DVB return channel
The DVB Return Channel are a family of standards in digital television, which make the TV transmission paths return channel capable . This enables data transmission in both directions, from point to point. From a technical point of view, digital video broadcasting (DVB) describes the standardized methods for transmitting digital content such as television or radio . The abbreviations mean:
- DVB = Digital Video Broadcasting = digital television
- DVB-T = DVB Terrestrial = aerial television
- DVB-RCC = DVB Return Channel Cable
- DVB-RCS = DVB Return Channel Satellite
- DVB-RCT = DVB Return Channel Terrestrial.
DVB-RCC via cable
DVB-RCC is used by cable network operators to offer Internet access. The television cable network is basically suitable; frequencies below the VHF band are specified for the return channels, instead of the previous TV channels 2, 3 and 4 (48.25 MHz, 55.25 MHz and 62.25 MHz). Cable networks that transmit neither digital nor analog TV programs on these frequencies can thus offer Internet via cable connection.
DVB-RCS via satellite
DVB-RCS has been advertised by SES Global since 1999 and should have been in regular consumer use in 2003. In reality, DVB-RCS is not available from any provider, but it is an interesting technology for Internet connections with low requirements. Because of the enormous latency (ping round trip) of over 600 ms, many participants share a transponder and thus its max. 38 Mbit / s. With newer satellites there are controllable transponders with comparatively tiny footprints, so that the whole of Europe does not have to share the bandwidth of approx. 38 Mbit / s per transponder - as is common with internet via satellite. The return channel should reach up to 2 Mbit / s.
The abbreviation “-RCS” is often confused with “Return Channel System ”.
DVB-RCS2 via satellite version 2
In 2012, a second version of the DVB-RCS standard was adopted with improved error correction and higher types of modulation (QPSK, 8-PSK and 16-QAM). The changes are aimed at increased spectral efficiency and should enable operating costs to be reduced as well as higher data rates.
DVB-RCT terrestrial
The DVB-RCT was advertised through marketing during the introductory phase. Of course, DVB-T cannot make DSL or Internet - compatible cable connections superfluous. DVB-T only reproduces the analogue cable TV offer quite well in digital terrestrial format.
In order to be able to use terrestrially broadcast digital TV, DVB-T, for interactive distribution services such as teleshopping, telelearning and telebanking, this service is equipped with a return channel, the DVB-RCT. The modulation in the return channel works with Multiple Access OFDM (MA-OFDM) in the same frequency bands in which the downstream channels transmit the TV signals. The transmission can take place in radio cells with a diameter of up to 65 km, and with several kbit / s. The DVB-RCT can transmit power peaks with several thousand transactions per second. The transmission power for the return channel, which is provided by the user terminal or the set-top box, is 0.5 W.
No return channel frequencies are defined for DVB-RCT.
Other procedures
Rather, the return channel could be implemented via General Packet Radio Service , Universal Mobile Telecommunications System or via SMS for voting or competitions.
Based on satellite receivers ( DVB-S ), there is a proprietary product, Astras Blucom , in which the cell phone is connected via Bluetooth and displays additional information. In addition to the disadvantage of the small display, the mobile phone has the advantage that it also provides a return channel, which is implemented in the specific product via SMS or GPRS and incurs corresponding fees, which limits its suitability to certain services with a low response volume.
Multimedia Home Platform -based solutions with any desired, including DVB-based return channels are possible.