Olivier Sentieys

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 Heuristic Self-Adaptive Medium Access Control for Resource-Constrained WBAN Systems

This paper presents a heuristic-based approach to self-adapt and reconfigures the wake-up schedule of the nodes in wireless body area networks (WBANs). A latency-energy-optimized traffic-aware dynamic medium access control protocol is presented. The protocol is based on an adaptive algorithm that allows the sensor nodes to adapt their wake-up and sleep patterns efficiently in static and dynamic traffic variations. The heuristic approach helps to characterize the algorithmic parameters with an objective to investigate the behavior of the convergence patterns of the WBAN nodes in a non-linear system. An open-loop form is developed by keeping the wake-up interval (Iwu) fixed followed by the closed-loop adaptive system which updates Iwu on every wake-up instant. An exhaustive search is conducted for different initial wake-up interval values which show that (on average) the algorithm parameters behave monotonically in open-loop systems, whereas a decaying function in the closed-loop form. Various performance metrics, such as energy consumption, packet delay, packet delivery ratio, and convergence speed (for reaching a steady state), are evaluated. It is observed that the convergence time varies from 8 to 72 s under fixed packet transmission rate, whereas the algorithm re-converges (within 8 s) whenever the transmission rate changes.

Phase-Preserving Power Limiting Function Using InP on SoI Photonic Crystal Nanocavity

We report on the use of an InP/silicon-on-insulator hybrid photonic crystal nanocavity for the realization of a phase-preserving all-optical power limiter. This function is experimentally demonstrated with 20-Gbit/s nonreturn-to-zero quadrature phase-shift-keying signals. Histogram-based measurements of the phase distributions indicate negligible variations of the phase noise, whereas the amplitude fluctuations are suppressed, confirming the effectiveness of cavity switching for implementing the power-limiter function. Significant power penalty reduction is achieved, indicating a promising application for future photonic circuits.

Communication-Based Power Modelling for Heterogeneous Multiprocessor Architectures

Programming heterogeneous multiprocessor architectures is a real challenge dealing with a huge design space. Computer-aided design and development tools try to circumvent this issue by simplifying instantiation mechanisms. However, energy consumption is not well supported in most of these tools due to the difficulty to obtain fast and accurate power estimation. To this aim, this paper proposes and validates a power model for such platforms. The methodology is based on micro-benchmarking to estimate the model parameters. The energy model mainly relies on the energy overheads induced by communications between processors in a parallel application. Power modelling and micro-benchmarks are validated using a Zynq-based heterogeneous architecture showing the accuracy of the model for several tested synthetic applications.