Coordinated beamforming for energy efficient transmission in distributed antenna systems

In this paper, coordinated beamforming scheme in distributed antenna systems (DASs) used for energy efficient transmission is developed. The major problem is non-convex of the optimization problem and is difficult to solve directly due to the fractional form. It is transformed into an equivalent subtractive-form optimization problem, by which we tackle this problem through a two-layer optimization algorithm. The out layer problem is solved by one dimension search method. The inner-layer sub-problem is solved with an optimal beamforming algorithm which is developed by exploiting the relationship between the user rate and the mean square error (MSE) of the received signal. The simulations illustrate that the higher energy efficiency can be achieved with the proposed algorithm than the weighted minimum mean square error (WMMSE) algorithm.