Digital Video Broadcasting - Cable (DVB-C) is the DVB European consortium standard for the broadcast transmission of

digital television Digital television (DTV) is the transmission of television signals using digital encoding, in contrast to the earlier analog television technology which used analog signals. At the time of its development it was considered an innovative advan ...

over cable. This system transmits an

MPEG-2 MPEG-2 (a.k.a. H.222/H.262 as was defined by the ITU) is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression metho ...

MPEG-4 MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related ...

family

digital audio Digital audio is a representation of sound recorded in, or converted into, digital form. In digital audio, the sound wave of the audio signal is typically encoded as numerical samples in a continuous sequence. For example, in CD audio, sam ...

digital video Digital video is an electronic representation of moving visual images ( video) in the form of encoded digital data. This is in contrast to analog video, which represents moving visual images in the form of analog signals. Digital video comprise ...

stream, using a QAM modulation with

channel coding In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea ...

. The standard was first published by the

ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the field of information and communications. ETSI supports the development and testing of global technical standard ...

in 1994, and subsequently became the most widely used transmission system for digital cable television in Europe, Asia and South America. It is deployed worldwide in systems ranging from the larger cable television networks (CATV) down to smaller satellite master antenna TV ( SMATV) systems.

Technical description

DVB-C transmitter

With reference to the figure, a short description of the single processing blocks follows. *

Source coding In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compression ...

and MPEG-2

multiplexing In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource - ...

(MUX): video, audio, and data streams are multiplexed into an

MPEG program stream Program stream (PS or MPEG-PS) is a container format for multiplexing digital audio, video and more. The PS format is specified in MPEG-1 Part 1 (ISO/IEC 11172-1) and MPEG-2 Part 1, Systems (ISO/IEC standard 13818-1/ITU-T H.222.0). The MPEG-2 Pr ...

(MPEG-PS). One or more MPEG-PSs are joined together into an

MPEG transport stream MPEG transport stream (MPEG-TS, MTS) or simply transport stream (TS) is a standard digital container format for transmission and storage of audio, video, and Program and System Information Protocol (PSIP) data. It is used in broadcast system ...

(MPEG-TS). This is the basic digital stream which is being transmitted and received by home set top boxes (STB) or relevant integrable decoder (e.g. Conax) module. Allowed

bit rate In telecommunications and computing, bit rate (bitrate or as a variable ''R'') is the number of bits that are conveyed or processed per unit of time. The bit rate is expressed in the unit bit per second (symbol: bit/s), often in conjunction w ...

s for the transported MPEG-2 depend on a number of modulation parameters: it can range from about 6 to about 64

Mbit/s In telecommunications, data-transfer rate is the average number of bits (bitrate), characters or symbols ( baudrate), or data blocks per unit time passing through a communication link in a data-transmission system. Common data rate units are mult ...

(see the bottom figure for a complete listing). * MUX adaptation and energy dispersal: the MPEG-TS is identified as a sequence of data packets, of fixed length (188 bytes). With a technique called energy dispersal, the byte sequence is decorrelated. * External encoder: a first level of protection is applied to the transmitted data, using a nonbinary

block code In coding theory, block codes are a large and important family of error-correcting codes that encode data in blocks. There is a vast number of examples for block codes, many of which have a wide range of practical applications. The abstract definit ...

, a Reed–Solomon RS (204, 188) code, allowing the correction of up to a maximum of 8 wrong bytes for each 188-byte packet. * External

interleaver In computing, telecommunication, information theory, and coding theory, an error correction code, sometimes error correcting code, (ECC) is used for controlling errors in data over unreliable or noisy communication channels. The central idea ...

: convolutional interleaving is used to rearrange the transmitted data sequence, such way it becomes more rugged to long sequences of errors. * Byte/m-tuple conversion: data bytes are encoded into bit ''m''-tuples (''m'' = 4, 5, 6, 7, or 8). * Differential coding: In order to get a rotation-invariant constellation, this unit shall apply a differential encoding of the two Most Significant Bits (MSBs) of each symbol. * QAM Mapper: the bit sequence is mapped into a base-band digital sequence of complex symbols. There are 5 allowed

modulation In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the ''carrier signal'', with a separate signal called the ''modulation signal'' that typically contains informatio ...

modes: 16- QAM, 32-QAM, 64-QAM, 128-QAM, 256-QAM. * Base-band shaping: the QAM signal is filtered with a raised-cosine shaped filter, in order to remove mutual signal interference at the receiving side. * DAC and front-end: the digital signal is transformed into an analog signal, with a

digital-to-analog converter In electronics, a digital-to-analog converter (DAC, D/A, D2A, or D-to-A) is a system that converts a digital signal into an analog signal. An analog-to-digital converter (ADC) performs the reverse function. There are several DAC archi ...

(DAC), and then modulated to

radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the uppe ...

by the RF front-end.

DVB-C receiver

The receiving STB adopts techniques which are dual to those ones used in the transmission. * Front-end and ADC: the analog RF signal is converted to base-band and transformed into a digital signal, using an

analog-to-digital converter In electronics, an analog-to-digital converter (ADC, A/D, or A-to-D) is a system that converts an analog signal, such as a sound picked up by a microphone or light entering a digital camera, into a digital signal. An ADC may also provid ...

(ADC). * QAM Demodulation * Equalization * Differential decoding * Outer interleaving * Outer decoding * MUX adaptation * MPEG-2 demultiplexing and source decoding * Programmable Transport Stream

DVB-C2

On February 18, 2008 it was announced that a new standard – DVB-C2 – would be developed during 2008, and a "Call for Technologies" was issued. Proposals including simulation programs and information on patent rights could be submitted until June 16, 2008. "The results of the DVB-C2 Study Mission already provided clear indications that technologies are available allowing the performance of the second generation DVB cable transmission system to get so close to the theoretical

Shannon Limit In information theory, the noisy-channel coding theorem (sometimes Shannon's theorem or Shannon's limit), establishes that for any given degree of noise contamination of a communication channel, it is possible to communicate discrete data (dig ...

that any further improvements in the future would most likely not be able to justify the introduction of a disruptive third generation of cable transmission system." (DVB-C2 CfT) By using state of the art coding and modulation techniques, DVB-C2 should offer greater than 30% higher spectrum efficiency under the same conditions, and the gains in downstream channel capacity will be greater than 60% for optimized HFC networks. The final DVB-C2 specification was approved by the DVB Steering Board in April 2009. DVB-C2 allows bit rates up to 83.1 Mbit/s on an 8 MHz channel bandwidth when using 4096-QAM modulation; future extensions will allow up to 97 Mbit/s and 110.8 Mbit/s per channel using 16384-QAM and 65536-AQAM modulation. Modes and features of DVB-C2 in comparison to DVB-C:

Countries that use DVB-C

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References

External links

Website of the DVB Project
*

Standard: ETSI EN 300 429 V1.2.1 (1998-04), ''Digital Video Broadcasting (DVB); Framing structure, channel coding and modulation for cable systems'', download fro
ETSI

Official factsheet of DVB-C2
{{Video formats Digital Video Broadcasting Television transmission standards