Recent results concerning the benefit of joint detection in CDMA systems

CDMA is a potential multiple access method for third generation cellular mobile radio systems. If accurate power control and soft handover have to be avoided, adequate CDMA system capacity can only be guaranteed by applying methods of interference suppression, which can be subdivided into interference cancellation and joint detection (JD). The basic principle of IC relies on the fact that the user signals radiated by different users arrive with unequal power levels at the receiver. These differences of power levels make it possible to detect, as a first step, the strongest user signal by, for example, a RAKE receiver, and to eliminate this signal from the total received signal. In subsequent steps, by repetition of this procedure all the other user signals can be detected in decreasing order of power levels. In the case of JD, the a-priori knowledge about the CDMA codes of the different users is exploited when separating the user signals simultaneously in the receiver. JD can only be performed if sufficient knowledge about the impulse responses of the involved radio channels is provided in the receiver.<>