00000cab a22000003a 4500 UP-99796217609624721 Buklod 20231007234508.0 m |o d | ta 110119s xx d | ||r ||||| || DENGII eng Bo Wei Application of NB WB AMR speech codecs in the 30-kHz TDMA system. pp. 1897-1901 A new system enhancement method is proposed for the EIA/TIA-136 system offering both channel operational range extension and improved performance within the current operational range. The existing time-division multiple-access (TDMA) (136) speech codec, the IS-641 enhanced full rate vocoder, operates at a fixed bit rate and does not allow the reallocation of bits to channel error protection as channel conditions degrade. The research presented here investigates the application of the narrow-band adaptive multirate (NB-AMR) speech codec and the wide-band AMR (WB-AMR) codec, both originally designed for the 200 kHz GSM channel, in the TDMA (TIA/EIA-136) 30-kHz system. In particular, we investigate adaptively allocating bits between NB/WB speech coding and error control coding within the limited channel bandwidth. Four modes out of 17 have been carefully chosen for the new TDMA/AMR system. Switching between codec rates as channel conditions change produces range extension below a C/I of 15 dB while also improving performance in the existing operational range above 15 dB. We keep the time slot formats unchanged so that our method is completely compatible with existing 136 systems. 200 kHz. 30 kHz. GSM channel. TDMA system. Channel error protection. Channel operational range extension. Error control coding. Full rate vocoder. Narrowband adaptive multirate speech codec. Speech coding. Time-division multiple-access. Wideband adaptive multirate codec. IEEE Transactions on wireless communications 3, 6 (2004). FO UPD DENG-II Article