Orthogonal frequency division multiplexing (OFDM) frequency domain interpolation pilot frequency-based cyclostationary feature spectrum sensing method

Abstract

The invention discloses an orthogonal frequency division multiplexing (OFDM) frequency domain interpolation pilot frequency-based cyclostationary feature spectrum sensing method. The invention mainly aims to solve the problems that the performance of the traditional sensing technology is limited by the length of a cyclic prefix, and the performance is lowered by the random variation of a pilot frequency phase. The OFDM frequency domain interpolation pilot frequency-based cyclostationary feature spectrum sensing method comprises the following implementation steps of (1) transforming a time domain signal into a frequency domain signal by performing fast Fourier transformation on the time domain signal received by a receiving end; (2) calculating a spectral correlation function of the frequency domain signal by utilizing a time domain smoothness periodogram method; (3) selecting feature points from the spectral correlation function; (4) constructing corresponding test statistics by utilizing the selected feature points according to the channel condition; and (5) comparing the test statistics with corresponding sensing judgment thresholds so as to judge whether a master user signal exists in a channel to be sensed or not, and giving the reliability tolerance of the master user signal. The OFDM frequency domain interpolation pilot frequency-based cyclostationary feature spectrum sensing method disclosed by the invention does not depend on the length of the OFDM symbol cyclic prefix, is good in detection performance under the low-signal to noise ratio fading channel condition, and can be widely applied to various broadband wireless OFDM communication systems.

Description

technical field [0001] The invention belongs to the technical field of wireless communication, in particular to a spectrum sensing method for wireless communication orthogonal frequency division multiplexing OFDM modulated signals, and further relates to a cyclostationary characteristic spectrum sensing method based on OFDM frequency domain interpolation pilots, which can be widely used in Various wideband OFDM wireless communication systems with interpolated pilots in the frequency domain. Background technique [0002] Radio spectrum is a limited physical resource shared by various wireless services. The spectrum authorization mechanism provides an effective way to ensure high-quality services and avoid interference, but this mechanism leads to very low utilization of radio spectrum resources. With the substantial increase in the demand for modern wireless communication services, the demand for radio spectrum resources will also further increase, and people have to pay atte...

AI Technical Summary

Problems solved by technology

Because the OFDM signal has its own unique characteristics, a targeted spectrum sensing method can be used for it. One is the sliding window energy detection method based on the OFDM cyclic prefix. Its advantage is that it is very simple to implement, but it needs to calculate multiple cyclic prefixes. length of the sliding window, so the complexity is very high, and the calculation of the perceptual decision threshold needs to know the accurate information of the noise variance, that is, its performance is very easily affected by the error of the noise variance estimation; for this reason, someone proposed a method based on autocorrelation The energy detection method has the advantage of low complexity and does not need to know the information of the noise variance, but its performance is closely related to the length of the cyclic prefix, the longer the cyclic prefix, the more reliable the detection, and most OFDM systems are out of throughput Considering that the length of the cyclic prefix is ​​usually not very long; for this reason, someone proposed a detection method based on the correlation between symbols in the time domain based on the matched filter perception method of OFDM interpolation pilot processing. The basic idea is that when two OFDM When the symbols have the same distribution of interpolated pilot symbols in the frequency domain, the pilot information in the symbol can be extracted through the correlation between OFDM symbols in the time domain. The frequency domain pilot information extracted by this method is a more effective test statistic , its performance is better than the detection method based on the cyclic prefix, however, it is impossible for the OFDM system to send the same pilot sequence in two symbols, so this method is difficult to apply in practice

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