What's the difference between CDMA and GSM texting?

When sending short messages, the fw layer uses a class called SmsDispatch.javagsm, which implements gsmSmsDispatch, while cdma implements cdmaSmsDispatch. The main difference between these two classes is the encapsulation/parsing method of pdu. Because every short message is encapsulated in the form of byte array (pdu) before it is sent to ril, gsm and cdma are different in protocol, so different methods are used to encapsulate and parse pud. If the gsm pdu is simply sent by cdma scheduling, it may not fail, but even if the other party can really receive it, there is a greater chance of garbled code. And I remember that one of gsm and cdma doesn't need a header at all, and it will be 8 bits shorter. In fact, there is no need to change anything, just take gsmSmsDispatch as an example to obtain cdmaSmsDispatch. Before sending a text message, judge the card type (C or G). You should be able to get the id of the operator from getprop. This judgment is one way, but I think there should be a better way to get cards.