Design Of OFDM For LPLC In Frequency And Time Selective Fading Channel

Power Line Carrier Communication is a kind of wired communication mode,which exchange data between network nodes based on power line network as transmission channel.By far,power line carrier communication draws a lot of attention for its widely coverage power line grid,maturely cabling infrastructure and low cost.Power line carrier communication has been a powerful candidate of the next generation communication.However,as a communication channel of power transmission,the power lines transfer in a harsh environment,and also have the characteristics of strong signal attenuation,complex type of noise,frequency-selective fading characteristic,time-selective fading and strong time-varying characteristic.In this thesis,the knowledge of the power line channel in relevant literature were analyzed and researched.We build the math model for power line channel,using the model to show the frequency-selective fading and time-selective fading characteristics in PLC channel,and to provide a stable,controllable channel environment,make it convenient to test and compare the result of the PLC communication system.We adopted the Orthogonal Frequency Division Multiplexing(OFDM)technology,combining with anti-fading encoding method,channel estimation,error correcting code and interleaving coding in the system,for OFDM have the characteristic of anti-frequency selective fading,and error correcting code can help to correct the error caused by the noise,also interleaving coding have the characteristic of anti-time selective fading.With the design base on that,it would be helpful to improve the ability of anti-jamming,anti-frequency selection,anti-time selective fading,and improve the reliability of the transmission system.We used MATLAB software to model and simulated the communication system,including the module of channel coding,OFDM modulation,interleaving,encoding,channel environment,channel estimation,de-interleaving,OFDM demodulation and channel decoding.Considering the simulation results and the hardware capabilities,we chose convolution code as our channel coding method and Viterbi hard decision decode as our channel decoding,used matrix interleaving to interleave the data,and set up proper parameters for OFDM modulation to improve the reliability of Power Line Carrier Communication.Based on the simulation system,the Power Line Carrier Communication system used the TI's DSP chip TMS320F2812.We built the communication system implementation model by the toolbox of MATLAB.There is an auto-generation of DSP code on the operating platform in Simulink,by setting the interface on MATLAB and DSP target board,then linking the codes,loading and running them on the DSP target board by CCS software.Through the analysis of the theory data and measured date,the power line carrier communication system could effectively improve the ability of anti-jamming,anti-frequency selective and time selective fading by taking the advantage of joint OFDM technology and error control method.It has a significant reference for the study of power line carrier communication.