Alain Pegatoquet

A Joint Duty-Cycle and Transmission Power Management for Energy Harvesting WSN

In this paper, we propose a global power management approach for energy harvesting sensor nodes. Our approach is based on a joint duty-cycle optimization and transmission power control. By simultaneously adapting both parameters, the node can maximize the number of transmitted packets while respecting the limited and time-varying amount of available energy. We obtain a high-packet delivery by using an original predictive transmission power control that can efficiently adapt the transmission power to the wireless channel conditions. To accurately model the wireless channel and the node communication hardware, a waveform-level radio frequency simulator has been developed. Simulation results show 6.5 times improvement in energy efficiency and a packet reception ratio which is 9 times more efficient than a recently published technique. A 15% increase in energy efficiency, with respect to a fixed transmission power configuration, has also been observed. Finally, the global power management strategy has been validated on a real wireless sensor networks platform. Experimental results are very similar to those obtained in simulations, and thus confirm the efficiency of our power management approach.

A framework for modeling and simulating energy harvesting WSN nodes with efficient power management policies

AbstractWireless sensor networks (WSNs) require an extremely energy-efficient design. As sensor nodes have limited power sources, the problem of autonomy is crucial. Energy harvesting provides a potential solution to this problem. However, as current energy harvesters produce only a small amount of energy and their storage capacity is limited, efficient power management techniques must also be considered. In this article we address the problem of modeling and simulating energy harvesting WSN nodes with efficient power management policies. We propose furthermore a framework that permits to describe and simulate an energy harvesting sensor node by using a high level modeling approach based on power consumption and energy harvesting. The node architectural parameters as well as the on-line power management techniques will also be specified. Two new power management architectures will be introduced, taking into account energy-neutral and negative-energy conditions. Simulations results show that the throughput of a sensor node can be improved up to 50% when compared to a state of the art power management algorithm for solar harvesting WSN. The simulation framework is then used to find an efficient system sizing for a solar energy harvesting WSN node.

Communication synthesis and HW/SW integration for embedded system design

The implementation of codesign applications generally requires the use of heterogeneous resources (e.g., processor cores, hardware accelerators) in one system. Interfacing hardware and software components together and providing communications between them are particularly error prone and time consuming tasks. Hence, on the basis of a generic architecture we propose an extended communication synthesis method that provides characterization of communications and their implementation scheme in the target architecture. This method takes place after partitioning and scheduling and can constitute the basis of a back end of a codesign framework leading to HW/SW integration.

Ultra low power asynchronous MAC protocol using wake-up radio for energy neutral WSN

To extend the system lifetime of WSN, energy harvesting techniques have been considered as potential solutions for long-term operations. Instead of minimizing the consumed energy as for the case of battery-powered systems, the harvesting node is adapted to Energy Neutral Operation (ENO) to achieve a theoretically infinite lifetime. Therefore, consumed energy due to communications is the critical issue to increase the system performance. In this paper, a nano-watt wake-up radio receiver (WUR) is used cooperatively with the main transceiver in order to reduce the wasted energy of idle listening in asynchronous MAC protocols where the node is waiting for potential messages, while still maintaining the same reactivity. Simulation results show that the throughput can be improve up to 82% with 53% energy saving compared to non-WUR approach of the TICER protocol. Our simulations are performed on OMNET++ with three different widely radio chips CC2420, CC2500 and CC1100 using models with measured data.

Duty-cycle power manager for thermal-powered Wireless Sensor Networks

Exploiting energy from the environment to extend the system lifetime of Wireless Sensor Network (WSN), especially thermal energy, is considered as a promising approach. When considering self-powered systems, the Power Manager (PM) plays an important role in energy harvesting WSNs. Instead of minimizing the consumed energy as in the case of battery-powered systems, it causes the harvesting node to converge to Energy Neutral Operation (ENO) in order to achieve a theoretically infinite lifetime. In this paper, a low complexity PM for a thermal-powered WSN is presented. Our PM adapts the duty cycle of the node according to the estimation of harvested energy and the consumed energy provided by a simple energy monitor for a super capacitor based WSN to achieve the ENO. Experiments are performed on a real WSN platform where harvested energy is extracted from the wasted heat of a PC adapter by two thermoelectric generators.

Using unified power format standard concepts for power-aware design and verification of systems-onchip at transaction level

Building efficient and correct system power-management strategies relies on efficient power architecture decision making as well as respecting structural dependencies induced by such architecture. Transaction level modelling allows a rapid exploration, verification and evaluation of alternative power-management architectures and strategies. This study introduces an efficient methodology for making system power decisions at transaction level (TL) by adding and verifying power intent and management capabilities into TL models. A generic framework that abstracts relevant concepts of the IEEE 1801 unified power format standard and implements assertion-based contracts is used throughout the methodology. A TL-model example is considered to validate the methodology.

A path analysis based partitioning for time constrained embedded systems

The HW/SW partitioning problem addressed in this paper is one of the key steps in the co-design flow of heterogeneous embedded systems. Generally the aim is to provide solutions that respect timing constraints and minimize an objective function such as the total area and/or the power consumption. Minimizing the hardware area conflicts with reducing execution time. Therefore, we introduce an heuristic for synthesizing heterogeneous systems that uses a global metric to guide the mapping of tasks according to the reusability of components and the time margin induced by timing constraints.

Energy-Efficient Power Manager and MAC Protocol for Multi-Hop Wireless Sensor Networks Powered by Periodic Energy Harvesting Sources

To overcome the limited energy in battery-powered wireless sensor networks (WSNs), harvested energy is considered as a potential solution to achieve autonomous systems. A power manager (PM) is usually embedded in wireless nodes to adapt the computation load by changing their wake-up interval according to the harvested energy. In order to prolong the network lifetime, the PM must ensure that every node satisfies the energy neutral operation (ENO) condition. However, when a multi-hop network is considered, changing the wake-up interval regularly may cripple the synchronization among nodes and, therefore, degrade the global system quality of service. In this paper, a wake-up variation reduction PM is proposed to solve this issue. This PM is applied for wireless nodes powered by a periodic energy source (e.g., light energy in an office) over a constant cycle of 24 h. Our PM not only follows the ENO condition, but also reduces the wake-up interval variations of WSN nodes. Based on this PM, an energy-efficient protocol, named synchronized wake-up interval MAC, is also proposed. OMNET++ simulation results using three different harvested profiles show that the data rate of a WSN node can be increased up to 65% and the latency reduced down to 57% compared with state-of-the-art PMs. Validations on a real WSN platform have also been performed and confirmed the efficiency of our approach.

A methodology for power-aware transaction-level models of systems-on-chip using UPF standard concepts

Building efficient and correct system power management strategies relies on efficient power architecture decision-making as well as respecting structural dependencies induced by such architecture. Transaction Level Modeling allows a rapid exploration, verification and evaluation of alternative power management architectures and strategies. This paper introduces an efficient methodology for making system power decisions at Transaction-Level (TL) by adding and verifying power intent and management capabilities into TL-models. A generic framework that abstracts relevant concepts of the IEEE 1801 (UPF) standard and implements assertion-based contracts is used throughout the methodology. A TL-model example is considered to validate the methodology.

Power Manager with PID Controller in Energy Harvesting Wireless Sensor Networks

System lifetime is the crucial problem of Wireless Sensor Networks (WSNs), and exploiting environmental energy provides a potential solution for this problem. When considering self-powered systems, the Power Manager (PM) plays an important role in energy harvesting WSNs. Instead of minimizing the consumption energy as in the case of battery powered systems, it makes the harvesting node converge to Energy Neutral Operation (ENO) to achieve a theoretically infinite lifetime and maximize the system performance. In this paper, a low complexity PM with a Proportional Integral Derivative (PID) controller is introduced. This PM monitors the buffered energy in the storage device and performs adaptation by changing the wake-up period of the wireless node. This shows the interest of our approach since the impractical monitoring harvested energy as well as consumed energy is not required as it is the case in other previously proposed techniques. Experimental results are performed on a real WSN platform with two solar cells in an indoor environment. The PID controller provides a practical strategy for long-term operations of the node in various environmental conditions.