DARPA eyes radio networks with fiber optic speeds

By Bob Brewin

January 7, 2013

The Defense Advanced Research Projects Agency kicked off an $18.3 million project last Thursday to develop radio systems that operate at fiber optic network speeds -- 100 gigabits per second -- to provide high capacity backbone networks for deployed forces. The agency wants to adapt technology used by cellular carriers and the latest version of the Wi-Fi standard.

DARPA envisions housing the broadband system on a high-altitude platform that operates at 60,000 feet with a planned transmission range of 62 miles for air-to-ground links and 124 miles for air-to-air links.

DARPA wants to tap the highest radio frequency or millimeter wave band, which runs from 30 to 300 GHz (just below the infrared light spectrum). The band supports broadband service over short distances but delivers poor performance in clouds or rain as the raindrops are the size of the small radio waves and impede transmissions.

The Pentagon’s research agency also wants to use a technique called spatial multiplexing, which transmits independent and separately encoded data signals from multiple antennas, known as multiple-input and multiple-output, in the latest version of the Wi-Fi standard, 802.11, to boost throughput.

Cellular carriers use millimeter wave band equipment for “backhaul” from tower sites to a central location. Companies such as E-Band Communications Corp. of San Diego manufacture equipment that today provides throughput of 1.25 gigabits per second in the 70-80 GHz band.

In the first phase of its high speed radio project, DARPA said it wants researchers to develop a system that can beam data at a rate of 25 gigabits per second over a single millimeter wave data stream and antenna with a 6-mile range. The second phase calls for the use of MIMO technology with two and then four antennas and streams to boost throughput to 100 gigabits over a 31-mile range.

Researchers need to develop novel 10 to 50 watt radio amplifiers and signal processing techniques to support high data rates. DARPA wants to install the system on military aircraft, and said bidders will need to develop conformal antennas that fit on the aircraft.

Saul Umbrasas, senior vice president of marketing and business development at E-Band Communications, said that DARPA has a steep challenge to develop a 100 gigabit per second system in the millimeter wave band, and called the project more an exercise “in theory rather than reality.”

Umbrasas said that at best, commercial firms will be able to develop millimeter wave radios that operate at data rates between 10 and 20 gigabits per second.

Proposals are due March 30.

By Bob Brewin

January 7, 2013