DVB/SCPC IP TransmissionThe forward (downstream) channel takes advantage of the DVB (Digital Video Broadcasting) multiplex - a very high speed data stream containing data packets from a number of individual smaller data streams. The return channel (upstream) works on the basis of the more classical SCPC (Single Channel per Carrier).
In a DVB television service, data streams are the MPEG-2 compressed video and audio (together with control data) which make up the TV channel. However, DVB today also has the ability to carry IP - and hence any higher level standard using IP - at a very high speed.
DVB has been developed to include encapsulation techniques which allow the MPEG-2 data packets to carry IP traffic at the same multi-Megabit/sec speed as digital television. This allows both digital TV and Internet traffic to co-exist on the same system and be received by either DVB PC Cards or DVB set-top-boxes. The data gateway - or DVB encapsulator - acts as a bridge between the IP world and the DVB world. IP packets are encapsulated into MPEG-2 packets which are multiplexed with video and audio into MPEG transport streams and uplinked for transmission by satellite in DVB-S format.
The recipient''s DVB receiver or DVB PC card demodulates and reassembles into IP packets and identifies those addressed to the PC, disregarding the others. This is the main advantage of DVB/SCPC over more classical SCPC/SCPC systems: The DVB multiplex allows the dedicated bandwidth in the downstream (forward channel) to be shared among many terminals. The recreated original IP packets are viewed - via browser, media player, etc - just as any other IP stream: except a great deal faster! The ability to transmit the Internet Protocol (IP) over satellite using the DVB standard for digital TV offers a wide range of potential services from a single technology platform.
These applications include one-way and two-way services:
As millions of receivers already in use world-wide work according the DVB standard - the consumer equipment is both already available and consumer-priced.
When a return channel via satellite is required for two-way services, SCPC is the preferred choice. atrexx offers integrated DVB/SCPC terminals as well as highly performing hybrid solutions consisting of a professional DVB IP receiver, an SCPC modulator, and a IP router to combine both upstream and downstream traffic.
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