Spatial scheduling algorithms for wireless systems

This paper addresses the problem of the spatial scheduling of users in a cell for simultaneous downlink transmission from a base statimultiple antennas on (BS) having multiple antennas under a perspective of joint Physical and Medium Access Control (PHY-MAC) design. First of all, we compute the transmit beamvectors for each group according to a zero forcing (ZF) criterion, which gives a simple closed-form solution. We show first that it is equivalent to the minimization of the maximum bit error rate (BER). In this paper, the main contribution lies on the resolution of the NP-complete combinatorial problem that comes up as a cost function if we want to minimize the total transmit power. The solution of the NP-complete problem is performed by the stochastic technique simulated annealing (SA). Additionally, we present two heuristic algorithms that may enable a real-time implementation of this scheduling approach.