Efficient transmit strategies for multiuser multiple antenna systems.

摘要

The use of space diversity techniques has become a prominent candidate to combat the impairments of the wireless channel. It has been shown that space diversity can be obtained via either employing co-located multiple transmit or receive antennas, or using simple relay nodes to assist the transmission. The premise of this thesis is that the performance of a multiuser system is highly dependent on the transmission scheme of each user. Consequently, we investigate the transceiver design problem for multiuser systems using either multiple antennas or relay nodes. In the first part of the thesis, we focus on multiuser multiple antenna systems. We classify the multiuser systems by their multiaccess strategies and consider the transceiver design problems that arise due to the multiaccess structures in each context. Specifically, we consider narrowband multiuser multiple input multiple output (MIMO) systems that employ multiple transmit and/or receive antennas, time-slotted multiuser MIMO systems and multiple antenna CDMA systems. We propose efficient transceiver design algorithms for each system considering the system wide mean squared error (MSE) or the sum capacity of the users as the performance metrics. Next, we investigate the effect of channel estimation errors on the transceiver designs we proposed. In order to characterize the effect of channel estimation errors on multiuser systems, we first analyze single user MIMO systems, and then extend our results to the multiuser case. Lastly, we turn our attention to the relay assisted multiuser communications, relay assisted F/TDMA ad hoc networks, and study the power allocation problem at the relay nodes. Considering the sum capacity as the performance metric, we solve the problem of optimally allocating the total power of each relay node between the transmissions it is assisting.