Improving Spectrum Usage
Through Cognitive Radio Technology

Approved by the IEEE-USA Board of Directors
13 Nov. 2003

IEEE-USA strongly encourages the Federal Communication Commission (FCC) to continue the innovative thinking evidenced by its encouragement of the development and implementation of Cognitive Radio (CR) technology, which offers the possibility of making significantly more efficient use of the finite radio spectrum resource.

A Cognitive Radio is a radio frequency transmitter/receiver that is designed to intelligently detect whether a particular segment of the radio spectrum is currently in use, and to jump into (and out of, as necessary) the temporarily-unused spectrum very rapidly, without interfering with the transmissions of other authorized users. CR is a relatively new technology, so we recognize that both technical and policy questions must be answered before full CR implementation can proceed.

Given the increasing demand for radio spectrum -- a finite resource -- and the potential for CR technology to facilitate sharing of otherwise unused spectrum (temporally and geographically), IEEE-USA strongly recommends that the FCC, with the cooperation of other government agencies and private sector entities:

• Determine, through industry/government sharing studies, in which bands CRs can be used with confidence, and validate the results of those sharing studies through initial field trials.

• Confirm the technical reliability and practicality of CR, by resolving technical issues including:

- What suitable "behaviors" and minimal technical restrictions are necessary to ensure CRs will operate without causing harmful interference to licensed users?

- How can a licensed frequency user determine that any interference received is actually the result of cognitive radio operation, rather than from some other source?

- What is the cumulative effect of very large numbers of CR users?

• Create a regulatory environment that permits CR technology implementation, while providing a method of redress and resolution for instances where interference might occur.

This statement was developed by the IEEE-USA Committee on Communications Policy and represents the considered judgment of a group of IEEE-USA members with expertise in the subject field. IEEE-USA is an organizational unit of The Institute of Electrical and Electronics Engineers, Inc., created in 1973 to advance the public good, while promoting the careers and public-policy interests of the more than 235,000 electrical, electronics, computer and software engineers who are U.S. members of the IEEE. The IEEE is the world's largest technical professional society. For more information, go to http://www.ieeeusa.org.

BACKGROUND

In May 2003, the Federal Communications Commission (FCC) sponsored a Cognitive Radio (CR) Technology Workshop to discuss the potential for more efficient use of the ratio spectrum, based on emerging CR technology, and how to best apply CR for better spectrum usage.

Studies have indicated that much of the available spectrum lies fallow much of the time, on geographic, time and frequency bases. CRs can utilize spectrum that is not already in use. They can also potentially use lower power than required to reach from point A to point Z, by sending lower-power (or even different frequency) signals to other CRs at points B, C, D, and so on, between points A and Z.

In the past, radio transmitters and receivers have been hardware-based. Once built, devices were only usable for the purposes for which they were designed. Now, however, "software defined radio" (SDR) has been developed, by which a given radio transmitter or receiver can be dramatically updated and modified -- on the basis of changes only to the software installed within the device.

CRs are "smart" in that they can "learn" about current use of spectrum in their operating area, make intelligent decisions on that basis, and react to immediate changes in the use of spectrum by other authorized or CR users.

Thus, any radio spectrum can, in principle, be opportunistically used by CRs on a non-interfering basis. CR technology offers the opportunity for efficient use -- without interference to authorized/licensed users -- of currently unused or underutilized spectrum.

The question of primary users' rights and obligations are raised, since many licensed users' perceive they have exclusive control of the spectrum that corresponds to their licenses, whether the license was issued by comparative hearings or bought at auction. The Commission needs to address these issues.

For example, if the CR can detect "on frequency" use by incumbent users that it should not interfere with, what is to prevent existing users from just "keying up" when CR activity is detected (or even just periodically as a "defensive measure") causing the CR to move? Would this become illegal, and under what penalty? By definition, CRs should be inherently non-interfering on a completely independent basis. Therefore, incumbents should be prohibited from deliberately blocking CR access to otherwise unused spectrum.

Of course, the full potential and practicality of CR technology has yet to be fully demonstrated. IEEE-USA suggests that CRs first be proven effective in spectrum that could be considered "low hanging fruit" (i.e. spectrum that has a relatively low percentage of actual usage by the authorized users, and for which the actual occurrence of limited amounts of interference would not be catastrophic).

For example, some bands may not be currently in use. Or, some bands have low average usage. And, some TV broadcast channels are not used at all in geographic areas where CR could be tried.

Clearly, initial trials should not be implemented in spectrum that the Department of Defense, law enforcement agencies or fire departments use. In such cases, the spectrum is often used only a small amount of time on average, but sometimes when it is needed, it is vitally important that it be available, without interference. After significant trials and experience, perhaps CRs could even be used in those spectrum ranges; but surely not in its initial technology trials.

Even in the end, CRs should probably not use some spectrum bands, such as spectrum used for the global positioning satellite (GPS), or spectrum used by satellites for observing weather patterns. In such cases, the CR would not likely detect any competing use of the spectrum, but could interfere with its authorized use.

While at first glance unlicensed spectrum may appear to be a good candidate for initial CR testing, it is necessary to consider the number of consumer and industrial devices that may or do use that spectrum. In fact, some of the unlicensed bands (e.g., 2.4 GHz) are already extremely crowded with devices sharing the band. Thus, experiments with CR in the unlicensed spectrum bands would not fully answer the issues of how CR should be used in licensed/authorized spectrum bands. Such issues must be addressed to take full advantage of CR potential to allow increased sharing of otherwise unused spectrum.

Clearly, some technical issues must be answered before any large-scale CR implementation can proceed, even though it limited trials showing CR technology effectiveness have been demonstrated. However, the challenge of creating a regulatory environment that permits CR technology implementation, while providing a method of redress for instances where harmful interference might occur, and providing for their resolution, is just as important.

IEEE-USA strongly encourages the FCC and other government agencies, as well as the private sector, to pursue CR technology development and application as vigorously as possible. The goal is to relieve radio spectrum overcrowding, which actually translates to a lack of access to full radio spectrum utilization.

Although the FCC must surely recognize and address all of the pertinent issues, IEEE-USA suggests that at this time, the FCC's major efforts, should focus on the following major issues:

• Deciding which bands would be available for initial CR trials, through sound and equitable sharing studies conducted cooperatively between industry and government agencies. Confirming the results of such sharing studies through field trials would, open up other CR bands as the technology proves effective, and further sharing studies and field trials would confirm the CR ability to coexist in those other bands.

• Defining the rights of the licensed spectrum band users where CR technology is authorized. Certainly, licensed users should be protected from CR interference (largely a technical issue). But if CR benefits are to be realized, CRs should not be denied the right to operate on a truly non-interfering basis. The FCC should not charge fees for such non-interfering use, or employ active techniques to deliberately block CR access to spectrum that would otherwise be unused temporally or geographically.

• Defining "harmful interference" within the authorized CR bands.

• At least in the beginning, the FCC should not implement a complete set of absolute rules as to how CR technology should be experimented with, but put guidelines or policies in place that CR users and primary users should follow in good faith.

• Establishing a method for incumbent spectrum users to register evidence of interference to their systems and achieve resolution.

In the interest of realizing the potentially significant benefits of CR technology as rapidly as possible, the FCC should act as quickly as possible to put guidelines/policies in place for trial and long-term CR technology implementation.

Rapid implementation is important not only to solve problems of inadequate access to unused or underutilized spectrum, but also to enhance U.S. technological leadership in cognitive radio technology.

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Last Updated: 17 November 2003
Staff Contact: Deborah Rudolph, d.rudolph@ieee.org

Copyright © 2003 The Institute of Electrical and Electronics Engineers, Inc.
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