QoS-Guaranteed Sequential User Selection in Multiuser MIMO Downlink Channels

In recent years, multiuser applications of MIMO techniques have received a lot of attention because of their large capacity gains for next generation multiuser wireless systems. In this paper, we propose a new sequential user selection algorithm and analyze its performance in multiuser QoS-guaranteed MIMO downlink channels. Multiple QoS-guaranteed users can be supported simultaneously while non-QoS users can receive the available residual throughput without sacrificing QoS-guarantees by flexibly allocating spatial gains to different QoS classes. The proposed algorithm can also reduce computational complexities of user selection procedures by dividing the whole user group into several subgroups according to their QoS priorities. We assume throughput-constrained constant rate users, delay-constrained real time users and no-constraint best effort users for different QoS classes. Numerical results demonstrate that our model can provide QoS-guaranteed services for constant rate users and real time users simultaneously, at the cost of some reduction in the total throughput for the MIMO downlink channels.