HomeNewsFemto Forum announces results of femtocell interference research

    Femto Forum announces results of femtocell interference research


    The Femto Forum, the independent industry and operator association that supports femtocell deployment worldwide, has announced the results of its femtocell radio study.  The study found that femtocells have the potential to deliver an order of magnitude more capacity than the macro network alone when used in dense deployments, even when occupying the same radio channel as the macrocells. It also identified numerous technological solutions that mitigate potential interference with the macro network to remove barriers to wide-scale deployment and maximize the capacity benefits.

    The research assessed the impact of femtocells on a mobile network in a wide
    range of deployment scenarios in order to explore co-existence issues
    including interference.

    The study looked at both femtocells using a separate carrier to the
    surrounding macro network and those using the same carrier – which pose 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 enough spectrum for this to be practical. The Femto Forum therefore
    identified technological solutions that mitigate the potential interference
    where femtocells share the same carrier as the macro network. These methods
    are already being developed for pre-standard femtocell solutions, and Femto
    Forum members are working to bring them within the standards framework.

    The key solutions are:

    .       Adaptive Pilot Power Control, whereby the femtocell dynamically
    adjusts its transmit power in response to the current level of signals from
    surrounding cells and the desired coverage area.

    .       Extended Tests for Dynamic Range, to ensure that femtocell designs
    are able to operate reliably even in the presence of nearby high power
    mobile phones connected to the macro network (this test has already been
    incorporated into the latest 3GPP Release 8 25.104 specification).

    .       Uplink power capping of the mobile phone when operating in the
    femtocell environment, ensuring that, even in difficult radio conditions,
    the phone hands-off to the macro network before its transmit power increases
    to the point where macro noise rise is a problem.

    .       Dynamic receiver gain management in the femtocell (Automatic Gain
    Control or adaptive attenuation), to ensure that femtocells can offer good
    service to both near and far mobile phones without unnecessarily increasing
    the phone transmit power, therefore keeping the noise rise to a minimum.

    This particular study relates to WCDMA, but the Femto Forum represents the
    full range of radio standards and similar studies are underway for other air

    "At a time when mobile operators are seeing data usage rocket, femtocells
    offer an economic and effective way to deal with demand," said Professor
    Simon Saunders, the Femto Forum's Chairman. "By utilizing the identified
    interference management techniques it has been shown that femtocells offer
    operators an effective method to increase capacity and coverage within their
    existing networks through dense cell deployments."