Multiple Antenna Wireless Systems and Channel State Information

OF THE DISSERTATION Multiple Antenna Wireless Systems and Channel State Information by Dragan Samardzija Dissertation Director: Professor Narayan B. Mandayam The use of multiple antennas in wireless systems have been shown to provide tremendous capacity gains. A key factor in realizing such gains is the knowledge of the channel state information (CSI) at the receiver and transceiver. In this thesis we study the fundamental limits of multiple antenna multiuser systems in the following contexts: (1) pilot-assisted channel state estimation, (2) transmitter optimization with delayed CSI and (3) CSI feedback schemes. We first analyze the effects of pilot assisted MIMO channel estimation on achievable data rates (lower bound on information capacity) over a frequency flat time-varying channel. Under a block-fading channel model, the effects of the estimation error are evaluated in the case of the estimates being available at the receiver only (open loop), and in the case when the estimates are fed back to the transmitter allowing water pouring transmitter optimization (closed loop). Using a characterization of the effective noise due to estimation error, we analyze the achievable rates as a function of the power allocated to the pilot, the channel coherence time, the background noise level as well as the number of transmit and receive antennas. We observe that as the number of transmit antennas increases, the sensitivity to the channel response estimation error is more pronounced (while keeping the same number of receive antennas). It is also seen that in certain cases, it is better to use the open loop scheme as opposed to the closed loop scheme. The analysis presented here can be used to optimally allocate pilot power for various system and channel operating conditions, and also to determine the effectiveness of closed loop feedback. Next, we consider multiple antenna transmitter optimization schemes that are based on