Scheduler Design for Multiple Traffic Classes in OFDMA Networks

This paper considers some scheduler structures that are executable in environments of multiple traffic classes and multiple frequency channels. In designing a scheduler structure for multiple traffic classes, we first propose a scheduler selection rule that uses the priority of traffic class and the urgency level of each packet. Then we relax the barrier of traffic class priority if a packet of higher priority has some room in waiting time. This gives us a chance to exploit multi user diversity, thereby giving more flexibility in scheduling. Our considered scheduler can achieve higher throughput compared to the simple extension of conventional modified largest weighted delay first (MLWDF) scheduler while maintaining the delay performance of QoS class traffic. We also design a scheduler structure for multiple frequency channels that chooses a good channel for each user as much as possible to exploit frequency diversity. The simulation results show that our proposed scheduler increases the total system throughput up to 50% without degrading the QoS performance of delay. Our schedulers are suited to be deployed for OFDMA systems like IEEE 802.16 systems that have plenty of frequency channels and use the adaptive modulation and coding (AMC) scheme.