Dr. W. Curtiss Priest and Kenneth Komoski
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Wireless: To Achieve Universal Service
October 30, 1995According to the recent U.S. Department of Commerce report, Falling Through the Net,
the nation's long-time goal of achieving universal telephone access for all Americans has yet to be
achieved. In light of this reality, our nation's new goal of achieving universal access to its swiftly
developing National Information Infrastructure (NII) seems logically and technologically
dependent on telephone access. This is not necessarily so. There is a logical and technological
alternative that must not be overlooked.
The alternative is wireless access. Wireless access for unserved Americans means
affordable access to communications, information and education for those millions being denied
because of an inability to pay for wired access. Thus, at a time when wired-access providers are
being charged with 'electronic redlining' and worse, the wireless solution outlined here is not just
a solution to a technological equity, it has significant potential for reducing social tensions.
Clearly, communication, information and education, and their concomitant social and economic
benefits are the must likely reducers of these tensions.
It is technologically feasible to provide digital wireless universal service to our entire
population for a very small cost. This has been made possible by improvements in technology and
the country's shift to digital communications.
It is, therefore, very important that we, as a nation, recognize the need for digital universal
service and recognize that the current way spectrum is allocated and used is not suited to achieving
digital wireless universal service, for all, at low cost.
The traditional approach to using wireless spectrum is a complex procedure of assigning
spectrum to various uses. This oftentimes involves selling a license to a user for the exclusive use
of a part of the spectrum.
In other cases, spectrum is allocated to a 'class' of users such as amateur radio enthusiasts.
In the case of radio amateur use, a person takes an exam to become licensed. Once licensed the
user may use wireless on any frequencies that the license permits with restrictions on type of
transmission and levels of power.
At a July 7th, 1995 workshop conducted by the EPIE Institute as part of a study of K-12
Networking and School/Home Networking sponsored by the John D. and Catherine T. MacArthur
Foundation workshop on K12 Networking and School/Home Networking, the participants
examined the spectrum map of the 'United States Frequency Allocations: The Radio Spectrum'
(U.S. DOC, NTIA, charted by Omega Engineering, 1991).
It was noted that there have been recent breakthroughs by the Metricom and FreeWave
companies in using a relatively small and crowded portion of unlicensed spectrum -- 902-928
megahertz for digital wireless communications. It was further doted that the implications of these
efforts are that we are on the verge of a radically different era in which wireless communications
can serve many of our country's needs for universal service.
Metricom provides wireless modems, which can be purchased for just under $300 and that
communicate to a transceiver up to 1/2 mile away. Use of the transceiver costs from $20-$30 a
month. The transceiver can talk to other transceivers and pass digital communications to other
wireless modems, to local area networks, or to the Internet. The wireless modems achieve speeds
that approximate the highest speeds available by dial-up phone lines (28.8 mbps).
FreeWave uses a less elegant networking technology, but has achieved transmission rates
and ranges that are distinctly higher than those of Metricom. They can provide a throughput of
128K bps at distances up to 20 miles, and 9600 bps at distances of 60 miles. The 20 mile
capability is equivalent to a full telephone ISDN line without any monthly charges. Unlike
Metricom, they do not have lower cost wireless modems. Their transceivers are $1250 each and
are bought outright.
Most importantly, we are witnessing these speeds in the first few years of the use of a
relatively new technology: the combination of digital compression, error-correction, collision
detection, mapping and retention of previously used frequencies, and frequency hopping. It is this
new technology that is revolutionizing wireless communications for the future.
What are the implications of collision detection and frequency hopping? They are quite
remarkable. They break away from the need to 'assign spectrum.' A wireless modem can just
look for a clear channel and send a packet of data, and a return packet can be received. FCC rules
require that these devices change frequency regularly when used in the 'unlicensed spectrums'
such as 902-928 mhz. The rules are under Part 15 of the Federal Code and, thus, these
transmissions are commonly referred to as 'Part 15 transmissions.'
The EPIE Institute, MacArthur Foundation-funded study sees a much greater availability of
other spectrum for educational purposes. We call this 'invisible spectrum.' As anyone with radio
background and a map of the spectrum allocation will realize, there are vast areas of spectrum that
go under-utilized or not utilized day-after-day in every community across the country. For
example, Dr. Priest, the study's senior technical consultant, was a radio amateur, K1ZSQ, and
employed the amateur band from 50-54 mhz. At any time of the day about 98% of the band is
As part of the current study we have consulted with a typical local amateur radio group.
We told them about how Metricom/ FreeWave technologies might be employed with their support.
After two hours of discussion the 'hams' said: 'Well, if you are essentially invisible, we don't
care.' They couldn't see what they could do to help except to give moral support - the technology
was beyond this particular group of hams and they didn't see the vision of creating a new class of
'amateur' user who would be using this technology. (Hams have for some fifteen years been
doing 'packet radio' but at speeds of only 1200 baud [4800 with compression] and with the
interest of going great distances using 'repeaters'; they are essentially building their own extremely
low-speed Internet - something that is becoming rapidly obsolete, and still leaves 98% of their 6
meter spectrum unoccupied.)
We have done analyses using Shannon's theorem to examine what the telecommunications
rates can be at various levels of 'signal-to-noise. 'What we have found is provocative and has
profound implications for universal service.
Wireless for Universal Service
If we took the 98% of the 6 meter band (50-54 mhz) there is a theoretical bandwidth of 6.7
mbps (that is megabits/second). With some degradation this might be in the range of 3-5 mbps!
How large is this? It is somewhat smaller than an ethernet Local Area Network (LAN)
running at 10 mps, but not by a lot. So if communities had FCC permission to use the 'invisible
spectrum' of just the ham's 6 meter band we could put community covering a ten mile radius could
be universally served via this single wireless LAN.
In consulting the spectrum map further, television requires 6 mhz of bandwidth per
channel. That's 50% more bandwidth, per channel, than the entire 6 meter band. One can see on
the spectrum map the amount of bandwidth dedicated to television channels 14-69. This ranges
from 470 mhz to 806 mhz -- 376 mhz in total. In even the largest metropolitan areas there are at
most 10-15 UHF channels using this spectrum and, thus, at least 40 channels are empty. At 6 mhz
per channel, this is 240 mhz of 'invisible spectrum' that could be used for education and
community purposes. This is 60 times the bandwidth of 6 meters and could run a wireless
community LAN of an astounding 300 mbps! Also, as we have discussed this idea with other
experts in the field, two other enhancements have been suggested. First, there is additional
spectrum between television stations that can be used (guard bands that currently go unused) and,
second, a top communications expert of the DOD suggested that small directional antennas would
greatly improve performance over implementations such as Metricom's.
Further, there is another advantage to using 'invisible spectrum' below 902 mhz. The
EPIE study reports that as the frequency drops, the ability for signals to pass through buildings
increases dramatically. FreeWave has told EPIE that at 902 mhz they can pass through a typical
building to an antenna on the far side and still attain an 8 mile range. At lower frequencies this
range would be greater AND the reliability and transmission rates would be much better if the
transceiver used, say 10 or 50 watts, instead of the 1 watt required by Part 15. The use of pulse
transmitters, designed in the 1940's for radar, would support this level of power and not require a
power source beyond that of the computer's power supply.
So lower frequencies and higher power in essentially vacant areas of spectrum could
provide an enormous amount of community bandwidth!
The final phase of our study further explores 'invisible spectrum.' Are there other
frequencies that could be employed? Are the collision detection and 'use mapping' technologies
(memory within the transceiver that keeps track of other uses of the same spectrum) developed by
Metricom sufficient to permit the FCC to allow the use of 'invisible spectrum'? What level of
universal service including community and education services could, say, 300 mbps provide to
each user? What congestion problems might there be? Are there any frequencies of use that might
cause health problems due to radio transmissions?
Assuming that the answers to these questions are favorable, local communities,
themselves, could move toward implementing the 'last 10 miles' of the National Information
Infrastructure Looking at the prices of Metricom's wireless modem at $300, at a typical ethernet
transceiver card at $45, and a 14.4 kbps modem at $30, we estimate that a card could be made for
any personal computer for less than $100 in quantities of a million. A million is small compared
with 96 million households and the U.S. population somewhat less than 300 million.
Given the likely technical feasibility, how should we proceed? Should the federal
government or NARUC (National Association of Regulatory Utility Commissioners) issue a
Request for Proposal (RFP) that Metricom, FreeWave, Motorola, and others could bid on to
develop the wireless card (and the community transceiver for each locality)? This might cost from
$1-5 million. With the prototype in hand, FCC cooperation, employing either donated machines
with newly enhanced softwares or recently announced low cost diskless workstations, and the
buying power of schools, communities, and individuals, the vision of the wireless card could be in
millions of homes and schools by the year 2000. Schools, libraries, and homes would be tied
together with much greater ease than imagined when President Clinton and V.P. Gore set this
national goal. (Perhaps schools could use Chapter I funds to provide every eligible student with a
wireless card for families' earned used business computers.)
Relationship to the Current Telephone System
Wired communications will always provide much more capacity than wireless. This is
because each wire (or fiber cable) can carry communications without bumping into another user
because the wire is isolated from all other wires. For wireless, there is only one kind of isolation
that works to prevent interference, and that is physical distance and antenna directionality. Further,
at some frequencies (those that permit 'skipping off the ionosphere') people can communicate
around the world. For those frequencies there is no isolation possible using radio/wireless
Nonetheless, as a local community networking solution for connecting schools, libraries,
homes, and social services, wireless has the distinct, inherent advantage of not requiring wires and
the costs associated with maintaining wires. Until recently many thought digital wireless was
mainly useful for 'mobile users' such as wireless PC's. But as Metricom has demonstrated,
wireless is also practical for fixed position, digital communications.
The wireless LAN described above has some distinct limitations. In a community of
20,000 people, such a LAN could provide an acceptable level of universal service but would not
permit every wireless user to send and receive video, nor would it support very many of these
people using 'high-end' internet access tools such as Netscape with many graphical images. It
would, however, provide better service as the population density decreases in rural areas.
It is these areas that telephone companies incur large costs to maintain telephone lines and
remote service. Thus, the wireless solution is better in exactly the situation which is worse for
telephone company profits.
Also, telephone companies are wiring more affluent communities with advanced digital
technologies because these communities can pay for these advanced systems. Telephone
companies are often charged with 'redlining' certain areas of low-income populations. Again,
wireless becomes an attractive solution to providing universal service to such communities. While
the level of service via digital wireless will not compare with ISDN or better telephone services, it
is more than adequate for many universal service informational and learning needs (Peter
Grunwald Associates, American Learning Household Survey, 1995).
Thus, we suggest that telephone companies are natural allies for the advancement of
universal wireless services. The rural application will solve their problems of serving a lone
customer down a 10 mile dirt road and the low-income services will help meet this country's
universal service needs without burdening the rate base of telephone companies.
Dr. W. Curtiss Priest, LINCT
Kenneth Komoski, LINCT