Evolution of Speech Coding for Wireless Communications
Gilles Miet · Kluwer Academic Publishers eBooks · 2006
The world-wide coverage of GSM-like networks led to an explosion of the number of subscribers, causing the saturation of some networks. Besides, the old technology used in GSM systems provided the customer with an unsatisfactory audio quality in many common situations. In parallel, DSP computing capabilities and the state of the art in speech and channel coding have improved. Therefore, to increase both the capacity and the quality of GSM networks, ETSI decided to standardise a new speech transmission system: the AMR. This Adaptive Multi Rate system is a combination of speech and channel codecs controlled by signalling means aimed at providing the best audio quality under background noise and transmission errors. The first part of this chapter explains this concept in comparison with current GSM coders. Another promising technology to achieve high quality speech transmission is wide-band coding. Therefore ETSI is investigating a wide-band AMR mode. The second part of this chapter presents the quality gain that can be provided by wide-band AMR. These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.