Alexandre Boe

UWB-IR transceiver for millimeter wave WLAN

The purpose of this paper is to demonstrate the high potentiality in terms of data rate and multiple access of a novel 60 GHz WLAN architecture for smart objects and indoor communication systems. This approach is based on the up-conversion of an ultra wide bandwidth impulse radio signal (IR-UWB) in the 60 GHz frequency range to benefit of the natural advantages of the UWB technique while avoiding the base band limitations (FCC part 15, interferences, antenna size,...). This complete architecture has been designed using a pHEMT foundry process (f t = 100 GHz). Each mm-wave and base band devices have been tested: mm-wave source, modulator, amplifiers, RF detector and correlator. The final demonstrator is fully monolithically integrated. A space division multiple access (SDMA) multi users is now under test using smart antennas. This is done using quasi-YAGI antennas switched with RF MEMS. In fact, future high data rate WLAN (wireless local area network) will be realized using smart antennas to reduce in the same time the consumption, the link budget and the multipath effects

Energy Consumption of Networked Embedded Systems

The Web of Things (WoT) defines the idea of addressing and requesting any surrounding connected device through Web applications. These devices are for a large part, tiny, wireless and mostly battery-powered. Therefore, energy represents a critical limiting resource for their large scale deployment in real life applications, such as smart cities or smart buildings. Consequently, the ability to measure, track and finely profile energy consumption of such devices and correlate it with the application driving the device functionalities is a big challenge to improve the development of WoT embedded applications. In this paper, we present our recent ongoing works on energy consumption measurement of networked embedded applications for the WoT area. More particularly, we focus on measuring energy consumption of the well-known Contiki Operating System HTTP Web server using two measurement methods, a simulation based method and a real world software based measurement method. Doing this, we quantify and model the gap existing between the simulation and the real world regarding network embedded applications, such as embedded Web servers. Afterwards, we describe our aims in using a real world hardware energy consumption measurement method and profile a home-made embedded Web server prototype called Smews. This latter could theoretically improve performances and power consumption of WoT applications relying on TCP/IP protocol.

60 GHz UWB-IR Transceiver With Pulsed-Injected Locked Oscillator

A simple but efficient transceiver for UWB Impulse Radio (UWB-IR) signal generation in millimeter-wave band for Giga-bit WLAN is presented. The emitter involves a subharmonic Injection Locked Oscillator (ILO) driven by a pulse generator with fast transition time. Its frequency oscillation is locked to one of the numerous harmonic components of the pulse generator at 30 GHZ, which permits to obtain a stable pulse to pulse phase condition. The start of the oscillations is studied, using the external quality factor Qext as main factor. Then a frequency doubler permits this modulated signal to be transposed at 60 GHz. The receiver includes a LNA, a RF-detector and a UWB Sample and Hold Amplifier (SHA). Some MMIC have been designed using a commercial pHEMT foundry process (ft = 100 GHz=): a pulse generator exhibiting less than 25 ps transition times, an oscillator with a 30 GHz free running output frequency, a LNA, a MPA, a RF detector at 60 GHz and a UWB SHA.

A combined ASK-PPM Time Hopping UWB transceiver for millimetre wave Gigabit WLAN

A simple but efficient architecture based on up-conversion of impulse radio (IR) signals at 55 GHz is presented. This complete architecture has been designed using a pHEMT foundry process (ft =100 GHz). Key results on mm-waves devices-VCO, frequency doubler, RF switch, LNA and RF detector-are presented and discussed. Baseband devices, composed of a pulse generator and a sample-and-hold amplifier, are also presented with experimental results. These results show our fully monolithically integrated demonstrator performs PPM time hoping and ASK modulation schemes with respective data rate up to 500 Mbps and 1 Gbps

Experimental evaluation of interference impact on the energy consumption in Wireless Sensor Networks

In the era of Internet of Things (IoT), the development of Wireless Sensor Networks (WSN) arises different challenges. Two of the main issues are electromagnetic interference and the lifetime of WSN nodes. In this paper, we show and evaluate experimentally the relation between interference and energy consumption, which impacts the network lifetime. We present a platform based on commercially available low-cost hardware in order to evaluate the impact of electromagnetic interference in 2.4 GHz ISM band on energy consumption of WSN. The energy measurements are obtained separately from each electronic component in the node. Interference and energy measurements are conducted in an anechoic chamber and in an office-type lab environment. X-MAC protocol is chosen to manage the Radio Duty Cycle of the nodes and its energy performance is evaluated. The energy consumption transmitter nodes is analyzed particularly in this work. Moreover, this energy consumption has been quantified and differentiated according to the number of (re-)transmissions carried out by the transmitter as well as the number of ACK packets sent by the receiver for a single packet. Finally, we use a model of real battery to calculate the lifetime of the node for operation within different interference level zones. This study lays the basis for further design rules of communication protocols and development of WSNs.

Toward Energy Profiling of Connected Embedded Systems

A huge number of connected objects are expected to be deployed over the coming years in various areas of everyday life. Many of these objects are energy-constrained and depend on a battery. Thus, energy is a critical resource that limits a large scale deployment, and greatly complicates the development of the embedded software on these objects. Hence, the ability to measure and finely profile the power consumption of such devices, and correlate it with the on-board application is a big challenge to improve the software development. Furthermore, common energy patterns can be extracted from the collected energy figures in order to provide guidelines allowing a proactive energy-based development. In this paper, we present an ongoing work about a lightweight framework for energy profiling of embedded applications source code at a functional granularity. It is driven by an on-line hardware-based measurement technique permitting to gather accurate energy figures. The framework is integrated into an energy-centric iterative development cycle allowing fast revaluations of the energy consumed by the targeted functions after each source code modification. Afterwards, we describe our future works about overcoming an unlocked state of art issue relative to asynchronous energy consumption profiling.

Porous Gold Films Fabricated by Wet-Chemistry Processes

Porous gold films presented in this paper are formed by combining gold electroless deposition and polystyrene beads templating methods. This original approach allows the formation of conductive films 2 × 106 Ω·cm−1 with tailored and interconnected porosity. The porous gold film was deposited up to 1.2 μm on the silicon substrate without delamination. An original zirconia gel matrix containing gold nanoparticles deposited on the substrate acts both as an adhesion layer through the creation of covalent bonds and as a seed layer for the metallic gold film growth. Dip-coating parameters and gold electroless deposition kinetics have been optimized in order to create a three-dimensional network of 20 nm wide pores separated by 20 nm thick continuous gold layers. The resulting porous gold films were characterized by GIXRD, SEM, krypton adsorption-desorption, and 4-point probes method. The process is adaptable to different pore sizes and based on wet-chemistry. Consequently, the porous gold films presented in this paper can be used in a wide range of applications such as sensing, catalysis, optics, or electronics.

Automatic Inference of Energy Models for Peripheral Components in Embedded Systems

Surrounding autonomous embedded devices are in a constant expansion. The advent and the rise of Internet of Things (IoT) enable these objects to take a giant step forward, especially regarding their large scale deployment in real-world applications of the everyday life. A significant part of these objects are battery-powered and energy-dependent. Thus, energy is a critical resource which greatly complicates the development of the embedded software. By decomposing the energy consumption of a battery-powered IoT device, we can see that peripheral components are the major contributors among the overall consumption. Indeed, these components are exploited and repeatedly used by the object to interact and communicate with its surrounding environment during all the application lifetime. Acquire the expertise to handle accurately, during the development stage, the behaviour of every on-board peripheral component is a big challenge to improve the development of IoT embedded applications. To guide the developer in this task, we propose an automated inference procedure of energy models for peripheral components. An accurate automata-based model of the energy consumption can be generated, with only little efforts from the developer, based on real runtime measurements, providing precise energy figures. The proposed process is focused on a lightweight code generation step and simple analyses of the energy output traces, allowing a quick regeneration of the models in the case of a peripheral component modification. We show the potentials of the proposed procedure by real experiments on real peripherals. The obtained results are satisfactory, and we believe that our proposition is able to enhance the embedded development in an energy-constrained environment.

Zirconia coating for enhanced thermal stability of gold nanoparticles

This paper describes a rapid, simple and one-step method for the preparation of 2–4 nm diameter zirconia-coated gold nanoparticles at room temperature. These nanoparticles were synthesized by two simultaneous processes: the chemical reduction of tetrachloroauric acid with sodium borohydride and the formation of zirconia sol–gel matrices. All the gold nanoparticle sols were characterized by UV–visible absorption and transmission electron microscopy to determine the nanoparticle size and shape. The synthesis method is a combination of a polymeric structure of the amorphous zirconia and the use of a strong reducing agent, and it yields to very small quasi-spherical gold nanoparticles at room temperature. The thermal stability up to 1200 °C of the coated nanoparticles was studied by x-ray diffraction. The metastable tetragonal phase of the zirconia coating was obtained at 400 °C, and a progressive transformation from tetragonal to monoclinic phases of the zirconia coating was observed up to 1100 °C. After the heat treatment at 400 °C, the crystallite size of the gold nanoparticles was about 29 nm, and it remained unchanged from 400 °C to 1200 °C. These results are promising for the development of such materials as doping elements for optical fiber applications.