Real-time scheduling refers to the problem in which there is a deadline associated with the execution of a task. In new generation embedded systems, tasks execute in devices that use a rechargeable energy storage unit (e.g. battery or ultracapacitor) and a recharging system (e.g. photovoltaic cells). In this paper, we address the scheduling problem for a uniprocessor platform with unique voltage and frequency, that is powered by a renewable energy storage unit. First, we describe our model where two constraints need to be studied: energy and deadlines. Since executing tasks require a certain amount of energy, traditional task scheduling like Earliest Deadline as Soon as possible (EDS) and Earliest Deadline as Late as possible (EDL) are no longer convenient. We present an on-line scheduling scheme, called EDeg (Earliest Deadline with energy guarantee), that jointly accounts for characteristics of the energy source, capacity of the energy storage as well as energy consumption of the tasks, and time. In order to demonstrate the benefits of our algorithm, we compare it by means of simulation with the classical EDS and EDL. And we show that EDeg outperforms these energy non-clairvoyant algorithms in terms of both deadline miss rate and size of the energy storage unit.

In this article, we present our investigations on the radiation of the power-line communication (PLC) system. Power line communication or power line carrier is a technology for carrying data on a conductor usually dedicated to electric power transmission. At high frequency, the power lines, whose are dimensioned and adjusted for electrical energy transfer, not to carry high frequency (HF) data signal, act then as radiating antennas.The system has a number of issues. The primary one is that power lines are inherently subject to a very noisy common mode current. The proliferation of electric, electronic, mobile and wireless devices contribute to increase this noise. The second major issue is the impact of data communication, the range of used frequencies is expected to be between 1 and 30 MHz. Power lines are unshielded and will act as transmitting antennas for the carried digital signals, and as receiving antennas of surrounded radio communications. Unshielded power cables at higher frequencies represent electromagnetic interferences (EMI) sources for existing communication systems that use the same frequency spectrum, such as military communications, hospital communications, radio astronomy, airport navigation systems and radio amateurs.In the sense of new perspective and growing technology, one of the most important aspects pertaining to the environmental electromagnetic compatibility (EMC) is electronic devices safety and human exposure to the radiation of power lines at high frequencies and possible adverse heat effects.The main objective of this paper is to determine rigorously the radiated electromagnetic field for different antenna lengths, different frequencies or wavelengths on near, intermediate and far zones.According to this 3D EMI distribution and to the real geometry of PLC, we propose a practical approach to minimize the radiated power by controlling the frequency band of the PLC system.

Ambient energy harvesting also known as energy scavenging is the process where energy is obtained from the environment, converted, and stored to power small devices such as wireless sensors. We present a variant of EDF scheduling algorithm called EH-EDF (Energy Harvesting-Earliest Deadline First). Decisions are taken at run-time without having prior knowledge about the future energy production and task characteristics. We gauge the performance of EH-EDF by means of simulations in order to show its benefits. We evaluate and compare several variants of EH-EDF in terms of percentage of feasible task sets. Metrics such as average length of the idle times are also considered. Simulations tend to demonstrate that no online scheduler can reach optimality in a real-time energy harvesting environment.

For the past decades, we have experienced an aggressive technology scaling due to the tremendous advancements of Integrated Circuit technology. As massive integration continues, the power consumption of the IC chips exponentially increases which further degraded the system reliability. This in turn poses significant challenges to the design of real-time autonomous systems. In this paper, we target the problem of designing advanced real-time scheduling algorithms that are subject to timing, energy consumption and fault-tolerant design constraints. To this end, we first investigated the problem of developing scheduling techniques for uniprocessor real-time systems that minimizes energy consumption while still tolerating up to k transient faults to preserve the system's reliability. Two scheduling algorithms are proposed: the first scheduler is an extension of an optimal fault-free energy-efficient scheduling algorithm, named ES-DVFS. The second algorithm aims to enhance the energy saving by reserving adequate slack time for recovery when faults strike. We derive a necessary and sufficient condition that must be efficiently checked for the time and energy feasibility of aperiodic jobs in the presence of failures. Later, we formally prove that the proposed algorithm is optimal for a k-fault-tolerant model. Our simulation results demonstrate that the proposed schedulers can efficiently improve energy savings when compared with previous works.

Abstract-In this paper we study the partitioned EDF scheduling in a homogeneous multiprocessor environment with Quality of Service (QoS) constraints. The system considered here is a real-time multiprocessor system assumed to be powered by rechargeable batteries. We address the issue of how to best partition a set of firm real-time tasks that can occasionally skip one instance according to a predefined QoS threshold. The main goal is to minimize the energy consumption of the system while offering solutions with respect to transient energy starvation situations the system can experiment. The contribution of the paper is twofold. First, we present a schedulability analysis of firm multiprocessor task sets under QoS constraints. Second we propose new partitionning heuristics integrating skips. The evaluation is conducted from several points of view (minimization of the total processor number, maximization of the spare capacity on each processor).