Article

Channel Modeling and Performance Analysis of Airplane-Satellite Terahertz Band Communications

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Abstract

Wireless connectivity in airplanes is becoming more important, demanded, and common. One of the largest bottlenecks with the in-flight Internet is that the airplane is far away from both the satellites and the ground base stations during most of the flight time. Maintaining a reliable and high-rate wireless connection with the airplane over such a long-range link thus becomes a challenge. Microwave frequencies allow for long link distances but lack the data rate to serve up to several hundreds of potential onboard customers. Higher bands in the millimeter-wave spectrum (30 GHz - 300 GHz) have, therefore, been utilized to overcome the bandwidth limitations. Still, the per-user throughput with state-of-the-art millimeter-wave systems is an order of magnitude lower than the one available with terrestrial wireless networks. In this paper, we take a step further and study the channel characteristics for the terahertz band (THz, 0.3 THz - 10 THz) in order to map the feasibility of this band for aviation. We first propose a detailed channel model for aerial THz communications taking into account both the non-flat Earth geometry and the main features of the frequency-selective THz channel. We then apply this model to estimate the characteristics of aerial THz links in different conditions. We finally determine the altitudes where the use of airplane-to-satellite THz connection becomes preferable over the airplane-to-ground THz link. Our results reveal that the capacity of the airborne THz link may reach speeds ranging from 50 - 150 Gbps, thus enabling cellular-equivalent data rates to the passengers and staff during the entire flight.

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... 0.22 THz frequency bands for the next generation of terrestrial wireless communications and inter-satellite communications, respectively (You et al., 2021). At present, the research of THz satellite communication mainly focuses on satellite-to-ground (S2E) or satellite-to-aircraft (S2A), mainly modeling molecular absorption and atmosphere (Balal & Pinhasi, 2018;Blaunstein et al., 2010;Kokkoniemi et al., 2021;Suen et al., 2017). This study analyzes the satellite-to-satellite (S2S) link, focusing on the impact of multipath effects on the channel. ...
... In reference (Jornet & Akyildiz, 2011), the authors analyze the total noise in the THz band including the molecular absorption noise and the antenna noise. The atmospheric noise and the thermal noise at the receiver between airplane and satellite are introduced in reference ( Kokkoniemi et al., 2021). Some authors analyze the white Gaussian noise, the system noise (Suen et al., 2017). ...
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A time-varying multi-ray channel model suitable for inter-satellite link simulation and performance evaluation is proposed aiming at the characteristics of the space communication environment. This model analyzes the propagation process and multi-dimensional characteristics of the terahertz (THz) waves between the satellite and the space station. The receiving environment of the space station is constantly changing due to the rotation of the station's solar panels with the sun and the relative motion between the station and the satellite. To predict critical multipath events for a specific communication configuration, the method of ray tracing, which is combined with the consistent orbiting theory and geometric orbital theory, is used to analyze the channel characteristics of different inter-satellite links at the THz band (220 GHz). The research content includes the path loss model, the multipath statistics, the small scale fading and some other related channel characteristics. The space THz multi-dimensional time domain, space domain, and frequency domain characteristics are obtained by studying the structural characteristics of the space station and space environment, the law of position change between the space station and the satellite, and the relative motion between the satellite and the space station. The study on the characteristics of the THz time-varying channel provides a reference for the prediction and planning of THz wave propagation in future inter-satellite links.
... For example, D-band (above 100 GHz) active electronically steerable antennas have been developed recently [180]. There are studies on terahertz technology such as [181] in which the authors show that the capacity of the satellite-to-airplane THz link may reach speeds ranging from 50-150 Gbps, thus enabling cellular-equivalent data rates to the passengers and staff during the entire flight. ...
... [32], [174], [181], [190] Cyber security in the quantum era ...
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During the New Space era small countries are also becoming more important players in the space business. While the space activities are rapidly increasing, it is important to make operations in a sustainable and safe way in order to preserve satellite services for future generations. In this survey paper, we discuss the multi-layer networking approaches in the 6G era specifically from the sustainability perspective. We review the most important regulations and international guidelines and revisit a three-dimensional architecture vision to support the sustainability target for a variety of application areas. We then classify and discuss space safety paradigms that are important sustainability enablers of future satellite communications. These include space traffic management, debris detection, environmental impacts, spectrum sharing, and cyber security aspects. The paper discusses also advances towards a planned European connectivity constellation that could become a third flagship infrastructure along with Galileo and Copernicus systems. Finally, we define potential research directions towards the 2030s.
... Recently, a THz channel model for aerial communications was first proposed in [112], since space-airground integrated network captures researchers' attention increasingly [113]. It is noted that the authors in [112] consider the frequency-selective THz channel and the non-flat Earth geometry, and the numerical results indicate that the channel capacity may be up to 120 Gbit/s in this case. ...
... Recently, a THz channel model for aerial communications was first proposed in [112], since space-airground integrated network captures researchers' attention increasingly [113]. It is noted that the authors in [112] consider the frequency-selective THz channel and the non-flat Earth geometry, and the numerical results indicate that the channel capacity may be up to 120 Gbit/s in this case. ...
Article
For the sake of meeting the demand of data rates at terabit (Tbit) per second scale in future networks, the terahertz (THz) band is widely accepted as one of the potential key enabling technologies for next generation wireless communication systems. With the progressive development of THz devices, regrading THz communications at system level is increasing crucial and captured the interest of plenty of researchers. Within this scope, THz channel modeling serves as an indispensable and fundamental element. By surveying the latest literature findings, this paper reviews the problem of channel modeling in the THz band, with an emphasis on molecular absorption loss, misalignment fading and multipath fading, which are major influence factors in the THz channel modeling. Then, we focus on simulators and experiments in the THz band, after which we give a brief introduction on applications of THz channel models with respects to capacity, security, and sensing as examples. Finally, we discuss some key issues in the future THz channel modeling.
... There are also some research instances in radio astronomy, modeling of high-capacity airplanes-to-satellite, and Earth-satellite communication links in the THz band. 4,[9][10][11][12] Among them, the work 11 presented a noise analysis model due to amplitude and phase fluctuations in the 33-to 960-GHz band using large atacama large millimeter/submillimeter array (ALMA)-based THz detectors. Our previous work 4 modeled a 10-Gbps/GHz GEO-ES THz link in the low-and mid-latitude regions within the 100-to 500-GHz band by considering different weather conditions. ...
... Moreover, the work 10 suggested that a Tbps geostationary satellite-to-Earth-station (GEO-ES) link is possible using large aperture dish array and space observatory optics in the above 500-GHz band, while establishing ALMA sites in northern Chile, Goldsone, and High Unitas in the USA, as well as some dry locations in China such as Tangulla Station, and Ali Shiquanhe in Tibet. Kokkoniemi et al. 12 modeled a 40-to 60-Gbps THz link for airplane-to-LEO and LEO-toairplane in the 300-GHz band. Taherkhani et al. 13 showed a channel model in the 300-GHz band under strong turbulence condition and note that 15-dBi more gain per antenna is required to achieve a threshold bit-error-rate (BER) over 1-km link under the standard atmospheric conditions. ...
Article
We present a comprehensive model to study the atmospheric channel impairments within the low-and mid-latitude regions for the geostationary satellite-to-Earth-station (GEO-ES) links in the selective terahertz (THz) bands (140, 220, 345, and 410 GHz), in terms of dispersion, turbulence loss, as well as atmospheric attenuation in different seasons. Our analysis shows that dispersion effect in the channel above 300 GHz causes serious performance degradation in the low-latitude (LL) regions compared to mid-latitude regions, resulting in a need for a higher signal-to-noise-ratio (SNR) to achieve an expected bit-error-rate of, e.g., 10 − 3. On the other hand, the GEO-ES link budget requirement becomes more stagnant due to turbulence loss in the LL regions compared to mid-latitude regions. In addition, seasonal variations investigation indicates that an improvement of 2- to 5-dB SNR can be obtained in the mid-latitude regions during winter. The influence of channel impairments on 16-QAM performance in an opto-electronic THz link with slant path geometry is analyzed as an example, and our results suggest that GEO-ES links operating in the 140- and 220-GHz bands are more foreseeably realistic in the low- and mid-latitude regions, whereas the 345-GHz band also shows a good potential for the future Earth-satellite THz links with high data capacity.
... The molecular absorption coefficient depends on the atmospheric temperature, T , and pressure, P , as well as the relative humidity, ϕ, and can be evaluated by leveraging the radiative transfer theory and the measured data provided in the high resolution transmission molecular absorption (HITRAN) database [65], as described in [8], [66], [67]. Alternative approaches to extract the molecular absorption coefficient by means of analytical formulas are provided in [68]- [70]. ...
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This contribution focuses on extracting the theoretical framework for the assessment and evaluation of the joint effect of rain, beam misalignment and hardware imperfections at long-range outdoor terahertz (THz) wireless systems. In this direction, we first report an appropriate system model for outdoor THz wireless systems that take into account the impact of different design parameters, including antenna gain and transceivers hardware imperfections, atmospheric conditions, such as rain, and parameters, like temperature, humidity and pressure, as well as stochastic beam misalignment that can be caused by thermal expansion, dynamic wind loads and/or weak earthquakes. For this model, we extract novel closed-form expressions for the probability density and cumulative distribution functions of the THz wireless channel that captures the impact of geometric loss, beam misalignment and rain attenuation. We capitalized the aforementioned expressions by presenting closed-form formulas for the outage probability and achievable throughput of the system. Finally, we document an analytical policy that returns the optimal transmission spectral efficiency that maximizes the achievable throughput. INDEX TERMS Hardware imperfections, misalignment fading, outage probability, performance analysis, radio frequency chain imperfections, rain attenuation, statistical characterization, throughput, terahertz wireless systems, wireless fiber extender.
... By contrast, in the stratospheric region with altitude above 10 km, water vapor almost disappears and oxygen dominates the molecular absorption. When altitude further increases from the stratosphere region to the vacuum space, there is no molecular absorption effect anymore, and the molecular absorption effect is much less significant than that in terrestrial and troposphere regions [12]. ...
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Communications in the terahertz band (THz) (0.1--10~THz) have been regarded as a promising technology for future 6G and beyond wireless systems, to overcome the challenges of evergrowing wireless data traffic and crowded spectrum. As the frequency increases from the microwave band to the THz band, new spectrum features pose unprecedented challenges to wireless communication system design. The molecular absorption effect is one of the new THz spectrum properties, which enlarges the path loss and noise at specific frequencies. This brings in a double-edged sword for THz wireless communication systems. On one hand, from the data rate viewpoint, molecular absorption is detrimental, since it mitigates the received signal power and degrades the channel capacity. On the other hand, it is worth noticing that for wireless security and covertness, the molecular absorption effect can be utilized to safeguard THz communications among users. In this paper, the features of the molecular absorption effect and their impact on the THz system design are analyzed under various scenarios, with the ultimate goal of providing guidelines to how better exploit this unique THz phenomenon. Specifically, since the molecular absorption greatly depends on the propagation medium, different communication scenarios consisting of various media are discussed, including terrestrial, air and space, sea surface and nano-scale communications. Furthermore, two novel molecular absorption enlightened secure and covert communication schemes are presented, where the molecular absorption effect is utilized as the key and unique feature to boost security and covertness.
... IV-B1 reveal the shortage of the commonly used deterministic and stochastic channel models for THz communications. These issues motivate the integration of deterministic and statistical modeling approaches to reach both high efficiency and accuracy un- [140], terrestrial and satellite spectrum sharing systems [134], airplane-satellite [165], as well as intersatellite links [166]. This suggests that the outdoor and mobile THz channels have drawn remarkable research attention, while further investigation of non-stationary and outdoor scenarios still remain open problems. ...
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... In (47), f and c stand for the transmission frequency and the speed of light, respectively, while G s , R i and G d represent the S transmission antenna gain, the i−th RIS reflection coefficient, and the D reception antenna gain, respectively. Likewise, in (48), κ(f ) denotes the molecular absorption coefficient, which depends on the atmospheric temperature (T ), pressure (p), as well as relative humidity (φ) and can be evaluated as in [92], [93] and [94, eq. (8)] ...
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This paper describes a computer-accessible catalog of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10 000 GHz (i.e. wavelengths longer than 30 μm). The catalog can be used as a planning guide or as an aid in the identification and analysis of observed spectral lines in the interstellar medium, the Earth’s atmosphere, and the atmospheres of other planets. The information listed for each spectral line includes the frequency and its estimated error, the intensity, the lower state energy, and the quantum number assignment. The catalog is continuously updated and at present has information on 331 atomic and molecular species and includes a total of 1 845 866 lines. The catalog has been constructed by using theoretical least-squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariance. Future versions of this catalog will add more atoms and molecules and update the present listings as new data appear. The catalog is available on-line via anonymous FTP at spec.jpl.nasa.gov and on the world wide web at http: //spec.jpl.nasa.gov.
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The updated 2009 edition of the spectroscopic database GEISA (Gestionet Etudedes Informations Spectroscopiques Atmospheriques ; Management and Study of Atmospheric Spectroscopic Information) is described in this paper. GEISA is a computer-accessible system comprising three independent sub-databases devoted, respectively, to: line parameters, infrared and ultraviolet/visible absorption cross-sections, microphysical and optical properties of atmospheric aerosols. In this edition, 50 molecules are involved in the line parameters sub-database, including 111 isotopologues, for a total of 3,807,997 entries, in the spectral range from 10-6 to 35,877.031cm-1. GEISA, continuously developed and maintained at LMD (Laboratoirede Meteorologie Dynamique, France) since 1976, is implemented on the IPSL/CNRS(France) ‘‘Ether’’ Products and Services Centre WEB site (http://ether.ipsl.jussieu.fr), where all archived spectroscopic data can be handled through general and user friendly associated managements of software facilities. More than 350 researchers are registered for online use of GEISA.
Article
The electromotive force due to thermal agitation in conductors is calculated by means of principles in thermodynamics and statistical mechanics. The results obtained agree with results obtained experimentally.
Article
Since its first publication in 1973, the HITRAN molecular spectroscopic database has been recognized as the international standard for providing the necessary fundamental spectroscopic parameters for diverse atmospheric and laboratory transmission and radiance calculations. There have been periodic editions of HITRAN over the past decades as the database has been expanded and improved with respect to the molecular species and spectral range covered, the number of parameters included, and the accuracy of this information. The 1996 edition not only includes the customary line-by-line transition parameters familiar to HITRAN users, but also cross-section data, aerosol indices of refraction, software to filter and manipulate the data, and documentation. This paper describes the data and features that have been added or replaced since the previous edition of HITRAN. We also cite instances of critical data that are forthcoming.
Article
In this short note, a misinterpretation of the Voigt line profile is pointed out, which is in several popular textbooks of atmospheric physics. The correct interpretation is given based on mathematical and physical arguments, as well as numerical verification.
Article
The microwave attenuation and noise temperature effects of clouds can result in serious degradation of telecommunications link performance, especially for low-noise systems presently used in deep-space communications. Although cloud effects are generally less than rain effects, the frequent presence of clouds will cause some amount of link degradation a large portion of the time. This paper presents a general review of cloud types and their water particle densities, attenuation and noise temperature calculations, and basic link signal-to-noise ratio calculations. Tabular results of calculations for 12 different cloud models are presented for frequencies in the range 10-50 GHz. Curves of average-year attenuation and noise temperature statistics at frequencies ranging from 10 to 90 GHz, calculated from actual surface and radiosonde observations, are given for 15 climatologically distinct regions in the contiguous United States, Alaska, and Hawaii. Nonuniform sky cover is considered in these calculations.
Short-range ultra-broadband terahertz communications: Concepts and perspectives
  • R Piesiewicz
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  • D Mittleman
  • M Koch
  • J Schoebel
  • T Krner
R. Piesiewicz, T. Kleine-Ostmann, N. Krumbholz, D. Mittleman, M. Koch, J. Schoebel, and T. Krner, "Short-range ultra-broadband terahertz communications: Concepts and perspectives," IEEE Antennas and Propagation Magazine, vol. 49, no. 6, pp. 24-39, 2007.
Three-dimensional angle of arrival estimation in dynamic indoor terahertz channels using a forwardbackward algorithm
  • B Peng
  • T Krner
B. Peng and T. Krner, "Three-dimensional angle of arrival estimation in dynamic indoor terahertz channels using a forwardbackward algorithm," IEEE Transactions on Vehicular Technology, vol. 66, no. 5, pp. 3798-3811, 2017.
The am atmospheric model
  • S Paine
S. Paine, "The am atmospheric model," Smithsonian Astrophysical Observatory, Tech. Rep. 152, 2012.
Recommendation P.838-3, Specific attenuation model for rain for use in prediction methods, International Telecommunication Union Radiocommunication Sector Std
  • Itu-R
ITU-R (2005) Recommendation P.838-3, Specific attenuation model for rain for use in prediction methods, International Telecommunication Union Radiocommunication Sector Std.
Recommendation P.840-6, Attenuation due to clouds and fog, International Telecommunication Union Radiocommunication Sector Std
  • Itu-R
ITU-R (2013) Recommendation P.840-6, Attenuation due to clouds and fog, International Telecommunication Union Radiocommunication Sector Std.
On the shape of collisionbroadened lines
  • J H Van Vleck
  • V F Weisskopf
J. H. Van Vleck and V. F. Weisskopf, "On the shape of collisionbroadened lines," Rev. Mod. Phys., vol. 17, no. 2-3, pp. 227-236, 1945.
U.s. standard atmosphere 1976
"U.s. standard atmosphere 1976," NASA, Tech. Rep., 1976. [36] "NASA EarthData GES DISC." [Online].