Researchers have sent information across two kilometers (1.2 miles) using sub-terahertz frequencies, the expected range for the still-developing 6G, the future generation of mobile system standards. This is the longest transmission ever achieved at these wavelengths, transmitting information at over two gigabits per second.
The deployment of 5G technology has shown that it is possible to transmit data over cellular networks at high speed with low lagging, but fiber-optic networks continue to be much faster. Serious competition could come from the deployment of 6G, the sixth generation in telecommunication – hence the name.
The road to this next generation is far from smooth – while the advantages are clearly exciting, the technical challenges are quite significant. The limit for the current frequency for 5G is 71 gigahertz, so 6G is going to go beyond that all the way to maybe 3 terahertz (3,000 gigahertz).
"You need to find a technology that can give you optical-like connectivity without the optical problems, and we think that terahertz technology is that," senior researcher Josep Jornet, from Northeastern University, said in a statement.
The approach has to borrow from NASA technology since the space agency has been using terahertz wireless systems to receive signals. Commercial radio components don’t get to such frequencies – not that they would be useful as they are, the team had to redesign how to send signals. The standard approach is to have a signal generator and a mixer, which adds the information to the signal. At terahertz frequencies, a standard mixer would get so much power that it would break.
So the team simply got rid of it and fed the information directly to the source. This was easier said than done, as the initial attempts led to a signal that became unintelligible. The team had to distort the information before sending it to the source so that the signal came out alright. However, they were able to get the information out without errors.
"In theory, you do the equations, and it sounds like it would work, but to make this theory you make many assumptions about how the device works internally," Jornet added. "Many times, when you go through this, you expect it not to work, so we were quite surprised that it actually worked."
It worked extremely well, hitting frequencies and bandwidths over 100 times better than 5G networks. A 10-fold improvement would have been sufficient for a 6G network.
While this is exciting, there are several issues to be sorted out. First and foremost, these terahertz frequencies are more susceptible to obstacles than 5G. For this reason, researchers think that before this tech gets to mobile phones, it might be used in communication from satellites as well as connecting rural communities with better infrastructure that doesn’t depend on cables.
The breakthrough is reported in Nature Electronics.