Cochannel interference reduction and path-diversity reception technique using CMA adaptive array antenna in digital land mobile communications

This paper describes a cochannel interference (CCI) reduction and path-diversity reception technique using a constant modulus algorithm (CMA) adaptive array antenna in digital land mobile communications. In this technique, the incident signals are individually recovered by using a multistage constant modulus (CM) array that consists of a multistage cascade of signal recovering and canceling processes. The recovered signals are sorted into the desired signal and CCI signal, and then the desired signals are combined in order to obtain the path-diversity gain, Performance is evaluated for a Gaussian filtered minimum shift keying signal and π/4-shifted quadrature phase-shift keying signal. Each signal processing is carried out using block demodulation (e.g., CMA adaptive signal recovering process and signal canceling process). Computer simulation results show that CCI can be reduced efficiently for a high-bit-rate time-division multiple-access system for quasi-static and fading channel conditions and that the bit error rate (BER) performance is improved by combining the desired signals. The extent of the improvement in BER performance indicates the difference in diversity gain between maximal ratio combining and selective combining. This suggests that a CMA adaptive array antenna is equivalent to selective combining diversity reception