AMC and channel-awareness for QoS-based scheduler design in WiMAX networks

Quality of service (QoS) differentiation is one of the keys to success for WiMAX (Worldwide Interoperability for Microwave Access) networks. Although the IEEE 802.16 standard issued some guidelines to design a QoS architecture, for the most part implementation details are left to manufacturers. Focus in this paper is on channel-aware scheduling policies to be implemented in the WiMAX Base Station for the delivery of downlink data traffic to fixed subscriber stations in a point-to-multipoint topology. This paper investigates on the effect of adaptive modulation and coding (AMC) schemes on the performance of the designed schedulers. Evaluation of the scheduling techniques will be based on their ability to provide QoS differentiation among traffic classes and fairness in the treatment of data flows in the same class. We expect that although AMC can be effectively used to dynamically adapt to variable channel conditions, it is not sufficient to guarantee inter-class traffic differentiation and intra-class fairness unless the scheduler also accounts for compensation of lost transmission opportunities of each single data flow.