Multiuser detection of short-code CDMA with antenna diversity

Many current and proposed wireless protocols that employ a code division multiple access (CDMA) element, incorporate short spreading sequences in order to facilitate efficient multiuser detection architectures. One such standard is the time division duplex (TDD) mode of the 3rd Generation Partnership Project (3GPP) universal terrestrial radio access (UTRA) system. One potential drawback with using short spreading codes is that as the number of users approaches the spreading code length the near-far resistance and the numerical stability of linear multiuser detection algorithms degrades. One method to mitigate these effects, and hence operate the system with a higher load, is to employ diversity antennas at the receiver. In this paper we study the mean asymptotic multiuser efficiency and analyse the numerical stability of linear multiuser detection algorithms employing receiver diversity.