| 摘要 |
A joint scheduling and grouping technique for throughput maximization is disclosed for an uplink space-division multiple access (SDMA) system under proportional fairness constraints, when the receiver employs successive group decoding. We consider a slow-fading narrowband MIMO multiple access channel (MAC) in which multiple users, each equipped with multiple transmit antennas, communicate to a receiver equipped with multiple receive antennas. The users are unaware of the channel state information (CSI) whereas the receiver has perfect CSI and employs a successive group decoder (SGD). For an open-loop system, achievable outage probabilities are obtained for the case where an outage must be declared simultaneously for all users (common outage) as well as the case where outages can be declared individually for each user (individual outage). We then derive the optimum successive group decoder (OSGD) that simultaneously minimizes the common outage probability and the individual outage probability of each user, over all SGDs of permissible decoding complexity. For each channel realization, the OSGD is also shown to maximize the error exponent of the decodable set of users. An adaptive SGD is derived which not only retains the outage optimality of the OSGD but also minimizes the expected decoding complexity. Asymptotically tight (in the limit of high SNR) affine approximations are then obtained for the weighted sum common and individual outage capacities and the symmetric outage capacities. Limiting expressions for the relevant capacities as the number of users and the number of receive antennas approach infinity are also obtained and it is shown that the SGD yields symmetric capacity gains commensurate with the decoding complexity allowed. Simulation results with practical LDPC outer codes show that the OSGD offers significantly improved performance at low decoding complexity.
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