POSITION STATEMENT - Wideband CDMA (WCDMA)
1. THE DECISION FOR WCDMA
On January 29, 1998, ETSI decided on WCDMA as the radio technology for the paired bands and TD/CDMA for the unpaired bands of Universal Mobile Telecommunications Services (UMTS).
In Japan, the standardisation body ARIB has opted for exactly the same WCDMA radio communications technology. This decisions has since been endorsed in the USA by the ANSI committee T1P1 - a US body with the responsibility to standardize GSM in North America.
Consequently, WCDMA is the common radio technology standard for third-generation wide-area mobile communications in both Europe, North America and Asia.
In ARIB, WDCMA is referred to as Core A. In ETSI, it is referred to as the Alpha concept. However, the technology remains exactly the same - WCDMA radio technology at 5 MHz bandwidth and specific parameters as chip rate and frame length based on an evolved GSM core network.
Moreover, the new 2 GHz frequency band has already been allocated by the ITU to third-generation services (IMT-2000) in both Europe and Asia.
In the light of the vast GSM footprint in Europe, Asia and North America - with 200 networks in operation in 110 countries and around 100 million subscribers in June, 1998 - the selection of WCDMA means there is now a common third-generation technology standard.
1.1 The Standardization Procedure
The selection of WCDMA followed an extensive and thorough standardization process. Also, the participants of these standardization bodies represent the entire global communications industry. In the process of standardizing WCDMA, all proponents were encouraged to submit their technologies. After extensive refinement and evaluation, WCDMA came out ads the preferred technology through a consensus decision. The final proposal was jointly put forward by Alcatel, Ericsson, Matsushita, Motorola, NEC, Nokia, Nothern Telecom and Siemens.
Thus, the global industry has submitted its technologies and participated in the work. All technology proponents have had an equal and fair opportunity to participate in this process and to contribute and promote their technologies.
A fair selection was then made in an open-ended process which adhered to established standardization procedures. These processes in the respective standardization bodies have all related to the establishment of 3G standards in line with the timetable required by the ITU.
1.2 Intellectual Property Rights
An integral part in the selection of any mobile communications standard is the full commitment from the industry and all its players that any IPRs that relate to the standard will be licensed on fair, reasonable and non-discriminatory terms. To facilitate WCDMA as an open-ended and truly global standard, initiatives were taken in conjunction with the January 29 ETSI decision for WCDMA to further limit any effects of potential aggregated royalties.
Any additional demands of changes to the standard after the decisions have been made are simply out of order. Furthermore, to link such demands to IPR would - in the tradition of standardization and in the spirit of creating an open global standard - be blatantly counterproductive to the interests of the entire wireless industry.
2.WCDMA TECHNOLOGY
Wideband CDMA is a completely new technology. Narrowband CDMA (IS-95) was pioneered in the USA and now Europe and Japan have selected WCDMA as their 3rd-generation standard. Naturally, the WCDMA standard is a different technology targetting 3G requirements. It has been based on extensive research conducted between 1989 and 1997.
From the start, WCDMA has been designed for high-speed data services and, more particularly, Internet-based packet-data offering up to 2 Mbps in indoor environments and over 384 kbps for wide-area.
Over a five-year period, WCDMA has been tested and verified in parallel R&D programs in both Europe and Japan. In order to achieve the necessary requirements on third-generation mobile communications, including trade-off between maximum capacity and operation in 5 MHz allocations, the so-called chip rate has been set at 4.096 MHz. This is essential in order to deliver the third-generation capabilities required by the UMTS and IMT-2000 specifications.
Furthermore the TDD component of UMTS, TD/CDMA, has been harmonized with WCDMA and thus provide efficient support for assymetric services and un-coordinated system operation in local areas, too.
WCDMA supports multiple cell layer operation in line with studies showing that two times 15-20 MHz licenses is recommended for third-generation capabilities and has thus been optimized for these requirements. Indeed WCDMA also operates in two times 5 MHz allocations by fulfilling the FCC rules. The selection of parameters, e.g. the so-called chiprate, has been made to optimise system capacity and performance in line with those requirements.
WCDMA R&D has had the advantage of including leading-edge research to optimize this new radio technology to deliver the mission-critical coverage and capacity for third-generation mobile communications. The WCDMA concept is based on a totally new channel structure for all layers (L1-L3) built on technologies such as packet-data channels and service multiplexing. The new concept also includes pilot symbols and a time-slotted structure which has led to the breakthrough features listed below:
Adaptive antenna arrays which direct antenna beams at users to provide maximum range and minimum interference. This is also crucial when implementing wideband technology where limited radio spectrum is available.
Hierarchical cell structures that allow the mix of macro and micro cells in urban areas to boost capacity.
Inter-frequency hand-off technology so that on-going calls can be handed over between carriers in different cells and frequencies.
Combining hierarchical cell structures and inter-frequency hand-off leads to a breakthrough with a new system layout that creates a very robust network.
Coherent demodulation in both uplink and downlink that maximizes range.
Complete integration of FDD, based on WCDMA, and TDD, based on TD/CDMA, technologies to offer optimum outdoor/in-door coverage and to support the complete range of services including voice, low- and high-bitrate data and assymetric services.
Independence of expensive GPS satellite systems. There is no need to synchronize WCDMA base stations through GPS positioning.
3. BACKWARD COMPATIBILITY
R&D in the early 1990s showed it would not be possible to meet third-generation requirements and still retain backward compatibility with any second-generation technology on the air-interface level. Consequently, a revolutionary solution was required.
In practice, certain key parameters in WCDMA and GSM have been harmonized in order to achieve an optimal solution for dual-mode GSM/UMTS terminals as well as GSM/UMTS hand-over.
This will facilitate today's users easy access to third-generation services through dual-mode terminals - as will be the case with UMTS/GSM terminals.
The R&D work invested into WCDMA in combination with the ETSI/ARIB/ANSI decisions mean there is now a unique opportunity to achieve a world standard that must not be lost.
Although an international co-operation between different standards organizations is very challenging, the ETSI-ARIB dialogue has been a very positive experience mainly because of the mutually shared goals. Now both groups are working hard to find a more efficient way how to proceed in their co-operation towards a global 3rd generation system and not only a common air interface. To achieve the global coverage in the standards work the relevant US organizations ANSI/TIA/T1P1 have coupled their efforts to these discussions as well. The first round of these trilateral talks was held in Tokyo in February 1998.
Furthermore, the groundwork to achieve a technical standard which can be deployed in all continents has been initiated by ETSI. The standardization body has already agreed that UMTS will fulfill FCC requirements to allow WCDMA to operate even in 2 times 5 MHz FDD spectrum to suit the North American environment.
3.1 Demands for Changes
There have been proposals to alter the chip rate of the agreed ETSI/ARIB/WCDMA concept to cater for backward compatibility with narrowband CDMA (IS-95). This run counter to the objectives with both UMTS and IMT-2000 and was therefore been disregarded since such alterations would dilute system capacity and performance.
In short, the consequence of the proposal would have been to eliminate the third-generation capabilities of WCDMA, such as hierarchical cell structures, inter-frequency hand-off capabilities and adaptive antenna arrays, etc (see above). The solution to backward compatibility remains dual-mode terminals.
Likewise, other initiatives to seek harmonization by comparing technical solutions from wbcdmaOne and WCDMA have been conducted. Most important was a study in ARIB (Ah-S group), initiated by proposals from wbcdmaOne proponents. These studies were concluded February 1998.
The outcome of these studies have been incorporated into the ETSI/ARIB WCDMA standard. Thus, there has been plenty of opportunity to discuss various technical solutions based on their respective merits in the due work process on more than one occasion already.
In line with the schedule for introduction of 3rd-generation services the detailed specification and implementation process should not be interrupted or delayed by activities not belonging to the process of the global industry.
Under any circumstances, IS-95/IS 41 and UMTS/evolved GSM technologies rely on different network technologies. The "GSM world" does not benefit from backward compatibility to the IS-95 air interface; thus, the chip rate harmonization does not offer any additional benefits to them.
In addition, in Americas the frequency allocation is different compared to the rest of the world and wbcdmaOne is planning to use so called multicarrier technology in the downlink in that market area. In WCDMA direct spreading technology is a global solution.
Technologies considered for wbcdmaOne are related to different elements of backward compatibility to IS-95, this limits the flexibility. This has led to fundamental limitations to wbcdmaOne as compared to WCDMA, especially with respect to its capabilities to support 3rd-generation capabilities. Some examples are:
Support of adaptive antennas can not be made with the same performance due to the common pilot channel structure used in wbcdmaOne.
wbcdmaOne channel format makes power control less efficient.
wbcdmaOne can not operate without external (GPS) synchronization.
wbcdmaOne do not support interfrequency handover, meaning that hierarcical cell structure and handover to second generation systems can not be performed.
wbcdmaOne do not efficiently support bit-rate and service flexibility.
wbcdmaOne do not have an integral TDD mode that supports un-coordinated local area operation.
It is also important to empasise that WCDMA have taken into account all the latest research on providing third generation capabilities into this newly developed standard. Wereas wbcdmaOne, with its backward compatibilities to IS-95, are hamstrung by backward compatibility with older, 2nd-generation CDMA technology. In addition, WCDMA is more mature, well-developed than wbcdmaOne and it has been tested in the field.
We therefore see that the only viable way to achieve a world standard is to build on the agreed ETSI/ARIB standard and retain its inherent third-generation capabilities. Adapting the WCDMA radio technology by the TIA for IS-41-based networks in the USA and elsewere - based on the same dual-mode functionality as in the case of UMTS/GSM - would provide third-generation capabilities to all mobile communications' operators and end users in the USA that the rest of the world will enjoy.
Last updated: 980629
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