New wireless network world record: 40Gbps over 1km, using EHF 240GHz

New wireless network world record: 40Gbps over 1km, using EHF 240GHz

Researchers at the Fraunhofer Institute and Karlsruhe Institute of Technology in Germany have successfully transmitted 40 gigabits per second over a one-kilometer (0.62 miles) wireless link — a new world record. The technology, dubbed Millilink, is the same speed as the fastest commercial fiber optic links, and could represent a major breakthrough for carrier backbones, broadband internet access in rural areas, and ultra-fast last mile access for customers who haven’t had fiber rolled out in their area.

So you have some idea of the scale of this accomplishment, the most advanced WiFi technology, 802.11ad (WiGig) manages around 7Gbps, over a distance of a few meters. 802.11ac can theoretically be used over longer ranges, but even with 8-antennae MIMO it maxes out at around 7Gbps.

To achieve 40Gbps (a transfer speed of around 5GB/sec, or a Blu-ray disc in five seconds), the German researchers use a massive, 80GHz block of wireless spectrum between 200 and 280GHz. By comparison, your WiFi router at home probably uses just 20MHz in the 2.4GHz or 5GHz range. (See: The wireless spectrum crunch, illustrated.) As you can imagine, you can squeeze a lot more data into 80GHz of bandwidth than 20MHz. In fact, with such a vast amount of bandwidth, link speeds well beyond 40Gbps should be obtainable — but for now, it sounds like the researchers are using a fairly rudimentary transmission protocol. With some multiplexing, it shouldn’t be hard to reach 100Gbps or more.

At this point, you might be wondering why WiFi, 3G, and LTE use tiny blocks of low frequencies, when massive amounts of bandwidth are available in the 30-300GHz (EHF, millimeter wave) range. The short answer is: The higher the frequency, the shorter the wave, the more the signal is attenuated (blocked) by obstacles. Longer waves can pass through walls, or bounce around corners — shorter waves can’t. This means that the Fraunhofer system is really only useful for point-to-point links that are less than a few miles long. Fortunately, that’s more than enough for backhaul between cell towers and ultra-fast last mile internet access. If the German researchers can commercialize their system, there would be a bevy of telecom giants who would love to roll out 40Gbps+ wireless links, instead of the very expensive task of laying cables in an urban environment.

There’s also another interesting corollary benefit of using such a high frequency: Higher frequencies have a shorter wavelength — and the shorter the wavelength, the smaller the antenna needs to be. In the case of Millilink, the transceiver chip measures just 4×1.5mm (pictured above). To generate such high frequencies, Fraunhofer uses its own III-V CMOS process to create transistors that are capable of operating at 300GHz.

Finally, it’s worth noting that faster wireless transfer speeds have been achieved in the lab — “infinite capacity” wireless vortex beams have managed 2.5 terabits per second (64 times faster) over one meter — but this is the first time that such speeds have been obtained in a real-world setting.