Study On Uplink Bandwidth Scheduling Algorithm Of IEEE802.16 Protocol

With the development of broadband wireless communication technology and more and more applications of the multimedia services, broadband wireless access technology should have the ability to guarantee the quality of services (QoS) required by users. In order to meet the application requirements of broadband wireless access in the future, IEEE organization has proposed a series of 802.16 standards. In IEEE802.16 standards the technology adopted by physical layer and the mechanism of MAC are defined detailedly. To support the QoS, services are divided into different scheduling types according to their QoS characters, and various service connections are associated with different QoS parameters. Furthermore, the scheduling algorithm for unsolicited grant service (UGS) is defined, but the standard don't give explanation for scheduling structures and concrete scheduling algorithms for the other types of services. Therefore, studying on bandwidth scheduling structures and algorithms of 802.16 system has extremely vital significance.The proposed scheduling architectures and algorithms are studied and analyzed in depth in the thesis. Most algorithms are just focus on the aspect of guaranteeing the QoS of services, but not giving considerations to the scheduling fairness of system. Thus a novel bandwidth scheduling algorithm based on pre-allocation mechanism is proposed to provide guarantee for the QoS of services and to resolve the problem of servicing unfair in the scheduling process. To make sure the request of data rate of high priority services, this algorithm will pre-allocate some bandwidth resource for them firstly. Then for the rest of bandwidth, the real time polling services, non-real time polling services and best effort services are allowed to share through the changed priority deficit queue algorithm. The scheduling will not be stopped until the usable bandwidths are zero or all service flows have got required bandwidths.In order to realize that uplink bandwidths could be used fair and efficiently among various service connections which is belong to different SSs, a model of bandwidth scheduling based on Grant Per Subscriber Station (GPSS) mode is established. In this model, the weight max-min fair algorithm is introduced to base station, and the novel bandwidth scheduling algorithm based on pre-allocation mechanism is used by subscriber stations. Because it has considered that various services have different requirement for QoS, so the weight max-min fair algorithm could allocate bandwidths fairly among subscriber stations. The proposed novel algorithm makes the lower priority service flows obtain some service opportunities while the high priority service flows' QoS are guaranteed as well. From the above, we can see that it has the ability to resolve the problem that the lower priority service flows are starved because most bandwidths is occupied by the high priority service flows and little bandwidths could be provided to the lower priority service flows for a long time in a certain degree.The weighted max-min fair scheduling algorithm and the bandwidth scheduling algorithm based on pre-allocate mechanism are embedded into the designed system model, so the service rate of the subscriber station's bandwidth requests could be raised. Although the throughput and delay characteristic of real-time polling services are lost in some cases, but it gives consideration to allocate bandwidths for the lower priority service flows, so it has achieved scheduling fairness well from user nodes to services.