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Comment by bengotow | Hacker News Reader

Would it be possible to build a software-level mesh on top of these devices even though they don't officially support meshing? In other words, could someone build an iPhone app that implements some sort of decentralized DNS and routes messages, even though the hardware can't do that on it's own?

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CFR 2009 § 95.1311

  MURS stations are prohibited from
  operating as a repeater station or as a
  signal booster. This prohibition in-
  cludes store-and-forward packet oper-
  ation.

http://www.gpo.gov/fdsys/pkg/CFR-2009-title47-vol5/pdf/CFR-2...

Pretty clear cut. No packet routing, at all, for any reason, using any method. Doesn't matter if the radio firmware is doing it or if the client is doing it.

(There is a general exemption to all licensing rules, at least in ham radio, in the case of "to provide essential communication needs in connection with the immediate safety of human life and immediate protection of property when normal communication systems are not available." (§97.403 Safety of life and protection of property.) Not terribly applicable in this situation, but a general "the Constitution is not a suicide pact" kinda thing.)

Then don't use packets, use a streams of hashes or something mathematically similar that doesn't fit the characteristics of a packet, but still retains the security, and integrity of the information.

I wonder whether the FCC is going to consider Bluetooth <-> MURS interconnection to be in violation of this rule.

You're right, that seems to be a very real regulatory risk for this product. Basically, this product is a cross band repeater between the ISM band and the MURS band. Just because the encoding is different doesn't not make it a repeater.

Bluetooth is a short range encrypted point to point link. It would be considered part of the station. Repeaters, in radio jargon, generally accept input from many sources, often without access control.

What's the rationale of the FCC to disallow this? Purely economic reasons?

I think congestion is the main reason. If a transmission had unlimited range (hypothetically), the band would fill up pretty quickly, so it would stop being useful. Natural limits of signal transmission and power limits are what makes public, unlicensed bands feasible. They limit the possible uses, but, stochastically, enables many people to use it at the same time.

At any repeater hop, the transmission uses double the airtime in the overlapping of the sender's and repeater's ranges (once while the sender is sending it, once while the repeater is repeating). And of course, if you use repeaters, a single transmission will use the band in a much larger area than a direct transmission.

With a mesh network, a product like this would be very problematic: From "a way to connect with friends while off the grid" it would turn into "unlimited free texts for a one time charge" (in a country with absurd charges for texting on mobile phones). Soon, neither this nor any other application on the band would be possible anymore.

Congestion is definitely the main reason. What we've done at goTenna's networking layer though, is we've made it listen-before-talk. That, added to the fact that we're only doing short-burst transmissions, makes it highly unlikely goTenna will ever "step on other tranmissions' feet."

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