Device-to-device coded caching with heterogeneous cache sizes

This paper considers a device-to-device (D2D) coded caching system where the users have differing cache sizes. During low traffic hours, the server places subsets of the files at the users' cache memories, in a manner that enables serving the users' requests via D2D transmissions during peak traffic hours. The objective is to jointly design the users' cache contents and the D2D transmissions in order to minimize the D2D delivery load. In particular, we seek to identify the optimal uncoded placement and linear delivery schemes. We propose a novel lower bound on the D2D delivery load under uncoded placement, which enables us to explicitly characterize the minimum D2D delivery load under uncoded placement for several cases of interest.