ITU-T’s Study Group 16 has completed work on G.711.1 – the new scalable wideband extension of the voice codec used in the majority of fixed-line digital systems - ITU-T Recommendation G.711. G.711.1 will significantly improve voice quality in VoIP calls by offering wideband quality while keeping bitstream interoperability with the G.711 narrowband legacy codec. Wideband offers far greater audio quality by making voice sound more natural and by greatly improving both intelligibility and listening comfort. Wideband also allows service providers to offer a wider variety of services. Widely deployed this bitstream-interoperable wideband extension of narrowband codecs will allow smooth transition from narrowband (300-3400 Hz) PSTN quality telephony to high-quality wideband (50-7000Hz) telephony over IP networks as well as efficient deployment in existing infrastructures.
G.711.1 can operate either at 80 or 96 kbit/s in wideband, and at 64 or 80 kbit/s in narrowband. Furthermore, the 64 kbit/s core layer mode enables seamless interoperability with systems equipped only with G.711. Besides this backward compatibility, another key attribute is its embedded coding feature that allows dropping part of the bitstream/payload on-the-fly during a call by simple truncation of the embedded bitstream at any entity in the middle of the network such as a gateway or a signal mixer at multi-point control unit (MCU). This avoids network congestion and facilitates interoperability with G.711 legacy narrowband systems. Besides these two main advantages, G.711.1 has a very short delay and low complexity, it also supports partial mixing that drastically reduces MCU complexity and delay.
G.711's roots can be traced back as far as the 1970s, it has become truly the lingua franca of voice telephony. The new ITU-T Recommendation enriches the existing standard while ensuring backwards compatibility and interoperability.
The new standard will drive the market for wideband applications. Launched in 2006, wideband telephony over fixed-line broadband access is gaining momentum; wideband telephony over mobile will soon start following the 2008 Mobile World Congress announcement of wideband-enabled 3G phones shipping in the 3rd quarter of 2008. Wideband services are expected to be one of the driving factors in next generation networks (NGN).