Blind adaptive minimum output energy RAKE receiver for DS/CDMA over multipath fading channels

To achieve a better tracking of time-varying channel parameters, a structure using blind adaptive minimum output energy (MOE) detection in conjunction with a RAKE combining diversity for direct-sequence code-division multiple-access (DS/CDMA) communications over the 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 normalized, complex-valued stochastic gradient descent (SGD) algorithm is developed for blind adaptation used in the MOE-RAKE. Simulation results show that, in the time-varying channel, the MOE-RAKE provides a better performance than the other blind multiuser detection techniques. In practice, to further improve the detector performance, a hybrid scheme started with blind adaptation for initial updates and then switched to the decision-directed algorithm is desired.