Loss-aware adaptive caching scheme for device-to-device communications

In current research of device-to-device (D2D) caching strategies, when terminals request and receive files within the transmission range, the effect of file redundancy and idle loss rate of the cache in terminals are rarely considered. In this study, the authors establish a motion and the transfer model of D2D terminals, and define a loss function considering cache idle loss and file redundancy. Then the relationship between the cache size and the number of terminals is analysed, and the optimal cache size is calculated according to the loss function. Through the analysis, the authors can see that the performance of the D2D caching network is almost constant when the product of the buffer size and the number of terminals is constant. Therefore, inspired by the above analysis and results, the authors devise an adaptive caching strategy, which determines the file caching method according to the comparison of the actual size of the terminal cache and the optimal cache size with respect to the loss function. Simulation results indicate that, compared with other caching schemes, the proposed adaptive strategy yields a significantly higher cache-hitting rate and less delay.