Joint Downlink Power Control and Multicode Receivers for Downlink Transmissions in High Speed UMTS

: We propose to combine the gains of a downlink power control and a joint multicode detection, for an HSDPA link. We propose an iterative algorithm that controls both the transmitted code powers and the joint multicode receiver filter coefficients for the high-speed multicode user. At each iteration, the receiver filter coefficients of the multicode user are first updated (in order to reduce the intercode interferences) and then the transmitted code powers are updated, too. In this way, each spreading code of the multicode scheme creates the minimum possible interference to others while satisfying the quality of service requirement. The main goals of the proposed algorithm are on one hand to decrease intercode interference and on the other hand to increase the system capacity. Analysis for the rake receiver, joint multicode zero forcing (ZF) receiver, and joint multicode MMSE receiver is presented. Simulation is used to show the convergence of the proposed algorithm to a fixed point power vector where the multicode user satisfies its signal-to-interference ratio (SIR) target on each code. The results show the convergence behavior for the different receivers as the number of codes increases. A significant gain in transmitted base station power is obtained.