On the Placement Delivery Array Design for Coded Caching Scheme in D2D Networks

TL;DR

This paper introduces a new array-based framework called D2D placement delivery array (DPDA) to optimize coded caching in D2D networks, achieving lower rate and packet number than previous schemes.

Contribution

It characterizes coded caching schemes with DPDAs, derives lower bounds on rate and packet number, and constructs schemes that meet these bounds for improved efficiency.

Findings

DPDA characterizes coded caching schemes for D2D networks.

Lower bounds on rate and packet number are established.

New schemes meet the bounds, reducing rate and packet size.

Abstract

The coded caching scheme is an efficient technique as a solution to reduce the wireless network burden during the peak times in a Device-to-Device (D2D in short) communications. In a coded caching scheme, each file block should be divided into $F$ packets. It is meaningful to design a coded caching scheme with the rate and $F$ as small as possible, especially in the practice for D2D network. In this paper we first characterize coded caching scheme for D2D network by a simple array called D2D placement delivery array (DPDA in shot). Consequently some coded caching scheme for D2D network can be discussed by means of an appropriate DPDA. Secondly we derive the lower bounds on the rate and $F$ of a DPDA. According these two lower bounds, we show that the previously known determined scheme proposed by Ji et al., (IEEE Trans. Inform. Theory, 62(2): 849-869,2016) reaches our lower bound on the rate, but does not meet the lower bound on $F$ for some parameters. Finally for these parameters, we construct three classes of DPDAs which meet our two lower bounds. Based on these DPDAs, three classes of coded caching scheme with low rate and lower $F$ are obtained for D2D network.