Monday, 20 October 2008

DVB-S2 The Next Generation Standard

As the technology is going ahead with a rocketing speed, India too is pacing with it and have shaken the world to get noticed. Due to rapid development most companies of the world are queuing up to please the Indian consumer as well raise the standard of life. And that is why, perhaps, more and more companies are introducing their upgraded products. Till now, most Indian companies had been using their S (satellite) technology, which specifies the use of QPSK modulation along with various tools for channel coding and error correction. 
The original DVB-S technology dates back to 1995 and was intended for delivery of broadcast services. In India, companies like TATA Sky, DISH TV, Sun Direct, BigTV, Doordarshan, each and every TV Channel, News Agencies and even data signals have been making use of this technology to provide satellite television to Indian masses. However, the introduction of the S2 technology by DVB is set to give Indian broadcasting a complete makeover. DVB-S2 is the second generation of the S-technology and comprises a variety of new features. DVB-S2 is based on the DVB-S standard which is used for satellite broadcasting, and the DVB-DSNG standard, which is used by mobile units for sending external footage back to television stations. 

This technology can not only be used for HDTV broadcasts, but this can also allow for the transportation of different multimedia streams such as, for example, Internet traffic, audio and video streaming and file transfers. In fact, DVB-S2 can achieve a capacity increase of 30% under the same transmission conditions compared to the older DVB-S standard. When the contribution of improvements in video compression is added, an (MPEG-4 AVC) HDTV service can now be delivered in the same capacity that supported an early DVB-S-MPEG-2 SDTV service, only a decade ago. The new technology can also be used for professional applications, where data must be multiplexed in real time and then broadcast in the VHF/UHF band.
These transmissions are not intended for the average viewer. To understand this complexity see the table below:
An efficient exploitation of the expensive satellite capacity has always been a key factor in the development of the satellite market, and the
improvements brought by DVB-S2 give promising perspectives for the future of satellite communications. The system allows transmission of one or more MPEG-2 audio/video streams , using QPSK or 8PSK or MAPSK (M-ary amplitude and phase shift keying) modulation with concatenated encoding. DVB-S2 benefits from more recent developments and has the following key technical characteristics:
This technology can not only be used for HDTV broadcasts, but this can also allow for the transportation of different multimedia streams such as, for example, Internet traffic, audio and video streaming and file transfers. In fact, DVB-S2 can achieve a capacity increase of 30% under the same transmission conditions compared to the older DVB-S standard.
 Modulation Modes – there are four modes available, with QPSK and 8PSK intended for broadcast applications in non-linear satellite transponders driven close to saturation. 16APSK and 32APSK, requiring a higher level of C/N, are mainly targeted at professional applications such as news gathering and interactive services.
 Forward Error Correction – DVB-S2 uses a very powerful forward error correction scheme (FEC), a key factor in allowing the achievement of excellent performance in the presence of high levels of noise and interference. The FEC system is based on concatenation of BCH (Bose-Chaudhuri-Hocquengham) with LDPC (Low Density Parity Check) inner coding.
 Adaptive Coding and Modulation (ACM) – allows the transmission parameters to be changed on a frame by frame basis depending on the particular conditions of the delivery path for each individual user. It is mainly targeted to unicasting interactive services and to point-to-point professional applications.
 Backwards Compatibility – DVB-S2 offers optional backwards compatible modes that use hierarchical modulation to allow legacy DVB-S receivers to continue to operate, whilst providing additional capacity and services to newer, more advanced receivers. 
DVB-S2 delivers excellent performance, the theoretical maximum information transfer rate in a channel for a given noise level. It can operate at carrier-to-noise ratios from -2dB (i.e., below the noise floor) with QPSK, through to +16dB using 32APSK. Today DVB-S2 links offer to the higher-layers protocols a terrestrial-like transmission medium, with recommended PERs around 10-7. This is of course an excellent result, but not all services at higher layers require to reach such outstanding performance. This is in particular true for Internet and multimedia services. However, DVB-S2 will not replace DVB-S in the short or even the medium term, but makes possible the delivery of services that could never have been delivered using DVB-S, and does so with a performance level that ensures that we won't see a "DVB-S3" for a very long time. 
In the Indian context, the process of conversion from DVB-S technology to DVB-S2 has already begun. Already NIC, the content developer of the government's websites, has started making use of this technology. DVB-S2 has already found a few takers in the form of Bharti Telemedia, which is soon to launch its DTH service and will make use of this technology. Videocon too has got itself enlisted for this technology for its soon-to-be-launched DTH service. Moreover, the current users in the form of TATA Sky and Dish TV have begun to upgrade their DVB-S to the S2 version. Moreover, the set-top boxes which boast of this technology are cheaper, which adds another feather in the technology's already full cap. With over a 50% price premium, the use of DVB-S2 set top boxes in standard definition DTH can outweigh savings in satellite capacity, particularly when targeting millions of consumers. A highly targeted DTH system destined to a relatively small group of consumers can benefit from the savings in capacity by adopting DVB-S2 set tops.
Developments in the MPEG-4 and DVB-S2 ecosystem have been greatly influenced by HDTV and the leading role taken by established DTH players such as DirecTV, BskyB, Premiere and EchoStar. It could now be in the hands of operators like Videocon and Bharti Telemedia in India to lead a similar process for the adoption of advanced technologies for standard definition DTH, a situation that could act as catalyst for MPEG-4 and DVB-S2 in other emerging markets. Also to pace with DVB-S2 satellite meter, Maxpeak is launching its DVB-S2 SAM-Plus meter in India which will make the job of installer much easier. An age of revolution in the way India views its television has already begun.

Source:
http://cablequest.org/articles/technical/item/1329-dvb-s2-the-next-generation-standard.htmlSource: http://cablequest.org/articles/technical/item/1329-dvb-s2-the-next-generation-standard.html

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