Spread spectrum is good - but it does not obsolete NBC v. U.S.!

• Author: Jackson, Charles

1. INTRODUCTION II. PURPOSE AND APOLOGY III. ANALYSIS A. Assertion One: Spread Spectrum Eliminates Interference B. Assertion Two: Signals Below the Noise Floor Are Harmless IV. CONCLUSION I. INTRODUCTION

   This short Article addresses a popular misconception--that new technologies such as spread spectrum have eliminated the problem of radio interference. That is false. Spread spectrum is a great technology, but it does not eliminate the problem of interference. Similarly, although some have asserted otherwise, signals below the noise floor can create interference.

   We first show that a number of authors have embraced these misconceptions in works addressing public policy--unfortunately, we are not attacking a strawman. Simplifying these authors' views somewhat, they argue technology has eliminated the problem of interference; therefore, the legal rationale for radio regulation under the Communications Act of 1934, affirmed in the 1943 NBC case, (1) must be reconsidered. On such reconsideration, the First Amendment trumps an obsolete theory of interference; therefore, the fundamental structure of the Communications Act of 1934 is invalid.

   We then provide a nonrigorous (no equations!) explanation of the nature of interference created by spread spectrum signals or by signals below the noise floor. We also offer a few pointers to the technical literature for those who wish to understand these issues in more depth.

2. PURPOSE AND APOLOGY

   Scientific discoveries and technologies sometimes gain a cachet out of proportion to their value. Their names become buzzwords--and they are called on to explain problems far beyond their reach. Google the phrase chaos theory together with the word politics or Google the terms quantum and finance, and you will find a host of articles and Web pages that stretch the fabric of science far beyond its elastic limit. (2) Some authors merely use the science as simile, but others claim that the relevant science supports their analysis of politics, finance, or movie criticism.

   A recent example of this phenomenon has occurred in telecommunications policy discussions in which analysts claim that new technology has solved the problems of radio interference. (3) Such claims have appeared in both the popular press and in academic journals. (4) The purpose of this Article is to examine two such claims and to match those claims with what we understand to be the capabilities of the technology. It is not our purpose here to engage in a discussion of spectrum policy--we (the Authors, collectively and individually) may agree with some of the policies advanced by these authors and disagree with others--rather, our purpose is to examine assertions regarding technology and to put those assertions into perspective. (5)

   These technological claims are then used as the basis for arguing that the policy goals and legal basis of the Communications Act of 1934 are no longer valid. (6) For example, Benkler and Lessig state:

   If the engineers are right--if the efficiency of an architecture of spread-spectrum wireless technology were even roughly equivalent to the architecture of allocated spectrum--then much of the present broadcasting architecture would be rendered unconstitutional. If shared spectrum is possible, in other words, then the First Amendment would mean that allocated spectrum--whether licensed or auctioned--must go. (7) The Communications Act of 1934 (8) incorporates large parts of the Radio Act of 1927 (9) and, albeit amended many times, still governs use of the radio spectrum in the United States. The Supreme Court upheld the constitutionality of the Communications Act in NBC. (10) Justice Frankfurter, writing for the majority, upheld the challenged regulations and noted that interference justified regulation,"[u]nlike other modes of expression, radio inherently is not available to all. That is its unique characteristic, and that is why, unlike other modes of expression, it is subject to governmental regulation. Because it cannot be used by all, some who wish to use it must be denied." (11) In dissent, Justice Murphy agreed with Justice Frankfurter on interference as the justification for regulation, "[o]wing to its physical characteristics radio, unlike the other methods of conveying information, must be regulated and rationed by the government. Otherwise there would be chaos, and radio's usefulness would be largely destroyed." (12)

   Both the majority and the dissent in NBC accepted interference as the justification for regulation--that was not in debate. But, if spread spectrum eliminates interference, then that predicate is wrong.

   We note that we hold in high regard many of the authors whose works are considered below and, if it were possible, would omit their names from our analysis. Unfortunately, it is hard to cite an article properly without using the author's name.

   We use the following approach. We state a proposition and follow that proposition with quotations from multiple sources showing how individual authors have expressed and accepted that proposition. We then analyze that proposition from the point of view of communications engineering. Our analysis is intended to be accessible--not mathematical. There are no equations, and mathematical jargon has been relegated to the footnotes.

3. ANALYSIS

   1. Assertion One: Spread Spectrum Eliminates Interference

      This assertion appears in various forms in many publications. Below are several instances of this assertion.

      * CDMA [a spread spectrum technology] modulation schemes allow you to use spectrum without interfering with others. (13)

      * A variety of techniques, some dating back to the 1940s, allow two or more transmitters to coexist on the same frequency. The best-known of these is spread-spectrum.... The practical consequence is that no government regulator or property owner need decide which signal is entitled to use the frequency; both of them can use it simultaneously. (14)

      * [N]ew technological developments, such as spread spectrum and ultra-wideband radio, make it possible for many users to use the same broad swath of spectrum simultaneously without interference. (15)

      * The spread spectrum transmissions of multiple users occupy the same frequency band, but are treated by each other as manageable noise, not as interference that causes degradation of reception. (16)

      * But the most important implication of spread spectrum technology for regulatory purposes is that it allows many users to use the same band of frequencies simultaneously. Because every signal is noise-like, the signal of each user is, to all the others, just part of the background noise. The receiver ignores all signals but the one chosen for reception, and "receives"--translates into humanly intelligible form--only those noise-like transmissions that carry the intended signal. (17)

      * Using a variety of strategies, mostly known as spread spectrum, researchers in wireless technology have begun to demonstrate the viability of systems that allow many users to share the same slice of spectrum without interfering with one another. (18)

      * The problem of interference, as real and serious as it was, like the problem of recouping the non-zero marginal cost of the book, went away. (19)

      * With spread spectrum, a transmission is disassembled and sent out over a variety of frequencies, without causing interference to whatever else might be operating within those frequencies, and is reassembled on the other end.... (20)

      * With spread spectrum technologies, spectrum would not need to be allocated, in the sense of giving one person an exclusive right to the detriment of all others. With spread spectrum, broad swaths of the radio spectrum could be available for any to use, so long as they were using an approved broadcasting device. Spectrum would become a commons, and its use would be limited to those who had the proper, or licensed, equipment. (21)

      These quotations came from Forbes, Columbia Journalism Review, The New Republic, three law review articles, and speeches by the authors. Those authors include professors at Stanford, New York University, Columbia, and the University of Pennsylvania. Another author is a practicing attorney who was a member of the Harvard Law Review and clerked for two federal circuit court judges.

      Unfortunately, the fundamental assertion is incorrect. Actually, spread spectrum does not eliminate interference; rather, it changes the nature of interference.

      Aquinas regarded arguments based on authority as the weakest form...