Research On Clock Recovery And Transport Stream Synchronization Based On Satellite Digital TV Time Service

This paper researches the Clock Recovery and Transport Sream synchronizationof broadcasting unit in the Satellite Digital TV Time Service System. The satellitedigital TV time service is based on the DVB-S. It provides time service by insertingtime message into digital TV channel. The high precise PCR time stamp is acquiredby time recovery and Transport Sream synchronization, which is inserted intochannel.The data rate of satellite digital TV is low, so more error will be emerged if thetime message is acquired directly by TS. The ephemeris is calculated by the timeinformation, so low data rata will cause error ephemeris, even wrong module chosen.The time delay is also calculated by the arrived PCR which have the same count value.So the higher the resolution of time recovery and data synchronization is, the lesserror of time delay will emerge. The research of time recovery and Transport Sreamsynchronization of broadcasting unit can improve the precision and reduce error rata.High precision PCR timestamp is insered into the satellite digital TV channel.The influence of insertion should be less. In the user section, the paper reseaches theaffection of insertion of time message by measuring channel parameters such as errorrate. So the testing and analysis in the user section can reduce the error ofbroadcasting path, improve the time service precision, proof the reliability ofinsertion.The main points of this thesis are as follows:(1) Analyse the signal structure including source coding and channel coding ofthe Satellite Digital TV system with DVB-S standard. Design the broadcasting unit ofthe whole time service system, and describe two main functions of high precisionPCR timestamp acquirement and timing message insertion in the subsystem.(2) Analyse the method of acquiring high precision PCR timestamp: clockrecovery and transport stream synchronization. According to the standard of signal insatellite digital TV, GS7025is chosen as the chip to recover transport stream.According the resource consumption of time receicer, Cyclone III EP3C16E144I7ischosen as the FPGA chip to synchronize data in transport stream and capturetimestamp. The peripheral electric circuit of GS7025chip and date&clock interface isshown in the paper, and the software modules which are designed for datasynchronization and timestamp acquirement are also shown in the paper based on the Quartus II.(3) System testing. Analyse the collected data about bit syschronization precision,insertion precision and signal interference. The conclusion is: there is no influence toeach other between the original video&audio signal and the timing message which isinserted into the channel.The purpose of this paper is to research the theory of transport streamsynchronization and high precision PCR timestamp acquirement by usingGS7025+FPGA chip, find the way of inserting timing information, analyse theinfluence between timing message and the original signals.