An asynchronous multiuser CDMA detector based on the Kalman filter

In this paper, we introduce a multiuser receiver based on the Kalman lter, which can be used for joint symbol detection and channel estimation. The proposed algorithm has the advantage of working even when the spreading codes used have a period larger than one symbol interval (\long codes"), unlike adaptive equalizer-type detectors. Simulation results which demonstrate the performance advantage of the proposed receiver over the conventional detector, the MMSE detector and a Recursive Least Squares (RLS) multiuser detector 1] are presented. A thorough comparison of the MMSE detector and the proposed detector is attempted because the Kalman lter also solves the MMSE parameter estimation problem, and it is concluded that, because the state-space model assumed by the Kalman lter ts the CDMA system exactly, a multiuser detector based on the Kalman lter must necessarily perform better than a non-recursive, nite-length MMSE detector. The computational complexity of the detector and its use in channel estimation are also studied.