AMR-WB (=Advanced Multi-Rate Wide Band) is a wideband (50-7000 Hz) speech coding algorithm, to be compared with the common narrow band speech codecs (300-3400 Hz). AMR-WB is also standardised as G722.2 by the ITU-T.
AMR-WB is used by the service called “HD Voice” by mobile operators.
HD Voice is not a VoIP service, although this is suggested by some features. This is a circuit switched mode, as is the basis for the mobile telephony service often called “GSM”. For deployment reasons, most operators implement this new service on their 3G/3G+ base stations, and less often on the 2G (GSM) ones. As the sales communication emphasises the Internet and data features for the 3G/3G+ networks, users may forget that these networks also support the circuit mode telephony service, just like the 2G networks.
Transmission of HD Voice uses same channels and benefits same conditions and quality or service as “standard” mobile voice. The priority granted to voice conversations (over packet mode data) in high traffic situations is still valid, and the network resources allocated to a link stay committed until it is released, even if other users are stressing the network.
The bits rates used are roughly similar to those used with GSM, the bandwidth extension is due more to the codec performance and efficiency than a higher bit rate.
As the primary goal is telephony, the system and coding are designed for a moderate latency, close to that of normal mobile telephone communications, if not better.
