Dynamic Resource Allocation for Downlink Multiuser MIMO-OFDMA/SDMA Systems

Abstract

In this paper, new dynamic resource allocation algorithms are investigated for the downlink of multiuser multiple-input multiple-output orthogonal frequency-division multiple-access and space-division multiple-access (MU-MIMO-OFDMA/SDMA) systems. Firstly, a mathematical formulation of the optimization problem is presented with the objective of maximizing the total system throughput under the constraints of each user’s quality of service (QoS) requirement and the integer modulation orders available on each spatial subchannel. Secondly, since it is difficult to obtain the optimal solution to the joint optimization problem, the whole optimization procedure is divided into two steps, namely, the subcarrier-user scheduling and the resource allocation. In the first step, a new metric is proposed to measure the spatial compatibility of multiple users, each with multiple receive antennas, based on which a new scheduling algorithm is designed to identify the optimal sets of selected users over all subcarriers. In the second step, two dynamic resource allocation algorithms are developed to assign radio resources to the scheduled users subcarrier by subcarrier. Simulation results demonstrate that the proposed algorithms outperform the traditional allocation methods based on random scheduling scheme. Especially, the performance of the algorithm, combined with power reuse strategy, approaches closely to that of the optimal allocation method based on user selection.