NTT DoCoMo's IMT-2000:

The Next World
Standard for

by Noriko Takezaki

When I travel to Europe or North America, can I use the same cellular phone I'm using here in Japan?" Unfortunately, for the world's current mobile phone systems, the answer to this often-heard question is "no." But it may be "yes" in the near future, for the next-generation mobile communications system known as IMT-2000 (International Mobile Telecommunications-2000) - if, that is, IMT-2000 system developers can resolve their differences and agree to cooperate for unification of a global standard.

Today, there are several different mobile phone systems in use throughout the world. Japan has adopted a TDMA (time-division multiple access) method called PDC (Personal Digital Cellular standard), which utilizes the 800-MHz and 1.5-GHz bandwidths. Europe, meanwhile, has a TDMA method called GSM (Global System for Mobile communication) using the 800-MHz, 1.8-GHz, and 1.9-GHz bandwidths. And in North America, yet another TDMA method called D-AMPS (Digital Advanced Mobile Phone Service) is used at the 800-MHz bandwidth, along with a CDMA (code division multiple access) method called IS-95 used at the 800-MHz and 1.9-GHz bandwidths.

Toward a next-generation standard
Because there is no interoperability among these differing TDMA and CDMA systems, a traveler cannot use the same cellular phone worldwide. For the next-generation IMT-2000 system, however - which is to use the 2,000-MHz (2-GHz) bandwidth - preparations for worldwide standardization are progressing. There is a good possibility - but, unfortunately, not a certainty - that IMT-2000 will be a unified global standard.

Three major air-interface methods are currently being investigated for IMT-2000: one proposed by Japan (NTT Mobile Communications Network; known as NTT DoCoMo), one proposed by Europe (Ericsson, Nokia, and Siemens), and one proposed by North America (Qualcomm, Motorola, Lucent Technologies, and Nortel). Although these proposed methods are all based on the same wideband CDMA (W-CDMA) technology, each is slightly different, which threatens worldwide interoperability unless a global standard is reached.

Since the European-proposed W-CDMA method shares some factors in common with the DoCoMo method (such as a 4.096M-cps* chip rate, asynchronous intercell mode, and 10-ms* frame length), it is expected that the European and Japanese sides will eventually come to an agreement for establishment of a unified standard. In fact, in June of this year, Ericsson and Nokia voiced their support for the NTT DoCoMo method.

The North American side, meanwhile - particularly Qualcomm, the original inventor of the CDMA technology - has been maintaining its independence. The US has proposed totally different characteristics for W-CDMA technology, (a 3.684M-cps chip rate, synchronous intercell mode, and 20-ms frame length). The ultimate battle over IMT-2000 standardization, therefore, is likely to pit a Japanese-European team against the holdout North American camp.

In Japan, NTT DoCoMo has been a key player in development of the next- generation air-interface technology.

The NTT DoCoMo method
In Japan, NTT DoCoMo has been a key player in development of the next-generation air-interface technology. The company has already proposed its own W-CDMA method to the Association of Radio Industries and Businesses (ARIB), a Japan-based standardization organization, and this proposed standard seems the most likely candidate for submission by Japan to the ITU (International Telecommunications Union) as a world standard next spring.

A major reason for the active involvement of NTT DoCoMo in this issue lies in the shortage of frequency bandwidths for its current PDC system, particularly in the 800-MHz range. Because of the drastic growth of its subscribers, NTT DoCoMo, Japan's most successful mobile phone system operator, fears that its allocated frequency bandwidths may be used up soon after the turn of the century.

This is not the only reason, however. "In the development of a next-generation mobile communications system, Japan has been leading the world in terms of exploring the multimedia field for mobile phone businesses," says Atsushi Murase, executive manager in NTT DoCoMo's research and development department. "The cellular network operators of other countries have not been thinking seriously about exploiting the multimedia field, which covers not only voice service but also data and image services. They have thought that voice service would be enough, and only recently - with the worldwide growth of the mobile phone market and the introduction of many mobile computing applications, as well as the drastic growth of the Internet - have they started to think about multimedia services."

There is a good possibility - but, unfortunately, not a certainty - that IMT-2000 will have a unified global standard.

NTT's research into a next-generation mobile phone system dates back to 1981, when Nippon Telegraph and Telephone Public Corp. (the public manifestation of NTT, before it was privatized in 1985) utilized the resources of its CDMA basic research. In 1992, NTT DoCoMo started full-fledged research into CDMA, and by 1994 the company had proposed its W-CDMA method to the ARIB. In 1996, NTT DoCoMo realized a successful field experiment in 2M-bps W-CDMA transmission.

NTT DoCoMo's W-CDMA method features high-quality voice transmission (equivalent to the quality of a wire-based network), flexible transmission power control in accordance with traffic conditions, efficient channel management (using pilot symbol-aided coherent detection), and multi-rate services using multi-code duplex. To promote its W-CDMA method, NTT DoCoMo has been preparing for system experiments to start this fiscal year by constructing a dedicated R&D center (to be completed in spring 1998). Indoor and outdoor tests are scheduled to be completed in FY1999, and the target date for starting commercial service is FY2000.

NTT DoCoMo has already selected several Japanese and foreign suppliers for the base station facilities and mobile terminals of its system experiments. For base station equipment, Ericsson, Fujitsu, Lucent Technologies, Matsushita Communication Industrial, and NEC were selected. The mobile terminals will be supplied by Matsushita Communication Industrial, Mitsubishi Electric, Motorola, NEC, Nokia, Sharp, and Toshiba.

Services that will be tested during the experiments include 8K-bps high-quality voice transmission, 28.8K-bps modem transmission, 64K-bps digital transmission, and 384K-bps or greater packet data transmission and moving image transmission. Functional confirmation tests will check sector and base station configurations, high-speed cell search, diversity handover, random access, and ATM (asynchronous transfer mode) transmission.

An unexpected left jab
The road for NTT DoCoMo, however, has not been as smooth as was expected. Early this year, NTT DoCoMo faced a fierce fight with mobile phone operators IDO and the Cellular Phone group companies. These operators announced that they had decided to use the IS-95 method for their digital network services (to be started next year), and expressed support for the extended version of IS-95 being proposed for IMT-2000 by the North American camp. Their reason was obvious: to beat dominant NTT DoCoMo. As of August 1997, NTT DoCoMo had over 13.8 million subscribers, far more than the Cellular Phone group's 3.7 million and IDO's almost 2.0 million.

While this jab at NTT DoCoMo did not seem strong, it punched the company from an unexpected angle and caused it to stagger. The revolt against NTT DoCoMo influenced the IMT-2000 system study group organized by the Ministry of Posts and Telecommunications (MPT), which was preparing to make a recommendation regarding the selection of a Japanese standard for IMT-2000 to the Minister. Contrary to expectations, the study group's final report (published in June 1997) declared, "It is too early to decide the orientation of the system image of IMT-2000 at this stage."

The report had been expected to recommend the W-CDMA method proposed by NTT DoCoMo and, if it had, that method would almost certainly have been selected as the Japan standard to be submitted to the ITU - very likely within this year. The "it is too early to decide" declaration, however, casts a shadow over the NTT DoCoMo method, and Japan's proposal to the ITU has effectively been postponed until next year.

But NTT DoCoMo remains optimistic. "If two or more methods should be proposed to the ITU as Japanese standards, it would be awkward considering the very basic purpose of standardization activities," observes NTT DoCoMo's Murase. "We are very proud of our [IMT-2000] technology. Our method has the greatest commonality with PDC, GSM, and IS-95. Therefore, it will be beneficial for the network, since the operators can utilize many of their existing platforms for the operation of IMT-2000 service."

Seeking foreign support
Part of the reason for NTT DoCoMo's optimism is the support it has garnered from other companies inside and outside Japan. KDD and Japan Telecom are backing the NTT DoCoMo method, and NTT DoCoMo has obtained support from two Asian cellular network operators - SK Telecom in Korea and PT Telekomunikas in Indonesia - as well as European vendors Ericsson and Nokia. SK Telecom and PT Telekomunikas have agreed to participate in NTT DoCoMo's W-CDMA system experiments, and also to exchange engineers between the companies.

The support from SK Telecom, in particular, is significant. SK Telecom is the largest cellular network operator in Korea, having more than 1 million subscribers to its IS-95 service. "We've heard that the reason SK Telecom decided to cooperate with us is that they want to widen the range of choices for their services, and not depend on a technology developed by a single, particular company," says Murase of NTT DoCoMo.

NTT DoCoMo has invited several other foreign operators - particularly those in the Asia-Pacific and Europe, and even some in North America - to participate in its IMT-2000 system experiments. These operators include China's Ministry of Posts and Telecommunications, Singapore Telecom, Telecom New Zealand, Telecom Malaysia, Telephone Organization of Thailand, Telstra (Australia), Cellnet (UK), De Te Mobil (Germany), France Telecom, Telecom Italia Mobile, Telia (Sweden), AT&T Wireless (US), and Bell Mobility (Canada). As of late September, however, none had accepted NTT DoCoMo's invitation.

Huge market potential
Meanwhile, the MPT has been actively working behind the scenes for smooth and quick (aiming at "world's first") deployment of IMT-2000 services in the Japanese market. The MPT schedule calls for the first stage of IMT-2000 commercial service in Japan to start in 2001 (for high-quality voice communications, 64K-bps N-ISDN line switching service, 144K-bps data packet transmission, and 384K-bps image data transmission). The second stage for more advanced services (like 2M-bps packet data transmission) would start in 2003.

To lay the groundwork for commercial IMT-2000 services in Japan, the advisory body of the Minister of Posts and Telecommunications, the Telecommunications Council, started deliberations in September regarding IMT-2000 technical specifications (including the disputed air-interface technology methods and general system conditions). Deliberations are scheduled to be completed in April 1999 - just one month after the ITU's expected decision on the basic parameters of IMT-2000 - to ensure a swift start for Japan's IMT-2000 services.

Regarding the controversy over air-interface methods, the MPT hopes to serve as mediator between NTT DoCoMo and its opponents (for unification of the Japan standard) and between Japan and other countries (for unification of a world standard). "The decision on IMT-2000 is not a simple issue of technology," says Shuichi Inada, the MPT's director at the land mobile communications division in the Telecommunications Bureau. "Some political settlement may be inevitable for adjusting opinions among the parties having a conflict of interests."

"The important point is, I think, how to perceive the market of IMT-2000," continues Inada. "It can grow as a huge, global multimedia market in which the cellular network operators will eventually offer tough competition for the fixed-network service operators. Also, from the viewpoint of vendors, their target market size can be expanded globally. For example, there is a huge potential market for IMT-2000 in Asia. Considering such factors, the wise choice for [Japanese companies] now is to get more support for long-term, comprehensive business schemes, not to advance their immediate interests."

The future mobile standard
In the end, it is likely that the NTT DoCoMo method will be selected as the Japan standard. Regarding whether it will become the world standard for IMT-2000, however, industry insiders put the probability at 50%.

It is still unclear whether the North American camp - which includes the original inventor of the CDMA technology - will make concessions to the likely Japan-Europe team. To entice the North American players, the Japanese side is emphasizing that the potential size of Japan's mobile phone market is tremendous - for vendors on the right team. This promotional line has been successful with European vendors, but nobody is sure yet whether it will seduce any players on the North American team.

And what of the general consumer, who simply wants to be able to use his cellular phone anywhere in the world? The best advice is to cross your fingers, and hope that the politicking among countries and vendors will soon lead to a unified IMT-2000 world standard.

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