A wireless multiuser system using diversity

This paper quantifies how diversity and the number of users affect the performance of a wireless multiuser system. The system accommodates N users and one central base station. Only the reverse link is considered. The base station receives the signal at A different antennas. In addition to antenna diversity, bandwidth diversity is used by transmitting signals with larger than Nyquist bandwidth. The receiver consists of an optimum linear MMSE equalizer/combiner. The stationary, frequency selective radio channels between all users and the base station are assumed to be known at the receiver. MMSE expressions are given and numerically evaluated. A tight lower bound is derived for the case when the number of users is larger than the total degree of diversity, referred to as overpopulated. Otherwise, the system is well populated. It is shown that overpopulated systems are interference limited while well populated systems are noise limited