Markus Anwander

Flexible experimentation in wireless sensor networks

Virtual testbeds model them by seamlessly integrating physical, simulated, and emulated sensor nodes and radios in real time.

UAVNet: A mobile wireless mesh network using Unmanned Aerial Vehicles

We developed UAVNet, a framework for the autonomous deployment of a flying Wireless Mesh Network using small quadrocopter-based Unmanned Aerial Vehicles (UAVs). The flying wireless mesh nodes are automatically interconnected to each other and building an IEEE 802.11s wireless mesh network. The implemented UAVNet prototype is able to autonomously interconnect two end systems by setting up an airborne relay, consisting of one or several flying wireless mesh nodes. The developed software includes basic functionality to control the UAVs and to setup, deploy, manage, and monitor a wireless mesh network. Our evaluations have shown that UAVNet can significantly improve network performance.

MARWIS: a management architecture for heterogeneous wireless sensor networks

In this paper we present a new management architecture for heterogeneous wireless sensor networks (WSNs) called MARWIS. It supports common management tasks such as monitoring, (re)configuration, and updating program code in a WSN and considers specific characteristics of WSNs and restricted physical resources of the nodes such as battery, computing power, memory or network bandwidth and link quality. To handle large heterogeneous WSN we propose to subdivide it into smaller sensor subnetworks (SSNs), which contains sensor node of one type. A wireless mesh network (WMN) operates as backbone and builds the communication gateway between these SSNs. We show that the packet loss and the round trip time are decreased significantly in such an architecture. The mesh nodes operate also as a communication gateway between the different SSNs and perform the management tasks. All management tasks are controlled by a management station located in the Internet.

BEAM: A Burst-aware Energy-efficient Adaptive MAC protocol for Wireless Sensor Networks

Low latency for packet delivery, high throughput, good reactivity, and energy-efficient operation are key challenges that MAC protocols for Wireless Sensor Networks (WSNs) have to meet. Since traffic patterns as well as network load may change during network lifetime, adaptability of the protocol stack, e.g. in terms of duty cycling, and the integration of reliable transport mechanisms are mandatory. So far, given that optimizations for energy-efficiency and performance parameters are contradicting, most MAC protocols proposed have concentrated on either one or the other. In order to close this gap, we designed BEAM (Burst-aware Energy-efficient Adaptive MAC).

Evaluation of WiseMAC and extensions on wireless sensor nodes

In the past five years, many energy-efficient medium access protocols for all kinds of wireless networks (WSNs) have been proposed. Some recently developed protocols focus on sensor networks with low traffic requirements are based on so-called preamble sampling or low-power listening. The WiseMAC protocol is one of the first of this kind and still is one of the most energy-efficient MAC protocols for WSNs with low or varying traffic requirements. However, the high energy-efficiency of WiseMAC has shown to come at the cost of a very limited maximum throughput.In this paper, we evaluate the properties and characteristics of a WiseMAC implementation in simulation and on real sensor hardware. We investigate on the energy-consumption of the prototype using state-of-the-art evaluation methodologies. We further propose and examine an enhancement of the protocol designed to improve the traffic-adaptivity of WiseMAC. By conducting both simulation and real-world experiments, we show that the WiseMAC extension achieves a higher maximum throughput at a slightly increased energy cost both in simulation and real-world experiments.

SNOMC: An overlay multicast protocol for Wireless Sensor Networks

Using multicast communication in Wireless Sensor Networks (WSNs) is an efficient way to disseminate the same data (from one sender) to multiple receivers, e.g., transmitting code updates to a group of sensor nodes. Due to the nature of code update traffic a multicast protocol has to support bulky traffic and end-to-end reliability. We are interested in an energy-efficient multicast protocol due to the limited resources of wireless sensor nodes. Current data dissemination schemes do not fulfill the above requirements. In order to close the gap, we designed and implemented the SNOMC (Sensor Node Overlay Multicast) protocol. It is an overlay multicast protocol, which supports reliable, time-efficient, and energy-efficient data dissemination of bulky data from one sender to many receivers. To ensure end-to-end reliability, SNOMC uses a NACK-based reliability mechanism with different caching strategies.

Authentication and authorisation mechanisms in support of secure access to WMN resources

Over the past several years, a number of design approaches in wireless mesh networks have been introduced to support the deployment of wireless mesh networks (WMNs). We introduce a novel wireless mesh architecture that supports authentication and authorisation functionalities, giving the possibility of a seamless WMN integration into the homes organization authentication and authorisation infrastructure. First, we introduce a novel authentication and authorisation mechanism for wireless mesh nodes. The mechanism is designed upon an existing federated access control approach, i.e. the AAI infrastructure that is using just the credentials at the users home organization in a federation. Second, we demonstrate how authentication and authorisation for end users is implemented by using an existing web-based captive portal approach. Finally, we observe the difference between the two and explain in detail the process flow of authorized access to network resources in wireless mesh networks. The goal of our wireless mesh architecture is to enable easy broadband network access to researchers at remote locations, giving them additional advantage of a secure access to their measurements, irrespective of their location. It also provides an important basis for the real-life deployment of wireless mesh networks for the support of environmental research.

TARWIS — A testbed management architecture for wireless sensor network testbeds

Research in the area of Wireless Sensor Networks (WSNs) has become more and more driven by real-world experimental evaluations rather than network simulation. Numerous testbeds of WSNs have been set up in the past decade, often with very much differing architectural design and hardware. The Testbed Management Architecture for Wireless Sensor Networks (TARWIS) presented in this paper provides the most crucial management and scheduling functionalities for WSN testbeds, independent from the testbed architecture and the sensor nodes operating systems. These functionalities are: a consistent notion of users and user groups, resource reservation features, support for reprogramming and reconfiguration of the nodes, provisions to debug and remotely reset sensor nodes in case of node failures, as well as a solution for collecting and storing experimental data. We describe the workflow of using a TARWIS on a WSN testbed over the entire experimentation life cycle, starting from resource reservation over experiment definition to the collection of real-world experimental data.

Connecting remote sites to the wired backbone by wireless mesh access networks

Wireless Mesh Networks (WMNs) operating in the 5 GHz band (IEEE 802.11 a/h) offer a great opportunity to function as wireless access networks. Remote sites that lack direct access to a wired/fibre network may benefit from this technology, as it can be used to bridge possibly large distances. The high gain of directional antennas improves the reception of signals in focused directions and reduces interference from unwanted sources. Therefore, they are the preferred choice for such bridging scenarios. In this paper, we present our experiences with setting up such a Wireless Access Network using directional antennas in the area of Neuchâtel, Switzerland. We describe the necessary equipment and planning steps, highlight common pitfalls and discuss gained insights as well as experimental results. Measured data supports the feasibility of our networking approach, yet reveals the high impact of general challenges that have to be overcome in real-world deployments.

Real-World Energy Measurements of a Wireless Mesh Network

Over the past several years the topics of energy consumption and energy harvesting have gained significant importance as a means for improved operation of wireless sensor and mesh networks. Energy-awareness of operation is especially relevant for application scenarios from the domain of environmental monitoring in hard to access areas. In this work we reflect upon our experiences with a real-world deployment of a wireless mesh network. In particular, a comprehensive study on energy measurements collected over several weeks during the summer and the winter period in a network deployment in the Swiss Alps is presented. Energy performance is monitored and analysed for three system components, namely, mesh node, battery and solar panel module. Our findings cover a number of aspects of energy consumption, including the amount of load consumed by a mesh node, the amount of load harvested by a solar panel module, and the dependencies between these two. With our work we aim to shed some light on energy-aware network operation and to help both users and developers in the planning and deployment of a new wireless mesh network for environmental research.