4
$\begingroup$

In my story the army has outfitted all of their front line soldiers with monitors to track movement and vital signs.

The devices then sends the encrypted information back to base to be decrypted and processed.

The enemy may be able to detect the transmissions and have a clue to where the soldiers are located.

What could I do to prevent this?

$\endgroup$
2
  • 1
    $\begingroup$ I don't have the time to write up an answer at the moment, but look into ultra-wideband with satellite links. HF NVIS (short wave near-vertical incidence skywave) could work too but the antenna sizes will be prohibitive. $\endgroup$
    – user
    Feb 16 '17 at 10:59
  • $\begingroup$ How close do the enemy's estimates of solider positions need to be? Also, how much data are we talking about sending (bytes/sec). How far does it have to be sent? How technologically advanced are the adversaries? SIGINT is a complicated subject, as is any game of cat and mouse. $\endgroup$
    – Cort Ammon
    Feb 16 '17 at 16:48
10
$\begingroup$

There are a few options, but none are perfect (and one only really works in space).

The issue is that if your wireless transmissions can be detected from a few locations then your enemy can (with a bit of maths) work out where you are. So we try to deny them the signals to analyse

Burst transmissions: Only ping your information every so often. This stops the enemy maintaining a constant lock, or even finding one if you change frequencies often enough. Not perfect as they could theoretically still get a lock, but better than blaring out your position constantly.

Fake them out: Set up other radio stations that fill the skies with random noise. A clever enough enemy will still be able to find you though, as they'll be able to identify and either ignore or destroy your ECM devices. Potentially using drones equipped with their own location transmitting packages (that you can then ignore) would help.

Keep very quiet: Requires a hardwired network of repeater nodes. If you keep your radio signals very short ranged then you can use a network of repeaters (like cell towers) to report last known location without too much risk of the enemy detecting your radio chatter. Downside is you'd need an extensive and well camouflaged network, and there's always the chance it can be destroyed or hacked. Potentially very useful for urban defence forces.

Satellites and lasers: Forget radio. If you're throwing out radio waves you're audible. Instead keep track of a series of satellites and have an automated comm package that maintains an laser lock on the satellite. The satellite can calculate your positions and transmit that back to base. It's undetectable by the enemy unless they're in the path of the laser, and even then they won't be able to use the laser point to triangulate your position unless they see more than one. This won't work indoors, under foliage, under cover, on a cloudy day, if it's too hot, if it's too windy or if you get dusty (or if the enemy deploys smoke), so it's only really a useful method if you're on an airless, clean planetoid.... So instead:

Satellites and directed radio antennae: Not perfect, as radio waves are going to spread more than coherent light, but they'll have a much wider operational range than lasers and they'll still be pretty hard for your enemy to pick out due to their non-homogeneous nature.

In reality? A combination of the above. Having any kind of real-time tracking system is a risk, so swapping methods, frequencies, encryption codes as often as possible in order to keep your enemy guessing as to what they should be looking for is a good idea.

Or just don't try.

$\endgroup$
5
  • $\begingroup$ privateinternetaccess.com/blog/2017/02/… may be of interest. Particularly the paragraph towards the end that starts with "Now, compare this who people who get mortar shells flying toward their location the second it is revealed." $\endgroup$
    – user
    Feb 16 '17 at 12:11
  • $\begingroup$ @MichaelKjörling: Yup. Sad truth is that any form of obvious sustained radio messaging is going to get you noticed and dead, it's just a matter of degrees. $\endgroup$
    – Joe Bloggs
    Feb 16 '17 at 12:14
  • $\begingroup$ I haven't had time to read up on what the state of the art is at this very now, but a maser wouldn't be completely out of the question. I know that the current size is pretty small. It will still be affected by buildings, but once we can build them with enough power, then a carefully selected band of frequencies would allow them to be far less influenced by the environment than a laser link would be. One just have to tell the troopers to not look into it... $\endgroup$
    – Mrkvička
    Feb 16 '17 at 12:15
  • $\begingroup$ @Mrkvička : Interesting.... $\endgroup$
    – Joe Bloggs
    Feb 16 '17 at 12:18
  • $\begingroup$ There's one other variant: scattered repeaters Like "fake them out", this requires multiple broadcasters, but instead of random noise, they repeat your broadcasts. With relativity, especially in space, they can still triangulate all the broadcaster locations, but cannot ID which one is the original sender. $\endgroup$
    – SRM
    Feb 16 '17 at 14:43
5
$\begingroup$

Well you could use CDMA which by nature allows signal to be perceived below noise floor like GPS on earth cannot be seen with a spectrum analyser .

Obviously if the enemy knows the codes used they could easily triangulate positions. The only safe bet would then be microwave or laser links but they would easily leave visual cues.

$\endgroup$
0
$\begingroup$

I would recommend a low powered mesh network with a very large number of nodes.

Since the individual transmitters would each be low powered they would only be detectable over a short distance making triangulation less effective. The short transmission distance would require a large number of nodes to be deployed in any area where the soldiers are going to be operating to allow data to be transmitted back to a secure area. I'm thinking a large number of throw-able or drop-able small breadcrumb like devices the soldiers could drop as they move through enemy controlled territory or small devices that could be deployed by drone or otherwise air dropped or even artillery delivered to blanket an area with tiny network repeaters.

The large number of devices would make it extremely difficult to target soldiers, you may be able to detect signals at short range, but that could mean soldiers are near or simply that the area is covered in repeater nodes, effectively not giving the enemy any useful information. You could even deploy nodes to areas with no soldiers as a diversionary tactic.

You would want the nodes to transmit some junk data even when no soldiers are present, otherwise the lack of signal or differences in signal quantity could be used to find soldiers active transmitters. With the data encrypted it would be impossible to tell fake data from actual soldiers data.

And while you are covering the battlefield in an active network, you might as well add some sensors to the nodes and use it for more than just monitoring the soldiers and get some active intelligence on the area.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.