Diversity reception in short-code CDMA

Short spreading sequences facilitate efficient multiuser detectors and have hence been incorporated into practical code division multiple access systems such as 3rd Generation Partnership Project UTRA-TDD. However, as the number of users approaches the spreading code length, the asymptotic performance and the numerical stability of linear multiuser detection algorithms degrade. Given some simplifications such as synchronous users, it is shown that receive diversity effectively mitigates these degradations and allows the system to be operated with a high load. A lower bound on the mean asymptotic multiuser efficiency is presented and the numerical stability of linear multiuser detection algorithms for systems with receive diversity is analysed. It is further shown that the performance variability is significantly reduced by receive diversity.