[opendtv] Re: China writes its own digital TV standard
- From: "Bob Miller" <robmxa@xxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Mon, 26 Jun 2006 21:35:58 -0400
It is going to be interesting watching what modulation Chinese broadcasters
pick.
Bob Miller
On 6/26/06, Manfredi, Albert E <albert.e.manfredi@xxxxxxxxxx> wrote:
>
> Very interesting.
>
> I thought ADTB-T was the orthogonal AM scheme described some time ago,
> which was almost identical to 8-VSB except that it used a two-phase AM
> approach instead of chopping off a sideband of AM. But here they
> actually mention that it's VSB. So something must have changed.
>
> China seems to have liked Sinclair's idea. Accept both.
>
> Bert
>
> --------------------------------------
> China writes its own digital TV standard
>
> Mike Clendenin
> (06/26/2006 9:00 AM EDT)
> URL: http://www.eetimes.com/showArticle.jhtml?articleID=3D189601091
>
> TAIPEI, Taiwan - After years of rivalry and numerous delays, China is
> poised to roll out a long-awaited standard for terrestrial digital
> television.
>
> The mandatory standard will cover both fixed and mobile terminals and
> will eventually serve more than half of China's TV viewers, especially
> those in suburban and rural areas.
>
> Though its name is not official yet, the standard is being called
> Digital Multimedia Broadcast-Terrestrial/Hand- held. DMB-T/H signals the
> beginning of the end for small Chinese trials of Europe's DVB-T
> standard, and it adds another rival to the mix for mobile-TV services in
> China-the world's largest market for TVs and mobile phones.
>
> An official announcement of the new standard is imminent, sources in
> China said, and could come as soon as this week. Its release will end a
> fierce rivalry between two universities with very different approaches
> to the terrestrial standard.
>
> DMB-T/H is an outgrowth of work at Tsinghua University in Beijing and
> Jiaotong University in Shanghai, each of which had hoped to provide the
> sole technology--but neither of which had the technical or political
> muscle to achieve that goal.
>
> The result is less a combination of their work than a coexistence of two
> modulation schemes-Tsinghua's time-domain synchronous orthogonal
> frequency-division multiplexing (OFDM) and Jiaotong's vestigial sideband
> (VSB) modulation.
>
> "Like 802.16, China's new digital TV standard has both a single-carrier
> and a multicarrier option," said Lin Yang, president of Legend Silicon,
> a Fremont, Calif.-based company closely affiliated with Tsinghua
> University.
>
> China will deploy digital TV over VHFIII and UHF spectrum ranges, using
> 8-MHz channel bandwidth. Jiaotong's portion of the standard is called
> ADTB-T, for Advanced Digital Television Broadcast-Terrestrial. Like the
> U.S. DTV standard, ATSC 8-VSB, it is based on single-carrier frequency.
>
> Supporters say ADTB-T technology lets signals travel longer distances at
> less power, with user terminals that are better at detecting weak
> signals. It has an edge in protecting against adjacent-channel
> interference and offers better performance at higher bit rates, making
> the technology a good candidate for HDTV streams to fixed terminals,
> said Yao Wang, an executive at ASIC designer Shanghai High Definition
> Digital Technology Industrial Co., which is affiliated with Jiaotong
> University.
>
> But unlike ATSC, Jiaotong's ADTB-T can provide nomadic TV service as
> well. In Shanghai, a trial has been under way since 2004 in which five
> transmitters broadcast to about 2,000 terminals, 1,600 of them in taxis.
> Nomadic services are also being tested on buses in Weihai, Shandong
> Province, and trials for fixed TV services are under way in five other
> cities and counties.
>
> But Tsinghua believes its DMB-T proposal is good not only for fixed
> terminals but also for video and data broadcasts to portable devices
> like handsets and PDAs.
>
> DMB-T taps the OFDM modulation scheme of Europe and Japan. Its 4k
> carriers are modulated with quadrature phase-shift keying or quadrature
> amplitude modulation. But it differentiates itself by using time-domain
> synchronous (TDS) OFDM.
>
> With data rates as high as 32 Mbits/second to cater to multimedia
> services, TDS-OFDM aims to better synchronize mobile and burst data
> broadcasts.
>
> But TDS-OFDM, unlike coded OFDM, uses the protective guard interval
> between data blocks by inserting a pseudo-noise sequence to do
> synchronization and channel estimation.
>
> "In COFDM," said Xingjun Wang, a Tsinghua University professor who led
> the developers of DMB-T, "there is nothing in the guard interval. So by
> using that part for channel estimation, it saves capacity from the
> carrier part by about 10 percent. Also, in the time-domain timing
> recovery, the accuracy and response time will be much shorter than in
> COFDM technology, which uses a frequency domain. Generally speaking, we
> can increase 3-dB sensitivity compared to DVB-T."
>
> Usually, OFDM approaches-the basis of DVB-T/H, ISDB-T, T-DMB and
> Media-Flo-are favored in broadcasting. Trials for Tsinghua's DMB-T are
> under way in about 30 cities, handily eclipsing the trials for
> Jiaotong's ADTB-T.
>
> What remains unclear, though, is whether all of China's digital
> TVs-fixed and mobile-will have to support both the TDS-OFDM and VSB
> schemes.
>
> Tsinghua University's Wang said demodulators should support both specs,
> even in handhelds. Rather than just sticking two demodulators on one
> chip, he said, his team used new techniques to enable the dual-mode
> demodulation. Details of the new techniques were not immediately
> available.
>
> On the other hand, Legend Silicon's Yang, said, "Maybe the government
> will ask the market to make a decision," by giving broadcasters an
> option on modulation schemes. Yang added, however, that the intent of
> the new Chinese DTV standard is "to make the single carrier and
> multicarrier adhere as closely as possible."
>
> Originally, China planned to release a draft for terrestrial digital TV
> in 2003 and to start the transition in 2004, but industry and government
> officials brokered a compromise between the two university efforts that
> emerged as leading contenders. The rivalry, insiders say, was fierce.
>
> At that time, the technologies were quite different, said Legend
> Silicon's Yang. But the teams have tried for two years to harmonize
> their efforts.
>
> "It's not an apples-to-oranges comparison anymore," Yang said. "The
> frame size, the P/N sequence, the synchronization data-everything is the
> same. The only difference is whether the signal is
> frequency-domain-defined data or time-domain-defined data."
>
> He called the Chinese standard closer to Japan's ISDB-T than Europe's
> DVB-T, because China and Japan consider the issue of low power
> consumption in the main spec. China's DMB-T/H is also unique in that,
> unlike DVB-H, both terrestrial and handheld devices are designed from
> the ground up to use the same spectrum.
>
> Like ISDB-T, the Chinese standard will support HDTV on nomadic devices,
> while Europe's DVB-T now supports only standard definition. China's new
> standard also differs from T-DMB, originally developed by South Korea
> for mobile TV. T-DMB, based on the Eureka-147 Digital Audio Broadcast
> standard, transmits at lower data rates and is designed for small
> portable devices like handsets and PDAs.
>
> One key difference between Korea's T-DMB and China's DMB-T/H: The former
> uses multiple, smaller channels at lower bandwidth, and must use more
> spectrum for channel separation; the latter uses wider channels at
> higher bandwidth for better spectrum efficiency, but the trade-off is a
> slightly higher receiver cost.
>
> A handful of Chinese companies already have silicon, or are prepping it,
> for DMB-T/H. Legend's demodulator handles both DMB-T and ADTB-T, and it
> is working on a low-power version for handheld devices, said Dinesh
> Venkatachalam, vice president of engineering at Legend.
>
> Shanghai High Definition Digital Technology is working on a
> second-generation chip that will support both components of the
> forthcoming standard. Others designing chips include Hangzhou-based
> Guoxin Technology and Shanghai-based Chinips Electronics. In handhelds,
> Microtune said it plans to expand its mobile tuner product line,
> including China's DMB-T/H.
>
> But multinationals in the set-top-box business are more cautious. At
> STMicroelectronics, "We are watching the standard," said Bob Krysiak,
> corporate vice president for Greater China, "and we think we understand
> the combination of the two, but just want to see it written down, and
> then we will be prepared to implement something as soon as the ink is
> dry on the spec." Conexant is also taking a wait-and-see approach. "I
> can't say when we will have a chip out but we are engaged and tracking
> the spec," said Henry Derovanessian, vice president of marketing for
> broadband media processing at Conexant.
>
> Set-top-box makers and some TV makers like Haier, Samsung and LG also
> have prototypes based on DMB-T/H. But Chinese TV and STB makers are
> mixed over how quickly consumers will adopt DTV services, and that will
> affect the pace at which TV makers integrate the digital tuners.
> "Hopefully, the integrated TV will hit the market this year, but it will
> take at least 10 years to popularize," said Chunguang Wang, a design
> engineer at TV maker Changhong Electric Co. "It's not easy to change the
> situation that a large number of families watching digital TV use a
> complementary STB, and the government is encouraging using STBs as a
> faster way of popularizing digital TV."
>
> Slow transition
>
> Indeed, the next challenge will be kick-starting the analog-to-digital
> transition. China had wanted to see 100 million DTV households by 2008,
> when it plans to air HDTV content from the Summer Olympics in Beijing. A
> 2015 deadline is in place to end analog broadcasts.
>
> But China is seeing a slow transition. By the end of 2005, only 4.1
> million households were using digital TV services, mostly based on
> cable, according to government figures. That was up considerably from 1
> million households the year before, but far short of the government's
> target, set last year, of 30 million households.
>
> Hurdles include the cost of the STBs and services, and a lack of
> compelling content that would motivate users to change. The terrestrial
> transition may face similar challenges, said Mark Natkin, a
> Beijing-based analyst for Marbridge Consultants.
>
> All material on this site Copyright 2006 CMP Media LLC. All rights
> reserved.
>
>
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