LTE: losing its voice?

John C. Tanner
Telecom Asia

One of the latest signs that LTE is moving into the 'reality' stage of the hype curve is that equipment contracts are starting to pile up. As we went to press, LTE contracts had been awarded in Japan, Norway, Singapore, Spain, Sweden and the US, with Alcatel-Lucent and Ericsson the early winners, while in recent weeks, Chinese vendors Huawei Technologies and ZTE have been picking up momentum with LTE trial wins with Netcom of Norway and Telef"”nica in Spain, respectively.

Another sign that the hype bubble may be cresting is that some mobile players are already worried about how well LTE will play with legacy services - namely, mobile's two most reliably consistent cash cows: voice and SMS.

While most of the presentations, white papers and seminars on LTE in the past year have talked up the technology's multi-megabit data capabilities and the possible business cases that could be built on that, far less attention has been paid to LTE's ability to handle voice calls, apart from the fact that - unlike its 2G and 3G predecessors - it's not an old-school circuit-switched network retrofitted for packet traffic, but the other way around.

The assumption has always been that LTE would be rolled out as an overlay to existing 2G/3G systems, which meant that LTE could get in with the business of moving packets and leave the circuit-switched voice traffic to the old networks that are not only optimized for it anyway, but also aren't going anywhere. The other assumption was that the 3GPP's IP Multimedia Subsystem (IMS) platform would enable cellcos that wanted voice and SMS services on their LTE networks to duplicate them on the new platform.

However, T-Mobile International is not convinced that LTE will ship 100% voice-ready when it becomes commercially available later this year. It's banking on LTE supporting voice and SMS partially because it wants to launch with a full-service LTE portfolio and also because of the efficiency gains of running voice and data on the same network, which reduces the cost-per-bit (a key LTE selling point).

As such, T-Mobile has been rallying the LTE vendor space to revisit the voice issue to make sure it is ready. At February's Mobile World Congress, Emin GŸrdenli, T-Mobile International's SVP of radio networks (and technology director for T-Mobile UK), said his company wants voice capability in LTE 'ideally from dayone'.

A month later, T-Mobile spearheaded the formation of the VoLGA (Voice over LTE via Generic Access) Forum, with Alcatel-Lucent, Ericsson, Huawei, Kineto Wireless, LG, Motorola, Nortel Networks, Samsung, Starent and ZTE onboard to define specs for circuit switched voice and SMS over LTE using the 3GPP's Generic Access Network (GAN) standard. The forum already has published its stage 1 specs and stage 2 draft specs, which it has also submitted to the 3GPP.

However, as is always the case with fledgling technology standards, not everyone is convinced that LTE's voice-SMS capability is an urgent issue - and most of the skeptics are cellcos that are more sold on LTE's data-only proposition.

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