Low-Complexity Energy-Efficient Power Allocation With Buffer Constraint in HSR Communications

In this paper, we investigate the energy-efficient power allocation for downlink distributed antenna system (DAS) with buffer size constraint in high-speed railway (HSR) scenarios. We design the power allocation at different times for HSR communications, utilizing the characteristics of fixed moving path of trains. A key issue we discuss is the matching problem between the data arrival process and instantaneous wireless transmission process under the buffer size constraint. We formulate the energy-efficient power allocation problem with the requirement of buffer size as a non-convex optimization problem. By a parameterized transformation and an iterative algorithm, we derive the optimal solution at different time phases. Then, to reduce complexity of the multiple iterations, we present a low-complexity algorithm by analyzing the feasible region of the optimal solution. Simulation results demonstrate that the proposed power allocation schemes can achieve the optimal energy efficiency (EE) and avoid data overflow. Moreover, with a smaller number of iterations, the low-complexity algorithm can achieve the same EE performance as the optimal algorithm based on the bisection method.