Femto Forum study concludes femtocells provide compelling benefits for 3G deployments in lower frequency bands

Femtocells help operators extend the benefits of lower frequencies by cost effectively plugging coverage gaps and augmenting capacity without introducing harmful interference

London, UK  – The Femto Forum, the independent industry and operator association that supports femtocell deployment worldwide, today published the results of its femtocell interference study focused on frequency bands below  1 GHz, such as the 850 and 900 MHz bands. The study found that femtocells can increase capacity by a hundred times, compared to the macro network alone, and this can be achieved without introducing unmanageable interference when proper mitigation techniques are used. Additionally femtocells allow operators to extend coverage to areas which cannot be covered economically or effectively with the outdoor network.

Lower frequency bands, such as 850 and 900 MHz, are proving increasingly popular with mobile operators for 3G usage as they provide more comprehensive coverage than higher frequencies and provide additional capacity where high frequency spectrum is scarce. However, there remain areas where operators cannot provide coverage as it is uneconomical or where the design of buildings prevents signal penetration.

Femtocells resolve this challenge by providing targeted indoor coverage while also adding major extra capacity. In so doing, femtocells maximise the benefits both operators and subscribers receive from lower frequency 3G services. The study assessed whether in the process of adding additional capacity, femtocells also operating on this lower frequency would introduce unmanageable interference. Such a situation would be necessary where operators do not have higher frequencies available. However, the research found that interference can be mitigated with a variety of power management techniques.

“Lower frequency bands offer powerful benefits for operators by facilitating more comprehensive mobile broadband coverage. However, they do not represent a silver bullet. The costs of macrocell solutions still make service provision in sparsely populated areas challenging and as data usage increases their benefits also decline,” said Simon Saunders, The Femto Forum’s Chairman. “Femtocells help operators make the most of lower frequencies by plugging coverage gaps and ensuring bandwidth hungry mobile users don’t negatively impact other subscribers’ experience. Crucially, it is now clear they can do this without introducing unacceptable interference.”

The study looked at femtocells using a separate carrier to the surrounding macro network and also those using the same carrier – which poses the greatest interference challenge, but also the greatest opportunity for increased spectrum efficiency. Although femtocells using a separate carrier were demonstrated to provide a simple means to essentially eliminate interference, many 3G operators do not have sufficient spectrum for this to be practical. In this situation the study found that techniques such as adaptive attenuation, power capping, downlink power management and increased receiver dynamic range can successfully mitigate interference. These techniques are already becoming widely available in the industry while others have already been built into standards.

The interference paper will be available alongside a shorter less technical topic brief paper, that summarises this study as well as the previous 2 GHz study, on the Femto Forum web site on February 15th. The previous 2 GHz study can be found here.

About The Femto Forum
Femtocells are low-power wireless access points that operate in licensed spectrum to connect standard mobile devices to a mobile operator’s network using residential DSL or cable broadband connections. The Femto Forum (www.femtoforum.org) was set up in 2007 to promote the wide-scale adoption of femtocells. The Forum supports and drives the adoption of industry wide standards and common architectures to enable the widespread adoption & deployment of femtocells by operators around the world. It directs and implements a multi-faceted marketing campaign raising the profile, driving technology development & deployment and promoting the potential of femto solutions among industry stakeholders, journalists, analysts, regulators, special interest groups, standards bodies and consumers.