How Curved Terahertz Waves Could Revolutionize Wireless Communications

In a breakthrough that could help revolutionize wireless communications, researchers unveiled a novel way to manipulate terahertz waves, allowing them to bypass obstacles rather than be blocked by them.

While cellular networks and Wi-Fi systems are more advanced than ever, they are also quickly reaching their bandwidth limits. Scientists know that in the near future they will need to switch to much higher communications frequencies than current systems use, but before that can happen, a number of obstacles literally stand in their way.

Researchers at Brown University and Rice University say they’re one step closer to getting around these solid obstacles like walls, furniture and even people – and they’re doing it by bending light.

Advances in terahertz communications

In a new study published in Communications engineeringThe researchers describe how they are helping to eliminate one of the biggest congestions in wireless communications. Today’s systems rely on microwave radiation to transmit data. However, it has become clear that the future standard for data transmission will use terahertz waves, which have up to 100 times the data transmission capacity of microwaves. A long-standing problem is that, unlike microwaves, terahertz signals can be blocked by most solid objects, making a direct line of sight between transmitter and receiver a logistical requirement.

“Most people probably use a Wi-Fi base station that fills the room with radio signals,” said Daniel Mittleman, a professor at Brown’s School of Engineering and senior author of the study. “No matter where they move, they keep the connection. At the higher frequencies we are talking about here, this is no longer possible. Instead, it will be a directional beam. When you move, that beam has to follow you to maintain the connection, and if you move outside the beam or something blocks that connection, you don’t get a signal.”

The researchers got around this by creating a terahertz signal that follows a curved trajectory around an obstacle rather than being blocked by it.

“This is the world’s first curved data link, a critical milestone in realizing the 6G vision of high data rate, high reliability,” said Edward Knightly, co-author of the study and professor of electrical and computer engineering at Rice University.

The novel method presented in the study could help revolutionize wireless communications and highlights the future feasibility of wireless data networks running at terahertz frequencies, the researchers said.

“We want more data per second,” Mittleman said. “If you want to do that, you need more bandwidth, and that bandwidth just isn’t there in traditional frequency bands.”

Novel techniques for signal transmission

In the study, Mittleman and his colleagues introduce the concept of self-accelerating beams. The beams are special configurations of electromagnetic waves that naturally bend or curve to one side as they travel through space. The beams were studied at optical frequencies but are now being researched for terahertz communications.

The researchers used this idea as a starting point. They developed transmitters with carefully designed patterns to allow the system to manipulate the strength, intensity and timing of the electromagnetic waves produced. With this ability to manipulate the light, the researchers make the waves work together more effectively to maintain the signal when a solid object blocks part of the beam. Essentially, the light beam adapts to the blockage by shuffling data along the patterns the researchers engineered into the transmitter. If one pattern is blocked, the data is transferred to the next one, and then to the next if that one is blocked. This means that the signal connection is completely preserved. Without this level of control, the system cannot make adjustments when the beam is blocked, so no signal gets through.

This effectively bends the signal around objects as long as the transmitter is not completely blocked. If it is completely blocked, another way is required to get the data to the recipient.

“Bending a beam doesn’t solve all possible blocking problems, but it solves some of them and in a way that’s better than what others have tried,” said Hichem Guerboukha, who led the study as a postdoctoral fellow at Brown and is now assistant professor at the University of Missouri – Kansas City.

The researchers validated their results through extensive simulations and experiments in which they circumvented obstacles to maintain communication links with high reliability and integrity. The work builds on the team’s previous study, which showed that terahertz data links can be reflected off walls in a room without losing too much data.

Practical applications and ongoing research

By using these curved beams, researchers hope to one day make wireless networks more reliable, even in crowded or obstructed environments. This could lead to faster and more stable internet connections in places like offices or cities where obstacles are common. Before we get to that point, however, there is still a lot of fundamental research to be done and numerous challenges to be overcome, as terahertz communications technology is still in its infancy.

“One of the key questions everyone asks us is how far can you make a turn and how far away,” Mittleman said. “We’ve roughly estimated these things but haven’t really quantified them yet, so we’re hoping to figure it out.”

Reference: “Curving THz wireless data links around obstacles” by Hichem Guerboukha, Bin Zhao, Zhaoji Fang, Edward Knightly and Daniel M. Mittleman, March 30, 2024, Communications engineering.
DOI: 10.1038/s44172-024-00206-3

The work was supported by the National Science Foundation and the Air Force Office of Scientific Research.