This is, in part, due to the wireless infrastructure that is used between the major carriers... Verizon and Sprint, both use CDMA technology, whereas AT&T and Tmobile utilize GSM.
Originally, only GSM carriers allowed the use of mobile voice and data, to be used simultaneously (became seamless at/around 2003-2006). where as verizon and sprint, lagged a little, verizon gaining their support when they fully launched VoLTE... sprint still in a somewhat soft launch only allows it in select areas that have a good LTE signal.
I used to do signal testing for all carriers with a majority of sprint, and used to remember exactly how all the architecture works, but it's been over a decade...
09-09-2019 08:38 PM