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The 4th Generation Telephony Concept

The projects page lists the various projects the the NTRG is currently involved in.

Staff, Postgraduates, Undergraduates and NTRG Alumni

Resources for 4BA2, 1ICT1 and 3ICT1 undergraduate courses.

Papers, Technical reports and presentations

Some links to telecommunications, e-commerce and cryptography resources.

Much of the dynamism present in the telephony industry today has stemmed from mobile telephony. The first generation of mobile telephones were based on analogue technology and were relatively unsophisticated. The second generation systems involved digital technology. Perhaps the most successful of these is the Global System for Mobile (GSM) Communications.

Applied research is now taking place aimed at defining standards for the 3rd generation mobile systems. At a European level, this is referred to as the Universal Mobile Telecommunications Systems (UMTS) and the global standardization effort undertaken by the ITU is called IMT-2000. The direction of this research is to evolve today's circuit switched core network to support new spectrum allocations and higher bandwidth capability. Efforts are also being made to integrate the many diverse mobile environments in addition to blurring the distinction between the fixed and mobile networks.

4th generation telephony supports broadly similar goals to the 3rd generation effort but starts with the assumption that future networks will be entirely packet-switched using protocols evolved from those in use in today's Internet. Today's internet telephony systems are the forerunner of the applications that will be used in the future to deliver telephony services.


Among the major benefits of the 4th generation approach are the following: 

  • The (long-awaited) achievement of voice-data integration
  • A single, simple technology supporting mobile and fixed networking
  • Enhanced services through the use of simple networks with intelligent terminal devices
  • A flexible method of payment for network connectivity that will support large number of network operators in a highly compeditive environment.

    Research Issues

    Before the promise of 4th generation systems can be delivered, a number of research issues must be resolved. These include: 

    Naming and Addressing
    Users will need to identify themselves and register for services - they may do this use a range of different identities. Computability with existing systems e.g. Telephone Number (E.164), IMSI, IMUN, IP Address, E-mail address must be considered.

    Directory Services
    Directory services will be required to map from a users identity to a routable network address to which the call can be delivered. In 4th generation systems, all users will be treated as being mobile, and will thus roam from one network point on another.

    Mobility Support
    In cases where users are using wireless networks to avail of services, it will be possible for users to change location while calls are active. Support must be provided to allow for handoff, and maintenance of the call state.

    Quality of Service (QoS) Support)
    In order to deliver a quality voice stream across a packet switched network, efforts must be made to control network QoS factors such as end-to-end delay, packet loss and jitter. One technique that can address the delay issue is our Smart IP Switching.

    The packet switched networks of the future will reflect the structure of today's Internet. That is, they will be made up of interconnected islands of infrastructure owned by competing commercial concerns. The architecture underlying the deliver of telephony services can be simplified using Real-Time payment systems.

    Wireless Channel Access
    The majority of protocols developed for MAC control on wireless links have focused on providing a circuit switched service - adaptation will be required for efficient support of 4th generation services.

    Ongoing Project Work

    Within the  Network and Telecommunications Research Group , a number of efforts are being made to address the above issues. Our telephony testbed application is called  NOMAD. It currently supports calls across UDP, RTP and Native ATM links. Directory support is available based on customized LDAP services. Multi-party payment methods based on adapted micropayment systems are under development.

    4th Generation Publications

    Some of the groups recent publications on topics related to 4th Generation Telephony are listed below.

    O'Mahony, D., Universal Mobile Telecommunications Systems : The fusion of fixed and mobile networks, IEEE Internet Computing, Vol. 2, No. 1, January/February 1998, pp 49-56

    Lloyd, D. & O'Mahony, D., Smart IP Switching : A Hybrid System for Fast IP-based Network Backbones, in proceedings of the 1st IEEE International Conference on ATM - ICATM'98, June 22-24, 1998, Colmar, France, pp 500-506

    O'Mahony, D., Doyle, L., Tewari, H. and Peirce, M., NOMAD - An Application to Provide UMTS Telephony Services on Fixed Terminals in COBUCO , in Proceedings of the 3rd ACTS Mobile Communications Summit, Rhodes, Greece, June 8th-10th, 1998, pp 72-76

    OMahony, D., Peirce, M. and Tewari, H., Electronic Payment Systems, Artech House, Boston, 1997, 250pp

    O'Mahony, D. & Lloyd, D., The Role of Smart IP Switching in 4th Generation Telephony, in Proceedings of Multi-Service Networks '98, Cosener's House, Rutherford-Appleton Laboratories, August 6-7th, 1998.

    Media Snippets

    CableLink Interview - Note that this file is very large and may take sometime to download

    Future Tense, RTÉ Radio One's weekly science show had an item about the work being carried out at the NTRG. You can download the item in three audio formats:


    Internet Telephony Links
  • Last Modified 17 June 2000. URL: http://ntrg.cs.tcd.ie/index.html Donal.OMahony at cs.tcd.ie