The Spectrum Allocation Algorithm of Cognitive Radio Based on OFDM

Based on the characteristics of cognitive radio (CR) and the transmission features of OFDM, this article offers the algorithms for the spectrum allocation in OFDM. Aiming at the probability of detection by the CR and the upper limit of the noise which can be suffered by the authorized user, CR achieves the maximal channel capability through the allocation of the sub-carriers and the power. This article provides three algorithms: the Irrigation Algorithm with the capacity optimization, the Revision Greedy Algorithm with the minimum interference to the authorized user and the Grouping Allocation Algorithm with the minimum computation load. These three algorithms emphasize particularly on different characters about CR. The simulation indicates that when the amount of the sub-channels is great, the Revision Greedy Algorithm is suited for the CR; the Grouping Allocation Algorithm has a better real-time performance, although we need choose an appropriate grouping number to balance the complexity of computation and the loss of channel capacity.