WLC39-6: Sum Rate Maximization and Transmit Power Minimization for Multi-User Orthogonal Space Division Multiplexing

We demonstrate that receive antenna selection (RAS) provides significant increase in the achievable sum rates for multi-user MIMO wireless downlinks that employ block diagonalization (BD) to achieve orthogonal space division multiplexing (OSDM), where each user terminal has one or more antennas. Although dropping one or more receive antennas at a user terminal reduces its capacity and correspondingly, the system sum capacity, judicious RAS improves the projected channel spatial mode gains and provides additional degrees of freedom to all other terminals within the BD-OSDM context. In this way there is mutual benefit to be shared among users when RAS is applied to all users and numerical results show significant sum rate gains despite sum capacity loss due to RAS. In many cases, users with reduced array sizes also enjoy increased channel rates. When projected virtual channels are used as a means of spatial mode allocation, this RAS concept is also beneficial and may be referred to as spatial mode selection (SMS). RAS/SMS is therefore a necessary first step in any resource allocation and power control exercise for BD-OSDM. Further, the same RAS/SMS algorithms for sum rate maximization also provide a systematic means of resource allocation and power control. To avoid exhaustive RAS search, which has exponential complexity, efficient RAS algorithms with linear complexity and near optimal performance are proposed.