Generated by Jive SBS on 2010-05-25-06:001

Service Provider Mobility: EnterpriseFemtocells: Easy to Underestimate

Posted by Will Franks Jun 17, 2009

Enterprise femtocells, forming a grid of self-organising coverage, are genuinely new. So it'snot surprising that they are often misunderstood.

On one hand they offer the low cost and self-install simplicity of enterprise WiFi. Yetthey also offer all the benefits of 3G cellular with massive data capacity. This is a headycombination, and promises to make in-building cellular affordable for small companiesbecause the femtocells are based on mass-produced hardware, because no radio planningis required and because they can be self installed by the IT guys. They also promise tomultiply the uptake of in-building cellular in large enterprises by providing added flexibilityand simplicity at a fraction of the cost of today's manually engineered pico/DAS systems.

John Spindler, in his article for Wireless Week, makes a couple of familiar assumptionsabout enterprise femtocells, which I'm happy to put right.

ASSUMPTION 1: MINIMUM COVERAGE OVERLAP

The first assumption is that a grid of enterprise femtocells has minimal coverage overlaps.It doesn't. In fact the femtos deliberately organise themselves into a grid with extensiveoverlaps.

Interference

What femtocells do that's different to picocells is manage interference themselves in real-time rather than rely on the complex RF engineering that would otherwise be required. Thefemtocells obey the policies set by the mobile operators so will never produce unmanagedinterference between each other or with the macro network. For example, femtocells in thegrid use algorithms to ensure maximum spatial diversity between scrambling codes.

Service Provider Mobility: Enterprise Femtocells: Easy to Underestimate

Generated by Jive SBS on 2010-05-25-06:002

Signal dominance

Making the wrong assumption about coverage overlap leads to worrying about phones flip-flopping in and out of the macro network. But enterprise femtocells provide a strong indoorsignal and also hold onto phones using "sticky cell" technology. Together these ensure thatflip-flopping doesn't happen, and that's true of any 3G phone.

ASSUMPTION 2: UNDERESTIMATING FEMTOCELL CAPABILITY

The second assumption is that femtocells can support only a handful of calls and have arange which is a fraction of a picocell. Not quite: enterprise femtocells can range in capacityfrom 8-16+ users, and each one has a range approaching today's picocells.

Handovers

Femtocells in the grid don't need to do soft handovers because of strong cell overlap, andthey don't have to handover very often because their range is not far short of picocells.There is always a battery life penalty when handing-over, but this is more than offset by themassive reduction in handset transmit power. In any case additional battery consumptiononly occurs when on a call, not when the phone is moving but idle. So the net effect is amajor boost in battery life over the macro network.

Over-provisioning?

In a grid of enterprise femtocells every femto handles not a handful of users but 8 or16 or more - providing robust coverage and high capacity throughout the building. Mostimportantly, it does so more cost-effectively than Pico/DAS solutions that require radioengineers to deploy them.

The bottom line...Ever wondered why wifi access points tend to be installed in a modular fashion,rather than in a pico/DAS-style hierarchy? The answer is because they can be - it'ssimpler, easier and cheaper. And the same is true of enterprise femtocells.

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Jun 17, 2009 12:48 PM Kittur Nagesh

Service Provider Mobility: Enterprise Femtocells: Easy to Underestimate

Generated by Jive SBS on 2010-05-25-06:003

Thanks Will for triggering the discussion on Femtocells. We believe that Femto is critical toscaling the mobile internet, especially as it transforms to higher performance via HSPA+,LTE, etc.

Can you comment on the impact of Femtocells on overall Mobile SP frequency planning? Ithought we had not yet reached "plug-and-play" Femto deployments.

And of course, there is the business model aspects of Femto. Who really pays for it?

What have you seen on these fronts? Thanks again!

Nagesh

Jun 23, 2009 9:09 AM ajay_sahai Kittur Nagesh in response to

According to Lightreading - Vodafone will launch femto in UK from July 1. Exciting. Butseems to be a very voice coverage centric offering. Not sure why they are underselling thebenefits of femto to indoor coverage for mobile data service. Quite similar to Sprint. In thatcase it was a 2.5G femto so it is clear.

Not sure what is the reason for VF to do this in a market like UK. Is it because of somelimitations in their femto/concerns about the femto technology or is it because they don'twant to get into backhaul traffic debates with the ISP's....

Jun 24, 2009 11:13 AM Will Franks Kittur Nagesh in response to

Yes we are at "plug-and-play". I think well demonstrated by Vodafone announcing theirlaunch. On frequency planning femtocells work on the bases of managed interference. Being aware and able to adapt to their radio environment is what fundamentally makes themdifferent from picocells.

Most deployments will be sharing frequencies with the macro network, usually the second orthird carrier.

Service Provider Mobility: Enterprise Femtocells: Easy to Underestimate

Generated by Jive SBS on 2010-05-25-06:004

On business model it depends on what the "Offer" is for the Carrier i.e. Coverage, Churnreduction, home tariff, enterprise, etc. As an example on churn, subscriber acquisition costsaround $400 in Europe. Churn is around 35% per year. So you can see for every customera Carrier can stop from churning they have up to $400 to spend per year.