This paper studies the fundamental limits of caching in a network with two receivers and two files generated by a two-component discrete memoryless source with arbitrary joint distribution. Each receiver is equipped with a cache of equal capacity, and the requested files are delivered over a shared errorfree broadcast link. First, a lower bound on the optimal peak rate-memory trade-off is provided. Then, in order to leverage the correlation among the library files to alleviate the load over the shared link, a two-step correlation-aware cache-aided coded multicast (CACM) scheme is proposed. The first step uses Gray-Wyner source coding to represent the library via one common and two private descriptions, such that a second correlationunaware multiple-request CACM step can exploit the additional coded multicast opportunities that arise. It is shown that the rate achieved by the proposed two-step scheme matches the lower bound for a significant memory regime and it is within half of the conditional entropy for all other memory values.
It is shown in REF that this strategy is optimal for a large memory regime, while the gap to optimality is bounded for other memory values.
Rate-memory trade-off for the two-user broadcast caching network with correlated sources
2017 IEEE International Symposium on Information Theory (ISIT)
2017 IEEE International Symposium on Information Theory (ISIT)
Computer Science Mathematics