Mobile telecommunication systems provide roaming service which allows calls to be made using different network operators in different geographic areas.This paper presents a study on internetwork signalling protocol architecture for PHS roaming. It's based on the distributed functional plane model for IN CS1 defined by ITU-T SG 11. The network capabilities, internetwork procedures and protocol structure for the roaming service are discussed, and the data model is proposed.
I. INTRODUC~IONMany mobile telecommunications systems provide roaming service [3]. The roaming service is a service that enables users to receive basic services from multiple network operators in different service areas. To provide the roaming service, internetwork interfaces and radio interfaces for user access must be standardized. In this paper we propose a signalling protocol architecture between PHS networks.
ASSUMPTIONS FOR NETWORK FUNCTIONAL ARCHITEWREBefore we can study the signalling protocol architecture between PHS networks, we need to understand network functional architecture (e.g., network functional allocation and functional models).
A. Nehvork Functional AllocationThe PHS currently uses three different network architectures in Japan. However, for our purposes, we assume that the PHS network has all the functions for PHS[4] shown in Fig. 1. These environments are the same as those provided by the current public land mobile network, and in this paper we focus on the interface between PHS networks. .radio resource control .radio resource control .(location) registration .(location) registration *supplementmy service *supplementary service Fig. 1. Interface in this paper. B. Functional Model and Signalling Protocol PHS can provide telecommunication services economically by using more advanced functions of the current network. Both the functional model and the signalling protocol for PHS roaming service should be based on the international standards for both Universal Personal Telecommunications (UPT)[51[9] and the intelligent network (IN)[6]. Study Group (SG) 1 1 in ITU-T has been studying the concepts of capability set for he standardization of IN. In 1995, SG11 made their recommendation in IN Capability Set 1 (IN CS1)[7][8] and began studying IN CS2. As far UPT, SG 1 has produced UPT service definitions[9], and SG 11 has come up with service procedures[5] based on IN CS 1.We use IN CSI as functional model for our internetwork interface between the service control function (SCF) and the service data function (SDF). This paper focuses on internetwork interface for PHS roaming.How roaming subscription data is managed influences network functional allocation and the functional models. Data can be managed by using the visitor location register (VLR). In VLR, the visited network (where roaming terminal visits) manages the data for the terminal during the visit. Data can be also managed by using the home location register (HLR). In this method the visited network gets data for the roaming terminal from the home network with which the roam...
