Smart devices are the rage but voice continues to account for a major part of customers’ bills. How can operators make a splash with a refreshed voice offering?
Solving basic voice challenges in a mobile environment
Adaptive Multirate (AMR) is a software that compresses a voice signal to minimize the consumption of bandwidth on the network: when channel conditions are adequate, less bits are needed to compensate channel errors, and more of the bit rate can be used to encode speech with higher quality. AMR has been used to encode speech in the frequency range of 200-3400 Hz. We can typically hear in the range of 20 Hz to 20000 Hz, but 200-3400 Hz (called Narrow Band) covers basic voice quality well.
Two challenges beyond mobility and being understood
When mobility was the biggest draw, being understood while on the move was sufficient. Thus Narrow Band AMR – coding speech in the range of 200-3400 Hz considering the channel conditions – was the solution. Moreover, handsets did not have enough processing power and battery to perform more intensive calculations.
Today we live in an era of mobile broadband with decreasing revenue per voice call minute, and end users expect more. One way to fight against end user price erosion is to change the rules of the game by HD Voice.
Wide Band AMR encodes speech at double bandwidth, from 50 Hz to 7000 Hz, and uses additional techniques to optimize background noise and silent periods. Spectrum is still scarce and radio links are still error prone, but Wide Band AMR doubles the speech quality while keeping the same bit rate as Narrow Band AMR. It is called High Definition voice – HD Voice for good reason.
What is needed to roll out AMR-Wide Band
Modern GSM and 3G WCDMA network hardware support WB-AMR natively, while older 3G media gateways and GSM transcoders need software updates. With all-IP radio access, some limitations due to TDM backhaul are naturally disappearing. Radio re-planning is not required but HD Voice needs good coverage. Operators can ensure a stable user experience by introducing HD Voice on both their 3G WCDMA and GSM networks. Good voice quality also requires better audio technology in handsets - possibly dual-microphone audio processing and improved speaker acoustics in handsets. The gauntlet is thrown towards phone manufacturers. Nokia 5230, Nokia X6, Nokia E5 and Samsung Omnia Pro were the first to market. For GSM HD Voice trials, Nokia recommended models are Nokia N8, E72, E55 and E52.
A windfall gain in user experience
HD Voice with AMR-WB comes naturally on top of GSM modernization driven by efficiency. The first operators to launch HD Voice will be the talk of the town while the followers would have missed a quick and sure opportunity to engage customers with their brand.
It is no surprise then that an increasing number of operators have launched HD Voice services or have announced their plans:
Nokia Siemens Networks has 179 GSM AMR-NB references, 21 GSM AMR-WB references and 325 GSM network references.
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