scope:

This Recommendation applies to the characteristics, performance and testing of voice enhancement devices (VEDs) for use in digital network-based equipment. Such devices are commonly found in mobile networks, and this version of the Recommendation is only applicable for mobile networks.

VEDs are defined as certain signal processing network functions (SPNFs) (such as noise reduction and acoustic echo control) in the digital transmission path that perform voice enhancement functions on voiceband signals that traverse mobile networks. Possible locations for VEDs located in mobile networks are shown in Appendix I.

Voice enhancement functions covered by this Recommendation include the control of acoustic echo generated by wireless handsets, noise reduction, and the recognition and accommodation of tandem free operation (TFO) and interworking function (IWF) signals.

The purpose of this Recommendation is to define certain performance constraints for VEDs and, where appropriate, to define laboratory tests that may be performed on a VED to verify that these constraints are met.

A VED that satisfies all the constraints and passes all of the tests in this Recommendation should ensure (but will not guarantee) that the pre-existing standard of the overall network performance (e.g., the transmission of speech, voiceband data and other voiceband signals, ISDN, etc.) is not degraded when the VED is installed in the network.

This Recommendation also describes the general characteristics of VEDs and indicates what characteristics are important to provide acceptable performance in the network. Issues relating to the interaction of VEDs with other network and subscriber equipment are also discussed in this Recommendation. This Recommendation does not define a standard algorithm for voice enhancement functions. Nor does it apply to either electrical echo control (governed by [ITU-T G.168]) or automatic level control (governed by [b-ITU-T G.169]).

Note that VEDs may be incorporated into other network equipment, such as the transcoder or electrical echo canceller. In this case, the performance requirements of this Recommendation refer to the performance of the VED only.

Note that some terminal devices (e.g., mobile stations) incorporate voice enhancement functions (acoustic echo control, noise reduction, etc.) that are similar to those performed by the VED. This Recommendation does not apply to functions contained in these terminal devices.