We have encountered a challenge a few times in Canada now where some cellular (EtherSim) devices seemingly have difficulty connecting or have very unstable connections at the end of coverage. At first we thought, ok we're just at the limit of the range to a particular tower, but then we noticed after some testing that the device was preferring to connect to a particular MNO, in this case Rogers (MNC 720), but that if we used an AT command to tell the unit to prefer TELUS (MNC 220) we suddenly got very good coverage. First question is why would that be? Why wouldn't the device choose an obviously much better signal strength tower than an unstable one?
Recently, we hit a new variation of this. We have a few devices in a coverage zone for SaskTel (MNC 780 expected), but the device is trying to connect to a Rogers tower with -126 dbm RSSI. We tried the same trick on a test unit to force connection to SaskTel as a preference. This time it doesn't work, the device is still connecting to Rogers after failing the request and falling back to a auto-connect setting. Can anyone help us arrange a smarter connection method, where the device will prefer higher RSSI/Qual tower contacts, and also are the SaskTel settings of 302 780 going to work under a Particle EtherSim? Thanks!
The carrier selection is controlled entirely by the modem and SIM and is not strictly based on strongest signal. Unfortunately the preference algorithm cannot be changed.
The reason Sasktel can't be manually selected is that the EtherSIM does not have an agreement with Sasktel.
Forcing a carrier can lead to your device getting banned by local towers, so we'd highly discourage you from doing so.
The SIM has a carrier priority list and will cycle through the available towers - changing the IMSI and switching carriers takes about 3-5mins, so you need to give the device enough time for that to happen. Generally a device will stabilise after a day or two once it's had a chance to run through the local options.
I appreciate the point being made, be assured that and this is not a normal course of action for us. In the other situations where we have forced selection the performance was so degraded from the initial selection that being banned wouldn't have been an issue really. I'm thinking of one instance where we saw only 10% or less of hourly connection attempts as successful. Forcing the selection raised the success rate to near 100%. We were very confused as to why the modem would choose as it did and had been fighting with the cell issue during a customer pilot for around two weeks leading up to the firmware change as I recall. So we'll keep it in mind and be careful about employing this approach.
Thanks, I suspected that was the reason with SaskTel. In Saskatchewan, Canada Rogers covers major highways but this leaves vast areas of the province without coverage other than SaskTel, who traditionally has had ubiquitous coverage on prior generations (3G/LTE Cat1). LTE-M is a different story unfortunately, but this area was well covered so I had hoped forcing the MNC would be a solution.
Lack of SaskTel support is a greater business concern though, since we have a number of customers in this area already suffering from poor signal reliability on the E402 solution compared to alternative cellular modems. Do we have some options to handle that, now or as we consider EtherSIM+? After dropping 3G support, we ordered a number of E310s which were performing better, but this geographical area is now presenting a challenge for our business to service. Any suggestions on how to best proceed?