终端直通蜂窝系统中的边缘缓存技术
发布时间：2018-09-01 08:06
【摘要】：随着蜂窝数据业务和流量迅速增长,蜂窝网络面临的数据流量压力越来越大。受网络资源的限制,传统的增加蜂窝系统容量的方法如缩小小区范围、增加可用频谱等,越发难以为继。如何对蜂窝网络系统进行流量卸载成为学界和业界关注的重点。D2D通信技术支持两个终端用户直接进行通信,相比于传统的蜂窝通信,D2D通信可以减轻蜂窝基站的负担。此外,边缘缓存是实现流量本地化、进行流量卸载的有效方法。将D2D通信与缓存相结合,使得蜂窝网络中缓存在终端的数据不仅可以满足终端自身需求,也可以通过D2D通信与邻近终端共享,这样将大大减轻网络流量负载。因此研究蜂窝系统中基于D2D通信的终端缓存策略以最大化系统流量卸载性能具有重要的理论意义和实用价值。首先,本论文对蜂窝系统中基于D2D通信的终端被动缓存的流量卸载性能进行了分析。当终端缓存有文件时,终端的文件请求可通过自身缓存或者基于终端间D2D通信的文件共享满足。本论文对两种不同的终端移动场景下终端缓存的流量卸载性能进行了研究。在静态网络中,终端间的拓扑关系可视作是稳定的,因此可以对各D2D链路的通信进行调度,但D2D链路的传输需求在不同时刻是变化的,本论文基于最大加权独立集模型提出了一个启发式算法来获得系统流量卸载比率。在高移动性网络中,终端间不存在稳定的拓扑关系,本论文将移动终端位置建模为泊松点过程,并通过随机几何分析得到系统流量卸载比率。接下来,本论文研究了蜂窝系统中基于D2D通信的终端主动缓存策略。终端可调整自身缓存内容以最大化系统流量卸载量。考虑到移动终端有不同的移动性和缓存空间、需要缓存的文件有不同的大小和流行程度这些因素,问题建模为一个组合优化问题并被证明是NP难题。由于终端和文件的数目较大,通过指数级复杂度获得最优解并不实际。本论文提出了一个低复杂度分布式终端间缓存调整算法来实现移动终端相遇时的缓存内容调整,并理论上推导了该算法能达到的性能界。基于终端间缓存调整算法,本论文提出了需要基站提供辅助信息的基站辅助流量卸载算法,为了减少基站辅助带来的控制信息负荷,进一步提出了由终端进行参数估计的完全分布式流量卸载算法。最后,本论文对基于D2D协作传输的传输策略和终端缓存策略进行了联合优化设计。多个终端可以以D2D协作传输的方式向同一终端传输同一文件以提高通信质量,对抗衰落,结合终端缓存策略进一步系统提升流量卸载性能。本论文将协作传输策略和终端缓存策略的联合优化问题分解为求解传输策略的子问题和求解缓存策略的主问题。本论文将传输策略子问题转化为有限步MDP问题,给出了该MDP问题贝尔曼最优性方程,通过求解.贝尔曼方程提出了系统传输策略进行链路选择;得到系统传输策略后,以梯度投影法为工具,对缓存策略主问题进行求解,得到了系统缓存策略。
[Abstract]:With the rapid growth of cellular data services and traffic, the pressure of data traffic on cellular networks is increasing. Due to the limitation of network resources, the traditional methods to increase the capacity of cellular systems, such as narrowing the cell size and increasing the available spectrum, are becoming more and more difficult to sustain. In addition, edge caching is an effective way to localize traffic and unload traffic. By combining D2D communication with caching, the data cached at the end of the cellular network is cached. It can not only meet the needs of the terminal itself, but also share with the adjacent terminals through D2D communication, which will greatly reduce the network traffic load. Therefore, it is of great theoretical significance and practical value to study the terminal buffer strategy based on D2D communication in cellular system to maximize the system traffic unloading performance. The unloading performance of terminal passive cache based on D2D communication is analyzed. When the terminal caches a file, the file request of the terminal can be satisfied by its own cache or file sharing based on D2D communication between terminals. In the state network, the topological relationship between terminals can be regarded as stable, so the communication of each D2D link can be scheduled. But the transmission demand of the D2D link varies at different times. Based on the maximum weighted independent set model, a heuristic algorithm is proposed to obtain the system traffic unload ratio. There is no stable topological relationship between terminals. In this paper, the location of mobile terminals is modeled as a Poisson point process, and the unloading rate of system traffic is obtained by stochastic geometric analysis. Next, the terminal active caching strategy based on D2D communication in cellular systems is studied. Considering that the mobile terminal has different mobility and cache space, the size and popularity of the files that need to be cached are different, the problem is modeled as a combinatorial optimization problem and proved to be a NP-hard problem. A low-complexity distributed inter-terminal cache adjustment algorithm is proposed to adjust the cache content when mobile terminals encounter each other, and the performance bound of the algorithm is deduced theoretically. A fully distributed traffic uninstallation algorithm based on terminal parameter estimation is proposed. Finally, a joint optimization design of transmission strategy and terminal caching strategy based on D2D cooperative transmission is carried out. Multiple terminals can transfer the same file to the same terminal by D2D cooperative transmission. This paper decomposes the joint optimization problem of cooperative transmission strategy and terminal cache strategy into the sub-problem of solving transmission strategy and the main problem of solving cache strategy. The Bellman optimality equation of the MDP problem is given, and the system transmission strategy is proposed for link selection by solving the Bellman equation.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5
，
本文编号：2216600
[Abstract]:With the rapid growth of cellular data services and traffic, the pressure of data traffic on cellular networks is increasing. Due to the limitation of network resources, the traditional methods to increase the capacity of cellular systems, such as narrowing the cell size and increasing the available spectrum, are becoming more and more difficult to sustain. In addition, edge caching is an effective way to localize traffic and unload traffic. By combining D2D communication with caching, the data cached at the end of the cellular network is cached. It can not only meet the needs of the terminal itself, but also share with the adjacent terminals through D2D communication, which will greatly reduce the network traffic load. Therefore, it is of great theoretical significance and practical value to study the terminal buffer strategy based on D2D communication in cellular system to maximize the system traffic unloading performance. The unloading performance of terminal passive cache based on D2D communication is analyzed. When the terminal caches a file, the file request of the terminal can be satisfied by its own cache or file sharing based on D2D communication between terminals. In the state network, the topological relationship between terminals can be regarded as stable, so the communication of each D2D link can be scheduled. But the transmission demand of the D2D link varies at different times. Based on the maximum weighted independent set model, a heuristic algorithm is proposed to obtain the system traffic unload ratio. There is no stable topological relationship between terminals. In this paper, the location of mobile terminals is modeled as a Poisson point process, and the unloading rate of system traffic is obtained by stochastic geometric analysis. Next, the terminal active caching strategy based on D2D communication in cellular systems is studied. Considering that the mobile terminal has different mobility and cache space, the size and popularity of the files that need to be cached are different, the problem is modeled as a combinatorial optimization problem and proved to be a NP-hard problem. A low-complexity distributed inter-terminal cache adjustment algorithm is proposed to adjust the cache content when mobile terminals encounter each other, and the performance bound of the algorithm is deduced theoretically. A fully distributed traffic uninstallation algorithm based on terminal parameter estimation is proposed. Finally, a joint optimization design of transmission strategy and terminal caching strategy based on D2D cooperative transmission is carried out. Multiple terminals can transfer the same file to the same terminal by D2D cooperative transmission. This paper decomposes the joint optimization problem of cooperative transmission strategy and terminal cache strategy into the sub-problem of solving transmission strategy and the main problem of solving cache strategy. The Bellman optimality equation of the MDP problem is given, and the system transmission strategy is proposed for link selection by solving the Bellman equation.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5
，
本文编号：2216600
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