終端直通蜂窩系統(tǒng)中的邊緣緩存技術
發(fā)布時間：2018-09-01 08:06
【摘要】：隨著蜂窩數(shù)據(jù)業(yè)務和流量迅速增長,蜂窩網(wǎng)絡面臨的數(shù)據(jù)流量壓力越來越大。受網(wǎng)絡資源的限制,傳統(tǒng)的增加蜂窩系統(tǒng)容量的方法如縮小小區(qū)范圍、增加可用頻譜等,越發(fā)難以為繼。如何對蜂窩網(wǎng)絡系統(tǒng)進行流量卸載成為學界和業(yè)界關注的重點。D2D通信技術支持兩個終端用戶直接進行通信,相比于傳統(tǒng)的蜂窩通信,D2D通信可以減輕蜂窩基站的負擔。此外,邊緣緩存是實現(xiàn)流量本地化、進行流量卸載的有效方法。將D2D通信與緩存相結合,使得蜂窩網(wǎng)絡中緩存在終端的數(shù)據(jù)不僅可以滿足終端自身需求,也可以通過D2D通信與鄰近終端共享,這樣將大大減輕網(wǎng)絡流量負載。因此研究蜂窩系統(tǒng)中基于D2D通信的終端緩存策略以最大化系統(tǒng)流量卸載性能具有重要的理論意義和實用價值。首先,本論文對蜂窩系統(tǒng)中基于D2D通信的終端被動緩存的流量卸載性能進行了分析。當終端緩存有文件時,終端的文件請求可通過自身緩存或者基于終端間D2D通信的文件共享滿足。本論文對兩種不同的終端移動場景下終端緩存的流量卸載性能進行了研究。在靜態(tài)網(wǎng)絡中,終端間的拓撲關系可視作是穩(wěn)定的,因此可以對各D2D鏈路的通信進行調(diào)度,但D2D鏈路的傳輸需求在不同時刻是變化的,本論文基于最大加權獨立集模型提出了一個啟發(fā)式算法來獲得系統(tǒng)流量卸載比率。在高移動性網(wǎng)絡中,終端間不存在穩(wěn)定的拓撲關系,本論文將移動終端位置建模為泊松點過程,并通過隨機幾何分析得到系統(tǒng)流量卸載比率。接下來,本論文研究了蜂窩系統(tǒng)中基于D2D通信的終端主動緩存策略。終端可調(diào)整自身緩存內(nèi)容以最大化系統(tǒng)流量卸載量�？紤]到移動終端有不同的移動性和緩存空間、需要緩存的文件有不同的大小和流行程度這些因素,問題建模為一個組合優(yōu)化問題并被證明是NP難題。由于終端和文件的數(shù)目較大,通過指數(shù)級復雜度獲得最優(yōu)解并不實際。本論文提出了一個低復雜度分布式終端間緩存調(diào)整算法來實現(xiàn)移動終端相遇時的緩存內(nèi)容調(diào)整,并理論上推導了該算法能達到的性能界�；诮K端間緩存調(diào)整算法,本論文提出了需要基站提供輔助信息的基站輔助流量卸載算法,為了減少基站輔助帶來的控制信息負荷,進一步提出了由終端進行參數(shù)估計的完全分布式流量卸載算法。最后,本論文對基于D2D協(xié)作傳輸?shù)膫鬏敳呗院徒K端緩存策略進行了聯(lián)合優(yōu)化設計。多個終端可以以D2D協(xié)作傳輸?shù)姆绞较蛲唤K端傳輸同一文件以提高通信質量,對抗衰落,結合終端緩存策略進一步系統(tǒng)提升流量卸載性能。本論文將協(xié)作傳輸策略和終端緩存策略的聯(lián)合優(yōu)化問題分解為求解傳輸策略的子問題和求解緩存策略的主問題。本論文將傳輸策略子問題轉化為有限步MDP問題,給出了該MDP問題貝爾曼最優(yōu)性方程,通過求解.貝爾曼方程提出了系統(tǒng)傳輸策略進行鏈路選擇;得到系統(tǒng)傳輸策略后,以梯度投影法為工具,對緩存策略主問題進行求解,得到了系統(tǒng)緩存策略。
[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.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN929.5
，
本文編號：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.
【學位授予單位】：浙江大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN929.5
，
本文編號：2216600
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