Underground LoRaWAN signal Test

1

Hello everyone, 2 weeks ago i was testing the RSSI of the LoRa signal in a factory that is placed underground. the Gateway was installed on the ground floor, I walked around with a LoRa tester device. i was expecting to get a good signal since the distance was < 1Km, however I was not able to catch any signal at the place where I was intending to install the LoRa Nodes.

My 1st question is:

is there any special installation steps that I should take care of when I’m installing an underground LoRaWAN System ?

2nd question, Although i configured the Tester to use the ABP Join method, however, i noticed that the device doesn’t join the Network unless i reset the counter of the Gateway(I used the internal Gateway server here).

Thank you

2

You can only realistically use a huge cavernous space full of air - as that’s best for radio waves - lots of iron work or solid rock tends to block them.

Without knowing what “internal Gateway server” you are using it’s hard to advise but as TTN don’t make one, this would technically be off-topic for this forum which is TTN only.

3

Not really.

As with most installations nodes and gateways should ideally have antennas as high as possible, free from obstructions and close to windows if appropriate.

Buildings with their walls and floors tend to attenuate radio signals quite a bit so you would expect range to be reduced, possibly significantly.

4

Hi Nick, i was using TTN but i tested some measurements by changing the Webserver to see if the problem is from the LoRa connection or the web connection.

Thank you for the suggestion.

5

This would only be true if you were using a WiFi gateway with the WiFi router on the surface …

6

Hi , But in my situation the building looks something near to this (except that the upper level is a closed

room with walls):

image

what i mean to say is that i’m searching away to make the signal penetrate through concretes and

(large wine bowls) underground. the distance is actually <200 m even but yet i can’t get any signal

down there.

7

My apologies, i didn’t explain it well. the gateway supports the internal webserver (beside the normal packet forwarder). so i tested the TTN 1st , then i though maybe the gateway doesn’t send the received packet correctly to TTN (the gateway supports Wifi connection to the router).

8

And where is the router?

And whilst you aren’t giving any detail, please don’t tell me what the gateway is either, it could only help the situation progress.

PS, where can I buy one of these underground lairs?

9

There is not a legal way to make the signal penetrate concrete better.

10

I used the Mutitech conduit AP(with internal webserver) & also dragino (LG308). the router and the gateways are in the same Room (ground level), sensors (& the tester) were like 300 - 200 meters apart but underground.

The picture is just to clarify the situation (but i agree they are very attractive).

11

wow, the thing is that i tested LoRaWAN in a dense area and i was able to reach 2.5 Km away. but now i can’t get around few hundred meters away. i though maybe some antenna configurations can make difference.

12

Given your hardware doesn’t have a gateway server on it, what is this then that may allow you to reset the ABP counter?

Do you mean you were looking at the gateway logs for uplinks? Which would suffice for checking for signals.

And given the rather closed system, why use LoRaWAN?

13

Nope.

The nodes are very likley already at the maximum legal radiated power, so using ‘better’ antennas would be illegal.

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14

yes i was checking the Log (in the internal webserver case)

As i remember if i’m using the ABP, i don’t need to reset the counter for every Node reset (as in OTAA) , No?

15

You’ll have to set that on the device console.

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16

???

If you tell us the use case, maybe we can help.

17

The system is intended to monitor the environment of a place where Wine bowls are stored. the place (as mentioned is an underground level). The previously installed system was using Wifi technology but the infrastructure consumes time (and cost) to be built the router must be near the sensors (which is not always easy to be done).

we are testing the LoRa now to come across the range (and the power) issue.
The main reason for the post is that I wanted to make sure that I followed the right way to test the technology so the final decision would be correctly chosen.
Honestly, I was expecting LoRa to achieve more than that.

18

Yeah, people do that. If the facility had large open spaces and not a whole pile of (metal?) containers with all the infrastructure required to keep the roof falling in, you may have a fighting chance.

You may want to look at the nRF24L01 which is ISM on 2.4GHz so possible (subject to any observations from @LoRaTracker) a better choice for penetration. You can do a 5 devices to one ‘gateway’ config quite quickly, so not as convenient as LoRa. But entirely off-topic for LoRaWAN, except 2.4GHz is supported on v3 but I don’t know about the radios yet.

I’d be happy to come over for a site survey - particularly if you are near to Biella as I haven’t seen my friend in a while and I do like the wines in the Piedmont region.

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19

Just to be sure you don’t have some other hardware problem, I would suggest you return the “dense area” where you previously tested and make sure the hardware still works and reaches 2.5Km again.

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20

TTI, as I recall, have been pushing the 2.4Ghz LoRa devices for use in Worldwide applications such as on ships. The Gateway is 3 x SX1280 devices as I recall.

The range of 2.4Ghz nRF24L01 is pathetic when compared to 2.4Ghz LoRa, for this type of application.