隨著第五代行動通訊網路的蓬勃發展，不論是大型場所中行動用戶的通訊品質，抑或是穿梭於城市中的車輛之間的即時通訊，生活中處處都和行動網路密不可分。在人潮眾多的大型場所，例如演唱會和體育場，安裝小型基地台是現今的趨勢。小型基地台可以針對不同的應用及場景部署不同的網路架構與需求，進而提升整體網路效率。而車載隨意行動網路是第五代行動通訊技術的應用之一，車輛、交通設施以及路側單元為車載隨意行動網路中的節點。節點之間可以互相傳遞訊息，以提供道路安全、導航與其他道路服務，讓用路人能獲得更便利及安全的交通環境。

然而，近年來隨著行動裝置的大量增加，再加上行動網路數據流量的增長，導致以低延遲、低傳輸量傳遞資料成為一項重要且具有挑戰性的議題。本論文主要探討行動網路中資料傳輸的延遲與冗餘。首先是如何降低使用者下載檔案時的傳輸延遲，以提升服務品質。再者，對於緊急訊息的傳播，探討如何避免快速廣播訊息時產生過多的冗餘傳輸。

為了達成低延遲需求，本論文針對不同的使用者移動模式分別採取不同的協作式快取分群方式，搭配次優的內容放置演算法，提出兩套策略(稱為SFMRD及 MVP)，優化快取的使用率並降低下載檔案的延遲時間。此外，由於傳統的謠言傳播演算法(Gossip algorithm)在傳播時產生太多冗餘的傳輸，本論文基於謠言傳播演算法提出一套記錄節點資訊的傳播演算法(稱為PPRL)，使車載網路的節點能夠減少在傳播時所產生的冗餘訊息。

針對上述的議題，本論文透過模擬實驗來觀察成效。與相關方法比較之下，結果顯示使用者的移動範圍在單一基地台的情況下，SFMRD能降低至少5.81%的平均檔案下載傳輸延遲。而當使用者為行進中之車輛時，MVP能增加至少25.5%從路側單元快取下載的檔案量。另外，PPRL在傳播訊息時，相比現有方法最少能減少9.2%的冗餘傳輸訊息量。

With the vigorous development of the fifth generation mobile networks (5G), life has become inseparable from mobile networks, such as the communication of numerous mobile users in large venues or the communication between vehicles driving in the city. Installing small cell base stations (SBSs) in large venues, such as concert halls or stadiums, is a current trend. By deploying SBSs, different network architectures can be used for various applications and scenarios to improve overall network efficiency. Besides, the vehicular ad hoc network (VANET) is one of the applications in 5G. The VANET consists of vehicles, traffic facilities, and roadside units (RSUs) as network nodes. Messages can be transmitted between nodes to provide road safety, navigation, and other on-road services so that occupants have a more convenient and safe traffic environment.

However, in recent years, the number of mobile devices has increased dramatically, which resulted in a large increment in mobile data traffic. How to transmit data with low latency and a low number of transmissions has become an important but challenging issue. In this dissertation, we investigate ways to reduce download latency for users with different movement patterns and redundant transmissions for emergency message broadcasts.

To better utilize the limited cache memory and achieve low transmission latency for different user mobility, we propose two strategies (called SFMRD and MVP) with different clustering algorithms and a suboptimal content placement algorithm. In addition, when propagating messages, the gossip algorithm is considered to generate too many redundant transmissions. Therefore, we propose an improved gossip algorithm (called PPRL) with a mechanism that records node information, which can reduce the number of redundant transmissions when disseminating messages.

Compared with related methods by conducting the simulation experiments, the results show that the SFMRD can reduce the average download delay by at least 5.81% when the user's moving area is within a single SBS. The MVP can increase the average file volume downloaded by the moving vehicles from the RSUs by at least 25.5%. For message dissemination, PPRL can reduce the number of redundant transmissions by at least 9.2% compared to the existing methods.

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