Radiowave Propagation Measurements for Sharing Spectrum Between Point-to-Point Microwave Radios and Personal Communications Systems
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A CW radiowave propagation experiment was peiformed in the New York City region to study spectrum sharing possibilities between point-to-point microwave systems and personal communications systems (PCS). 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 separation between transmitter and receiver causes a significant increase in isolation due to increased terrain variations and earth curvature. The system dependent isolation requiredfor sharing the spectrum with a few PCS radiators could be found even in the conventional main beam direction in regions shadowed by surrounding objects. Conversely, strong signals were often found in directions well away from the main beam. Thus, there was measurable degradation of the microwave antenna discrimination relative to its “free-space” directivity. At all distances, the isolation varied widely, with noticably strong signals popping up in larger shadowed areas. Low power systems with low antenna heights and small cell sizes, on the order of a city block or leis, would have a better probability offinding suitably isolated regions to operate in. Large cell, high-powered systems with high antennas may need to move well beyond the horizon to share spectrum.
KeywordsAntenna Gain Share Spectrum Main Beam Discrimination Function Microwave Antenna
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