Opportunistic Sensing in Wireless Sensor Networks

Opportunistic sensing systems consist of changing constellations of wireless sensor nodes that, for a limited amount of time, work together to achieve a common goal. Such constellations are self-organizing and come into being spontaneously. This paper presents an opportunistic sensing system to select a subset of sensor nodes out of a larger set based on a common context. We show that it is possible to use a wireless sensor network to make a distinction between carriages from different trains. The common context in this case is acceleration, which is used to select a subset of carriages that belong to the same train. Simulations based on a realistic set of sensor data establish that the method is valid, but that the algorithm is too complex for implementation. Downscaling reduces the number of processor execution cycles as well as memory usage, and makes the algorithm suitable for implementation on a wireless sensor node with acceptable loss of precision. Actual implementation on wireless sensor nodes confirms the results obtained with the simulations

A Real time network at home

This paper proposes a home network which integrates both real-time and non-real-time capabilities for one coherent, distributed architecture. Such a network is not yet available. Our network will support inexpensive, small appliances as well as more expensive, large appliances. The network is based on a new type of real-time token protocol that uses scheduling to achieve optimal token-routing through the network. Depending on the scheduling algorithm, bandwidth utilisations of 100 percent are possible. Token management, to prevent token-loss or multiple tokens, is essential to support a dynamic, plug-and-play configuration. Small appliances, like sensors, would contain low-cost, embedded processors with limited computing power, which can handle lightweight network protocols. All other operations can be delegated to other appliances that have sufficient resources. This provides a basis for transparency, as it separates controlling and controlled object. Our network will support this. We will show the proposed architecture of such a network and present experiences with and preliminary research of our design

A Debugging Tool for Distributed Systems

This paper describes parts of the design of a debugger for a distributed real-time multimedia system. Emphasis lies on the distributed aspect of debugging, which means that attention is paid to the external behaviour of the processes. This type of debugging is useful to find communication or synchronization errors. However, experience shows that this is not enough: the debugger must also provide hooks for the user to use traditional sequential debuggers. This type of debugging focuses on the internal behaviour - or internal logic - of processes. For the sequential debugging part a normal debugger like GDB can be taken. Three key elements of the debugger are events, filters and recognizers. By definition events are the lowest level of system activity that may be observed by the event debugger. Filters are applied to remove events from the stream of events produced by the debuggee that are of no interest for the programmer. Recognizers are used to recognize behaviour -right or wrong- of the system. By combining events, different levels of abstraction are introduced, thus alleviating the task of the programme

A QoS-Control Architecture for Object Middleware

This paper presents an architecture for QoS-aware middleware platforms. We present a general framework for control, and specialise this framework for QoS provisioning in the middleware context. We identify different alternatives for control, and we elaborate the technical issues related to controlling the internal characteristics of object middleware. We illustrate our QoS control approach by means of a scenario based on CORBA

Application Interaction Model for Opportunistic Networking

In Opportunistic Networks, autonomous nodes discover, assess and potentially seize opportunities for communication and distributed processing whenever these emerge. In this paper, we consider prerequisites for a successful implementation of such a way of processing in networks that consist mainly of heterogeneous devices. Devices are heterogeneous in size, in abilities, in movement, and in the role they play in the application. The focus here is on the interaction at different levels and among various nodes, in view of our current scenario, where mobile nodes connect clusters of wireless sensors. The combined networks form an infrastructure-less sensor and actuation network. We propose a RESTful interaction model, which we demonstrate with an example implementation

Towards Opportunistic Data Dissemination in Mobile Phone Sensor Networks

Recently, there has been a growing interest within the research community in developing opportunistic routing protocols. Many schemes have been proposed; however, they differ greatly in assumptions and in type of network for which they are evaluated. As a result, researchers have an ambiguous understanding of how these schemes compare against each other in their specific applications. To investigate the performance of existing opportunistic routing algorithms in realistic scenarios, we propose a heterogeneous architecture including fixed infrastructure, mobile infrastructure, and mobile nodes. The proposed architecture focuses on how to utilize the available, low cost short-range radios of mobile phones for data gathering and dissemination. We also propose a new realistic mobility model and metrics. Existing opportunistic routing protocols are simulated and evaluated with the proposed heterogeneous architecture, mobility models, and transmission interfaces. Results show that some protocols suffer long time-to-live (TTL), while others suffer short TTL. We show that heterogeneous sensor network architectures need heterogeneous routing algorithms, such as a combination of Epidemic and Spray and Wait