Propagation correlations at 900 MHz

The correlation in mean received power from four non-cosited 900 MHz sources is studied as a function of angle of arrival difference (AAD) at the mobile. Two tests are examined, one in the Washington-Baltimore area, and the other in the Chicago-Schaumburg area. Three hundred meter power averages were taken in Washington while 20 meter averages were obtained in Chicago. Weighted correlation coefficients averaging in the order of 0.7 were obtained at small AAD's. Serial correlations are also examined. A table lookup model of correlation coefficient versus AAD was obtained from the measurements. This was applied to the cellular system simulation to show differences in estimated performance with and without AAD correlation taken into account. The example given was assumed to be in an urban propagation enviroment with a 19-mile separation between co-channel users. Differences in 〈C〉/〈I〉 of 2.7 dB with omni antennas and 4.7 dB with 60-degree sector antennas are obtained at the level achievable at 90% of the locations.