Sinclair’s Petition, Indoor Reception, and Receiver Performance and Improvements
The implementation of digital television, including HDTV, is proceeding ahead of pace in the United States.
This is factually incorrect as there are probably fewer than 10000 8VSB STB's in use in the United States compared to over 500,000 COFDM DTV receivers in use in the United Kingdom. Both countries launched DTV service at the same time and on a like-for-like market size the UK penetration figures would exceed 2,000,000 DTV homes in US market size. Furthermore a significant number of US broadcasters have yet to commence DTV service, there are repeated worries about the transmission standard performance, and in early December 1999 the US Department of Defense called for a review of DTV modulation standards used in the US.
The recent controversy in the U.S. arising from demonstrations given by Sinclair broadcasting should not and will not slow the pace of the transition to digital television. The great majority of U.S. broadcasters, and manufacturers of professional and consumer equipment are all squarely behind retaining VSB.
This is factually incorrect. At writing time around 49% of US television stations are either pressing for the DTV modulation standard to be reviewed, further comparative testing performed and Microsoft and the Department of Defense want the choice of DTV modulation standard reevaluated.
The FCC staff has already issued an extensive report that recommends retaining the VSB transmission system used in the ATSC Standard, and ATSC is confident that the full Commission will follow this advice.
This OET report has not been formally endorsed by FCC Commissioners as FCC policy pending the outcome of the Sinclair petition to have the modulation standard reevaluated.
The Sinclair demonstrations have highlighted a problem, i.e., that many of the first generation DTV receivers do not perform well enough in the presence of severe multipath impairments.
These receivers did not function at all in the presence of severe multipath impairments in many inner city urban areas and with indoor antenna reception. This is a known problem with 8VSB which has been highlighted in earlier comparative testing of COFDM and 8VSB in Australia and Singapore in independent programs of laboratory and field trials. After exhaustive testing both countries chose COFDM due to its superior overall performance.
But this is a problem with some receiver implementations, not with the VSB transmission system.
There is no basis for accepting this factually unsupported assertion without further independently validated laboratory and real-world field-testing.
Moreover, other receivers already in the market perform vastly better than those used in the Sinclair demonstrations, and second and third generation receivers now becoming available offer further significant improvements. In addition, several new chips have been announced that will offer even better performance against multipath impairments, and these new chips can be expected to be found in new receivers over the next several months.
These are unsupported assertions, which require further programs of independent laboratory and field testing to validate or refute the claims made above. In contrast the DVB-T COFDM system has been demonstrated to provide excellent performance in the presence of static and dynamic multipath, both in field trials around the World and in the operational DTV system used in the UK for over a year.
Sinclair’s proposal to allow individual broadcasters to choose what modulation scheme to use is unnecessary, and would cause uncertainty and delay that would paralyze the transition to DTV. 75 stations are already on the air in 34 American cities, already reaching more than half of U.S. viewers.
However less than 10000 8VSB STB receivers are in use translating to a market penetration of 0.0005% after one year of service. Many early adopters have reported SEVERE reception problems with multipath, flutter and antenna alignment problems.
It would cause at least a three-year delay to conduct the necessary testing and frequency planning studies before it could even be considered whether or not COFDM and VSB could be mixed and matched across the country.
The DVB-T system, which is consumer-proven, could be inserted into the US DTV Table of Allotments as confirmed by the earlier FCC OET report. A DVB-T system could be deployed in the United States within six months of the go-ahead.
Indeed, many observers believe that delay of the conversion to DTV is the real objective behind Sinclair’s badly biased "prove that VSB doesn’t work" demonstrations.
Another, more probable, interpretation is that over-the-air broadcasters are right to be concerned about the substandard performance of 8VSB and, as we now know, these concerns are shared by the DoD.
Indeed, as concerns about the problem of indoor reception have begun to subside, Sinclair has now voiced an ardent belief that a successful DTV business model must include mobile video services.
Concerns about indoor DTV reception have NOT subsided, as there has, to date, been no demonstration of an 8VSB receiver with indoor antenna performance remotely comparable with COFDM DTV. Around the world broadcasters are opting for DTV services which can deliver the mobile DTV service alongside HDTV in hierarchical COFDM DVB-T and ISDB-T services, from Australia, through Germany, Japan to Singapore.
This idea was carefully considered in the Advisory Committee process, and rejected because U.S. broadcasters were not willing to pay the required penalties in coverage and bit rate that would be unavoidable in such an approach.
The Advisory Process predated by some five years the development of modern DTV systems which enable mobile DTV services to be seamlessly carried in hierarchical transmissions within a 6Mhz channel without loss of coverage or bit rate. Indeed DVB-T mobile DTV services, operating in hierarchical mode, have a C/N 10dB LOWER than ATSC. The conclusions of the Advisory Process have been rendered outdated by the onward march of DTV technology.
As compared to the Sinclair demonstrations, where a handful of carefully chosen worst-case sites were chosen in an unsound and unfair attempt to discredit the ATSC Standard, field tests of the system have been conducted at approximately 2,900 sites in nine cities, including about 250 indoor sites. The overwhelming conclusion of these tests is that the ATSC system is successful in replicating NTSC coverage. By and large, where reasonably good NTSC pictures can be obtained over the air, then perfect digital pictures will also be received. And reception will only improve as newer receivers appear with better multipath performance.
The Sinclair sites were typical inner-city and suburban areas which are densely populated and showed that 8VSB was unable to be received in over three quarters of all sites whereas COFDM was received at 100% of all locations.
The ATSC testing methodology used depends on a 30ft mast, directional external Yagi and rotor. This does NOT correspond to real world DTV reception conditions and affordability of antennae by consumers, whereas many of the Sinclair tests were conducted at ground floor and indoor antenna level.
Replication of NTSC coverage is no longer an adequate business goal given the demonstrably superior ACCESS performance of COFDM to 8VSB. The FCC OET report, commenting on these ATSC measurements, noted that in a number of major US cities ATSC 8VSB coverage would be reduced by 40% compared to NTSC.
Coverage in Mexico City
Mexico City represents coverage challenges that are similar to several U.S. cities, and field tests in Chicago and New York give us confidence in predicting that the ATSC Standard is fully capable of providing superb DTV service in Mexico City.
This assertion has no basis in fact and can only be validated by an independent comparative laboratory and field trial of COFDM and 8VSB in Mexico City. In Washington DC, and Seattle measurements indicate that there is an OUTDOOR antenna coverage 'hole' of 40% of the population with ATSC/8VSB.
Transmission System Parameters and Coverage Capability
The ATSC VSB transmission system offers significant advantages over the COFDM system used in the European standard, especially when COFDM is forced to make the necessary tradeoffs to operate in 6 MHz channels. In 6 MHz channels, if the COFDM system is configured to deliver approximately the same payload bit rate as VSB, COFDM exhibits a carrier-to-noise threshold of 20.5 dB, 5.5 dB higher than the 15.0 threshold of VSB.
The latest DVB-T chipsets require a C/N of 18.5dB and there is steady commercial progress towards the theoretical limit of 16.5dB. Tests by Nxtwave of their new 8VSB chipset, which seeks to rectify the severe performance impairments of 8VSB, indicate that the minimum ATSC C/N is 16.5dB in simple RF environments.
This means that COFDM must transmit at power levels that are 3.6 times greater than VSB, with potentially severe impacts on interference into existing analog services during the transition period.
In real RF environments, as measured by Sinclair, the far field difference is 2dB for the same average DTV station ERP. This is insignificant compared to antenna downlead losses of 6dB, the diurnal fade margin of 6dB needed to counter the digital 'cliff' effect, and a typical $20 set-back preamp has a gain of 12dB.
In addition, COFDM has a 2.5 dB higher peak-to-average power ratio which when taken with the threshold difference means that COFDM transmitters must operate at power levels that are 8 dB (6.3 times) higher than VSB.
This is factually unsupported given the use of dynamic precorrection and the fact that the measured C/N difference in real-world far-field conditions is 2dB for equivalent average erp.
This would mean substantially higher initial equipment acquisition and ongoing operating costs for broadcasters.
This statement has no basis in fact without further quantification and independent analysis.
The COFDM system used in the DVB Standard offers a great variety of configurations, but careful analysis of these options reveals that there is no combination of DVB parameters that can match the combination of carrier-to-noise threshold, data rate, and ghost length provided by the ATSC 8-VSB system.
This is not correct. The DVB-T mode chosen by Sinclair matches the ATSC payload data rate very closely and has demonstrably superior multipath management performance, indoor antenna reception performance, and identical far-field coverage performance.
The ATSC Standard also offers significantly better performance than DVB in the presence of impulse noise, the kind of transmission impairment caused by automobile ignition systems, power lines, and household appliances. This disadvantage is inherent in the signal standard, and cannot be overcome by improvements in DVB/COFDM receivers.
This has already been overcome in second-generation DVB-T receivers as has been seen in the UK operational experience. In particular the earlier Philips DTX6370 receivers which were susceptible to impulse noise in low signal areas have been superseded by the DTX6371 which offers far superior performance in comparable conditions.
Recent tests carried out by the BBC and others indicate that the 8000 carrier DVB-T system has 13dB better impulse noise performance than the 2000 carrier version, which is superior to ATSC performance. Furthermore with the higher ERP's in use in the Americas compared to Europe COFDM DTV service is unlikely to be affected by impulse noise.
The apparently higher sensitivity of the VSB system to antenna aiming that was featured in the Sinclair demonstrations is not really a weakness in the VSB transmission system, but is primarily the result of the poor implementation of the particular first-generation receivers used in those tests. Other existing receivers and the upcoming new generation of receivers, all with vastly improved ghost canceling capabilities, minimize any antenna aiming problems. Furthermore, next generation receivers will employ "smarter" tuning algorithms that will further minimize this problem.
These are unsupported assertions contingent on unproven and undemonstrated future improvements in 8VSB technology, which as the Australian and Singapore tests determined, was near its theoretical limit. This can be contrasted with the off-the-shelf availability of solutions to these problems embodied in COFDM as implemented by DVB-T.
Translators and Repeaters
Like Mexico, the U.S. relies on a great many translators and repeaters to provide service to its dispersed population. In tests conducted by the Advanced Television Technology Center, the feasibility for on-channel-repeaters with the ATSC system has been demonstrated, as has the capability of a consumer DTV receive to demodulate and decode an 8-VSB signal repeated in an area shielded from the primary signal.
The DVB-T COFDM system permits local area single frequency networking where the translators/repeaters share the same frequency as the master DTV station. There is NO requirement for shielding, signals coming from different stations are additively integrated by the receiver in 'overlapped' areas, there is a 3-4dB network gain, and this is highly beneficial to shaping coverage patterns for portable and mobile DTV services.
This is NOT possible with ATSC/8VSB.
Interoperability
Regarding interoperability of terrestrial broadcast standards with cable, satellite and other media, the DVB family of standards does not convey greater interoperability just by virtue of applying the same name. In fact, the DVB terrestrial standard is suboptimized in some respects in order to utilize the same components as the DVB satellite standard that was developed earlier.
The DVB system is a suite of interoperable digital television standards permitting global economies of scale and scope. Already chips are being developed which integrate DVB-T and DVB-S for use in STB's and IDTVS generating global economies of scale and scope.
Market demand more than anything else will dictate whether single chips or single boxes support various combinations of delivery media. Such combinations are at least as likely to be developed using the ATSC DTV standard and its close cousins that are in widespread use in the U.S. for cable and satellite services.
Tests have determined that ATSC is NOT compatible with OpenCable, or with either of the two US digital satellite services. Further ATSC is not compatible with DVB satellite services such as Echostar or Sky Latin America.
Testing Programs and Procedures
Regarding potential tests of DTV systems, the ATSC has participated in extensive testing in the U.S. and in many other countries, and we stand ready to assist Mexico in planning and conducting for any such endeavor.
This is a welcome development. An independently audited program of laboratory and real-world field trials has provided incisive insights for other Administrations. In all previous selections of this nature DVB-T/COFDM has been selected in preference to ATSC/8VSB using a wide variety of selection criteria.
Convergence
The ATSC has three highly sophisticated standards development efforts under way that are taking advantage of the very latest technologies in software and data communications standards to define the ideal platform for interactive services. These are the ATSC Data Broadcasting Standard, the ATSC Standard for DTV Application Software Environment (DASE), and a standard for Interactive Services.
None of these standards is implemented in the current set of ATSC/8VSB receivers, which would have to be recalled or field modified following the finalisation of these standards. In contrast the DVB-T system has a common scrambling algorithm and is currently implementing the Multimedia Home Platform, which runs across multiple platforms, and will be supported by 'legacy' DVB receivers using platform-specific API's.
Range of Services
The ATSC Standard offers a full range of audio and video services, including HDTV, SDTV, and a limitless array of potential information services. Such services are already being delivered not only to traditional television viewers, but also to personal computer users via plug-in cards that contain full ATSC DTV receiver/decoders. The Standard also includes a variety of special services and capabilities, including emergency services, and services for the disabled.
ATSC has not implemented closed captioning, the Department of Defense has raised serious concerns about the receivability of 8VSB in emergency conditions, and a range of other services have NOT been implemented. DVB supports closed captioning, supports emergency transmission modes to portable and mobile services, and has an audio description service for the disabled.
Further PC DTV cards will be subject to the same receivability problems as fixed receivers unlike PC DTV cards utilizing a COFDM DTV system.
Mobile Services
In the North American DTV planning process, reception by mobile receivers was specifically excluded as a requirement for an advanced television system.
This can be attributed to the fact that the ATSC technical strategy has since been pre-empted by the revolutionary developments in COFDM DTV systems, in particular those operating in hierarchical modes.
Choosing technical parameters for a digital television transmission system invariably involves making tradeoffs, and supporting reception by mobile receivers would require a dramatically lower payload in terms of the delivered bit rate, or dramatically reduced coverage area for fixed receivers, or both. Neither of these tradeoffs was attractive to broadcasters, because it was considered essential to match or exceed the coverage of existing analog service, and to provide a high enough bit rate to support HDTV service in a 6 MHz channel.
This is factually incorrect. DVB-T hierarchical DTV services allow the SIMULTANEOUS delivery of a mobile DTV service (circa 4Mbit/sec) and a HDTV service (say 720P at 12 Mbit/sec) in a SINGLE 6Mhz channel. The mobile service provides outstanding coverage to mobile and portable indoor receivers and the HDTV service is available to fixed rooftop/portable indoor antennae.
For those countries where service to mobile receivers is considered important, ATSC strongly recommends that such services be offered using different bit streams in separate channels, at least. In addition, it probably will make sense to use a different modulation scheme as well.
This strategy introduces unnecessary diseconomies of scale and scope, fragments the DTV receiver market, and prevents broadcasters from offering combined mobile and fixed DTV services, or seamlessly reconfiguring their DTV service portfolio during different dayparts. It is also spectrally inefficient, as the mobile DTV service would require a different spectrum allocation.
With modern DTV systems such as DVB-T COFDM, this is UNNECESSARY as hierarchical DVB-T transmissions combine mobile DTV and HDTV/multichannel SDTV in the same RF channel allocation. Further DVB-T COFDM receivers seamlessly follow reconfigured DTV service portfolios eg from mobile to HDTV and vice versa in non-hierarchical transmissions.
If a service provider tries to make a single bit stream in a single channel with a single modulation scheme support service to both fixed and mobile receivers at the same time, the delivered payload or the coverage for stationary receivers or both will be dramatically reduced.
This is factually incorrect for DVB-T COFDM. The aggregate payload is almost identical to the non-hierarchical case, the C/N for the HDTV type fixed receiver service is almost identical to the non-hierarchical case and the mobile DTV service enjoys a much lower C/N and therefore much higher coverage. This mobile DTV service is simultaneously available to portable and laptop DTV receivers.
Since the content of the services to mobile receivers is likely to be different anyway, we believe it makes much more sense to offer a separate service to mobile receivers, and probably with a different modulation scheme optimized for mobile reception.
This constraint is a barrier to commercial flexibility, which is unnecessary in DVB-T COFDM systems. There could be a commercial requirement for a SIMULCAST mobile and HDTV service depending on broadcaster business models.
HDTV
In developing the ATSC DTV Standard, the provision of HDTV has been a major goal since the beginning of the Advisory Committee process, and HDTV remains the centerpiece among a limitless set of DTV applications. In North America, we are convinced that consumers will rapidly embrace the dazzling widescreen HDTV pictures and stunning multichannel digital surround sound offered by HDTV, and that within a few short years, viewers will demand HDTV quality for top entertainment and sports programming.
To date demand for HDTV receivers appears relatively muted because of the high receiver costs, receivability problems, the availability of lower priced near substitutes such as DVD and digital DBS, and absence of DTV cable retransmission.
In sharp contrast, there are still no plans whatsoever to offer any HDTV service in any European country--not by satellite, cable or terrestrial broadcast.
The main reason for this is, given the previous commercial failure of HDTV in Europe, is the lack of viable business models or consumer demand as perceived by European broadcasters to fund HDTV services. HDTV services delivered via digital satellite in the United States are premium subscription channels with natural incremental funding mechanisms.
Indeed, in the U.K.UK DTV service is being implemented in a way that will leave no practical means for even migrating to HDTV service, at least until analog TV services are turned off.
In the UK DTV service is growing strongly, in particular the 16x9 EDTV sector, with 2.5% market penetration achieved in nine months following launch. By 2000 it is estimated that there will be 750,000 DTV viewers (equivalent to three million US DTV homes in a comparably sized market). At current growth rates it is estimated that analog TV will be turned off in the 2006-2010 timeframe well before North America. There are outline plans to provide a mobile DTV service, using the same COFDM transmission technology able to address the same receiver population, following analog closure.
There are no plans to introduce HDTV service, as broadcasters do not detect either consumer demand or viable business models.
We believe that countries that view HDTV as an essential or important DTV application will be far better served by adopting the ATSC Standard. A huge market is emerging in North America and beyond for ATSC HDTV equipment, while Australia (with just 18 million people) remains the only country with plans to offer HDTV using the DVB standard. We believe that ATSC HDTV broadcast and consumer equipment will be far more readily available at significantly lower prices than such equipment designed to operate with the DVB Standard with its limited market potential.
To date less than 10000 8VSB STB's have been purchased. ATSC HDTV has NOT been commercially deployed in any other country, and globally there are over three hundred and fifty million tv households committed to DVB-T deployment, outnumbering ATSC by over three to one, with several trading blocs still to make DTV system choices.
Audio Services
On the topic of audio, the Dolby Digital system used in the ATSC Standard has essentially become the de facto standard for multichannel audio. The DVB Project has modified its standard to permit Dolby to be provided as an option, and Singapore and Australian have insisted on using Dolby Digital audio, even though they have adopted the DVB standard overall. Both the ATSC and the DVB systems have the ability to add support for additional audio compression schemes. However, compatibility with receivers must be carefully considered.
ATSC receivers cannot currently support dual channel audio or audio description channels.
We estimate that DVB receivers would cost about $80 more at retail than ATSC receivers.
This is a FALSE statement.
With a market size already dwarfing ATSC by three to one globally in committed TVHH and fifty-to-one in actual receivers delivered DVB-T now has unprecedented global economies of scale and scope. Indeed first generation DVB-T STB's are now available for $200 unsubsidized, and integrated DVB-T televisions are available for $750 in the UK.
The cost premium for adding MPEG2 MP@HL is IDENTICAL for ATSC and DVB, and is around 20% of the finished receiver price..
Therefore, DVB will always enjoy comparative economic advantage over ATSC due to its global acceptance outside the United States.
While an average difference of $80 may not be large in DTV receivers selling in excess of $1,000, the difference will become more pronounced with set-top boxes that contain only electronics for demodulation/decoding functions (not display capability) that are soon expected to be in the $500 retail price range.
DVB-T STB's retail for $200, enjoying a 2:1 cost advantage over ATSC.
Personal computers are also using ATSC demodulators or full receiver as add-on cards, where the retail price of such cards is already $300 or less, depending on capability. In these cases, a cost difference of $80 can be extremely important.
This is a FALSE statement. See above.
On the transmit side, as noted above, VSB has an 8 dB advantage over COFDM due to the difference in carrier-to-noise threshold and peak-to-average power. This means that COFDM transmitters would either need to operate at 3.6 times greater power, or a network of smaller transmitters would need to be established with added controversy and impact on the environment. Either way, this would mean substantial increases in acquisition and operation costs. These same considerations would apply to the use of translators and repeaters.
Again, these are FALSE statements, as discussed earlier.
Summary
Mexico has played an important role in defining the needs and parameters for an advanced television system through the participation by Mexican companies and individuals in the Advisory Committee on Advanced Television Service that worked for ten years to define the ATSC DTV Standard. Implementation of that system is now fully under way in the U.S., with service already reaching more than 50% of American households.
Although the ATSC service COVERS 50% of US households less than 0.0005% of US homes have ACCESS to US DTV. By contrast, over exactly the same time period, the UK COFDM DTV system now COVERS 90% of the population and has ACCESS to over 2.5% of homes.
The recent controversy arising from the demonstrations by Sinclair Broadcasting is rapidly abating, as people come to understand that the Sinclair demonstrations said far more about the poor performance of the particular receivers Sinclair chose to highlight than about the capabilities of the ATSC VSB system itself. In addition, broadcasters and the FCC have come to understand that other receivers perform much better and that further significant improvements are on the near horizon.
These statements are unsupported by independent evidence. Indeed with the intervention of the DoD, the US controversy over the fragility of the 8VSB standard is intensifying, with a petition to reexamine the issue before the FCC. To date, no 8VSB receivers have been demonstrated which solve these problems, which are easily handled by DVB-T/COFDM.
As more HDTV programming becomes available over the next few months, we expect consumer enthusiasm and purchases to soar as they witness the dazzling picture quality and impressive surround sound of HDTV. And new data services broadcast to smart DTVs and to personal computers are now beginning to be offered as well, promising revolutionary benefits over the next decade and beyond.
This is an unsupported assertion, given the demonstrable fragility of the US 8VSB DTV standard.
We believe that for Mexico the ATSC DTV Standard offers significant technical advantages over the European DVB system.
This is an unsupported assertion without a program of independently validated laboratory and field trials to evaluate both systems against a set of criteria suitable for Mexico's specific needs.
But in addition to these technical advantages, we believe there are compelling economic and compatibility reasons for Mexico to align itself with the same standard that is being implemented so rapidly in the U.S.
The US DTV implementation is now in danger of outright market failure, given very weak consumer demand, the absence of viable DTV business models, and accelerating doubts about the performance capabilities of the 8VSB modulation standard. Therefore it may be prudent for Mexico to suspend DTV implementation and await the resolution of these issues or else adopt globally proven DTV standards.
The ATSC stands ready to address any concerns that Mexican broadcasters or the Mexican government may have, and we pledge our continued full support to bringing the benefits of this fertile new technology to the Mexican people.
The most appropriate route to investigate these issues would be to conduct an independent program of audited laboratory and real-world field trials. This would enable Mexico to verify the capabilities of rival DTV systems, mirroring the experience of other Administrations, and confidently base its choice on a program of autonomous tests in real-world reception conditions.
