Teodora Guenkova-Luy

End-to-end quality-of-service coordination for mobile multimedia applications

Transmitting real-time multimedia streams over heterogeneous mobile networks is a challenging task. Variation in network and system conditions can dramatically affect application performance. When providing end-to-end quality-of-service (QoS) multiple system facets should be coordinated: orchestration of local and peer resources, reservation of network resources, adaptation of multimedia streams, etc. This paper presents an end-to-end negotiation protocol (E2ENP) for negotiating and coordinating QoS on an end-to-end basis both at application and network layer. Based on a flexible extensible markup language (XML) model and extending SDPng concepts, the protocol enables the negotiation of system capabilities and allows provider-services to effectively influence the negotiation process. The aim of the E2ENP design is to optimize the efficiency of multimedia call setup and reduce the time for QoS renegotiations, whenever vertical handovers or spontaneous network reconfigurations occur. The basic protocol is presented, together with implementation and measurement results, stemming from several studies on current and future third-generation/fourth-generation scenarios.

Service Location using the Session Initiation Protocol (SIP)

Service location is a crucial part of dynamic systems that are using other services in order to accomplish their work. Beside service oriented architectures (SOA), multimedia networks need to dynamically access services on demand. Usually, service-location protocols support users at finding services. Therefore, in dynamic environments, the implementation of one of these protocols and an appropriate infrastructure is needed. We propose the integration of service location with the session initiation protocol (SlP), which is a common coordination protocol for multimedia services. With only small extensions on top of the classical SIP implementation, nodes may register and search for services (e.g., searching for video-on-demand servers with special capabilities), thus, omitting the additional overhead of implementing separate discovery services. Our solution is compliant to the SIP standard and can offer the same level of flexibility as common service-location protocols, however, reducing the processing complexity at the SIP-based devices

Service Mobility with SIP, SDP and MPEG-21

The ubiquitous access to multimedia services anywhere and at any time requires flexible service accommodation to user requirements and to device capabilities. At mobility of persons and devices, it is possible to enforce not only terminal-based adaptations, but also the media sessions can migrate from device to device to optimize the user experience. As the capabilities of mobile hand-held devices are limited, migrating sessions to close-by high-performance terminals like wall displays or in-home entertainment systems will indeed contribute to optimized device application and to more satisfactory media consumption. The current SIP/SDP framework can partially enable a session-migration process. However, SIP/SDP lacks advanced client-search and description capabilities. On the other hand, MPEG-21 DI can support sophisticated service descriptions but it misses a control-data exchange approach. Therefore, this paper proposes to merge concepts from IMS using SIP/SDP(ng) with MPEG-21 DI to implement a novel session migration concept based on standardized mechanisms.

Adaptive multimedia multi-party communication in ad hoc environments

Adaptivity is a key issue for enhanced multimedia communication in wireless environments, where the network QoS for a whole session cannot be guaranteed. Within this paper we propose a set of mechanisms to provide adaptive multimedia multi-party communication according to user-defined QoS levels over self-organizing ad hoc network extensions connected to IP access networks. We use special extensions to SIP/SDPng based on XML to negotiate alternative application defined QoS levels and adaptation paths and optionally couple local resource management with network layer QoS. At the network layer, we propose the MMARP (Multicast MANET Routing Protocol) which provides efficient multicast communications within ad hoc network extension to public infrastructure based access networks. MMARP is able to deal with the complexity of supporting traditional IP nodes whilst inter-operating smoothly with fixed IP networks. An adaptive application architecture is demonstrated that uses the E2ENP and allows multimedia applications to reconfigure themselves in realtime to match the specific network conditions in order to preserve the user-perceived QoS. Thus, an integration of application layer QoS as defined by the user and network layer QoS is achieved.

End-to-end quality of service coordination for multimedia applications in heterogeneous, mobile networks

Anytime, anyplace application of distributed, multimedia services requires flexible configuration of service quality and coordination of relevant management actions both in mobile terminal and network. This paper presents a new approach for coordinating quality of service (QoS) configuration at multimedia-session establishment and during service adaptations, in accordance with user preferences for service presentation, user contracts with providers, and access/utilization management of the access-provider networks. The general features of an end-to-end negotiation protocol (E2ENP) for multimedia-session management are discussed. E2ENP is designed to minimize signaling load and maximize flexibility of system configuration. The application model of the E2ENP is described and interactions between terminals and access provider are discussed. Some initial measurement results detailing E2ENP performance are presented in consideration with various network configurations.

A Session-Initiation-Protocol-Based Middleware for Multi-Application Management

The deployment of multimedia services in next- generation networks is a challenge due to the high configuration complexity of the streaming process in different stationary and mobile sub-networks and for various user devices. The session initiation protocol (SIP) has proven to be a suitable mechanism to handle the control of multimedia services in such networks. However, the current standardization and implementation of SIP do not allow the simultaneous coordination of multiple concurrent applications on a single device, as the prescribed realization of the SIP state machines (transactions) does not consider mutual access of applications to a single SIP stack. This paper presents a SIP- based mechanism for synchronized management of services in a shared environment. We have developed a middleware that facilitates the uniform access of multiple applications towards one or multiple SIP stacks to enable prioritization of services and centralized resource coordination of concurrent SIP applications on a single terminal or server.

A Decentral Architecture for SIP-based Multimedia Networks

The Session Initiation Protocol (SIP) is a general protocol for session setup and management, e.g., for VoIP. Current SIP networks build on a fixed infrastructure that relies on static network entities. General problems with this infrastructure, e.g., in ubiquitous ad-hoc networks, lead to a trend of integrating peer-to-peer mechanisms into SIP. We propose a generic architecture for decentralised SIP networks. The SIP location service of our architecture is based on JXTA for message routing. This allows SIP networks without central location services, and in extreme even without central SIP proxies. Unlike other approaches, we do not modify SIP. Thus, standard SIP clients can be seamlessly integrated. Due to the flexibility of JXTA, various peer-to-peer algorithms can be integrated according to current requirements. Additionally, our architecture supports registration, discovery and locating of services based on SIP. This saves resources in end terminals and also benefits from the peer-to-peer approach.