Energy-Efficient Power Allocation Scheme for Distributed Antenna System Over Composite Fading Channels

In this paper, a power allocation (PA) scheme aiming at maximizing energy efficiency (EE) with minimum rate constraint is proposed for a distributed antenna system (DAS) in composite fading channels. The EE for DAS with dynamic circuit power consumption is first presented. Then, maximizing the EE under the maximum power constraint of each remote antenna (RA) and the minimum rate requirement of the system, an optimization problem is formulated. Based on this, two cases of the optimization problem are, respectively, analyzed. The first case is that the rate equals the given minimum value, and an effective algorithm is proposed to get the number of active antennas and the corresponding power allocation for this case. The second case is that the rate is greater than its given minimum value. For that case, we present an efficient algorithm, where the optimal number of active RAs is firstly derived, and then an optimal PA in closed form is achieved by using the Lambert function. By combining these two cases, an optimal PA scheme for the EE optimization problem is proposed, and it can include some existing optimal schemes as special cases. Simulation result shows that the proposed PA scheme is effective and applicable for different fading channels. Moreover, it can obtain the superior EE performance and meet the required constraints.