Digital adaptive beamforming (ABF), with its ability to enhance frequency reuse and co-channel-interference rejection for improved service capacity and link quality, is expected to play an important role in future wireless communications. However, the performance of such a digital communication system strongly relies on the accuracy of synchronization. This paper investigates the system performance of digital adaptive beamforming in a digital QAM receiver in the presence of synchronization errors. The simulation results show that digital adaptive beamforming can cancel interference while simultaneously compensate for the carrier phase and frequency offset to support a reliable 64-QAM link. However, this system is very sensitive to the symbol timing error and the sampling timing offset. The system employing both ABF and adaptive equalization, which can reject interference in a multipath environment, is able to compensate for the symbol timing error and the sampling timing offset. The tracking range of the carrier frequency offset is also improved in the system with both adaptive beamforming and equalization.
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