Measurement results on indoor radio frequency re-use at 900 MHz and 18-GHz

Current interest in indoor radio applications for wireless communications spans a wide frequency range: from the 902-928 MHz ISM band, to the 18 GHz band allowed by the FCC´s recent rulemaking for low-power high-speed data and voice communications. The authors report measurements of indoor radio propagation in these two bands, in four indoor environments. They also examine the effects of the statistical variations in the instantaneous received signal level on system outage. They pay special attention to the feasibility of frequency reuse with and without antenna diversity. A plot of average attenuation as a function of distance is found to be well correlated with each site´s expected propagation characteristics. These expectations were derived from measurements of the radio transparency of various building materials and careful surveying of each site. Furthermore, the effects of multipath fading are characterized by calculating the outage probability of a hypothetical communications system employing selection antenna diversity. They find that, in general, attenuation increases steeply as a function of distance, so that the probability of interference between two users on the same frequency is small unless they are very close to one another. This suggests the possibility of a high degree of frequency re-use, and particularly so for the case when antenna diversity is used; the possibility is confirmed by the outage calculations. They also find that performance variations from site to site can be large due to different methods of construction