| 抄録（英） |
CR(Cognitive Radio) has been attracted attentions to resolve the problem related to lack of frequencies. For the CR, if we detect the unused frequency band which is used by licensed PU(Primary User), SU(Secondary User) starts to use the frequency band. In the conventional scheme, centralized control manages frequency resources to avoid the interference between PU and SU. However, there are problems related to infrastructure construction cost increment caused by miniaturization of cell size and CR has little flexibility when it starts. In this paper, we study autonomous PU detection scheme by SU when PU starts to use the licensed frequency band, which needs neither management of frequency by centralized control, nor side information which is a part of the frequency band. We assume that PU modulation is OFDM(Orthogonal Frequency Division Multiplex). After SU calculates the correlation between CP(Cyclic Prefix) and effective symbol, the one with a high correlation is regarded as a synchronous candidate. Then the pilot subcarriers are extracted from OFDM symbol of synchronous candidate in the frequency domain. To detect PU, IFFT(Inverse Fast Fourier Transform) is applied to the extracted subcarriers which is multiplied known pilot subcarriers. The detection probability is evaluated by the computer simulation, and the effectiveness of the proposed method is shown. |