What is Open Spectrum?

---Robert Horvitz, 29 June 2005
http://openspectrum.info/ (no longer online)


"Open Spectrum" is based on the realization that technology can reduce or even
eliminate the need for governments to micro-manage wireless communication. In
different contexts it can be viewed as

     * an ideal of freedom in the use of radio frequencies;
     * a critique of traditional spectrum management;
     * a possibility arising from trends in radio design.

In fact it is all of these - leading to differences in emphasis and opinion among
Open Spectrum supporters. A webpage cannot resolve these differences, but it
can position our work by clarifying some of the policy options.

For almost a century, governments have imposed detailed limits on the use of
radio - who can transmit or receive what frequencies and waveforms, at what
power levels, in which locations, for what purposes. Licenses summarize these
controls for specific users or "stations." State control of radio usage goes far
beyond what is accepted for other media (speech, publishing, photography,
Internet, etc.). Yet most people accept strict rules for radio in the belief that they
are necessary to prevent chaos and interference.

However, during the past 20 years, smarter radios have been developed that go a
long way toward solving problems which once seemed to require government
intervention. Cordless phones can automatically scan a band to select an
unoccupied channel. Cellular phone networks dynamically assign frequencies
when handsets are activated, and set signal levels to the minimum needed for an
adequate link. Smart receivers can separate signals that are coded differently
even when they occupy the same channel. Smarter radios tend to combine ease
of use with better link quality and support for novel applications. The combination
of these attributes has fueled explosive growth in public demand for wireless
devices. And the spread of these devices dramatically improves economic
efficiency, productivity, personal safety, convenience and social cohesion.

But the wireless boom also drew attention to the fact that regulations designed to
protect "dumb" radio equipment from interference create artificial shortages of
frequencies. Recent surveys have shown that static frequency assignments can
result in band utilisation rates as low as 5-10 percent. A few radio experts began
making this point in the mid-1990s, laying the groundwork for Open Spectrum to
emerge as an alternative model in spectrum management. Eli Noam, Yochai
Benkler, Dave Hughes and Kevin Werbach were among the first to argue for Open
Spectrum as a serious policy option. But it was the US Federal Communication
Commission's 1985 decision to allow new communication technologies in the
bands for unlicensed "Industrial, Scientific and Medical" (ISM) devices that 
jumpstarted this evolution.

Communication in the ISM bands must tolerate interference. This is in contrast to
traditional spectrum management, where the aim is to prevent interference.
Protection against interference is normally achieved by not letting other
transmitters use a licensed channel within a geographic "protection zone." 

But Wifi - a technology that developed in the ISM bands - showed that large numbers of
people can share a band, without specifically assigned channels, if everyone uses
low power and waveforms designed to soften the effects of interference. With no
protection zone, there is no technical justification for licensing Wi-Fi. And indeed,
most countries now exempt Wi-Fi from licensing, as shown by our global survey.

Wi-fi is often cited as Open Spectrum's "proof of concept," validating "unlicensed
commons" as a practical paradigm in frequency management. That is why we
focus on the de-licensing of Wi-fi as a confidence-building measure for regulators
just starting on the path toward freer public access to radio. However, it is also
important to note that Open Spectrum is a much broader concept than Wi-fi. At
the same time, Wi-fi works as well as it does because of widespread voluntary
acceptance of the IEEE 802.11 standards, and because of mandatory processes of
"type approval" (in which equipment is approved by regulators for unrestricted
sale if it conforms to certain parameters, particularly as to radiated power and
frequency use). Thus, unlicensed is not the same as unregulated. Open Spectrum
supporters seem split by this distinction, with some arguing for complete
deregulation, and others (like ourselves) embracing type approval as preferable to
licensing.

Another divisive issue is unlicensed access to licensed bands. Ultra-WideBand
signals, for example, can be used at such low powers - below what is already
allowed for unintended emissions, in fact - that many people think UWB
interference to licensed services is unlikely. On the other hand, some licensees,
who paid millions of dollars for their frequencies, do not want unlicensed UWB to
get access to the same frequencies for free. A different approach is called
"cognitive radio." Cognitive devices recognize the presence of other signals in
their environment, quickly re-tuning to unoccupied channels and vacating each
channel as soon as the primary licensee starts using it. Dynamic, opportunistic
access like this could push band utilisation to very high levels indeed. But would
the risk of interference from cognitive radios really be minimal? This is a question
that needs more testing under a wide range of conditions. Nevertheless, opening
a licensed band to shared use by unlicensed devices is easier than completely
clearing a band of licensed users. So if you think of Open Spectrum as something
that can be introduced gradually, this is an important option.

"Passive" radio services - like radioastronomy and satellite downlinks - pose a
special problem. Their earth stations do not emit signals that could be detected by
cognitive radios, and they must be able to receive extremely faint signals without
interference. It may be that the bands for passive services need to be protected
like wilderness areas and excluded from unlicensed use. We have no problem with
that - but other advocates of Open Spectrum think all radio bands should be
unlicensed commons regulated only by "the minimum set of rules required to make
the commons sustainable."

Regardless of the problems and risks, some people think radio technology is
evolving inevitably toward a future where traditional forms of regulation will be
impossible. Billions of Radio Frequency IDentification (RFID) tags are likely to
spread around the world in the coming decade; they will be as hard to control as
an epidemic. "Software-defined radio" is another challenge. More and more radio
functions that had been performed by hardware are likely to be implemented in
software in the future. If this software is open source, or can be modified or
replaced after purchase, "type approval" processes are undermined.

What then? Optimists envision a post-regulatory future where Darwinian
competition in the marketplace will yield the "fittest" devices - equipment immune
to interference and capable of automatically finding and exploiting any morsel of
under-used spectrum when needed. Just as the largest animals tend to be placid
vegetarians, the users of powerful radio equipment may choose not to cause
interference, for the benefit of all. Widely supported standards and protocols for
automating co-operation and "politeness" seem essential for the success of this
scenario. If some spontaneously self-organizing system can be devised for quickly
imposing penalties on interferers, everyone could feel more confident in such a
future.

Our own goals are more modest. We would like to eliminate governments' role in
granting permission for individuals and organizations to use radios harmlessly,
particularly in developing countries. To state that positively, we want to unleash
the benefits of wireless communication for economic and social development in
the places that have the most to gain. As the need diminishes for treating radio
with special strictness, to counteract the technology's shortcomings, radio
regulation should converge toward the rules that apply to the most common
medium - ordinary human speech. It may take a while to get there, but progress
along the way will be marked by economic growth and improvements in the
quality of life.


Note: Thanks to the efforts of supportive volunteers, this text is also available 
in Chinese, Russian, Spanish, Portuguese, Italian and French.