【作者】 周薇；

【导师】 戴彬；

【作者基本信息】 华中科技大学 ， 通信与信息系统， 2012， 硕士

【摘要】 随着第三代移动电话的出世，3G手机已经能够提供除了语音和SMS之外的更多种信息服务，比如网页浏览，电子邮件的查看，电话会议等。特别是近阶段YouTube，Facebook，Twitter等社交网络服务的出现与快速普及，人们可以方便地通过移动设备共享图片和视频，发布日志，讨论感兴趣的话题。这使得移动设备接入互联网越来越流行，给移动通信的应用发展提供了新的契机。无线协作内容分发系统就是利用移动设备间的短距离连接，通过他们的相互协作来实现内容分发过程。本文首先简要介绍了无线协作内容分发系统，详细描述了其常用架构及典型的实际应用场景，并对无线协作网络的研究现状及数据分发过程中冗余策略的研究现状进行了归纳和总结。根据网络编码应用于小型手持设备的相关研究与测试，本文说明了在无线协作内容分发系统中应用网络编码的可行性，继而通过描述网络编码给内容分发系统的传输信息量，安全性等方面带来的益处说明了网络编码技术应用的必要性。根据无线协作内容分发系统的实际应用场景的描述，本文对其模拟场景进行了具体的方案设计，并在OMNeT++仿真平台上进行了其仿真场景的搭建，对场景内成功恢复原始数据的移动节点的百分比和节点恢复整个原始文件所需的平均时间这两个系统性能参数进行了评估，并分析了移动节点数目，存储节点数目，存储节点的移动特性等因素对这些性能参数的影响。分析显示，在不完全协作的情况下，移动节点的数目对系统性能参数影响不大，而存储节点的数目则对系统性能存在影响，在一定范围内，存储节点数越多，系统的总体性能越好。另外，存储节点的位置分布与移动速度对整个系统的性能也存在较大影响，当存储节点均匀分布于移动场景内，或者有效分布于用户密集区时，性能较好，而且选择移动速度和移动范围相对比较固定或不那么剧烈的节点作为存储节点较为合理。最后，根据前面得到的仿真实验结果，制定了新的存储节点的选取机制来取代随机选取机制，通过性能对比发现，新的选取机制能够实现性能优化。更多还原

【Abstract】 With the birth of the third generation mobile phone, services available on the3Gtelephone are no longer limited to voice and SMS. Multimedia interaction and mobile webbrowsing also become more and more important. People can easily share pictures andvideo, post to a blog and discuss interesting topics, expecially with the rapid spread ofSNS, such as YouTube, Facebook, Twitter, etc. The wireless cooperation contentdistribution system achieves the content distribution process using the short range linkbetween the mobile devices, namely, cooperation.This paper first introducts the wireless cooperation content distribution system, andthen summarizes its relevant study and redundancy policy study in the process of datadistribution.According to the research and testing about network coding applicated on smallhand-held devices, this paper illustrates the feasibility and need of network coding for thewireless cooperation content distribution system.The simulation scenarios of the wireless cooperation content distribution system isdesigned and realized on the OMNeT++simulation platform. This paper evaluates theperformance parameters of the simulation system, including the percentage of the mobilenodes recovered the original file and the average time for nodes to recover the whole file,and analyzes the impacts of several factors towards these performance parameters, such asthe number of mobile nodes, storage nodes and the mobility features of the storage nodes.Study shows that the number of storage nodes has influence on system performance,while the number of mobile nodes has little impact in the case of incomplete cooperation.Within a certain range, the more storage nodes, the better the overall system performance.In addition, the location and speed of the storage nodes also have a great impact on systemperformance. When the storage nodes uniformly distribute within the area, or distribute inthe user-intensive area effectively, the performance is better. And it’s more reasonable toselect the nodes as the storage nodes whose speed is small.Finally, according to the previous simulation results obtained, a new selectionmechanism of the storage node is given to replace the random selection mechanism. And itis proved that this new selection mechanism can achieve performance optimization.更多还原