The reason for this phenomenon is the patent limitation of communication baseband.
The patent of telecom CDMA technology belongs to Qualcomm, but the patent fee in Qualcomm is very high. At present, CDMA is no longer used in telecom's 4G network, and telecom calls and SMS services still rely on CDMA baseband. If a mobile phone pays a dual baseband fee, the mobile phone manufacturer can only install one CDMA baseband.
Extended data:
The three major domestic operators use baseband.
Dual card dual standby can be divided into dual mode dual standby, dual network dual standby, dual standby single pass, dual standby dual pass and so on.
1, GSM (2g)/TD-SCDMA (3g)/TD-LTE (4g) used by China Mobile;
2. China Unicom uses GSM (2g)/WCDMA (3g)/TD-LTE (4g)/FDD-LTE (4g);
3. China Telecom uses CDMA1X (2g)/EVDO (3g)/TD-LTE (4g)/FDD-LTE (4g).
References:
Dual card dual standby-Baidu Encyclopedia