A Light-Weight Cooperative Caching Strategy by D2D Content Sharing

Mobile Internet traffic has been a vast amount by the Video-on-Demand (VoD) services. To reduce the enormous traffic to a mobile Base Station (BS), some techniques are proposed for offloading traffic among devices using Device-to-Device (D2D) direct communication. Several studies try to improve the offloading ratio by cooperating multiple devices. However, these require a long computational time while it degrades the performance from the environmental changes in devices' circumstances. This paper proposes a light-weight method to construct a mobile cooperative cache by assigning group IDs both to devices and contents. Each device selects its cache contents by checking the match of its own group ID and content group ID. Such scheme efficiently reduces a load of BS by distributing various contents among devices without much deployment of BSs and computational cost. Moreover, we utilize a D2D overhearing technology to accelerate the contents deployment. Since the D2D overhearing could increase traffic by flushing and homogenizing cached contents, we also propose a prioritized cache algorithm to keep the variety of contents by enduring the flood of the D2D overhear. Evaluation results in a stadium demonstrate that our group-based caching strategy reduces BS's traffic load up to 81.7% as well as a fast content distribution by a synergy effect of the D2D overhearing and the prioritized caching.