| The use of multiple antennas at both ends of a point-to-point wireless link, known as multiple-input multiple-output (MIMO) wireless, promises significant performance enhancements in terms of capacity, reliability and power efficiency. In the first part of the thesis, we quantify the resulting gains over point-to-point MIMO links by characterizing the statistical properties of mutual information over frequency-selective correlated Gaussian MIMO channels assuming that the channel is unknown at the transmitter and perfectly known at the receiver.; With ever increasing demands for ubiquitous, tetherless and high data rate applications, there has recently been great interest in developing distributed (or adhoc) communication techniques for enhancing performance and enabling more efficient usage of system resources over wireless networks. In particular, how to utilize the spatial degrees of freedom created by multiple antennas in the adhoc network setting has long been an open problem. In the second part of the thesis, we design and analyze distributed MIMO relaying techniques as an additional leverage over conventional point-to-point MIMO systems and quantify the resulting gains in terms of power/bandwidth efficiency and link reliability. We use Shannon-theoretic tools to analyze the tradeoff between energy efficiency and spectral efficiency (known as the power-bandwidth tradeoff) in meaningful asymptotic regimes of signal-to-noise ratio (SNR) and network size. We propose low-complexity distributed coordination schemes based on linear relay forwarding and characterize their power-bandwidth tradeoff under a system-wide power constraint on source and relay transmissions. The impact of multiple users, multiple relays and multiple antennas on the key performance measures of the high and low SNR regimes is investigated in order to shed new light on the possible reduction in power and bandwidth requirements through the usage of distributed relaying techniques. |
