Placement delivery array design for coded caching scheme in partially cooperative device-to-device networks

Device-to-device (D2D) communication is a promising technique for next-generation wireless cellular communication systems. This paper studies coded caching in a partially cooperative D2D network, where only a subset of users transmit, while all request files. In all existing partially cooperative D2D coded caching schemes, each file must be divided into subfiles, referred to as the subpacketization level, which grows exponentially with the total number of users. For practical implementations, it is desirable to have schemes with reduced subpacketization levels. We propose an array known as a partially cooperative D2D placement delivery array (PC-DPDA), which describes the placement and delivery phases of a partially cooperative D2D coded caching scheme. Low subpacketization level schemes can be obtained by constructing appropriate PC-DPDAs. The placement delivery array (PDA) was proposed as a tool for designing coded caching schemes for broadcast networks. A wide range of PDA classes has been constructed in the literature. We propose a construction of a PC-DPDA from any given PDA, thereby obtaining several classes of PC-DPDAs. We show that an existing partially cooperative D2D coded caching scheme, which has an advantage over other known schemes in terms of operating memory regime, corresponds to a class of PC-DPDAs.