Application Of Spread Spectrum And Equalization In Powerline Communication System Based On OFDM

At present,Power Line Communication(PLC)technology with its advantage of no need to network's requirements is paid more attention to the field of communication technology.PLC is an information transmission protocol that uses electrical wiring as the medium.Orthogonal frequency division multiplexing(OFDM)is a kind of physical layer technology which is widely used in the PLC standards.In the power line communication channel,there are frequency selective fading and single frequency interference.This paper focuses on the problem of anti interference in PLC system,and the single frequency interference and multi-path interference is chosen as the main research object.Spread spectrum,equalization and OFDM technology is the main research means in the paper,and the performance of OFDM system and the interference suppression technology are analyzed and studied.The theoretical basis of OFDM technology is introduced in the paper,and the history of OFDM technology,modulation and demodulation methods,the common issues such as the equalization and peak to average ratio are described.Moreover,the combination of OFDM with spread spectrum technology and the advantages are analyzedIn order to suppress the frequency selective fading,the frequency domain equalization technology is introduced in the paper,and the performance the system based on frequency domain equalization technology is analyzed.The frequency selective fading in the channel is suppressed effectively.In order to improve the anti-jamming performance of the PLC communication system,the multi-carrier spread spectrum(MC-SS)system is introduced in the paper,which is combined OFDM with the spread spectrum technology.The system performances of MC-SS system under single frequency interference,impulse interference and frequency selective fading channel are studied.Meanwhile,in order to avoid the decline of the transmission rate of the system,the data parallel transmission is proposed.The orthogonality between spreading sequences is used to ensure the transmission rate and to avoid the interference between data parallel.Further,the space diversity technique is introduced into the multiple-input and multiple-output power line communication(MIMO-PLC)system based on the characteristic of the power line,and the anti-jamming performance of system using space-frequency block codes and space-time block codes is analyzed.The simulation results show that the space diversity technique can effectively resist frequency selective fading.