Bisnd Essay, Research Paper
Date sent: Sat, 27 Apr 96 17:56:40 0100INTEGRATION OF UMTS AND B-ISDN – IS IT POSSIBLE OR DESIRABLE?INTRODUCTIONIn the future, existing fixed networks will be complemented bymobile networks with similar numbers of users. These mobileusers will have identical requirements and expectations to thefixed users, for on-demand applications of telecommunicationsrequiring high bit-rate channels. It will be necessary forthese fixed and mobile networks to interoperate in order topass data, in real time and at high speeds, between theirusers. But how far must this interoperation be taken? How muchintegration of the fixed and mobile network structures isneeded? Here, a fixed network, B-ISDN, and a mobile network,UMTS, under development at the same time, are examined to seehow well and closely they should work together in order tomeet expected user needs. Work already taking place on this isdiscussed. BACKGROUNDThe Universal Mobile Telecommunication System (UMTS), the thirdgeneration of mobile networks, is presently being specified aspart of the European RACE technology initiative. The aim ofUMTS is to implement terminal mobility and personal mobilitywithin its systems, providing a single world mobile standard. Outside Europe, UMTS is now known as International MobileTelecommunications 2000 (IMT2000), which replaces its previousname of Future Public Land Mobile Telecommunication System(FPLMTS). [BUIT95]UMTS is envisaged as providing the infrastructure needed tosupport a wide range of multimedia digital services, orteleservices [CHEU94], requiring channel bit-rates of lessthan the UMTS upper ceiling of 2 Mbits/second, as allocated toit in the World Administrative Radio Conference (WARC) ‘92bands. UMTS must also support the traditional mobile servicespresently offered by separate networks, including cordless,cellular, paging, wireless local loop, and satellite services. [BUIT95] Mobile teleservices requiring higher bit rates, from2 to 155 Mbits/second, are expected to be catered for byMobile Broadband Services (MBS), the eventual successor toUMTS, which is still under study. [RACED732]Broadband Integrated Services Digital Network (B-ISDN),conceived as an all-purpose digital network that willsupersede Narrowband ISDN (N-ISDN or ISDN), is also stillbeing specified. B-ISDN, with its transport layer ofAsynchronous Transfer Mode (ATM) is expected to be thebackbone of future fixed digital networks. [MINZ89]It is anticipated that, by the year 2005, up to 50% of allcommunication terminals will be mobile. [CHEU94] The MobileGreen Paper, issued by the European Commission in 1994,predicts 40 million mobile users in the European Union by2000, rising to 80 million by 2010. This gives mobile users animportance ranking alongside fixed-network users. [BUIT95]One result of this growth in mobile telecommunications will bethe increase in teleservice operations that originate ineither the fixed or mobile network, but terminate in theother, crossing the boundary between the two. UMTS is expectedto be introduced within the next ten years, and integrationwith narrowband and broadband ISDN is possible in this time. Interoperability between UMTS and ISDN in some fashion will benecessary to support the interoperability between the fixedand mobile networks that users have already come to expectwith existing mobile networks, and to meet the expectation ofconsistency of fixed/mobile service provision laid out in theinitial RACE vision. [SWAI94]One way of making UMTS attractive to potential customers is tooffer the same range of services that B-ISDN will offer,within the bounds of the lower 2 Mbits/second ceiling of UMTS. [BUIT95]So, with the twin goals of meeting existing expectations andmaking UMTS as flexible as possible to attract customers, howclosely integrated must UMTS be with B-ISDN to achieve this?ALTERNATIVES FOR INTEGRATING UMTS WITH OTHER NETWORKSThe UMTS network could be developed along one of the followingalternative integration paths:1. Developing an ‘optimised’ network structure and signalling protocols tailored for the special mobile requirements of UMTS. This would be incompatible with anything else. Services from all fixed networks would be passed through via gateways. This design-from-scratch method would result in highly efficient intra-network operation, at the expense of highly inefficient inter-network operation, high development cost, scepticism relating to non-standard technology, and slow market take-up. True integration with fixed networks is not possible in this scenario. Given the drawbacks, this is not a realistic option, and it has not been considered in depth. One of the RACE goals was to design UMTS not as a separate overlay network, but to allow integration with a fixed network; this option is undesirable. [BUIT95]2. Integration with and evolution from the existing Global System for Mobile telecommunication. (GSM, formerly standing for Group Special Mobil during early French-led specification, is now taken as meaning Global System for Mobile communications by the non-French-speaking world.) GSM is currently being introduced on the European market. This option has the advantage of using already-existing mobile infrastructure with a ready and captive market, but at the expense of limiting channel bit-rate considerably, which in turn limits the services that can be made available over UMTS. Some of the technical assumptions of UMTS, such as advanced security algorithms and distributed databases, would require new protocols to implement over GSM. GSM would be limiting the capabilities of UMTS. [BROE93a]3. Integration with N-ISDN. Like the GSM option above, this initially limits UMTS’s channel bit-rate for services, but has a distinct advantage over integration with B-ISDN – N-ISDN is widely available, right now. However, integrating UMTS and N-ISDN would require effective use of the intelligent network concept for the implementation of mobile functions, and modification to existing fixed network protocols to support mobile access. Integrating UMTS with N-ISDN makes possible widespread early
introduction and interoperability of UMTS in areas that do not yet have B-ISDN available. This allows wider market penetration, as investment in new B-ISDN equipment is not required, and removes the dependency of UMTS on successful uptake of B-ISDN for interoperability with fixed networks. Eventual interoperability with B-ISDN, albeit with constrictions imposed on UMTS by the initial N-ISDN compatibility, is not prevented. [BROE93a]4. Integration with B-ISDN. This scenario was the target of MONET (MObile NETwork), or RACE Project R2066. Unlike the above options, B-ISDN’s high available bandwidth and feature set does not impose limitations on the service provisioning in UMTS. Fewer restrictions are placed on the possible uses and marketability of UMTS as a result. Development of B-ISDN is taking place at the same time as UMTS, making smooth integration and adaptation of the standards to each other possible. For these reasons, integration of UMTS with B-ISDN has beenaccepted as the eventual goal for interoperability of futurefixed and mobile networks using these standards, and thisintegration has been discussed in depth. [BROE93a, BROE93b,BUIT95, NORP94]At present, existing B-ISDN standards cannot support themobile-specific functions required by a mobile system likeUMTS. Enhancements supporting mobile functions, such as callhandover between cells, are needed before B-ISDN can act asthe core network of UMTS. Flexible support of fixed, multi-party calls, to allow B-ISDNto be used in conferencing and broadcasting applications, hasmany of the same requirements as support for mobile switching,so providing common solutions to allow both could minimise thenumber of mobile-specific extensions that B-ISDN needs. As an example of how B-ISDN can be adjusted to meet UMTS’sneeds, let’s look at that mobile requirement for support forcall handover. Within RACE a multiparty-capable enhancement ofB-ISDN, upwardly compatible with Q.2931, has already beendeveloped, and implementing UMTS with this has been studied. For example, a UMTS handover can be handled as a multi-partycall, where the cell the mobile is moving to is added to thecall as a new party, and the old cell is dropped as a partyleaving the call, using ADD(_party) and DROP (_party)primitives. Other mobile functions can be handled by similaradaptations to the B-ISDN protocols. The enhancements to B-ISDN Release 2 and 3 that are requiredfor UMTS support are minimal enough to be able to form anintegral part of future B-ISDN standards, without impacting onexisting B-ISDN work. [BUIT95]These modifications only concern high-level B-ISDN signallingprotocols, and do not alter the transport mechanisms. Theunderlying ATM layers, including the ATM adaptation layer(AAL) are unaffected by this. THE INTELLIGENT NETWORKThe Intelligent Network (IN) is a means for service providersto create new services and rapidly introduce them on existingnetworks. As the IN was considered useful for implementingmobility procedures in UMTS, it was studied as part of MONET,and is now specified in the Q.1200 series of the ITU-Trecommendations. The intelligent network separates service control and servicedata from basic call control. Service control is thenactivated by ‘trigger points’ in the basic call. This meansthat services can be developed on computers independent of thenetwork switches responsible for basic call and connectioncontrol. This gives flexibility to the network operators andservice providers, as well as the potential to support theservices on any network that supports the trigger points. Eventually, IN can be expanded to control the network itself,such as handling all UMTS mobile functions. [BROE93a]Any network supporting the intelligent network service setwill be able to support new services using that service seteasily, making integration of networks easier and transparentto the user of those services. The intelligent network is thusan important factor in the integration of B-ISDN and UMTS. UMTS, B-ISDN and the intelligent network set are all beingdeveloped at the same time, allowing each to influence theothers in producing a coherent, integrated whole. [BUIT95]CONCLUSIONIn order to be accepted by users as useful and to provide aswide a variety of services as possible, UMTS needs some formof interoperabilty or integration with a fixed network. Integration of UMTS with B-ISDN offers the most flexibility inproviding services when compared to other network integrationoptions, and constrains UMTS the least. With the increase in the number of services that will be madeavailable in UMTS and B-ISDN over present standalone services,it is unrealistic to develop two separate, and incompatible,versions of each service for the fixed and mobile networks. Integrating UMTS and B-ISDN makes the same service setavailable to both sets of users in the same timescale,reducing development costs for the services, and promotinguptake and use in the market. The intelligent network conceptallows the easy provision of additional services with littleextra development cost. Integrating UMTS with B-ISDN, and withthe intelligent network set, is therefore desirable. Work on this integration indicates that the mobilerequirements of UMTS can be met by extending existing B-ISDNsignalling to handle them, without significantly modifyingB-ISDN. Integration of UMTS with B-ISDN is thereforetechnically feasible. REFERENCES[BROE93a]W. van den Broek, A. N. Brydon, J. M. Cullen, S. Kukkonen,A. Lensink, P. C. Mason, A. Tuoriniemi,”RACE 2066: Functional models of UMTS and integration intofuture networks”,IEE Electronics and Communication Engineering Journal, June1993. [BROE93b]W. van den Broek and A. Lensink,”A UMTS architecture based on IN and B-ISDN developments”,Proceedings of the Mobile and Personal CommunicationsConference, 13-15 December 1993. IEE Conference Publication 387. [BUIT95]E. Buitenwerf, G. Colombo, H. Mitts, P. Wright,”UMTS: Fixed network issues and design options”,IEEE Personal Communications, February 1995. [CHEU94]J. C. S. Cheung, M. A. Beach and J. P. McGeehan,”Network planning for third-generation mobile radio systems”,IEEE Communications Magazine, November 1994. [MINZ89]S. E. Minzer,”Broadband ISDN and Asynchronous Transfer Mode (ATM)”,IEE Communications Magazine, September 1989. [NORP94]T. Norp and A. J. M. Roovers,”UMTS integrated with B-ISDN”,IEEE Communications Magazine, November 1994. [RACED732]IBC Common Functional Specification, Issue D. Race D732: Service Aspects. [SWAI94]R. S. Swain,”UMTS – a 21st century system: a RACE mobile project lineassembly vision”END.