iCacheOS: In-RAN Caches Orchestration Strategy through Content Joint Wireless and Backhaul Routing in Small-Cell Networks

Distributed caching in the radio access network (RAN) has been a common approach for improving QoE per- ceived by mobile users and reducing backhaul traffic load. In this paper, we focus on the problem of cooperative and online searching and routing for content objects cached according to their local popularity in small- cell networks (SCNs), considering practical issues of implementation complexity and content prefer- ence diversity, which is different from prior arts mainly focusing on global content caching optimization with pre-knowledge of content requests and/or mobility pattern of users. We propose an in-RAN caches orchestration strategy (named as iCacheOS), where cooperative content searching and sharing is achieved through content joint wireless and backhaul routing algorithm. Specifically, the in-RAN caches orchestration framework is designed under the software defined networking inspired system architecture consisting of the central orchestrator and in-RAN caches with the local routing function; the content joint wireless and backhaul routing problem is constructed with the objective to minimizing the SCN content transmission delay, which is proved to be a quadratic assignment problem (QAP); to assure high computation efficiency, a joint dimension reduction, Lagrangian relaxation and accelerated branch and bound algorithm is pro- posed. Numerical results reveal that iCacheOS can significantly reduce the content transmission delay and outgoing backhaul traffic load, and is more robust to content preference diversities, in comparison with other strategies.