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Minimalization of Femto NodeB Radiation in Direction of Windows Disclosure Number: IPCOM000198568D
Publication Date: 2010-Aug-09
Document File: 2 page(s) / 466K

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Minimalization of Femto NodeB Radiation in Direction of Windows

Andrzej Wąż-Ambrożewicz, Maciej Pakulski, Patryk Pisowacki

The publication relates to the Femto concept of wire- less cellular networks. The Femto nodes, called Home Node Bs (HNB) or Home enhanced Node Bs (HeNB), in UTRAN (Universal Terrestrial Radio Access Net- work) and LTE (Long Term Evolution) are small indi- vidual base stations that are installed for the most part by the individual users at their premises. The novelty of the Femto concept lies in the fact that while the mobile network operator still has the overall author- ity over the Femto nodes, it does not perform the net- work-planning nor it deploys the nodes. The situation results in the uncoordinated deployment, where the mobile network operator has no detailed knowledge about the network topology.

The uncoordinated deployment of the Femto nodes will cause an increase in the level of interferences, and this will affect not only the users of the other nearby Femto nodes, but can also degrade the performance of the macro network (i.e. the overlay part of the same cellular network, based on the conventional (e)Node Bs). In extreme situations, this may lead to the un- availability of the macro network, especially in the ar- eas of the dense deployment of the Femto nodes, e.g. a building with multiple individual apartments or an of- fice park with a multitude of individual small separate offices. The problem is aggravated if both the Femto and the macro parts of the mobile network use the same frequency resources. The increase in the level of the interferences is partly due to the fact that the Fem- to access points (HNBs or HeNBs) are typically using omni-directional antennas to assure sufficient cover- age and to allow out-of-the-box operations (no skills are needed during the installation of the equipment).

Several approaches exist to solvethe problem. An ex- ample to minimize the interference is the use of the X2 interface (LTE systems), where the interference co- ordination messages are exchanged between adjacent eNBs or HeNBs. The problem, however, is that up to now it is not possible to exchange these data between the macro and the Femto layer. Moreover, due to the potentially high number of involved HeNBs, the ap- proach may not be practically feasible.

Another method to avoid Femto-to-macro interferenc- es is to use additional resources (e.g. frequency band) dedicated only for Femto or as an emergency band for the macro users tha...