TIA/EIA/IS-641-A:1998

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TDMA – Cellular PCS – Radio Interface Enhanced Full-Rate Voice Codec

Published By	Publication Date	Number of Pages
TIA	1998	NA

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Category: TIA

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Description

Preface

This document gives a description of the Nokia/JSH speech and
channel codec for the TIA IS-641 Enhanced Full Rate Codec. The
codec consists of a 7.4 kbit/s ACELP speech codec and a 5.6 kbit/s
channel codec (Forward Error Correction).

Section 1 gives a general description of the speech coder and
sections 2 and 3 give more detailed descriptions of the speech
encoder and the speech decoder, respectively. Section 4 gives a
detailed description of the channel encoder. The channel decoder in
section 5 is not considered as part of this standard. The bad frame
masking described in section 5. 1 is provided as an example
solution; other solutions are allowed. Section 6 gives a detailed
description of the different aspects of Discontinuous Transmission
(DTX). The bad frame masking described in section 6.4.4 is provided
as an example solution; other solutions are allowed.

This standard consists of this document and a soft copy
distribution comprising four diskettes. These contain a bit-exact
description in the form of a fixed point ANSI C code and a number
of test sequences. The C code defines the speech codec and the
channel encoder with a set of fixed point basic operators. The test
vectors are described in Annex A. A detailed description of the
contents and formats of the soft copy distribution is given in
Annex B. The details of the instability protection for the speech
codec are given in Annex C. Annex D describes a reference design of
a voice activity detector (VAD) which may be used to implement the
DTX mode of the speech encoder in the mobile station (MS).

MS implementations shall be bit-exact. Bit-exact implementations
are subject to the test vectors specified in this standard. Base
station implementations are not required to be bit-exact. However,
non bit-exact validation is subject to the minimum performance
requirements for the Enhanced Full Rate codec contained in
IS-686.

In the case of discrepancy between the high level and the
bit-exact descriptions, the description in the bit-exact C program
will prevail.

Additional information