Although there’s no rigid cadence to engineering innovations — new things are discovered intentionally and accidentally all the time — cellular wireless technology has moved towards a generation-per-decade model, such that 4G devices dominated the 2010s, 5G is ready for the 2020s, and 6G is expected to define the 2030s. The key change underlying these generational shifts is expansion of usable wireless spectrum: Miniaturized radios inside wireless devices can now broadcast on a larger number of frequencies than before, use multiple frequencies simultaneously, and fill wider channels with increasingly massive amounts of data.
I’ve previously explained the 4G-5G network difference as akin to widening an existing highway and adding new high-speed, extra-wide lanes. For wireless engineers, the challenge has been finding the space to build these highways. Throughout the 4G and 5G eras, governments have (slowly and with plenty of drama) reallocated military or otherwise reserved radio frequencies for consumer and industrial use. As 6G looms, engineers and governments are already planning to make use of “terahertz” spectrum, a block of radio frequencies so high that all-new testing equipment, chips, antennas, and other innovations are needed for commercialization.
What is terahertz technology, really? Here’s a primer that will help you understand the next decade of announcements.
Terahertz in context
While most people think of wireless technologies as almost magical — check out this crowd’s reaction to Apple’s July 1999 demo of Wi-Fi — the underlying science is radio engineering, which has been around for over a century, but advanced significantly in the past two decades. Just as home and car radios received audio broadcasts from giant outdoor towers, similar radios later shrank to fit inside computers, phones, watches, and earbuds, receiving data from smaller wireless base stations (and other devices).
Radio waves are commonly measured in multiples of “Hertz” (Hz), the international unit of frequency representing the number of cycles in one second. Kilohertz (kHz) is a thousand Hz, Megahertz (MHz) is a million Hz, Gigahertz (GHz) is a billion Hz, and Terahertz is a trillion Hz. To broadly generalize, as the frequencies go up, more bandwidth tends to be available for data, but the radio waves travel shorter distances and are easier to accidentally impede. Car radios pick up low-quality AM audio signals anywhere in a city, your home Wi-Fi works only within your house, and a millimeter wave 5G phone may drop signal just by moving on the wrong side of a pane of glass.
To get a little more technical: AM radio technology used roughly 10 kHz blocks to transmit monaural audio signals between 540kHz to 1.6MHz frequencies. Then FM radio enabled stereo, superior sounding audio by using larger, roughly 200kHz blocks of spectrum between 88.1MHz and 108.1MHz frequencies. Broadcast TV used varying amounts of bandwidth on 54-88MHz, 174-216MHz, and 470-806MHz frequencies to deliver combined video and audio signals, after which Wi-Fi (2.4GHz/5GHz) and cellular began gobbling up blocks of higher-frequency spectrum for data.
In retrospect, it’s almost funny that those TV frequencies were called “VHF” (very high frequency) and “UHF” (ultra high frequency); today, pocket-sized devices can transmit on 39GHz millimeter wave frequencies, nearly a million times higher, while “submillimeter wave” Terahertz frequencies are even higher than millimeter wave, but believed to be safe — about as far as radio signals can go without moving into light rays, x-rays, and cosmic rays, which unlike lower-frequency radio waves are forms of radiation that could potentially alter human biology.
Terahertz applications, today and tomorrow
Bandwidth is the key reason terahertz technology is being eyed for 6G networks. Without even fully exploiting the spectrum’s potential, researchers have already demonstrated that terahertz waves will let chips exceed 5G’s peak of 10Gbps, and there’s been talk of a target 6G speed of 1Tbps. That quantity of bandwidth would be able to support even higher definition video than is available today, as well as human brain-caliber artificial intelligence, mobile holograms of people and objects, plus live streaming of “digital twins” of real buildings. Once terahertz communications links are widely established between devices, Japanese cellular carrier Docomo predicts that AI will become available everywhere.
Today, terahertz technology can be used to make cameras that “see” beyond the limitations of human eyes. Like millimeter waves, submillimeter waves can be used to detect weapons concealed inside clothing; they can also pass through soft tissue to image bones, and peer through one layer of paint to see what’s underneath it. Companies such as TeraSense, Ino, and i2s have already developed terahertz cameras that can be used to see through materials or detect tiny manufacturing defects, though the price tags can be shocking — the i2s TZcam had an MSRP of $80,000, with a note that the “lens is sold separately.”
It’s fair to say that terahertz tech isn’t coming to smartphones any time soon. Assuming international standards organization 3GPP does indeed coalesce on terahertz frequencies as foundational for 6G networks, the technology isn’t expected to be ready for commercialization in pocket devices until around 2030; Samsung thinks early devices could happen “as early as 2028,” with mass commercialization following two or more years later. A similar 10-year timeline proved to be enough to transform millimeter wave from an engineers’ dream into a viable cellular technology, so don’t bet against it happening over the next decade.
Between now and then, you can expect to see plenty of announcements of terahertz engineering innovations. Keysight Technologies helped NYU Wireless set up a 6G lab before most people even knew what 5G was, starting with sub-terahertz frequencies before moving up to the terahertz range. The U.S. FCC opened a huge swath of spectrum — 95GHz to 3THz — last year, offering 10-year licenses to companies interested in experimenting with the “tremendously high frequency” technology. Research is already underway across the world for potential fabrication materials and applications for terahertz technologies.
We’ll have to see whether terahertz spectrum lives up to its promise, but we could see ultra low-power, highly secure data transmissions accomplished by “extremely small” frequency antennas found within everything from phones and computers to wearables and even clothes. Engineers still have plenty of work ahead to make terahertz tech practical for consumers, but if they continue on their current paths, the next two decades of wireless innovation should be even more exciting than the last two have been.
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