Anders Nickelsen

OPEN: open pervasive environments for migratory interactive services

One important aspect of ubiquitous environments is to provide users with the possibility to freely move about and continue to interact with the available applications through a variety of interactive devices such as cell phones, PDAs, desktop computers, intelligent watches or digital television sets. Migratory applications are able to follow the user by sensing changes in the users context and adapting to available devices, ideally without interrupting the user experience. However, applications themselves must contain functions to monitor context information, coordinate a migration, handle application adaptation and interact with the user during the migration process. To make life easier for developers and users of migratory applications, we propose an integrated Migration Service Platform (MSP), where all the common migration functions are centralised. We show how the platform is realised as middleware that contains a server for the central functions and lightweight client-side running on the end-user devices. We show how migratory applications can interact with the platform and thereby do not have to contain migration functions themselves. By using the platform, they can register and be controlled by the platform to enrich the user experience with the application. We describe the challenges following the centralisation of a migration platform that can support different types of applications, both games and business applications, implemented with either web-technologies or as component-based applications.

Service migration protocol for NFC links

In future ubiquitous communication environments, users expect to move freely while continuously interacting with the available applications through a variety of devices. Interactive applications will therefore need to support migration, which means to follow users and adapt to the changing context of use while preserving state. This paper focuses on the scenario of migration between two devices in which the actual migration procedure is executed over near-field communication (NFC) ad-hoc links. The NFC link is interesting as it gives the user the perception of trust and enables service continuity in cases where mid- or long-range wireless connectivity is unavailable. Based on an experimental performance analysis of a specific NFC platform, the paper presents a migration orchestration protocol with low overhead and low delays to be used with NFC links. Experimental results allow to conclude on the sizes of application state that can be expected to be feasible for such ad-hoc NFC migration.

Model-based decision framework for autonomous application migration

A dynamically changing state of the run-time environment impacts the performance of networked applications and furthermore influences the user-perceived quality of the applications. By migrating the application between the users devices that give different user experiences, a good overall user experience can be maintained, without loosing the application session. It is non-trivial for a system to automatically choose the best device for migration. The choice must maximize the user experience quality and take into account that a migration delays the users work-flow and even may fail. Moreover, the environment state is not directly observable, and needs to be estimated which leads to inaccuracy. We model the automatic migration trigger as a stochastic optimization problem and we propose to use a hidden Markov model combined with a Markov Decision Process (MDP) to solve the problem. The solution generates policies to choose target device for migration that gives the optimal user experience. We analyse these policies in simulation experiments and derive conclusions on which scenarios the model-based approach performs better than a greedy approach, also when considering inaccurate state estimation.

Scalable Emulation of Dynamic Multi-hop Topologies

Communication in wireless networks is affected by uncontrollable disturbances in the channel. Effects of these disturbances are exacerbated in networks with dynamic topologies and multiple hops. Lack of control of the channel complicates testing of such networks as test conditions are hard, or impossible, to reproduce. This paper describes how to create reproducible test conditions for these networks by emulating the wireless links. Emulation is performed by a topology emulator to which end-nodes are connected using wired links. In real-time, the emulator imposes packet drops and delays onto traffic between end-nodes. The imposed properties are based on simulations of node mobility, loss and delay models. Evaluation confirms that the testbed is capable of emulating links in real time and transparent to upper layer protocols. Additionally, the impact on test results is evaluated, such as increased network delays and reduction of bandwidth when loading the emulator. Finally, an outlook on advancing capabilities and how to integrate such in the emulator is presented.

OPEN Platform for Migration of Interactive Services: Architecture and Evaluation

One important aspect of ubiquitous environments is to provide users with the possibility to freely move about and continue to interact with the available applications through a variety of interactive devices such as cell phones, PDAs, desktop computers, intelligent watches, or digital television sets. Migratory applications are able to follow the user by sensing changes in the users context and adapting to available devices, ideally without interrupting the user experience. However, applications themselves must contain functions to monitor context information, coordinate a migration, handle application adaptation, and interact with the user during the migration process. To make life easier for developers and users of migratory applications, an integrated Migration Service Platform (MSP) is proposed, where all the common migration functions are centralised. The authors show how the platform is realised as middleware that contains a server for the central functions and lightweight client-side running on the end-user devices. The authors show how migratory applications can interact with the platform and thereby do not have to contain migration functions themselves. The authors describe the challenges following the centralisation of a migration platform that can support different types of applications, both games and business applications, implemented with either web-technologies or as component-based applications.

Service Migration Network Support

This chapter introduces the various functionalities needed from the system to support generic service migration processes. The chapter focuses on the supporting parts of the platform related to the needed network support. The chapter introduces entities, modules and components needed for providing the required network support functionalities and detail their interaction, both internally as well as externally.

The Fourth International Conference on Wireless and Mobile Communications, 2008. ICWMC '08

Communication in wireless networks is affected by uncontrollable disturbances in the channel. Effects of these disturbances are exacerbated in networks with dynamic topologies and multiple hops. Lack of control of the channel complicates testing of such networks as test conditions are hard, or impossible, to reproduce. This paper describes how to create reproducible test conditions for these networks by emulating the wireless links. Emulation is performed by a topology emulator to which end-nodes are connected using wired links. In real-time, the emulator imposes packet drops and delays onto traffic between end-nodes. The imposed properties are based on simulations of node mobility, loss and delay models. Evaluation confirms that the testbed is capable of emulating links in real time and transparent to upper layer protocols. Additionally, the impact on test results is evaluated, such as increased network delays and reduction of bandwidth when loading the emulator. Finally, an outlook on advancing capabilities and how to integrate such in the emulator is presented.

Circuit-Elimination based Link-State Routing in Mobile Ad-hoc Networks

Circuit-elimination based connected dominating set formation is an efficient technique for reducing routing overhead in mobile ad hoc networks. In this paper, we propose a new message dissemination algorithm which utilizes such techniques to reduce the number of nodes that generate or forward link state advertisements in link state routing protocols. Simulation results with both static and dynamic network topologies demonstrate the potential of the proposed algorithm to reduce routing overhead, compared with a benchmark link state routing protocol, OLSR.