This article is part of an exclusive IEEE Journal Watch series in partnership with IEEE Xplore.
As the telecommunications industry gradually rolls out 5G networks around the world, researchers are beginning to focus on next-generation 6G network technologies. His one vision for 6G is to use new cellular frequencies ranging from 100 gigahertz to terahertz. The problem with this vision is that gases in the atmosphere absorb these waves. This means that signals transmitted on these frequencies can become useless after just a few meters.
But why not turn that disadvantage on its head and use it to address pressing global problems? In a new paper published in the journal Oct. 6. IEEE networkresearchers show how future 6G networks can be used to measure emissions that harm both the climate and human health.
“If a terahertz signal is being absorbed, we can tell which molecules are absorbing the signal,” says Josep Jornet, a professor of electrical and computer engineering at Northeastern University in Boston. “So we can build an infrastructure that turns the problem of signal absorption into an opportunity to learn what gases are present in the air and in what concentrations.”
“What we are proposing in this paper is radio spectroscopy.” —Josep Gionet, Northeastern University
Sashitharan Balasubramaniam, a computing professor at the University of Nebraska-Lincoln, said climate change and air pollution are becoming increasingly urgent issues as emissions from industrial and agricultural sectors increase. talk. At the same time, he also has a vision for a 6G network operating in the sub-terahertz and terahertz range, which is ideal for gas detection. “This guy makes sense to combine the two.”
Different molecules absorb different electromagnetic radiation frequencies depending on their molecular structure. For example, carbon dioxide, ammonia, and ozone all have unique absorption properties.
Spectroscopy, the technique used to decipher the molecular makeup of chemicals, is based on that fact. This involves irradiating a chemical or biological sample with a broad frequency spectrum, measuring the absorption at each frequency, and analyzing the series of absorption peaks that appear in the spectrometer reading.
“What we are proposing in this paper is radio spectroscopy,” says Jornet. He, Balasubramaniam, and their colleagues used a radio developed at Northeastern. The radio operates at frequencies between 100 and 300 GHz, with enough power to transmit data over tens of meters, and at lower power for distances up to 2 kilometers. “There are radios that can reach up to 1 to 1.1 terahertz. But the power we have at those frequencies is very low, probably enough for about a foot.”
The researchers compared the absorption profiles of different gases obtained from an online molecular absorption database with the sensing data of different gas samples from a sub-THz transceiver in sensing mode. He used two techniques to measure radiation absorption. One is simple path loss data analysis, which measures the signal loss between the transmitter and receiver. The other is the power spectral density approach, which measures the power of a signal versus frequency. Machine learning algorithms were then used to identify absorption patterns and matched against online databases.
They were able to accurately detect the greenhouse gases carbon dioxide, methane, and nitrous oxide. Sulfur dioxide is a byproduct of chemical factories and is harmful to health. Other toxic gases such as ammonia and ozone. Balasubramaniam says the method can also detect relevant gases in mixtures. “What’s interesting is that if you mix different gases in different proportions and collect enough data to look at the patterns, you can pinpoint those few gases even as their distances and concentrations vary.”
6G networks are still years away. But there would be economic benefits to using the same infrastructure for both communications and sensing, said Mehmet Kan, a professor of computing at the University of Nebraska-Lincoln and another co-author of the paper. Vran says. Adding gas sensing capabilities to a terahertz infrastructure simply requires a layer of signal processing software at a small cost to the communications provider. It would also benefit the agricultural sector, where monitoring and reporting of harmful emissions from livestock facilities is being discussed.
“If the regulations come into effect, it will put a huge burden on producers,” Vran said. “Some of the gas sensors that this work replaces are very expensive. However, with terahertz systems like this, the same infrastructure can be used for multiple purposes, which reduces costs and reduces deployment costs. rate will improve.”
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