Troubleshooting LTE keeps disconnecting
Since I first posted in April I did some testing trying different routers, a secondary location and two other operators (Telekom and Digi).
Also I discovered later that phone calls also get interrupted sometimes. So the router reconnects automatically when needed but only phone part.
Testing on 5G was not possible since I don't have 5G coverage.
As for 4G, the only available band at the primary location is band 20 (FD 800 MHz), so testing on another band, again, is not possible.
Signal quality with two -16 dB logarithmic antennas is 75% at between -97 and -101 dB (it varies). These are mounted on the roof of my house.
All of the above is valid for operators Orange and Telekom.
Below is a picture of the router when disconnected from the internet.
In this state I can make and receive phone calls without fail (when connected to the Orange network).
Calls sometimes get disconnected but during the call only.
First test I did was taking the NV510 to a secondary location with better coverage, and reinstalled the old Huawei E5186 at the primary location.
At the secondary place I only had acces to a set of -8 dB antennas that I plugged directly into the router but the signal quality was similar with that at my primary location (75% at about -99 dB).
I kept the TP-Link there for three weeks on Orange during witch time I did not experience any disconnects. Not even once.
I then decided to take the router back to the primary location and try a Telekom pre-payed sim.
Since I needed acces to my Orange phone number that was in the Huawei, I put the Telekom SIM in the TP-Link and connected only one -16dB antenna to each Router.
I monitored the TP-link through Aginet app for about three weeks and every time I checked, the router was online. So apparently, at the primary location, on Telekom, the router din not disconnect.
I concluded that there must be some compatibility issue with the antennas that Orange uses on the particular tower where I get coverage from at the primary location.
I then decided to transfer my main Orange number to Telekom.
However,
After installing the freshly transferred SIM into the TP-Link I discovered that I could not make or receive phone calls. I'm on the Telekom network now, witch was supposed to be OK.
After buying another router (Tenda 4G06) I discovered that the TP-Link does not support VoLTE on the Telekom network.
When trying to make a call it attempts to make it through UMTS and since there is no 3G coverage in the area it can't make the call.
The Tenda is also VoLTE compatible but it goes to 2G to make the call when connected to the Telekom network.
Telekom offers VoLTE services. I tested on my phone so it is available, just the TP-Link router can't use it for some reason.
The third operator I tried (Digi) was for testing purposes only because their coverage is very weak in the area and it's not a viable solution in the long run.
So far, at the location where I use this router my results are:
On Orange - I get VoLTE calls but frequent disconnects.
On Telekom - I get a stable internet connection (no disconnects) but no VoLTE
On Digi - I get VoLTE calls but I can't test for disconnects because of weak coverage.
My uneducated guess is that there is a problem with the VoLTE part of the router.
As for the Tenda I returned it because of horrible sound quality on the phone line.
I also tried a ZTE MF289F witch I returned because it didn't support VoLTE calls, although it was advertised as compatible, and not being 2G compatible, witch meant I couldn't have tested it for a long time, before the return period would have expired.