Mixed Timescale Online PHY Caching and Content Delivery for Content-Centric Wireless Networks

In content-centric wireless networks, physical layer (PHY) caching has been proposed to exploit the dynamic side information induced by base station (BS) cache to support Coordinated Multi-Point (CoMP) and achieve huge capacity gain. The performance of PHY caching depends heavily on the cache content placement algorithm. In existing algorithms, the cache content placement is adaptive to the long-term popularity distribution in an offline manner. We propose an online PHY caching framework based on the concept of virtual interest packet (VIP) in a virtual network. The VIP captures microscopic spatial and temporary popularity variations, and thus the VIP-based online PHY caching can adapt the cached content to the microscopic popularity variations to fully exploit the benefits of PHY caching. The joint optimization of online caching and content delivery is formulated as a mixed timescale drift minimization problem and a low complexity algorithm is proposed to find the optimal solution. Simulations show that the proposed solution achieves large gain over existing solutions.