An evaluation of adaptive antennas for UMTS FDD by system simulations

A system simulator for performance evaluation of adaptive antennas in UMTS FDD has been developed. The simulator is flexible, it uses realistic channel and system assumptions, and, for a given scenario, provides the maximum number of users that can be supported by the network. The antenna types included in the simulator are switched lobe, phased array and adaptive array, as well as conventional fixed sector antennas. Results point to a capacity increase of more than a factor of two by using adaptive antennas compared to conventional sector antennas. Most of the increase is obtained by using the relatively simple switched lobe antenna implementation. Using adaptive antennas can alternatively increase range or reduce transmit power. The reduction in transmit power points to MS battery lifetime being increased by at least 4 times compared to conventional sector antennas. Sector and switched lobe antennas are approximately equally sensitive to downlink orthogonality loss. The total network capacity was roughly 20 % higher when increasing the downlink code orthogonality from 0.4 to 0.8.