Joint detection for multicode transmission in downlink high speed UMTS

In this paper, a unified signal model for a multirate hybrid multicode and variable spreading factor CDMA channel model is proposed. It follows the structural principles of practical downlink high speed UMTS, and leads to a convenient algebraic form which allows for powerful receiver designs for multicode CDMA systems. We show the natural correspondence between the multiuser detection problem and the multicode detection problem. As a result, advanced joint multicode receivers, exploiting the available information about the multicode spreading sequences and mobile channel impulse response, can be applied in the mobile channel. As an example, a joint multicode detector based on the MMSE criterion is derived. Simulations demonstrate that using joint multicode receivers in the mobile channel offer a significant performance gain over the conventional Rake receiver.