This paper quantifies the effect of diversity and number of users on the performance of a wireless multiuser system. The reverse link is considered for a system with N users and a single base station. The base station receives the signal at A different antennas. In addition to antenna diversity, frequency diversity is used by transmitting signals with larger than Nyquist bandwidth. The receiver consists of a multiple-input multiple-output (MIMO) MMSE linear (LE) or decision-feedback equalizer (DFE). The quasi-stationary, frequency selective radio channels between all users and the base station are assumed to be known at the receiver. We unify the concepts of frequency and antenna diversity and show that the total degree of diversity is equal to the product of processing gain and receiver inputs. It is proven that the general relationship between the equalizer output SNR and MMSE for the MIMO LE and DFE is the same as for the single-input single-output equalizers. Bit error rates, outage probabilities and capacities of systems with different degrees of diversity, user populations and signal to noise ratios are calculated and illustrated.
Multiuser detection, MIMO equalization, spread spectrum, antenna diversity, diversity combining, decision-feedback equalizers, wireless communication.PDF file, 336 kBytes