Research On Timing Synchronizationalgorithm Based On All-digital Receiver In Satellite Communication

With the rapid development of science and technology, satellite communicationtechnology with its large message capacity and transmission distance has become animportant means of modern communication. And that has a broad application prospectin emergency communication, military communication, civilian communication, and soon. However, signal’s frequency offset and independence of local clock andtransmitter’s clock may affect the best sampling in all-digital receiver, such as to causethe bit error rate’s deterioration of whole system. In other words, good synchronizationsystem is very important to implement the follow-up signal’s accurate demodulation forany digital communication. Therefore, timing synchronization plays an important role insatellite communication. So how to realize accurate timing in synchronization systemhas become a research hotspot.At present, scholars have carried out lots of research work in timingsynchronization. But existing timing synchronization algorithms usually considersynchronous speed or system self-noise only, without jointly considering the influenceof them on synchronization performance. Meanwhile, carrier frequency offset caused bysignal’s propagation also is ignored. So enhanced Gardner timing error detectionalgorithm (Evolved Gardner, E-Gardner) and anti carrier deviation’s Gardner timingerror detection algorithm (Anti Carrier Gardner, AC-Gardner) are proposed. The formeruses the median method and symbolic function to reduce pattern jitter and eliminatesystem self-noise respectively according to the polarity changes of two adjacentsymbols. The latter has found carrier frequency offset has cyclical impact on clock error.In view of this, the carrier frequency offset is moved to minimum periodic intervalhaving minimal influence on clock error.In addition, emergency data’s transmission is usually millisecond or second perframe in OFDM (Orthogonal Frequency Division Multiplexing) system. If the arrivaltime of received data frame can’t be detected accurately, the whole frame may be lost.To solve above problem, some existing algorithms just consider the preamble’s structure,but don’t availably combine it with frame synchronization and symbol synchronization.Therefore, a combined detecting synchronization OFDM-based preamble algorithm(Combined Detecting Synchronization OFDM-based Preamble, CDSOP) is presented.This algorithm firstly uses good autocorrelation characteristic to improve preamble, and then roughly estimates the preamble position of data frame with coarse timing. Finally,fine timing on the basis of coarse timing is used to detect the useful part’s beginning ofreceived frames.E-Gardner algorithm, AC-Gardner algorithm and CDSOP algorithm’s simulationand performance analysis are completed by building simulation platform on thecomputer in this thesis. Simulation results show that the proposed algorithms comparedwith others not only can effectively eliminate the effects of carrier frequency offset, butalso can obviously improve the system’s performance under the given satellite channelenvironment, which realizes the accurate signal’s demodulation and achieve the goal ofthe timing synchronization.