1Introduction
Abstract
The main goal of modern wireless communications is reliable transmission over an imperfect channel with the data rate to approach the channel capacity as much as possible. A physical channel often introduces additive white Gaussian noise, interference of various natures, and probably also multipath fading. The latter two impairments are often the sources that eventually limit the performance of a wireless system. Efforts of combating interference and multipath fading constitute an important part of the history of communications. The mathematical nature of interference is the collision between multiple symbols or multiple users in a low-dimensional space. Today, the paradigm of orthogonality has become a basic thought for combating different types of interference, while multi-antenna technology is a powerful means to exploit the inherent capacity of multipath fading channels.
James Clerk Maxwell's electromagnetic theory, established in 1864, uncovered the field nature of electromagnetic waves, marking a transition in our understanding of electromagnetism from phenomenology to physical theory. It is a prelude to the two far-reaching and revolutionary events in contemporary sciences: quantum physics and Einstein's theory of relativity. In engineering aspect, Maxwell's electromagnetic theory essentially becomes a physical foundation for telecommunications, stimulating the invention of the radio by Guglielmo Marconi in 1901, the invention of television broadcasting ...