Precoder design for MIMO wireless communications systems

This thesis mainly addresses the designs of precoders for the multiple-input-multiple-output (MIMO) wireless communication systems. A joint transceiver design subject to a total power constraint is first introduced. The sum of the mean square error (MSE) of all data streams (the trace of the MSE matrix) is used as the objective to minimize. A detailed derivation with an analytic solution is provided.;A joint transceiver design subject to per-antenna power constraints, which is more realistic since each antenna has its own power amplifier, is considered. Two iteration methods are provided since the equation is highly nonlinear when the optimal precoder F is solved.;The precoder designs for several practical systems are investigated. In a time-division duplex (TDD) system where the MIMO channels between the downlink and the uplink are reciprocal, the channel state information can be obtained by sending the training sequence. The MMSE precoder is designed based on the estimated channel state information (CSI).;In a frequency-division duplex (FDD) system, where the MIMO channels are not reciprocal, the estimated CSI needs to be sent back through a feedback link, which is bandwidth-limited. A codebook-based feedback approach will be adopted. Both the transmitter and the receiver store the same codebook. At the receiver, the codeword is picked up according to some selection criterion, and the corresponding index of this codeword is sent back to the transmitter. The transmitter will choose this codeword for the data precoding. A new feedback strategy is proposed as well.;The precoder design for an FDD MIMO system with a successive interference cancellation (SIC) scheme at the receiver is investigated. SIC scheme, which is nonlinear, can improve the system performance since with the assistance of cyclic redundancy check (CRC), interferences from the correctly detected bit stream to the incorrectly detected bit stream due to MIMO transmission/reception can be removed. A codebook-based feedback approach will be adopted for the precoder design because of the limited bandwidth in the feedback link. Two selection criteria of the CSI codeword for precoding, the conventional singular value decomposition (SVD) and the partial channel precoding, are proposed.;At last, the precoder design for a downlink multiuser FDD MIMO system is investigated. Block diagonalization (BD), which is a linear processing technique, aims to eliminate the multiuser interference in multiuser downlink broadcast systems. The key idea is to design each user's precoding matrix to lie in the null space of all other users' channels. For the FDD systems, a feedback method called "range space feedback" is developed. Each user will send back the range space of its own channel. The performance due to quantization error will be investigated through the numerical simulations.