How does my military communicate if satellite communications is impossible and sky wave is unreliable

Question

On a planet that resembles Earth, long wave radio communications face some challenges. Satellite communications (SATCOM) is impossible as it is impossible for the inhabitants to send anything up into space despite having near future technology due to a particle cloud layer. This particle cloud layer came a while after radio communications and satellites were developed and created.

Starting at around 50km altitude (around the start of the D layer of the ionosphere), this cloud extends upwards. Slightly past the ionosphere, the particles that make up the cloud layer violently react with anything climbing altitude. Stripping/tearing apart anything that rockets past it. For reference, a Saturn V would be torn apart in seconds. Despite humanity's best efforts, they haven't been able to send anything into space, let alone past the upper Mesosphere (85km). For cruising altitudes, one can safely assume that anything past 50km will start to feel major vibrations and face some surface level damage. Going higher will cause damage and tearing of a rocket or aircraft at an exponential rate.

While SATCOM is useful for long range communications, it isn't the only method. Before the advent of satellite communication, we relied heavily on bouncing radio waves off the ionosphere (especially the D layer) between a transmitter and receiver. Aka sky wave. However, the particle cloud interacts with radio communications as well. The suspended particles in the cloud can have a variety of effects on a radio signal. Sometimes it does nothing, sometimes it causes the radio signal to reflect at a different angle, completely missing the receiver. Other times the signal is shot up straight into space. The effects are determinant based on the types of particles colliding with each other in the sky during the moment of transmission. All this means that while sky wave works at times, it's not reliable enough for military operations.

The majority of the planet's internet/communications system relies heavily on wired connections and base stations for civilian use. For basic cellular or radio electric applications this is fine since one can utilize multiple base stations. Sky wave communications is used by civilians at times, however a receiver may not be able to send a verification message back (two generals/exactly once delivery dilemma) at times.

However, for the military this is problematic. Long range communications are important. Especially in a modern battlefield where military units are maneuvering while working together with multiple other branches. Even moreso if a faction is operating far from home. Chancing sky wave by bouncing radio signals against the ionosphere is simply too risky to use. It may work at times, but it may also not work for a couple days. As such they need alternative methods of communications.

How would my military communicate across both short and long ranges if SATCOM and sky wave is impossible and unreliable respectively?

Notes:

1. Line of sight radio communications work perfectly fine.
2. Radio existed far before the particle cloud set upon the planet. Infact, they had capabilities to send basic satellites into space. However, after that they have never been able to get back into space or use the ionosphere for radio communications reliably.
3. In terms of scale, a faction needs to be able to communicate across oceans or continents somewhat reliably. They don't need real-time data uploads, but reports and top level orders do need to be able to be sent.
4. The system doesn't have to give the exact same resolution or scale as existing SATCOM or skywave communications. It just has to be good enough for the military to operate overseas or across their country during defensive operations.
5. Technology is near future.

Answer 1

It depends on what you mean by "long range", and what you actually need to do.

Ground wave propagation of longer wavelengths can give you considerable range (hundreds of kilometers), if you use the right equipment. The longer wavelengths involved are inconvenient because of losses associated with having horizontal antennae too close to the ground (it'd be nice to have your 80m-wavelength aerial at least 40m up, for example) and vertical antennae can be inconveniently tall, but temporary transmitting stations could be set up using vehicle-based systems that could be erected and dismantled quickly when needed.

Remember these things can be asymmetric, with big antennae and powerful radios a decent way back behind the front, that can communicate with smaller and less powerful equipment even when those smaller devices can't communicate with each other.

That's positively ancient technology though, and the sort of thing that could be cobbled together by hobbyists these days. Bandwidth is extremely low and antenna requirements are awkward. Because you can't practically have a directional radio transmission with such low frequencies, it makes it harder for multiple users to communicate at the same time without interference, and easier for radio direction finding systems to hunt you down.

(photo credit: US army via wikimedia)

A somewhat more modern and high-tech approach would be to do use microwave tropospheric scatter. The troposphere is comfortably below your macguffin layer (20km vs 50km) so it is unaffected by ionispheric shenanigans. Troposcatter can have ranges of up to 1000km in ideal conditions.

This has been used for military communications in the recent past... NATO ACE-High was retired in 1995 as satellites had made it obsolete. Stuff like the AN/TRC-170 (pictured above) was developed in the late 80s and is still occasionally used even now, providing a few hundred kbps bandwidth over 150 kilometers. Modern equipment is still being specified and developed, presumably in case satellite communications become disrupted. I found this US army troposcatter project spec dated 2017, and looking at bandwidths up to 50Mbps and ranges up to 170km.

Many such devices could be deployed over a large area using air and ground vehicles, and provide a fairly robust and high bandwidth mesh network that seems like it should be able to do what you want it to. Multi-hop communication links are easy to arrange with modern technology so the range can be extended as far as you can safely advance the transceivers. The beams also are much more tightly controlled with much less spread, making it somewhat harder to detect them, and more awkward to interfere with them

Answer 2

Aircraft would be a major component of their communication system

When using line-of-sight radio, you can reach farther by putting your transceiver on a taller tower. Even better, put it on top of a mountain. Better yet, put it in the sky. Satellites in outer space would be nice, but if you can't have those, you can use aircraft up to your maximum safe altitude. Each aircraft could act like a radio repeater, relaying signals across the breadth of the Earth it can "see". If you had a bunch of them, they could form a mesh network that passes signals around a wide area -- perhaps all the way around the world.

Depending on the enemy's ability to shoot down your aircraft, there are a few different design approaches to this surface-to-air-to-air-to-surface network. One approach would be to use jets that fly high and fast and on unpredictable courses so that the enemy can't shoot them down, or so that they're gone from the enemy's radar before he can react. But my preferred approach would be a huge fleet of cheap repeaters in the form of weather balloons or dirigible drones -- small enough that it's difficult and expensive for the enemy to shoot them, numerous enough and cheap enough that even lots of losses can't take down the network.

Answer 3

The decade before ...

Say they were at something like 1950s technology. That would include HF radio for long-range, mobile use, and undersea telegraph and telephone cables. The infrastructure exists, it is used commercially and for military purposes. The military may have their own, hardened phone and telegraph lines, and they have big short radio stations connected to the landlines. For navigation, they have things like LORAN.

The day before ...

You mentioned the first sats. Early ones merely beeped from space to prove that they were up. Then at some point there were the first communications sats. Bandwidth is not nearly enough to replace the previous systems. No GPS yet.

It happens!

The loss of the nascent commo sats has no great impact, because they used to be a novelty. The loss of HF radio will have significant immediate impact. Civil air travel gets grounded, or at least much less common?

Onwards from the departure.

Civilians will not get satellite TV. The technology for transoceanic cables gets improved. An incentive to go to fiberoptic much earlier?

The military goes for hardened, redundant cables and also radio relay stations. There is a great incentive to develop automated switching and relay technology, each unit in the 'network' receives digital messages, validates the header, and sends it onwards. If you think about the nature and origin of the internet protocols, you may note a similarity ...

At some point, LORAN-like receivers become smaller and more lightweight, transmitters become smaller and more common. That could be integrated with a cellphone network. So in a big city, smartphones work as we know them, but in rural areas there are gaps in navigation and not just in communication. The military develops a readily deployable, encrypted, hardened system on that basis.

Answer 4

Very Low Frequency or VLF can transmit through the earth itself. The antenna arrays for transmitting are very large, for receiving they can be a little shorter, but stil a long wire is required. They were developed to communicate with Subs that were underwater. Also the transmit very slowly sometimes several seconds for a single character. In practice only short messages were sent.

https://en.wikipedia.org/wiki/Very_low_frequency

Answer 5

Why not laser communications. Use the particle cloud as a relay. I shoot a laser into it, encoded with a message, you read the message and can answer back the same way. Everyone can see the message but this is why we have codes.

Not sure if this is the right way to calculate the range but online calculators say that for a balloon 1km in the air, the horizon it sees is 112.9km away. So ideally, anyone 112.9km away from that balloon would be able to see a laser bounce off of it, if they weren't obstructed by anything other than the curvature of the earth. At 50km, the distance to the horizon is 800km. So in theory, if I fired a laser straight up into this particle cloud, you should be able to see it from 800km away-ish? (Actually I guess that's distance-from-the-reflection, not distance-from-the-source. Eh, no one said there'd be math...) I should be able to cover even longer distances by firing it at an angle. Using infra-red should enable it to get scattered less by water vapor (clouds). I imagine the scattering would confuse the reception of the signal but I feel like it's a solvable problem and you could get a coherent message this way.