Indoor wireless infrared channel characterization by measurements

Use of infrared light for indoor wireless communications has received considerable attention recently. In this paper, we present results obtained from a large set of measurements performed at the University of Ottawa. We investigate impacts of receiver rotation and shadowing on the properties of indoor infrared channels. This paper contains a description of a measurement system developed and used throughout the experiments. Measurement results are used to find and present methods to estimate variations of channel path loss for small changes in the receiver direction, using statistical techniques. This would be useful for generating samples of channel path loss for system performance simulations and modulation analysis. Using the measurement results, it is shown that variations of channel path loss are smooth and a simple curve-fitting algorithm can be used to accurately interpolate intermediate values. It is also shown that for a receiver changing its elevation angle from 0 degrees to 180 degrees, five points along the entire path are sufficient to predict variation of channel path loss for the entire rotation range. The results also demonstrate a correlation between the channel delay spread and channel path loss for both diffuse and line-of-sight configurations. A simple formula can provide an estimate of channel delay spread for a known path loss of a given configuration. It is demonstrated that variations of channel path loss for small changes of receiver rotation can be described by a Gamma distribution. This enables generation of samples of channel path loss under general conditions for system-level simulation algorithms. Measurements have also been performed to investigate effects of shadowing on indoor infrared channel characteristics. Some important parameters that specify the impact of shadowing on the channel characteristics are included in the measurement plans. Variations of channel path loss due to shadowing and due to these parameters are investigated and detailed results are reported. It is shown that shadowing affects the channel delay spread. For the measured shadowing results, it is shown that channel path loss and delay spread are correlated and their relationship is provided.