| List of digital television broadcast standards |
| DVB standards (Europe) |
| DVB-S (satellite) |
| DVB-T (terrestrial) |
| DVB-C (cable) |
DVB-H (handheld)
|
| ATSC standards (North America/Korea) |
| ATSC (terrestrial/cable) |
| ATSC-M/H (mobile/handheld) |
| ISDB standards (Japan/Latin America) |
| ISDB-S (satellite) |
| ISDB-T (terrestrial) |
| ISDB-C (cable) |
| SBTVD/ISDB-Tb (Brazil) |
| DTMB standards (China) |
| DTMB-T/H (terrestrial/handheld) |
| CMMB (handheld) |
| DMB standards (Korean handheld) |
| T-DMB (terrestrial) |
| S-DMB (satellite) |
| MediaFLO |
| Codecs |
| Video |
| Audio |
| Frequency bands |
| VHF |
| UHF |
| SHF |
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.
Contents |
DVB-C 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.
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.
| DVB-C | DVB-C2 | |
|---|---|---|
| Input Interface | Single Transport Stream (TS) |
Multiple Transport Stream and Generic Stream Encapsulation (GSE) |
| Modes | Constant coding and modulation |
Variable Coding & Modulation and Adaptive Coding & Modulation |
| FEC | [[Reed-Solomon error correcion|Reed Solomon (RS)]] |
LDPC + BCH |
| Interleaving | Bit-Interleaving |
Bit- Time- and Frequency-Interleaving |
| Modulation | Single Carrier QAM |
COFDM |
| Pilots | NO |
Scattered and Continual Pilots |
| Guard Interval | NO |
1/64 or 1/128 |
| Modulation Schemes | 16 to 256-QAM |
16 to 4096-QAM |
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 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 channel.
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)
The mode adaptation modules, which operate separately on the contents of each PLP, 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 provides:
This sub-system shall perform outer coding (BCH), 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 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
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.
The function of the frame builder is to assemble the cells of the Preamble Symbols(s) as well as the cells produced for each of the Data Slices into arrays of active OFDM Cells corresponding to the preamble structure and each of the Data Slices and OFDM Symbols which make up the overall frame structure. The frame builder operates according to the dynamic information produced by the scheduler and the configuration of the frame structure.
The function of the OFDM generation module is to take the cells produced by the frame builder, as frequency domain coefficients and to transform them into the frequency domain.