A 6.3 kb/s CELP codec suitable for half-rate system

A codec scheme suitable for the GSM (Group Special Mobile) half-rate system is proposed. The source coding has been performed with a CELP (code-excited linear prediction) algorithm, which provides good speech quality at low bit rates. In order to fit the recommended speech of 11.4 kb/s for the traffic channel, a 6.3 kb/s CELP codec and a FIRE protecting scheme adding 5.1 kb/s of redundancy were used. The real-time implementation is based on two PC boards connected via the PC bus: this makes it easy to test the system functions. The speech quality is almost the same as that of a full-rate codec on a wide range of experiments with different speakers and different languages. Channel error effects are considered.<
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