Do energy conservation measures make a case for femtocells?

Green HousesThe need to make more efficient use of our energy resources has changed the construction materials used to build our homes. These can drastically reduce the quality of indoor mobile phone signals. Does this make a stronger case for femtocells in the home and office?

Energy conservation is no longer optional

With governments having signed up for aggressive carbon reduction targets, it makes a lot of sense to improve the energy efficiency and thermal performance of buildings rather than rely on sustainable energy production. Wind turbine industry has been in recession of late, with substantial layoffs. Solar panels, attracting heavy subsidies, still make up a very small percentage of generating capacity.

The contribution made by improved energy efficiency enforced through building regulations should have a much greater effect on the net energy demands, and therefore the carbon footprint of the future. The legal requirements apply both to newbuild and existing properties, whenever new walls or extensions are built.

Telecom companies themselves have set their own energy reduction targets. Its not all completely altruistic – ongoing energy bills form a substantial part of network operating costs. Large operators such as France Telecom, KPN and ATT have all given themselves goals of some 20% reduction by 2020. Fixed network operator BT plans to reduce their carbon footprint by 80% between 1996 and 2016. 

Materials used aren’t mobile phone signal friendly

Unfortunately, the very materials that are used to improve thermal efficiency aren’t so beneficial for radio signals. Metallic foil is often encased inside walls. Glass window panes are made from materials that are more energy efficient. These may still pass through visible light but be less friendly to weak mobile phone signals from a distant cell tower.

This isn’t new – those living in metal framed or stone walled homes will know. This eHow article summarises the main issues. 

Network planners are noticing a difference

At the small cells conference in Berlin in October 2011, one speaker commented that it is becoming more difficult to provide good mobile phone service in such buildings. High thermal insulating glass windows and metallic foil wall insulation are presenting barriers that previously weren’t found.

Where a typical glass window might cause less than 1dB signal loss, measurements of up to 100dB signal loss have been made – making it extremely difficult to achieve good service in those buildings. Even where service is provided, the high signal power required affects both the outdoor macrocell (by taking up a greater percentage of its capacity) and the user (shorter battery life).

A simple solution

The provision of small, low cost and highly effective femtocells inside these buildings solves both these issues. Alternatives, such as local repeaters are typically more difficult to install and maintain. The low cost of femtocells (retail price now as low at 49 Euros, but sometimes given away free) also makes this attractive to end users. 

Without such measures, the capacity of the outdoor cell towers will be significantly reduced, leading either to the need for many more to be installed or substantial loss of network capacity in the area served.

More energy efficient too

It can also be argued that the power consumption of femtocells (the latest models operate at a maximum of less than 5 Watts) is a fraction of that used by large cell towers. The battery life of smartphones using them is also extended, due to the low transmission power needed to connect.

While a combined indoor solar powered femtocell may not make sense (the sunlight indoors typically  wouldn’t be adequate), there may be many already powered indirectly by solar panels on the roofs of homes and businesses, again with a reduced carbon footprint.

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