On the Performance, Complexity, and Fairness of Suboptimal Resource Allocation for Multiuser MIMO-OFDMA Systems

The combination of multiple-input-multiple-output (MIMO) and orthogonal frequency-division multiple access (OFDMA) is a promising solution to the flexible and spectrally efficient provision of data services in future wireless communication systems. However, adaptive resource allocation (RA) in frequency, time, and space in multiuser MIMO-OFDMA systems is very complex due to the inclusion of the space dimension and the large number of resources to be managed. Indeed, an optimal RA for maximizing the sum rate is usually too complex for practical application, and suboptimal strategies are required. In this paper, the performance, complexity, and fairness of suboptimal RA strategies aiming at the maximization of the sum rate are investigated. A model for suboptimal RA strategies is proposed, and two new RA strategies are introduced. The proposed strategies are compared in terms of the sum rate, complexity, and throughput fairness and are shown to present better performance-complexity and performance-fairness tradeoffs than some existing suboptimal strategies, as well as to achieve almost the same sum rate as that obtained through an exhaustive search.