Theoretical analysis of frequency-correlation coefficient for received signal level in mobile communications

Frequency-correlation coefficient characteristics that define frequency separation in frequency-diversity techniques were studied theoretically using a propagation model that makes allowances for received bandwidth. Equations of frequency-correlation coefficients in non- and line-of-sight propagation paths were derived. The equations showed that frequency-correlation coefficient depends on such factors as frequency separation, received bandwidth, differences in pathlengths, and the power ratios of the direct to indirect waves. The frequency-correlation coefficient increases as the received bandwidth increases and decreases as the difference in pathlength increases. However, when the difference in the pathlength was small (30 m), the effect of the received bandwidth was minimal. The frequency-correlation coefficient also depended somewhat on the power ratio. To confirm the accuracy of our theoretical derivations, computer simulations were performed. Frequency-correlation coefficients were calculated by simulating instantaneous received signal levels. The theoretical results matched those of the simulation