MDS-Coded Distributed Caching for Low Delay Wireless Content Delivery

We investigate the use of maximum distance separable (MDS) codes to cache popular content to reduce the download delay of wireless content delivery. In particular, we consider a cellular system, where popular files are cached in a distributed fashion in a limited number of the mobile devices using an MDS code and can be downloaded from them using device-to-device (D2D) communication. The base station controls the D2D communication and assists the requests that cannot be fully satisfied by the distributed caching (DC) network by providing the missing data. We consider a network model, where the cell is divided into clusters, where D2D links can be activated. We derive an analytical expression for the delay incurred in downloading content from the wireless network assuming that devices roam in and out of clusters according to a Poisson random process. Our analysis allows to identify the parameters of the wireless network that mostly affect the performance and to compare different caching strategies in terms of delay. We show that DC using MDS codes can dramatically reduce the download delay with respect to the scenario where content is always downloaded from the base station and to the case of uncoded DC.