Performance of Multicode DS/CDMA With Noncoherent $M$ -ary Orthogonal Modulation in the Presence of Timing Errors

This paper derives an accurate approximation to the bit error rate (BER) of multicode direct-sequence code-division multiple access (DS/CDMA) with noncoherent M-ary modulation in wideband fading channels when timing errors are made at the receiver employing equal-gain combining (EGC). This reflects the practical scenario where the path delays are estimated imperfectly, leading to synchronization errors between the correlation receivers and the received signals. The analysis can be applied to any type of a fading distribution for both independent and correlated diversity branches. It is shown that the derived analytical expressions are in close agreement with the Monte Carlo system simulations, particularly in the case of small timing errors.