Content Placement in Cache Networks Using Graph Coloring

Abstract

Small cell densification is one of the effective ideas addressing the demand for higher capacity in cellular networks. The major problem in such networks is the limited capacity of wireless backhaul links. Caching the popular files in the memories of small cell base stations (SBSs) is an effective solution to this problem. One of the main challenges in caching is choosing the files to be stored in the memory of SBSs, especially when some SBSs have overlapped coverage. In this article, we propose a new caching scheme by exploiting the concept of graph coloring. To this end, we model the network scenario by a graph. This graph is divided into four subgraphs, i.e., placement, access, SBS, and delivery graphs. Through some modifications to the SBS graph, we convert it to a graph that can be colored. Then, we propose a graph coloring-based scheme to cache the popular files. We also derive a lower-bound for the hit rate improvement of our scheme compared to the conventional scheme which caches the most popular files anywhere. We evaluate the performance of our proposed scheme through simulations. Our results show that by employing the proposed scheme in a typical network, the load on the backhaul links is reduced significantly in average compared to the conventional scheme and some previously proposed schemes.