Combined Estimation of Power Allocation and Channel in OFDM-Based Opportunity Spectrum Access System

In this paper, we investigate the power allocation strategy that aims at maximizing the capacity in OFDM-based opportunity spectrum access(OSA) systems. The channel estimation techniques for OFDM systems based on pilot arrangement are considered. The combined power-allocation and channel estimation based on comb type pilot arrangement is studied through different strategies .We try to estimate channel at pilot frequencies and power allocation of the subcarriers simultaneously. The combined estimation is based on LS while the channel interpolation is linear interpolation. We show that the traditional water-filling strategy applied in general OFDM systems needs to be modified due to the per subcarrier power constraints in such systems. A smooth water-filling strategy is proposed and show better performance .