Accroding to docs from GSM fundamentals and practical behavior which I have read, there are two types of “ERROR Correction Coding”:
Backward error correction & Forward Error Correction
-Backward Error Correction: if check bits are correct, it’s assumed all the information are correct, but if check bits have problem, then AUTOMATIC REPEAT REQUEST enabled -> It’s more used for dat and not suitable ofr speech
-Forward ERRO Correction:
it’s in two types and in GSM used a combination of them: *Block codes *convolutional codes
….brb