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Anyone can pick up wireless transmissions without revealing their location, but transmitting is much harder.

What types of wireless communication systems are there that a device can use to transmit information without revealing its location to other parties (e.g. the network operator) assuming that the other parties are using only standard equipment (not specialized equipment specifically designed to track users)?

Systems that routinely employ receivers capable of measuring arrival time (i.e. precisely enough for time of flight), or directionality, such as beamforming WiFi, could allow a network operator or someone with several receivers to deduce the user's location, and so would not qualify.

Systems in which the device reports its location itself (e.g. to help select the best reciever) such that a device could spoof it or fail to report it (and still be able to use the network) would still qualify.

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    I don't think that is any sort of wireless transmission system which you couldn't trilaterate. – user56893 May 3 '15 at 15:40
  • @JamesR I know; this is asking about whether you could do it with equipment normally used to operate the network.. – AJMansfield May 3 '15 at 15:42
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    Use motorcycles instead. – gowenfawr May 3 '15 at 20:03
  • Dumbing down the adversary's capabilities makes the question much less interesting. – Deer Hunter May 3 '15 at 22:25
  • @DeerHunter The point of that is that I'm not interested in what an adversary specifically interested in targeting you could accomplish, but rather what an adversary who is passively watching everyone using the network could accomplish if you decided suddenly to try to hide your location. – AJMansfield May 4 '15 at 11:56
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There is no way to transmit data wirelessly without being susceptible to trilateration (using the standard definition of "radio wireless").

That's why attempts to "transmit data without revealing your location" usually end up shifting to things like laser, infrared, or other visible light methods. These things tend to work well in directional applications, which is why they're either static (like MAN) or military (for whom the benefits of secrecy justify the trouble of maintaining directional links with mobile and semi-mobile equipment).

(Which is, incidentally, the point I was going for with the motorcycles. If you want non-detectable wireless transmissions, you have to use something other than a radio, and that was a spectacular example).

There's really only two ways to mitigate the the ability to ELINT radio transmissions:

  1. Make them directional. Requires special hardware, works better for some types of radio than others, not really worth it (if you're going there, use a laser).
  2. Lower the power so that the opponent has to be physically closer to triangulate. Of course, in turn, whoever you're transmitting to has to be closer than that. And you don't seem to trust the network operator, so that won't work.

Now, you stipulate that

parties are using only standard equipment (not specialized equipment specifically designed to track users)

That's kind of a difficult stipulation. You can walk your wifi laptop into most businesses secure in the knowledge that their system isn't set up to locate you. But getting a system to do it isn't difficult. And heck, just like Pringles cans weaponized armies of hackers, you can put together your own FindMe pretty easily. I think it's fair to say that anything you can transmit with "standard equipment" can be located by an opponent using off-the-shelf or homebrew devices.

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This answer assumes that the adversary does have access to run-of-the-mill scanning direction finders (an example). Also, the adversary is sure to detect your transmission (otherwise, you'd be talking about LPI radio comms).

For a "successful" transmission without being pinpointed to a single (true) location with some guaranteed accuracy, you have to know, at the very least, the number and locations of the adversary's ESM receivers. Please accept the notion that for some configurations of the receivers your efforts to conceal your location will be futile.

Given this knowledge, you have to exploit several facts about radio comms and trilateration:

  1. Perfectly coherent transmissions from multiple transmitters may make direction finding exceedingly difficult (depends on the numbers!)
  2. Geometry matters. Distance matters. Get away from where the direction finders are and exploit the errors in timing that accrue at long ranges.
  3. Don't be predictable with your power output. Knowing the standard power of your transmitter simplifies the adversary's problem.
  4. Anomalous propagation is your friend. "Urban canyons" create conditions for multipath and very weird echoes, which won't be exploitable unless the adversary took the time to survey the cityscape in advance. Weather also matters.

With all this in mind, you have to understand that

  1. Breaking laws is not recommended. Law enforcement's RF monitoring and direction finding resources in developed countries are vast.
  2. If you want to openly transmit something so important that your only requirement is hiding your location, be prepared to get out of Dodge fast.
  3. Relying on strangers' advice at random Internet sites is no substitute for learning the theory and practice on your own.

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