Optimal antenna assignment considering QoS under MIMO environments

Exploiting multiple-input-multiple-output (MIMO) diversity, systems with error-prone and bandwidth-limited wireless channels can easily support reliable transmission. We develop optimal cross-layer scheduling that consists of QoS scheduling at the upper layer and optimal antenna selection at the physical layer. For QoS scheduling, we design a framework for optimal scheduling to meet users´ QoS requirements. To solve this optimization problem, we consider a clique-searching algorithm for antenna selection that maximally utilizes the characteristics of MIMO systems by adopting the graph theoretical approach. As the clique searching problem becomes NP complete with the increase of transmit antennas in number, we propose a suboptimal antenna selection algorithm to deal with a large number of transmit antennas. We derive some theorems and properties for our approach and, through simulations, we demonstrate the performance of QoS scheduling which is effective to handle real-time traffic.