Performance of Scheduling Algorithms under Mobility for Multimedia Services in OFDM Systems

摘要

Scheduling algorithms are playing a key role in overall system performance of broadband wireless systems (BWS). Maximal SNR (MaxSNR) and Round Robin (RR) are two conventional scheduling strategies which emphasize efficiency and fairness respectively. Proportional Fair (PF) algorithm provides tradeoff between efficiency and fairness. In this paper, we apply PF to IEEE 802.16a OFDM based BWS and name it OPF. We also propose a new algorithm for multimedia services: Normalized Multimedia Adaptive OPF (NMAOPF). Adaptive modulation and coding scheme is applied in time varying and frequency selective fading wireless channel. System performances are compared in efficiency and fairness with and without user mobility. Efficiency is in terms of throughput, mean packet delay and packet drop ratio; fairness is in terms of user satisfaction rate and average user rate. Joint PHY and MAC layer simulation results show that: within the traffic range of 55 to 70 Mbps, compared with RR and MaxSNR, the performance of OPF is in between. Our proposed NMAOPF outperforms all others without user mobility, while under mobility, it is not as good as MaxSNR but better than OPF and RR.