Despite all the advances in commercial wireless networking, even the most industrial-strength radio frequency links can't come close to the speed and reliability of wire and fiber. While industry groups such as the WiGig Alliance strive toward providing two gigabit-per-second wireless connections at short range, longer-range wireless links such as the directional microwave systems used on some cell towers top out at around 250 megabits per second—a small fraction of what can be pushed over a fiber backbone.

Of course, you can't run a fiber backbone through the air or summon one up at will on the battlefield. That's why the Defense Advanced Research Projects Agency has launched a program to create technology that can act as a backbone for an airborne network with the same sort of bandwidth as fiber optic backbones—100 gigabits per second. If successful, the program could mean not just faster data connections on the battlefield, but better broadband for people in remote areas and cheaper expansion of cellular networks.

The effort, called the 100 Gigabit-per-second RF Backbone (or 100G in DARPA shorthand), seeks to do more than just overcome the physics that limit current radio-based data connections using the Defense Department's Common Data Link (CDL) standard protocol. The initiative is searching for a solution that will be able to be deployed both to the battlefield and aboard aircraft—and work at distances of over 200 kilometers.

The goal set by DARPA isn't just pulled out of the air, so to speak. The amount of data collected by sensors on aircraft, such as synthetic aperture radars, are so vast that only a small amount of it can be pushed back to commanders on the ground—which is why the military has command and control aircraft like the E-3 Sentry Airborne Warning and Control System (AWACS), filled with crewmembers who can interpret the data close to the sensor. But AWACS are expensive. And with more and more drones carrying sophisticated radar systems to track targets on the ground—along with optical and infrared sensors—the DOD needs a way to beam all the data back at higher fidelity, either to an AWACS, another aircraft, or to a command center on the ground a hundred miles away.

The most likely route to creating this sort of Skynet is to use the same sort of technology used to collect much of the data in the first place—synthetic aperture antenna technology. There have been a number of efforts to turn the Active Electronically Scanned Array (AESA) radars of fighter aircraft into dual-purpose systems capable of both acting as a radar and as a data link. Raytheon, L-3 Communications and other companies working on previous DARPA-funded projects have demonstrated the creation of airborne mobile ad-hoc networks by connecting a data modem to an AESA radar. This turns some of its transmission array into a multiplexed transmitter and establishing network connections of over 4.5 gigabits per second.

DARPA sees the next leap in data throughput coming from improvements in extreme high frequency (EHF) radio technology. Using wavelengths measured in millimeters, EHF frequencies—such as the 60 gigahertz frequency used at the top end of the WiGig standard—are typically only effective for communications at short range and within line of sight. But DARPA believes that by using techniques in the modulation of signals, including quadrature amplitude modulation (QAM), the millimeter wave band can be used over much greater distances, through cloud cover, and to achieve even higher throughput. In a statement on the program, DARPA program manager Dick Ridgeway said the project "plans to demonstrate how high-order modulation and spatial multiplexing can be synergistically combined to achieve 100 Gigabits per second."

While DARPA is looking at this from a purely military perspective, 100-gigabit wireless connections could have much larger ramifications for wireless carriers. They may allow for the creation of temporary network backbones in response to disasters. They could also create an opportunity for an artificial intelligence to create a centrally controlled network of cybernetic killing machines (but that's not within the scope of this research project).

Listing image by US Army