Markov chain analysis of uplink subframe in polling-based WiMAX networks

IEEE 802.16 is proposed to provide middle-range access and high data rate for real-time transmission through wireless channel. The increasing of access range, data rate and total number of nodes makes the wireless media access more difficult and critical. To overcome access contentions from requests, IEEE 802.16 thus adopts a centralized-based polling MAC instead of random access control. In such a polling mechanism, the number of polls (NPS) within a frame period becomes an important factor. There are two main reasons. First, not all of the polled nodes have packets to be sent, and thus wastes bandwidth used for polling these nodes. Second, that the node has packets to be sent may not be polled immediately, and then increases polling delay. Therefore, this paper analyzes NPS based on the Markov chain analysis to minimize average polling delay while increasing network throughput. Numerical results indicate that the analysis results are very close to the simulation results. Moreover, the number of polls and the waste rate are also analyzed under various NDS and offered loads.