【作者】 梁建新；

【导师】 张朝阳；

【作者基本信息】 浙江大学 ， 通信与信息系统， 2005， 硕士

【摘要】 宽带无线接入技术作为下一代通信网中最具发展潜力的接入技术之一，正受到业界越来越多的关注。IEEE802.16系列规范(也被称为WiMax)的制定，就是为了适应宽带无线接入的快速发展，并为之提供一个全球统一的标准。 本文的研究工作主要基于IEEE802.16d标准。为了迎接高用户量、高数据传输量和多种业务并存给网络无线资源管理策略带来的挑战，提高的系统性能，本文将主要从资源分配和节能控制两个角度入手进行研究。主要的研究手段是数学推导和仿真，仿真工具采用Matlab和OPNET。 IEEE802.16可以使用多种物理层模式，其中的OFDM和OFDMA模式都是基于OFDM技术。本文关注OFDMA模式下的下行资源分配问题。根据现有的算法，基站可以按照用户的服务质量(QoS)和信道情况自适应地将子载波、比特和功率分配给不同的用户，使发射总功率最小，以达到远高于传统多用户方式的功率效率和系统容量。然而这些已有算法都隐含地假设了一种线性环境，即在发射端没有功率(或者说信号幅度)限制。实际的OFDM系统却往往很难保证这一点。在非线性的系统里，这些算法性能将可能受到影响，用户也将无法获得要求的QoS。本文将讨论这种自适应的OFDMA系统中非线性对用户最终信噪比的影响，并提出一种在保证用户QoS前提下最小化发射功率的资源分配算法，之后通过仿真结果来研究非线性对OFDMA系统性能的影响。 由于终端的可移动性，如何节约能量和延长待机时间是设计中的又一个重要问题。本文根据IEEE802.16协议TDD模式下物理层的特点，提出一种针对数据业务的节能控制协议，当只有下行业务时，终端根据其业务量自适应地调整休眠时间的长度，在休眠结束时立即侦听寻呼信道以便接收信息。这种协议可以将终端侦听寻呼信息所消耗的能量减少到最少，其代价是包的时延增大，并可能导致基站的包缓存队列溢出。但是算法可以通过适当设定休眠时间的长度保证溢出概率在允许的范围内。因为牺牲了时延性能，本协议适用于非实时性的数据业务。最后，为了适应动态的网络环境，增加了一种流量预测机制，使得休眠时间可以根据流量状况动态调整，以满足队列溢出率的要求。仿真表明，该协议的节能效果显著。更多还原

【Abstract】 As one of the most promising technology in the next generation communication network, BWA (Broadband Wireless Access) has drawn much attention and became a hot spot of researching. The IEEE 802.16 standard is proposed as a world standard of BWA.Our work is based on IEEE 802.16 standard. To enhance the system performance to confront the challenge of supporting more users and providing higher rate and multiple services in future networks, we make research in perspective of radio resource management, mainly on two spots: resource allocation and energy conserving.IEEE 802.16 specifies several physical layer modes, among which, OFDM and OFDMA modes are both based on OFDM technology. In this work, we first investigate downlink resource allocation problem in OFDMA mode. According to present algorithms, to improve system capacity, the base station may adaptively allocate subcarrier, bit, and power to users based upon their Quality of Service (QoS) requirement and channel conditions. The resulted OFDM signals are more subject to non-linearity which may cause signal amplitude clipping and degrades all users’ QoS granted by the radio resource allocator. This work will study the influence of non-linearity on the final SNR performances in such a system, and propose a novel resource allocation algorithm considering the non-linearity of practical transmitting system. The system performance is simulated and compared with that of an ideal system which has no non-linearity.Another major issue in today’s wireless networks is the limited energy of the communication devices. In this work, an energy-conserving protocol which complies with TDD mode of IEEE 802.16 standard is proposed. This protocol is applicable to downlink data service. The base station buffers data packets for each mobile station (MS), and pages them on paging channel. As soon as the MS wakes up from sleeping mode, it turns on receiver. If there is a piece of information for that MS, it tries to access the network and receive packets. When there is no packet left in buffer queue, the MS switches to sleeping mode. This protocol may save energy at expense of packet delay performance and the probability of queue overflow. By setting the sleeping time properly, the overflow probability can be reduced to a required limit. Simulation proves the analytical results and shows a significant improvement of energy-consuming performance.更多还原