A comparison of indoor radio propagation characteristics at 910 MHz and 1.75 GHz

There has recently been much deliberation regarding whether indoor radio communications systems should operate in the 900 MHz band, or in the 1.7 GHz band. However, there are no propagation results available in the literature which compare indoor channel characteristics in the two bands. This paper presents the results of temporally and spatially distributed wideband (impulse response) propagation measurements on fixed indoor radio channels in these bands. Impulse response parameters, as well as envelope fading and frequency correlation statistics are presented and compared for the two bands, and for two different buildings. Results from the temporal experiments show that for a specific location in either of the two buildings, the dynamics of indoor channels are slightly less random at 910 MHz than at 1.7 GHz. It is believed, with due regard for the quasi-static nature of the fading, that this would result in marginally better performance on a given transmit/receive link in the 900 MHz band. The spatially distributed measurements showed that the structures of average impulse response envelopes differed for channels in the two buildings. In one building, rms delay spreads were slightly greater in the 1.7 GHz band for over 90 percent of transmit/receive link configurations. In the other building, rms delay spreads were marginally greater in the 900 MHz band for 70 percent of the configurations. It was also found that the standard deviation of rms delay spreads for different link configurations was greater for both frequency bands in this building. I n both buildings, the standard deviation was greater for the 1.7 GHz band results. These differences in rms delay spread standard deviations are considered to be important in the evaluation of coverage capabilities in different buildings and for different frequencies of operation.