Research On D2D Technology For Wireless Caching

Wireless video service has been one of the main drivers of mobile data traffic. This fast growth in traffic has been imposing a significant burden on the current wireless communication systems, especially during the peak periods. However, traditional communication technologies do not exploit the key property of video, i.e., asynchronous content reuse, which means a few popular files are requested by a major users during a period of time. With the improvement of computing ability and storage capacity, introducing caching to wireless communication systems has attracted more and more attention, especially D2D(Device-to-Device) caching networks. This was proposed as a favorable approach to handle the explosive growth of wireless video services, and provide a new direction for the future development of wireless communication.In D2 D caching networks, the popular video files can be pre-download in user’s cache during the off-peak hours. With the help of caching, the user can obtain the requested file from its own cache or the caches of the adjacent users by using D2 D transmission, instead of downloading from the base station. This can not only significantly reduce the system load, air congestion, latency and energy consumption, but also provide users with a better service experience.This thesis studies the key technology of D2 D caching networks as follows:Firstly,we provide an extensive review of available literature on wireless caching networks. Moreover, we carry out the classification and summarization.Secondly, we study the optimal caching strategy for D2 D caching networks in the caching phase. Under the condition of limited caching space, we formulate the optimal caching problem aimed at maximizing the hitting probability and develop two sub-optimal algorithms with low complexity, i.e., cut-off random caching scheme and segment-based random caching scheme. Simulation results show that the performances of proposed schemes are closed to the optimal one.Thirdly, we study the scheduling algorithm of the D2 D caching networks in the delivery phase. Under the condition of target signal to interference plus noise ratio(SINR), we formulate the scheduling problem aimed at maximizing the activated D2 D links. Then, we divide this problem into two sub-problems, i.e., pairing problem of potential links and activating problem of pairing links. We also develop the solutions for the two sub-problems, respectively. Simulation results show that the proposed scheduling algorithm can achieve a better performance than the existing algorithms.Finally, we do research on energy efficiency problem of the D2 D caching networks while considering the activating probability of D2 D links in the caching phase. Under limited caching capacity, we formulate the optimal caching strategy for minimizing the energy consumption and provide a sub-optimal solution, i.e., two-segments random caching scheme. Numerical results show that introducing caching into D2 D networks can significantly reduce the energy consumption. Furthermore, the proposed algorithm can obtain the similar performance with the optimal one.