Shadow fading correlation between uplink and downlink

Selection diversity among base stations can be employed to combat shadow fading in mobile telephony. Selection of the strongest uplink received signal from a mobile at several base stations is straightforward. However, determining the base station from which to transmit to the mobile for downlink diversity often relies on the assumption that shadow fading on the uplink is highly correlated with the shadow fading on the downlink. Signal level data were collected from a GSM system in rural and suburban propagation environments at 1900 MHz. After averaging out the small scale multipath fading, the correlation between uplink and downlink shadow fading ranged between 0.66 and 0.92. The experiment, environment and results are described.