Mobile coded caching in small cell networks: Algorithm design and performance analysis

Abstract

In coded caching, users cache pieces of files under a specific arrangement so that the server can satisfy their requests simultaneously in the broadcast scenario via eXclusive OR (XOR) operation and therefore reduce the amount of transmission data. However, when users' locations are changing, the uploading of caching information is frequent and extensive that the traffic increase outweighed the traffic reduction that the traditional coded caching achieved. In this paper, we propose mobile coded caching schemes to reduce network traffic in mobility scenarios, which achieve a lower cost on caching information uploading. In the cache placement phase, the proposed scheme first constructs caching patterns, and then assigns the caching patterns to users according to the graph coloring method and four color theorem in our centralized cache placement algorithm or randomly in our decentralized cache placement algorithm. Then users are divided into groups based on their caching patterns. As a benefit, when user movements occur, the types of caching pattern, rather than the whole caching information of which file pieces are cached, are uploaded. In the content delivery phase, XOR coded caching messages are reconstructed. Transmission data volume is derived to measure the performance of the proposed schemes. Numerical results show that the proposed schemes achieve great improvement in traffic offloading.