| 1. |
- Wennerström, Hjalmar, 1984-
(författare)
-
A Node-Link Perspective on the Impact of Local Conditions in Sensor Networks
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Sensor networks are made up of small battery-powered sensing devices with wireless communication capabilities, enabling the network to monitor the environment in which it is deployed. Through their flexible and cable-free design these networks open up for new deployment scenarios that were previously not plausible such as during a natural disaster. Motivated by scenarios where centralized oversight is not possible the focus of this thesis is to equip nodes with further adaptability to changes in the links it has with other nodes. This is achieved through contributions in three areas focusing on observations from a node-link perspective.First, the impact the local environment has on the nodes is explored by deploying a sensor network outdoors next to a meteorological station to correlate the variations in link quality to the changes in the environment. The work identifies temperature as the main factor, where through further investigations in a controlled setting, a linear relationship between the decrease in signal quality and the increase in temperature is described.Secondly, the thesis address how nodes in a sensor network can be motivated to exchange data by modeling it as a game. The game theoretic design is motivated by the absence of any centralized control and focus on the nodes as individual users in the network. The presented design motivates the selfish nodes to participate in the exchange of sensor data, showing that it is the best strategy.Lastly, by exploring and understanding how connections in a mobile sensor network occur, nodes are given more flexibility to determine how to send and sample sensor data. This adaptability to contact occurrences is shown to provide better ways of sending data by selecting higher quality links as well as making sampling more energy preserving by reducing the rate in the vicinity of other nodes.
|
|
| 2. |
- Wennerström, Hjalmar
(författare)
-
Meteorological impact and transmission errors in outdoor wireless sensor networks
- 2013
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Wireless sensor networks have been deployed outdoors ever since their inception. They have been used in areas such as precision farming, tracking wildlife, and monitoring glaciers. These diverse application areas all have different requirements and constraints, shaping the way in which the sensor network communicates. Yet something they all share is the exposure to an outdoor environment, which at times can be harsh, uncontrolled and difficult to predict. Therefore, understanding the implications of an outdoor environment is an essential step towards reliable wireless sensor network operations.In this thesis we consider aspects of how the environment influence outdoor wireless sensor networks. Specifically, we experimentally study how meteorological factors impact radio links, and find that temperature is most significant. This motivates us to further study and propose a first order model describing the impact of temperature on wireless sensor nodes. We also analyze transmission errors in an outdoor wireless sensor networks, identifying and explaining patterns in the way data gets corrupted. The findings lead to a design and evaluation of an approach for probabilistic recover of corrupt data in outdoor wireless sensor networks. Apart from the experimental findings we have conducted two different outdoor deployments for which large data sets has been collected, containing both link and meteorological measurements.
|
|
