Harvesting Short-Lived White Spaces via Opportunistic Traffic Offloading Between Mobile Service Providers

Currently, Wi-Fi (IEEE 802.11) is the most widely adopted wireless technology for mobile traffic offloading at hot spots. Despite its great success, Wi-Fi is constrained by the over-crowded unlicensed spectrum, which leads to poor user experience, especially in urban areas. This paper introduces an opportunistic cooperation framework that allows mobile service providers (MSPs) to offload traffic onto each other's network by harvesting short-lived spectrum/resources of cellular systems. Specifically, through traffic offloading, MSPs aim to maximize their profit while maintaining their quality of service (QoS) commitments. For that purpose, we model the strategic cooperation between MSPs as a stochastic Markov game in which the dynamics of resource availability and user behaviors are captured via a Markov decision process. We prove that the game is irreducible and admits a Nash Equilibrium at which all MSPs benefit from traffic offloading. A practical algorithm that uses only local information to govern traffic offloading at MSPs is then developed. Numerical simulations show that by designing appropriate profit sharing contracts, our proposed algorithm can achieve almost the same performance as that of a socially optimal solution. The derived traffic offloading strategies not only improve QoS and revenue for MSPs, but also can be used to guide MSPs on when to turn off their base stations while the traffic volume is light (e.g., during nighttime).