Performance Enhancement of Multiuser Time Reversal UWB Communication System

UWB communication is a recent research area for indoor propagation channels. Time Reversal (TR) communication in UWB has shown promising results for improving the system performance. In multiuser environment, the system performance is significantly degraded due to the interference among different users. TR reduces the interference caused by multiusers due to its spatial focusing property. The performance of a multiuser TR communication system is further improved if the TR filter is modified. In this paper, multiuser TR in UWB communication is investigated using simple TR filter and a modified TR filter with circular shift operation. The concept of circular shift in TR is analytically studied. Thereafter, the channel impulse responses (CIR) of a typical indoor laboratory environment are measured. The measured CIRs are used to analyze the received signal peak power and signal to interference ratio (SIR) with and without performing the circular shift operation in a multiuser environment

Time Domain Measurements for a Time Reversal SIMO System in Reverberation Chamber and in an Indoor Environment

International audienceTime domain measurements are conducted for ultra-wideband (UWB) signals in a reverberation chamber (RC) and in a typical indoor environment for a single input multiple output (SIMO) time reversal (TR) system. Different TR characteristics i.e. TR peak performance, TR focusing gain, average power increase, signal to side lobe ratio (SSR) and delay spread are analyzed and compared to that of a single input single output (SISO) TR system

Multiuser Time Reversal UWB Communication System: A Modified Transmission Approach

International audienceIn this paper, ultra-wideband (UWB), time reversal (TR) communication is investigated by modifying the transmission prefilter. Mathematical expressions for received signal and the interference in the modified transmission scheme are derived. It is shown that the modified transmission approach reduces multi-user interference which eventually translates into a better bit error rate (BER) performance than simple TR multiuser scheme. Channel impulse responses (CIR) of a typical indoor channel are measured. In a multi-user scenario, both TR and the modified TR schemes are studied using the measured CIRs. It is shown that the proposed modified TR scheme outperforms the original TR scheme

Deep Learning-aided TR-UWB MIMO System

This paper presents a novel deep learning-aided scheme dubbed PRρ-net for improving the bit error rate (BER) of the Time Reversal (TR) Ultra-Wideband (UWB) Multiple Input Multiple Output (MIMO) system with imperfect Channel State Information (CSI). The designed system employs Frequency Division Duplexing (FDD) with explicit feedback in a scenario where the CSI is subject to estimation and quantization errors. Imperfect CSI causes a drastic increase in BER of the FDD-based TR-UWB MIMO system, and we tackle this problem by proposing a novel neural network-aided design for the conventional precoder at the transmitter and equalizer at the receiver. A closed-form expression for the initial estimation of the channel correlation is derived by utilizing transmitted data in time-varying channel conditions modeled as a Markov process. Subsequently, a neural network-aided design is proposed to improve the initial estimate of channel correlation. An adaptive pilot transmission strategy for a more efficient data transmission is proposed that uses channel correlation information. The theoretical analysis of the model under the Gaussian assumptions is presented, and the results agree with the Monte-Carlo simulations. The simulation results indicate high performance gains when the suggested neural networks are used to combat the effect of channel imperfections

Time Reversal UWB Communication: Experimental Study for High Data Rates in Dense Multipath Propagation Channels

International audienceHigh data rate communication for a Time Reversal UWB communication system is experimentally studied using binary pulse amplitude modulation in dense multipath propagation channels. Experiments are done for inter symbol intervals ranging from 64ns to 1ns. Signal, Interference and Noise components are separated from the received signal and their bit error rates are computed. The received signals are neither processed nor equalized. It is shown that at very high data rates (>125 Mbps), the performance of the system is limited by inter symbol interference. However at high data rates (<125 Mbps), time reversal system gives good BER performance in the presence of inter symbol interferenc

Machine learning and blockchain technologies for cybersecurity in connected vehicles

Future connected and autonomous vehicles (CAVs) must be secured againstcyberattacks for their everyday functions on the road so that safety of passengersand vehicles can be ensured. This article presents a holistic review of cybersecurityattacks on sensors and threats regardingmulti-modal sensor fusion. A compre-hensive review of cyberattacks on intra-vehicle and inter-vehicle communicationsis presented afterward. Besides the analysis of conventional cybersecurity threatsand countermeasures for CAV systems,a detailed review of modern machinelearning, federated learning, and blockchain approach is also conducted to safe-guard CAVs. Machine learning and data mining-aided intrusion detection systemsand other countermeasures dealing with these challenges are elaborated at theend of the related section. In the last section, research challenges and future direc-tions are identified

Application du retournement temporel (RT) aux systèmes de communications ultra large bande (ULB) et multi-antennes (MIMO)

In ultra wideband (UWB) systems, extremely narrow RF pulses are employed to communicate between transmitters and receivers. Because of their extremely wide bandwidth, UWB signals result in large number of resolvable multi-paths and thus reducing the interference caused by the superposition of these multi-paths. However, it also results in a complex receiver system. Time reversal (TR) is a transmission approach which permits to detect the received signal with simple receivers by shifting the complexity to the transmitter. The received signal in the TR scheme is very focused in time and spatial domains. Temporal and spatial focusing permit to reduce inter symbol interference and multi-user interference respectively. In this Ph.D. thesis, we investigate the TR UWB scheme and its application to high data rate communications. A validation of the TR scheme in the laboratory is performed with simulation, semi-measurement and measurement approaches. A parametric analysis of the TR is carried out with multiple antenna configurations (SISO, SIMO, MISO and MIMO). The results show that MIMO-TR outperforms all other configurations The robustness of the TR scheme is also studied in non stationary environments. The results suggest that if the channel maintains some partial correlation with the previous channel, TR can give a robust performance even if the total correlation of the channels is very low. Although higher bandwidths generally give better performance than the lower bandwidths, but the degradation in the performance with the variations in the channel is of the same magnitude Furthermore, TR scheme is investigated from the communication point of view. Experimental validations of a new modulation scheme and high data rate communication for TR UWB are performed for dense multipath propagation channels. It is shown that the BER performance in the indoor channel is better than the reverberation chamber. Furthermore, with the sub-band TR transmission approach, a sort of equalization is achieved which significantly improves the BER performance Finally, multi-user TR communication has been examined with modifications in the TR pre-filter. The modified TR scheme outperforms simple TR and TR with circular shift scheme, especially at higher number of simultaneous users. The results presented in this thesis suggest that the TR UWB scheme, which can easily be combined with the MIMO systems, is a promising and attractive transmission approach for future wireless local and personal area networks (WLAN & WPAN) and wireless streaming applications.Dans les systèmes ultra large bande (ULB), des impulsions RF extrêmement étroites sont employées pour la communication entre émetteurs et récepteurs. En raison de leur bande passante très large, les signaux ULB entraînent un grand nombre de trajets multiples résolvables et donc réduisent les interférences provoquées par la superposition de ces trajets. Toutefois, cela nécessite la mise en œuvre d'un système de réception complexe. Le retournement temporel (RT) est une approche qui permet d'utiliser des récepteurs simples en déplaçant la complexité vers l'émetteur. Le signal reçu RT est très focalisé dans les domaines temporel et spatial. Les focalisations temporelle et spatiale permettent de réduire respectivement l'interférence entre symboles et l'interférence multi-utilisateurs. Dans cette thèse, nous étudions la technique du RT en ULB et son application aux communications haut débit. La validation de la technique du RT dans le laboratoire est réalisée et une étude paramétrique du RT est faite avec différentes configurations multi-antennes (SISO, SIMO, MISO et MIMO). Les résultats montrent que la configuration RT-MIMO présente les meilleures performances. La robustesse du RT est également étudiée dans des environnements non stationnaires. La robustesse du RT est également étudiée dans des environnements non stationnaires. Les résultats suggèrent que si le canal garde une certaine corrélation partielle avec le canal précédent, le RT peut donner une bonne robustesse même si la corrélation totale des canaux est très faible. Bien que les performances obtenues soient meilleures avec des bandes passantes supérieures, la dégradation des performances avec les variations dans le canal reste du même ordre de grandeur. Ensuite, le RT est étudié du point de vue communication. Des validations expérimentales d'une nouvelle technique de modulation et la communication à haut débit sont effectuées pour des canaux denses en trajets multiples. On montre que les performances de TEB en indoor sont meilleures que celles obtenues en chambre réverbérante. Par ailleurs, avec une transmission RT par sous bandes, qui constitue une sorte d'égalisation, le TEB peut être sensiblement amélioré. Enfin, la communication RT multi-utilisateur a été examinée avec des modifications dans le pré-filtre. Le RT modifié donne de meilleures performances que le RT classique ou le RT avec permutation circulaire. Les résultats présentés dans cette thèse suggèrent que le RT en ULB, qui peut être facilement combiné avec les systèmes MIMO, est une approche prometteuse pour les futurs réseaux de locaux et personnels (WLAN et WPAN) sans fils