Introduction This document provides a description of the AMR speech service@ including speech coding@ channel coding and link adaptation. The following standards contain provisions which through reference in this text@constitute provisions of this Standard. At the time of publication@ the editions indicated were valid. All standards are subject to revision@ and parties to agreements based on this Standard are encouraged to investigate the possibility of applying the most recent editions of the standards indicated below. ANSI and TIA maintain registers of currently valid national standards published by them. ETSI TS references in this specification are specific@ in the sense that they refer to release and version numbers. If there are future changes that require changes to the channel coding or other parts@ this specification will have to be revisited. See Section 4 for specific references. Section 3 provides an overview of the AMR system. Section 4 describes the speech coding. Section 5 provides a placeholder for possible future noise suppression. Section 6 describes the link adaptation and inband signaling that control the mode adaptation. Section 7 describes support for tandem free operation (TFO). Section 8 provides a detailed description of the channel encoder. The channel decoder is not considered a part of this standard@ and may be performed with any method capable of decoding Recursive Systematic Convolutional (RSC) codecs and block codes. The implementations of the speech codec in the MS shall be bit-exact. Bit-exact implementation shall conform to the fixed point C-code@ see ETSI TS 126 073@ [2]@ and is subject to the test vectors defined in the ETSI specification for AMR@ see ETSI TS 126 074@ [ 3]. The implementation of the speech codec in the BS is not required to be bit exact; however@ non bit-exact implementation is subject to the minimum performance requirements for the AMR codec@ contained in TIA/EIA-136-240. Foating-point C-code is found in ETSI TS 126 104 [12] for reference. Performance characterization of the AMR speech codec can be found in ETSI TR 126 975 [16].