A decorrelating RAKE receiver for CDMA communications over frequency-selective fading channels

Recent studies show that multiuser detection in code-division multiple-access (CDMA) communications can be performed without explicit knowledge of users' channel characteristics in a frequency-selective fading environment [1], [2]. However, the computations of these blind approaches are an order of magnitude higher than existing adaptive minimum output energy (MOE) receivers [3], [4] which require at least knowledge of the desired user's channel response. Although the high-complexity problem can be alleviated by constrained adaptive filtering [5], the tradeoff is a significant drop in receiver performance, especially when the multipath pattern is time varying, In this paper, we present an adaptive receiver for CDMA communications over frequency-selective, and possibly time-varying, wireless channels, A salient feature of the new receiver is that it has complexity and performance comparable to that of the well-known MOE receivers [3], [4], and yet requires no knowledge of the desired user's channel characteristics.