OFDM (Orthogonal frequency division multiplexing) signal spectrum sensing method for asynchronous time without frequency offset

Abstract

The invention discloses an OFDM (Orthogonal frequency division multiplexing) signal spectrum sensing method for asynchronous time without frequency offset. Received signals from monitoring channels are sampled, thereby obtaining sampling signals; estimation is carried out through utilization of the autocorrelation of cyclic prefixes of the OFDM signals in the received signals according to sampling values of all sampling points in the sampling signals under the condition that the time is asynchronous and the frequency offset does not exist, thereby obtaining noise power; a covariance matrix of the sampling signals is calculated according to the sampling values of the sampling points in the sampling signals; the test statistics is calculated according to the noise power and the covariance matrix of the sampling signals; and through comparison of the test statistics and an obtained judgment threshold, whether licensed user signals exist in the monitoring channels or not is judged, thereby realizing spectrum sensing. The method has the advantages that the spectrum sensing performance of the OFDM signals can be effectively improved, and the computing complexity is low.

Description

technical field [0001] The present invention relates to a spectrum sensing method in a cognitive radio system, in particular to a noise power estimation-based OFDM signal spectrum sensing method for time asynchrony and no frequency offset. Background technique [0002] With the rapid development of communication technology and people's increasing requirements for communication data rate and quality, the demand for bandwidth has increased significantly. However, the existing fixed spectrum allocation mechanism makes the spectrum utilization rate very low. In 2009, the Wireless Technology Research Institute of China Mobile Research Institute conducted actual measurements on the utilization of authorized spectrum in my country. The actual measurement results showed that the utilization rate of most of the spectrum was less than 5%, and some were even close to 0%. In order to improve spectrum resource utilization, technologies such as dynamic spectrum access (Dynamic spectrum a...

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Problems solved by technology

However, the existing fixed spectrum allocation mechanism makes the spectrum utilization rate very low

In 2009, the Institute of Wireless Technology of China Mobile Research Institute conducted actual measurements on the utilization of authorized spectrum in my country. The results of the measurement showed that the utilization rate of most of the spectrum was less than 5%, and some were even close to 0%.

The covariance matrix-based spectrum sensing method proposed by Zeng et al. in "Spectrum sensing algorithms for cognitive radio based on statistical covariance (spectrum sensing method based on statistical covariance in cognitive radio)" in 2009 can utilize the Correlation realizes spectrum sensing, which has the characteristics of low calculation amount, but this method does not consider the specific situation of time asynchronous and no frequency offset, so the cyclic prefix autocorrelation characteristic of OFDM signal cannot be effectively used

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