DVB T2W

A DVB terrestrial digital television transmission solution for
Australia, Canada, Mexico,
South Korea and New Zealand 



Abstract
DVB-T2 is in process of being developed as a terrestrial transmission system for the UK. However, as a DVB standard T2 has flaws and is limited in bandwidth. DVB-T2's maximal transmission bandwidth is 10 MHz, a mode that could not be used in Canada or anywhere where there are 6 MHz television channels.

With an effective bandwidth increase to 12 MHz, 16 MHz, 18 MHz or 24 MHz a better television transmission system can be created. The bandwidth increases must naturally be in multiples of either 6 MHz or 8 MHz. The 6 MHz or 8 MHz multiples are needed to be backwardly compatible with NTSC and PAL & SECAM bandwidth allocations.

The proposed wideband "DVB-T2W" system could be implemented in Australia, Canada-Mexico and New Zealand where it makes the most economic sense. DVB-T2W is not the same thing as DVB-T2 -- it is a more advanced transmission format.

Primary design goals (not in any specific order)
  1. Increase the number of channels in a Channel Group so one transmitter can serve an entire region on behalf of multiple broadcasters.
  2. Reduce RF channel planning complexity for regulators and broadcasters.
  3. Reduce RF transmitter output power by a factor of at least 20% vs DVB-T or DVB-T2.
  4. Reduce electromagnetic compatibility issues by avoiding some of DVB-T2's extremely high datarate transmission modes.
  5. Increase Doppler Immunity vs DVB-T2, but make it no worse than DVB-T high rate modes.
  6. Allow for open source CODECs to be used for both Audio and Video transmission.
  7. Create a transmission system that is 3D and 4k ready by default.
  8. Current DVB transmission systems do not support wavelet encoding in the Video CODECs. There must be support for wavelet encoding of reference images in the Video transmission subsystem so as to make the signal more robust.
  9. Currently DVB and ATSC are shackled with some CODEC components that have intellectual property issues. This must end.
  10. Turbocodes, and Punctured Turbocodes must be permitted for use in the Error Correction subsystem, as propagation conditions may evolve that will not work with the current DVB-T2 error correction subsystem.
  11. Allow mobile devices to still have access to TV service via older DVB (or ATSC) terrestrial transmitters.
  12. Allow for Digital Audio Broadcasting, at least nominally as DVB-T currently does.
All of these design goals can be met with increased bandwidth, and limited modifications to the DVB-T2 transmission system. The only possible major change that new video codecs will be required and the error correction system must have an alternate to the current Low Density Parity Check Codes + BCH currently implemented.



History matters : the role of NTSC, PAL-7 and PAL-8

PAL broadcast systems

This table illustrates the differences between the various PAL broadcast systems.
The rarer forms of PAL have been omitted from the table.

Signal Parameter
PAL B PAL G, H PAL I PAL D
Transmission Band VHF UHF UHF/VHF VHF
Lines / Fields 625/50 625/50 625/50 625/50
Video Bandwidth 5.0 MHz 5.0 MHz 5.5 MHz 6.0 MHz
Sound Carrier 5.5 MHz 5.5 MHz 6.0 MHz 6.5 MHz
Channel Bandwidth 7.0 MHz 8.0 MHz 8.0 MHz 8.0 MHz
Active lines 576i 576i 576i 576i

Implementation note
In the end these systems were decommissioned and replaced with DVB-T (Australia, NZ) and ATSC (Canada). However, this HDTV transmission system adoption is not without its flaws and its problems.


DVB-T and DVB-T2 History

Towards the end of 1991, broadcasters, equipment manufacturers and regulatory bodies in Europe came together to discuss the formation of a group that would oversee the introduction of digital TV. That group, which became known as the European Launching Group (ELG), realized that a consensus-based framework, through which all of the key stakeholders could agree on the appropriate technologies to be used, would benefit everybody involved.

A Memorandum of Understanding (MoU) was drawn up, setting out the basis on which competitors in the marketplace would come together in a spirit of trust and mutual respect. The MoU was signed in September 1993 by all ELG participants, and the DVB Project was born. A key report from the Working Group on Digital Television was also central to setting out important concepts that would go on to shape the introduction of digital TV in Europe and far beyond.

By any measure the DVB Project has been a success. More than 500 million devices around the world are receiving services that use DVB standards, including at least 100 million satellite receivers and at least 150 million DVB-T receivers. DVB-C is the most commonly used system for digital cable TV. DVB-T has seen phenomenal growth in the last few years with services on air across Europe and in parts of Asia, Africa and Latin America and many more countries that are planning deployment. The economies of scale engendered by such success mean that the prices consumers have to pay for receivers are falling all the time.

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 would be devoted to provide optimum reception for stationary (fixed) and portable receivers (units which can be nomadic, but not fully mobile) using existing aerials, whereas a second and third phase would 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.

The BBC, ITV, Channel 4 and Five agreed with the regulator OFCOM to convert one UK multiplex (B, or PSB3) to DVB-T2 to increase capacity for HDTV via DTT. They expected the first TV region to use the new standard would be Granada in November 2009 (with existing switched over regions being changed at the same time). It was expected that over time there would be enough DVB-T2 receivers sold to switch all DTT transmissions to DVB-T2, and H.264.



The current DVB-T2 specification

The DVB-T2 draft standard was ratified by the DVB Steering Board on June 26, 2008, and published on the DVB homepage as DVB-T2 standard Blue Book. The T3 specification was handed over to the European Telecommunications Standards Institute (ETSI) by DVB.ORG on June 20, 2008. The ETSI process resulted in the DVB-T2 standard being adopted on September 9, 2009.

The ETSI process had several phases, but the only changes were text clarifications. Since the DVB-T2 physical layer specification was complete, and there would be no further technical enhancements, receiver VLSI chip design started with confidence in stability of specification. A draft PSI/SI (program and system information) specification document was also agreed with the DVB-TM-GBS group.


DVB-T and DVB-T2 Compared
Bold text indicates changes added to the DVB base system
System
DVB-T DVB-T2
FEC Convolusional Coding + Reed Solomon 1/2, 2/3, 3/4, 5/6, 7/8 LDPC + BCH 1/2, 3/5, 2/3, 3/4, 4/5, 5/6
Modes QPSK, 16QAM, 64QAM QPSK, 16QAM, 64QAM, 256QAM
Guard Interval 1/4, 1/8, 1/16, 1/32 1/4, 19/256, 1/8, 19/128, 1/16, 1/32, 1/128
FFT size 2k, 8k 1k, 2k, 4k, 8k, 16k, 32k
Scattered Pilots 8% of total 1%, 2%, 4%, 8% of total
Continual Pilots 2.6% of total 0.35% of total


Now that the DVB system has been adequately presented, the main proposal for its modifications can be made.



DVB T2W Specification



Proposed DVB-T2W System

System characteristics



Notes





Original TV Bandwidth
8 MHz
7 MHz
6 MHz PAL, PAL-M, PAL-N, NTSC; 5 MHz PAL (VHF) not used





Proposed T2W Bandwidth (1)
24 MHz
21 MHz
24 MHz
(3 x 8, 3 x 7, 4 x 6)
Proposed T2W Bandwidth (2)
16 MHz
14 MHz
18 MHz
(2 x 8, 2 x 7, 3 x 6)
Proposed T2W Bandwidth (3)
= NA =
= NA =
12 MHz
(NA, NA, 2 x 6)





T2W Relative to T2




"Carrier Density"
~= DVB-T2 ~= DVB-T2 ~= DVB-T2 No change vs T2
"Number of Carriers"
~= DVB-T2
~= DVB-T2 ~= DVB-T2
No change vs T2
"Guard band"
~= DVB-T2 ~= DVB-T2 ~= DVB-T2 No change vs T2





Constellation deletions
256 QAM
256 QAM 256 QAM Cable TV Only
Constellation additions
32 QAM
32 QAM 32 QAM EM compatibility





DVB-T2W FFT sizes vs T2
No change
No change No change
EM compatibility
Guard intervals vs T2
No change
No change No change
EM compatibility





Continual pilots %
0.35, 0.70, 1.4
0.35, 0.70, 1.4
0.35, 0.70, 1.4
Propagation
Continual pilots % (added)
2.8
2.8 2.8 Propagation Fallback





Error Correction




FEC added to T2(W)
Turbo Codes
Turbo Codes
Turbo Codes (+Punctured) Fallback





Audio & Video CODECs




CODECs added (2D)
Dirac + Theora
Dirac + Theora
Dirac + Theora
Open Source CODECs





CODECs deleted (2D)
MPEG (2 & 4)
MPEG (2 & 4)
MPEG (2 & 4)
JPEG & AAC Core IP issues
CODECs added (3D) DVB-3D TV
DVB-3D TV
DVB-3D TV
CODECs added (3D) DVB-3D TV (Dirac)
DVB-3D TV (Dirac) DVB-3D TV (Dirac) Dirac 3D mode does not exist (2013)





Interlaced DTV Modes (deleted)
16:9 HD, ALL
16:9 HD, ALL 16:9 HD, ALL Dirac Progressive Modes only
Interlaced DTV Modes (SDTV)
4:3, ALL
4:3, ALL 4:3, ALL For MPEG 2 & 4 compatibility only





Bandwidth Density




"goal" T2W (wide)
5.55 mbs / 1 MHz
5.55 mbs / 1 MHz
5.55 mbs / 1 MHz
12, 16 MHz
"goal" T2W (widest)
5.65 mbs / 1 MHz
5.65 mbs / 1 MHz 5.65 mbs / 1 MHz
18, 24 MHz
"Maximal" T2 (reference)
6.29 mbs / 1 MHz
6.29 mbs / 1 MHz
6.29 mbs / 1 MHz
@ 8 MHz nominal





Single Frequency Networks
Possible, permitted
Possible, permitted Possible, permitted
~ (DVB-T & T2) nominal





Virtual Channel Codegroups
Forced
Forced Forced
RF channel issues





Doppler Immunity
~DVB-T, >DVB-T2
~DVB-T, >DVB-T2 ~DVB-T, >DVB-T2
Generally no worse than DVB-T!





Table Annex
Table Annex Table Annex Table Annex Table Annex





3D Ready (mode)
16 MHz, 24 MHz
14 MHz, 21 MHz
All modes
3D HD requires about 120% of nominal HD bandwidth





4k Ready (mode, provisional)
24 MHz only
21 MHz only
24 MHz only
4k requires about 250% to 350% nominal HD bandwidth





1seg Ready
ALL MODES
ALL MODES ALL MODES 1seg delivers video as a narrowband stream






Due to the changes in (error correction systems, density of scatter pilots, density of continual pilots) and other factors it is unknown if DVB-T2W will have the same Doppler Immunity (aka non affectation of reviver motion) that DVB or DVB-T2 has.

DVB-T2W should have Doppler Immunity nearly equivalent to DVB under the highest datarate transmission conditions.

At the current time there is at least some latent evidence that DVB-T2 may not be as robust as DVB-T in motor cars or airplanes when high datarate modes are used using the minimal number of pilots and scattered pilots in the datastream.


In moving to a higher order QAM constellation (higher data rate and mode) in hostile RF / microwave QAM application environments, such as in broadcasting or telecommunications, interference (via multipath) typically increases.

Reduced noise immunity due to constellation separation makes it difficult to achieve theoretical performance thresholds. There are several test parameter measurements which can help determine an optimal QAM mode for a specific operating environment.


Rectangular QAM

Rectangular QAM constellations are, in general, sub-optimal in the sense that they do not maximally space the constellation points for a given energy. However, they have the considerable advantage that they may be easily transmitted as two pulse amplitude modulation (PAM) signals on quadrature carriers, and can be easily demodulated. The non-square constellations achieve marginally better bit-error rate (BER) but are harder to modulate and demodulate.

The first rectangular QAM constellation usually encountered is 16-QAM. In QAM modulation systems, there is a Gray coded bit-assignment that has evolved that is nearly standard to the format.

Non-rectangular QAM -- a transmission format that should be added to T2W

It most be noted that T2 permits the QAM constellation to be tilted up to ~40º. It is reasonable to preserve this tilting feature in T2W.


However, it is the nature of QAM modulation that many different constellations can be constructed. Circular QAM should be allowed at lower datarates as it may provide better signal propagation versus tilted Rectangular QAM. Circular QAM may be more electromagnetically benign versus Rectangular QAM.

Areas of absolutely no change : The video resolution layers set up in ATSC that are identical to DVB will not change. However, abandonment of interlaced HDTV modes may come in the near future but for the sake of the standard it is wise to permit these transmission formats.

Interoperability

Tuner interoperability
General electromagnetic interoperability


Annex A : Backward Compatibility


For the utility of this proposal in nations already using DVB, the current authorized nation level DVB base allocation of CODECs is acceptable.

For practical purposes this means

Video
Audio are permitted by default.




Annex B : 4K & 3D Compatibility


DVB (and DVB T2) is intelligent enough that it sends out an extra robust signal for the mobile reception and a high-data rate signal for the 4K signal.

So, in essence all of the 4K possibilities of DVB and DVB T2 are absorbed by this specification. It is possible to transmit 4K and 3D at the same time, where DVB and DVB T2 cannot do this at all.

Here are some specs on the Fall 2013 experimental 4K broadcasts :

• It takes 25.24 Mb/s of bandwidth for the 4K broadcast; 1.02 Mb/s for the mobile broadcast.
• The 4K signal used HEVC encoding; mobile used H.264
• The 4K broadcast used 256 QAM modulation; mobile use QPSK

DVB is celebrating its 20th anniversary in 2013 and is currently being used in 67% of digital broadcast receivers around the world.

Phil Laven, chairman of the standards body, also reported that the 1 billionth DVB receiver just lit up in October 2013.



Technical references

Video CODECs & Audio CODECs used for broadcasting

Transmission systems (physical layer)

Transmission systems (codec layer)

Next Generation video CODECs, with no intellectual property issues

Created by
Initial idea
Created
Last Modified
Version

Last change

Revision state


Max Power
20 July 2010
14 August 2010
22 May 2014
0.77b3

Add Annex A & B

Active


This is an updated version, the original ATSC 3.0 Submission version can be found here.
Versions in PDF or other formats may become available in future but are available via request at the current time.