ITU approves key characteristics for the radio interfaces of third generation mobile systems

IMT-2000 spectrum requirements input for Preparatory meeting of WRC-2000 also agreed

25 March 1999

Geneva - The meeting of the International Telecommunication Union on IMT-2000 (ITU-R Task Group 8/1), which concluded last Friday in Fortaleza (Brazil), agreed on the way to proceed with the standardization of IMT-2000. The results of the meeting take account of input from the global wireless industry including operators, regulators, consortia and the TransAtlantic Business Dialogue. The meeting also reached consensus on the additional spectrum requirements for IMT-2000 for the Conference Preparatory Meeting (CPM) of the World Radio Conference 2000. A major objective for the meeting was to adopt a set of key characteristics for the IMT-2000 radio interfaces as an initial step towards the development of more detailed ITU specifications for IMT-2000.

The decisions reached at Fortaleza provide essentially a single flexible standard with a choice of multiple access methods which include CDMA1, TDMA1 and combined TDMA/CDMA, all potentially in combination with SDMA1, to meet the many different mobile operational environments around the world. Although second generation mobile systems involve both TDMA and CDMA technologies, very little use is currently being made of SDMA. The advent of adaptive antenna technology linked to systems which have been designed to optimize performance in the space dimension should significantly enhance the performance of future systems.

Participants agreed that the further development of the more detailed IMT-2000 radio interface recommendations within the ITU should continue to aim at minimizing the impact of flexibility within the IMT-2000 standard on users through maximizing commonality and ease of digital implementation in a hand-held mobile unit. It was also agreed that IMT-2000 radio interfaces should include the capability of operating with both of the major third generation core networks currently under development.

The IMT-2000 key characteristics are organized, for both the terrestrial and satellite components, into the RF (radio frequency) part (front end), where impacts are primarily on the hardware part of the mobile terminal, and the baseband part which is largely defined in software. In addition to RF and baseband, the satellite key characteristics also cover the architecture and the system aspects. The use of common components for the RF part of the terminals, together with flexible capabilities which are primarily software defined in baseband processing, should provide the mobile terminal functionality to cover the various radio interfaces needed in the 21st century as well as provide economies of scale in their production.

There are already many multi-mode/multi band mobile units appearing on the market to meet the evolution needs of today’s systems and by, early next century, there should be negligible impact in areas such as power consumption, size or cost due to the flexibility defined within the IMT-2000 standard if harmonization efforts during the more detailed definition stage are strongly focused towards the needs of the end user.

The key characteristics by themselves do not constitute an implementable specification but establish the major features and design parameters that will make it possible to develop the detailed specs (to be referred to as IMT.RSPC) between June and November 1999.

The main purpose of the consensus building phase that preceded the meeting in Brazil was to minimize the number of IMT-2000 terrestrial radio interfaces and maximize their commonalities. This process is expected to continue through participation of the major industry groups in the further ITU harmonization of the key characteristic data based on the values or range of values agreed at Fortaleza.

However, due to the constraints on satellite system design and deployment and because it was considered that there was little to be gained at this time from harmonizing any of the satellite proposals since they were already global, several satellite radio interfaces were included in the agreement. Commonalities among elements of the satellite and terrestrial radio interfaces were however sought and terrestrial/satellite commonality can be expected to further increase when the second phase of the IMT-2000 satellite component is introduced in the early part of the 21st century.

The deployment of IMT-2000 systems is foreseen to start shortly after the year 2000, subject to market considerations in the various regions around the world. To rapidly proceed with the production of all required technical documents, an unprecedented team effort will be required. To this end, close coordination between the ITU and various global partnership projects and standards-setting organizations throughout the world will be essential.

"The participants felt that this flexible approach to IMT-2000 that provides choice among multiple access methods within a single standard will address the needs of the worldwide wireless community by allowing operators to select those radio interfaces that will best address their specific regulatory, financial, and customer needs while minimizing the impact of this flexibility on the end user through careful choice of parameters such that are readily implementable in the increasingly software-defined mobile units expected to be available in the early years of the next century." said Mike Callendar, Chairman of Task Group 8/1 on the last day of the meeting.

"The work done at Fortaleza is driven by the needs of our customers for the IMT-2000 standard, which are the global operator community and the many millions of individual users around the world who will benefit from low cost wireless access to the information society in the 21st century" said Yoshio Utsumi, ITU Secretary-General. "This new wireless standard represents an unprecedented level of global cooperation to meet the diverse needs of the different ITU regions and offers the possibility to significantly narrow the telecommunications "gap" between developing and developed regions" he added.

In order to make effective use of the available frequency bands, both FDD and TDD modes of duplexing needed to be included in the IMT-2000 global standard2.

The new mobile standard thus makes it possible to:

  1. allow coexistence and interoperability between pre-IMT-2000 systems (current 2nd generation as well as initial 3G upgrades) and IMT-2000 compliant systems in order to maximize operator flexibility. This approach supports gradual evolution along converging paths that can differ from one region to another and from one operator to another. The aim is to simplify the implementation of small lightweight multi-mode multi-band terminals, for inter-system roaming on a national, regional, international and intercontinental basis through maximizing commonalities and ease of implementation of digital techniques in design and construction.

    The evolution strategy and the flexibility embodied in the decision of Task Group 8/1 means that early adopters of 3G systems will continue to be able to get voice telephony and low rate data services when roaming on today's mobile networks but will be able to take advantage of the full range of options made available by operators on their 3G networks wherever and whenever these are deployed. And carriers will have the ability to grow a new and profitable market while preserving earnings from existing services and amortizing their 2G investments.

  2. accommodate the different spectrum strategies which operators and countries may wish to adopt when deploying IMT-2000 systems. While some operators will use new spectrum for their IMT-2000 services, others will overlay IMT-2000 within spectrum already used to provide pre-IMT-2000 services in order to provide smooth migration of their customers to enhanced mobile services over a number of years without the need to obtain additional spectrum.

The more than 200 participants at Fortaleza had very little room to manoeuver. Several countries, particularly from Asia and Australasia and developing countries urged the group to agree on a single IMT-2000 standard, ideally based on one technology. That view was endorsed by many operators. Several others however stressed the need for operational flexibility to meet the varying situations around the world.

The flexible approach represented the only option on which consensus could be achieved and work could proceed. The meeting nonetheless agreed to strongly encourage the various operators fora in their efforts to achieve a minimum set of radio interfaces, covering operators needs having the least possible impact on mobile terminals so that the user is unaware of the technology which provides the services he/she has chosen, and thus meet the widely endorsed IMT-2000 objectives. The operators were also requested to provide comments on the flexibility provided in the key characteristics as approved in Fortaleza and possibly to add further information on operational scenarios that operators face around the world. Operators were also urged to convey their views to the radio transmission technologies proponents to facilitate the rapid development of the IMT-2000 recommendations.

Clearly, the next challenge will be to develop the more detailed ITU specifications in such a way as to minimize undue technical complexities or deterioration of performance while catering for multiple operating environments. There was widespread agreement for the specifications to guarantee full interoperability in spite of the inherant flexibility and be ultimately cost-effective in order to make the new standard attractive to both operators and the consumers.

"We have made a great step forward at Fortaleza but some very hard work is still ahead of us" cautioned Mr Utsumi. "It is now time for all to take a long-term view of where everyone’s interests really lie", he added. Mr Utsumi stressed that, given current forecasts on the future use of wireless systems for access to telecommunication services, IMT-2000 networks were expected not only to provide mobile communications but will also constitute a fundamental part of future telecoms networks. "In light of the glittering prize that third generation represents, divergence of strategies in bringing 3G to the marketplace is understandable" Utsumi said. "But, at the end of the day, it is the consumer that will decide on the basis of the added advantages over systems and services they already enjoy: wisdom should therefore guide us in our decisions", he concluded.

On the IPR front, on the basis of advice from the ITU Radiocommunication Bureau Director, Mr R. W. Jones, the Fortaleza meeting had decided to authorize the development of the detailed specifications to proceed on the basis of the key characteristics approved by Task Group 8/1 with the incorporation of a note warning that CDMA schemes may be subject to IPR "blockage". However, the recent announcement made by Qualcomm and Ericsson would appear to solve the IPR issue although details are awaited to reach a conclusion. Both companies, in their statement issued today, indicated they "agreed to jointly support approval by the International Telecommunication Union [...] of a single CDMA 3G standard that encompasses three optional modes of operation [...] and to commit to the ITU and to other standards bodies to license their essential patents for a single CDMA standard or any of its modes to the rest of the industry on a fair and reasonable basis free from unfair discrimination".

On the network side, another ITU group of experts (ITU-T Study Group 11), chaired by Dr Sadahiko Kano, met in Geneva and created a special group on IMT-2000 to provide better focus and faster results in mobile network standards. The aim is to match the structures and processes established elsewhere in industry fora where all aspects of mobile system network specifications are addressed in a project-oriented manner. The creation of the group is also aimed at laying the foundation for a more consolidated structure in the years to come on a comprehensive handling of IMT-2000 and other mobility services/network aspects.

The group, in addition to being responsible for all network aspects will also provide a forum where the ITU (network and radio experts) as well as interested groups that are not members of the ITU will be working cooperatively on IMT-2000 network-related standards. The Geneva meeting adopted an overall IMT-2000 network-related project plan.

The next meetings of the ITU-R Task Group 8/1 will take place in Beijing, China from 31 May to 11 June 1999, which will include a joint experts meeting with ITU-T SG 11 network experts, and in Helsinki, Finland from 25 October to 5 November 1999. The next series of meetings of ITU-T Study Group 11 will take place in Geneva from 22 November to 10 December 1999.

1 CDMA: Code division multiple access
TDMA: Time division multiple access
SDMA: Space division multiple access
2 IMT-2000 incorporates Frequency Division Duplex (FDD), with single or multi-carrier operation, as well as Time Division Duplex (TDD) operation.