Opportunistic Multiuser Scheduling in Downlink TDMA MISO Systems

Abstract

We consider the problem of multiuser opportunistic fair scheduling (OFS) in downlink MISO systems employing beamforming. OFS is performed on a per scheduling interval basis to achieve fair bandwidth allocation. Transmit beamforming provides TDMA systems with the capability of supporting multiple concurrent transmissions. Since the optimal beamforming scheme can be calculated for a given subset of users, the scheduling problem then refers to the optimal user subset selection to maximize the system throughput subject to certain constraints. We propose two practical multiuser schedulers, and then present discrete stochastic approximation algorithms to select adaptively a better user subset. We also consider scenarios of time-varying channels where the algorithm can track the time-varying optimum. We present results to show the performance of the proposed algorithms in terms of fast convergence, time-varying tracking capability and fairness.