The present invention includes a time-division-multiple-access (TDMA) communication system having a base station and at least one mobile station, each transmitting and receiving an analog radio-frequency signal carrying digitally coded speech. The speech is encoded using a vocoder which samples a voice...http://www.google.com/patents/US6529730?utm_source=gb-gplus-sharePatent US6529730 - System and method for adaptive multi-rate (AMR) vocoder rate adaption
