Repair Scheduling in Wireless Distributed Storage with D2D Communication

TL;DR

This paper analyzes how repair scheduling in wireless distributed storage systems affects communication costs, showing that repair frequency and code choice are crucial for cost efficiency in D2D content retrieval.

Contribution

It introduces a model for repair scheduling in wireless distributed storage with D2D communication, deriving cost expressions and analyzing the impact of repair intervals and coding schemes.

Findings

Frequent repairs reduce overall communication costs.

Different codes require different repair frequencies for optimal performance.

Instantaneous repair is not always the most cost-effective approach.

Abstract

We consider distributed storage (DS) for a wireless network where mobile devices arrive and depart according to a Poisson random process. Content is stored in a number of mobile devices, using an erasure correcting code. When requesting a piece of content, a user retrieves the content from the mobile devices using device-to-device communication or, if not possible, from the base station (BS), at the expense of a higher communication cost. We consider the repair problem when a device that stores data leaves the network. In particular, we introduce a repair scheduling where repair is performed (from storage devices or the BS) periodically. We derive analytical expressions for the overall communication cost of repair and download as a function of the repair interval. We illustrate the analysis by giving results for maximum distance separable codes and regenerating codes. Our results indicate that DS can reduce the overall communication cost with respect to the case where content is only downloaded from the BS, provided that repairs are performed frequently enough. The required repair frequency depends on the code used for storage and the network parameters. In particular, minimum bandwidth regenerating codes require very frequent repairs, while maximum distance separable codes give better performance if repair is performed less frequently. We also show that instantaneous repair is not always optimal.