Doppler effects on single-carrier signals operating in fading channels

Abstract

This thesis examines the performance of single-carrier systems in a fading channel environment. A transmission through a fading channel results in changes in phase and amplitude that degrade system performance. A pilot symbol in a single-carrier system can determine the channel characteristics, allowing reliable system performance. The differential decision feedback and double differential-decision feedback algorithms compensate for Doppler error by updating the channel phase estimation between each symbol. To determine the performance of single carrier systems in a fading environment, this thesis used MATLAB simulations. Each algorithm was tested for a variety of conditions to determine performance characteristics. Simulations for QPSK, 16-QAM and 64-QAM were implemented to test bandwidth efficient modulation using pilot symbols. Higher order QAM signals are less tolerant to phase errors since the signal constellation points are more densely located. These simulations showed that both algorithms can effectively compensate for Doppler errors in a fading channel with similar performance. In most situations the differential-decision feedback algorithm performed marginally better than the double-differential decision feedback algorithm.