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Optical/IP

NSN Goes Solo for LTE Voice

Nokia Networks claims to have a unique way for filling the Long Term Evolution (LTE) voice void, and has not joined an industry initiative to create a new standard for delivering voice services over LTE.

NSN stands out as the only major infrastructure supplier that is not a member of the Voice over LTE via Generic Access (VoLGA) Forum , which is a new group set up to write specifications for delivering circuit-switched voice and SMS services over IP-based LTE networks using the Generic Access Network (GAN) standard. (See New Specs Deepen LTE Voice Dilemma and New Forum Gives Voice to LTE .)

The VoLGA initiative is supported by T-Mobile International AG and nearly all of NSN's competitors, including Alcatel-Lucent (NYSE: ALU), Ericsson AB (Nasdaq: ERIC), Huawei Technologies Co. Ltd. , Motorola Inc. (NYSE: MOT), Nortel Networks Ltd. , Sonus Networks Inc. (Nasdaq: SONS), Starent Networks Corp. (Nasdaq: STAR), and ZTE Corp. (Shenzhen: 000063; Hong Kong: 0763).

NSN, instead, proposes a different approach for delivering LTE voice services, which it calls Fast Track Voice over LTE. The vendor says its mobile switching center (MSC) servers already have session initiation protocol (SIP) signaling capability, and with the Fast Track software update, those MSC servers can handle VoIP traffic in LTE networks.

"We have a solution that's much more straightforward," says Sandro Tavares, marketing manager for converged core at NSN, explaining the vendor's decision not to join VoLGA. "It gets to the objective of providing voice over LTE networks with the same equipment that our customers already have, and [it's] tied to 3GPP standards."

How to deliver legacy circuit-switched voice and SMS services over LTE networks is a divisive issue for the industry. The threat of fragmentation is real, and several operators are worried about it. Even though LTE networks are expected to enable only data services during the first few years, some operators are uncomfortable with not having a good solution for delivering their cash-cow services. (See T-Mobile: Voice Discord Threatens LTE and T-Mobile, Orange Open Up on LTE.)

Quick recap: The 3rd Generation Partnership Project (3GPP) -endorsed way to deliver voice over LTE is via IP Multimedia Subsystem (IMS), but the technology is perceived as too expensive and immature to deploy anytime soon. Another approach is called circuit-switch (CS) fallback, whereby voice and SMS traffic would be handled by 2G or 3G networks, which is inelegant and would require multimode devices. (See Voice Over LTE & the 'IMS Gap'.)

A third way is the VoLGA plan, which would effectively tunnel the circuit-switched traffic across the LTE IP-based network. The problem for VoLGA is that T-Mobile is so far the only operator supporter. Without other major operators behind it, the initiative will struggle to gain 3GPP acceptance.

And then there's Nokia-Siemens Networks.

NSN's Fast Track solution for LTE voice is based on the mobile softswitch developments undertaken by parent Nokia Corp. (NYSE: NOK) during the past few years. Back in 2004, before its joint venture with Siemens, Nokia introduced an MSC server mobile softswitch based on its DX200i hardware. In 2006, a software upgrade to that product was commercially available so that the MSC server could support VoIP, which then became the Nokia VoIP Server. (See Nokia Intros VOIP Server.)

The Fast Track update to the Nokia VoIP Server makes it possible for mobile operators to use their existing circuit-switch core networks to manage voice traffic over LTE networks. The servers can also be used if operators choose to deploy an IMS architecture.

"Fast Track Voice over LTE… handles voice using SIP by a software update or by activating VoIP functionality in MSC servers," explains Aarne Rainvuori, head of voice solution sales, mobile core, at Nokia Siemens.

NSN says that 240 of its customers can use Fast Track to deliver voice services over LTE networks.

And since many mid- to high-end handsets already support SIP, the need for device updates is reduced. By contrast, the VoLGA solution will require clients on handsets in order to work.

When asked whether NSN would ever join VoLGA if it got enough operator support, Tavares says it's "hard to say. We really believe our solution makes sense for our customers ... [We] would rather not talk about 'ifs' here. Our fellow competitors have decided to propose this solution, but it would be up to the market to decide."

For more on this issue, tune in to the Unstrung Webinar, Voice Over LTE, on Tuesday, July 28.

— Michelle Donegan, European Editor, Unstrung

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