A Study on the Characteristics of the Proportional Fairness Scheduling Algorithm in HSDPA

Abstract

In the packet-switched domain of the universal mobile telecommunications system (UMTS), scheduling algorithms such as the proportional fairness (PF) and round robin (RR) are used to decide on resource allocation (time and code space) for the users. According to the literature, the PF algorithm will provide significant throughput gain only if the channel variation is slow enough for the scheduler to track but fast enough such that it does not have to wait for too long in order to experience a constructive fading. In this paper, the authors provide a comparison study between the PF & RR algorithm. Matlab simulations are conducted under various different settings and environments in order to gauge and understand the characteristics of the PF scheduler. Simulation results show that under average channel conditions with fading within 5 dB and user diversity of 5, the PF provides a cell throughput gain of 5% over the RR and an individual UE bit rate gain of 7% over RR. When simulated with a higher SNR margin of 10 dB and user diversity of 10, the PF showed better performance compared to the RR, with a cell throughput gain of 18% and an individual bit rate gain of 20% over those achieved by the RR. This seems to suggest that the PF is able to better adapt to an increased user diversity and signal-to-noise (SNR) margin compared to the RR. The findings in this paper underscore the critical characteristics of the proportional fairness scheduling algorithm under different channel conditions. The findings also set the tone for further research to optimise the trade-off achieved by the PF.