Power optimization for multiuser MISO-OFDMA based cognitive radio systems

This paper proposes analysis power optimization for MISO-OFDMA down-link based cognitive radio system that maximizes the sum rate of multi secondary users (SU). The problem is solved based on dual optimization method under constraints on the tolerable interference thresholds between secondary users and primary user´s (PU) frequency bands and the total transmission power. In proposed system, multiple transmit antennas cooperatively design their respective transmit beamforming vectors (MISO) to optimize the system performance. Accordingly, this MISO technique has been applied to OFDMA Cognitive system to compensate for the impact of from PU to CR. The simulation results are presented showing how CR coordinator determine the position and power which are assigned to each CR subcarrier to maximize the transmission throughput and the suggested MIMO system has more more enhanced and efficient total throughput then previous SISO system.