Adaptive Group-Blind Multiuser Detection Based on a New Subspace Tracking Algorithm

group-blind multiuser detectors for use in code-division mul-tiple-access (CDMA) uplink environments in which the base station receiver has the knowledge of the spreading sequences of all the users within the cell, but not that of the users from other cells. Yu and Høst-Madsen later developed an adaptive version of this detector for synchronous CDMA channels. In this letter, we develop a new low-complexity, high-performance subspace tracking algorithm and apply it to adaptive group-blind multiuser detection in asynchronous multipath CDMA channels. The detector can track changes in the number of users and their composite signature waveforms. We present steady-state performance as well as the ability of the receiver to track changes in the signal subspace. We also address the performance gain of the group-blind detector over its blind counterpart for this application. Index Terms—Adaptive multiuser detection, code-division mul-tiple access (CDMA) uplink, group-blind multiuser detection, sub-space tracking. I