Adaptive hierarchical polling and cost-based call admission control in IEEE 802.16 WiMAX networks

IEEE 802.16 standard is proposed for providing high data rate and middle-range access to Internet through wireless access channel. The increasing of data rate, access range, and total number of wireless nodes makes the wireless media access control more difficult and critical. For minimizing collisions due access contention, IEEE 802.16 thus adopted a polling access mechanism for base station (BS) to polling all subscriber stations (SSs) in turn. Although the polling mechanism overcomes the access contention among all SSs, it suffers from long polling delay and inefficient channel allocation in such WiMAX networks while in the worst case that in the worst case of that a BS polls each SS or group at each frame period. Therefore, we proposed an adaptive polling approach with cost-based Call Admission Control (CAC) for increasing utilization of access channel and network reward, and reducing polling delay. Two mechanisms are proposed in this study, including a two-level adaptive scheduling mechanism for scheduling a dynamic polling list for QoS-based SSs and a cost-based call admission control mechanism for determining of accept a new incoming service flow or not. Numerical results indicate that the proposed approach outperforms IEEE 802.16 standard in fractional reward loss and average delay significantly.