Performance of DS-CDMA communication systems with generalized offset QPSK modulation.

Abstract

In this thesis, we consider the performance of direct-sequence spread-spectrum multiple-access communication systems using generalized offset quadrature phase shift keying schemes. In particular, we explore the effect of the chip waveform used on the overall performance of these systems. In the first part, we provide a comparative analysis of the error and bandwidth performance of several modulation schemes over unfaded single-path additive white Gaussian channels. We then extend the analysis to the case of multipath fading channels, and we study and compare the impact of different diversity reception schemes as means to improve performance. In the second part, we present a method to design signalling formats with optimal chip waveforms that minimize the multiple-access interference power under a number of constraints pertaining to fixed transmitted power, limited out-of-band emission, phase continuity and envelope uniformity of the transmitted signals. In the final part, we study performance degradation under more realistic channel models that include band-limiting filters and nonlinear amplification. The final results drawn from this work allow for the use of various figures of merit to provide a comprehensive performance comparison among conventional modulation schemes and newly designed ones for direct-sequence code-division multiple-access communication applications.