Research On Power Line Communication Synchronization Technology

Power line communication(PLC) is a way of communication using power line as a medium for data transmission. The technology has been widely used by electric power company in the smart grid due to its unique advantage. However, due to the complexity of power line transmission environment and time-varying characteristics such as high noise, high attenuation factors, the data rate of power line communication is restricted and bit error rate increases.This paper focuses on the synchronization technology in PLC system for further research.First of all, this paper studies the power line channel characteristics and the simulation model of power line channel.is given in this paper. Then,this article analyzes several common power line carrier communication, and by combining their advantages and disadvantages and application environment, this paper chooses spread spectrum communication as power line carrier communication. Then this paper introduces the basic theory of spread spectrum communication and system structure. The frame head design scheme for power line spread spectrum system is introduced.Then, based on the study on the basis of direct spread spectrum communication synchronization theory, this paper proposes a novel timing synchronization algorithm based on Chirp signal. The main work and innovations are as follows:The traditional code synchronization technology in direct spread spectrum system is taking advantage of the good auto-correlation characteristic for PN sequences. Do the relation operation for the receiving signal and the local PN code, in order to find the right starting position. The disadvantages for this method is that the capturing time is too long and the capturing accuracy is not so high.By using the Chirp signal’s pulse compression feature, the pulse compression algorithm is researched. The algorithm uses Chirp signal as the training sequence, the receiving signal at the receiver goes through a matched filtering which can get a very sharp narrow pulse to gain synchronization.Then based on Chirp signal in Fractional Fourier Transform(FRFT), a synchronization algorithm is proposed. The FRFT of Chirp signal on the optimal fractional domain has the characteristic of "energy gathering".According to the "energy gathering" position offset, the timing synchronization is finished. The timing synchronization accuracy under the environment of zero frequency offset is high, otherwise the algorithm performance is reduced greatly.According to the ordinary FRFT method is affected by frequency offset, this paper puts forward the improved FRFT method. The new training sequence is designed using two head-tail Chirp signal as a frame head. This paper respectively does the optimal FRFT of received signal, two energy gathering position can be obtained. With the two energy gathering position offset,this paper can calculate the right position of the timing synchronization.The position has been eliminated the influence of the frequency deviation, and high precision for timing synchronization is acquired.Finally, this paper discusses the implementation of the improved algorithm on a DSP platform. This paper starts from the basic steps of the algorithm, introduces the reason for choosing TMS320C6455 development environment and then introduces the program flow of the improved algorithm. Finally, the performance of the algorithms is analyzed.