Intelligent Network Services in Migration from PSTN toward NGN Mahmoud Saeidi, Mahmoud Pirhadi, Fattaneh Ayazi Iran Telecommunication Research Center Tehran, Iran msaeidi40@itrc.ac.ir , pirhadi@itrc.ac.ir , f_ayazi@itrc.ac.ir Abstract  In this paper we will propose two new scenarios for two IN services when migrating from Public Switched Telephone Network, PSTN toward Next Generation Network, NGN. Next Generation Network is one of the promising Networks in near future. Because of huge amount of investment on PSTN, the migration towards NGN implementation would be instant step by step and gradual not an instant replacement. . Therefore, we need to plan the interfaces between PSTN and NGN in order to convert data and signalling. By applying Intelligent Network services in PSTN, IN services scenarios will be changed while migrating to NGN. We assume that IN equipment is located in PSTN. We will propose two novel scenarios when users located in NGN request card calling and free phone Services. Keywords  Next Generation Network, Intelligent Network, Migration to NGN, Card Calling Service, Free Phone Service 1. Introduction With the increasing demand of the telephone services and wide variety of those services, the traditional telephone networks, composed of numerous interconnected switches, are not able to catch up with such a demand. Each demanded service must be implemented in every switch with the exactly same signaling protocols. During the development and maintenance, the coordination of different types of switches would be extremely difficult if not impossible. In other words, introducing new services in the Public Switched Telephone Network (PSTN) is a difficult process, as it requires the development from scratch and the modification of software of switches which are spread all over the network. To deal with this difficulty, communication operators have to evolve from hard coded switches to dynamically configurable distributed systems. Therefore a new architecture called Intelligent Network [1] was defined by ITU-T. The need of an intelligent service layer above the traditional transport layer to provide various kinds of value-added services is obvious. This layer of networks is called intelligent networks, IN. The IN is based on a simple principle: the service specific software is separated from the Basic Call Processing and is run on a specialized node This node is called the Service Control Point (SCP), while the switches are called Service Switching Point (SSP). The Service Management System (SMS) contains management functions of the IN systems. The Service Data Point (SDP) is a database that holds information related to the service. SDP could be either separated from SCP or loaded on SCP. Some of the IN services are Free Phone Service, Card Calling Service, Number Portability Service, Premium Rate Service, Universal Access Number Service, Universal Personal Communication Service, Televoting Service, Virtual Private Service and etceteras. There are different scenarios for them. These scenarios include exchanging INAP message among SSP, SCP and SDP. In these scenarios, the calling party and the called party are in PSTN. In other words, exchanging data and signaling is done by circuit-switched network. Many operators are now migrating their PSTNs from circuit switched network toward the packet-switched network paradigm. This new approach is often called the Next Generation Network (NGN). The term NGN is commonly used for changes in network infrastructure that have already started in the telecom and information technology (IT). As such, it is not a term that can be precisely defined but is rather an umbrella term that varies among individuals, vendors, and literature. The NGN enables network operators to run all services (i.e. voice, data and video) on a single network. The NGN concept is based on packet-based nodes called Media Gateways (MGs). Media Gateways take over the functionality of the switching hierarchy in the current PSTN system [2], [3]. The Intelligent Network concepts are very relevant to Next Generation Networks, and may provide a bridge from current telephony features to the new IP based network. In section 2 we describe the conceptual model of IN services. In section 3 we describe IN architecture. In section 4, IN Services Deployed in migration from PSTN to NGN is described. In addition, in this section we will propose two novel different scenarios for two IN requested service, Card Calling and Free Phone when migrating from PSTN to NGN. 2. IN Conceptual Model (INCM) [4] The INCM is composed of four planes, each representing a different abstract view of IN networks. According to Fig. 1, at the topmost level we have Service Plane, which describes services from user’s point of view. Service plane consists of different service features. Each service is composed of number of these features. CS-1implements 25 services using 38 service features. Also, CS-2 implements 60 services using 62 service features. Next plane is Global Functional Plane (GFP), which looks at services from the service provider’s viewpoint. ISBN 89-5519-129-4 - 265 - Feb. 20-22, 2006 ICACT2006