Robust exploitation of spatial and multi-user diversity in limited-feedback systems

We explore spatial vs. multi-user diversity tradeoffs in a cellular system with limited feedback. When the average feedback per individual user must be kept low, we show that spatial diversity gains, provided by antenna selection mechanisms and space-time block coding, clearly exceed those of multi-user diversity. Performance assessment is conducted, both analytically and by means of computer simulations, in terms of average system capacity and throughput. Closed-form expressions are derived for the SNR densities associated with the different transmission configurations, along with an approximate lower bound for system throughput.