The impact of multiuser diversity on space-time block coding

In this letter, analytic performance results are derived for space-time block coding paired with multiuser diversity. We consider a scenario in which K active data users, each of which is potentially equipped with multiple antenna elements, are served by a multi-antenna element base station (BS). We focus on the downlink channel, where a space-time block coding scheme is employed and assume that channel quality information is reported to the BS by all users on a per frame basis. Using a scoring function at the BS, time resources are allocated to the user with the best instantaneous effective signal-to-noise ratio (SNR), facilitating a multiuser diversity mechanism. Using order statistics, we compute histograms and cumulative distribution functions of the effective SNR at the space-time combiner output and assess the interaction between multiuser diversity obtained via scheduling and spatial diversity obtained via the space-time code.