Tag Archives: terahertz frequency

Advancing the Speed of Wireless

Scientists at University College London recently achieved a speed on a wireless link of 938 Gbps. That’s over 4,000 times faster than the current average speed being delivered by T-Mobile, the current fastest cellular provider in the U.S.

The team is researching techniques for multiplexing multiple radio transmissions into a coherent transmission. The scientists achieved the speeds by utilizing a huge span of spectrum between 5GHz and 150 GHz. They also had to combine multiple techniques to create and join the signals.

  • The signals from 5-75 GHz were generated using traditional, but high-quality radios that used digital-to-analog converters.
  • The signals from the higher frequencies, the W-band from 75-110 GHz and the D-band from 110-150 GHz were generated by mixing optically modulated signals that used frequency-locked lasers and high-speed photodiodes. By frequency-locking the lasers, the scientists were able to create a stable carrier frequency that avoided the signal noise that would have been generated by normal free-running lasers.
  • The team then used orthogonal Frequency-Division Multiplexing (OFDM)and bit loading to goose the signal up to 938 Gbps over the air.

Another team of researchers recently achieved fast wireless speeds on a single channel. The team is a consortium of researchers from the Japanese firms DOCOMO, NIT Corporation, NEC Corporation, and Fujitsu. The team of companies created a wireless device that uses 100 GHz spectrum indoors or 300 GHz spectrum outdoors to create a 100 Gbps link that can transmit for about 100 meters. The companies see this first device as the prototype for developing future wireless radios that can deliver speeds only possible today on fiber.

In the past, several research teams in laboratories have created terabit speeds for a link of several feet. There is a lot of literature speculating that radios in space could reliably achieve terabit speeds between satellites without the interference created by air.

All of the research teams are pushing the cutting edge for wireless technologies with the goal of someday creating much faster wireless technology. The worldwide push to master the use of the terahertz frequencies between 100 GHz and 1 THz has been labeled as 6G, although wireless vendors have already absconded that label to describe radios that use millimeter wave spectrum. The terahertz frequencies lie between traditional radio and infrared light.

The first 6G summit met in 2022 in Levi, Lapland, Finland, sponsored by the University of Oulu, and included major wireless vendors like Nokia, Huawei, Ericsson, Samsung, and NTT, along with researchers from numerous universities as well as groups like Bell Labs. At the summit, researchers talked about creating a set of standards for terahertz frequencies by 2030. They identified the first hurdle as the development of chips that can handle faster speeds. There were also questions about whether governments would try to regulate the higher frequencies.

For now, these fast tests represent scientists pushing the edge of radio technology. These tests are not going to produce any usable technology for many years. The University of College London used a wide swath of spectrum that would never by allowed by any government. But the early success of these various tests show that faster radios will somebody be possible.

Terahertz WiFi

While labs across the world are busy figuring out how to implement the 5G standards there are scientists already working in the higher frequency spectrum looking to achieve even faster speeds. The frequencies that are just now being explored are labeled as the terahertz range and are at 300 GHz and higher spectrum. This spectrum is the upper ranges of radio spectrum and lies just below ultraviolet light.

Research in these frequencies started around 2010, and since then the achieved broadband transmission speeds have progressed steadily. The first big announced breakthrough in the spectrum came in 2016 when scientists at the Tokyo Institute of Technology achieved speeds of 34 Gbps using the WiFi standard and the 500 GHz spectrum range.

In 2017, researchers at Brown University School of Engineering were able to achieve 50 Gbps. Later that year a team of scientists from Hiroshima University, the National Institute of Information and Communications Technology and Panasonic Corporation achieved a speed of 105 Gbps. This team has also subsequently developed a transceiver chip that can send and receive data at 80 Gbps – meaning these faster speeds could be moved out of the lab and into production.

Like with all frequencies, when transmitted through the air, the higher the bandwidth the shorter the distance until a radio transmission scatters. That makes the biggest challenge for using these frequencies the short transmission distances. However, several of the research teams have shown that transmissions perform well when bounced off walls and the hope is to eventually achieve distances as long as 10 meters (30 feet).

The real benefit of superfast bandwidth will likely be for super-short distances. One of the uses of these frequencies could be to beam data into computer processors. One of the biggest impediments to faster computing is the physical act of getting data to where it’s needed on time, and terahertz lasers could be used to speed up chips.

Another promising use of the faster lasers is to create faster transmission paths on fibers. Scientists have already been experimenting and it looks like these frequencies can be channeled through extremely thin fibers to achieve speeds much faster than anything available today. Putting this application into the field is probably a decade or more away – but it’s a breakthrough that’s needed. Network engineers have already been predicting that we will exhaust the capabilities of current fiber technology on the major Internet transmission paths between major POPs. As the volume of bandwidth we use keeps doubling we will be transmitting more data in a decade or two between places like New York and Washington DC than all of the existing fibers can theoretically carry. When fiber routes get that full the problem can’t be easily fixed by adding more fibers – not when the volumes double every few years. We need solutions that involve fitting more data into existing fibers.

There are other applications that could use higher frequencies today. For example, there are bandwidth needs for specific applications like real-time medical imaging and real-time processing for intricate chemical engineering that need faster bandwidth that is possible with 5G. The automated factories that will create genetic-based drug solutions will need much faster bandwidth. There are other more mundane uses of the higher frequencies. For example, these frequencies could be used to replace X-rays and reduce radiation risks in doctor’s offices and airports.

No matter what else the higher frequencies can achieve, I’m holding out for Star Trek holodecks. The faster terahertz frequencies could support creation of the complex real-time images involved in truly immersive entertainment.

These frequencies will become the workhorse for 6G, the next generation of wireless technology. The early stages of developing a 6g standard is underway with expectations of having a standard by perhaps 2030. Of course, the hype for 6G has also already begun. I’ve already seen several tech articles that talk about the potential for having ultrafast cellular service using these frequencies. The authors of these articles don’t seem to grasp that we’d need a cell site every twenty feet – but facts don’t seem to get in the way of good wireless hype.