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TD-SCDMA arrives-with baggage -- Digging a hole in China
(Electronic Engineering Times Via Acquire Media NewsEdge) If there was ever a standard that should never have come to be, it's time-division, synchronous code-division multiple access (TD-SCDMA). Yet, here it is. China's effort at technological differentiation and self-determination in the rapidly evolving world of 3G mobile multimedia is to be showcased-with much fanfare-at the upcoming Olympic Games in Beijing. Then, in all likelihood, it will fade away.
Unless, of course, China's Ministry of Industry and Information Technology (MIIT) continues to ram the standard down the throat of a reluctant China Mobile, while at the same time further delaying the issuance of licenses for the third-generation cellular technologies the rest of the world is using:
wideband CDMA and cdma2000. Such a delay would give TD-SCDMA the breathing room it needs to overcome certain technical hurdles and extend its coverage.
It's not that the standard itself is inherently flawed. On the contrary, time-division multiplexing offers some advantages over the frequency-division duplex (FDD) wideband-CDMA mode. (W-CDMA supports both TDD and FDD, but the latter is being emphasized in current deployments.) With TDD, it's easier to assign time slots dynamically to adjust for asymmetric Internet traffic. TDD is also more spectrally efficient, and it simplifies frequency planning. Further, the use of a single band obviates the need for FDD's expensive and bulky filters, and allows more-accurate channel estimation techniques.
Like all technological innovations, however, TD-SCDMA requires testing and improvement. That's where the problem arises. Mobile wireless tests take time and money. The latter seems to know no bounds, and the former is running out as China falls further behind the rest of the world in its 3G rollout.
Early TD-SCDMA trials revealed coverage and capacity problems, and the data rates-2.8 Mbits/second in the downlink and 384 kbits/s for the uplink-need to be improved by going to a multicarrier format. (Putting multiple carriers together yields higher data rates.) But that creates its own set of problems, which have yet to be resolved.
So, why did China pick TD-SCDMA in the first place? Therein lies the irony.
In 2006, Zhou Huan, chairman and president of Datang Technology, a major backer of TD-SCDMA, pointed to the slow progress and birthing pains of W-CDMA-performance issues and the late arrival of handsets-as a chance for China to get ahead of the rest of the world with a more spectrally efficient standard that, theoretically, would cost less to deploy. It wouldn't be the first time a major nation went down its own road. In an earlier wireless generation, the United States chose CDMA over the more widely used GSM, and fell woefully behind Europe and the rest of the world in cellular proliferation and usage. Likewise, Japan opted for PDC over GSM in 1991, and its citizens remained isolated with poor-quality voice and low-quality handsets.
But rather than an opportunity, W-CDMA's problems should have been a red flag for the Chinese. Wireless, especially 3G, is just plain hard to do. Ask any of the operators or equipment providers that have been steeped in W-CDMA for the past 10 years.
Even though W-CDMA and cdma2000 are now proven and deployable technologies that are rapidly moving down the cost curve, China Mobile, under pressure from the MIIT, continues commercial trials of TD-SCDMA. "The Chinese government will ensure China Mobile sticks to TD-SCDMA no matter what happens; it has to make TD-SCDMA work," said Hwai Lin Khor, wireless analyst for ABI Research (Singapore).
Indeed, "The MIIT needs to have some achievement to show the country. If they give up, they lose face," said Kevin Wang, senior manager of China research at iSuppli Corp.
So motivated, China Mobile announced in May that it had invested up to $2.04 billion to install TD-SCDMA networks in eight Chinese cities and that coverage had reached 95 percent that of 2G networks (see story, page 46). These, however, are still commercial trials. Forecasters see TD-SCDMA in 30 cities by year's end, translating to 500,000 users by the end of 2008 and 3 million by the end of 2009. The MIIT originally wanted 10 million users by the close of next year.
Nothing to sneeze at
Of course, that's still a lot of handsets and basestations-and a lot of chips. For basestations, the main equipment suppliers are Huawei and ZTE; the chip suppliers are mainly Texas Instruments, Analog Devices and Xilinx.
Basestations are expensive to deploy for a yet-unproven technology. But suppliers aren't too worried, since the equipment can be reprogrammed for other standards, such as W-CDMA, said Ramesh Kumar, worldwide director of marketing at Texas Instruments Inc.
The real commitment comes from handset manufacturers, the leading one being ZTE, with 26.9 percent of the TD-SCDMA market, according to iSuppli's figures. It's followed by Xinyoutong, with 15.8 percent; Samsung and Hisense, each with 9.4 percent; and Lenovo, with 7.5 percent. Other players include Postcom, Amoi, LG, Holley and Datang. From Taiwan, BenQ, Compal and Sunplus are also entering the game.
ZTE's model U980 smart phone is almost exclusively driven by chips from Analog Devices Inc., which has sold its cellular division to China's Mediatek. ZTE was already an ADI customer before the acquisition, so the chips still have ADI markings, according to a recent video teardown (see above).
Christian Kermarrec, Mediatek's wireless president and corporate vice president, called the company's TD-SCDMA customers a who's who of Asian mobile players, including LG, Hisense, HTC, Yulong, UT and BenQ. In fact, Mediatek found sockets in more than 60 percent of the handsets China Mobile purchased before the Olympics. "Spreadtrum and T3G have 20 percent and 12 percent, respectively," Kermarrec said.
Make-or-break time
While Mediatek is making hay off TD-SCDMA-as is Spreadtrum, another homegrown company that makes wireless RF, baseband and multimedia chips-other handset chip makers are not faring so well. Startups T3G and Commit are especially troubled. Datang Mobile, a primary holder of TD-SCDMA intellectual property, is pulling its stake in T3G, though Samsung and STMicroelectronics remain backers. ST inherited its stake when it acquired NXP's cellular division earlier this year.
Commit, for its part, went bankrupt after Nokia withdrew backing. Commit was launched in 2001 as a $233 million investment by a number of interests, including Datang and Texas Instruments.
The lack of stamina from once-staunch supporters doesn't augur well for a nascent standard. Indeed, the tepid support of TD-SCDMA by chip and equipment suppliers that are members of the TD-SCDMA Forum is remarkable in and of itself. A smaller base of chip providers translates to higher costs, although ABI's Khor is hopeful that if China Mobile can hold out for a couple of years, other chip manufacturers will step in to drive costs down.
And if the Olympic trials go well, there may still be life in the standard. Clearly, the Summer Games will be the first milestone for TD-SCDMA, but it's safe to assume those trials will take place under very controlled conditions, making sure that whatever capacity is available isn't stretched or stressed in any way.
Then what?
The "ifs" go on: If, after the Olympics, the MIIT holds off on granting licenses for cdma2000 or W-CDMA, there may be time to iron out TD-SCDMA's wrinkles and for subscribers to climb on board. If TD-SCDMA successfully enters the LTE standard, incumbent operators outside China can deploy both FDD and TDD LTE at the same time to achieve higher capacity. Currently, said Khor, China Mobile, Verizon and Vodafone are involved in three-party trials for LTE that involve both FDD and TDD.
Odds are that once TD-SCDMA has been shown to work-and it probably will work, eventually-China Mobile will be free to migrate quickly to 4G options. How soon that happens depends on whether issues such as multicarrier operation can be overcome. In the view of iSuppli's Wang, if the Chinese successfully develop multicarrier operation, TD-SCDMA will last five years. If not, its life span will be two to three years, tops.
That said, the MIIT's moves in this area continue to confound the best analyses. In the end, TD-SCDMA is less about technological innovation than about government grandstanding. It's a homemade dim sum that's being force-fed to reluctant operators, supported by a few noteworthy but noncommittal chip suppliers. Whether it ultimately succeeds or fails, TD-SCDMA may go down as the greatest waste of technological expertise in the history of wireless.
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TD-SCDMA serves as a newbattleground for 3G
http://www.mobilehandsetdesignline.com/171000285
Relying on a combination of time-division duplex (TDD) and synchronous CDMA, TD-SCDMA offers some key advantages, including no need for paired frequencies, suitability for IP services, the ability to support asymmetric services in up/downlink and the flexibility to incorporate new technologies (e.g., joint detection, adaptive antennas, dynamic channel allocation).
This feature describes the characteristics and structure of TD-SCDMA signals and some architectural approaches to meeting their requirements.
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Building multicarrier TD-SCDMA transmit architectures
http://www.mobilehandsetdesignline.com/howto/209100382
While TD-SCDMA does have strong merit, in order to improve its data rates, it must be able to handle multicarrier signals. That remains a thorny issue, as digital-to-analog converters and multicarrier power amplifiers must preserve the spectrum of several digitally generated carriers without corruption or spurious signal generation in adjacent channels. Thus, a basestation transmitter must generate a minimum of spectral regrowth, both on the individual carriers and as a result of intermodulation between the carriers.
This article describes the analog, digital and mixed-signal components required to build an image-rejection basestation transmitter architecture. Designers can use the information as a guide during the design and development process.
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TD-SCDMA RD V2.1 design Meets Rx-Blocking Mask and Sensitivity Requirements
http://www.techonline.com/learning/techpaper/199500686
This application note introduces Maxim's second-generation TD-SCDMA radio-frequency transceiver chip set with its V2.1 reference design. It also discusses some of the key system issues, such as sensitivity and blocker tests, that warrant careful consideration by those looking to create an optimum TD-SCDMA RF design.
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EE Times Edge digital edition exclusive:
View our video teardown of a ZTE handset designed for China's homegrown
TD-SCDMA standard at: http://link.brightcove.com/services/player/bcpid1659825400
http://www.eetimes.com/
Copyright 2008 United Business Media LLC. All rights reserved.
Copyright ? 2008 CMP Media LLC
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