Low‐complexity energy efficient power allocation scheme for DAS with maximum power constraint

Abstract

In this paper, a low-complexity optimal power allocation (PA) scheme is developed to maximize energy efficiency (EE) in a distributed antenna system (DAS) under maximum power constraint and target bit error rate (BER) requirement.Composite Rayleigh fading, multiple receive antennas, and dynamic circuit power consumption are all considered in the system. Unlike conventional schemes, the presented scheme provides a closed-form expression of PA.Firstly, the optimization problem is formulated according to the definition of EE. Using the Karush-Kuhn-Tucker conditions, a general form of the optimal PA, in which the number of active antennas and corresponding power allocation are required only, is then proposed. With this general form, an effective algorithm is presented to yield the closed-form PA. The proposed scheme can be applied to the system with static circuit power consumption and/or without target BER constraint to obtain optimal PA. Simulation results corroborate the effectiveness of the developed scheme, and the scheme can achieve the same EE performance as the existing optimal schemes with lower complexity. Moreover, the distributed antenna system with multiple receive antennas has higher EE than that with single receive antenna. energy-efficient coordinated PA in a multicell DAS is addressed by using successive Taylor expansion and an iterative algorithm. A more practical case is considered for DAS in Feng et al, 12 where only the slowly varying large-scale channel information is known, and an optimal PA scheme to maximize EE is proposed by using the random matrix theory. Unfortunately, the above schemes require a great number of iterations basically. Taking this into account, an optimal PA scheme for EE maximization in DAS is proposed in Kim et al, 13 where the optimal PA is iteratively calculated by the Lambert function. To further reduce the calculation complexity in Kim et al, 13 a simplified PA scheme for EE maximization is developed in Wu et al, 14 but some minor errors have been found in the theoretical derivation for EE optimization, and the resulting PA coefficient may exceed the given maximum transmit power, so its accuracy is not guaranteed. For this reason, Ashraf et al 15 highlights some mistakes existing in Wu et al, 14 and an improved algorithm is presented, but its computational complexity is relatively higher and may be further reduced. In addition, the schemes above basically address single receive antenna, no dynamic power consumption, as well as no quality of service requirement for analysis convenience, and thus, these schemes lack generality.Motivated by the reason above, the EE of DAS is studied over composite Rayleigh channels including large-scale path loss and shadowing effect, where multiple receive antennas, dynamic circuit power consumption, and target BER requirement in practice are all considered. Through the theoretical derivation and performance analysis, an optimal PA scheme to maximize EE in DAS is developed. Computer simulations show that the proposed scheme is effective,...