Analysis of diversity, beamforming and hybrid diversity-beamforming systems

In this paper we compare Shannon capacities of diversity, beamforming, and hybrid diversity-beamforming systems for reverse and forward links. Our results show that the reverse link capacity of a diversity system is higher than that of a beamforming system, while the beamforming system can provide higher capacity than the diversity system in the forward link. A hybrid diversity-beamforming system can provide comparable capacity to the diversity system in the reverse fink and to the beamforming system in the forward link. We also compare outage capacities of these three systems and our results show that the diversity system provides higher outage capacity both in reverse and forward links. Estimation of forward link channel covariance matrix is of vital importance for sub-optimum design of forward link beamformer and is addressed in the last section of the paper. We propose two methods for estimating the forward link channel covariance matrix based on reverse link measurements for a frequency-division-duplex (FDD) system.