Adaptive decorrelating detectors for CDMA systems

Abstract

Abstract. Multi-user detection allows for the efficient use of bandwidth in Code-Division Multiple-Access (CDMA) channels through mitigation of near-far effects and multiple-access noise limitations. Due to its inherent noise and multipath immunity, CDMA multi-access is being considered as a platform for personal communication systems (PCS). As CDMA based digital communication networks proliferate, the need to determine the presence of a new user and integrate knowledge of this new user into the detection scheme becomes more important. The decorrelafing detector is a linear multi-user detector that is asymptotically optimal in terms of near far resistance; however, in the presence of a new unknown user, performance of the decorrelator is severely degraded. Adaptive decorrelators are constructed which adaptively augment an existing conventional decorrelator to demodulate a new active user in addition to existing users. Several likelihood ratio based schemes are employed. Both synchronous and asynchronous communication are investigated.

Traffic modeling and tracking for multiuser detection for random access networks

“…It would therefore be better off for the receiver to adopt the second approach, performing user identification prior to symbol detection. The problem of detecting active users has been addressed by several authors in a dynamic CDMA system [5,4,9]. A common feature of their approaches is that the detection is focused on current data window without utilizing the traffic continuity.…”