Transmit beamforming and power allocation for downlink OFDMA systems

This paper considers a transmit beamforming and subcarrier power allocation method for orthogonal frequency division multiple access (OFDMA) systems. As the beamforming vector control criterion, we employ the maximization of so-called signal-to-leakage-plus-noise ratio (SLNR) at each base station, which enable us to obtain closed form beamforming vector by using only locally available information. We also discuss the local optimality of the SLNR based beamforming vector. As for the subcarrier power allocation, two different approaches are employed, namely, the equalization of signal-to-interference-plus-noise ratio (SINR) for subcarriers and the maximization of sum rate of subcarriers. Computer simulation results show the validity of the transmit beamforming and power allocation method with highlighting the difference between the two power allocation algorithms.