Age-Constrained Content Access Strategy in D2D-Assisted Wireless Caching Networks

Device-to-device (D2D) assisted wireless caching network enables users to obtain requested contents with lower energy consumption, by caching popular files in the memory of end users. However, the freshness of information retrieved from other end users is not taken into consideration in previous researches. Age-of-Information (AoI) is proposed as a performance metric to evaluate the freshness of a piece of information by counting the time elapsed since its generation. In this paper, we propose an age-constrained content access strategy in D2D-assisted wireless caching systems with the aim of achieving the best energy efficiency. We formulate a Markov decision process (MDP) problem by considering network state and freshness of requested content. The formulated problem falls in the form of a nonlinear integer program. To solve the problem efficiently, we reformulate the problem by approximating the expected energy consumption of future time slots into an age-related function of the next slot. Through performance evaluation, we show that the performance of our proposed strategy is competitive in terms of average age of requested contents and network-wide energy consumption, when compared with traditional content access strategies.