> Whether a new radio system "interferes" with existing ones is entirely dependent on the equipment involved.
With this definition then there is no other type of rivalry. This is true for any resource with tragedy of the commons, where an externality is encountered. This goes for land, agriculture, pollution, oil, etc. The limit here is always the efficient production from some resource using technology. This is part of the ceteris paribus of rivalry.
For what you're discussing, for non-interfering waves with the same spectrum, you would need a QAM or some other modulation scheme, with more granular phase detection, which requires exponential more energy, thus capital, per degree resolution of phase detection at the same distance. Thus, the rivalry always exists because enterprises prefer the method leading to the cheapest production with the same product.
> maybe we should be promoting technological development by letting people freely interfere, which can be done by imposing no rules whatever, not even a property regime. Absent power limits, that's pretty much what we do with WiFi.
As I'll continue discussing in your other comment this is exactly what Coase advocated for.
> establishing a private property regime is still rather interventionist
It is in the sense you're discussing with the FCC but not in the Coase's sense where private property is in the strict abstract sense by enforcement of contracts between consenting individuals. Coase's point is that it shouldn't be specially regulated differently than the enforcement of any other private contract. Unless for specific cases which can only be known through experience
But it's rivalrous in a distinctive way--it's a function of contemporaneous and evolving limitations of the existing state of technology and usage patterns. To quote a famous IEEE Spectrum article, "Moreover, interference is not some inherent property of spectrum. It's a property of devices. A better receiver will pick up a transmission where an earlier one heard only static. Whether a new radio system "interferes" with existing ones is entirely dependent on the equipment involved. Consequently, the extent to which there appears to be a spectrum shortage largely depends not on how many frequencies are available but on the technologies that can be deployed. Many regulations intended to promote harmony of the airwaves have instead, by putting artificial limits on technology, created massive inefficiency in spectrum utilization." https://spectrum.ieee.org/telecom/wireless/the-end-of-spectr... What that's referring to are techniques like MIMO, beamforming, beam steering, etc.
As David Reed is quoted and paraphrased as saying in that Salon article: '[We have stupid radios not because we haven't figured out how to make them smart but because there's been little reason to make them smart. They're designed to expect signal to be whatever comes in on a particular frequency, and noise to be everything on other frequencies.] 'The problem is more complex than just making smart radios, because some of the techniques for un-confusing the receiver are best implemented at the transmitter, or in a network of cooperating transmitters and receivers. It's not simply the radios. It's the systems architecture, stupid!' https://www.salon.com/2003/03/12/spectrum/
We're only beginning to scratch the service of the channel discernment improvements that can had with MIMO, beamforming, beam steering, and other techniques, but we're limited by the larger ecosystem of devices and regulations, which is largely an artifact of a system which assumes a fixed interference burden across vast geographical areas. The channel capacity of a band of spectrum is, in the absence of coherent interference, point-to-point as a theoretical matter because non-coherent electromagnetic radiation does not interfere. To reiterate, interference as typically experienced is a function of the inability to differentiate a signal which is present or which could be present if the transmitting and receiving systems were more sophisticated, and (according to the theoretical work) this is ultimately a computational problem.[1] Thus "spectrum scarcity", at least in the context of P2P wireless networks, is a function of technology, not an intrinsic, fixed property.
Taking that context into account--that interference and thus the degree of rivalrousness for any band of spectrum is a complex, dynamic function that dissipates as technology progresses--we can end up drawing different conclusions than from the technological presumptions behind Coase's argument. For example, as someone else mentioned, maybe we should be promoting technological development by letting people freely interfere, which can be done by imposing no rules whatever, not even a property regime. Absent power limits, that's pretty much what we do with WiFi. Similarly, a lot of theoretical radio techniques are first explored and applied by the military precisely because of the adversarial context, and they're consistently fruitful because the physical limits of what's possible are still quite distant.
> I’m not arguing for or against the ideas of Coase, only correcting that public presentation of his ideas as an interventionist.
I never had the sense that Coase was characterized as interventionist, at least not in the context of FCC reforms. If refuting that is your goal, fair enough. IME, however, in popular discourse anything "free market" is generally considered non-interventionist, and as compared to FCC regulations contemporaneous with his paper that's a fair characterization. But from my perspective (and AFAIU of many others, especially in the SDR community), establishing a private property regime is still rather interventionist, no less than it is with copyrights and patents, relative to the baseline of nothing. Nobody claims taxi medallion systems are non-interventionist, even when medallions are a freely transferable property right (e.g. NYC, sub-class of medallions in SF, etc). Uber would certainly disagree.
[1] This is why 5G achieves aggregate bandwidth multiples in the same bands even though 4G channel efficiency is near the Shannon limit. See https://cmte.ieee.org/futuredirections/2017/05/17/taking-a-f...