节点文献
宽带无线接入网动态QoS机制研究
Research on the Dynimic Mechanism of QoS in Broadband Wireless Access Network
【作者】 曾菊玲；
【导师】 宋俊德；
【作者基本信息】 北京邮电大学 ， 电路与系统， 2010， 博士
【摘要】 随着宽带无线接入网的普及,其用户数和业务种类越来越多,宽带业务的QoS要求与无线资源的稀缺性和波动性的矛盾逐渐加剧,动态QoS机制研究网络在提供QoS保证的同时,如何跟踪无线资源,提高网络效率,是解决该矛盾的重要手段,越来越得到重视。本文深入研究了宽带无线接入网中动态QoS机制,其中包括支持跨层或优化的宽带无线接入网的QoS框架、链路独立层中优化的映射、链路依赖层中跨层优化的QoS映射、动态接纳控制四个部分,分别从整体结构、参数映射和关键控制技术研究了宽带无线接入网中动态QoS机制的实现方法。包括以下几个内容：1、提出了支持跨层或优化的QoS框架,框架具有链路独立层、链路独立-业务接口、链路依赖层的分层结构。在链路独立-链路依赖业务接口,通过虚拟QID及其资源管理器将链路信息屏蔽在接口内,在链路独立层可以不考虑链路信息,避免过分跨层设计带来的混乱。在链路独立层,通过定义通用层间接口,提供对通用优化QoS映射的支撑,通过基于该接口的优化映射,解决资源稀缺问题；在链路依赖层,通过定义链路层及物理层的QoS管理结构、功能模块以及QoS交互机制,提供对OFDM的物理层—链路层的跨层设计及动态QoS机制的支撑,在保证业务质量的同时,提高了网络资源的有效性和动态性,克服了OSI分层结构缺乏跟踪可变物理资源的机制、不能适应无线通信的缺陷,并且具有通用性。仿真结果说明该框架在QoS保证和系统效率上优于OSI分层结构。2、提出了链路独立层优化的QoS映射,包括：在用户级——应用级映射中,提出了基于最大似然估计的主观量化方法和基于最佳判决的最优多重衰减线性映射方法,使映射误差达到最小；在应用级——IP级提出了性能最佳结合模板的映射,不仅实现了性能最佳的业务类别映射,还能具体确定各应用业务帧映射的IP业务；在IP级——链路级优化的QoS映射中,提出了效率最优映射结合映射误差最小的链路带宽分配策略,双重优化使得在性能和效率上都能得到保证,仿真结果说明,该优化映射方法在业务质量和网络效率上都得到了提高。3、提出了基于OFDM子载波的AMC/ARQ跨层设计及QoS映射。通过建立状态持续时间相等的OFDM子信道FSMC(有限状态MARKOV信道),解决了目前基于状态幅度的FSMC不能支持AMC/ARQ跨层设计的问题,基于此,提出了基于OFDM频域子载波的AMC/ARQ跨层设计并进行了优化设计,收到了满足时延和丢包率且频谱效率最高的效果,实现了QoS跨层映射。针对OFDM子信道状态对高速移动的敏感性,基于相等持续时间的FSMM对跨层设计作出了进一步改进,得到了适应高速移动的AMC/ARQ跨层设计。最后以信道FSMC为基础,采用内嵌MARKOV链方法和队列方法,给出了AMC/ARQ跨层设计系统的丢包率、时延评估方法。仿真表明该跨层设计使得系统通过率有较大提高,误比特率有较大下降。4、提出了目前常见接入网的动态接纳控制策略。对IEEE802.11e的EDCA,通过OFDM子载波比特分配、自适应更新授予带宽等措施跟踪网络及业务动态特征,通过对分布式的、半模式化的每流接纳控制的测量及模式计算方法的改进,达到了保证业务质量的同时,系统效率提高,仿真结果显示性能优良；对HCCA,通过OFDM子载波比特分配,使物理资源分配最优化,基于单个可变比特流的丢包性能和可变比特的统计复用性能分析,提出了有效TXOP作为可变比特流的接纳标准,使带宽和丢包率同时得到保证,将比特分配和有效TXOP用以改进参考接纳机制,使QoS得到保证的同时,系统效率提高,仿真证明了这一点；对HCCA,还提出了根据业务优先权的站内OFDM子载波分配和接纳控制机制,仿真显示该方法对多媒体流效果较好；对802.16d/e,通过OFDMA的子载波及比特分配,在保证子站业务量比例和功率限制下,频谱效率达到最优,通过采用优化的带宽门限,资源予留机制中的用户满意度达到最优,通过两级调度机制,实现根据业务QoS要求选择信道的目标,充分保证业务质量,通过采用有效带宽作为接纳标准,可变比特流的带宽及时延和丢包率同时得到保证,仿真表明,基于上述措施的接纳控制在保证业务质量的同时,使系统效率达到了最大。
【Abstract】 Contradictions of scarcity and fluctuation of wireless resource and the requirement of QoS lead to dynamic mechanism of QoS in broadband wireless access network. The Dynamic mechanism is studied in this paper, which is consisted of the cross-layer framework of QoS, the optimal mapping of QoS parameters in link-independent layer, the cross-layer mapping of QoS parameters in the link-dependent layer and dynamic admission control. The realization of that dynamic mechanism is studied from the three aspcets—the whole cnfinguration and the QoS mapping as well as the crucial control in these five parts,respectively.1、The framework of QoS layered by the link-independent layer, the interface of link-independent layer to the service and link-dependent layer is presented to surpport the optimal or cross-layer stratage.In the interface,the virtual queen identity and its resource manager shield the information of the wire-less link so that it need not be considered in the link-independent layer.In the link-independent layer, a comman optical algorithm for QoS mapping based the general interface is given out to overcome the scarcity of wireless resource.In the link-dependent layer,the QoS manage structure of te link and physics layer and its functional moduels as well as the iteraction mechnical are defined to suport the cross-layer design between physics and link layer and the realization of dynamic control The simulation results show this framework outperform the layered one of the OSI. 2、The optimal mapping in the link-independent layer is addressed.The optimal muitiple line mapping between the user layer and the applying layer based on maximum likelihood decision of the statistical theory is presented to minimize the mapping error.The algorithm combining the best-quality-guarantee mapping with the moduel mapping is presented in appling layer to the IP layer,which can not only realize the best quality of service but also each packet.In the optimal mapping of the IP layer to the link layer, the dual optimal bandwidth allocation combining the highest efficiency algorithm for the sevice class and the laest error aigorithm for the bandwidth is presented. The simulation results show that these optimal algorithm enhance the quality of the service and the efficiency of the network.3、The AMC/ARQ cross-layer design and QoS mapping is suggested. The finite state Markov channel model(FSMM) based on the same time of the state of the subcarrier of the OFDM signal is build up as the base of that at first and it can support the AMC/AQ that the FSMM based on the amplitude can’t be used for.As the the results,the biggest frequency spectrum efficiency under the gurentee of the service is obtained. And then the futher improment on the AMC/ARQ of subcarrier of the OFDM aiming at its sensitivity to the vehicles based on FSMM and the QoS mapping are made,which result in the adapth of the AMC/ARQ to the vehicle. To use the design for the mapping,the loss ration and the delay of the paccket is addressed.The simulation results show that our optimal statage this design rsiae the through rate and low the bit error ratio greatly.4、The dynamic admission control is presented in some wide bandth access wirlees networks. In EDCA of the IEEE802.11e,the dynamic characteristics of the channel and service is tracked by adaptively allocation of bits in the subcarrier of OFDM and updating the granting bandwidth.The increasment of the efficiency of the system under the guarantee of the service is obtained by the improvement on the measurement of the control variables and the computation of the network model in the semi-model and center-asisted admission control per flow.All that is showed by the simulation.In HCCA of the IEEE802.11e,the optimization of the physical resources obtained by allocation of the bits in the subcarrier of OFDM.The effective TXOP is presented as the control variable of the admission based on the analysis of the drop characteristics of the single varable bits rate flow and the multiplexity of flows,which results in the bandwidth and the restriction of the drop are guranteed at the same time.The simulation is showed that the improved admission adopting the bits allocation and the effective TXOP outperformed that aforetime in throughout.And in HCCA,the adaptive subarrier allocation according to the service’s priority inter the station is also presented.The simulation shows it has better effect on multimedia flow by better synchronization.In 802.16d/e,the optimization of the efficiency of the frequency spectrum subject to the restriction of the ratio of the station’s service and the power of the station is obtained by the subcarrier assigned and the bits allocation. Adopting the optimized bandwidth threshold make the user’s satisfaction dgree in resourse reserve biggest.The two-level schedule is adopted to select the channel according to the service quality so that it guarantee the service effectively and the effective bandwidth as the control variable in admission so that the bandwidth and packet drop ratio are ensured at the same time.The simulation shows that the admission control based on the above methods optimize the efficiency of the system subject to the service’s quality.