Effects of non-uniform windowing in a Rician-fading channel and simulation of adaptive automatic repeat request protocols

Two aspects of digital communication were investigated. In the first part, a FFT-based, M-ary FSK receiver in a Rician-fading channel was analyzed to determine the benefits of non-uniform windowing of sampled received data. When a frequency offset occurs, non-uniform windowing provided better FFT magnitude separation. The improved dynamic range was balanced against a loss in detectability due to signal attenuation. With large frequency offset, the improved magnitude separation outweighed the loss in detectability. An analysis was carried out to determine what frequency deviation is necessary for non- uniform windowing to out-perform uniform windowing in a slow Rician-fading channel. Having established typical values of probability of bit errors, the second part of this thesis looked at improving throughput in a digital communications network by applying adaptive automatic repeat request (ARQ) protocols. The results of simulations of adaptive ARQ protocols with variable frame lengths is presented. By varying the frame length, improved throughput performance through all bit error rates was achieved.http://archive.org/details/effectsofnonunif1094527773Lieutenant, United States Coast GuardApproved for public release; distribution is unlimited