In this paper, we investigate the performance of maximum ratio combining (MRC) in the presence of multiple cochannel interferences over a flat Rayleigh fading channel. Closed-form expressions of signal-to-interference-plus-noise ratio (SINR), outage probability, and average symbol error rate (SER) of quadrature amplitude modulation (QAM) with M-ary signaling are obtained for unequal-power interference-to-noise ratio (INR). We also provide an upper-bound for the average SER using moment generating function (MGF) of the SINR. Moreover, we quantify the array gain loss between pure MRC (MRC system in the absence of CCI) and MRC system in the presence of CCI. Finally, we verify our analytical results by numerical simulations.

This paper presents the approximate error rates of M-ary phase shift keying (MPSK) for optimum combining (OC) with multiple interferers in a flat Rayleigh fading channel. The approximations, which have been used to evaluate the performance of binary PSK for OC, are extended to the performance analysis of MPSK for OC in the presence of arbitrary numbers of antennas and interferers. The mean eigenvalues of interference-plus-noise covariance matrix are analyzed to compare the approximation techniques, i.e., first-order approximation and the orthongal approximation. Using the moment generating function (MGF)-based method, the approximate error rates of MPSK for OC are derived as the closed-form expressions in terms of the exact error rates of MPSK for MRC. The approximate analytical results show the simple and accurate way to assess the average symbol error rate of MPSK for OC with arbitrary numbers of antennas and interferers.

For usage in fading environments, the idea of utilizing radio signal processing with software programmable devices promises greater flexibility and functionality. However, to realize these benefits very high performance DPSs and AD converters are required, especially for adaptive antennas with CDMA. One potential method of reducing the implementation complexity is to employ multicarrier (MC) modulation as it allows parallel signal processing in addition to its benefits in combating fading and ISI effects. This paper proposes a system utilizing MC DS/CDMA and a recursive adaptive array antenna processing algorithm for estimating the array response vector (array manifold) and hence the optimal weights. In order to evaluate this system performance results obtained through computer simulations are presented. The proposed MC system improves the accuracy of the direction-of-arrival (DOA) estimation of the signal by 2 degrees as compared with a single carrier system. It is also shown that the proposed adaptive array antenna algorithm for MC DS/CDMA reduces the number of iterations of the power method significantly and allows parallel processing of the adaptive algorithm.