B. Denis

Impact of NLOS propagation upon ranging precision in UWB systems

The ultra wideband (UWB) radiolocation functionality usually relies on the ability to perform a very precise estimation of the time of flight (TOF). Unfortunately, in spite of the fine performances demonstrated by the UWB systems, indoor dense multipath channels may alter the precision of the range estimate from severe blockage situations. This paper addresses the general problem of non line of sight (NLOS) errors in the specific context of UWB range estimation. Typical ranging errors due to the NLOS propagation are exhibited by deriving experimental results from real indoor VNA measurements into realistic statistical error models.

Performance analysis of LDR UWB non-coherent receivers in multipath environments

This paper presents an analytical comparison of three modulation schemes applied to two low data rate (LDR) ultra wideband (UWB) non-coherent receivers, namely the quadratic detector and the differential detector. In order to evaluate properly the impact of UWB multipath channels on performance, new statistical models on energy collection are proposed, and then taken into account in the analytical expressions of the error probability. Finally, critical system parameters, such as the optimal integration time for energy collection or major synchronization tolerances (coarse synchronization granularity, clock constraints) are derived from the obtained results.

On the scheduling of ranging and distributed positioning updates in cooperative IR-UWB networks

The recent demonstration of precise ranging measurements through low power Low Data Rate (LDR) Impulse Radio - Ultra Wideband (IR-UWB) communications has disclosed new perspectives for cooperative location-enabled wireless networks. With this respect, joint ranging and distributed positioning mechanisms supported by specific protocol transactions have already been proposed within user-centric infrastructureless applications. However, in spite of advanced medium access techniques, those approaches still suffer from resource inefficiency. In this paper, we describe and compare new scheduling strategies regarding the joint update of ranging measurements and positional information. One goal is to accelerate the convergence of positioning errors and hence to reduce network latency and overhead accordingly. As an example, one scheduling option considers discarding so-called useless pair-wise links based on the prior analysis of the conditional Cramer Rao Lower Bound (CRLB) of positioning errors at each mobile node.

Synergetic MAC and higher layers functionalities for UWB LDR-LT wireless networks

This paper deals with Medium Access Control (MAC) techniques adapted to location applications in Ultra Wideband (UWB) Low Data Rate (LDR) wireless networks for which low power consumption, low complexity location and relaying capabilities are identified as critical features. In comparison with the IEEE 802.15.4 MAC, the proposed solution is completely described by the use of self-contained beacons. We introduce here some of the supported functionalities in compliance with recent Low Duty Cycle (LDC) requirements. Under realistic ranging models, we also evaluate the performance of joint ranging/positioning procedures through event-driven packet-oriented simulations.

Performance analysis of low complexity solutions for UWB low data rate impulse radio

This paper analyzes and compares the performance of non-coherent and differential receivers under realistic channels for both synchronization and communication. The well-known error probabilities are reminded and the receiver operating characteristics (ROC) are calculated. It also provides some recommendations to system designers, proposes and discusses critical concepts for a low complexity implementation of the proposed schemes, in compliance with the ranging functionality

Performances analysis of a UWB receiver using complex processing

Ultra wideband (UWB) systems are characterized by the transmission of very low power spectral density signals using bandwidths from 500 MHz up to several GHz and propagating through dense multipath channels. Digital communications using UWB impulse radio concern, among others, high data rate transmissions, for instance between 1 Mbps and 1 Gbps. The aim of this analysis is to define a generic UWB model, in terms of signal shape, modulation scheme and channel representation. Then, this model is used to specify and evaluate a brand-new principle of UWB receiver based on a mono band complex processing and maximum ratio combining.

Ultra wideband: the radio link of the future?

A new data transmission technique is about to create a revolution in the field of wireless local area networks. This new method, called Ultra Wideband, is based on the transmission of data through the communication channel below the noise floor. It involves transmitting very short duration pulses, which has the effect of spreading the signal energy across a wide frequency range. The objective of this article is to report on the state of the art in this research area, and to outline the main advantages of this promising data transmission method.RésuméUne nouvelle technique de transmission de données est en train de révolutionner le domaine des communications sans fil courte portée. Cette nouvelle technique, connue sous le nom de transmission Ultra Large Bande, consiste à émettre les données sur le canal radio en dessous du plancher de bruit. Pour cela, on transmet des impulsions de très courte durée qui vont étaler leur énergie dans une large plage de fréquences. Le présent article a pour objectif de dresser un état de l’art des recherches dans ce domaine ainsi que de mettre en évidence les principaux avantages de cette méthode très prometteuse.

Performance of IEEE 802.15.4a UWB Systems Under Multi-User Interference

In this paper, we evaluate the performance of impulse radio-ultra wideband (IR-UWB) communications at the physical layer (PHY) level in a multi-user low data rate (LDR) context. Focusing more specifically on the IEEE 802.15.4a standard, this study aims at characterizing and quantifying the potential interference effects resulting from simultaneous competing transmissions. For the sake of simplicity, we deliberately restrict the investigation to a generic coherent Rake receiver in typical illustrating scenarios (in terms of nominal bit rate, pulse repetition period, and channel configuration). On this occasion, we provide original semi-analytical bit error rate (BER) models and simulation results, along with realistic figures for the corresponding tolerated SIR and SNR levels. The derived interference specifications, which properly abstract the IEEE 802.15.4a PHY layer in the presence of MUI, can be considered as relevant inputs for further system, medium access control (MAC), or cross-layer studies.