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— This paper analyzes the impact of beamforming antennas on the topological connectivity of multihop wireless networks. As a metric for the connectivity of the network, we use the percentage P (path) of nodes that are connected via a multi-hop path. We show that simple randomized beamforming — i.e., each node adjusts its main beam into a randomly chosen(More)
Solar harvesting circuits have been recently proposed to increase the autonomy of embedded systems. One key design challenge is how to optimize the efficiency of solar energy collection under non stationary light conditions. This paper proposes a scavenger that exploits miniaturized photovoltaic modules to perform automatic maximum power point tracking at a(More)
The paper studies the case of a sensor node which is operating with the power generated by an environmental source. We present our model of an energy driven scheduling scenario that is characterized by the capacity of the node's energy storage, the deadlines and the power dissipation of the tasks to be performed. Since the execution of these tasks requires(More)
Renewable energies can enable embedded systems to be functional indefinitely. In particular for small autonomous sensors, energy harvesting techniques have attracted much interest. This paper considers systems which provide services periodically with adjustable quality evaluated in terms of rewards. The reward garnered for one service is monotonically(More)
Recently, there has been a substantial interest in the design of systems that receive their energy from regenerative sources such as solar cells. In contrast to approaches that attempt to minimize the power consumption we are concerned with adapting parameters of the application such that a maximal utility is obtained while respecting the limited and(More)
—Recently, there has been a substantial interest in the design of systems that receive their energy from regenerative sources such as solar cells. In contrast to approaches that minimize the power consumption subject to performance constraints, we are concerned with optimizing the performance of an application while respecting the limited and time-varying(More)
Power management has been a critical issue in the design of embedded systems due to the limited power supply. To prolong the lifetime, energy minimization has been studied under performance constraints in the past decade. The emerging embedded systems with the capability to harvest energy from the environment have recently triggered the revision of power(More)
—The limited battery lifetime of modern embedded systems and mobile devices necessitates frequent battery recharging or replacement. Solar energy and small-size photovoltaic (PV) systems are attractive solutions to increase the autonomy of embedded and personal devices attempting to achieve perpetual operation. We present a batteryless solar-harvesting(More)
Energy harvesting has recently emerged as a feasible option to increase the operating time of sensor networks. If each node of the network, however, is powered by a fluctuating energy source, common power management solutions have to be reconceived. This holds in particular if real-time responsiveness of a given application has to be guaranteed. Task(More)
This paper investigates real-time scheduling in a system whose energy reservoir is replenished by an environmental power source. The execution of tasks is deemed primarily energy-driven, i.e., a task may only respect its deadline if its energy demand can be satisfied early enough. Hence, a useful scheduling policy should account for properties of the energy(More)