Gain improvement of a cellular base station multibeam antenna

Abstract

For both 900MHz and 1.9 GHz wireless systems, one economical approach to the problem of increasing capacity and coverage is to use multibeam adaptive base station antennas. Experimental test results are used to determine the gain improvement which can be achieved from a multibeam antenna array relative to a traditional dual-diversity three-sector antenna configuration. The multibeam antenna uses selection combining to switch the signals from the two strongest directional beams to the base station's main and diversity receivers. To assess the impact of the beamwidth on the overall system performance, the following two multibeam antennas were tested: a 12 beam 30/spl deg/ beamwidth array and a 24 beam 15/spl deg/ beamwidth array. Both antennas were field tested in typical cellular base station sites located in heavy urban and light urban environments. The performance of the multibeam antennas are compared in the different environments based on two sets of receive signal strength statistics. The first set of results characterizes the relative power differences and beam separations of the signals measured in each directional beam of the multibeam antenna. The second set focuses on gain improvements achievable with the multibeam antenna compared to the traditional sector configuration. The results indicate that in excess of a 5 dB of gain improvement can be achieved with a 24 beam base station antenna in a cellular mobile radio environment.