Inter-segment handover algorithm for an integrated terrestrial/satellite-UMTS environment

The third generation of mobile telecommunications, known in Europe as the Universal Mobile Telecommunications System (UMTS), is envisaged to consist of an integrated satellite and terrestrial network. The focal point of this integration is to enlarge and complete service coverage, and in so doing, provide the mobile user with the ability for global roaming. In such an environment, a dual-mode terminal will enable service continuity by handing over the call from one network to another whenever necessary. This type of handover is called inter-segment handover (ISHO). Within the European Commission´s Advanced Communications, Services and Technologies (ACTS) programme, the SINUS (Satellite Integration into Networks for UMTS Services) project is investigating a number of issues relating to a terrestrial/satellite-UMTS environment. One of the issues investigated is the derivation of an optimum ISHO handover approach and the implementation of the algorithm and subsequent performance evaluation in the SINUS test-bed. This paper provides a description of the handover algorithm developed in SINUS and presents the approach chosen for the implementation of the ISHO protocol in the SINUS test-bed. Different strategies for ISHO are discussed and the criteria used to choose the most appropriate one are given. The functional model of the chosen handover algorithm is presented and is mapped onto the functional architecture of the SINUS system. According to this mapping, the information flow of the handover protocol is described. Finally, the development approach of the protocol, based on the Generic Radio Access Network (GRAN) concept, is discussed