A speech coder for aeronautical telecommunications

British Telecom International (BTI) has introduced an aeronautica/ telephone service known as the Skyphone. This service uses 9.6 kbit/ s speech codecs because of the limited satellite power available. Because of the need to achieve operation of aeronautical te/ephones between any aircraft and any ground station in any country, the technica/ specifications have been agreed internationally. After extensive testing of the various speech codecs proposed for the service by companies from severa/ different countries , the codec designed at British Telecom Research Laboratories (BTRL) was found to be the best and is to be used both for international te/ephony and for air traffic control. This paper gives a brief description of the Skyphone and the factors which influence the speech codec design and then describes the codec designed by BTRL for the service.