Optimum Power Allocation Policies for an Energy Harvesting Wireless Transmission System Under Energy Storage Losses

Abstract

This research work presents an energy harvesting model in which the transmitter harvests energy from the surrounding environment and stores it in an imperfect battery. Inevitably, this harvested energy has two kinds of extra consumption: battery storage losses and circuit power consumption. Towards this end, a single-user channel model is considered to determine the optimum power allocation policies for static and fading channels. The objective is to maximize the average throughput of an energy harvesting wireless transmission system within a finite time fraction during which transmission occurs. The throughput maximization problem is formulated with joint constraints viz., finite sized battery, circuit power consumption and limited amount of transmit power and solved using convex optimization techniques. Specifically, Lagrange multiplier method and Karush-Kuhn-Tucker (KKT) conditions are used to solve the proposed optimization problem. An optimum offline power allocation policy is proposed and an algorithm is provided to find optimum thresholds for power allocation. Moreover, an online power allocation policy is derived and an algorithm is provided with harvested energy available causally at the transmitter. For online algorithm, we consider adaptive thresholds that varies with storage efficiency and value of epoch. Simulation results show that the proposed offline and online algorithms have outperformed the earlier work focused on considering energy storage losses for energy harvesting wireless transmission systems.