Effect of Fast Cell Selection Coupled with Fast Packet Scheduling in High-Speed Downlink Packet Access

摘要

This paper investigates the effect of fast cell selection (FCS) associated with fast packet scheduling methods and hybrid automatic repeat request (ARQ) such as Chase combining, in which the optimum cell (or sector) transmitting a slot-assigned downlink shared channel (DSCH) is selected based on the received signal-to-interference power ratio (SIR), for high-speed downlink packet access (HSDPA). The Round robin (RR), Proportional fairness (PF) and Maximum carrier-to-interference power ratio (CIR) schedulers are used as the scheduling algorithm. The simulation results elucidate that although almost no additional diversity gain through FCS is obtained for the PF and Maximum CIR schedulers, the improvement in throughput by FCS coupled with the RR scheduler is achieved, assuming the continuously transmitted packet model. In addition, we clarified that the effect of FCS is small when only inter-sector FCS is performed; however, inter-cell FCS is effective in improving the radio link throughput for the access users with a lower received SIR near the ceil edge. Consequently, the radio link throughput at the cumulative distribution of 20% of soft handover users when both inter-sector and inter-cell FCS are performed is increased by approximately 20% and 60% for PF and RR schedulers, respectively, compared to that without FCS, i.e. with hard handover. Furthermore, we also show that when a traffic model such as the modified ETSI WWW browsing model is taken into account, the effect of FCS is greater than that assuming continuous packet transmission, because the diversity effect yielded by the fast packet scheduling becomes relatively small. The user throughput at the cumulative distribution of 20% employing both inter-sector and inter-cell FCS is increased by approximately 60% compared to that without FCS.