A comparison of multipath distortion characteristics among digital modulation techniques

In a digital mobile radio transmission, long-delayed multi-path propagation causes frequency selective fading, resulting in signal waveform distortion and hence bit error rate (BER) degradation. Comparison of multipath distortion among various digital modulation techniques (binary, quaternary, offset quaternary, and minimum phase shift keying (BPSK, QPSK, OQPSK and MSK)) is made using a two-ray propagation model, which is a fundamental model to evaluate multipath tolerant capability. The analysis clarified the multipath conditions causing severe distortions and also the mechanisms of eye pattern degradation, showing the superiority of BPSK in multipath tolerance.