Effect of Antenna Power Roll-Off on the Performance of 3G Cellular Systems from High Altitude Platforms

An investigation into the impact of antenna radiation patterns on the performance of a 3G mobile communication system provided a single high-altitude platform (HAP) is presented. Use of elliptical and circular beam antennas is examined for a 91-cell system. Crucial performance parameters are shown to be the mainlobe power roll-off and sidelobe level. It is presented that the optimum power roll-off from cell center to the cell edge ranges between 10-35 dB, which is dependent on the types of antennas used, sidelobe level, and antenna gain strategy employed. Elliptical beam antennas are proven to provide the best solution, but circular beam antennas with their gain adjusted to reduce the degree of cell overlap and compensate for increasing path loss are shown to provide similar performance, with the advantage that they are practically more realizable. It is shown that poorer overlap performance can be partially compensated for by an increased power roll-off at the cell edge, a strategy that is employed in the case of the gain adjusted circular beam antennas. The impact of cell radius and elevation angles is also assessed.