DVB-RCS Return Channel via SatelliteWhile IP traffic can be encapsulated into a MPEG-2 transport stream which enables receiving one-way DVB (Digital Video Broadcasting) broadband services via satellite, traditionally a slow terrestrial telephone link between the user and Internet service provider was used to request data. Due to the recognized need for the specification of a return channel via satellite, the Technical Module of the DVB project created an Ad-hoc group early 1999, called the DVB-RCS (DVB- Return Channel via Satellite).
A two-way exchange of data requires two transmission paths: the forward channel from a centralized hub location (RCS-Gateway) to the user terminal (RCS Terminal), and a return channel from the user terminal to the central hub. The DVB-RCS return channel system underwent final standardization by ETSI in early 2000.
The standard calls for a forward link based on DVB/MPEG-2 data format carrying up to 45 Mbps of traffic and a return link of up to 2 Mbps using a Multiple Frequency Time Division Multiple Access (MF-TDMA) scheme. The DVB-RCS physical layer contains specification of time slots and frames organized in super-frames. The return channel offers dynamically scheduled contention-less bandwidth via a satellite link to the hub station.
All user PCs behind the RCS Terminal (RCST) may have either public IP addresses (known to the Internet) or private IP addresses (used only within the satellite network). To facilitate interfacing with the Internet, private Internet addresses are mapped to a public registered IP address using a network address translator (NAT) at the hub station. Where an ISP is sending an IP packet to a host (with a private IP address) it uses a public address for the Internet portion, which is translated at the central hub.
DVB-RCS allows for cost efficient broadband satellite transmit and receive links. As such, DVB-RCS networks can build the platform for high-speed networks supporting all kinds of broadband services available on the Internet, such as broadband web-access, web TV, streaming video etc. DVB-RCS systems are scalable. A simple, single-gateway DVB-RCS system might serve up to thousands of users, whilst a distributed gateway architecture DVB-RCS system might provide integrated services to several hundred thousand users.
For DVB-RCS to become a global satellite standard, with interoperability of terminals from different vendors, further standardization efforts are needed. Currently, the standard only defines the link and physical layers (OSI layers 1 & 2) but does not specify the equally important processing at upper layers, like network management, TCP acceleration, HTTP pre-fetching, routing, data compression, Quality of Service (QoS), encryption.
As a result, all current DVB-RCS networks have to use terminals originating from the vendor of the DVB-RCS hub station.
LinkStar: Outdoor unit
The ODU consists of an antenna (90cm, 1.2m, 1.8m or 2.4m) and an RF power amplifier and low noise receiver
LinkStar: Indoor Unit
The IDU is an integrated unit. The MPEG-2 stream is recovered from the outbound signal by an integrated circuit consisting of a DVB demodulator and demultiplexer
2way2sat@night Service for Sub-Sahara Africa
Get a high quality Internet access at night for very little. No volume limitation, all Internet protocols supported.