Trellis coding and adaptive estimation in dually polarized systems
Description
The author of this dissertation presents, analyzes and evaluates methods of improving the performance of digital communication systems in environments that introduce depolarization crosstalk, differential phase shift and Additive White Gaussian Noise (AWGN) Novel multidimensional Trellis Coded Modulation (TCM) schemes are presented and shown to greatly improve the performance of the systems over the equivalent uncoded formats. The redundancy for coding is introduced by utilizing a convolutional encoder and then mapping the output onto an expanded signal set. The constellation expansion is generated by using dual polarization, dual carrier frequencies, or consecutive time intervals The new schemes designed by the author are Phase/Polarization TCM, Phase/Frequency/Polarization TCM, and X8-TCM. They not only achieve considerable asymptotic and effective gains, but also have low redundancy, low modulation levels, low complexity, and constant envelope A reduction in the probability of error can also be achieved by using canceling filters. The optimum canceler receiver for dually polarized Offset Quadrature Phase Shift Keying (XPOL-OQPSK) is studied in this dissertation. This receiver is an adaptive Maximum Likelihood Sequence Estimator (MLSE), suggested by the inherent memory in systems which use dual polarization and offset between in- and quadrature-phase components, and by the varying statistics of the interferences. A simplified receiver (the MLSE-1) is also studied. Performance evaluations show that the new detection scheme permits XPOL-OQPSK to be used in instances where its use without cancellation would be precluded. A novel way of analytically predicting the performance of the MLSE detectors is also given The author also studies the Minimum Square Error (MSE) surfaces versus channel parameters or versus filters weights for the XPOL Binary Pulse Amplitude Modulation (BPAM) receivers The MSE surfaces themselves, their characteristics, and their critical points for several XPOL-BPAM systems are given. The study includes the conventional receiver, the fixed canceler receiver, and the adaptive canceler detector. Three different error signals are considered, depending on whether the signals used are those before or after the decision-making process