Dr. W. Curtiss Priest and Kenneth Komoski

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Wireless: To Achieve Universal Service

October 30, 1995


According 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 empty.

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 communications.

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