【作者】 张青波；

【导师】 何加铭；

【作者基本信息】 宁波大学 ， 通信与信息系统， 2013， 博士

【摘要】 WiMAX(Worldwide Interoperability for Microwave Access)即全球微波互联接入，是一项新兴的宽带无线通信技术，能提供面向互联网的高速连接以及较大覆盖范围的无线连接。随着WiMAX成为继CDMA2000(Code Division Multiple Access2000)、WCDMA(Wideband Code Division Multiple Access)和TD-SCDMA(Time Division-Synchronous Code Division Multiple Access)之后的全球第4大3G(The3nd Generation MobileCommunication System)标准，WiMAX技术正被广泛的研究和应用。与其他3G技术相比，WiMAX的技术优势体现在：传输距离远、更高速的无线宽带接入、能提供基于QoS（Quality of Service）的无线多媒体通信服务等，可以很好地应用于一些灾害频发和突发事件等地区和场合的无线通信。另外，随着全球性的WiMAX论坛组织的成立，促进了WiMAX设备的通用性认证和确保不同厂商设备的交互使用，进一步推广了WiMAX技术。无线宽带接入WiMAX系统应用难点是对协议算法的开发。首先理论分析了WiMAX协议相关技术，给出其分析模型，影响WiMAX技术应用的主要问题为呼叫接纳控制机制、分类压缩机制和协同中继等，这也是全文的基础和出发点。针对系统繁忙时系统资源紧张的问题，提出了一种基于收益/支出比的呼叫接纳控制算法。该方法利用顾客满意度指数模型计算系统收益，以系统消耗的总带宽为支出，最终以此收益/支出比作为是否接纳新业务流的判决依据。不仅有效保证了系统对业务的服务质量，而且复杂度低，具体实施容易。利用时间离散的四维马尔科夫队列模型进行业务加载仿真，与经典的截止优先权算法相比，本文提出的算法在系统繁忙时，有较高的接纳率和吞吐量，提高了系统效率。针对现有的分类算法无法直接应用于WiMAX系统问题，提出了一种基于地址分块异或和哈希查找的包汇聚子层分类算法，实现了高层协议数据单元的快速查找分类。利用地址分块提高了匹配速度，分块异或有效抑制了内存空间爆炸。该方法复杂度低，支持范围匹配，而且动态更新速度快，在存储空间性能和时延上都满足了系统QoS的要求。仿真结果表明，本文提出的算法搜索速度高于典型的AQT(Area-based Quad Tree)算法和HiCuts（Hierarchical Intelligent Cuttings）算法。针对现有压缩算法复杂度高等问题，分析研究了媒质接入层分段协议数据单元报头及子头格式，创新性地利用分段协议数据单元报头保留位和子头保留位进行编码实现了对分段协议数据单元中的连接标识字段进行压缩。该算法能根据无线信道环境实现自适应压缩。仿真结果表明提出的压缩算法压缩效率高，丢包率低，达到了满意的压缩效果。针对平均功率算法功率效率低的问题，提出了一种基于协同中继AF(Amplif andForward)网络的优化功率分配算法。该方法采用固定阈值自适应调制方案，根据调制符号所含比特数对用户信道进行功率注水，降低了算法复杂度，提高了带宽效能。在此基础上，用户子载波再根据信道质量进行功率微调，减少由于信道子载波信噪比的差异造成的功率分配不均。与平均功率算法相比，本文提出的优化功率分配算法不仅功率效率高，而且能较好地改善系统误码率性能。论文紧密围绕WiMAX系统的呼叫接纳控制机制、分类压缩机制和协同中继等关键技术展开研究，提出了一些改进的算法。文中分析以及提出的方法和解决方案，对WiMAX系统的研究和实践具有一定的参考意义。更多还原

【Abstract】 WiMAX named as Worldwide Interoperability for Microwave Access is an emergingbroadband wireless communications technology, it can provide high-speed connection for Internetas well as a larger wireless coverage. As WiMAX becomes the world’s fourth3G standardfollowing the CDMA2000, WCDMA and TD-SCDMA, WiMAX technology is being extensivelystudied and applied. Compared with the other3G technologies, WiMAX technology has technicaladvantages such as longer transmission distance, higher-speed wireless broadband access, and canprovide QoS-based wireless multimedia communication services. It can be well applied forwireless communication in some areas of frequent disasters and sudden events. In addition, itpromotes the generic certification of WiMAX equipment and ensures the interactive use of devicesfrom different manufacturers with the establishment of the global WiMAX Forum organization,thus WiMAX technology is further used. One of the application difficulty of wireless broadbandaccess WiMAX system is the development of the protocol algorithms.The dissertation firstly analyze the related techniques of WiMAX protocol and present analysismodels. The main problems of the application of WiMAX technology are call admission controlmechanism, classification&compression mechanism and cooperation relay, which is foundationin the whole dissertation.According to the problem of resource constraints when the system is busy, this dissertationproposed an income/expenditure ratio based call admission control algorithm. CustomerSatisfaction Index model was used to calculate system income, system’s total bandwidthconsumption was used as expenditure, thus the system used this income/expenditure ratio to judgewhether or not to accept a new business. The proposed scheme can not only ensure business’sservice quality effectively, but also be easily implemented with low complexity. Four-dimensionaltime discrete MMPP (Markov Modulated Poisson Process) queuing model was used to simulatebusiness load. Compared with the classic Cutoff priority algorithm, our scheme has higheracceptance rate and throughput, and improves system’s efficiency when it is busy.For existing classification algorithms can not be directly applied to the WiMAX system, anaddress block XOR and Hash look-up based packet convergence sub-layer classification algorithmwas proposed, realizing the quick lookup and classification of higher-layer protocol data. Addressblock was used to improve searching speed, block XOR effectively suppressed the memory space explosion. The proposed algorithm can support range matching and realize quick dynamic updatewith low complexity, and its storage performance and delay meet the system’s QoSrequirement.Simulation results proved that the proposed scheme has higher search speed comparedwith the typical AQT (Area-based Quad Tree) algorithm and HiCuts (Hierarchical IntelligentCuttings) algorithm.Aiming at the problems of high complexity in present compression algorithms, the header andsub-header format of segmented protocol data unit were analyzed in media access control layer,and connection identifier field was innovatively compressed using the reserved bits of header andsub-header to decode in segmented protocol data unit. The scheme can realize adaptivecompression according to wireless channel environment. The simulation results verified that thepacket loss rate of proposed compression algorithm is low with high compression efficiency, andachieves satisfactory compression effect.According to low power efficiency in average power algorithm, an optimized power allocationalgorithm was proposed based on cooperative relay AF (Amplify-and-Forward) network. Thescheme used a fixed threshold as adaptive modulation, channel adopted water-filling methodaccording to the number of bits contained in the modulation symbol, reducing the complexity ofthe algorithm and improving bandwidth performance. On this basis, power was trimmed accordingto channel quality in sub-carrier, reducing power’s uneven distribution caused by the difference ofsub-carrier’s signal-to-noise ratio. Compared with the average power algorithm, the optimizedpower allocation algorithm can not only enhance power efficiency, but also improve the system’sBER performance.This dissertation focuses on key technologies of the call admission control mechanism,classification&compression mechanisms and cooperative relay in WiMAX system, someimproved algorithms are proposed. The proposed algorithms and solutions are helpful in WiMAXsystem.更多还原