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I've started a little side project with the goal of tracking my cat's location in real time. To transmit the GPS-data, it seems like I have two options: I can either use cellular communication or (hopefully) peer-to-peer. I wanna use P2P because I don't want ongoing costs. However, from my online research, I can't really estimate the maximum range I could achieve P2P yet. My specifications would be as follows:

Transmitting antenna: would be mounted in the cat's collar

  • size: has to fit in a collar of shape ~3 x 25 x 1 cm
  • power consumption: as low as possible
  • bandwidth: around one location ping per minute, so probably 30-40 bits per second (or higher bandwidth and fewer transmissions if this reduces power consumption)

Receiving antenna: would be sitting at home

  • size: "as big as it needs"
  • power: "as high as it needs", can be plugged in
  • range: cat is expected to wander up to 5 km in the suburb

I've read about LoRa and similar technologies that seem to come closest to what I need. Unfortunately, LoRa "only" has a range of up to 10 km in line of sight, which apparently drops to ~1 km in suburbs. Also, all existing pet trackers use cellular communication (although it seems like the products weren't updated in over a decade and they want to make money selling their cellular subscriptions).

So my question is: Do any of you know a way to achieve P2P communication under said circumstances? Can I even achieve this with radio? Or is there maybe any new technology I am missing (maybe also free open network I could use)?

Thanks a lot!

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  • \$\begingroup\$ 5 km in suburbs is hard. But Wiki has this site that lists the competing technologies you may want to consider more closely. No matter the choice (or if any will work for you), you will also need to be extremely good at programming MCUs for extreme low power use. The RF is what's going to mostly cost you in Joules per packet sent. But the MCU may start to count if you don't know how to properly program one for ultra low power. (A housecat isn't big. I like bobcats because I've had one. They are a little bigger though.) \$\endgroup\$ Commented Jul 11 at 0:42
  • \$\begingroup\$ I just noticed that the first-referenced article on that Wiki page may be helpful, as well. \$\endgroup\$ Commented Jul 11 at 0:49
  • \$\begingroup\$ Quick Google search suggests the 4g SIM card route would cost you 5-15 dollars per year depending on region and network. Maybe less if you shop around. I think it will be hard to build a LoRa receiver for less than that over the range you want. \$\endgroup\$ Commented Jul 11 at 14:39

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You read about LoRa, so I'd guess you already stumbled upon the answer: faced with the problem that a low-power transmitter can't get data reliably across a channel of large distance, you reduce the distance. LoRa's approach to that is meshed; see LoRaWAN.

You'd do the same. People might expect you to pay for network access, either way, or you might be allowed to use the mesh for free, depending on operators and technology.

Also, don't know what you mean with "ongoing cost" of cellular communications. For low-speed low-volume M2M comms, you buy a subscription (manifest as "a SIM"), which usually comes with something like 10 years of network access and somethink like up to 1 MB of data per day/week/month/year (depending on the upfront cost). You'll want to research "NB-IoT SIM" or "Cat-M SIM".

Note that bundling GNSS and cellular technology in one SoC might be cost-efficient, anyways.

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  • \$\begingroup\$ Thanks a lot. As also suggested by the two commentators, NB-IoT SIMs are probably the way to go. \$\endgroup\$
    – bns
    Commented 4 hours ago

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