Wolf-Bastian Pöttner

IBR-DTN: A lightweight, modular and highly portable Bundle Protocol implementation

In this paper we present IBR-DTN, a lightweight, modular and portable Bundle Protocol implementation and DTN daemon. IBR-DTN is especially suited for embedded platforms, which allows to leverage the benefits of a fully compliant Bundle Protocol daemon in cost sensitive distributed sensing applications. We line out IBR-DTNs extensible software architecture and introduce the modules included in the standard IBR-DTN distribution. To give an impression of the performance that can be expected when using IBR-DTN, we perform a series of benchmarks and compare the outcome with DTN2 performance, the reference implementation of the Bundle Protocol.

The GINSENG system for wireless monitoring and control: Design and deployment experiences

Todays industrial facilities, such as oil refineries, chemical plants, and factories, rely on wired sensor systems to monitor and control the production processes. The deployment and maintenance of such cabled systems is expensive and inflexible. It is, therefore, desirable to replace or augment these systems using wireless technology, which requires us to overcome significant technical challenges. Process automation and control applications are mission-critical and require timely and reliable data delivery, which is difficult to provide in industrial environments with harsh radio environments. In this article, we present the GINSENG system which implements performance control to allow us to use wireless sensor networks for mission-critical applications in industrial environments. GINSENG is a complete system solution that comprises on-node system software, network protocols, and back-end systems with sophisticated data processing capability. GINSENG assumes that a deployment can be carefully planned. A TDMA-based MAC protocol, tailored to the deployment environment, is employed to provide reliable and timely data delivery. Performance debugging components are used to unintrusively monitor the system performance and identify problems as they occur. The article reports on a real-world deployment of GINSENG in an especially challenging environment of an operational oil refinery in Sines, Portugal. We provide experimental results from this deployment and share the experiences gained. These results demonstate the use of GINSENG for sensing and actuation and allow an assessment of its ability to operate within the required performance bounds. We also identify shortcomings that manifested during the evaluation phase, thus giving a useful perspective on the challenges that have to be overcome in these harsh application settings.

A practical analysis of communication characteristics for mobile and distributed pollution measurements on the road

Summary Measuring environmental data in city areas has become an important issue for municipalities due to several climate directives. As fixed measuring stations are inflexible, cost-intensive, and limited to monitoring a specific spot, we developed a distributed environmental monitoring network called Environmental Monitoring in Metropolitan Areas (EMMA). This architecture is based on the delay tolerant networking approach and can be integrated into existing Public Transportation Networks (PTNs). Buses or other vehicles can be equipped with sensor nodes that gather data and forward messages. In order to evaluate the basic ideas of this project we performed a series of real-world experiments. Besides analyzing the behavior of 802.11-based Wireless Local Area Network (WLAN) between moving vehicles in a controlled environment, we also evaluated the communication performance in urban environments. Moreover, we examined the qualification of a Disruption Tolerant Networking (DTN) implementation for spreading measurement results throughout the network. The suitability of EMMA’s architecture has been successfully demonstrated by these experiments. Copyright

Constructing Schedules for Time-Critical Data Delivery in Wireless Sensor Networks

Wireless sensor networks for industrial process monitoring and control require highly reliable and timely data delivery. To match performance requirements, specialised schedule based medium access control (MAC) protocols are employed. In order to construct an efficient system, it is necessary to find a schedule that can support the given application requirements in terms of data delivery latency and reliability. Furthermore, additional requirements such as transmission power may have to be taken into account when constructing the schedule. In this article, we show how such schedule can be constructed. We describe methods and tools to collect the data necessary as input for schedule calculation. Moreover, due to the high complexity of schedule calculation, we also introduce a heuristic. We evaluate the proposed methods in a real-world process automation and control application deployed in an oil refinery and further present a long-term experiment in an office environment. Additionally, we discuss a framework for schedule life-cycle management.

Performance comparison of DTN bundle protocol implementations

In recent years, Delay Tolerant Networking (DTN) has received a lot of interest from the networking community. Today the Bundle Protocol (RFC 5050) is the standard communication protocol in DTNs and several implementations for various platforms are available. As of now, no quantitative analysis of the different implementations performance or a structured evaluation of interoperability has been undertaken. We performed interoperability checks and an extensive quantitative performance analysis of three Bundle Protocol implementations for Linux systems. In this paper we summarize our main findings. While the overall results show, that all implementations provide some baseline compatibility with each other, the stability and achieved performance under stress situations varies widely between implementations.

Data elevators: Applying the bundle protocol in Delay Tolerant Wireless Sensor Networks

Delay Tolerant Networking (DTN) enables transfer of data where conventional network protocols fail to deliver data because no continuous end-to-end connectivity is available. While the Bundle Protocol (BP) has been established as the standard DTN protocol in many application areas, Wireless Sensor Networks (WSN) often use proprietary protocols with a subset of the BP features. In this paper we use an exemplary application to demonstrate how the BP can be beneficial for many WSN-based projects. We show, how low-power sensor nodes can transport bundles by exploiting existing movement in the environment. More importantly we show, how 8-bit WSN nodes can seamlessly interact with standard BP implementations running on standard PCs. Our application, a sensor that is installed on the roof of a 15-story building, is using an elevator to transport bundles carrying measured values to our lab. We analytically compare the BP to existing protocols for WSNs, evaluate our application scenario and give insight into principal limitations.

Impact of radio range on contact characteristics in bus-based delay tolerant networks

In bus-based delay tolerant networks the duration of a contact between two nodes limits the amount of data that can be transferred. For the implementation of such networks it is important to determine which contact durations can be expected. Moreover, this information can be used by scheduling and routing algorithms to increase efficiency. In this paper we structure and characterize the different types of contacts and examine the effects of radio range on contact duration. For realistic results we experimentally investigate the typical range of IEEE 802.11a/b and use a real mobility trace of a large-scale public transport network. We report the simulation results for different types of contacts and the probability distribution of contact durations for various realistic ranges. Furthermore we show that the angle of contacts is an appropriate criterion for the classification of contacts, and propose to use it as input for routing and scheduling decisions.

Piggy-Backing Link Quality Measurements to IEEE 802.15.4 Acknowledgements

In this paper we present an approach to piggyback link quality measurements to IEEE 802.15.4 acknowledgement frames by generating acknowledgements in software instead of relying on hardware support. We show that the software-generated ACKs can be sent meeting the timing constraints of IEEE 802.15.4. This allows for a standard conforming, energy neutral dissemination of link quality related information in IEEE 802.15.4 networks. This information is available at no cost when transmitting data and can be used as input for various schemes for adaptive transmission power control and to assess the current channel quality.

A demonstrator of the GINSENG-approach to performance and closed loop control in WSNs

The overall goal of GINSENG is a wireless sensor network that will meet application-specific performance targets, and that will be proven in a real industry setting where performance is critical. This demonstrator shows some of the key outcomes of the GINSENG project such as energy-efficient wireless real-time closed loop control, performance debugging, integration with ERP systems and usability on heterogeneous hardware. Furthermore, it allows the user to interact with the system.

QoS-AODV6E: An energy-balancing QoS routing scheme for WSNs

Wireless Sensor Networks (WSN) now advance into areas where new scenarios and applications require WSNs to meet certain Quality of Service (QoS) requirements. To tackle these challenges, a routing approach has to consider limited energy supply of sensor nodes, dynamic network conditions as well as node mobility. This paper presents QoS-AODV6E, a routing scheme based on the Ad-hoc On-Demand Distance Vector (AODV) routing protocol, which encompasses QoS and Energy-Awareness for mobile WSNs. Based on the reactive AODV routing protocol, QoS-AODV6E allows applications to specify QoS parameters and finds suitable routes that support their requirements. In order to prolong the lifetime of the network, QoS-AODV6E balances the energy consumption between different paths through the network based on the weakest node. We evaluate our implementation of QoS-AODV6E in Contiki using simulation and measurements.