| Multiple input multiple output (MIMO) communication systems and multiuser diversity play important rolls in future wireless systems and enable them to achieve high data rates. Earlier studies on multi-user MIMO (MU-MIMO) systems were based on some ideal assumptions on system such as perfect channel state knowledge, perfect feedback channel and known inter-cell interference. This thesis investigates design and performance of MU-MIMO systems under more practical assumptions.;We first consider channel state information (CSI) feedback schemes for MIMO-OFDM broadcast channel. By considering simple zero-forcing beamforming (ZFBF) precoder and ignoring user selection problem, we compare achievable ergodic rates under different channel state feedback schemes. We propose a novel "time-domain" channel quantized feedback which is inspired by rate-distortion theory of Gaussian correlated sources and takes advantage of the channel frequency correlation structure.;Next, we consider spacial channel model (SCM) which is used as a benchmark in standardization and examine some alternatives for channel estimation and prediction scheme. We show that a parametric method based on ESPRIT is able to accurately predict the channel even for relatively high user mobility as long as the angular spread is large.;Subsequently, we study the problem of user scheduling in MIMO broadcast systems under non-perfect CSI. We propose a dynamic novel opportunistic scheme that, depending on the channel state quality of user terminals, categorizes user terminals into "predictable" and "non-predictable" users and at each scheduling slot, serves one non-predictable user (transmit diversity) or several predictable users (multi-user diversity).;In our final analysis, we investigate user scheduling in the presence of unknown inter-cell interference. We present a systematic method for joint scheduler/ARQ design. We define "optimistic" throughput as the throughput that can be achieved if the transmitter knew the instantaneous user ICI and transmitted to each scheduled user at the maximum possible instantaneous rate and show that properly designed incremental-redundancy hybrid ARQ schemes can achieve any desired fraction of the "optimistic" throughputs with finite average decoding delay where optimistic.;Results in this work have been published in the following papers: (1) H. Shirani-Mehr, H. Papadopoulos, S. A. Ramprashad and G. Caire, "Joint Scheduling and Hybrid-ARQ for MU-MIMO Downlink in the Presence of Inter-Cell Interference", submitted to IEEE Transactions on Communications. (2) H. Shirani-Mehr, G. Caire and M. J. Neely, "MIMO Downlink Scheduling with Non-Perfect Channel State Knowledge", submitted to IEEE Transactions on Communications. (3) H. Shirani-Mehr, H. Papadopoulos, S. A. Ramprashad and G. Caire, "Joint Scheduling and Hybrid-ARQ for MU-MIMO Downlink in the Presence of Inter-Cell Interference", Submitted to ICC 2010. (4) H. Shirani-Mehr and G. Caire, "Channel State Feedback Schemes for Multiuser MIMO OFDM Downlink", IEEE Transactions on Communications, September 2009. (5) H. Shirani-Mehr, and G. Caire, "MIMO Downlink Scheduling with Non-perfect Channel State Knowledge", Information Theory Workshop, 2009, Taormina, Italy. (6) H. Shirani-Mehr, D. N. Liu and G. Caire, "Parametric Channel Estimation and Prediction with Applications to Channel State Feedback for MIMO Downlink Schemes", 42nd Asilomar Conference on Signals, Systems and Computers, 2008. (7) G. Caire and H. Shirani-Mehr, "Feedback Schemes for Multiuser MIMO-OFDM Downlink", Information Theory and Applications Workshop, 2008. |
