Performance of multi-level QAM with maximal ratio combining space diversity for land mobile radio communications

A novel type of space diversity with maximal ratio combining for multilevel quadrature amplitude modulation (QAM) in land mobile communications to improve transmission performance is proposed. In order to realize maximal ratio combining space diversity for QAM, a novel type of diversity combining method using a pilot symbol insertion type fading estimator is applied. The proposed diversity combining is carried out at the baseband using digital signal processing, simplifying the diversity receiver hardware. Computer simulation and laboratory experiments confirm that the multilevel QAM using the proposed method is effective for improving the transmission performance of land mobile communications