Ultra wideband: applications, technology and future perspectives

Ultra Wide Band (UWB) wireless communications offers a radically different approach to wireless communication compared to conventional narrow band systems. Global interest in the technology is huge. This paper reports on the state of the art of UWB wireless technology and highlights key application areas, technological challenges, higher layer protocol issues, spectrum operating zones and future drivers. The majority of the discussion focuses on the state of the art of UWB technology as it is today and in the near future

Topological Quantum Field Theory on Non-Abelian Gerbes

The infinitesimal symmetries of a fully decomposed non-Abelian gerbe can be generated in terms of a nilpotent BRST operator, which is here constructed. The appearing fields find a natural interpretation in terms of the universal gerbe, a generalisation of the universal bundle. We comment on the construction of observables in the arising Topological Quantum Field Theory. It is also shown how the BRST operator and the trace part of a suitably truncated set of fields on the non-Abelian gerbe reduce directly to the coboundary operator and the pertinent cochains of the underlying Cech-de Rham complex.Comment: 36 pages, LaTeX; v2: version to appear in J.Geom.Phy

Dynamic Channel Modeling at 2.4 GHz for On-Body Area Networks

In wireless body area networks, on-body radio propagation channels are typically time-varying, because of the frequent body movements. The dynamic local body scattering dominates the temporal and spatial properties of the on-body channels. The influence varies largely depending on the distribution of the channels and the modes of body movements. In this paper, we present some major achievements on the dynamic onbody channel modeling at 2.4 GHz under the framework of the COST 2100 action. Results of two complementary measurement campaigns are presented: a geometry-based one on a single subject, and a scenario-based one covering different subjects. Statistical models including the Doppler spectrum and the spatial correlation of on-body channels are presented. An analytical model is also introduced to offer a time-space description of the on-body channels, which is validated by the geometry-based measurement campaign

Single Receiver Multi-antenna Code-Modulated IR-UWB Front-End

International audienceThe multi-antenna receiver has many usecases in wireless communications and Radar but it facessome major drawbacks such as high cost of hardware andhigh power consumption. Recent developments on narrowband systems have led to an alternative solution calledCode-Division Multiplexing (CDM), using a single RFreceiver front-end to receive signals from multi-antenna.For this purpose signals from the antennas are mixedwith high speed spreading codes and then are combinedat the RF stage. However, the use of high speed codesincreases the signal bandwidth. Applying this solution onUltra-Wide Band (UWB) systems is questionable because ofthe bandwidth increase. This paper discusses the principlesand implementation of CDM technique on an ImpulseRadio (IR) UWB system showing interesting insights. Anexperiment is performed to estimate the Angle-Of-Arrival(AOA) on the recovered signals in a basic indoor positioningscenario

Time Domain Complex Radar Cross Section of Human Body for Breath-Activity Monitoring

International audienceThe knowledge of the complex Radar Cross Section (RCS) of the human body in ultra-wide band can fully describe the breathing activity. In this paper, we investigate the timedomain RCS so as to analyze the backscattered signal from the human body, for further respiratory monitoring in any aspect angle. The time domain RCS measurements are first calibrated with the monostatic radar measurement of a metallic sphere. Subsequently, the RCS of a human body phantom is measured over the full 0-360o angle, azimuth range, allowing to put forward the creeping wave around the body. Finally, we measure the RCS of a human person and its temporal variation, also in various aspect angles. The results, which show a mixture between breathing and other body movements, are valuable inputs for respiratory monitoring in various body postures

Advanced Bayesian filtering techniques for UWB tracking systems in indoor environments

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Mutual Coupling Modeling and Calibration in Antenna Arrays for AOA Estimation

International audience<p>In antenna arrays, mutual coupling is an undesired effectwhich degrades the array pattern and the performance of array signal-processing algorithms like for Angle-Of-Arrival(AOA) estimation. Various approaches for mutual-couplingcompensation that evaluate the coupling in receiving andtransmitting modes have been studied. In this paper, a definition of the mutual coupling in receiving mode from thescattering parameters is introduced. A dissimilarity factoris added on the signals after the coupling calibration tosimulate amplitude and phase variations at the terminationof array elements. The coupling model shows the role ofantenna characteristics and distance between the elements.When the antennas are all connected to a matched load andthere is no dissimilarity between the antennas, the couplingin the receiving mode assimilates to that in the transmitting mode. To validate this statement, the coupling of an array of two patch antenna elements in these two modes is calculated, which shows an adequate agreement. A simplified technique calibrating the coupling and the dissimilarity is also proposed. The application of these couplingcalibration techniques together shows many possibilities to improve antenna arrays processing.</p

Performance evaluation of direct and cooperative transmissions in body area networks

International audienceBody area networks (BAN) offer amazing perspectives to instrument and support humans in many aspects of their life. Among all possible applications, this paper focuses on body monitoring applications having a body equipped with a set of sensors transmitting in real time their measures to a common sink. In this context, at the application level, the network fits with a star topology, which is quite usual in the broad scope of wireless networks. Unfortunately, the structure of the network at the physical layer is totally different. Indeed, due to the specificity of BAN radio channel features, all radio links are not stationary and all sensors suffer from link losses during independent time frames. In wireless networks, link losses are often coped with multi-hop transmission schemes to ensure a good connectivity. However, since the radio links are not stationary, the multi-hop routes should adapt quickly to BAN changes. We instead propose in this work a different approach based on opportunistic relaying. The concept relies on electing some sensors to support the transmission of other ones having a worst connection. Instead of changing the relay time to time, we rather select a relay node from a statistical perspective. We evaluate this approach from a theoretical point of view and on realistic simulations using the packet error rate outage probability as a performance criterion