scope:

This document specifies the test procedures to ensure that non-bit-exact implementations of TIA/EIA-136-430 compatible full-rate speech codecs operating in CTX or DTX-high meet recommended minimum performance requirements. This document also defines the minimum performance specification for non-bit-exact TIA/EIA-136-430 CNG implementation operating under channel error free conditions. The speech codec is used to digitally encode the speech signal for transmission at a data rate of 12200 bps or 244 bits every 20 ms.

The TIA/EIA-136-430 standard includes a bit-exact specification of the speech codec using a fixed point ANSI C code [Ref. 14,15]. Twenty-eight sets of test sequences are provided along with this standard [Ref. 17]. These test sequences are designed to provide for maximum coverage of the fixed point ANSI C code. There are separate test sequences for testing the encoder and for testing the decoder portions of the TIA/EIA-136-430 standard speech codec. A bit-exact implementation of this standard on a fixed point device would have to "pass" all of the twenty-eight test sequences for the encoder and the twenty-eight test sequences for the decoder in order to comply with the TIA/EIA-136-430 standard.

At the Base Station end, non-bit-exact implementations of the TIA/EIA-136-430 standard are permitted. For such implementations, it may not be possible to generate test vectors that can guarantee compatibility with the standard by using them as input to the speech encoder or decoder and by examining their output for exact replication of the corresponding reference vector. This document describes a series of tests which are used to test conformance to the specification. These tests do not necessarily ensure that the codec operates satisfactorily under all possible input signals and it is still a requirement of the manufacturer to ensure that his implementation operates in a consistent manner. The purpose of these tests is to test for minimum performance levels. The manufacturer should attempt to provide the highest performance possible.

The testing of any non-bit-exact implementation of the codec operating in CTX or DTX-high is based upon two classes of procedures:

Objective tests, which are based upon bench measurements of the speech codec function.

Subjective tests, which are based upon listening tests to judge overall speech quality.

Minimum performance specification for CNG is based on objective tests. These tests are defined by the test database, a method for generating individual test data files, the test requirements on candidate CNGs, a method to collect performance metrics, and the means to test those metrics so as to validate conformance to the specification.

The main purpose of the testing is to ensure adequate performance between any Base Station's encoder and any Mobile Station's decoder and vice-versa. Since the Mobile Station is restricted to have bit-exact implementations of the TIA/EIA-136-430 standard only, it suffices to demonstrate that minimum performance standards have been met when inter-operating with any bit-exact implementation. For this purpose, the fixed point ANSI C code provided as a part of the TIA/EIA-136-430 standard can be treated as the reference or master codec [Ref. 14,15].

The restriction that MSs can only have bit-exact implementations of the TIA/EIA-136-430 standard is the primary reason that allows this standard to ensure minimum performance standards between any pairing of Base Stations and MSs; otherwise, this could only be guarantee d by testing all combinations of encoder/decoder pairings in both Base Stations and MSs. With the number of equipment manufacturers expected to supply equipment this could easily become a prohibitive task.

By convention in this document, the Courier font is used to indicate C language and other software constructs such as file and variable names. The diacritical mark, §, is used to indicate section numbers.