EFFECT OF RANDOM CARRIER PHASE AND TIMING ERRORS ON THE DETECTION OF NARROW-BAND M-PSK AND BAND-LIMITED DS/SS M-PSK SIGNALS

In this contribution we present a simple approximate expression for the BER degradation, caused by random carrier phase and timing errors, of the maximum-likelihood (ML) receivers operating on narrowband M-PSK and bandlimited direct-sequence/spread-spectrum (DS/SS) M-PSK signals; this expression is very accurate for (small) degradations of practical interest, and reveals that the BER degradation (in dB) is essentially proportional with the tracking error variance. In the absence of ISI at the optimum decision instants, carrier phase errors yield exactly the same degradation for narrowband M-PSK as for bandlimited DS/SS M-PSK. When the product of the r.m.s timing error and the minimum signal bandwidth is held constant, the degradation for bandlimited DS/SS M-PSK is considerably smaller than for narrowband M-PSK, especially for large values of M and small values of the rolloff.