基于可缓存机会性协作MIMO的视频缓存和功率算法研究

发布时间：2018-07-04 23:07

本文选题：协作MIMO + 缓存控制　；参考：《南京邮电大学》2017年硕士论文

【摘要】：随着科学技术的发展,在线视频播放应用对无线系统的性能要求越来越高。移动用户对视频数据的传输速率和视频播放的质量也提出了更高的要求。同时,用户终端视频播放将会产生大量的流量消耗,大量的网络流量给核心网和接入网带来了巨大的带宽压力。为了缓解网络容量需求爆炸式的增长,可缓存的机会性协作MIMO框架应运而生。它可以改变无线网络的拓扑结构,有效减小用户反复请求热门资源所产生的带宽消耗。从而减轻网络负担提高用户的服务质量。本文研究了一种可缓存的机会性协作MIMO框架。通过在中继配备缓存并将一部分视频文件预先存放在缓存中,然后利用协作MIMO将视频文件传输给用户,这样可以有效节省系统带宽。首先在两个时间尺度上讨论了系统花费,并将问题分解成短期的功率控制和长期的缓存控制两个子问题。然后研究了一个容许的功率控制策略,并利用近似贝尔曼方程求解功率控制问题,证明了在相同的发射功率下该控制策略可以提供更好的视频播放性能。接下来推导出缓存优化问题的近似表达式,并研究了如何用随机次梯度算法求解这个优化问题,同时提出了遗传算法进行缓存优化。然后,对用户终端缓冲区缓冲数据的队列动态和视频播放性能指标进行分析。用队列缩放的方法求得各个性能指标的封闭形式表达式。对比了在最大距离可分码缓存策略和普通缓存策略下的视频播放性能。并研究了注水法和部分信道倒置法缓存控制策略对平均发射功率,缓存溢出概率的影响。最后通过仿真对比了遗传算法和随机次梯度算法对系统花费的影响;并仿真分析了不同缓冲区阈值对缓存频率和缓存延迟的影响。
[Abstract]:With the development of science and technology, the performance of wireless system is required more and more. Mobile users also put forward higher requirements for the transmission rate of video data and the quality of video playback. At the same time, the user terminal video playback will produce a large amount of traffic consumption, a large number of network traffic to the core network and access network brings huge bandwidth pressure. In order to alleviate the explosive growth of network capacity, a caching opportunistic cooperative MIMO framework emerges as the times require. It can change the topology of wireless network and reduce the bandwidth consumption caused by users repeatedly requesting hot resources. Thus lighten the network burden and improve the service quality of users. In this paper, a caching opportunistic cooperative MIMO framework is studied. By providing buffer in relay and storing some video files in cache, and then transferring video files to users by cooperative MIMO, the system bandwidth can be saved effectively. First, the system cost is discussed on two time scales, and the problem is decomposed into two sub-problems: short-term power control and long-term buffer control. Then an allowable power control strategy is studied and the approximate Berman equation is used to solve the power control problem. It is proved that the control strategy can provide better video playback performance under the same transmit power. Then the approximate expression of the buffer optimization problem is derived, and how to solve the optimization problem by the stochastic subgradient algorithm is studied. At the same time, a genetic algorithm is proposed to optimize the cache. Then, the queue dynamics and video playback performance of buffer data in user terminal are analyzed. The closed form expression of each performance index is obtained by queue scaling method. The video playback performance under the maximum distance divisible code cache strategy and the common cache strategy is compared. The effect of buffer control strategy of water injection and partial channel inversion on average transmit power and buffer overflow probability is studied. Finally, the effects of genetic algorithm and stochastic sub-gradient algorithm on system cost are compared, and the effects of different buffer thresholds on buffer frequency and buffer delay are analyzed.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN919.3

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