Coverage Analysis for Multi-Request Association Model (MRAM) in a Caching Ultra-Dense Network

Abstract

This paper examines the impact of multiple requests based user association model on the performance of ultra-dense small cell network. We consider a cache-enabled small cell network where popular files are cached in different small cells according to the spatial popularity of files. Unlike traditional models, where a user sends requests to a single nearby small cell, we propose a multi-request based user association model (MRAM). In this model, a user selects multiple small cells in its vicinity, referred to as neighbors, for sending file requests. This subset of neighbors search the requested file simultaneously, in order to provide it to the user at the small cell level. This results in an improved coverage probability, which increases the cache hit ratio, eventually alleviating the backhaul congestion. We further exploit coverage probability by considering different coverage patterns and derive closed-form expressions based on these coverage scenarios. We concretely demonstrate that the performance of such a multi-request model is improved with user's movement in different regions. Gains obtained from MRAM are quantified in terms of coverage probability through numerical simulations as well as network simulations.