IEEE 802.16 無線寬頻網路中，提升頻寬資源利用率之排程演算法設計

Abstract

Improving bandwidth utilization is one of the important research issues, especially in the IEEE 802.16 wireless broadband networks. The IEEE 820.16 standard supports two network topologies, the point-to-multipoint networks and mesh networks. In this dissertation, bandwidth utilization improving scheduling algorithms are proposed for these two supported networks, respectively. For the point-to-multipoint networks, burst is an atomic bandwidth allocation unit for downlink and uplink transmissions in IEEE 802.16 orthogonal frequency division multiple access (OFDMA) systems. This dissertation investigates downlink burst scheduling problem in IEEE 802.16 OFDMA systems. Solving this problem with the objective of maximizing downlink bandwidth utilization, a burst fragmentation, packing and allocation algorithm is proposed to decide the position and shape of each burst in the downlink subframe. For further improving the downlink bandwidth utilization in an given burst allocation scenario, a burst shifting scheme is proposed to make neighboring bursts share and utilize wasted slots caused by the rectangular mapping constraint of bursts by means of arranging the position of the wasted slots in bursts. For the mesh networks, minislot is an atomic bandwidth allocation unit for data transmissions among subscriber stations and base station. This dissertation overcomes minislot scheduling problem for IEEE 802.16 mesh networks and formulates this problem as an integer linear programming model. Due to the high computational complexity for solving integer linear programming model at subscriber stations and the degrade of bandwidth utilization resulted from data collision problems and minislot insufficient problems, this dissertation proposes a decentralized minislot scheduling protocol to make subscriber stations, rather than the base station, schedule minislot usage for throughput gains in the IEEE 802.16 mesh networks. The decentralized minislot scheduling protocol includes minislot usage constraints and minislot decision strategies to alleviate data collisions and minislot insufficient problems as well as to increase bandwidth utilization. The proposed protocol not only can accommodate to the IEEE 802.16 standard, but also make subscriber stations schedule minislots with the latest minislot usage information. Based on the above mentions, this dissertation conducts a series of simulations to evaluate the performance of proposed bandwidth utilization improving scheduling algorithms for the two supported networks, respectively. The simulation results show that the proposed algorithms and protocol outperform related work in the bandwidth utilization.