Research On Wideband Spectrum Sensing Method Of Communication Signal

With the development of communication services,spectrum becomes more and more scarce.In order to increase the spectrum utilization,the study of spectrum sensing is of great significance.At present,spectrum sensing is gradually used in the military field,such as military communications and reconnaissance.O n the one hand,we need to perceive whether there is any alliance in the monitoring frequency band in the communication state and prevent other communication signals from occupying the frequency band.On the other hand,it is important to know whether there is an enemy is communicating in the monitoring frequency band,what frequency band is occupied by the enemy and what kind of signal is for communication,which provides important reference for subsequent interception of enemy information and selection of interference strategies.In military reconnaissance,how to perceive the communication signals with unknown parameters in a wide frequency band is an urgent problem to be solved.In order to solve the above problems,this thesis studies perceptual structure of wideband,signal detection and recognition.The main work of this dissertation is as follows.1.Wideband spectrum sensing structures are studied,including digital channelization structure and BigBand structure.According to their respective advantages and disadvantages,the two structures are combined using the characteristics of uneven distribution of communication signals in the spectrum,that is,digital channelization structure are used in the signal-intensive frequency bands,while BigBand structure in the sparse frequency band.The simulation verified the feasibility of using this structure for spectrum sensing.2.The methods of detecting communication signals with unknown parameters are implemented,including the time domain energy detection method,the frequency domain energy detection method and the autocorrelation detection methods,and the advantages and disad vantages of these methods are analyzed.The same false alarm probability and signal parameters are used for simulation to verify the detection effect of the three detection methods.The result shows that the frequency domain energy detection method works well for narrowband communication signals.3.A method for estimating the code rate or pseudo code rate of a communication signal is studied.This method first uses the best wavelet scale factor to improve the signal-to-noise ratio,and then estimates the code rate or pseudo code rate of the signal through the interval between spectral lines in the spectral map of the wavelet transform modulus.In this paper,the range of cutoff line is given by theoretical derivation,and the feasibility of this method is verified by simulation.The simulation results show that this method can accurately estimate the code rate or pseudo code rate for common eight kinds of communication signals,i.e.2FSK ? 4FSK ? BPSK ? QPSK ?16QAM?32QAM?64QAM?DSSS/BPSK,under the lower SNR.4.The characteristics of common eight kinds of communication signals in time,frequency and time-frequency domains are studied.Combined with the characteristics of the signals,the signal is averaged and denoised using the estimated code rate or pseudo code rate value.Then the amplitude histogram and frequency histogram are used to modulate and identify the signal.This paper presents a flow chart of modulation recognition of eight communication signals,and uses simulation to verify the recognition effect.