provides a lower bound on the SNR threshold.; We show that, for equiprobable signaling, the bit-wise log-likelihood ratio densities for higher-order constellations are symmetric. This property is used in the stability condition. Furthermore, the densities for the different bits can be averaged to a single density without significantly affecting the computed threshold values.; The simulated performance in AWGN and i.i.d. Rayleigh fading of the proposed SCTCM system is comparable to that of more complex systems suggested in the literature. The iterative decoding thresholds at high rates are within 1 dB of the channel capacity for higher-order constellations, and correspond well to simulation results. |
