Exploiting Mobility in Cache-Assisted D2D Networks: Performance Analysis and Optimization

TL;DR

This paper analyzes how user mobility impacts cache-assisted D2D networks, deriving a model for data offloading that increases with user speed and proposing a mobility-aware caching strategy to enhance performance.

Contribution

It introduces a novel analytical model considering contact durations and develops a mobility-aware caching strategy to optimize data offloading in D2D networks.

Findings

Data offloading ratio increases with user moving speed.

Mobility-aware caching improves data delivery performance.

Contact duration information is crucial for effective cache placement.

Abstract

Caching popular content at mobile devices, accompanied by device-to-device (D2D) communications, is one promising technology for effective mobile content delivery. User mobility is an important factor when investigating such networks, which unfortunately was largely ignored in most previous works. Preliminary studies have been carried out, but the effect of mobility on the caching performance has not been fully understood. In this paper, by explicitly considering users' contact and inter-contact durations via an alternating renewal process, we first investigate the effect of mobility with a given cache placement. A tractable expression of the data offloading ratio, i.e., the proportion of requested data that can be delivered via D2D links, is derived, which is proved to be increasing with the user moving speed. The analytical results are then used to develop an effective mobility-aware caching strategy to maximize the data offloading ratio. Simulation results are provided to confirm the accuracy of the analytical results and also validate the effect of user mobility. Performance gains of the proposed mobility-aware caching strategy are demonstrated with both stochastic models and real-life data sets. It is observed that the information of the contact durations is critical to design cache placement, especially when they are relatively short or comparable to the inter-contact durations.