The Femto Forum, an industry group comprised of companies that support the widespread use of femtocells, has just announced the results of a study that indicates that femtocells have the capacity 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. (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 research assessed the impact of femtocells on a mobile network in a wide range of deployment scenarios to explore coexistence issues including interference. The simplest way to avoid interference between femtocells and macrocells is for them to operate on different radio channels. Unfortunately, not all 3G operators have enough spectrum to make this a viable solution. Still, the group came up with several technical solutions that would forestall interference even when both sets of cells are operating on the same radio channel. Adaptive pilot power control would dynamically adjust transmit power response to the current level of surrounding cells. Expanded tests for dynamic range would assure that femtocells are designed to operate reliably even in the presence of nearby high-power 3G mobile phones. Mobile phones would be equipped with uplink power capping—i.e., the phone would hand-off to the macro network before its transient power increased to the point where its noise would be a problem. Finally, automatic gain control, or adaptive attenuation, within the femtocell would allow it to provide good service to both nearby and more distant mobile phones.The entire 10.91-MB, 158-page report can be downloaded from the Femto Forum website.
Femtocell Group Proposes Techniques for Forestalling Interference
