CEO - Cost-Aware Energy Efficient Mobile Data Offloading via Opportunistic Communication.

With the surging demand of data access, end users of mobile devices are increasingly facing the tradeoff between delay, energy efficiency, and monetary cost. Although delayed data offloading is seen as a promising solution, a coherent data offloading framework which simultaneously considers all three aspects is still missing. To fill this gap, we study the problem of cost-aware energy efficient offloading. We formulate the problem as a discrete time optimal control problem, and show that the optimal policy has a threshold-based structure. We further propose the Cost-aware Energy efficient Offloading (CEO) policy, which approximates the optimal policy and can be calculated efficiently. Through extensive simulations, we demonstrate that CEO adapts well to users' preference of monetary cost and to the network environment. When compared to the state-of-art protocol, CEO can achieve up to 64% PDR improvement when cellular usage is to be avoided, and it can achieve a reduction of up to 23% in energy consumption, when the energy consumption is to be minimized.