Joint source-channel coding with a redundancy-matched binary mapping in GSM speech transmission

The optimal binary mappings for converting the signal redundancy of the zero-th order (nonuniformity) and the first order (correlation) into individual bits are described. By employing a mapping matched to the residual redundancy inherent in the source-encoded parameters further gains can be obtained in the joint source-channel coding. The basic idea is to convert the residual redundancy of the source encoded parameters into the bit redundancy such that it can be more efficiently utilized in the channel decoding and the resulting parameters are less vulnerable to digital errors. The approach is successfully applied to the GSM full rate (FR) codec to achieve a more reliable transmission of speech signals