DVB-C2
Encyclopedia
DVB-C2 is a digital cable transmission system developed by the DVB
Project. It uses the latest modulation and coding techniques to enable highly efficient use of cable networks where, up to now, in many cases downstream transmission capacity is already being used to its limit. DVB-C2 will initially be used for the delivery of innovative new services, such as video-on-demand (VOD
) and high definition television (HDTV), helping digital operators to remain competitive and also to meet retransmission requirements; in the longer term the migration of current DVB-C
services to DVB-C2 is also foreseen.
was first published by ETSI in December 1994, subsequently becoming the most widely used transmission system for digital cable television. The standard is deployed worldwide in systems ranging from the larger cable television networks (CATV) down to smaller satellite master antenna TV (SMATV) systems.
A range of factors have combined to create the demand for DVB
to create a second generation cable transmission standard, as has been the case with DVB-S2
and DVB-T2
for satellite and terrestrial transmission.
As with all DVB
standards, the specification is based on a set of Commercial Requirements. Key requirements include an increase in capacity (at least 30%), support of different input protocols, and improved error performance. DVB-C2
reuses some of the building blocks of other second generation DVB
transmission systems - the “DVB Family” approach. The new standard was not required to be backwards compatible with DVB-C
, although DVB-C2 receivers will be able to also handle DVB-C
services.
April 2010 saw the publication of the DVB-C2 specification (EN302769. An updated version is already available as DVB BlueBook A138 and the Implementation Guidelines Document (DVB BlueBook A147). In the same month, the Technical University of Braunschweig performed the first live DVB-C2 transmission, which validated the strong expected performance boost of the new system.
The first DVB-C2 tuners are expected mid-2011.
By using state of the art coding and modulation techniques it offers greater than 30% higher spectrum efficiency under the same conditions as today’s DVB-C
deployments. After analogue switch-off the gains in downstream capacity will be greater than 60% for optimized HFC networks.
The system output is a single signal to be transmitted on a single RF
channel.
, slice the input data stream into data fields which, after stream adaptation, will form baseband frames (BBFrame).
The mode adaptation module comprises the input interface, followed by three optional sub-systems (the input stream synchronizer, the Null Packet deletion unit and the CRC-8 encoder) and then finishes by slicing the incoming data stream into data fields and inserting the baseband header (BBHeader) at the start of each data field.
), inner coding (LDPC
) and bit interleaving. The input stream shall be composed of BBFrames and the output stream of FECFrames. Finally, the LDPC output, go through a bit interleaver.
The number of sub-streams depends on the modulation (QPSK, 16QAM, 64QAM, 256QAM, 1024QAM, 4096QAM).
These sub-streams are split into two parallel cell words. Each cell word from the demultiplexer shall be modulated using either QPSK, 16QAM, 64QAM, 256QAM, 1024QAM, 4096QAM
The Data Slice Packets for Data Slice Type 1 only transmit the FECFrame data and rely on a pointer within the Level 1 Signaling Part 2 to detect their start.
The Data Slice Packets for Data Slice Type 2 carry a FECFrame header that allows for synchronization to the Data Slice Packets without any additional information.
DVB
Digital Video Broadcasting is a suite of internationally accepted open standards for digital television. DVB standards are maintained by the , an international industry consortium with more than 270 members, and they are published by a Joint Technical Committee of European Telecommunications...
Project. It uses the latest modulation and coding techniques to enable highly efficient use of cable networks where, up to now, in many cases downstream transmission capacity is already being used to its limit. DVB-C2 will initially be used for the delivery of innovative new services, such as video-on-demand (VOD
Video on demand
Video on Demand or Audio and Video On Demand are systems which allow users to select and watch/listen to video or audio content on demand...
) and high definition television (HDTV), helping digital operators to remain competitive and also to meet retransmission requirements; in the longer term the migration of current DVB-C
DVB-C
DVB-C stands for Digital Video Broadcasting - Cable and it is the DVB European consortium standard for the broadcast transmission of digital television over cable...
services to DVB-C2 is also foreseen.
History
DVB-CDVB-C
DVB-C stands for Digital Video Broadcasting - Cable and it is the DVB European consortium standard for the broadcast transmission of digital television over cable...
was first published by ETSI in December 1994, subsequently becoming the most widely used transmission system for digital cable television. The standard is deployed worldwide in systems ranging from the larger cable television networks (CATV) down to smaller satellite master antenna TV (SMATV) systems.
A range of factors have combined to create the demand for DVB
DVB
Digital Video Broadcasting is a suite of internationally accepted open standards for digital television. DVB standards are maintained by the , an international industry consortium with more than 270 members, and they are published by a Joint Technical Committee of European Telecommunications...
to create a second generation cable transmission standard, as has been the case with DVB-S2
DVB-S2
Digital Video Broadcasting - Satellite - Second Generation is a digital television broadcast standard that has been designed as a successor for the popular DVB-S system. It was developed in 2003 by the , an international industry consortium, and ratified by ETSI in March 2005...
and DVB-T2
DVB-T2
DVB-T2 is an abbreviation for Digital Video Broadcasting – Second Generation Terrestrial; it is the extension of the television standard DVB-T, issued by the consortium DVB, devised for the broadcast transmission of digital terrestrial television....
for satellite and terrestrial transmission.
- Many CATV networks are already full to capacity.
- Operators with high digital penetration need the flexibility to keep their offering competitive
- CATV networks retransmitting content from other networks, e.g. satellite, must keep pace with their evolution
- New tools are needed to address both private and business customers, particularly with IP-based content
- Performance improvements, e.g. zapping time, are needed to increase digital penetration in some markets
As with all DVB
DVB
Digital Video Broadcasting is a suite of internationally accepted open standards for digital television. DVB standards are maintained by the , an international industry consortium with more than 270 members, and they are published by a Joint Technical Committee of European Telecommunications...
standards, the specification is based on a set of Commercial Requirements. Key requirements include an increase in capacity (at least 30%), support of different input protocols, and improved error performance. DVB-C2
DVB-C2
DVB-C2 is a digital cable transmission system developed by the DVB Project. It uses the latest modulation and coding techniques to enable highly efficient use of cable networks where, up to now, in many cases downstream transmission capacity is already being used to its limit...
reuses some of the building blocks of other second generation DVB
DVB
Digital Video Broadcasting is a suite of internationally accepted open standards for digital television. DVB standards are maintained by the , an international industry consortium with more than 270 members, and they are published by a Joint Technical Committee of European Telecommunications...
transmission systems - the “DVB Family” approach. The new standard was not required to be backwards compatible with DVB-C
DVB-C
DVB-C stands for Digital Video Broadcasting - Cable and it is the DVB European consortium standard for the broadcast transmission of digital television over cable...
, although DVB-C2 receivers will be able to also handle DVB-C
DVB-C
DVB-C stands for Digital Video Broadcasting - Cable and it is the DVB European consortium standard for the broadcast transmission of digital television over cable...
services.
April 2010 saw the publication of the DVB-C2 specification (EN302769. An updated version is already available as DVB BlueBook A138 and the Implementation Guidelines Document (DVB BlueBook A147). In the same month, the Technical University of Braunschweig performed the first live DVB-C2 transmission, which validated the strong expected performance boost of the new system.
The first DVB-C2 tuners are expected mid-2011.
System differences with DVB-C
As with its predecessor, DVB-C2 offers a range of modes and options that can be optimised for the different network characteristics and the requirements of the different services planned for delivery to cable customers.Table comparing available modes and features in DVB-C and DVB-C2
| DVB-C | DVB-C2 | |
|---|---|---|
| Input Interface | | |
| Modes | | |
| FEC Forward error correction In telecommunication, information theory, and coding theory, forward error correction or channel coding is a technique used for controlling errors in data transmission over unreliable or noisy communication channels.... | | |
| Interleaving Interleaving In computer science and telecommunication, interleaving is a way to arrange data in a non-contiguous way to increase performance.It is typically used:* In error-correction coding, particularly within data transmission, disk storage, and computer memory.... | | |
| Modulation Modulation In electronics and telecommunications, modulation is the process of varying one or more properties of a high-frequency periodic waveform, called the carrier signal, with a modulating signal which typically contains information to be transmitted... | | |
| Pilots | | |
| Guard Interval Guard interval In telecommunications, guard intervals are used to ensure that distinct transmissions do not interfere with one another. These transmissions may belong to different users or to the same user .... | | |
| Modulation Schemes | | |
By using state of the art coding and modulation techniques it offers greater than 30% higher spectrum efficiency under the same conditions as today’s DVB-C
DVB-C
DVB-C stands for Digital Video Broadcasting - Cable and it is the DVB European consortium standard for the broadcast transmission of digital television over cable...
deployments. After analogue switch-off the gains in downstream capacity will be greater than 60% for optimized HFC networks.
DVB-C2 system overview
The generic C2 System model is represented in figure 1. The system input(s) may be one or more MPEG-2 Transport Stream(s) and/or one or more Generic Stream(s). The Input pre-processor, which is not part of the C2 System, may include a service splitter or a demultiplexer for Transport Streams (TS) used to separate the services into the C2 System inputs, which are one or more logical data streams. These are then carried in individual Physical Layer Pipes (PLPs).The system output is a single signal to be transmitted on a single RF
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
channel.
DVB-C2 system architecture
Input pre-processor
Physical Layer Pipe (PLP) creation: adaptation of Transport Stream (TS), Generic Stream Encapsulation (GSE), Generic Continuous Stream (GCS), or Generic Fixed-length Packetized Stream (GFPS)Mode adaptation
The mode adaptation modules, which operate separately on the contents of each PLPPLP
PLP may stand for:*Personalized Learning Programme*Packet Layer Protocol, a network layer protocol*Partner Login Portal, a partner facing web portal*Pamantasan ng Lungsod ng Pasig, a local university in Pasig City, Philippines...
, slice the input data stream into data fields which, after stream adaptation, will form baseband frames (BBFrame).
The mode adaptation module comprises the input interface, followed by three optional sub-systems (the input stream synchronizer, the Null Packet deletion unit and the CRC-8 encoder) and then finishes by slicing the incoming data stream into data fields and inserting the baseband header (BBHeader) at the start of each data field.
Stream adaptation
Stream adaptation provides:- Scheduling: The scheduler shall decide together with the Data Slice builder which Data Slices of the final C2 System will carry data belonging to which PLPs
- Padding: Padding may be applied in circumstances when the user data available for transmission is not sufficient to completely fill a BBFrame, or when an integer number of UPs has to be allocated in a BBFrame.
- BB Scrambling: The complete BBFrame shall be randomized. The randomization sequence shall be synchronous with the BBFrame, starting from the MSB and ending after Kbch bits.
FEC encoding
This sub-system shall perform outer coding (BCHBCH code
In coding theory the BCH codes form a class of parameterised error-correcting codes which have been the subject of much academic attention in the last fifty years. BCH codes were invented in 1959 by Hocquenghem, and independently in 1960 by Bose and Ray-Chaudhuri...
), inner coding (LDPC
Low-density parity-check code
In information theory, a low-density parity-check code is a linear error correcting code, a method of transmitting a message over a noisy transmission channel, and is constructed using a sparse bipartite graph...
) and bit interleaving. The input stream shall be composed of BBFrames and the output stream of FECFrames. Finally, the LDPC output, go through a bit interleaver.
Mapping bits onto constellations
The bit-stream from the bit interleaver is demultiplexed into N sub-streams.The number of sub-streams depends on the modulation (QPSK, 16QAM, 64QAM, 256QAM, 1024QAM, 4096QAM).
These sub-streams are split into two parallel cell words. Each cell word from the demultiplexer shall be modulated using either QPSK, 16QAM, 64QAM, 256QAM, 1024QAM, 4096QAM
Data Slice Packets Generation
The complex cells of one or two FECFrame shall form a Data Slice Packet.The Data Slice Packets for Data Slice Type 1 only transmit the FECFrame data and rely on a pointer within the Level 1 Signaling Part 2 to detect their start.
The Data Slice Packets for Data Slice Type 2 carry a FECFrame header that allows for synchronization to the Data Slice Packets without any additional information.