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Signal jamming seems like an annoyingly simple way to sabotage a lot of interesting ideas. It has historically been used to block reception of propaganda broadcasts, and also to ruin military communication. My interests are more in the latter, but wider and looking far into the future.

The fundamental problem of interest is that of making good decisions after losing contact with superiors. This can be encountered in a variety of situations without dramatic consequences, but is amplified by two factors that will only become more relevant in the future: One of the factors is how much is at stake. An example of high-stake autonomous decision making is that of having to decide whether to launch nuclear weapons, as in this story from the Cold war. The other factor is the importance of unmanned systems. Even a remotely controlled system must have some fall-back mode when communication is lost, and for certain systems, typically expensive and/or dangerous ones, especially those exercising (military) power, neither inaction, deterministic behavior nor self-destruction are acceptable options. An example would be a space-deployed nuclear attack surveillance and defense system.

If communication can always be jammed, the only solution I see is increasing local autonomy. For sufficiently complex missions, this entails solving the problem of aligning the goals of agents possessing artificial general intelligence with the goals of their owner. That is in itself an immensely difficult problem. Since communication latency inevitably grows with distance, and power inevitably shrinks, sufficiently remote operations alone will require solving the same problem. In a question at the World Building StackExchange, I previously proposed that the difficulties of goal alignment could motivate a super-intelligent ruler agent to limit its own autonomous presence, and thus its power, far away from its base. Such considerations are not exclusive to an artificial super-intelligence, though possibly both compatible with one and a (nearly) convergent instrumental goal. The principle outlines/reiterates a solution to Fermi's paradox, in the sense that very advanced civilizations will choose to stay at home and perhaps even hide their existence for safety.

Here, however, we may restrict the interest to cases where signal jamming is the foremost concern, i.e. where (for any reason) all acceptable paths to success crucially depend on working communication. Therefore, this is a physics question. It also has (relatively) down-to-Earth relevance in the context of safety against nuclear war.

The Wikipedia entry on Radio jamming mentions several methods for jamming radio signals, including (among others) noise and pulses. The countermeasures mentioned are increasing transmission power and using other frequencies than those jammed.

Intuitively, as a non-physicist, I presume that a way to counteract noise-based jamming is to portion out the transmissions in short, high-power pulses that stand out from the jamming noise. Furthermore, assuming that pulse-based jamming likewise depends on prioritizing its input for high-power pulses, it should leave vacant signaling time between the pulses. If the signal to be jammed has a predictable pattern, the jammer can target that pattern. If the signal is not made robust through redundancy, the jammer can break the communication line merely by spewing randomly spaced pulses.

But what if the signal of powerful pulses follow an externally unpredictable pattern (defined by something like secret key encryption) and has built-in error correction based on redundancy? Would that still be jammable? And if not: Would it be practically usable? And would it have side effects of jamming other communication or destroying electronic equipment? (In the latter case, the technology could still find uses in crucial applications like nuclear defense.)

Wikipedia apparently does not even have an article named pulse-based communication. I did, however, find an article on Ultra-Wideband communication, which is sometimes referred to as "pulse radio". It does not look particularly promising, being described as having short range and low Signal-to-Noise Ratio. I am interested in hearing some expert views on this.

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    $\begingroup$ Depends a lot on whether you can tight-beam (line of sight) a signal. Much harder to jam a highly directional receiver. $\endgroup$ – Carl Witthoft Apr 9 at 13:39
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Any form of digital radio communication already employs error correction. It's not so much a question of whether or not to use error-correction, but an assessment of the amount of overhead to be allocated to provide support for error correction.

Such overhead reduces the bitrate of the transmission. Given the state of technology of error correction I would expect that blanket jamming of radio communication is not possible, but extensive suppression of radio communication is. The presence of jamming reduces achievable bitrate of radio communication.


A form of sharing frequency space that is in widespread use is 'frequency hopping'. I assume that in frequency hopping there is also a lot of mutual interference, requiring redundency in the protocol, but overall it is (to my understanding) the most efficient way of sharing frequency space.

To evade communication suppression (jamming) I can imagine a system that hops over a very wide frequency range, adapting to whatever works best in a particular environment. To suppress that kind of communication the adversary would have to broadcast jamming over a very wide range of frequencies. I assume that will be very expensive, both in hardware and energy consumption.

A bit of history:
The earliest form of internet connection to homes was using Plain Old Telephone System (POTS). Those copper lines were build to carry a low bandwidth analog signal: human speech. As a result there was a limit to the achievable bitrate. At some point a very clever signal technology was developed. The protocol to build the connection would sample the quality of the connection at various frequencies, at some frequencies there would be more distortion than at others, and it would subsequently favor the frequencies and modes of transfer with the least distortion. With that adaptive protocol it was possible to achieve a bitrate slightly higher than the Shannon limit.


The 'Shannon limit' is so ubiquitous in digital information transfer that the expressions 'bitrate' and 'bandwidth' have come to be used as interexchangeable expressions. With a wider frequency space available you can transfer more information per unit of time.

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  • $\begingroup$ Thanks! So I should not expect perfect jamming to be possible, because any(?) amount of noise can be counteracted by increased redundancy, at the expense of bitrate. Could you explain how a higher bitrate than the theoretical Shannon limit is possible? Are you perhaps referring to the Shannon-Hartley limit, which assumes Gaussian noise? BTW, I notice Wikipedia's explanation of Shannon's Noisy-channel coding theorem assumes a stationary or somehow predictably changing transition model. But how to handle an adversarial adaptive model? And does my suggestion about pulse signals make sense? $\endgroup$ – Elias Hasle Apr 9 at 13:57
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The most important insight to this is that in communications we do not really encode "bits" instead we encode waveforms, in other words messages are encoded into waveforms not into "bits". Now waveform communications aimed at a specific spatial direction have several "dimensions" that can be used to carry the message.

  1. time
  2. frequency
  3. phase
  4. energy (amplitude)

Any combination of these or just by themselves can be used to modulate (change) the underlying information carrier (sinusoid) and transmit information. Which is the best depends on the channel. Modulations by 1,2,3 have the advantage that the various waveforms can be made orthogonal quite easily and thus be separable by the waveform filters of the receiver.

Shannon proved that in normal (Gaussian) noise it does not matter what modulation scheme you use, the same SNR can get you the same optimal performance. But except for satellite comms that can be very close to the idealized additive Gaussian noise channel terrestrial reality (jamming, saturation, nonlinearities, etc.) is different.

The simplest form of orthogonal time modulation (time hopping) is sending fixed shape non-overlapping pulses at pseudo-random, i.e., information dependent instants where the information to be sent is the time slot of the pulse. Orthogonality of the pulses is obvious because they do not overlap in time. This scheme was actually the first widely used form of "spread spectrum" and was (is being) used in every single military airplane to be identified as a friend or foe (IFF).

What @Cleonis was alluding to in his answer was a form of coding in the frequency domain. Signals that are non-overlapping in their spectrum are orthogonal from Parseval's theorem, so information sent in one slot is not affected by the one in the other and can be individually processed. You can dynamically change the carrier frequency of a slot and then the slot index is the information (message), this is called frequency hopping and since the invention of digital synthesizers it is a widely used modulation technique especially in military comms.

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