Throughput–Outage Analysis of Cache-Aided Wireless Multi-Hop D2D Networks

Cache-aided wireless device-to-device (D2D) networks have demonstrated promising performance improvement for video distribution compared to conventional distribution methods. Understanding the fundamental scaling behavior of such networks is thus importance. Recently, based on real-world data, it has been observed that the popularity distribution should be modeled by a Mandelbrot-Zipf (MZipf) distribution, instead of the common Zipf distribution. We thus in this work investigate the throughput-outage performance for cache-aided wireless D2D network adopting multi-hop communications, with the MZipf popularity distribution for file requests and Poisson point process for user distribution. Considering the case that Zipf factor is larger than one, we first propose an achievable content caching and delivery scheme and analyze its performance. Then, by showing that the achievable performance is tight to the proposed outer bound, we show that an optimal scaling law for cache-aided wireless multi-hop D2D networks is obtained.

I. Introduction

Over the last years, progress of semiconductor technology has made memory one of the cheapest hardware resources. Accordingly, caching at the wireless edge has emerged as a promising approach for significantly improving the efficiency and quality of video distribution [2]. The idea of caching is to trade cheap memory resources for expensive bandwidth resources by caching video files close to the prospective users. This principle, combined with the asynchronous content reuse and concentrated popularity that are general characteristics of video requests [2], has rendered caching at the wireless edge a widely explored method for video distribution [3].