RAKE receiver using blind adaptive minimum output energy detection for DS/CDMA over multipath fading channels

Abstract

To achieve better tracking of time-varying channel parameters, a structure using blind adaptive minimum output energy (MOE) detection in conjunction with RAKE combining diversity for direct-sequence code-division multiple-access communications over frequency selective multipath fading channels is introduced. In this MOE-RAKE structure, the signal replicas received from multiple fading paths are first independently produced by a bank of adaptive MOE detectors and then combined by a RAKE receiver for final symbol decision. A normalised, complex-valued stochastic gradient descent algorithm is developed for the blind adaptation used in the MOE-RAKE. Simulation results show that, in the time-invariant channel, the MOE-RAKE has a performance comparable to the previously proposed MOE and outperforms the conventional RAKE. In the time-varying channel, the MOE-RAKE performs better than the other blind multiuser detection techniques. In practice, to further improve the detector performance, a hybrid scheme started with blind adaptation for the initial updates and then switched to the decision-directed algorithm is desired.