Research On Physical Layer Watermarking Technology Based On TD-LTE

Recently,the research of physical layer security mechanism has become the focus of attention.As an important implementation of physical layer security mechanism,physical layer authentication technology has strong theoretical and practical significance.This thesis studies the watermarking technology in physical layer authentication,which embeds authentication information into transmission signal in the form of watermark.4G mobile communication has many advantages such as high speed,anti-interference and compatibility,and is widely used in the world.However,the processing flow of 5G in physical layer is very similar to 4G.Therefore,it is of great significance to study the physical layer watermarking based on TD-LTE(Time Division-Long Term Evolution),which is not only applicable to the communication mechanism widely used in the world,but also has important reference value for the future mechanism.In this thesis,a watermarking scheme applied to TD-LTE system is designed,which takes the frequently used calling as an application scenario.Firstly,the USRP(Universal Software Radio Peripheral)is used to receive the actual data when the user makes a phone call,and then the actual data is analyzed with reference to TD-LTE physical layer protocol.According to the analysis results,TD-LTE signals can be divided into user data signals and demodulation reference signals.The former is used for transmitting user data and the latter is used for channel estimation.In order to reduce the interference of watermark to user information,this thesis embeds watermark into the phase of demodulation reference signal.In order to reduce the influence of watermark on the channel estimation of demodulated reference signal,a watermarking scheme based on phase symmetric embedding is adopted in this thesis.In order to reduce the bit error rate of watermark transmission,this thesis adds channel coding to the watermark generation scheme.In order to prevent the third party from deciphering the watermark,the existing watermarking scheme generates the watermark by hashing the user bit and the shared key between the legitimate communication parties,so that different watermark signals can be embedded in different data frames.In order to reduce authentication errors caused by demodulation errors of user information,this thesis proposes the concept of pseudo-user bits,and uses pseudo-user bits instead of user bits as parameters of watermark generation.In this thesis,the proposed watermarking scheme is simulated in Gaussian channel and Rayleigh fading channel,and compared with the existing watermarking scheme.The system performance is measured by the key indicators such as error rate of user signal,error rate of watermark,transmission success rate of user signal,transmission success rate of watermark and authentication success rate.In particular,considering that the carrier frequency of mobile phone cannot be completely accurate in the actual communication process,the performance of watermarking system with the frequency offset is also simulated in this thesis.The simulation results are consistent with the expected results,which prove that compared with the existing common watermarking scheme,the watermarking scheme proposed in this thesis has good anti-noise and anti-frequency offset performance,and reduces the impact on user data.Finally,the performance of watermarking system in real environment is verified by USRP,and the results show that the watermarking scheme proposed in this thesis has good feasibility.