Efficient Design and Control for Network-Assisted Device-to-Device Content Delivery Network

Proliferation of mobile devices over the past few years has explosively increased demand for multimedia content in various service scenarios such as video and game streaming. This growth in demand for mobile content has brought a significant challenge of how to efficiently deliver such content to users. Content delivery networks (CDNs) have grown in popularity as the most feasible solution to overcome this challenge. Many mobile network operators have tried to develop customized CDN solutions suited to their network systems in practice. In this paper, we focus on an intriguing paradigm where mobile devices are used as cache servers and localized content sharing is activated via device-to-device (D2D) communication. As the most feasible network system, we consider a network-assisted D2D CDN where a mobile network assists and controls D2D communication processes. We first investigate inherent characteristics of the network system, resulting in the following findings: 1) D2D communication utilization and 2) network assisted control. As a new approach to devise efficient CDN design and control algorithms that simultaneously consider the inherent characteristics, we adopt the Lyapunov stability theory. As a result, we can derive efficient algorithms including content placement, content request routing, and content scheduling as a total solution including CDN design as well as control based on a cross-layer design approach. Through packet simulations, it is demonstrated that the performance yielded by the proposed strategies is superior to that delivered by other strategies in terms of delay to directly represent content delivery performance.