DoD Weighing Dynamic Frequency Selection for Better Use of Spectrum

Mark Norton, principle technology adviser to the Defense Secy. for networks and information, told us that DoD is still evaluating the test, done at Ft. A.P. Hill, Va., and hasn’t decided whether DFS will be a big part of how the military uses spectrum. “We have seen a 6 node demonstration,” Norton said. “We have to experiment and understand how it can be scaled, the implications of adopting it to our current networks and radios, as well as the other conditions such as costs, network burden. Once we get a little better handle on those parameters we need to decide exactly where it fits in the spectrum.” He said it may not necessarily work for all spectrum, “but it may benefit certain spectrum bands.”

DoD dedicated the last day of the summit to DFS. A presentation on the Shared Spectrum test was followed by a panel discussion on the technology’s future. DFS “dynamically” tells a transmitter to move to another channel when interference arises, such as from a radar signal. Devices using DFS also monitor availability of unobstructed spectrum before transmitting.

In the test, witnessed by dozens of industry observers, 6 mobile 802.16-based radios using DFS were able to operate in the same spectrum as a suite of fixed, instrumented military and commercial legacy radios without causing interference (CD Sept 19 p3).

More tests are needed, Norton said. “We'd like to go to a 25-node network next and get into a little more of an operational environment,” he said: “That’s still probably a year away.” Many questions remain on whether DFS has a place on the battlefield. “We need to ask where does it fit the best, where can we afford it, does it replace current capabilities or does it provide new military utility,” Norton said. “Is it survivable? Is it susceptible to jamming? Does it fit with existing security policy? All of these are questions that need to be looked at in more detail.”

Kalle Konston of Alion, who has been involved in IEEE efforts to develop standards for DFS, said the recent test will be seen as “a defining moment” for DFS. “I think there are some analogies between what went on there and what the Wright Brothers did,” he said: “It wasn’t that they were the first ones to fly. They were the first ones to fly under control and not crash and have a disaster in the process.”

Paul Kolodzy, chmn. of the FCC’s former Spectrum Policy Task Force, said he has believed for many years DFS would work, as shown by the recent test. “DARPA is starting to show the first steps, that they have real systems that were actually interacting with each other,” Kolodzy told us: “There were holes out there and they dynamically changed their frequencies to make sure that they could fit inside of them in a very dynamic environment… This actually has shown that it has worked in very fast dynamics… The only question now is how does this scale. What happens when you get to larger and larger systems.”

DFS is of interest to the military as well as to business, Kolodzy said. “In the military community they need this because they're making more and more intensive use of their spectrum. They need that to protect their forces, and to be able to do that they need to find some way of actually using the spectrum even more intensively than they're using it today,” he said: “The commercial folks are looking at it for the TV white spaces, taking advantage of spectrum that is underutilized to be able to put out new services.”

DFS will change how people think about spectrum, predicted Donya He, engineering mgr. at BAE Systems. “The old thinking pattern is not going to work,” she said. “Before you had spectrum managers sitting at a desk saying here’s a set of frequencies I can’t use. I can’t assign to this group. That paradigm has shifted to everything is going to be dynamic.”