DVB-RCS

DVB-RCS is an acronym for Digital Video Broadcasting - Return Channel via Satellite or (Return channel over system). It is a specification for an interactive on-demand multimedia satellite communication system formulated in 1999 by the DVB consortium.

The 5th revision of the DVB-RCS standard was completed in 2008. A major update included the very first broadband mobile standardization. This extended version, formally referred to as "ETSI EN 301 790 v 1.5.1" is also known as "DVB-RCS+M". The "+M" version added several new features, such as the ability to use "DVB-S2" bursts in the uplink channel back to the satellite. It incorporated signal fade mitigation techniques and other solutions to combat short term signal loss.

In contrast to other satellite communications systems, DVB-RCS was created in an open environment where any DVB member can participate. DVB membership is open to all companies willing to subscribe. The work group called "DVB TM-RCS" is currently pursuing other technical solutions for the approved commercial system.

In 2009 technical work started for a new version of DVB-RCS called "DVB-RCS NG" (Next Generation). In this more powerful version of the standard "RCS2" there will be support for Higher Layers for Satellite (HLS) communication.

In older systems, interactive video broadcasting was possible as a result of using physical cables for connectivity. However, in remote areas cable connections may be unavailable, two-way communication was then impossible via traditional means. One possible solution was to use a satellite linked connection for the return (uplink) channel in addition to the standard downlink channel. This option is more expensive to implement than with cabled connections in built-up areas, but may be more cost effective for remote areas where the costs of laying cable to users would not be recovered for a long time. Additional costs involved in RCS systems include the costs of a two-way satellite antenna and renting data bandwidth from a satellite communications provider.

DVB-RCS is a mature open source satellite communication standard with highly efficient bandwidth management. This make it a cost-efficient alternative solution for many users. It also provides an established foundation for further satellite communications research.

To implement this kind of communication, a user will require a device called a "SIT", ("Satellite Interactive Terminal", "astromodem" or Satellite modem). A suitable satellite-dish is also required. Some systems are supplied as a pre-built combination. The user receives multimedia stream transmissions via the downlink-signals from the satellite. The user sends requests for service signals via the "SIT" and the uplink channel to the satellite. Upon receipt of the command from the user the satellite sends the user request data to the service provider. This takes about 0.5 seconds to connect each way with the satellite. (1 second total for satellite up and downlinks, and another second to the service provider and back, a total of 2 seconds Round-trip delay time).

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