Spectral and Energy Efficiency Optimization Through Coordinated Transmission for Downlink Cloud Radio Access Networks

Cloud-based Radio Access Network (C-RAN) is capable of implementing flexible antenna installation and centralized processing to facilitate dense deployment of cells in the era of mobile traffic explosion. This paper investigates into the spectral and energy efficiency trade-off of C-RAN, and proposes optimized downlink coordinated transmission to enhance spectral efficiency (SE) and energy efficiency (EE). SE optimization is formulated as a sum rate maximization problem and solved by Lagrange multiplier method. EE optimization is formulated as a multi-objective function, and is then transformed into single objective function, which is solved by numerical search method. Simulations are conducted under different pre-coding configurations, and results demonstrate the effectiveness of proposed methods.