On Greening Cellular Networks by Sharing Base Stations: A Game-theoretic Approach

With increasing demands for mobile data traffic, many base stations (BSs) consume a significant amount of electrical power with a lot of electricity bill. Many practical solutions include sharing BSs among mobile network operators (MNOs), in which an MNO’s BS allows to serve traffic from nearby users subscribing to other MNOs with being paid a certain roaming fee. However, without assurance of gains, MNOs would not agree to BS sharing. In this paper, we study pricing and user association policies that assure actual gains to each MNO in the BS sharing. We model this with a game that jointly involves the strategic decision of roaming price and user association, where we consider the flow-level dynamics of traffic. We assume a time-scale separation where pricing decision is made at a slower time scale than user association, as often done in practice. First, for a fixed roaming price we analyze the user association game, where we prove that (i) it is a potential game, (ii) there exists a unique pure Nash equilibrium (NE), and (iii) a distributed algorithm inspired by an approximate version of Jacobi play converges to the NE. We study the slower time-scale pricing decision game and prove that there exists a pure NE with achieving almost the efficiency of full cooperation (without roaming fee). We demonstrate that there exists a significant degree of energy saving, once an appropriate competition rule is provided, through numerical simulations under a variety of scenarios.