Η παρούσα διπλωματική εργασία είναι η υλοποίηση σε λογισμικό του Home Subscriber Server (HSS). Ο HSS είναι ένας εξυπηρετητής ζωτικής σημασίας για το IP Multimedia Subsystem (IMS). Αποτελεί την κύρια βάση του δικτύου που περιέχει σημαντικές πληροφορίες για τους χρήστες και επιτελεί, μαζί με κάποιες άλλες οντότητες,την πιστοποίηση και την εξουσιοδότηση των χρηστών, που επιθυμούν να χρησιμοποιήσουν το IMS δίκτυο. / This thesis is the software implementetion of a Home Subscriber Server (HSS). The HSS is a server vital for IP Multimedia Subsystem (IMS). It is the main basis of the network which contains important information for users and it performs, along with some other entities, certification and authorization of users who wish to use the IMS network.

Next generation heterogeneous wireless networks are expected to interwork with Internet Protocol (IP)-based infrastructures. Conventional network services operate like silos in that a specific set of services are offered over a specific type of access network. As access networks evolve to provide IP-based packet access, it becomes attractive to break these “service silos” by offering a converged set of IP-based services to users who may access these services using a number of alternative access networks. This trend has started with third generation cellular mobile networks, which have standardized on the use of the IP Multimedia Subsystem (IMS) to manage user access to a wide variety of multimedia services over the mobile Internet, while facilitating interworking of heterogeneous wireless and landline access networks. The future users of communication systems will subscribe to both IP-based and Circuit Switched (CS) based services and in the foreseeable future a single database that handles user profiles across all domains will be required. Home Subscriber Server (HSS) as an evolved version of Home Location Register (HLR) is one of the key components of IMS. In deploying HSS as a central repository database, in a fully overlapped heterogeneous network setting, changes of access mode are very frequent and conveying this information to HSS imposes excessive signaling load and delay. In our proposed scheme we introduce an Interface Agent (IA) for each location area that caches the location and information about the access mode through which a user can be reached. This method results in significant amount of savings in signaling cost and better delay performance. The existing call delivery approaches in cellular networks may not be well suited for future communication systems because they suffer from unnecessary usage of network resources for call attempts that may fail which adds to excessive signaling delays and queuing costs. Reducing the number of queries and retrievals from the database will have a significant impact on the network performance. We present a new scheme based on Reverse Virtual Call setup (RVC) as a solution to the call delivery problem in heterogeneous wireless networks and evaluate the performance of this framework.

Next generation heterogeneous wireless networks are expected to interwork with Internet Protocol (IP)-based infrastructures. Conventional network services operate like silos in that a specific set of services are offered over a specific type of access network. As access networks evolve to provide IP-based packet access, it becomes attractive to break these “service silos” by offering a converged set of IP-based services to users who may access these services using a number of alternative access networks. This trend has started with third generation cellular mobile networks, which have standardized on the use of the IP Multimedia Subsystem (IMS) to manage user access to a wide variety of multimedia services over the mobile Internet, while facilitating interworking of heterogeneous wireless and landline access networks. The future users of communication systems will subscribe to both IP-based and Circuit Switched (CS) based services and in the foreseeable future a single database that handles user profiles across all domains will be required. Home Subscriber Server (HSS) as an evolved version of Home Location Register (HLR) is one of the key components of IMS. In deploying HSS as a central repository database, in a fully overlapped heterogeneous network setting, changes of access mode are very frequent and conveying this information to HSS imposes excessive signaling load and delay. In our proposed scheme we introduce an Interface Agent (IA) for each location area that caches the location and information about the access mode through which a user can be reached. This method results in significant amount of savings in signaling cost and better delay performance. The existing call delivery approaches in cellular networks may not be well suited for future communication systems because they suffer from unnecessary usage of network resources for call attempts that may fail which adds to excessive signaling delays and queuing costs. Reducing the number of queries and retrievals from the database will have a significant impact on the network performance. We present a new scheme based on Reverse Virtual Call setup (RVC) as a solution to the call delivery problem in heterogeneous wireless networks and evaluate the performance of this framework.

Next generation heterogeneous wireless networks are expected to interwork with Internet Protocol (IP)-based infrastructures. Conventional network services operate like silos in that a specific set of services are offered over a specific type of access network. As access networks evolve to provide IP-based packet access, it becomes attractive to break these “service silos” by offering a converged set of IP-based services to users who may access these services using a number of alternative access networks. This trend has started with third generation cellular mobile networks, which have standardized on the use of the IP Multimedia Subsystem (IMS) to manage user access to a wide variety of multimedia services over the mobile Internet, while facilitating interworking of heterogeneous wireless and landline access networks. The future users of communication systems will subscribe to both IP-based and Circuit Switched (CS) based services and in the foreseeable future a single database that handles user profiles across all domains will be required. Home Subscriber Server (HSS) as an evolved version of Home Location Register (HLR) is one of the key components of IMS. In deploying HSS as a central repository database, in a fully overlapped heterogeneous network setting, changes of access mode are very frequent and conveying this information to HSS imposes excessive signaling load and delay. In our proposed scheme we introduce an Interface Agent (IA) for each location area that caches the location and information about the access mode through which a user can be reached. This method results in significant amount of savings in signaling cost and better delay performance. The existing call delivery approaches in cellular networks may not be well suited for future communication systems because they suffer from unnecessary usage of network resources for call attempts that may fail which adds to excessive signaling delays and queuing costs. Reducing the number of queries and retrievals from the database will have a significant impact on the network performance. We present a new scheme based on Reverse Virtual Call setup (RVC) as a solution to the call delivery problem in heterogeneous wireless networks and evaluate the performance of this framework. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

This Master’s thesis deals with IMS architecture problems. This thesis describes its creation and progress, also structure of this architecture is mentioned. Text of this thesis describes function of the most important parts of the architecture, such as Proxy-CSCF, Interrogating-CSCF, Serving-CSCF and HSS. IMS architecture uses SIP protocol for establishment, maintenance and closing session and Diameter protocol for network management functions. That is why this thesis also describes characteristics of these two protocols. Next part of the thesis is focused on Open-source platform Open IMS Core and its installation. Open IMS Core platform was developed for testing IMS technologies within an internal project at the Fraunhofer Institute FOKUS in Berlin. Nowadays it is used by major part of vendors and providers for testing their products and services. As a main theme of this thesis, there was made a simple network, which consists of three users. This network is established on fundamentals of IMS and it was made in Open IMS Core. So in one chapter is outlined a process of its creation. There is described a process of adding a user list to database server HSS. In the next part there are mentioned some information about setup of virtual IMS terminal. Eventually there are shown some possibilities of how to catch traffic in the network. In this chapter there are also state diagrams, which describe a process of registration of IMS terminal and also a process of establishment, maintenance and closing session.