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Mobile firm Orange has become the first UK network to use a technology that
offers higher quality voice calls.
High Definition (HD) voice claims to reduce background noise and the "hisses
and crackles" often heard on a normal mobile call.
The technology, known as, Adaptive Multi Rate Wideband (AMR-WB) has been
adopted as an international standard for 3G mobile networks.
Other networks are expected to follow Orange soon, experts said.
"It is relatively easy for an operator to introduce - it's just a software
upgrade in a base station," said William Webb, head of research and
development at the UK regulator Ofcom.
Other countries already have networks using the technology - known colloquially
as HD Voice - including Moldova and Germany.
Data squeeze
AMR-WB is what is known as a speech codec; software that compresses a voice
signal to maximise the amount of bandwidth on a network.
"There is a commercial incentive to squash the data as much as possible," said
Mr Webb. "But you can go too far. The trick is to find the balance point, the
sweet spot."
Continue reading the main story
Start Quote
The difference is noticeable, although I'm not sure you could quite describe
the HD call as 'crystal clear'
End Quote Rory Cellan-Jones BBC's technology correspondent
He said there had been a lot of experimentation over the years with voice
codecs, including the introduction of a so-called "half-rate codec", which
squeezed the same data into half the bandwidth.
"Operators tried to use it but quickly discovered that consumers didn't like it
and switched back," he said.
Speech codecs work by modelling the waveform of the incoming voice.
Rather than transmitting the whole waveform, algorithms look for consecutive
sections that are similar. If two sections of the wavelength are alike, the
redundant information is stripped out, allowing the signal to be compressed.
The AMR-WB codec also does this but to a wider range of speech frequencies that
today's codecs, allowing higher quality calls.
"We are using exactly the same bandwidth on the network," said Andrew Warner,
head of voice and messaging protocols at Orange.
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"We are squeezing more speech information into the same channel."
This is important as any additional need for bandwidth would reduce the
network's ability to cope with the ever increasing data demands of people
browsing the web on their phones.
In addition to compression technology, AMR-WB is "intelligent" and varies the
amount of data it pumps into the network depending on the complexity of the
speech pattern.
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"If the speech is quite complex it may use a higher data rate, if it is more
simple it drops down," said Mr Webb.
Orange has already run trials of the technology in the south west of England
and now plans to roll it out across the country.
Mr Warner said that many manufacturers were already developing handsets to work
with HD voice, including Nokia and Samsung.
The technology will only initially work on the Orange 3G network between
HD-enabled handsets.
"You won't experience it when you're calling a landline or a mobile phone that
has not been optimised to work with HD voice," said Mr Warner.
Orange, owned by France Telecom, recently merged with T-mobile in the UK. The
company - known as Everything Everywhere - has 30 million customers.
The two firms have not merged their networks so T-Mobile customers will not
initially be able to use the service.
The launch of HD voice comes amidst reports from Orange customers of regular
network outages.
Some have speculated that the faults are the result of upgrades to the network
or attempts to merge with T-Mobile.