Signal design for multiple-input multiple-output wireless: A unified perspective

Wireless networks are unique among communication networks by virtue of the mobility and portability they enable for the end-user. Wireless networks are impaired by several propagation phenomena such as fading, delay spread and co-channel interference. A new paradigm that mitigates these adverse effects by employing multiple antennas at both the transmitter and the receiver is rapidly emerging as an acceptable practical solution. In theory, such multiple-input multiple-output (MIMO) systems provide enormous gains in spectral efficiency that are linear in the number of antennas. Efficient signal design to realize these gains is an important practical problem. Signal design for the case when the channel is known at the receiver and unknown at the transmitter has been heavily studied. The solutions span a wide range from designs that maximize signal reliability to designs that maximize information rate. Each of these designs is well understood in isolation, but to date there has been no cohesive analysis of general space-time codes that ties all these designs together.; In this dissertation we provide a unifying framework for the design and analysis of space-time codes that are linear in the input information symbols. Previous work on designing space-time codes minimized the maximum pairwise error probability (PEP), i.e., the probability of error between the closest pair of codewords. We take into account the entire constellation by employing the conventional union bound on probability of error. The union bound is in fact a tighter upper bound on the probability of error than the maximum PEP. Focusing on the quasi-static Rayleigh MIMO channel, we derive necessary and sufficient conditions on linear codes that minimize the union bound. Our solutions encompass as special cases the well-known spatial multiplexing (SM) and orthogonal space-time block codes (STBCs).; Spatial multiplexing is known to be capacity-efficient, i.e., SM can achieve channel capacity in conjunction with good temporal codes. Orthogonal STBCs lose capacity over channels with multiple receive antennas. We provide sufficient conditions for capacity-efficient codes and design new linear codes based on both error probability and capacity that outperform previously proposed codes.