Comparison of three different optimization objectives for distributed antenna systems

In this paper, we discuss three different optimization objectives for a distributed antenna system (DAS). They are: (i) maximize sum-rate under the constraints of the system's minimum spectral efficiency (SE) requirements and overall transmit power of each remote access unit (RAU); (ii) minimize the overall transmit power while satisfying the system's minimum SE requirements and overall transmit power of each RAU; (iii) maximize energy efficiency (EE) while satisfying the system's minimum SE requirements and overall transmit power of each RAU. We use sub-gradient iteration approach to obtain the optimal power allocation algorithms for the maximum sum-rate and minimum the overall transmit power optimization problems. We exploit fractional programming method to investigate energy-efficient power allocation algorithm for the maximum EE optimization problem. Three efficient power allocation algorithms are developed to maximize sum-rate, minimize the overall transmit power, and maximize EE for the downlink multiuser DAS. Simulation results are provided to demonstrate the effectiveness of the developed three power allocation algorithms, and illustrate the EE performance of maximizing EE is higher than the two other optimization objectives.