Design considerations for broadband indoor infrared wireless communication systems

Recently there has been a growing interest in using infrared light for broadband indoor wireless communications. There are two major limitations for establishing a wideband infrared communications link. The first and most important limit is the power requirements of such a link. The second important impairment is the intersymbol interference caused by multipath dispersion. In this paper we address the issue of designing an optimized transmission system to provide the best power efficiency for an infrared link. Important parameters that should be considered for this design and some examples of efficient link designs are discussed. The suggested designs can improve the power efficiency of an indoor infrared link up to 4 to 8 dBo while providing a smaller rms delay spread, more robustness to shadowing and a more uniform distribution of power. Characteristics of the indoor infrared channel depends upon the directions of the receiver. This dependency can be used in designing a direction diversity receiver to decrease the rms delay spread of the received signal and to reduce the effects of noise by using proper combining techniques. We discuss the effects of receiver direction and field-of-view on the channel parameters and suggest a configuration for a direction diversity receiver.