An Efficient Online Cache Replacement Algorithm for 5G Networks

In recent years, 5G cellular networks utilization has rapidly increased and is expected to grow even more in the near future. This will put the current cellular networks operators in a challenge to overcome the network's limits to satisfy the increasing mobile data traffic and the proliferation of user demands in deploying mobile applications. The deployment of cache-enabled small base stations (Femtocells) is a promising solution to reduce the backhaul traffic loading and the file-access latency and therefore decrease the cellular network operational costs. Due to the limited cache capacity when compared with the number of files that can be requested by users, in this paper, we formulate the problem of minimizing the cost paid by the cellular network while satisfying the cache capacity as an integer linear program (ILP). Due to the NP-completeness of the ILP formulation and the difficulty of obtaining the file request sequence apriori in real-life scenarios, we propose an online algorithm that decides which file to remove from cache in order to allocate capacity to the newly-requested file. The algorithm works on a per-request basis and does not require the knowledge of the file request sequence in advance. We prove that for a cache that can store up to k files, the algorithm achieves a competitive ratio of O(log(k)), which is the best competitive ratio achieved by any online algorithm as shown in the literature. The simulations conducted considering a single cache show that while the proposed algorithm achieves a similar hit ratio compared with widely-used replacement schemes, it can reduce the cost of the cellular network by 25%.