Performance and Design of Turbo Codes on Rayleigh Fading Channels

Fading in wireless environments is a major obstacle to reliable communications. In order to mitigate the e ects of fading, channel coding is often employed. In this thesis, the performance and design of the channel coding technique, turbo codes, [1] is examined over Rayleigh fading channels. The thesis considers coherent BPSK signaling over both time-correlated and fully-interleaved Rayleigh, slow-fading channels with additive noise. The performance analysis begins with simulation results for typical turbo schemes in regions of low signal-to-noise. The e ects of block length, turbo decoder iterations, channel side information and channel correlation are examined. For regions of higher signal-to-noise, an average upper bound is developed and applied to a variety of fading conditions. The bound serves to illustrate the achievable performance of turbo codes and the e ects of block length and constituent encoder choice in the performance of turbo codes. Following from the performance analysis, this thesis outlines criteria for optimizing turbo codes for fading channels. In this analysis, design criteria are developed for the turbo interleaver on both fully-interleaved and correlated channels. For time-correlated channels, alternative interleaving schemes are proposed and studied through simulations. i