Content Pushing Based on Physical Layer Multicasting and Request Delay Information

For content-centric wireless networks, pushing and proactive caching hold the promise of greatly improving system throughput in the future. However, the throughput gains obtained from these techniques are limited by the energy of the base station and the buffer size of the receivers. To make full use of this energy and these buffers, this paper presents a Joint Pushing and Caching (JPC) method for physical layer multicasting systems, where the request delay information (RDI) is exploited in noncausal, statistical, and causal form. In JPC, the content items pushed by the base station and removed from the buffers of receivers in each timeslot are jointly determined. With noncausal or statistical RDI, an offline policy is presented by formulating and solving an optimization problem in order to maximize the effective throughput. With causal RDI, an online policy is presented to further enhance the effective throughput with little signalling overhead. Causal feedback of RDI is found to bring a substantial throughput gain.