Hier finden Sie wissenschaftliche Publikationen aus den Fraunhofer-Instituten.

A physical model of the wireless infrared communication channel

: Jungnickel, V.; Pohl, V.; Nonnig, S.; Helmolt, C. von


IEEE Journal on Selected Areas in Communications 20, (2002), No.3, pp.631-640
ISSN: 0733-8716
Journal Article
Fraunhofer HHI ()
multipath channels; optical links; optical transfer function; wireless infrared communication channel; indoor environments; diffuse component; line-of-sight component; direct component; ulbricht's integrating sphere; los component; transfer function; rician factor; electrical power; k-factor; infrared links; data transmission; directivity; high-speed infrared communication

A simple analytical model of the wireless infrared communication channel in indoor environments is presented. The infrared signal is modeled as the combination of a diffuse component and a line-of-sight (LOS) or direct component. For the diffuse component alone, the properties of the channel are found using Ulbricht's integrating sphere. When a LOS component is also present, the transfer function depends upon the Rician factor K given by the ratio of the electrical power in the LOS and diffuse signals after the detector. For small K, the transfer function shows notches down to low frequencies, but due to the nature of light never for zero frequency. We confirm that a K-factor >or=13 dB is required also in infrared wireless links in order to support distortionless data transmission beyond 100 Mbit/s. Increasing the directivity at the receiver and/or at the transmitter improves the effective value of K. Here, we show that a moderate directivity will be sufficient for high-speed infrared communication in typical indoor scenarios.