Wireless signal range is notoriously hard to estimate. Anybody who has setup a Wi-Fi router and experienced poor signal strength in areas of their home knows this. The maximum range for power-friendly LoRaWAN line-of-sight communications is often quoted at up to 10 miles, which translates into about 25x the range of Wi-Fi.
But any RF engineer would quickly explain that line-of-sight is the exception, and the 900 MHz signal used with LoRaWAN experiences increasing attenuation based on material thickness and density, whether the building is a glass skyscraper, wooden home, or masonry brick structure. The presence of metals, for example in reinforced concrete, can wreak havoc on signal strength.
So, with the large number of variables, how can I setup a LoRaWAN gateway at my facility?. How does a network operator estimate the number of gateways to roll out a LoRaWAN network?
The short answer is to follow the rules of thumb.: For urban areas, where multiple buildings may be in the way, you should get an average of 1 mile. For more open, rural areas, where trees and buildings are not blocking line of sight, expect to get 4 miles. But that all depends on several factors.
While LoRaWAN gateways are designed to provide economical coverage, sometimes there are trouble locations which just cannot get a good signal. In those situations, consider the following:
- The type of walls between the gateway and the sensor. Generally thinner, less metallic wall will allow greater signal penetration
- The topography of the landscape your transmitting across (hills and mountains)will block signal.
- Other 900 MHz communication in the area can reduce apparent signal strength
Regarding things that to overcome the obstacles at a particular gateway, here is a concise (though not complete) listing consider the following:
- Higher Quality antenna (you get what you pay for)
- Externally powered antenna.
- Height of your transmitting antenna in relation to your receiving antenna (placement is key, and higher is always better)
There are countless factors that go into LoRa range and sometimes the best way to get an idea for signal strength is to use a field test device. But with that said, it is good to know the limitations of any technology you use