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

Abstract

Previous studies showed 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. However, the computations of these blind approaches are an order of magnitude higher than existing adaptive minimum output energy (MOE) receivers which require at least knowledge of the desired user's channel response. Although the high-complexity problem can be alleviated by constrained adaptive filtering, 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, and yet requires no knowledge of the desired user's channel characteristics.