There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Stable non-Gaussian random processes , by G. Samorodnitsky and M. S. Taqqu. Pp. 632. £49.50. 1994. ISBN 0-412-05171-0 (Chapman and Hall).

The adoption of a reconfigurable intelligent surface (RIS) for downlink multi-user communication from a multi-antenna base station is investigated in this paper. We develop energy-efficient designs for both the transmit power allocation and the phase shifts of the surface reflecting elements subject to individual link budget guarantees for the mobile users. This leads to non-convex design optimization problems for which to tackle we propose two computationally affordable approaches, capitalizing on alternating maximization, gradient descent search, and sequential fractional programming. Specifically, one algorithm employs gradient descent for obtaining the RIS phase coefficients, and fractional programming for optimal transmit power allocation. Instead, the second algorithm employs sequential fractional programming for the optimization of the RIS phase shifts. In addition, a realistic power consumption model for RIS-based systems is presented, and the performance of the proposed methods is analyzed in a realistic outdoor environment. In particular, our results show that the proposed RIS-based resource allocation methods are able to provide up to 300% higher energy efficiency in comparison with the use of regular multi-antenna amplify-and-forward relaying.

Reconfigurable Intelligent Surfaces for Energy Efficiency in Wireless Communication

This paper reviews some main results and progress in distributed multi-agent coordination, focusing on papers published in major control systems and robotics journals since 2006. Distributed coordination of multiple vehicles, including unmanned aerial vehicles, unmanned ground vehicles, and unmanned underwater vehicles, has been a very active research subject studied extensively by the systems and control community. The recent results in this area are categorized into several directions, such as consensus, formation control, optimization, and estimation. After the review, a short discussion section is included to summarize the existing research and to propose several promising research directions along with some open problems that are deemed important for further investigations.

/pdf/an-overview-of-recent-progress-in-the-study-of-distributed-1xnb6e12se.pdf

An Overview of Recent Progress in the Study of Distributed Multi-Agent Coordination

This article reviews some main results and progress in distributed multi-agent coordination, focusing on papers published in major control systems and robotics journals since 2006. Distributed coordination of multiple vehicles, including unmanned aerial vehicles, unmanned ground vehicles and unmanned underwater vehicles, has been a very active research subject studied extensively by the systems and control community. The recent results in this area are categorized into several directions, such as consensus, formation control, optimization, task assignment, and estimation. After the review, a short discussion section is included to summarize the existing research and to propose several promising research directions along with some open problems that are deemed important for further investigations.

An Overview of Recent Progress in the Study of Distributed Multi-agent Coordination

Gorce J-M, Arditi M, Schneider M. Influence of bubble size distribution on the echogenicity of ultrasound contrast agents: A study of SonoVue™. Invest Radiol 2000;35:661–671.RATIONALE AND OBJECTIVES.To study the relative contributions of different bubble size classes to SonoVue™’s echogenicity in fu

Influence of bubble size distribution on the echogenicity of ultrasound contrast agents: a study of SonoVue.

This paper focuses on the the emerging transmission technologies dedicated to IoT networks. We first analyze the classical cellular network technologies when taking into account the IoT requirements, and point out the need of dedicated technologies for IoT. Then, we present the PHY and MAC layers of the technologies that are already deployed, or likely to be deployed: UNB by SigFox, CSS by LoRa T M , Weighless, and RPMA by Ingenu. We then compare their performances to highlight their pros and cons. Finally, we discuss on the open research challenges that still need to be addressed.

/pdf/dedicated-networks-for-iot-phy-mac-state-of-the-art-and-tekb0ysg6s.pdf

Dedicated networks for IoT : PHY / MAC state of the art and challenges

Relay attacks pose a real threat to the security of wireless communications. Distance bounding protocols have been designed to thwart these attacks. In this paper, we study the way to adapt distance bounding protocols to time-hopping ultra wide band (TH-UWB) radios. Two protocols are proposed which are based on the milestones of the TH-UWB radio: the time-hopping sequence and the mapping code. The security and the different merits of those protocols are analyzed.

Distance Bounding Protocols on TH-UWB Radios

The multiresolution frequency domain parflow (MR-FDPF) approach is applied to radio wave propagation in indoor environments. This method allows for a better understanding of indoor propagation and hence greatly assists the development of WiFi-like network planning tools. The efficiency of such wireless design tools is strongly impacted by the quality of the coverage predictions which have to be estimated with a limited computational load. The usual approaches are based either on an empirical modeling relying on measurement campaigns or on geometrical optics leading to ray-tracing. While the former approach suffers from a lack of accuracy, the later one needs to balance accuracy with computational load requirements. The new approach proposed herein is based on a finite difference formalism, i.e., the transmission line matrix (TLM). Once the problem is developed in the frequency domain, the linear system thus obtained is solved in two steps: a pre-processing step which consists of an adaptive MR (multigrid) pre-conditioning and a propagation step. The first step computes a MR data structure represented as a binary tree. In the second step the coverage of a point source is obtained by up-and-down propagating through the binary tree. This approach provides an exact solution for the linear system whilst significantly reducing the computational complexity when compared with the time domain approach

Deterministic Approach for Fast Simulations of Indoor Radio Wave Propagation

Recent years have witnessed a tremendous growth of research in the field of wireless systems and networking protocols. Consequently, simulation has appeared as the most convenient approach for the performance evaluation of such systems and several wireless network simulators have been proposed in recent years. However, the complexity of the wireless physical layer (PHY) induces a clear tradeoff between the accuracy and the scalability of simulators. Thereby, the accuracy of the simulation results varies drastically from one simulator to another. In this paper, we focus on this tradeoff and we investigate the impact of the physical layer modeling accuracy on both the computational cost and the confidence in simulations. We first provide a detailed discussion on physical layer issues, including the radio range, link and interference modeling, and we investigate how they have been handled in existing popular simulators. We then introduce a flexible and modular new wireless network simulator, called WSNet. Using this simulator, we analyze the influence of the PHY modeling on the performance and the accuracy of simulations. The results show that the PHY modeling, and in particular interference modeling, can have a significant impact on the behavior of the evaluated protocols at the expense of an increased computational overhead. Moreover, we show that the use of realistic propagation models can improve the simulation accuracy without inducing a severe degradation of scalability.

https://ensiwiki.ensimag.fr/images/5/53/JeromeGINSS_ref6.pdf

Jean-Marie Gorce

Papers

Influence of bubble size distribution on the echogenicity of ultrasound contrast agents: a study of SonoVue.

Dedicated networks for IoT : PHY / MAC state of the art and challenges

Distance Bounding Protocols on TH-UWB Radios

Deterministic Approach for Fast Simulations of Indoor Radio Wave Propagation

Impact of the Physical Layer Modeling on the Accuracy and Scalability of Wireless Network Simulation