Subject: [NEXTEL-1] New Tech Feeds Spectrum Debate

From: Marcel <[email-masked]>
Date: Wed, 02 Jul 2003 01:59:03 -0400

New Tech Feeds Spectrum Debate
By Christian Bourge
June 30, 2003

New technology being developed by the Department of Defense may hold the answer to the contentious debate over the best means for managing the limited-frequency spectrum available for broadcasting and wireless device use.
The Defense Advanced Research Projects Agency is developing technology under the auspices of its NeXt Generation Communications Program, known as XG, that would allow multiple users to share wireless spectrum in ways previously thought unrealistic or impossible.
The XG protocol is designed to work not only within a single band of spectrum, such as the ubiquitous 2.4 megahertz or 900 MHz technologies that are dominant in cordless phones, but also across a wide band of frequencies.

The idea driving the concept is to develop a protocol for an intelligent and adaptive radio device that could take advantage of gaps in frequency use across a broad spectrum, while not interfering with already-existing transmissions.
"We have the technology that will achieve a lot of the objectives for enabling people (users and devices) to work cooperatively in the spectrum," Preston Marshall, program manager of the DARPA XG program, said last week at a forum examining the new technology at the centrist New America Foundation.
The policy implications of this technology are immense, representing a full-on assault on claims by spectrum licensees that their frequency bands have no space for other users and must be protected from interference, even from low-power wireless devices that only put out a radio signal detectable over a short distance. DARPA has projected that the technology would increase the efficiency of spectrum use by an order of magnitude or more. If proven effective, the technology could become the driving force behind a new generation of unlicensed wireless technologies.
According to DARPA, the XG technology would allow the shared use of spectrum through cognitive radio devices. These devices would adapt to the gaps in frequencies available in a particular region by taking into account time, frequency, code and other signal characteristics when determining where along the frequency band the device's signal would be sent. The XG protocol is designed to allow the development of radio devices that would co-exist with existing technologies and wireless standards such as the 802.11, the design protocol for Wi-Fi wireless LAN devices.
Although some technologies allow radio devices to pick the best signals available on a set frequency, a machine based on XG protocol would actually pick its own broadcast frequency. A set frequency would be needed between both the receiver and transceiver device to enable their initial communication, but the decision about what frequency would be used to send all remaining transmissions between the two devices would not be pre-programmed.

The technology is beyond the infancy stage but still early in its development. Although some are skeptical whether it will pan out, Marshall said three military contractors are working on developing radio devices based on the XG protocol and are expected to deliver working prototypes within three years.
The development of XG was driven in part by the shortage of available wireless spectrum along with the need to find new ways to use it and fit more users into it. Marshall noted the main question driving the work is how to automate frequency management in a radio network.
The goal has become to create a cognitive radio whose design is independent of the regulatory restrictions typically faced when developing a wireless device. The function of such a machine could theoretically be changed via software upgrade, to reflect changes in the law covering about spectrum allocation.
"What we want to do is make the policy (governing the XG protocol) independent of the technology," he said. "If we do that right, we can build a set of policies for every radio."

The availability of so-called "white space"-the unused portion of a frequency band occupied by other wireless technologies, such as cellular or broadcast signals-is inherent with the XG protocol. The growth in the development and use of wireless devices has driven a harsh debate over the frequency spectra reserved for federal government use and licensed to companies by the Federal Communications Commission for dedicated purposes.
Whether portions of those reserved frequencies can be allocated to emerging technologies has become a large part of that debate.
Many companies that hold spectrum licenses provided by the FCC claim there are not any underutilized portions of their spectrum. They also contend they need the full frequency spectrum allocated to protect their signals from interference.
Much of this dedicated spectrum is considered prime space for next-generation wireless technologies, particularly for broadband computing applications. Some critics of current FCC licensing practices consider this unavailable space as the potential answer to the so-called "last mile" problem of getting unfettered broadband Internet access to the consumer.
They argue the scarcity of spectrum is an artificial state created by government policy. XG and other evolving technologies demonstrate broadcasters and other spectrum licensees do not need as much space as they have allocated.
Mark Cooper, director of research at the Consumer Federation of America, said it is very important DARPA is talking about the reality of spectrum availability and developing technologies such as XG. He predicted it would help drive a massive policy debate on spectrum use.
"This shows that spectrum can be shared," Cooper told United Press International. "What we are now discovering is that the possibility for getting rid of the system of licensing is growing dramatically. That would be a real revolution."

The National Association of Broadcasters, which has long fought to protect the integrity of broadcast-dedicated spectrum, did not return UPI's calls to comment for this article. However, Mark McHenry, president of Shared Spectrum, a wireless technology firm, said there is space-even in licensed frequencies in crowded urban areas-for a technology such as XG to exploit.
"We have done spectrum measurements over the last two years and the spectrum is not full," McHenry said at the forum. "I think it is pretty clear if we have better access mechanisms there would be a lot of spectrum hertz [available]."
The U.S. military hopes XG technology will allow for the use of radio devices around the world without interfering with existing spectrum users in any particular country. Given that each nation has its own set of rules for the use of spectrum, the military must currently deal with different spectrum rules around the world for the 10,000 to 15,000 radio devices used by the U.S. armed forces. XG would theoretically allow the military to go into a country without having to navigate that country's particular spectrum limitations.
The potential uses for the technology go far beyond military applications.

DARPA is developing XG as an open, unlicensed standard and hopes commercial users will adopt it.
XG is seen as having particularly strong applications for wireless broadband use. Although technologies such as Wi-Fi have enabled wireless access to the Internet for many, they have not driven a boon in the adaptation of high-speed broadband, as many had hoped.
Randolph May, director of communications policy studies at the free market-oriented Progress & Freedom Foundation, agreed with Cooper the XG standard points to the need for greater flexibility in the government's licensing of technology. However, he said, the FCC is moving in the right direction by trying to reengineer its policies to provide greater leeway for wireless technologies.
In addition, May noted XG is one of many emerging technologies- wireless and wired-that should help facilitate the development of a competitive broadband marketplace.
"I think Wi-Fi is certainly a precursor of what wireless can do to help resolve the last-mile issue," May told UPI. "It is not everywhere and it is not ubiquitous, but it is part of the solution and it looks like this new next generation DARPA technology is just a further possible technological development that is going to make wireless more competitive."
http://www.wirelessnewsfactor.com/perl/story/21828.html

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