An energy efficient covariance optimization scheme for distributed antenna systems in broadcast channel

In this paper, we discuss energy efficient covariance optimization scheme for the downlink multiuser distributed antenna systems in broadcast channel (DAS-BC). The energy efficiency (EE) optimization problem for DAS-BC is a non-convex optimization problem. Therefore, according to the duality between multiple-input multiple-output (MIMO)-BC and MIMO-multi-access channel (MAC), we first transform the non-convex EE optimization problem to a convex optimization problem. Then exploiting the theory of fractional programming, we convert the EE optimization problem of DAS-BC in fractional form into an equivalent optimization problem in subtractive form. Next, an optimal energy efficient covariance matrix algorithm is developed to maximize EE in DAS-BC. Through computer simulation, we demonstrate that the performance of EE and SE (spectral efficiency) for DAS-BC are better than co-located antenna systems in broadcast channel (CAS-BC).