Enhanced DS-CDMA uplink performance through base station polarization diversity and multistage interference cancellation

In wireless communications systems, multipath fading and multiple access interference distort the received signal and cause significant degradation in system performance. By exploiting the intrinsic structure of multiple access interference, multiuser detection significantly improves performance and overcomes the near-far problem of the conventional DS-CDMA correlation receiver. In mobile environments, polarization rotation and decorrelation arise due to multiple reflections and scattering along the transmission path. Furthermore, in portable applications since hand-held terminals are often oriented inclined to the vertical, the energy radiated from the handset has components in both vertical and horizontal directions. Polarization diversity is thus a very practical alternative for providing diversity reception at the base station and mitigating the deleterious effects of multipath fading. This paper evaluates the uplink performance of a DS-CDMA system that incorporates multistage parallel interference cancellation, and takes advantage of polarization diversity at the base station. Results indicate that polarization diversity leads to performance improvement comparable to spatial diversity.