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seamlEss multimedia serVices Over alL IP-based infrastrUcTurEs


The SIM Access Gateway (SAG) is a state-of-the-art gateway platform that performs mapping of the authentication and authorisation mechanisms from a WLAN environment on the corresponding mechanisms of a mobile network for terminals with SIM cards accessing a WLAN environment. Its role is to act as a AAA server for the WLAN environment for SIM based users. Its Authentication functionality is based on the transfer of 2G (GSM or GPRS) authentication material from a core network HLR. The authentication functionality can be extended easily to cover USIM based users by the addition of an extra EAP-AKA module similar to the EAP-SIM one as far as the WLAN interface of SAG is concerned. Regarding the MAP/SS7 interface with the HLR the implemented MAP protocol at SAG supports transfer of UMTS Authentication Quintuplets apart form the GSM Triplets and therefore it can easily provide the appropriate mapping on UMTS based authentication information exchange. Its Authorisation functionality is based on the transfer of the authenticated users’ subscribed profiles from the same HLR, the profiles are used thereafter for granting access or not to specific WLAN services. SAG can be easily and safely integrated into core GSM/GPRS and UMTS networks. Furthermore, the gateway software can be installed on the operators Network Management System from which configuration and monitoring of the product can be easily performed.
In the context of Evolute a comprehensive AAA solution for supporting users roaming among heterogeneous networks was designed and realised. Using this approach, a user can roam among different networks and get access to network and multimedia services. The current AAA development supports only GSM/GPRS authentication, however, it can be easily extended to UMTS networks. The work involved design, implementation and testing both in practice and theory of the following components: - IP-based AAA infrastructure: This involves the integration of multimedia and mobility control components with AAA servers. This involved designing and extending of components for enabling the integration between SIP and RADIUS as well as the usage of SIP-based authentication in IP environments. - Enhanced access functionalities: To demonstrate the ability of the Evolute AAA infrastructure, user applications and hosts were extended to enable SIM-based access to wireless LAN and SIP-based services. - Integration of GSM/GPRS and IP-based AAA: This part of the work involved the design and realization of integration and mapping of IP-based AAA protocols (RADIUS) and GSM protocols (SS7). This work resulted in the implementation of the SIM access gateway. - An extended HLR for the GPRS network is required, incorporating extensions to the MAP signalling to support additional information elements for authentication and authorisation of WLAN users. - Adaptations to the mobile client are required, enabling a terminal to be multimode but also reading the necessary SIM triplets and being able to securely send the information to HLR for authentication and authorisation procedures. A major result of these activities was a demonstration environment showing the feasibility of seamless integration between different networking and AAA technologies.
University of Surrey developed a Context Transfer mechanism, which enhances cellular-IP mobility protocol, aiming to further optimise the handoff operation in mobile networks. During the handoff operation from one cellular-IP base station to another, cellular-IP packets could be used to initiate and transfer authorised context from the previous cellular-IP base station via the cellular-IP gateway(s) to the new cellular-IP base station. This draft presents how the context transfer extensions introduced could facilitate in reducing latency and packet loss by avoiding the signalling required between the mobile node and the new base station in re-establishing the desired state information. Furthermore, Intracom worked closely with University of Surrey and has developed and integrated the mechanism achieving service sustainment at the new point of attachment after handoff, thus softening the handoff procedure.
As new high-speed WLAN technologies are making a strong entry in the market and viable standards are replacing a very fragmented field of vendor specific solutions, they provide almost wired speed communication capabilities in offices and other high usage areas (often referred to as hotspots). Combining the wide coverage of cellular systems with the speed and capacity advantages of WLANs, users are enabled to make the most out of wireless IP communication. By introducing global IP mobility, applying it across different radio technologies and platforms, a unified all-IP-based communication infrastructure can thus be provided for mobile Internet access. EVOLUTE consortium explored the use of heterogeneous wireless networks, in order to provide seamless multimedia services over a range of geographical areas whenever and wherever it is required. Within this concept, a mobile node equipped with multiple wireless network interfaces will have many ways of accessing the all-IP-based infrastructure through different types of wireless networks. For example, a typical user may move from an office environment, where his/her PDA or laptop is connected (e.g. via an in-room WLAN) to elsewhere in the building, where it may be connected via a building-wide RF network. The same user may then move outside, where his/her connectivity is via a cellular network, and then into another building, which is connected via a different building-wide RF network. EVOLUTE specified, developed and tested a vertical handoff scheme that allows a mobile user to roam amongst various multiple wireless networks in a manner that is completely transparent to real-time services and that disrupts connectivity as little as possible. An all-IP infrastructure does not only hold the promise of a more flexible network architecture but even more the basis for providing intelligent and personalised communication services in a simple and distributed manner. While current approaches for service creation are usually realized in a centralized manner and are geared towards a single media, basing the service creation on IP allows for combining mobile and wireless technologies, real time audio and video services and data services. Further, by deploying multimedia servers, real-time services can be provided in a distributed manner, which allows the separation of service and network provisioning.
Main results of the Evolute project are the following; - SIP based service provision components. - Implementation of two multimedia service scenarios on top of the EVOLUTE infrastructure. One scenario is Instant Messaging (IM) and Video Streaming based, however the second deals more with instant messaging and roaming between WLAN and GPRS (or GSM) network. - Implementation of the RTSP mobility. To make the service provision possible in EVOLUTE, the SIP proxy -- the SIP Express Router (SER)-- was enhanced by some components such as IM and presence platform, SIP/SMS Gateway, CPL script. Some enhancements on the client side were performed as well, for instance, the SIP client (KPhone) was extended to support roaming and dynamic changing of the used IP address. It was also enhanced to interwork with an RTSP server in order to allow the explained below scenario. The multimedia service based on both Instant Messages and Video Streaming can be considered as an example of the location based services that can be deployed in a WLAN hot spot or in the 3G Network by a Service Provider. The service is based on the assumption that the SIP and RTSP protocols are used. A user enters in the WLAN hot spot, he gets access to the network using the Evolute AAA procedure and then he registers at the SIP proxy. The SIP proxy sends him an Instant Message with a list of RTSP URLS from which the user can choose a movie trailer (for example). He clicks on the selected URL and the RTSP player starts. The movie will be provided if the user is authorized to get access to the RTSP service. This service is fully integrated in the Service Authentication and Authorization architecture proposed and implemented in the project, allowing an ISP to directly deploy it in its network. Keeping a multimedia session alive while roaming in a heterogenous environment was also addressed in EVOLUTE and a multimedia service scenario was developed for that purpose: a user accessing the internet with a GPRS technology, starts a text chat session with a friend, then he moves to a hotspot and keeps the multimedia session. Afterwards, he moves to a GSM network, closes his laptop but still keeps chating by receiving SMS messages on his mobile. The components used in this scenarios were mentioned earlier. At the moment the RTSP standard doesn�t contain any reference to mobility and till now there is no implementation of both RTSP client and server that is able to manage the mobility of the user. The state of art is the proposal of H. Schulzrinne�s in which he suggests a solution for RTSP mobility based on the SIP mobility approach. The multilayer mobility management architecture proposed in the EVOLUTE project, even if it is based on a hybrid SIP/Mobile IP/micromobility protocols solution can be applied also to RTSP. In an intra-domain handoff, the RTSP signaling traffic is exchanged between the RTSP server and the client using Mobile IP, instead of the RTP media stream that is redirected to the RTSP client new position, without using Mobile IP. The redirection of the RTP traffic has been done sending a PAUSE message, then a new SETUP message from the client to the server, followed by a PLAY message. This solution, agreed with the MMUSIC working group has been successfully tested in the laboratory: the RTSP client interacted with the Cellular IP client, the Mobile IP client and the RTSP server in the correct way during the handoff. The tests show that, even if few seconds are required for the handoff, the freezing of the images and the restarting of the images have a good effect on the user perception of the handoff. This solution has been implemented in the MPEG4IP client and in the Darwin streaming server, without any header addition to the RTSP standard, but using the great flexibility of the RTSP protocol. Since the EVOLUTE mobility solution involves also Network Address Translator, the implementation of the RTSP mobility includes also the addition of the STUN protocol support in the MPEG4IP client. This will allow the RTSP client not only to support the RTSP mobility, but also the NAT and firewall traversal. All these results have been developed in Linux and tested both in a laboratory environment and in a close to real environment: they can be considered prototypes of multimedia services. These results can interest 2G/3G/4G telecom operators, WLAN network service providers, Service providers and Content Providers. They can use the multimedia service provisioning architecture, proposed in the EVOLUTE project, to offer a wide range of services because there is the support of AAA functionalities. Even if the results have been demonstrated and evaluated with a 2G network, they could be extended to a 3G/4G network without any changes and without any impact on the exploitation results, because the multimedia service provisioning architecture has been designed for being used in a 3G networks.