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Is voice over LTE a conundrum?
|07 июля 2009|
I find it odd that the first deployments of Long Term Evolution (LTE) are coming this year despite warnings that the current generation of technology cannot support circuit-switched-based SMS and voice services.
It may sound odd in itself that I'm talking about circuit-switched services being supported on these all-IP networks. After all, LTE is supposed to be a data-only solution in the interim, supporting data cards and dongles. Third-generation systems are supposed to be used for voice.
But Kineto Wireless points out in its new blog that a lack of native SMS over LTE is set to doom even LTE dongle services because operators rely on SMS for back office, customer care, provisioning and management of HSPA-based dongle services. The same systems need to be available for LTE dongle and data card services at launch.
And T-Mobile International has been making the rounds to argue why LTE needs to support voice services from the get go. The operator said that since LTE is supposed to give operators the most spectrally efficient networks, it only makes sense to put all traffic on that network and not rely on less efficient 3G networks. Such support also will entice manufacturers to make LTE phones that will be more appealing to consumers than dongles and data cards.
The 3G Partnership Project (3GPP) hasn't ignored the issue, but the standards body has envisioned that this functionality would be solved by the use of IP Multimedia Subsystem (IMS) architecture. The problem is, we've been writing for some time about the sluggish rollout of IMS.
Others have talked about enabling a circuit-switched fallback capability whereby the mobile device is forced off the LTE network onto 2G and 3G networks for voice and SMS capabilities. This also doesn't seem too promising given the network inefficiency.
T-Mobile International and major handset and equipment vendors have joined forces to promote what they call Voice over LTE via Generic Access (VoLGA). By September, the group hopes to develop a common set of standards, to be submitted to 3GPP, to allow circuit-switched SMS and voice traffic to travel over LTE over a generic access approach. Kineto and some of the wireless industry's biggest vendors are founding members of the group, including Alcatel-Lucent, Ericsson, Huawei, LG Electronics, Motorola, Samsung, Starent and ZTE. Nokia Siemens Network is proposing its own solution.
Steve Shaw, vice president of corporate marketing with Kineto, says VoLGA (I keep thinking of Russia) is garnering support from operators despite the fact that T-Mobile International is the only one to join so far. He said other operators aren't that interested in joining since the group is poised to release technical specs.
Although IMS is the plan for many operators, Shaw said there is no reason that operators can't use VoLGA now and then migrate SMS and voice functionality to IMS down the road. Can a consensus be reached within 3GPP quickly? Some see the VoLGA effort as trying to derail IMS. Moreover, will some networks support VoLGA and others support IMS longer term? What does this mean in terms of cost? And of course, the biggest question is: Could early LTE deployments be delayed because of this issue as industry folks are suggesting?