This paper reports experimental and modeling studies that investigate the dependence of indoor radio channel multipath characteristics on a transmit/receive range. Specifically, a simple model for estimation of the complex baseband equivalent impulse response for indoor channels is explained. Using this model, the relationship between rms delay spread and range on static indoor channels is estimated from simulations. Results show that this relationship is nonmonotonic, and has a maximum at a range that depends on the building dimensions and the electrical properties of reflecting surfaces. The model is then used in infinite, as well as finite, resolution modes to supplement the measurements of impulse response characteristics in different buildings using a limited resolution channel sounder. Experimental and modeling results are then combined to derive conclusions which confirm the anticipated nonmonotonic relationship exists in empty buildings. Measurement results demonstrate, however, that furniture has the effect of destroying this relationship, making rms delay spread almost independent of range. The possible influence of adjacent buildings that can be seen through windows is also noted.
