Timing Synchronization Based On The Gardner Algorithm Research

The purpose of timing synchronization in digital communications is to get the correct start and end of every symbol at the receiver. Timing synchronization is the fundamental issue of all synchronization problems in digital communications. We can't get the digital messages that are transmitted without timing synchronization. Timing recovery consists of two distinct operations:estimation of the timing phase; application of the estimate to the sampling process. The former is referred to as timing measurement, the latter as timing correction. Timing correction serves to provide the decision device with signal samples with minimum intersymbol interference.The main research work of this thesis includes:we study the basic theory of timing adjustment by interpolation under the circumstance that sampling is not locked to the incoming data. Then we make some efforts to discuss the timing recovery scheme which is composed of interpolator, timing error detector, loop filter and numerically controlled oscillator and do the simulation of the scheme. The estimation of the timing parameter with the maximum likelihood method is discussed and we reasoned out the timing error detector algorithm based on the maximum likelihood estimation. Compared with the maximum likelihood timing error detector, the Gardner timing error detector has a better performance with a smaller timing variance. A digital prefilter is proposed in the thesis. By comparing the timing jitter and error rates of the timing recovery scheme with the prefilter and the condition without the prefilter, we concluded that the digital prefilter can be used to eliminate the timing variance and reduce error rates.