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

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 highrate wireless connection with the airplane over such a longrange 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 millimeterwave 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.Index Terms-Airplane communications, satellite communications, THz channel modeling, THz communications I. INTRODUCTION T ODAY, terahertz (THz, 0.3 THz-3 THz) communication is widely considered to be one of the next frontiers for future wireless systems. Data transmission over the THz band offers at least an order of magnitude higher rates than emerging millimeter-wave (mmWave, 30 GHz-300 GHz)

Molecular Absorption Effect: A Double-edged Sword of Terahertz Communications

“…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].…”

Terahertz-Band Near-Space Communications: From a Physical-Layer Perspective

“…This induces additional frequencyselectivity to the propagation channel between NSPS and aerial platforms. Also note that, the traditional terrestrial modeling for molecular absorption loss based on homogeneous assumption of the transmission medium, is no longer valid for THz-NS-COM due to inhomogenity of the highaltitude atmosphere, as stated above [11]. Hence, mathematical modeling of molecular absorption loss needs substantial modification, which should be a function of transmission distance, center frequency, and the atmospheric temperature and pressure curves across different altitudes.…”

“…Aside from signal attenuation, the molecular absorption phenomenon also generates colored noise components, termed as molecular absorption noise, which originates from black-body radiation of the atmosphere. The characteristics of such ambient noise depend on the resonant frequencies of different types of atmospheric molecules, which can be modeled by the antenna brightness temperature following the Rayleigh-Jeans law or Planck's law [11].…”

THz channel modeling: Consolidating the road to THz communications

“…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.…”