Using insertion convolutional code for speech transmission over GERAN 8PSK voice bearers

Lower rate codes can be constructed from a high rate code by inserting known dummy bits into the information bit sequence before encoding. These so-called insertion convolutional (IC) codes can individually adjust the amount of protection given to the information bits, and can be decoded using the same decoder as for the mother codes. We employed the recursive systematic insertion convolutional (RSIC) codes in adaptive multirate (AMR) speech transmission over GERAN (GSM/EDGE radio access network) 8PSK half rate (HR) voice carriers and good results were obtained. The unequal error protection (UEP) necessary for differently important speech encoded bits is realized and optimized by employing different rates of channel codes, followed by a systematic mapping of code bits into strong and weak bits of 8PSK symbols. As a result, the scheme for AMR speech transmission over 8PSK HR voice carriers significantly outperforms the scheme over GMSK HR voice carriers