The historic agreement reached at January's ETSI SMG meeting in Paris will enable Europe and Japan to progress with the development of UMTS - the Third Generation mobile communications technology.

After months of discussion, the supporters of the W-CDMA and TD-CDMA proposals agreed to join forces to develop a solution which combines elements of both concepts. The decision to work together came after a further inconclusive vote at the special SMG meeting when it became apparent that the TD-CDMA camp did not have the votes to win the battle. Top executives from the rival parties met behind closed doors for a long evening of tough bargaining before hammering out a compromise solution which was approved unanimously by the SMG plenary on January 29.

Pressure for a compromise had been building since the indicative vote at the SMG meeting in December 1997. The majority of operators had made it clear that they wanted an agreement on a single air interface standard in order to promote competition and achieve economies of scale and that they strongly favored the W-CDMA solution. SMG chairman Fred Hillebrand spent January talking to the different players in an effort to achieve a compromise and there were also a number of key meetings between individual vendors. At the back of everyone's mind was the concern that failure to agree on a single air interface could jeopardize all the gains made through the global success of GSM.

The concept agreed by the two groups combines both Frequency Division Multiplex (FDD) and Time Division Multiplex (TDD) technologies. The frequency spectrum allocated for UMTS is in two parts; paired and unpaired. In the paired band the proposed specification will utilize FAD, the radio access technique proposed by the Ericsson and Nokia grouping. In the unpaired band the UMTS system uses the TDD access techniques contained in the TD-CDMA solution proposed by the UMTS Alliance. The introduction of TDD to the W-CDMA concept enables the development of a technology which can meet all the needs of the operators. Wideband CDMA will be used for the cellular wide area coverage, high mobility service, and TD-CDMA for low mobility, local in-building services, asymmetric data transmission and wireless office type applications such as those supported by the GSM CTS proposals and digital cordless technologies.

The agreement covers a number of key issues and defines the requirements of the new air interface. These requirements are that it must: enable the development of low cost terminal units; be compatible with GSM; harmonize the FDD and TDD elements to enable dual mode operation; and be able to operate in 2 x 5MHz of spectrum in order to support US GSM-based PCS operators. All the parties involved will now begin the long and difficult process of turning the FDD/TDD concept into a real specification, a process that is expected to take two years.

There will undoubtedly be difficult IPR issues although all the vendors have promised to co-operate to resolve any problems. In a joint state-ment, Alcatel, Bosch, Ericsson, Italtel, Motorola, Nokia, Siemens and Sony said they would work together to provide "agreed guidelines for the handling of IPRs essential to the UMTS air inter-face specification which result in reasonable cost for the manufacturers".

Perhaps the most significant aspect of the proposed new air interface is that it is supported by the Japanese players. Representatives from ARIB, the Japanese standards body, NTT DoCoMo and major Japanese manufacturers were observers at the SMG plenary and have pledged their support for the new concept.

The compromise solution was warmly welcomed by other key players. Dr Adriana Nugter, chairman of the GSM MoU Association says: "I congratulate the industry on reaching agreement in the form of a combined proposal. This now sets a working basis to define standardization and means that we can now move forward. We are very happy with this agreement." Thomas Beijer, UMTS Forum chairman was equally enthusiastic. "I wholeheartedly welcome this agreement and congratulate the competing manufacturers who have shown a constructive attitude in reaching a consensus and agreeing a framework for the next phase of detailed standardization in a spirit of co-operation." Summing up the overall view of this historic decision, Hillebrand says: "We can now go forward and build on the success of GSM. This is a major step towards this end."