SIM7600与华为Y9数据漫游不稳定问题求助

Hi folks,

I'm dealing with a tricky data roaming issue on the SIM7600 MiniPCIe module, and I've run a series of tests across different devices to narrow down the problem. Here's the full breakdown:

Test Devices #

• Device A: SIM7600 (MiniPCIe) + MediaTek-based OpenWrt system
• Device B: Huawei E5172 CPE modem
• Device C: Huawei Y9 2019 smartphone

Network Context #

• The ISP SIM card's home PLMN is 44444 (fictional value)
• Target roaming PLMN is 55555 (fictional value)
• Roaming network uses FDD Band 3 or 1, which all devices support

Test Results & Observations #

1. Huawei E5172 Test:
   Successfully registered to the roaming network with stable data transmission. Confirmed the carrier has not whitelisted this device's IMEI, nor locked the SIM to a specific IMEI/modem.

   • Attached screenshot:

2. Huawei Y9 2019 Test:
   APN settings were configured correctly, and roaming was enabled. However, the roaming indicator only appeared for a short time (less than 1 minute), after which the device failed to connect and disconnected—no data transmission was possible during this window.

   • Attached screenshots: ,

3. SIM7600 + OpenWrt Test:
   Identical issue to the Huawei Y9: the module briefly obtains an IP address but can't transmit data. AT command tests showed:

   • AT+CREG? returned 0,6 (data roaming active) for a short period, then switched to 0,3 (registration rejected)
   • Attempting AT+COPS=1,2,"55555" had no effect
   • Attached screenshots: , , ,

I'm stuck figuring out why two devices (Y9 and SIM7600) can only get temporary roaming access before being rejected, while the E5172 works perfectly. Any solutions or troubleshooting tips would be greatly appreciated!

内容的提问来源于stack exchange，提问作者Amir Farahani