Localization is one of the key technologies in wireless sensor networks (WSNs), since it provides fundamental support for many location-aware protocols and applications. Constraints on cost and power consumption make it infeasible to equip each sensor node in the network with a global position system (GPS) unit, especially for large-scale WSNs. A promising method to localize unknown nodes is to use mobile anchor nodes (MANs), which are equipped with GPS units moving among unknown nodes and periodically broadcasting their current locations to help nearby unknown nodes with localization. A considerable body of research has addressed the mobile anchor node assisted localization (MANAL) problem. However, to the best of our knowledge, no updated surveys on MAAL reflecting recent advances in the field have been presented in the past few years. This survey presents a review of the most successful MANAL algorithms, focusing on the achievements made in the past decade, and aims to become a starting point for researchers who are initiating their endeavors in MANAL research field. In addition, we seek to present a comprehensive review of the recent breakthroughs in the field, providing links to the most interesting and successful advances in this research field.

/pdf/a-survey-on-mobile-anchor-node-assisted-localization-in-cye1ebv78f.pdf

A Survey on Mobile Anchor Node Assisted Localization in Wireless Sensor Networks

Recent advances in semiconductor laser and light emitting diode devices, able to efficiently operate in the solar blind regime, have brought the oblivious ultraviolet C-Band (UV-C) communications to the fore again. The non-light-of-sight transmission ability as well as the negligible background noise effect are a few of the intriguing benefits offered by this alternative broadband wireless solution. Motivated by such inherent characteristics, the current survey presents a quick and clear entry point to the topic, useful to the researchers who first get confronted with UV-C communications. To better understand the UV-C systems, a brief classification in the introductory section and a trace back to the historical evolution of this technology from its very beginnings to the current trends are provided. Then, several aspects related to the transceiver device characteristics are addressed, whereas particular emphasis is given on channel modeling including the major degrading effects, such as absorption and scattering. Modulation and multiple access schemes as well as other ways for performance enhancement as diversity and encoding techniques are also summarized. Since networking is necessary to overcome the short UV-C range, interference, connectivity, and coverage issues are thoroughly investigated. Finally, the study is concluded with a discussion regarding the challenges needed to make UV-C systems able to meet the high demands of the next generation wireless networks.

A Survey on Ultraviolet C-Band (UV-C) Communications

Anthropogenic climate change is expected to strengthen the vertical wind shears at aircraft cruising altitudes within the atmospheric jet streams. Such a strengthening would increase the prevalence of the shear instabilities that generate clear-air turbulence. Climate modelling studies have indicated that the amount of moderate-or-greater clear-air turbulence on transatlantic flight routes in winter will increase significantly in future as the climate changes. However, the individual responses of light, moderate, and severe clear-air turbulence have not previously been studied, despite their importance for aircraft operations. Here, we use climate model simulations to analyse the transatlantic wintertime clear-air turbulence response to climate change in five aviation-relevant turbulence strength categories. We find that the probability distributions for an ensemble of 21 clear-air turbulence diagnostics generally gain probability in their right-hand tails when the atmospheric carbon dioxide concentration is doubled. By converting the diagnostics into eddy dissipation rates, we find that the ensembleaverage airspace volume containing light clear-air turbulence increases by 59% (with an intra-ensemble range of 43%–68%), light-to-moderate by 75% (39%–96%), moderate by 94% (37%–118%), moderate-to-severe by 127% (30%–170%), and severe by 149% (36%–188%). These results suggest that the prevalence of transatlantic wintertime clear-air turbulence will increase significantly in all aviation-relevant strength categories as the climate changes.

/pdf/increased-light-moderate-and-severe-clear-air-turbulence-in-3mflcyipvn.pdf

Increased light, moderate, and severe clear-air turbulence in response to climate change

A aircraft hazard warning system or method can be utilized to determine a location of turbulence, hail or other hazard for an aircraft. The aircraft hazard warning system can utilize processing electronics coupled to an antenna. The processing electronics can determine an inferred presence of turbulence in response to lightning sensor data, radar reflectivity data, turbulence data, geographic location data, vertical structure analysis data, and/or temperature data. The system can include a display for showing the turbulence hazard and its location.

System and method for turbulence detection

Clear-air turbulence (CAT) is one of the largest causes of weather-related aviation incidents. Here we use climate model simulations to study the impact that climate change could have on global CAT by the period 2050–2080. We extend previous work by analyzing eight geographic regions, two flight levels, five turbulence strength categories, and four seasons. We find large relative increases in CAT, especially in the midlatitudes in both hemispheres, with some regions experiencing several hundred per cent more turbulence. The busiest international airspace experiences the largest increases, with the volume of severe CAT approximately doubling over North America, the North Pacific, and Europe. Over the North Atlantic, severe CAT in future becomes as common as moderate CAT historically. These results highlight the increasing need to improve operational CAT forecasts and to use them effectively in flight planning, to limit discomfort and injuries among passengers and crew.

https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1002/2017GL074618

Global Response of Clear-Air Turbulence to Climate Change

A high-performance airborne UV Rayleigh lidar system was developed within the European project DELICAT. With its forward-pointing architecture, it aims at demonstrating a novel detection scheme for clear air turbulence (CAT) for an aeronautics safety application. Due to its occurrence in clear and clean air at high altitudes (aviation cruise flight level), this type of turbulence evades microwave radar techniques and in most cases coherent Doppler lidar techniques. The present lidar detection technique relies on air density fluctuation measurement and is thus independent of backscatter from hydrometeors and aerosol particles. The subtle air density fluctuations caused by the turbulent air flow demand exceptionally high stability of the setup and in particular of the detection system. This paper describes an airborne test system for the purpose of demonstrating this technology and turbulence detection method: a high-power UV Rayleigh lidar system is installed on a research aircraft in a forward-looking configuration for use in cruise flight altitudes. Flight test measurements demonstrate this unique lidar system being able to resolve air density fluctuations occurring in light-to-moderate CAT at 5 km or moderate CAT at 10 km distance. A scaling of the determined stability and noise characteristics shows that such performance is adequate for an application in commercial air transport.

/pdf/airborne-forward-pointing-uv-rayleigh-lidar-for-remote-clear-3ltcwyl5li.pdf

Airborne forward-pointing UV Rayleigh lidar for remote clear air turbulence detection: system design and performance.

The method involves analyzing a temporal evolution of a clear air turbulence significant index i.e. Richardson number. Safeguard action of an airplane is taken into account when analysis of the temporal evolution of the index and of trajectory of the airplane indicates that the airplane crosses a zone subjected to clear air turbulence, where the airplane occupies a position (P) and horizontally displaced at a speed (V). Flight personnel of the aircraft are informed when analysis of the temporal evolution of the index and of the trajectory indicates that the airplane leaves the zone. An independent claim is also included for a device for protecting an airplane in flight against clear air turbulence.

Method and device for protecting aircraft against clear air turbulence

Clear-air turbulence could be detected at long range using a UV lidar. Because the vertical speed cannot be retrieved from Doppler shift analysis at long range, the turbulence detection is based on the measurement of molecular density fluctuation associated with the turbulent wind. After an optimization of the characteristics of the candidate UV lidar, we present an evaluation of the detection range and of the false alarm rate and missed alarm rate depending on the altitude and vertical velocity root mean square. This study shows that 96% of turbulence with vertical velocity leading to dislodging of unsecured objects in the airplane can be detected at 15 km using a 2 W laser at 355 nm with a false alarm rate of 0.18 per flight hour.

Performance evaluation for long-range turbulence-detection using ultraviolet lidar

We report on a development of a long-range airborne UV
high spectral resolution lidar, intended for the detection
and characterisation of clear air turbulence (CAT). The
detection of turbulence is based on the measurement of
density fluctuations associated with the movement of turbulent
air masses. These density fluctuations are measured
by the variations in the molecular backscatter coefficient
which is determined from the lidar signal by spectrally
separating it from the aerosol backscatter.
After an introduction, we review the CAT detection principle
and describe the lidar system design. We then
present the expected performance of the system and give
an overview on the planned measurement campaign.

/pdf/clear-air-turbulence-detection-and-characterisation-in-the-3jumvbb9rg.pdf

Clear air turbulence detection and characterisation in the delicat airborne lidar project

A high-performance airborne UV Rayleigh lidar system was developed within the European project DELICAT. With its forward-pointing architecture it aims at demonstrating a novel detection scheme for clear air turbulence (CAT) for an aeronautics safety application. Due to its occurrence in clear and clean air at high altitudes (aviation cruise flight level), this type of turbulence evades microwave radar techniques and in most cases coherent Doppler lidar techniques. The present lidar detection technique relies on air density fluctuations measurement and is thus independent of backscatter from hydrometeors and aerosol particles. The subtle air density fluctuations caused by the turbulent air flow demand exceptionally high stability of the setup and in particular of the detection system. This paper describes an airborne test system for the purpose of demonstrating this technology and turbulence detection method: a high-power UV Rayleigh lidar system is installed on a research aircraft in a forward-looking configuration for use in cruise flight altitudes. Flight test measurements demonstrate this unique lidar system being able to resolve air density fluctuations occurring in light-to-moderate CAT at 5 km or moderate CAT at 10 km distance. A scaling of the determined stability and noise characteristics shows that such performance is adequate for an application in commercial air transport.

/pdf/airborne-forward-pointing-uv-rayleigh-lidar-for-remote-clear-3tqenb1c3c.pdf

Hervé Barny

Papers

Airborne forward-pointing UV Rayleigh lidar for remote clear air turbulence detection: system design and performance.

Method and device for protecting aircraft against clear air turbulence

Performance evaluation for long-range turbulence-detection using ultraviolet lidar

Clear air turbulence detection and characterisation in the delicat airborne lidar project

Airborne forward pointing UV Rayleigh lidar for remote clear air turbulence (CAT) detection: system design and performance