【作者】 郭雪莲；

【导师】 吴玉成；

【作者基本信息】 重庆大学 ， 通信与信息系统， 2009， 硕士

【摘要】 随着技术、社会的发展以及Internet的普及,人们对语音、视频、数据等业务的需求不断增加。无线网络能够使人们“随时随地”接入网络的要求得到满足。IEEE802.16做为一种具有竞争力的宽带无线城域网接入技术,实现了标准全球统一的目标。IEEE802.16MAC层协议对QoS保障机制进行较为完善的定义,制定了完备的信令体系、基于QoS的业务调度类型、带宽请求与分配机制等。研究实现IEEE802.16QoS保障的无线资源管理算法具有重要的意义。接入控制是QoS保障中的重要一环,它的主要任务是根据一定的策略对是否允许接入新到业务进行判决。新业务的加入有可能导致网络中原有业务的QoS性能有所下降;但是,网络需要容纳尽可能多的业务。接入控制用来在这对矛盾中找到一个平衡点,使网络中业务的QoS得到保证,同时使带宽利用率保持在较高的水平。论文在对IEEE802.16体系结构以及无线网络中的接入控制技术介绍的基础上,针对QoS实现机制中的接入控制技术开展了研究,主要内容如下:1、对MAC层QoS机制做了较为详细的分析,完善其QoS实现架构,给出了一种方案。对方案中主要模块的功能进行了定义,并描述了架构中信令、数据交互时BS和SS端所进行的操作。2、研究了一种基于门限策略的接入控制算法。为了保证切换过程中通话的连续性和实时业务的高QoS要求,算法定义了业务之间的优先级,根据优先级设置了5个门限。这些门限控制系统资源不同占用情况下允许接入不同优先级的业务。同时,为增加系统的接入连接数和带宽利用率,利用ERTPS、RTPS和NRTPS业务具有适应性带宽的特点,算法还引入了一种带宽借用的机制。仿真结果表明,这种设置门限的方式保证了高优先级业务的接入成功率,但牺牲掉了低优先级业务的部分性能。3、考虑到IEEE802.16网络中业务具有不同的速率要求,改进了一种基于权值的动态接入控制算法。将测量单位时间内业务的平均到达率与平均传输速率乘积的比做为权值,为每类业务分配带宽。仿真结果表明,相比于原算法中只采用业务到达率的比为权值来分配带宽的方式,改进的权值取值方式能够比较准确的反映各类业务的实际带宽需求,改善系统在阻塞率、掉线率以及带宽利用率方面的性能。更多还原

【Abstract】 With the development of technology and society, as well as the popularity of Internet, requirements of sounds,video and data are increasing. Wireless communication satisfy people’s desires of accessing network wherever and whenever. As a competive technology of Broadband Wireless Metropolitan Area Network, IEEE802.16 provides a uniform worldwide standard for Broadband Wireless Access. IEEE802.16 MAC layer protocol defines comprehensive QoS guaranteeing mechanism, including complete signaling system, scheduling service types and bandwidth request/allocation, and so on.The research on wireless resource management algorithms for IEEE802.16 is of great significance.Call admission control is very important for QoS guaranteeing. Its main task is to determine whether allow a new service flow or not according certain policy. The entry of new one may decrease current online services’QoS performance. However, network has to absorb businesses as many as possible. Call admission control can be used to find the trade-off to ensure the Qos of existent services, meanwhile maintain the bandwidth utilization at a high level.Based on the introduction of IEEE802.16 system and call admission control technology, this thesis is specially about call admission control of Qos realization. The main contents are as follows:1. The QoS mechanism of MAC layer was analyed in detail. A proposal was posed in order to perfect the QoS realization architecture. The main functional modules of this architecture were defined. The operations of SS and BS were described when signaling or data were exchanging between them.2. Call admission control algorithm based on a threshold strategy was studied. In order to maintain conversation in handoff process and ensure higher QoS requests for real time services, this algorithm defined priorities among services. Five thresholds were set according to above-mentioned priorities. Different priority services were admitted under different bandwidth usage circumstances, which was controlled by these thresholds. A bandwidth borrowing mechanism was adopted by taking advantage of the adaptive bandwidth traits of ERTPS、RTPS and NRTPS in order to maximize the number of connections and bandwidth utilization.The simulation results showed that the method of setting thresholds guaranteed high-priority services better access ratio at the cost of low-priority services’access ratio.3. Considering the various rates of services in IEEE802.16 network, this thesis improved a weight-based dynamic call admission control algorithm. The product of average arrival rate and transfer rate in measurement unit time were used as weight to distribute bandwidth for different services. The simulation results showed that, comparing with the old method which used average arrival rate as weight to allocate bandwidth only, the improved method could reflect the bandwidth requirement of each service more exactly. In this way, it improved the blocking probability, dropping probability and bandwidth utilization of system.更多还原