Oare cand si in Romania ?
In March 2006 DVB decided to study options for an upgraded DVB-T standard. In June 2006, a formal study group named TM-T2 (Technical Module on Next Generation DVB-T) was established by the DVB Group to develop an advanced modulation scheme that could be adopted by a second generation digital terrestrial television standard, to be named DVB-T2.
According to the commercial requirements and call for technologies issued in April 2007, the first phase of DVB-T2 will be devoted to provide optimum reception for stationary (fixed) and portable receivers (i.e., units which can be nomadic, but not fully mobile) using existing aerials, whereas a second and third phase will study methods to deliver higher payloads (with new aerials) and the mobile reception issue. The novel system should provide a minimum 30% increase in payload, under similar channel conditions already used for DVB-T. Expected technologies will probably include:
LDPC/BCH codeforward error correction, in compliance with the technique already adopted in the DVB-S2 satellite standard, and other newer standards.
Optional use of MIMO and other antenna diversity system.
Improved methods for reducing peak power to the antenna (PAPR reduction).
More than 8k carriers. 16k and 32k carriers would minimize the overhead when single frequency networks are used. Present SFN networks are likely to see gains of 50% or more in net bit rate.
Improved channel estimation. Less overhead from fewer pilot carriers is likely.
30% larger distance between adjacent transmitters possible with SFN. Much larger SFN.
Variable coding and modulation.
Flexible multiplexing; several concurrent transport streams including Generic Stream Encapsulation for IP.
New DVB-T2 receivers are expected to be able to receive DVB-T, but DVB-T receivers will not receive DVB-T2 as hardware changes are needed. Firmware upgrades will not be enough.
It is expected that work on the DVB-T2 specification will be completed and passed to ETSI for standardization during 2008. First draft standard is expected by the end of June 2008. Market deployment is expected for 2009.
The BBC, ITV, Channel 4 and Five have agreed with the regulator Ofcom to convert one UK multiplex (B, or PSB3) to DVB-T2 to increase capacity for HDTV via DTT. They expect the first TV region to use the new standard will be Granada in November 2009 (with existing switched over regions being changed at the same time). It is expected that over time there will be enough DVB-T2 receivers sold to switch all DTT transmissions to DVB-T2, and MPEG-4 Part 10.
Ofcom recently published its final decision for HDTV using DVB-T2 and MPEG-4 : BBC-HD will have one HD slot from DSO at Granada and ITV, C4 and Five will compete for the two remaining HD slots from 2009 until 2012.
The DVB-T2 draft standard
From documents published on the Internet by RAI and others, the following characteristics are expected for the T2 standard.
Modulation will be standard COFDM in one of the modes QPSK, 16-QAM, 64-QAM, or 256-QAM (but not 128-QAM).
OFDM modes will be 1k, 2k, 4k, 8k, 16k and 32k. The symbol length for 32k mode will be about 4 ms.
Guard intervals will be 1/128, 1/32, 1/16, 19/256, 1/8, 19/128, and 1/4. (For 32k mode, the maximum is 1/8.)
FEC will be LDPC and BCH (as in DVB-S2), with rates 1/2, 3/5, 2/3, 3/4, 4/5, and 5/6.
There will be fewer pilots, in 8 different pilot-patterns, and equalization will be based also on the RAI CD3 system.
In the 32k mode, a larger part of the standard 8 Mhz channel can be used, adding about 2% extra capacity.
DVB-T2 will be specified for 1.7, 5, 6, 7, 8, and 10 MHz channel bandwidth.
MISO (Multiple-Inputs Single-Output) may be used (Alamouti scheme), but MIMO will not be used. Diversity receivers can be used (as they are with DVB-T).
Bundling of more channels into a SuperMUX (called TFS) is not in the standard, but may be added later.
An example for a UK MFN DVB-T profile (QAM64, 2k, CR2/3, GI1/32) and a DVB-T2 equivalent (QAM256, 32k, CR3/5, GI1/12 shows an increase in bit rate from 24.13 Mbit/s to 35.4 Mbps (+46.5%).
Another example is an Italian SFN DVB-T profile (QAM64, 8k, CR2/3, GI1/4) and a DVB-T2 equivalent (QAM256, 32k, CR3/5, GI1/16): it shows an increase in bit rate from 19.91 Mbit/s to 33.3 Mbps (+67%).
Status of the DVB-T2 specification (early April 200
The DVB-T2 physical layer specification is complete and there will be no further technical enhancements.
The receiver VLSI chip design can be started with confidence in stability of specification (the DVB internal standard document is available to all DVB members including the leading chip companies)
Draft PSI/SI (program and system information) specification document agreed with the DVB-TM-GBS group.
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