T-Mobile, Orange Open Up on LTE

BERLIN -- LTE World Summit -- For T-Mobile International AG and France Telecom's Salt SA , the key emphasis in Long Term Evolution (LTE) is on the "Long."

Here in Berlin, the operators raised all the technical issues that need to be resolved before the next-generation mobile broadband technology can be commercially viable.

While neither operator committed to a launch timeframe, their plans for LTE lag behind the ambitious timetables set by Verizon Wireless and NTT DoCoMo Inc. (NYSE: DCM), both of which are aiming to launch commercial LTE services in 2010. (See MWC 2009: T-Mobile Gets Real on LTE.)

The operators' concerns with LTE include: support for voice services; the impact on backhaul capacity; intellectual property rights; the lack of standardization for self-organizing networks (SONs); and the lack of spectrum. And those are just the chief conerns.

In addition, T-Mobile and Orange, along with other European carriers, are scarred by the disastrous early days of WCDMA (3G), when they spent billions of euros on licenses and hyped 3G downlink speeds beyond reality, leaving customers and investors sorely disappointed. They don't want to repeat those 3G mistakes in LTE, especially in the midst of a global financial crisis.

LTE needs voice
As an all-IP, packet-based network, LTE doesn't support legacy circuit-switched voice and SMS services. Determining the best way to deliver those services over LTE is causing some angst among operators.

"I don’t think we should push LTE as a wireless DSL technology -- it has much more than that. That's why we push heavily for early availability of all services, most importantly voice and SMS over LTE," said Klaus-Juergen Krath, senior VP of radio networks development at T-Mobile. "We should take our lessons learned [from 3G] to LTE and we shouldn't launch unless full services are ready" (that is, voice and SMS).

There are many different solutions for delivering voice over LTE, including IP Multimedia Subsystem (IMS), Voice over LTE via Generic Access (VoLGA), and using GSM, UMTS, or CDMA2000 1x networks for voice while LTE is used only for data, a hybrid strategy referred to as circuit-switch fallback. (See New Forum Gives Voice to LTE .)

T-Mobile supports VoLGA, while Orange prefers the circuit-switch fallback approach.

"The first LTE applications will be data only," said Marc Fossier, executive VP of corporate and social responsibility and former Group CTO of Orange (NYSE: FTE). "2G/3G fallback is not a very nice solution, but it could be usable."

3 Group 's technology director, Ed Candy, also weighed in on the voice issue.

"In these difficult times, to go ahead with a technology that's service-limited is crazy," he said. "We don't know how this financial crisis is going to play out. I would be against [using] any technology that has fundamental holes in it."

Backhaul capacity crunch
The backhaul capacity constraints currently being experienced by operators in their 3G networks will be magnified in LTE deployments.

"The bottleneck today is not the radio, but backhaul. That's what determines the end-to-end performance," said T-Mobile's Krath. "This is something we've been working on, to eliminate this bottleneck and to increase bandwidth on our backhaul while keeping costs flat."

With HSPA, for example, a peak rate of a cell site can be 45 Mbit/s (that is, 3x14.4 Mbit/s). "But still, the majority of sites are connected through E1 [lines] with 2 Mbit/s to 8 Mbit/s capacity," he explained. "We need to get fiber to the sites or build high-capacity microwave links in the future."

The challenge for operators is to increase this network capacity for little or no incremental cost. "We must keep our backhaul costs flat, but must increase our backhaul capacity significantly," said Krath.

Orange's Fossier said that "full IP microwave solutions are absolutely key" to LTE.

It's clear LTE will require bigger backhaul pipes, but just how much more is difficult to specify. And, according to Heavy Reading senior analyst Patrick Donegan, LTE backhaul is more than a capacity issue.

"From a technology perspective, throwing more capacity at the problem is arguably the easier part of the backhaul challenge with the transition to LTE," says Donegan. "The more difficult part is designing the network to support the new latency and security requirements that come with the new LTE architecture, such as with the introduction of the X2 interface between the eNode Bs [LTE base stations]."

And another thing…
In addition to backhaul and voice services, Orange also worries about LTE IPR (international property rights). "We'll not stop talking about it," said Fossier. "The 3G story has been hindered by IPR. If we keep on piling up IPR, we'll not help the industry."

And the operator called for more work to be done to develop and standardize SON techniques, which it eyes as a potential operating cost saver.

"We're not concerned with peak rates," said Fossier. "The key issue is on cell capacity and cell edge performance. This has to be checked, and that's the main advantage with LTE we're looking at."

While Orange and T-Mobile's plans for LTE are nowhere near as aggressive as those of Verizon Wireless, the main advantage the U.S. operators have over the Europeans at this stage is spectrum -- they've got it with 700 MHz. Most European operators, except for those in Sweden and Norway, are still waiting for auctions of 2.6 GHz spectrum and 800 MHz, the so-called "digital dividend" spectrum. (See MWC 2009: AT&T Plots LTE in 2011 and MWC 2009: Verizon Picks LTE Vendors.)

Even though European operators may have the option to use refarmed 900 MHz or 1800 MHz spectrum for LTE, Orange and T-Mobile are eyeing new spectrum for their next-gen mobile broadband services.

"There are no clear plans to use 900 MHz for LTE. The 900 MHz band is something we need to complete and complement our UMTS deployment," said Fossier. "So far our plans are focused on 2.6 GHz for LTE. Our view is that LTE is for new spectrum."

T-Mobile's Krath said 2.6 GHz and the digital dividend appeared best for getting services to market.

He concluded: "There is still much about LTE in announcements and PowerPoints. We still have work to do on industrialization of LTE, backhaul, automation/SON, [and] legacy network support."

— Michelle Donegan, European Editor, Unstrung

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