What kind of range/RSSi cutoff is expected from mdot to indoor gateway?

[laurent brunet]

Hello,

We’ve been running some tests with communication between mdot to conduit and between our third party device and the conduit. We’re wondering what kind of range and RSSI cutoff can be expected of the mdot and how can we maximize that. We’ve been cutting off at max -110 for the RSSI and it seems pretty low.

Thank you!

Laurent

[Peter Ferland]

Losing connection around -110 RSSI is typical. Regarding range, it depends greatly on the positioning of the gateway and node. The Conduit performs best when it is raised off the ground and the antenna is not close to any sheets of metal.

The longest advertised ranges are all unobstructed line of sight. If you have multiple obstructions (especially metal) between the transmitter and receiver range can be 500m or less.

[laurent brunet]

Thanks for the answer Peter, I have a few follow up questions.

We have an indoor gateway, I know there is an outdoor version too but I’m not sure if it’s just a difference in the casing for it. Is there an outdoor gateway with a better sensitivity than the indoor one we currently have?

Secondly, I don’t know if you’ll be able to answer this but let’s try anyway. We ran some test using lora communication between two devices and had rssi readings going up to -130 before cutting off, is there any reason the readings we’re getting for lorawan using a gateway are much bigger?

Thanks!

Laurent

[Peter Ferland]

The IP67 gateway is the same hardware inside. Other than the addition of a PoE injector for power and a rugged external antenna it is the same hardware.

I checked survey data for other locations and have indeed seen RSSIs reported for connections between an mDot and MTCDT down to -133. -110 is the cutoff seen when there are a large number of 900MHz devices near the gateway.

[laurent brunet]

Good, thanks a lot for the info. I’ll try to get some tests going with comparable conditions and see what kind of difference I’m getting. We were worried it was a different way of calculating the RSSI between both applications but it might just be that the conditions were different.

Laurent

[laurent brunet]

I just figured out we have a fairly strange behavior coming from the devices and I was hoping you could confirm what we think is happening right now.

When we run tests to see what kind of RSSI we are getting and to see the range we can achieve in our conditions, we realized that we go from receiving every single packet to receiving none in a matter of maybe 20 seconds. We send packets every 5 seconds +/- 1s. This also happens while our RSSI are still very much under the limit we would be expecting. For example, our last received packets today were around -95 on a clear day.

What we think might be happening is the path we’re taking to do our tests goes down in elevation slightly but possibly enough to make the direct line of sight to be blocked completely by the ground. Could that explain what we are getting? I feel like this behavior is really abnormal and those numbers are also pretty strange.

Thanks for your input!

Laurent

[Peter Ferland]

That is a strong possibility – LoRa (or any other 800-900MHz signal) will not make it through the ground very far! You can certainly see “dead spots” just like in a cellular phone network.

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