T-Mobile UK has claimed that voice-over-IP (VoIP) calls are too low in quality to be allowed over its data network.
As first reported by ZDNet UK earlier this week, the mobile provider has banned the use of VoIP and IM services over its new HSDPA-enabled data cards.
Initially it said the move was a "commercial decision" and such services were "not key" to its customers. But in a statement issued on Wednesday, T-Mobile said instead that VoIP technology "is not yet of a consistent or high enough level of quality to offer a good customer experience on the T-Mobile network".
"This situation may change in the future," it said, "but for now we believe it is in the best interests of our customers to restrict the use of VoIP technology."
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No other UK network prohibits the use of VoIP with datacards. Earlier this year the 3 network went so far as to sign a VoIP partnership with Internet telephony giant Skype.
3 spokesperson Rachel Channing told ZDNet UK that 3 makes a point of offering its customers "choice and a range of platforms for communications".
"We also have an advanced 3G network which means we can offer these services over a datacard or even a handset," she said on Thursday.
But telecoms analyst John Delaney of Ovum said T-Mobile’s decision was "not entirely illegitimate".
"Technical reasons make it difficult to offer consistent services," Delaney told ZDNet UK on Thursday, suggesting that VoIP’s bandwidth-hungry nature is one reason behind T-Mobile’s decision.
"The main reason operators are concerned about VoIP over their 3G networks is not so much a worry about substitution of calls and call revenues, but degrading the performance of the network for other users."
Margaret Hopkins, associate at Analysys, disagreed. "It’s not really real-time packets that hog bandwidth, it’s file transfer protocols such as TCP," Hopkins told ZDNet UK.
"I’m not saying you can be sure of perfect quality on a VoIP network, but it seems to me that’s not the main motivation for T-Mobile’s decision. This looks to me like they don’t want VoIP to affect their voice revenues." The ban was "excessively protective", Hopkins said.