Software antenna and its communication theory for mobile radio communications

An adaptive array antenna or a smart antenna is named a software antenna because it can be programmable 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 the space and time domains for radio communications, so that the communication theory can be generalized from a conventional time domain into both the 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 multiple users in CDMA, precoding and joint optimization of both the transmitter and receiver. Such spatial and temporal processing promises drastic improvement of performance as a practical countermeasure for multipath fading in mobile radio communications.