Propagation

4615 mots 19 pages
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Propagation

Prediction

ModeIs

175

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4.7 Indoor Propagation Modeis
Jaakko Liihteenmiiki , VTT Information Technology, Finland 4.7.1 General

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Predicting the propagation characteristics between two antennas inside a building is important especially for the design of cordless telephones and WLANs (Wireless local area networks). Also the design of cellular systems with indoor base stations involves the use of indoor propagation modeis. The indoor propagation channel differs considerably from the outdoor ane. The distance between transmitter and receiver is shorter due to high attenuation caused by the internal walls and furniture and aften also because of the lower transmitter power. The short distance implies shorter delay of echoes and consequently a lower delay spread. The temporal variation s of the channel are slower compared to the conditions where the mobile antenna is mounted on a caT. As is the case in outdoor systems, there are several important propagation parameters to be predicted. The path loss and the statisticai characteristics of the received signal envelope are most important for coverage planning applications. The wide-band and time variation characteristics are essential for evaluation of the system performance by using either hardware or software simulation. The considered propagation models are divided into fauT groups: empirical narrow-band modeis, empirical wide-band modeis, modeis for time variations and deterministic modeis. Empirical narrow-band models are expressed in a form of simple mathematical equations which give the path loss as the output. The equations are obtained by fitting the model to measurement results. Empirical wide-band modeis are expressed in a form of a table listing average delay spread values and typical power delay profile (PDP) shapes. Modeis for time variations are used for example to estimate the Doppler spectrum of the received signal. Deterministic modeis are calculation

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