The Wideband Spectrum Sensing Based On SFFT In The Cognitive Communication

The electromagnetic spectrum plays a crucial role in this communication medium in wireless communications.However,spectrum resources are very tight and users need to use them within the frequency bands allocated by the government.At present,static spectrum access is mainly adopted in communications.When the spectrum is in an idle state,unauthorized users cannot use it.This causes a waste of spectrum dimensions to some extent.With the continuous development of communications,the dynamic spectrum access method can ease the pressure on spectrum resources.Cognitive Radio(CR)points out that users should have cognitive functions,and on the basis of software radio,through the detection of spectrum resources,find free frequency bands and modify the hardware parameters to communicate the process.The key of cognitive radio is to find unoccupied spectrum resources.The spectrum sensing technology finds the spectrum resources available to the user by analyzing the complex spectrum environment.As a key technology in CR,spectrum sensing technology directly affects the performance of cognitive systems.Broadband spectrum sensing can increase the access probability of cognitive users and has important significance in cognitive radio systems.However,Nyquist's theorem indicates that the sampling frequency must be greater than twice the bandwidth,which undoubtedly increases the hardware implementation difficulty and perceived time.The MIT artificial intelligence laboratory proposed a Sparse Fast Fourier Transform(SFFT)algorithm.The SFFT algorithm is mainly aimed at sparse signals,which can greatly improve the operation efficiency and reduce the sampling frequency.In this paper,a wideband spectrum sensing method based on SFFT is proposesed that can solve non-sparse cases.By preprocessing the signal,the signal is sampled at a rate 2 to 8 times lower than the Nyquist sampling rate,and then the spectrum is recovered and the channel state is estimated according to the energy detection algorithm.Finally,we use the USRP hardware platform to build a cognitive communication system,and verify the wideband spectrum sensing based on SFFT in the system.