Proactive Caching in 5G Small Cell Networks

Massive deployment of small-cell base stations (SBSs) is going to play a key role for capacity and coverage enhancements in 5G networks. However, the backhaul for these networks remains one of the important issue to solve. Ideally, the capacity of backhaul has to be in the same order of wireless links in order to avoid bottlenecks in the delivery and sustain huge traffic generated by mobile users, especially due to video streaming and content sharing in social networks. In reality, the deployment of such high-speed backhauls is not straightforward due to its costly nature. Thus, one promising way of tackling this backhaul bottleneck and satisfying users’ demand is to cache the strategic contents at the edge of the network, namely at the SBSs and user terminals (UTs). So far, most of the existing solutions are based on the reactive networking paradigm in which users’ content requests are served immediately upon their arrival or causing outages otherwise. In this chapter, we first provide an overview for recent research in small cell networks (SCNs), and then we explore the novel paradigm of proactive caching in SCNs that leverages the latest developments in storage, context-awareness, and social networking. With this approach, we show that important gains can be obtained, with backhaul offloadings and higher ratios of satisfied users reaching up to 22% and 26%, respectively. I. SMALL CELL NETWORKS: PAST, PRESENT AND FUTURE TRENDS Smartphones have exponentially increased the traffic load in current cellular networks showing no signs of slowing down [1], [2]. It is now well understood that a very effective way to increase network capacity is making cells smaller by reducing the distance to the users [3]. Indeed, cell densification has gone from the order of hundreds of square kilometers (back in the eighties) to a fraction of a square meter or less with the advent of hotspots. There has been recently a great interest to deploy relays, distributed antennas and small cellular access points (such as micro/pico/femto cells) in residential homes, subways, enterprises, and hot-spot areas. These network architectures, which are either operator-deployed or user-deployed are referred to heterogeneous networks (HetNets) or small cell networks (SCNs) [3], [4]. By deploying additional network nodes within local-area range and making the network closer to end-users, small cells can significantly improve spatial reuse and coverage, boost capacity, and offload traffic more efficiently [4]. April 13, 2015 DRAFT