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Optimization of In-house WLAN by Selection of alternative Frequency Bands

The higher the frequency, the more transmission power is needed for a given distance and bit rate. There are mainly two reasons for this: First, the free space attenuation - at least with linear antennas - is linked to the wavelength by a constant ratio between effective antenna area and the respective wavelength. Second, higher frequencies tend to be absorbed by building structures and furniture. This can be observed in practice: Whereas a 2.4 GHz link may work across one or two walls, a 5 GHz link may have serious problems even with the first wall. Selection of even lower frequency bands enables WLAN with even less transmission power.

Due to regulation, these frequency bands are not available today for unlicensed use. Nevertheless, one may assume that a long term migration to different rules is possible. Using intelligent, adaptive Mechanisms for the selection of the actual frequency, a more effective use of the restricted wireless spectrum seems possible. So, there are good reasons, for basic research on the usage of alternative frequency bands.

Today's UHF band, that is mainly reserved for TV and audio broadcast services is a candidate for such a band. Of course, any interference with the primary user in its intended service area must be avoided. This can be done with intelligent systems that will recognize the primary user and perform effective transmission on a locally unused carrier frequency.

This project is granted by the "Bundesministerium für Bildung und Forschung (BMBF)" as part of the granted project "Minimierung der Immision künftiger Funkdienste (Miniwatt II)" - "Mimimization of the Emssioins of future Radio Services".

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Dr.-Ing. Wolfgang Endemann
Tel.: 0231 755-3195