The results of temporally and spatially distributed wideband (impulse response) propagation experiments in the 900 MHz and 1.7 GHz radio frequency bands in two different buildings on fixed indoor radio links are reported. 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 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% of transmit/receive link configurations. In the other building, RMS delay spreads were marginally greater in the 900 MHz band for 70% of the configurations.>

A nationwide data network is planned that will employ microwave relay networks for both long-haul and short-haul interconnection. A digital modulation technique has been developed that has the constant level advantage of frequency-shift keying (FSK) systems while retaining the error rate and threshold performance of coherently detected binary or four-phase phase-shift keying (PSK). Occupied spectrum and interference characteristics of a 21.5-Mbit/s data system are compared to the more conventional 600-, 1200-, and 1800-channel message systems.