How far is REALLY LoRa’s range and why Radio Engineer will never commit to a distance?

How far is REALLY LoRa’s range and why Radio Engineer will never commit to a distance?

"What's the range of your LoRa modules?”

I’m often asked this question. Much to the regret of the questioner, I’ll usually reply with a barrage of questions: ‘What’s your antenna?’, ‘What's your data rate?’ and ‘Indoors or outdoors?’.

The truth is: I'm never going to give a straight answer. Don’t expect me to confidently exclaim ‘10km!’. Why? I'm a radio engineer and well, it's complicated...

What IS the range of LoRa? 

In this world of ‘spec wars’, companies are keen to advertise the highest possible number. In radio terms, that means free-air or Line-of-Sight, which represent the best possible conditions. Needless to say, those conditions are unlikely to be met in real life. Hence, I asked some friends at Semtech about the LoRa claims of range. They explained that the 15km figure you often hear being mentioned, originates from a series of measurements conducted by a team of very diligent Danes at Indesmatech. Obviously, these are still achieved under favorable conditions. In urban areas and in typical applications, you might expect much shorter distance. In fact, that figure would shrink to a kilometer or two.

Unless you’re Andreas Spiess and very determined. Then you can get more. Much, much more:  Andreas Spiess achieved a record breaking 211km when connected to a commercial LoRaWAN gateway in Switzerland. Watch this video to see how:

 

How to extend LoRa Range?

You probably won't be attempting to brake any records but there are some factors to bare in mind if you want to extend your range:

  • In radio, height is everything. You want some good, well-matched antennas, with a few obstacles.
  • Power helps. That is one reason why LoRa mobiles work so well (2W of energy compared to a few mW for typical Bluetooth).
  • Low frequencies i.e. longer wavelengths fair better. This is partly because they penetrate better (depending on the medium) but also because the antennas often are bigger and therefore collect more of the RF energy.
  • Space is good. Avoid large bodies of water, lumps of metal, forests, masses of concrete or lots of walls.
  • Don’t expect success with both ends sitting on or near the ground (the earth is curved after all)
  • ...and factor in the competition for (radio) space with other users.

How to calculate LoRa Range?

Here is a very rough rule of thumb to calculate the range for outdoors: take the best possible range, i.e. the Line-of-Sight figure and divide this by 10. For Indoor range: take the outdoor figure and divide it by a further 10.  Remember to pay attention to your antennas and what’s in between them and your range should expand.

Lastly, keep in mind the words of a great Scottish engineer : "Ye cannae change the laws of physics, capt’n"*  LoRa is a marvel, but there is only so much you can get at 868 MHz with a 25mW radio. In my opinion a few kilometers is still pretty awesome. 

* He also had the benefit of Dilithium crystals. 

Article by Stephen Clarke, Technical Director, Wireless Product

 

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