Software antenna and its communiation theory for mobile radio communications

An adaptive array antenna or a kind of smart antenna is named a software antenna because it can be programable to form a desired beam pattern if an appropriate set of antenna weights is provided in software. It can be a typical tool for realizing a software radio. An adaptive array can be considered as an adaptive filter in space and time domains for radio communications, so that the communication theory can be generalized from a conventional time domain into both space and time domains. This paper introduces a spatial and temporal communication theory based on a software antenna, such as spatial and temporal channel modeling, equalization, optimum detection for a single user and multiuser in CDMA, preceding and joint optimization of both transmitter and receiver. Such spatial and temporal processing promises drastic improvement of performance as a practical countermeasure for multipath fading in mobile radio communications.