On the effects of Doppler bandwidth, network load and power control threshold on the UMTS/FDD radio interface performance

In this paper the behavior of the UTRA-FDD radio interface of UMTS, based on wideband CDMA technology, is investigated at different conditions of Doppler bandwidth, network load and power control threshold. To this aim, a general simulation setup has been developed, which includes a cellular environment with hexagonal layout and uniform user distribution, a propagation channel with path-loss, log-normal shadowing and Rayleigh fast fading, a transmission system with SIR-based closed loop power control, convolutional coding with interleaving and RAKE receiver. Among the simulation results, the SIR process, the frame error probability process and the energy efficiency of the transmitters are analyzed. It is shown that power control provides a good level of fairness across the system and, even though an increasing network load reduces the fraction of users fulfilling the performance requirements, the behavior of the satisfied users remains unchanged. Moreover, the robustness to network load improves as the fading changes faster.