Space and frequency diversity measurements of the 1.7 GHz indoor radio channel for wireless personal communications

The authors empirically evaluate three diversity schemes for indoor wireless personal communications. Measurements at 1.75 GHz, using a four-branch diversity receiver and selection combining (SC), are analyzed to determine the effects of physical parameters, signal fading statistics and a switched combiner on diversity performance. Results are obtained from numerous locations and over 800 measurements. These indicate that antenna separations of as small as a quarter wavelength provide significant diversity gains. For similar performance, frequency diversity requires separations of at least 5 MHz. A 4-branch combination of these schemes (hybrid diversity) yields on average a 16 dB improvement at 99% signal availability. The local mean variations between branches in these measurements is ±3 dB but this has a negligible effect on average diversity performance using ideal SC. The diversity gains are shown to have a variability of ±2.5 dB. Switch and stay combining (SAS), a form of SC, is sensitive to the input fading statistics and to switch delay. These variations in diversity performance should be considered for a worst case link design