Research On Spectrum Allocation Combining Soft Decision Spectrum Sensing In Cognitive OFDM Systems

In recent years, a variety of new technologies are emerging with the rapiddevelopment of wireless communication, which has great demand of thespectrum resources. At the same time, the need for new business of the existingradio technology is also increasing. All of them resulted in the fact that the radiospectrum resource which was scarce became more strained. The problem needs to besolved, otherwise it will restrict the development of wireless communications.Cognitive radio has got attention and become a hot research as a new techn ologyto solve the problem.Before cognitive users shared the spectrum resources, they should sense thestate of spectrum and make a viable strategy to take advantage of the availablechannel resources. Today’s study is mostly about spectrum sensing and spectrumallocation. Many researches about spectrum allocation are trying to find a way toimprove the performance of cognitive radio system while not making muchinterference to primary users. But the researches have ignored the impact ofunfavorable spectrum sensing results. In fact, power allocation based onerroneous spectrum sensing results will always make much interference toprimary users, which violates the baisc principle that cognitive user should notdisturb primary users’ communication. Therefore, this article will jointlyconsider the spectrum sensing results and spectrum allocation to find analgorithm that can work well even in an unreliable situation.First, the article describes the purpose and significance of this study. Also theexisting technology of cognitive radio and some mathematical theories to be usedare introduced.Secondly, the spectrum allocation algorithm based on water-fill is discussedin the sitiation of the proposed system model. Futher by jointly considering thespectrum sensing results, an improved spectrum allocation algorithm aimed atthe unreliable spectrum sensing situation is proposed.Finally, some simulation about the proposed spectrum allocation algorithmis made. Numberical results show that the proposed algorithm can ensure a smallinterference even in an unreliable spectrum sensing situation.