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I'm currently working on a project that involves establishing a reliable non-line-of-sight wireless communication link with a range of 1 kilometer or more. The project does not have internet access, so it requires self-contained solutions. While I've considered LoRa for its long-range capabilities, I've encountered difficulties finding reliable LoRa solutions for non-line-of-sight conditions over such distances. I'm seeking guidance on communication protocols and any alternative technologies that could address these challenges effectively.

  1. Location: Remote location cover with trees. The controller will be placed inside a house.
  2. Range: 1 km.
  3. Condition: In non-LOS condition need to control two stepper motors with pan and tilt mechanism. It's a one way communication.
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  • \$\begingroup\$ Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. \$\endgroup\$
    – Community Bot
    Commented Sep 29, 2023 at 5:29
  • \$\begingroup\$ This is not the place for suggestions what equipment to buy, You should have a specific question in mind, to get good answer. There are forums available for the type of advice you're looking for. Good luck. \$\endgroup\$
    – MiNiMe
    Commented Sep 29, 2023 at 5:32
  • \$\begingroup\$ You will have to specify and disclose what in particular needs to be communicated. One way or bidirectional? Allowable latency? Consequences of communication errors? Required bandwidth? The IP protocol suite works without connection to "the" internet. \$\endgroup\$
    – greybeard
    Commented Sep 29, 2023 at 6:46
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    \$\begingroup\$ "Non line-of-sight" communication is a very wide class. What's in the way? Can you place any kind of repeater to make two (or more) line-of-sight links? Can you place any kind of reflector? Or use a building or something? And as @greybeard says. what speed, latency? What amount of reliability? Engineering is a numerical endeavour, even if we often start with wide estimates. "1km or more" how much more? How big can your antennas be? Sat radio? Moonbounce? \$\endgroup\$
    – jonathanjo
    Commented Sep 29, 2023 at 7:09
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    \$\begingroup\$ What is your power budjet and antenna size constraint \$\endgroup\$
    – Autistic
    Commented Sep 29, 2023 at 8:07

2 Answers 2

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As mentioned in the comments your question should include latency / bandwidth requirements. It sounds like the link budget is not known and may not be easy to determine. The following solution has been successfully deployed to provide a reliable battery powered network enabling monitoring of the snow pack depth in California. It has the benefits of simply deploying devices as repeaters to increase the reliability should it be required. It is limited to low bandwidths though. ADI includes a power estimator so you can have a good idea of your power budget / battery lifetime which is a function of bandwidth. The solution is very robust, I've used it myself.

https://www.analog.com/en/applications/technology/smartmesh-pavilion-home/smartmesh-ip.html

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As, unless they bounce off something, radio signals travel in a straight line, there is no magic solution when you don’t have line of sight.

Either there is terrain in the path (hills) and it won’t work at all, or there is “just” vegetation and then it will most likely be very unreliable, varying with seasonal changes to vegetation and with weather (rain or snow, but also in some circumstances temperature gradients).

So, some available solutions involve:

  • Laying down fiber. This is the most reliable solution. There are other questions which deal with the requirements for the fiber link, to make sure it won’t get damaged. Once you have fiber you can run Ethernet and do whatever you want. You will need power at both ends.
  • Laying down copper cabling. Same issues with protecting the cable, and you can’t run standard Ethernet on that. There are quite a few solutions suitable for those distances, though.
  • If none of the wired solutions are possible, the only other reliable option is to avoid the obstacle(s). This could involve:
    • just clearing a path in the vegetation (and keep it clear over time)
    • Setting up the antennas on masts, so your line of sight stays above the obstacles
    • Make a detour around the obstacles, with one or more additional sites with repeaters along the way. It may involve a single repeater or many.
    • Possibly just bounce the signal off a reflector, but this is probably more in the realm of magic

The exact technology will depend on your requirements in terms of bandwidth, latency, power, distance and cost. It may also depend on local regulations and licensing requirements. It may involve WiFi, WiMAX, BLE-LR, LoRA, HaLow, microwave links, laser, and probably a dozen more.

Note that unless you go laser, “line of sight” should include the Fresnel zone, so you need additional clearance around the specific line of sight, which depends on the frequency and link budget.

It may be possible to use radio technologies which bounce on the ionosphere, but that goes into HAM territory, and I’m not sure at all what the reliability on that is (nor if it can actually work for such short links, it’s generally used for extremely long distances).

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