BG95 auto GSM/LTE RAT selection

Technical Subjects
1

Hello,

We are using BG95-M3 in our device, configured with AT+QCFG="nwscanmode" command to search for RATs both GSM and LTE (scan_mode=0). However, we see that when the modem connects to GSM, it strongly tends to stay connected with this RAT after many subsequent network connections (even with power down/up sequence in between), although LTE becomes and stays available. Then only forcing the modem with AT+QCFG="nwscanmode" command to search only for LTE (scan_mode=3), will result with modem being connected to LTE.

The problem with such forcing to LTE is that:

  • we do not know if LTE is currently available, and
  • we have very limited battery usage constraints.

As a result, we cannot just try each time assuming that LTE could be available to wait for network timeout connection from modem, only to switch it back to GSM after such try.

Is there a way to somehow change the RAT priorities internally in the modem, to make it try searching for LTE in a more efficient way? How does this network RAT searching actually work - does modem try to search for another RAT (especially more efficient RAT) itself, or is it up to the host to make such decisions?

Best regards

2

What does AT+QCFG="nwscanseq" return now, as your current setting?

Maybe try:

AT+QCFG="nwscanseq",020301 (M1 → NB1 → GSM) or

AT+QCFG="nwscanseq",030201 (NB1 → M1 → GSM)

3

HI,
Relevant operation documents have been sent to you, you can refer to the documents for debugging.

4

We have a similar situation (see Switching automatically to preferred RAT). Can you send the documents to me too?

5

Very similar issue here. BG95-M3 connected via eMTC (LTE) for months and then some network glitch or possible short network downtime made it connect via GSM. Module never recovered from this and stayed on GSM even though LTE is available. Module is completely power-cycled for each request, so this is somehow persisted.

Another module BG95-M3 encountered the same network glich and used GSM for a while, but then recovered to LTE.

What are those operation documents? could you share those with me? thanks.

6

Similar issues here, it might switch to LTE if it is in the mood, but nothing we do seem to make any difference.
@tabor.tang-Q could you send us the documents as well?