Size Matters: Size-based Scheduling for MPEG-4 over Wireless Channels

For bursty traffic with a large peak-to-average ratio and a stochastic channel, is it possible to minimize the response time of every flow while maximizing the effective channel utilization and maintain fairness? This is the question we address in this paper. In wireless networks with a single shared channel, channel arbitration is a core issue for flows with throughput and timeliness requirements on the uplink and peer-to-peer links where the instantaneous demand is not known. This paper presents a link layer frame scheduling algorithm for delay-sensitive variable bit rate traffic, such as high-rate multimedia (MPEG-4), over a wireless channel. We evaluate our scheduling algorithm over two Medium Access Control (MAC) architectures and compare it to four scheduling strategies that cover a range of classes: TDMA, proportional share algorithms, real-time scheduling algorithms, and size-based scheduling algorithms. Detailed simulation results, with full-length MPEG-4 movie traces over a fading wireless channel, show that Fair-Shortest Remaining Processing Time (Fair-SRPT) outperforms other algorithms in terms of QoS performance, channel utilization efficiency and response time under all utilization levels and channel error rates. Our Fair-SRPT scheme avoids the classical SRPT problems of preferring small jobs by using normalization to mean reservations. An attractive feature of the proposed approach is that it can be implemented with no modifications to the IEEE 802.11e and IEEE 802.15.3 high-rate personal area network standards.