Cross-Layer Design and Optimization of CDMA Networks in Frequency-Selective Fading Channels

The cross-layer optimization technique in a recent paper [1] is extended and analyzed for frequency-selective channels with maximum ratio combining (MRC) coherent RAKE receiver. We assume random arrival time for a new user within a frame, and consider discrete spreading factors as a practical case. We show that the optimum outer-loop SNR-target does not depend on the received number of paths (L_p), and neither is dependent on the Uniformly-distributed arrival time of new users. Furthermore, an increase in L_p reduces the sum-throughput and the achievable gain in sum-throughput through our optimization approach.