How the cellular network works? - GSM Architecture

The Process Behind Sending An SMS Message Using A 2G GSM Network. ... as without VoLTE you wouldn’t be able to make or receive calls in places with a 4G signal but no 2G or 3G. You might think that would be a rare occurrence, but some of the frequencies that 4G operates on, such as the 800MHz spectrum, have far greater reach than 2G or 3G ... ................
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