A Stochastic ADMM Approach to Distributed Coordinated Multicell Beamforming for Renewables Powered Wireless Cellular Networks

The availability of renewable energy sources (RES) has facilitated efficient and sustainable resource allocation for wireless communication systems. In this paper, a novel framework is proposed to implement coordinated multicell beamforming (CMBF) scheme for cellular networks powered by a smart microgrid, where the BSs are equipped with RES harvesting devices and can buy/sell energy from/to the main grid. New models are developed to capture the stochastic energy harvesting, dynamic electricity prices, and energy transaction cost gauged by the conditional value-at-risk (CVaR) function. Based upon these models, a distributed CMBF scheme is put forth to minimize the grid-wide transaction cost under user quality-of-service (QoS) constraints. Specifically, it is shown that the relevant task can be cast into a convex program to be tackled in a distributed fashion, leveraging the state of the art optimization tools. To deal with the unpredictable nature of the renewable energy, the stochastic alternating direction method of multipliers is then employed to develop a novel distributed CMBF scheme. It is established that the proposed scheme can guarantee optimality of the obtained CMBF solution, using only local channel state information at each BS and limited information exchange among the BSs. Merits of the proposed scheme are corroborated by extensive numerical results.