Research On Ambient Backscatter Communication System Based On MFSK Modulation

The Ambient Backscatter Communication(Am BC)system uses Radio Frequency(RF)sources existing in the environment to provide energy and communication,and the power consumption of the transceiver is significantly lower than that of the traditional radio communication system.This makes it a representative of low-power networks and Internet of Things(Io T)applications.However,the presence of jammer often poses great challenges to systems detection? In addition,the broadcast characteristic of the system makes the transmission easy to be eavesdropped,which affects the security of the physical layer of the system.The main work and innovations of this master’s thesis are as follows:1)This thesis first introduces the multi-antenna ambient backscatter communication system model with Multiple Frequency Shift Keying(MFSK)modulation.The receiv-ing model of the system in the presence of jammer is analyzed.An adaptive detection algorithm based on the maximum a posterior probability criterion is proposed.The simu-lations demonstrate that the detection performance of the system gradually increases with the increase of receiving antennas.Compared with traditional detection algorithms,the proposed algorithm performs better in the presence of jammer.2)Due to the high algorithm complexity of the proposed adaptive detection algo-rithm based on the maximum a posterior probability criterion,this thesis proposes an anti-jammer detection algorithm based on the energy threshold.The simulations demonstrate that when the frequency spectrum of the jammer overlaps with the passband of the filters at the receiver with low power,the adaptive maximum a posterior detector performs better.Conversely,the anti-jammer energy threshold detector outperforms the adaptive maxi-mum a posterior detector.In addition,the detection performance of anti-jammer energy threshold detector is also superior to traditional detection algorithms in jammer situations.3)In order to enable the reader to distinguish between the tag and malicious imitators,the physical layer authentication algorithm based on power spectral density is proposed.It divides the system into two stages: authentication training and information transmis-sion.The authentication probabilities of the tag and imitators are obtained under different signal-to-noise ratios.4)Finally,based on the system model,this thesis proposes to add random noise to RF sources to resist eavesdropping,so as to improve the security capacity of the system.Given the total power,the optimal allocation ratio of the RF sources and random noise is designed,and the system outage probability is analyzed.The system outage probability with and without noise signals is also compared through simulation analysis.