An improved coded caching scheme for partially cooperative D2D networks

A model of device-to-device (D2D) coded caching in which only a subset of users transmit information during the D2D transmission process was recently introduced. Such networks are referred to as partially cooperative D2D networks. Tebbi and Sung proposed a coded caching achievability scheme for such networks that enables all users to obtain their respective file demands. This is done by forming user sets and employing some of the transmitting users to compensate for the non-transmitting users in each such user set. In this paper, we show that this approach is sub-optimal. In particular, we show that by forming groups of such user sets that satisfy certain properties, it is possible to exploit additional coding opportunities across all the user sets in that group that are not exploited in the previously proposed scheme. We also show how to construct such groups and characterize the resulting improvement in the device-to-device transmission rate.