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Spread Spectrum and the Amateur Radio Service (1995)

dcc99.dewayne.gif Dewayne Hendricks WA8DZP
Warp Speed Imagineering
Reprinted from TAPR Packet Status Register, # 60, Fall 1995.


This paper reviews the current status from a regulatory perspective of the use of spread spectrum (SS) in both the amateur and commercial services.


Back in 1989, Al Broscius N3FCT [1] discussed the use of commercially available Part 15 SS devices that were becoming available in the market, for use in the amateur radio service (ARS) for packet radio operations. He identified several commercial systems that were then available and made the following recommendation:

    "To responsibly address this technology, we feel amateur operators should
    experiment with the commercial systems now available in establishing long
    distance communication paths using high-gain antenna systems coupled with
    the maximum legal power of one watt, determining interference levels seen
    by weak signal receivers attributable to spread spectrum transmissions, and
    carefully introducing this technology to computer bulletin board operators
    who could financially support development of an unlicensed computer

To the author's knowledge, to date very little effort has been made by the amateur radio community to pursue this recommendation. For instance, although there have been reports by various hams of their experiences with such devices on various USENET newsgroups over the last several years, there has been no written report of such experiences in ARS publications such as QEX, PSR or DCC proceedings. So while there are now millions of SS devices out in the world today in the hands of the average consumer, SS remains an unrealized technology in the world of amateur radio.

Commercial SS Activities

Since the Broscius article in 1989, there has been a lot of activity in the commercial sector regarding SS. As a result of the request and feedback of many manufacturer's of Part 15 devices, the FCC changed the rules in 1990 in order to make it possible to product devices under Part 15 which could operate at higher data rates and to close up some of the holes in the previous version of the regulation that had been issued in 1985.

In January, 1991, Apple Computer filed the now famous Data-PCS petition with the FCC which asked for the allocation of 40 MHz in the 1850-1990 MHz band for a new radio service to be used for high-speed, local area network services. Some important points of the petition include:

    • be accessible to users of personal computers without imposition of licensing obligations, network connection fees, or air-time charges;
    • be open to any computer manufacturer's products and any network access and usage scheme that complies with the regulatory requirements.
    • be regulated in a manner that assures non-discriminatory access to assigned frequencies by compatible devices for like purposed; and
    • Have flexibility built into the initial regulatory scheme to encourage innovation in and the evolution of Data-PCS technologies and services.

In 1993, the FCC allocated 20 MHz for this new service, in the 1910-1930 MHz band. In addition, ten additional MHz were allocated this year by the FCC for this service in the 2390-2400 MHz band. Lest you forget, this ten MHz of spectrum is part of the current ARS allocation which runs from 2390-2450 MHz. The ARS was made primary in this band by the FCC and the Data-PCS service now shares this band with the ARS on a secondary non-interference basis.

Finally, Apple Computer this May '95 petitioned the FCC for yet another new service called the NII Band (National Information Infrastructure). In this case, they are asking the FCC to:

    * allocate for use as part of the NII Band the 5150-5300 MHz band, a shared private-government band that currently is not heavily used within the United States and has been allocated throughout most of Europe for unlicensed wireless local area networks;

    * allocate for use as part of the NII Band the 5725-5875 MHz band, a shared private-government band that currently is used by unlicensed Part 15 technologies, industrial, scientific and medical ("ISM") devices, and Amateur radio operators;

This comes to a total of 300 MHz!! Again, lest you forget to notice, about 150 MHz of this is coming out of the ARS allocation at 5.7 GHz. Apple describes the essential characteristics of this new service as follows:

    "The NII Band will be fundamentally different from any other wired, licensed-wireless, or unlicensed service. Unlike licensed-wireless services, no single entity will have an exclusive license to provide service using the spectrum. Unlike both licensed-wireless and wired services, availability will not be determined by a service providers deployment plan or the economics of a fee-for-service offering.

    Unlike traditional Part 15 operation, NII Band devices will not have to contend with unpredictable and uncontrollable interference, a host of different devices employing a variety of modulation schemes and power levels, and the continuing threat of giving way to incompatible services.

    Unlike Data-PCS offerings, the NII Band will support very high-bandwidth transmissions and communications over longer distances. Unlike the proposed unlicensed bands above 40 GHz, the NII Band will support certain in-building and longer-distance communications that are not feasible using very high frequencies and will be amenable to more rapid product deployment.

    The NII Band would promote the full deployment of a National Information Infrastructure ("NII"), extending the effective reach of the NII by making possible high-bandwidth access and interaction throughout a limited geographic area -- where mobility is key -- both on a peer-to-peer, ad hoc basis and through wireless local area networks. Moreover, it would provide for unlicensed, wireless, wide area "community networks" connecting communities, schools, and other groups under served by existing and proposed telecommunications offerings.

    The NII Band would advance a host of public policy objectives, including assuring that all segments of society have access to the "information superhighway;" extending advanced telecommunications offerings to schools, libraries, hospitals, and government agencies; and promoting the participation of small businesses, businesses owned by women or minorities, and pioneering firms in tomorrow's telecommunications marketplace."

As you can see this is a very ambitious proposal. If it makes it thru the rulemaking process at the FCC, then in the near future the average consumer will have in their hands communications facilities which will make the current technologies and practices of the ARS look like something from the age of 'spark gap' transmitters. To date, it is estimated that there are about 60 million Part 15 devices out in the world. Of these, about eight million are SS devices.

One can expect to see lots of exciting wireless products announced and SS technologies will be a major part of many of these new offerings.

Amateur Radio SS Activities

Little has changed in the amateur radio service as far as high-speed SS packet radio is concerned in the period since 1989. Most of the commercial SS equipment available today on the market cannot be operated under the current Part 97 rules. One event of note however, was the publishing by the ARRL of the "Spread Spectrum Sourcebook" [2]. This was an excellent attempt by the League to acquaint the average ham with the technology of spread spectrum. Another excellent reference on packet radio technology and the use of SS appears in [3].

About the time of Apple's Data-PCS petition, Robert Buaas K6KGS submitted a request for an STA (Special Temporary Authorization) to amend Part 97 to allow relaxed usage of SS technology in the ARS. Buaas' request was granted by the FCC in 1992 and he was awarded an STA that had been renewed several times and remains in effect as of today. There is a recent QEX article which covers the STA and SS technology [4]. An earlier QEX article which describes the STA appears in [5].

Since the original STA was granted, Buaas and the other hams who are authorized to experiment under the STA have performed many experiments using SS technology both with existing Part 15 SS devices and homebrew hardware that was developed for the purpose of the experiments. This work formed the basis for the ARRL Board of Director's to pass a motion in January, 1994 to have their counsel submit to the FCC a petition for rulemaking to modify the SS rules in Part 97. Nothing was filed with the Commission in 1994, however the League's Board reaffirmed its decision this year at their January meeting. At this time, the author can report that both the League and TAPR will be submitting petitions for rulemaking to the FCC to change the SS rules. This filing will be the joint effort of both organizations during the past year to come up with a set of rule changes which will allow the amateur community to make the most effective use of SS technology in the ARS.

Future issues of PSR will provide more information on the petitions and how they are moving thru the formal rulemaking process. In addition, in the coming year TAPR will be launching an initiative to better acquaint the average ham with this technology and make it possible for them to experiment with it thru the availability of new hardware.

To sum up, the ARS has a lot of catching up to do with the commercial sector in this area. SS technology is not magic and is by no means the solution to all of the world's problems. However, it can make possible some new avenues for the deployment and availability of high-speed packet radio systems to the amateur radio community in the future.


[1] Broscius, A. "License-Free Spread Spectrum Packet Radio," 8th ARRL Computer Networking Conference Proceedings, p.16 [1989]
[2] American radio Relay League "Spread Spectrum Sourcebook," ARRL, [1991]
[3] Lynch, C.A. and Brownrigg, E.B. "Packet Radio Networks - Architectures, Protocols, technologies and Applications," Pergamon Press [1987]
[4] Price, H. "Digital Communications", QEX, p. 22 June, [1995]
[5] Rinaldo, P. "CDMA Spread Spectrum STA", QEX, p. 2 June, [1992]

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