Research On Timing And Frequency Synchronization Algorithm For NG-DSL System

Internet information technology has penetrated into all aspects of people's daily life,especially the application of online education,consumer payment,video conference,leisure and entertainment is very extensive.With the increase of broadband users,the current domestic network speed is more and more difficult to meet the needs of the public.The next generation digital subscriber(NG-DSL,next generation digital subscriber Line)technology as a new type of high-speed access technology came into being in this situation.It makes full use of the characteristics of optical fiber that can carry out high-speed data transmission,realizes the transmission rate higher than 1Gbps,and makes the bandwidth break through 100 megabytes,greatly improving the network speed.Traditional DSL(digital subscriber line)is limited by technology,and can only complete the information transmission work with less data.Because of the introduction of high-level OFDM(orthogonal frequency division multiplexing)technology in the physical layer of NG-DSL,this technology is widely used in wired and wireless access networks,and in QAM(high carrier number and high orthogonal amplitude modulation Because of this,NG-DSL has a high dependence on signal synchronization technology compared with other access technologies.Symbol timing synchronization and sampling frequency synchronization are two important ways for NG-DSL system to realize efficient signal synchronization.In this paper,firstly,the mechanism of the above two synchronization methods to NG-DSL system is explained in detail.On the basis of in-depth analysis,two new synchronization algorithms are proposed tentatively,that is,the new symbol timing synchronization based on the minimum energy difference and the new sampling frequency fast synchronization based on the eager iteration.The simple operation mechanism of new symbol timing synchronization based on the minimum energy difference is as follows: first,timing coarse synchronization is carried out.When the approximate position of quasi minimum value is determined in this process,the method of variable step size search is needed;then timing fine synchronization is carried out.When the minimum value is determinedin this process,the search is continued on the basis of the previous process.The algorithm can find the timing position of the symbol quickly and reduce the complexity greatly.The latter captures the sampling frequency offset,and then corrects the acquisition value through iteration.After capture,the algorithm continues to execute,and completes the fine-tuning process of the estimated value according to the obtained tracking value.This paper also optimizes and perfects the new algorithm,sets the tracking threshold in the tracking process,and adjusts the estimation when the tracking value is greater than the threshold.The sampling frequency synchronization algorithm can use fewer symbols to converge to the actual value of the estimated value quickly.On the basis of improving the estimation correction method and the observation value fitting method,it achieves the effect of simplifying the calculation.The above two new algorithms have been tested by the anti truth experiment,which effectively realizes the characteristics of low complexity,fast synchronization and high precision of NG-DSL system.