Decentralized Coded Caching Without File Splitting

Coded caching is an effective technique to reduce the redundant traffic in wireless networks. The existing coded caching schemes require the splitting of files into a possibly large number of subfiles, i.e., they perform coded subfile caching. Keeping the files intact during the caching process would actually be appealing, broadly speaking because of its simpler implementation. However, little is known about the effectiveness of this coded file caching in reducing the data delivery rate. In this paper, we propose such a file caching scheme that uses a decentralized algorithm for content placement and either a greedy clique cover or an online matching algorithm for the delivery of missing data. We derive approximations to the expected delivery rates of both schemes using the differential equations method, and show them to be tight through concentration analysis and computer simulations. Our numerical results demonstrate that the proposed coded file caching is significantly more effective than uncoded caching in reducing the delivery rate. We, furthermore, show the additional improvement in the performance of the proposed scheme when its application is extended to subfile caching with a small number of subfiles.