NET-SYNCHRONIZING DEVICE FOR MULTI-MEDIA SATELLITE COMMUNICATION SYSTEM

摘要

PURPOSE: A network synchronizing apparatus for a multimedia satellite communication system is provided to easily conform data transmission time between each set-top box by transmitting PCR data when a center station transmits a predetermined number of TS packets and synchronizing a data transmission timing signal by every set-top box through the same method when the set-top box receives the PCR data. CONSTITUTION: An ethernet interface(11) generates an IP packet on the basis of an ethernet frame inputted from an IP switch and outputs it. An input buffer(12) sequentially stores the IP packet data outputted through the ethernet interface(11). An IP packet controller(13) determines the type of the input data on the basis of a header of the IP packet data stored in the input buffer(12), controls a packet generation of a PS packet generator(15) and a TS packet generator(16) on the basis of the determining result, and controls a transmission data processing unit on the basis of a control data applied from the ethernet interface(11). A subscriber information storing unit(14) stores a PID allocated for each set-top box(4). The PS packet generator(15) generates a PS(Private Section) packet on the basis of the data inputted from the IP packet controller(13). The TS packet generator(16) generates an MPEG-2 TS packet on the basis of the PS packet data inputted from the PS packet generator(15), a PID applied from the IP packet controller(16) and traffic data stored in the input buffer(12) and outputs it. The TS packet generator(16) counts the number of the TS packets transmitted for the set-top box(4), reads a program clock reference(PCR) value applied from a PCR generator(18) when the count value is a predetermined value, and transmits it to the set-top box(4). A frequency generator(17) generates a 27MHz frequency signal. The PCR generator(18) counts the frequency signal outputted from the frequency generator(17) and outputs the count value data.