Comparisons of digital communications systems in fading channels via importance sampling simulation
Abstract
The evaluation of the bit error rate (BER) performance of digital communication systems is often done via simulation on computers. Traditionally, Monte Carlo method is effectively the only practical way to evaluate the BER for complex channel models. But for very low BER, this method requires excessive computer time. Importance sampling is an alternative that can reduce the computational load on computers. This powerful tool is utilized to investige the performance of communication systems in fading channels. Differentially encoded quadrature phase-shift keying (DEQPSK) carrier is used in the systems. We have shown that differential decoding is 2 dB better than differential detection when perfect phase recovery is attained. However, differential decoding suffers a large performance loss when the phase estimate is not perfect. The degradation comes from the nonzero variance of the phase estimator and two anomalies which are also caused by the imperfect phase recovery, namely phase equivocation and misalignment for the combining. An equivocation free receiver and aligning procedure are employed to conquer the anomalies.
Degree
Ph.D.
Advisors
Sadowsky, Purdue University.
Subject Area
Electrical engineering
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