Research On Anti-Jamming Technologies In High Speed Power Line Carrier Communications

At present,power line communication(PLC)has become a research hotspot of the communication layer of the Internet of Things due to its low cost,wide coverage,and low dropout.However,it is susceptible to severe clutter interference,which results in poor communication quality.Therefore,it is necessary to adopt optimized anti-jamming strategies to suppress various type of interferences.To solve this problem,on the premise of analyzing and studying the PLC transmission channel,this thesis studies the multi-carrier OFDM channel estimation and single-carrier transmission adaptive equalization optimization scheme under high-speed PLC transmissions.First,the development status of PLC and its multi-carrier and single-carrier transmission schemes are introduced.Second,the principle of PLC,the characteristics and models of PLC transmission channels are analyzed.Third,the researches on channel estimation under multi-carrier OFDM transmission are carried out.After that,the distortion compensation problem of PLC system under limited bandwidth is discussed.In combination with adaptive equalization technology under single carrier transmission,a dual-mode exchangable CMA-LMS equalization scheme suitable for high-speed PLC systems is studied.Finally,the anti-jamming scheme under PLC transmission is summarized and prospected.The main content and contributions of the full thesis are concluded as follows.First,a comprehensive analysis of the poor channel environment of the low-voltage PLC channel is carried out.Then the attenuation loss on the power line and the impact of multiple transmissions are taken into account.The power line multipath channel modeling is also completed under the theoretical guidance,which is convenient for subsequent channel estimation and the resistance of the adaptive equalization algorithm for valid verification.Second,the basic principle of power line multi-carrier OFDM system is introduced.Various traditional channel estimation methods are analyzed and compared in the perspective of theory and simulation experiments.To effectively eliminate the residual bias after estimation,a channel estimation scheme using K-means method to select appropriate anti-jamming is proposed.The harmonic sequence is desgned at the origin,and the interference of the training sequence on the data sequence is eliminated.According to the cluster analysis method,the time Statistical averaged singular value decomposition(SVD)channel estimation are carries out with iterative updates of noise and signals to achieve the purpose of time-domain denoising.It completes system estimation and recover channels,and thus improve systematical anti-jamming and the bit error rate performance.Then the simulations are carried out to verify the effectiveness of the proposed scheme.Third,in a limited-bandwidth power line channel,when single-carrier transmission is used and the rate is high,the inter-symbol interference also increases.To eliminate inter-symbol interference,a single-carrier equalization technique using phase-shift keying modulation is proposed.Based on the Constant Modulus Alogorithm(CMA)and Least Mean Square Error(LMS)method,a two-stage dual-mode CMA suitable for pwer line carrier communications is proposed.By selecting and optimizing the variable step size,the algorithm achieves fast convergence and stability,effectively reduces the influence of inter-symbol interference,and thus it realizes adaptive compensation of signals.In addition,the effectiveness of the proposed algorithm is verified through simulations,and its complexity is also analyzed for practical reference.This thesis can effectively improve the system performance and thus reduce complexity by optimizing the anti-jamming technologies in PLC systems.Therefore,it has high practical value and it can be widely used in practical PLC systems,especially in IoT application systems,which require low cost and reliable transmission and so on.