why some cost UE cannot connect to srsran_4G

[faratell]

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I implemented a 4G network using srsRAN_4G, USRP B210, and Open5GS. The PLMN of my network is set to 00101. I used oyeitimes SIM cards. for EARFCN=1650, I tested various COTS UEs with the following results:

1) Samsung F13, A3, s23: Successfully connected but Samsung Galaxy Note 4, Failed to find APN and could not connect
2) Nokia 3.2: Successfully connected
3) Honor X9b: Successfully connected
4) Iphone 13:  Successfully connected
4) Xiaomi Mi A2 and two other Xiaomi models: Found APN but failed to connect
5) Huawei Y8p and one other Huawei model: Successfully connected and supported VoLTE

The results show varying degrees of compatibility across different smartphone brands and models with the implemented 4G network. While most Samsung, Nokia, Honor, and Huawei devices successfully connected, the Samsung Galaxy Note 4 and Xiaomi phones encountered issues. Notably, only Huawei devices supported VoLTE functionality for my network. Now my question is that: What causes these phones to behave differently on our network?