Prediction of Satellite Shadowing in Smart Cities with Application to IoT

The combination of satellite direct reception and terrestrial 5G infrastructure is essential to guarantee coverage in satellite based-Internet of Things, mainly in smart cities where buildings can cause high power losses. In this paper, we propose an accurate and fast graphical method for predicting the satellite coverage in urban areas and SatCom on-the-move scenarios. The aim is to provide information that could be useful in the IoT network planning process, e.g., in the decision of how many terrestrial repeaters are really needed and where they should be placed. Experiments show that the shadowed areas predicted by the method correspond almost perfectly with experimental data measured from an Eutelsat satellite in the urban area of Barcelona.Ministerio de Industria, Turismo y Comercio de España TSI-020301-2009-3

Long term evolution of the surface refractivity for arctic regions

YesIn this paper, local meteorological data for a period of 35 years (from 1979 to 2013) from Kuujuaq station have been used to calculate the surface refractivity, N and to estimate the vertical refractivity gradient, dN1, in the lowest atmospheric layer above the ground. Monthly and yearly variations of the mean of N and dN1 are provided. The values obtained are compared with the corresponding values from the ITU maps. The long-term trend of the surface refractivity is also investigated. The data demonstrate that the indices N and dN1 are subject to an evolution which may have significance in the context of climate change (CC). Monthly means of N show an increasing departure from ITU-R values since 1990. Yearly mean values of the dN1 show a progressive decrease over the period of study. Seasonal means of dN1 show a decrease over time, especially for summer. Such a trend may increase the occurrence of super-refraction. However, currently available ITU-R recommendations for microwave link design assume a stationary climate, so there is a need for a new modelling approach

A methodology for precise estimation of rain attenuation on terrestrial millimetre wave links from raindrop size distribution measurements

Attenuation by atmospheric rain is the most significant impairment in millimetre wave frequencies (mmWave). Modern instruments could provide detailed measurements of rain, such as raindrop size distributions (DSDs). The analysis of DSDs could estimate their effects on past or co-located links measurements. This study presents propagation analysis in the mmWave bands using measurements of two terrestrial links working at 26 and 38 GHz carried out in Johor, Malaysia. Statistics obtained have been analysed in detail to extract any excess attenuation. The DSDs provided by a disdrometer have been used to estimate rain attenuation. The derived results show that the estimation can provide reasonable accuracy after extracting the wet antenna effects and having the advantage of the availability of measurements from various types of equipment

Introducing an effect of climate change into globals models of rain fade on telecommunications links

Rain attenuation limits the performance of microwave telecommunication links functioning above approximately 5 GHz. Recent studies have revealed that over the last twenty years the occurrence of rain, at intensities that cause outage on terrestrial links, has experienced a strongly increasing trend in the UK. Globally, the height of rain events has also been observed to increase, which may compound increasing trends in rain fade experienced by Earth-Space communication systems. These climatic changes are almost certainly having significant effect on the performance of existing radio systems, and need to be taken into consideration when planning future systems. The International Telecommunication Union – Radio Section (ITU-R), maintains a set of internationally accepted models for the engineering and regulation of radio systems globally. Although under constant revision, these models assume that atmospheric fading is stationary. This assumption is inherent in the way models are tested.In this project, a method is developed to estimate global trends in one of the most fundamental parameters to the ITU-R models: the one-minute rain rate exceeded for 0.01% of an average year. This method introduces climate change into the ITU-R model of this parameter: Rec. ITU-R P.837. The new model is tested using a method that does not make a stationary climate assumption. Salonen-Poiares Baptista distribution, which is the fundamental method for developing ITU-R Rec. P.837 has been tested using UK Environment Agency data, but no correlations was found between measured annual accumulations and distribution parameters. Nonetheless a link was found between mean annual total precipitations (MT) and rain exceeded at larger time percentages such as; 0.1% and 1%

Analysis and implementation of prediction models for the design of fixed terrestrial point-to-point systems

Cataloged from PDF version of article.In this study, propagation link analysis and implementation of prediction models for the design of fixed terrestrial point-to-point systems are aimed. Different propagation models in the literature are examined as case studies and comparisons are made. Rec. ITU-R P.530 Model is analyzed in detail. The worst month link availability is investigated for terrestrial microwave LOS/NLOS radio links operating in NATO Band 3+ (1350-2690 MHz) and NATO Band 4 (4400- 5000 MHz) frequency bands. The calculation of Bullington model of diffraction loss is extended for LOS path case and determination of reflection points on the terrain profile is improved. Several terrestrial microwave LOS/NLOS radio links are analyzed using the propagation parameters such as TX (transmitter) and RX (receiver) station coordinates, path length, frequency, antenna heights above ground level, antenna gains, polarization, radio refractivity gradient, time percentage, target SNR (Signal to Noise Ratio), bandwidth, digital terrain elevation and climate data. The calculation of the received power with the effect of the ground reflection is developed to calculate the fade margin in the defined microwave LOS/NLOS radio links. Received power is calculated by taking into consideration the attenuation due to rain and atmospheric gases, diffraction loss and the effect of multipath fading due to reflection. The validity of the implementation of link analysis is justified by comparison with the commercial ATDI ICS telecom software and the measurement data existing in the literature over sample microwave LOS/NLOS radio links.Göktaş, PolatM.S

Model fitting to account for the weather s impact on wireless propagation at 2.4 GHz

[EN] Usually, users of outdoor wireless local area networks have a good quality of experience and they do not have any complaint about its performance. However, under certain weather conditions, their performance decreases due to influence of meteorological variables on wireless signal propagation and users notice this deterioration through disconnections, delays, data loss, etc. This paper presents the research carried out in order to approach the unsuccessful transmission of different frames at MAC layer from the weather conditions at run time by using mathematic models.This work has been supported by the Vice-Rectorate for Research, Innovation and Transfer through the programme FPI-UPV. The authors would like to thank Borja Opticos and Azimut Electronics for their support.Bri Molinero, D.; Garcia, M.; Lloret, J.; Ramos, F. (2017). Model fitting to account for the weather s impact on wireless propagation at 2.4 GHz. National Academy Science Letters. 40(2):127-130. https://doi.org/10.1007/s40009-016-0520-7S127130402Bianchi C, Meloni A (2007) Natural and man-made terrestrial electromagnetic noise: an outlook. Ann Geophys 50:435–445International Telecommunications Union (2013) Recommendation ITU-R P.676-10: attenuation by atmospheric gasesInternational Telecommunications Union (2013) Recommendation ITU-R P.530-15: propagation data and prediction methods required for the design of terrestrial line-of-sight systemsBri D, Fernández-DiegoM Garcia M, Ramos F, Lloret J (2012) How the weather impacts on the performance of an outdoor WLAN. IEEE Commun Lett 6:1184–1187Bri D, Ramos F, Lloret J, Garcia M (2012) The influence of meteorological variables on the performance of outdoor wireless local area networks. In: IEEE international conference on communications, OttawaBri D, Sendra S, Coll H, Lloret J (2010) How the atmospheric variables affect to the WLAN Datalink layer parameters. In: Advanced international conference on telecommunications, BarcelonaChu CH, Chen YM, Huang YT, Carvalho R, Hsu CC, Chen LJ (2014) Measurement of long-distance Wi-Fi connections: an empirical study. In: IEEE international conference on communications, SydneyOhshima K, Hara H, Hagiwara Y, Terada M (2012) Field investigation of the radio transmission performance and distance in an environmental wireless sensor network. In: International conference on information networking, BaliNadeem F, Leitgeb E, Koudelka O, Kandus TJG (2008) Comparing the rain effects on hybrid network using optical wireless and GHz links. In: International conference on emerging technologies, RawalpindiSchmidt M, Lipson H (2009) Distilling free-form natural laws from experimental data. Science 324:81–85Schmidt M, Lipson H (2013) Eureqa (Version 0.98 beta) [Software] Available: www.nutonian.comBri D, Garcia M, Lloret J, Misic J (2015) Measuring the weather’s impact on MAC layer over 2.4 GHz outdoor radio links. Measurement 61:221–233Yu F, Biswas S (2012) MAC protocol switching: a novel tool for performance adaptation in wireless sensor networks. Netw Protoc Algor 4:69–8

Multipath propagation characterization for terrestrial mobile and fixed microwave communications

Multipath propagation is a key issue studied throughout this thesis, and it causes dispersions in delay, frequency and spatial domains. These are dominant phenomena in both terrestrial mobile and fixed wideband communications. In this thesis, multipath propagation mechanisms including diffraction, refraction, reflection and scattering are studied when radio waves interact with dielectric and metallic objects, or an atmospheric duct. Measurements were also performed for empirical modelling and validation of the theoretical work carried out in this thesis. By using physical optics (PO) method, the attenuation by double knife edges with ground reflections is solved for the first time under a general formula of the attenuation by multiple knife edges with ground reflections derived in this thesis, and some important and interesting conclusions are obtained. The attenuations by curvilinear-topped obstacles and by multiple flat-topped obstacles are also presented in closed forms. The results are the simplest and easiest ones available now, and they can be applied for field strength predictions both in mobile and fixed microwave communications. Based on three-ray (direct, reflected and super-refracted) and two-ray (direct and super-refracted) multipath models for plane and spherical earth, respectively, frequency selective fading (FSF) and depolarization due to clear air are studied by simulations and experiments for terrestrial line-of-sight (LOS) microwave links and dual-polarized communication systems. Novel simulation methods have been introduced and applied based on the fact that the amplitudes and excess delays of the rays are functions of the (modified) refractive index gradients which are random variables with exponential and normal distributions inside and outside the duct in lower atmosphere, respectively. Some important empirical or semi-empirical models and parameters are presented at 5 GHz based on large amount of measured data in indoor and outdoor environments. The results include path loss models, excess delay and rms delay spread, spatial and frequency correlations, window (sector) length of averaging fast fading components, path number distribution, and tapped-delay-line (TDL) channel models. These empirical or semi-empirical parameters and models are the latest results achieved at 5 GHz, and they are of great importance in designing of future wireless local area networks (WLAN), especially the TDL models are developed for the first time in this frequency band. Using a general autocorrelation function derived in this thesis for three-dimensional (3-D) scattering environments, a novel theoretical modelling method is developed to study the propagation mechanisms of different types of Doppler spectra observed in measurements. The 3-D autocorrelation function is connected to the probability density functions (PDF) of the angles of arrival (AoAs) of the scattered waves and the antenna radiation patterns in the azimuth and elevation planes. This is a new work which tries to define and explain the physical reasons of 3-D Doppler spectra from propagation point of view. A new computer simulation method for wideband 3-D received signal level in an urban environment is developed under the general assumptions of the distributions for path number, amplitude, excess delay etc. This simulation method can provide detailed fading characteristics for wideband mobile communications in a specific urban environment.reviewe

Designing and Implementing Future Aerial Communication Networks

Providing "connectivity from the sky" is the new innovative trend in wireless communications. High and low altitude platforms, drones, aircrafts and airships are being considered as the candidates for deploying wireless communications complementing the terrestrial communication infrastructure. In this article, we report the detailed account of the design and implementation challenges of an aerial network consisting of LTE Advanced (LTE-A) base stations. In particular, we review achievements and innovations harnessed by an aerial network composed of Helikite platforms. Helikites can be raised in the sky to bring Internet access during special events and in the aftermath of an emergency. The trial phase of the system mounting LTE-A technology onboard Helikites to serve users on the ground showed not only to be very encouraging but that such a system could offer even a longer lasting solution provided that inefficiency in powering the radio frequency equipment in the Helikite can be overcome.Comment: IEEE Communications Magazine 201