Prediction of the space-frequency correlation function for base station diversity reception

In this paper, a model is proposed to estimate the signal statistics for urban-area base stations with highly elevated antennas, Based on the model, the envelope correlation of the received signal is estimated in the case of hybrid space-frequency diversity reception at the base, It is shown that the spatial correlation oi the complete signals is determined by the mean angle of arrival and the width of the incoming beam Useful closed-form approximations for inline and broadside antenna orientations are obtained, Comparisons between the theoretical model and available experimental data provide adequate justification for the model, It is shown that the lowest spatial correlations among all the possible angular orientations are obtained when the mean direction of incoming signals is perpendicular to the axis of the base antennas, For this case, an antenna separation of 26 lambda is required to achieve an envelope correlation of 0.7 when the width of the incoming beam is 0.7 degrees, and this separation reduces to 9 lambda for a width of 3 degrees, The results indicate that the required spacings can he further reduced by using frequency diversity in conjunction with space diversity, Generalization of the model to incorporate local scattering effects is also proposed.