Multiuser interference suppression in wideband broadcast CDMA networks

Multipoint-to-point code division multiaccess (CDMA) networks have been the primary focus in multiuser interference (MUI) suppression research, where the recent development of the turbo minimum mean square error (MMSE) detector promises near interference-free performance at an acceptable complexity. The complementary case, namely point-to-multipoint, i.e. broadcast transmission is increasingly becoming more important since traffic on the forward link is likely to increase substantially, particularly for data, in the near future. In (synchronous) broadcast with orthogonal spreading, e.g. the forward link in a single-cell configuration such as a wireless local area network (WLAN), MUI arises only due to the frequency selectivity of the propagation medium. MMSE and turbo MMSE equalisation based receivers are developed. They are observed to significantly mitigate MUI in a WLAN´s forward link, especially with the turbo configuration comprising a linear MMSE front-end equaliser in early iterations and a decision feedback MMSE front-end equaliser in later iterations. The relevance of such approaches to the multicell CDMA forward link is also discussed in relation to recent trends that tie pricing to the quality of service provided to the user.