[daniper]

We want to do that, but FCC regulations don't enable meshing (currently) on the bands we're using (151-154 MHz, aka the MURS band). We considered releasing a 900 MHz device that the FCC allows to mesh but then you only get, if you're lucky, up to 0.5 km range and it has to be line-of-sight. So we went with MURS because you can get greater range and don't have to be line-of-sight; the propagation characteristics are better down at MURS. Also, when we asked 1000 people (including testers) what they preferred -- a long-range MURS device or a short-range meshing device -- about 8 of 10 picked the former. So that's why the goTenna device you see today is our first release!

[glomek]

Do you intend to release the specifications for the protocol you are using? For example, would I be able to hook a computer with gnuradio up to a MURS radio and write software that could communicate with a goTenna?

[TD-Linux]

This. I am super excited about the GoTenna because it is basically Ham Radio for the masses. But I'd also like to talk to GoTenna users with SDR or similar - in the spririt of non-encrypted ham communication.

[daniper]

We have an open SDK coming out soon -- you can sign up for developer updates at our website

[glomek]

That sounds like a way to write programs that use a bluetooth attached gotenna. Is that correct?

What I am asking is, could I talk to a gotenna using another radio setup of my own creation. Are you publishing enough information about gotenna for me to do that?

[malandrew]

What about for users of GoTenna in other countries that don't have the MURS band mesh restriction? Will they be allowed to enable mesh delivery through a third party on their device?

[Nrsolis]

I ordered mine when the page went live. I hope to get them soon and start enjoying them. I'm actually headed out to Colorado to climb the Collegiate Peaks so I'm hoping they get here before mid-August.

Don't worry. I've got a ham license and I'm bringing my 2m/70cm HT with me and a SatCom set too. Would be nice to give it a go in real-world conditions.

[bengotow]

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?

[sbierwagen]

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.)

[meatmanek]

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

[konstruktor]

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.

[TD-Linux]

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.

[andruby]

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

[konstruktor]

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.

[daniper]

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."

[FindersKeep]

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.

[jrockway]

How often are you getting non-line-of-sight propagation with MURS?

[daniper]

Most of the time. We live in NYC and have gotten anywhere from 0.5 mile to 3.5 miles range here, depending what part of the city you're in. There's nearly no such thing as LOS in a city unless, say, you're in a skyscraper ;)

[jrockway]

Ah, I'm just surprised that buildings ended up mattering when you were deciding between 150MHz or 900MHz.

While people like to complain about the frequency getting higher and propagation dropping off (especially related to 2.4GHz and 5GHz wifi), I haven't found a good paper that guarantees that's the case. Anecdotally, I can receive a 5GHz signal in my office in Manhattan from a radar in Floyd Bennett Field, 12 miles away, with buildings in the way. Similarly, inside my apartment, I have much better luck with 440MHz radio communication than 144MHz communication. (Ground floor, so not that great either way.)

Being limited to 4W EIRP in the 900MHz ISM band probably played more of a role?

Anyway, you might want to find these guys: https://news.ycombinator.com/item?id=7981431

The combination of your product with their technology could be quite interesting.

Also, follow up question: does your protocol attempt to recover signals from below the noise floor?

[daniper]

No on the noise floor question ;)