Adaptive Antennas for Microcellular and Mixed Cell Environments withDS-CDMA

Abstract

Adaptive antenna technology is now regarded as one of the key system components in future generation cellular networks. This paper considers the performance of a DS-CDMA system which employs adaptive antennas at the base station sites of both microcell and mixed micro/umbrella cell operational environments. A microcellular ray tracing propagation tool has been employed in order to ascertain site specific propagation data. Results for a typical small cell environment highlight both the propagation characteristics and the behaviour of the adaptive antenna, as well as the sensitivity of the system upon parameters such as the mutual coupling effect. This work does not assume idealised propagation conditions or antenna radiation patterns for the small cell analysis. In summary, the results indicate that microcellular base stations employing adaptive antenna signal processing can offer a significant capacity enhancement and improved channel characteristics when compared with their omnidirectional counterparts. In addition, it is shown that umbrella cells overlaying microcells within the same RF bandwidth allocation, do not impact upon system capacity providing that adaptive antenna technology is employed at the umbrella cell site.