Selective multiuser detection for cellular CDMA systems

We propose a new computationally efficient multiuser detection scheme, based on the multiuser detection of a subset of pre-selected users, and conventional detection of the rest of the users. This approach, called selective multiuser detection (SMD), allows for full exploitation of available processing power at the receiver by use of multiuser detection, and provides the remedy for computational complexity of multiuser detection schemes when the number of active users increases beyond the processing capability. We analyze the SMD scheme using a decorrelator as the multiuser detector, and derive the capacity for the single-cell and the multi-cell CDMA cellular system. We propose and examine three different criteria for selection of users to be processed by the multiuser detector. The capacity improvement with respect to the conventional CDMA detector combines the gain from multiuser detection and reduction of other-cell interference. We analyze the two effects and evaluate them numerically. The results indicate that the SMD is a promising alternative for multiuser detection-oriented CDMA systems with large number of active users