TG Gateway VoLTE fix

With the shutdown the 3G some clients may have issues with 4G VoLTE calls.

Yeastar provide two solutions for this:

NOTES: 

• Before you fix the issues, insert the sim cards first.
• It is assumed the model is TGv3 - not applicable to TGv1
• The modems should be 4G/LTE capable (modem models EC20, EC21 or EC25). To check see this KB
• The fix is persistent across reboot however if you change the sim cards or insert new sim cards, you will need execute the AT commands or upgrade firmware again!
• 4G LTE Calls need enable "VoLTE" in the GSM trunks(Mobile List->Edit->Advanced Settings->Enable VoLTE)
• In some situations you will also need to hard set the network type to '4G only'
• You may get undetected sim cards issue after you fix it the first time, just click reboot on modules once or twice, or even better - reboot the gateway.

Option 1. AT Commands

Connect the TG with Putty, (SSH account is 'support', password is 'iyeastar') and to execute the commands below:

asterisk -rx 'gsm send at 2 AT+QMBNCFG=\"autosel\",1'
asterisk -rx 'gsm send at 2 AT+CFUN=1,1'

Option 2. Firmware

You can also upgrade to this version of firmware to fix the issue 91.3.0.21.48

Upgrade method https://support.yeastar.com/hc/en-us/articles/8629958998553-How-to-upgrade-the-TG-TA-TE-gateway

NOTE: You need upgrade firmware twice, first from your current version to 91.3.0.21.48, then from 91.3.0.21.48 to itself.