Small cells

Backhaul Clouds Metro Femto Vision

Vodafone Group plc (NYSE: VOD)'s vision for deploying metro femtocells for future mobile broadband coverage is alive and well, but the concept needs a solution for low-cost, high-capacity backhaul to become reality.

Vodafone first introduced the metro femto concept -- which it calls a "MetroZone" -- last year. Since then, other major operators have backed the concept; femto specialist Picochip unveiled plans for an LTE chipset supporting this application; and Vodafone has been working with partners (but we don't know who) to develop, test, and promote the idea. (See Vodafone Dreams of Metro Femto, Operators Eye LTE Metro Femtos, picoChip Touts LTE Femto, and PicoChip Does LTE Femtos.)

The basic idea is to take the same low-cost, low-power principles of femtocells used in homes or offices and build those into rugged, outdoor, shoebox-sized base stations that can be installed on lampposts or street corners to supplement macrocell coverage in future networks like Long-Term Evolution (LTE) or LTE-Advanced. The premise is that smaller cells have better performance and higher capacity.

Following recent simulations and a technical trial in Europe, Vodafone's verdict is that the concept is good, but needs work, in nutshell. The operator says it will continue to pursue the idea and start work on a number of technology issues.

"The concept is strong," said Andy Dunkin, head of new technologies and innovation for radio access networks at Vodafone, speaking at the Next Generation Networks conference in Bath, U.K., yesterday. "As an architecture, it works for us."

Now the operator will turn its attention to several technology challenges that could potentially thwart the project, the biggest one of which is backhaul.

Many small LTE base stations deployed in hotspots will need high-capacity, low-cost backhaul connections. Vodafone's Dunkin says the operator is looking for a wireless backhaul solution to be developed and called for further industry support to resolve the problem.

"If we can't crack the backhaul, then it's not very feasible," Dunkin told Unstrung. "There's nothing we're not exploring."

He explained that backhaul links with capacity of 50 Mbit/s to 100 Mbit/s would be needed to support the small LTE base stations. Ideally, the compact base stations would house, not only the radio front end, but also the wireless backhaul, he explained.

One such option is called in-band backhaul, which lets an operator use some of its own spectrum for backhaul purposes. Israeli-based semiconductor startup DesignArt Networks has built this capability into its base station chipsets for LTE and WiMax. (See Startup Tackles 4G Backhaul Bottleneck and DesignArt Tackles Backhaul.)

Ultimately, Vodafone is evaluating the MetroZone concept as a way to ensure next-generation mobile broadband networks live up to users' expectations in the future.

"Nothing is too wacky to try and predict what traffic behavior will look like in 2015," he says. "[Consumers want] to access the Internet in the same way with same level of experience as they have from home. For mobile operators, that's a challenge."

— Michelle Donegan, European Editor, Unstrung

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