Joint cell zooming and sleeping strategy in ultra dense heterogeneous networks

Abstract

To optimize the ultra dense distribution of base stations (BSs) which consist of micro BS and macro BS, balancing the tradeoff between user communication quality and energy saving is essential. In this paper, a joint cell zooming and sleeping strategy is proposed for the downlink two-tier heterogeneous network under the Poisson Point Process (PPP) model, in order to balance the user benefits and communication system operating cost. First, the cell zooming scheme is presented based on game theory, where the association probability of each base station is achieved by adjusting the cell zooming factor (CZF). With the improved BS association probability, more users can benefit with better network experience by connecting to micro BS instead of macro BS. Then a two-step sleeping strategy is put forward, by applying the cell zooming. The first step is to ascertain which BSs are kept based on the analysis of the energy consumption of candidates. The second step is used to measure the overall overlapping degree of each BS and provide different sleep decisions according to the radius of the area covered by MBS. The proposed sleeping scheme is able to stimulate the BS with a high overlapping degree to be slept to achieve more energy saving. Through the proposed joint schemes, the service efficiency of communication system is improved, when the users connect to micro BS instead of macro BS and some micro BSs with low utility are turned off. Simulation results indicate the improved performance in terms of the user experiences and energy saving.