Radiowave propagation measurements for sharing spectrum between point-to-point microwave radios and personal communications systems

A CW radiowave propagation experiment was performed to study spectrum sharing possibilities in the New York City region. The results showed that the isolation measured between the microwave and a PCS system on the street was more dependent upon building shadowing and street orientation within the city than on the distance between the two systems for distances less than 20 km. At greater distances, the topography, including intervening hills and the curvature of the Earth which could shield the systems, played a strong role in providing isolation. The system dependent isolation required for sharing could be found even in the conventional main beam direction in locations surrounded by shadowing objects. Conversely, strong signals were often found well away from the main beam. Thus, there was measurable degradation of the microwave antenna discrimination relative to its (free-space) directivity. Closer in, the isolation varied widely, with regions of strong signals popping up in the shadows. The median difference between co-polarized and cross-polarized signal levels was only 7.5 dB. Occasionally, cross-polarized signals were stronger than cc-polarized signals. Statistical area models under-predicted the isolation, missing most sharable regions.<
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