I have a mobile wireless router (PW100 4G LTE Router) that provides WiFi via a SIM card. I have purchased several data “bundle codes”. One way to activate a data code is to send a USSD code: *101*CODE#
The router’s interface provides a USSD Service interface through which I should be able to send these USSD codes.
When I attempt to load a bundle code, or to check my balance by submitting the USSD code *101#, the site hangs and eventually prints out: “session terminated by network”
If I place the sim card into a phone I am able to issue the USSD codes without problem. So, it is the wireless router that is not properly managing the USSD connection.
I have been trying to troubleshoot this with no success. Do any of you here have experience with WiFi routers, or with USSD codes in general, and might have some suggestions of things I can try?
Eventually I was able to confirm this. Using software-defined radio I was able to see that the USSD codes send out a signal in the ~895 MHz range, which is allocated to the 2G GSM by my provider.
I purchased a batch of SIM800L chips off ali express and those work without problem for issuing the USSD codes. I can also see that they emit the same signal at 895 MHz.
I kept looking into it and I have found that the SIM7600 chips have 2G, 3G, and 4G. So I have ordered a dev kit that uses the SIM7600 chip and I am going to use it to build a little raspberry-VoIP station, and I can also use this station to issue the USSD codes when needed.
It would still be nice if I could issue the USSD codes directly from my MiFi, but I have not been able to find a comparable MiFi that runs 2G and LTE… So I still need to take the sim card out of the MiFi to top it up, but it is progressing.