Abstract:
In the last decade, the increasing demand for wireless communication services has created the need for systems that offer high capacity and quality of service. In order to accommodate more customers in a given coverage area, we face the challenge of improving the system capacity without degradation in the quality of service. Besides voice communication, video telephony, remote database query, transaction processing and electronic data interchange could also be implemented in advanced cellular systems. Frequency reuse techniques attempt to utilise the available frequency spectrum in an efficient manner. In order to increase this frequency reuse factor, the cell size could be reduced. This reuse causes cochannel interference (CCI), which is one of the major sources of performance degradation.
One of the techniques for interference reduction is diversity combining. There are a range of diversity techniques available in conjunction with adaptive antenna arrays. With optimum combining, the signals at the receiving antennas are weighted and combined to maximise the output signal to interference plus noise ratio (SINR). Therefore, interfering signals are suppressed while the desired signal is enhanced. One of the diversity techniques, called minimum mean square error (MMSE) diversity combining, has been adopted for cellular mobile radio systems because it is specifically designed to suppress CCI.
