Special issue on signal processing for wireless communications

Increasingly, wireless communication networks, and particularly mobile networks, are designed to operate as multiuser systems, in which the sharing of temporal, spatial, and spectral resources by multiple users is systematic. Such systems permit significant flexibility in channel assignment, allow effective countermeasures to the physical properties of multipath channels, and generally provide for efficient utilization of the resources of mobile radio and similar channels. Examples of such systems include code-division multiple-access (CDMA) systems in which resource sharing begins at the transmitter, as well as orthogonally-multiplexed systems such as time-division multiple-access (TDMA) systems, in which resource sharing results from physical limitations such as multipath and imperfect channelization filters. Indeed, these types of systems include most contemporary and emerging standards for digital wireless communications. In order to fully exploit the favorable properties of multiuser communications, it is necessary that the multiuser nature of the signaling multiplex be accounted for in receiver design. This necessity has been recognized since at least the early 1980's. notably with the organized study of advanced signal processing techniques for the demultiplexing of non-orthogonally multiplexed signals — i.e. mutliuser detection. The interest in such techniques has grown considerably over the intervening two decades, with the coincident exploding growth in commercial wireless services and the attendant demands on available power and spectrum resources. A great variety of techniques have been developed in this area, and the purpose of this special issue is to present some of the latest of these techniques.