Energy-Efficient Sparse Beamforming in Cloud Radio Access Networks

In this paper, the optimization of energy efficiency (EE) and the improvement of user data rate in cloud radio access networks (C-RANs) are studied by introducing a weighted sparse beamforming (WSB) method. Using stochastic geometry tools, analytical expressions are derived to describe downlink ergodic rate and coverage probability for coordination multipoint joint transmission in C-RAN. Based on these expressions and by taking advantage of central processing and coordination in baseband unit pool, power allocation among remote radio heads is optimized using the WSB. The WSB optimization algorithm is based on water-filling power allocation strategy and redistributing the power among RRHs. The improvement in both EE and ergodic rate is achieved. The improvement in EE is pronounced up to 28% using WSB technique compare to the equal power beamforming method in the proposed C-RAN network.