Mobility Management in beyond 3G-Environments

Beyond 3G-environments are typically defined as environments that integrate different wireless and fixed access network technologies. In this paper, we address IP based Mobility Management (MM) in beyond 3G-environments with a focus on wireless access networks, motivated by the current trend of WiFi, GPRS, and UMTS networks. The GPRS and UMTS networks provide countrywide network access, while the WiFi networks provide network access in local areas such as city centres and airports. As a result, mobile end-users can be always on-line and connected to their preferred network(s), these network preferences are typically stored in a user profile. For example, an end-user who wishes to be connected with highest bandwidth could be connected to a WiFi network when available and fall back to GPRS when moving outside the hotspot area.\ud In this paper, we consider a combination of MM for legacy services (like web browsing, telnet, etc.) using Mobile IP and multimedia services using SIP. We assume that the end-user makes use of multi-interface terminals with the capability of selecting one or more types of access networks\ud based on preferences. For multimedia sessions, like VoIP or streaming video, we distinguish between changes in network access when the end-user is in a session or not in a session. If the end-user is not in a session, he or she needs to be able to start new sessions and receive invitations for new sessions. If the end-user is in a session, the session needs to be handed over to the new access network as seamless as possible from the perspective of the end-user. We propose an integrated but flexible solution to these problems that facilitates MM with a customizable transparency to applications and end-users

Efficient sharing of dynamic WSNs

The Ambient middleware supports real-time monitoring and remote maintenance across the Internet via wired and mobile wireless network access technologies. Additionally, the middleware offers easy integration with third-party applications. Ambient Studio utilizes the middleware for remote WSN configuration and monitoring. The ConnectBox utilizes it to monitor and maintain WSNs remotely. This paper describes the Ambient middleware and compares its efficiency with the existing messaging protocols used for instant messaging and web services

Dynamic State Estimation based Transmission Line Protection Scheme: Performance Evaluation with Different Fault Types and Conditions

This paper presents the experimental validation of a transmission line protection scheme based on dynamic state estimation for different fault types and conditions. The protection scheme utilizes real-time high-frequency sampled measurements from advanced sensors and evaluates the operating condition of the transmission line based on which a tripping signal is generated in case a fault occurs. The validation is performed using a physical scaled-down model of a power system, consisting of a transmission line, transformer, synchronous generator, and loads. The following faults are examined during the validation: unbalanced faults under different load conditions, high impedance fault, fault current fed from both ends, hidden failure, external fault, and load change conditions. The results show that the scheme performs as intended and thus proves its efficacy to detect various types of faults. The maximum fault detection time is calculated to be 42.5 milliseconds, while the maximum fault clearing time comes out to be 82.5 milliseconds, on par with currently employed protection methods. The obtained results demonstrate the ability of the scheme to detect different fault types under varying conditions and avoid potential issues with relay coordinatio

Transmission Line Protection Using Dynamic State Estimation and Advanced Sensors: Experimental Validation

This paper presents the experimental validation of a protection scheme for a transmission line based on dynamic state estimation along with the practical application of advanced sensors in this protection scheme. The scheme performs dynamic state estimation with high-frequency measurements provided by the sensors, assesses the operating condition (i.e., health) of the transmission line in real-time, and thereby determines the tripping signal whenever a fault is detected. The validation was carried out in two steps, first with simulation studies for a three-phase fault and then with the experimental implementation using a physical scaled-down model of a power system consisting of transmission lines, transformers, and loads. The simulation and validation results have shown that the scheme performs adequately in both normal and fault conditions. In the fault case with the experimental setup, the scheme could correctly detect the fault and send the trip signal to the line’s circuit breakers with a total fault clearing time of approximately 65 milliseconds which is comparable to conventional protection methods. The average processing time for a measurement sample block is 12.5 milliseconds. The results demonstrate that this scheme and the sensors would work for transmission line protection which can avoid relay coordination and settings issues

Sensor Networks in the Low Lands

This paper provides an overview of scientific and industrial developments of the last decade in the area of sensor networks in The Netherlands (Low Lands). The goal is to highlight areas in which the Netherlands has made most contributions and is currently a dominant player in the field of sensor networks. On the one hand, motivations, addressed topics, and initiatives taken in this period are presented, while on the other hand, special emphasis is given to identifying current and future trends and formulating a vision for the coming five to ten years. The presented overview and trend analysis clearly show that Dutch research and industrial efforts, in line with recent worldwide developments in the field of sensor technology, present a clear shift from sensor node platforms, operating systems, communication, networking, and data management aspects of the sensor networks to reasoning/cognition, control, and actuation

Realtime mobile sharing of multimedia and context

Today’s inter-connected networks enable feature-rich applications that adapt according to situational and environmental changes, and the networks and objects that are discovered. These so-called pervasive applications can be composed from both locally and globally available multimedia resources such as audio and video, web services and context sources. Context sources in these pervasive applications can vary from your mobile phone’s sensors to dedicated sensor networks deployed in buildings and vehicles, sensor nodes attached to beings and objects, and events generated from devices and applications. The sharing of resources and the dynamic changes in these pervasive applications pose a number of challenges on the enabling infrastructure. This thesis focuses on methods for realtime sharing of wireless access networks, sensor information and multimedia among applications on mobile devices. We propose to use application-level techniques to support mobility and sharing and enable using lower-level gtechniques where available. Our contributions include methods and supporting communication architectures for efficient sharing of wireless access networks, multimedia and wireless sensor networks. Additionally, we contribute a reasoning framework to compare and combine communication architectures that support pervasive applications

Spanning a multimedia session across multiple devices

This paper describes an innovative solution that allows a multimedia session to be distributed over multiple devices that are in close proximity to a user. This would typically be useful when a user engaged in an audio/video conference enters a meeting room. Upon entering, all media session components are transferred from the personal digital assistant (PDA) to the projector, Hi-Fi set, and webcam present in the meeting room. When the user leaves the room, all media session components are transferred back to the PDA. Transferring parts of a multimedia session between different devices is defined as partial session mobility (PSM). Numerous methods exist for PSM. None of these methods is directly suitable for initiating PSM from a dedicated network node such as an IP Multimedia Subsystem (IMS) application server, but they do provide a starting point. Because of a number of advantages in the invite-based method, this method is taken as a basis for network-initiated PSM. This paper compares the existing methods, describes the proposed network-initiated method to support PSM, and investigates how to combine it with terminal-initiated PSM. It also describes how PSM could be supported in IMS. © 2008 Alcatel-Lucent