Joint Optimization for PAPR Reduction and Opportunistic Beamforming (OBF) in OFDM Systems

Opportunistic beamforming (OBF) is an effective way to increase the multiuser diversity (MUD) of the communication systems; with employing OBF in OFDM system, in addition to the MUD gain, frequency diversity gain is also obtainable. However, the complexity of the OBF-OFDM system is increased and the peak-to-average power-ratio (PAPR) of the OFDM signals must be reduced. The reduction of signals' PAPR and complexity of the system is modeled as the design of phase sequences in this paper. Hence, periodic phase sequences are designed and employed to reduce the OFDM signals' PAPR and the complexity of the normal OBF-OFDM system simultaneously, where the transmit data at all antennas can be generated in time domain directly via one N-point IFFT. The simulation results show that, after the proposed schemes are adopted, complexity of the OBF-OFDM system is reduced and the system throughput, both in the maximum throughput scheduling scheme and the proportional fairness scheduling scheme, is almost same as that of the normal OBF-OFDM system and greater than that of non-OBF OFDM.