Alain Sibille

An UWB-UHF semi-passive RFID System for localization and tracking applications

We present a novel radio-frequency identification (RFID) system with capability of localization and tracking of passive or semi-passive tags. Localization and tracking features are enabled by backscatter modulation on ultra-wide bandwidth tags antenna. A ultra-high frequency signal allows the wake-up of the tags enabling the reduction of energy consumption and ensuring compatibility with existing RFID systems. The overall system as well as the reader and tag architectures are introduced. The localization and tracking performance evaluation is presented in some reference scenarios.

Modeling of the influence of body-worn antennas upon the Path Loss variability in UWB WBAN scenarios

The achieved work on the propagation channel of Wireless Body Area Networks has reached today a significant level. However, a large dispersion of reported results, notably as regards Path Loss is observed, both in anechoic chamber and in indoor premises. This work is motivated by this context, the main objectives being on one hand to explain (at least partly) and on the other hand to reduce this dispersion. Measurements have been performed in an anechoic chamber with two human subjects over a 1–12 GHz frequency band. A comparative analysis of the Path Loss involving nine UWB antennas of various types is presented for the Hip-to-Chest and Hip-to-Wrist scenarios. A statistical analysis of the corresponding dataset with a parametric approach with respect to various UWB frequency bands, antenna distance from the body and arm position is exposed next. Parametric models depending on either parameter extracted for various bands, are finally provided. The main objective of is to reduce the variances of the resulting statistical models through a parametric approach and categorization of antennas.

Joint antenna-channel statistical modelling of UWB backscattering RFID

ultra wide band semi-passive RFID based on a backscattering principle promise an excellent trade-off in terms of cost, range and localization capability. However, this trade-off will be deeply impacted by the characteristics of the backscattering, which involves both the propagation channel and the tag antenna mode behaviour. This work addresses the joint modelling of both, starting from rigorous electromagnetic principles. It highlights the necessity to combine the tag randomness with that of the channel, especially in the angular and polarization domains. It also sketches some routes towards this modelling.

Analysis of Secret Key Robustness in Indoor Radio Channel Measurements

In the recent years, a set of works have addressed inherent characteristics of the fading propagation channel in an information-theoretic framework oriented towards security. In particular, for cryptographic purposes, secure key bits can be extracted from reciprocal radio channels, seen as a shared source of randomness between any two entities. In this paper we intend to assess the impact of true radio channel features on the security performance, by quantizing the complex channel coefficients into discrete key bits. To this end, indoor channel measurements were performed and investigated in different scenarios, e.g. LOS/NLOS condition, narrowband (NB) as well as wide band (WB) targeting OFDM systems. Secret key robustness is firstly studied for the legitimate terminals in terms of key bit disagreement ratio and key randomness, and secondly by considering an eavesdropper in a wide set of positions around these terminals and by evaluating the difference between the generated keys. A simplified channel model is also analyzed in comparison with the measured channels, as regards the characteristics of generated key bits.

Interaction of UWB Tag Backscattering With Close Metallic Reflectors

Ultrawideband (UWB) radio frequency identification (RFID) systems for real-time objects identification and localization represent a promising solution for a future generation of RFID, as they can overcome current narrowband technology limitations. As is well known from the literature, it is very challenging to ensure a reliable RFID communication when tags are placed in proximity of metallic reflectors. For this reason, we here investigate the interaction between a UWB RFID tag and a close metallic disturber, assuming semi-passive tags operating in modulated backscattering. The impact of the metallic reflector on the tags backscattering pattern and RFID system coverage is evaluated, showing how tag detection is affected since the energy is mainly concentrated in certain directions.

Modulation Scheme and Channel Dependence of Ultra-Wideband Antenna Performance

This letter applies a new statistical approach for the performance evaluation of ultra-wideband (UWB) communications antennas, to the comparison between time and frequency-based modulation schemes. The radio link output signal-to-noise ratio (SNR) is systematically referenced to that obtained by replacing the investigated antenna with an ideal one. This allows establishing a relative performance scale for antennas, suited to their context of use. In addition to the presentation of the method, this letter shows a few exemplary results demonstrating the antenna performance dependence on modulation and channel.

Tag signals for early authentication and Secret Key Generation in wireless public networks

In this paper, a new protocol is proposed for securing both authentication and communication in wireless public networks. It relies on the combination of two techniques presented in the article: Tag Signal (TS) and Secret Key Generation (SKG). First, tag signals are used to securely exchange identification information, perform Channel Frequency Response (CFR) and provide a controlled radio advantage to legitimate users. Then secret keys are generated using authenticated CFR to protect communication. In addition to the presentation of the techniques, measured CFR and SKG performance are also provided for real WiFi communications.

A Novel Methodology to Evaluate Uplink Exposure by Personal Devices in Wireless Networks

Over the last 20 years, the wireless technology has known a large development in terms of devices and services, accompanied consequently by considerable doubts about the level of exposure to the electromagnetic fields radiated by these systems. An intermediate step in the assessment of the real exposure is to statistically model the input power delivered to these personal devices during an uplink transmission. In this spirit, we propose a systematic methodology for the characterization of the variability of the delivered input power for given propagation conditions. This methodology first addresses the influence of the personal devices relative positioning, with respect to the users body on the antennas performance as well as on the exposure level. Second, it add-resses the sensitivity of the input power to the characteristics of the propagation channel. The exposure levels have been investigated from specific absorption rates computed using finite-difference time-domain simulations on a realistic numerical model of child bodies. The input power is directly related to the antenna radiation pattern and to the local propagation scenario, through effects such as body obstruction and multipath diversity. The statistical analysis shows that the delivered input power can be modeled by an inverse Gaussian or a log-normal distribution.

Analysis of Alice-Bob-Eve scenarios for secret key generation from random channels

We address fundamental issues related in providing randomness and security for secret key generation from radio channel characteristics, based on an analysis of the knowledge shared by Alice/Bob/Eve.

Assessment and Modelling of Terminal Antenna Systems

The pervasive use and insatiable demand for high-performance wireless devices globally are driving the development of new communication technologies and standards. In this chapter, we present advancements in the area of terminal antenna systems and describe how they play a major role in enabling strict performance requirements to be met in future systems. As opposed to conventional systems that do not require explicit considerations of the terminal antenna beyond the satisfaction of some predefined design criteria in impedance bandwidth, radiation pattern and efficiency, multiple antenna systems in upcoming and future wireless networks must deliver significantly higher performance goals.