Distributed Coded Caching Based Video Multicast Technology

As a newly emerging technology, coded caching outperforms the traditional caching in terms of both the delivery performance. More specifically, coded caching can not only provide local caching gain, but also the global caching gain, where both gains are originated from the joint optimization of the content disseminated among multiple users and the coded transmission scheduling, such that the possible maximal number of different users’requests can be met in one coded multicast transmission by the server station. In the coded multicast transmission system, when users request files from the server, the server will try to sort out the best coded scheme to linearly multiplex different files together such that each individual user can successfully restore its requested one from the received coded packet and its own local pre-stored content. By doing so, we can realize the so called one transmission, multiple response mechanism.In this paper, the background and research significance of the coded caching scheme will be firstly reviewed. The Ali-Niesen coded caching design and the placement-delivery array (PDA) formulation will be introduced to show the state of the art in the recently emerging coded caching design issue. Since few coded caching design consider to support the different service priority levels, by following the PDA idea, the modified PDA based coded caching design is proposed to guarantee that the users with higher priority level can be served earlier than the users with less priority level.In order to verify the coded caching design, a video multicast platform is developed, wherein the system comprises of six users, one server. It is assumed that there are in total 10 different files at the server, and each file can be partitioned into four segements, and 50%of each file will be pre-stored at all six users. In this thesis, we use the time duration that all requested files are delivered by the server to assess the transmission efficiency of the coded caching based multicast system over the traditional unicast system. In order to deal with the packet loss issue in wireless environment, fountain code is also employed in our system. And our experiment analysis shows that, the use of the coded caching based multicast can significantly reduce the transmission latency when compared to the traditional unicast system in wired network. While the introduction of fountain code in the coded caching multicast scheme can effectively cope with the packet loss issue, even in wireless environment with up to 20%-30% packet loss rate. We use the service order to assess the priority differentiation capability, our experiment results show that, when considering different user priority levels in the coded caching design, the user with higher priority level can always be served earlier that the user with less priority levelThe analysis in this thesis disclosed that, the joint use of the modified coded caching design with user priority level support and the fountain code provides efficient and feasible technical solution to the multicast transmission scheme in wireless network environment.