Femtocells expand to cover urban areas

cityscapeWith femtocell technology now proven and generally accepted for use in the home and office, we are now seeing more serious investment in products for public access in urban areas. On show at this year’s Mobile World Congress, Alcatel-Lucent launched their specially designed metro-femto product targeted at this expanding market. I looked more deeply into what they have been up to.

Metro-Femto Isn’t New

This isn’t the first time we’ve seen the femtocell industry promote the idea of femtocells for coverage and capacity of high traffic in public areas – for example Vodafone has been using the term metro-femto for some years and disclosed that they have actively deployed the technology in Qatar and Dubai last year.

With the performance of the latest radio optimization techniques close to reaching the theoretical limits of Shannon’s Law, the only way to achieve substantial increase in data capacity is either through extra spectrum (very expensive or unobtainable) or large numbers of small cells. Metro-Femto offers a way of achieving this in popular urban areas using open-access femtocells both indoors and out.

But specifically engineered metro-femto products are

What is new is that the products on show today are not adapted residential devices, but have been custom engineered with a specification more suited to unsupervised and remote sites.

Alcatel-Lucent’s new metro product has been designed from the ground up for this application – I’d view this as a 2nd generation metro-femto unit. It’s not just the same residential or enterprise femtocell board in a different box – the unprotected environment means it needs to be much more ruggedized (temperature, outdoor weather, physical abuse etc.) and additional remote management capability. However the same underlying femto hardware and mature femto software are used, so that they connect into the same Femto Gateway and management systems as other classes of femtocell.

To provide the wider range and performance, higher RF power is used – these units are either 250mW or 500mW – much higher than the 20mW residential or even 100mW enterprise femtocells. They can handle up to 16 or 32 concurrent voice calls/channels which gives enough capacity for the small areas they cover.

The photo on the right shows the new unit on a live trial site.

ALU-Metro-Femto

Other options include internal/external casings, pole or wall-mount, 2100MHz or 1900MHz (with GPS to help comply with North American emergency call location requirements).

The units are powered remotely over Ethernet – typically a small mains power converter (similar to a laptop power adaptor) is used to inject power onto the Ethernet cable and a modem used to connect to the internet through DSL, cable or other connection. These can be installed nearby the outdoor unit or at a more convenient and accessible remote location.

Installation doesn’t require highly skilled RF installation engineers – anyone with suitable telecoms/IT wiring expertise should be capable. Some RF planner oversight will be needed, although detailed configuration parameters for macrocells (antenna tilt angles, RF power settings, spreading code assignments etc.) aren’t needed. Unlike residential femtocells, some configuration to ensure efficient handover (such as neighbour lists) may be appropriate.

Unlike some of the residential femtocells, where price point is extremely sensitive, these units aren’t manufactured by the high volume ODMs in the Far East. Alcatel-Lucent has engineered this entirely in-house, from the board design, case through to manufacturing.

Stronger Business Case

Regardless of how fit for purpose the new hardware is, the business case for it must stack up. For this, Bell Labs (Alcatel-Lucent's research arm) did some business modeling and compared the cost of providing capacity through traditional macrocells with small urban femtocells. Whether you believe their results are biased or not, I’ll leave to the reader to determine – but bear in mind that ALU develop and sell both types of product.

The macrocell approach increased the number of existing macro cellsites from 28 to 39 and substantially increased the capacity of each through extra RF carriers, sector splitting and backhaul. The cost was some €1.43Milllion over a 3 year period.

The metro-femto approach deployed 144 metro femtocells at total cost of €640K - a saving of some 55%.

Shared femtocell infrastructure

One argument being made by the femtocell vendors is of the low cost and short time for incremental deployment of other classes of femtocell. Where operators have already taken the initial step of installing gateways, management systems and business processes to support any class of femtocell, these can be reused for other classes.

This reduces the time and cost to introduce metro-femto significantly because it avoids the need for wider staff training and familiarisation, vendor selection of common femtocell infrastructure and related costs.

Summary

This might be one of the first specially designed metro-femto products, but I’m sure this won’t be the last. There is clearly growing interest from network operators seeking to find more cost effective means of satisfying the thirst for mobile broadband data capacity in urban areas.

Metro-Femto provides another strong commercial argument for deployment of femtocells. The incremental cost for network operators who have already deployed residential or enterprise systems means that those operators can react quickly to respond to their customers needs – stealing a march on their competitors.

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