Coherent Rake reception using noisy channel estimates [DS-CDMA cellular radio]

With traditional Rake reception, channel estimates are used to combine despread values. In this paper, a maximum-likelihood approach is used to reformulate the Rake combining weights, accounting for the channel estimation error. Specifically, Ling's formulation is extended to include fading, noise, and channel estimation error correlation between fingers. The resulting combining weights are similar to the generalized Rake receiver, except that the known channel response is replaced by a minimum mean-square error (MMSE) estimate, and the noise covariance matrix is augmented by a term related to channel estimation. The performance of this and other combining approaches are compared, showing how performance depends on the available energy for channel estimation and the Rake finger placement strategy.