7 deus leaflet wp6


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7 deus leaflet wp6

  1. 1. DEUS Deployment and Ease Use of wireless Services Positioning Main challenges Knowledge of the current location of an object or moving person is very useful for several applications. In the use cases of DEUS, we want to guide a person through an exposition in a museum or in a historical building. The person receives some sort of PDA when he arrives at the museum, which then provides him with information based on his current location (e.g. information on a specific painting, historical background of a room). It could also guide someone to a specific part of the exposition, based on the interests of the user. The main challenge in DEUS is to provide an easy-to-use and easy-to-deploy indoor positioning solution which achieves room-level accuracy based on cheap, off-the- shelf wireless sensor nodes. DEUS Approach The positioning application uses the wireless sensor network developed by DEUS and is therefore based on the IEEE 802.15.4 radio technology. These wireless sensor nodes are spread out over the building and gather the information needed to determine a user or asset’s position. The user or asset that needs to be located is equipped with a wireless sensor node that sends beacons, which are picked up by the other wireless sensor nodes. These sensor nodes subsequently send this information to a positioning server. This positioning server analyses the gathered information and calculates the user/asset’s position. Applications that want the user or the asset’s position contact the positioning server to receive the required information. In the DEUS project, we have developed the communication protocol between the sensor nodes and the positioning server and we have implemented three methods to determine the position. These were evaluated separately and a hybrid solution was also considered.
  2. 2. DEUS Deployment and Ease Use of wireless Services DEUS solutions The figure above shows the general concept of the positioning application. We want to determine the position of the person on the left. This user is wearing a PDA and a positioning tag (i.e. an IEEE 802.15.4-based sensor node). This sensor node sends positioning beacons at regular intervals. The beacons are intercepted by the wireless sensor nodes spread out in the building. The nodes individually combine the received information and the measured link information into a measurement report and send this report wirelessly to the positioning server. There, the information is gathered, processed and a position for the user is calculated. This positioning information can then be used by an application. This information is graphically visualized and can be accessed via a webservice. An example can be found in the following figure. The blue dots are the sensor nodes attached at fixed locations in the building, the red dot is the user’s position.
  3. 3. DEUS Deployment and Ease Use of wireless Services Implemented solutions Proximity based In this solution, the asset’s position is determined by finding the fixed sensor node that is the closest to the asset. The range of the mobile node is limited so that only one fixed node can receive the positioning beacons. The resulting accuracy depends on how far the fixed sensor nodes are placed from each other. Weighted algorithm A more advanced solution is the weighted algorithm. Weights between fixed nodes are calculated based on the received signal strength. These weights are subsequently used for triangulation. This method allows us to compensate the fluctuating RSSI values. Using this solution, an indoor accuracy of 5m can be achieved in one room. However, larger fluctuations occur in hallways due to multipath fading and reflection. Map-based intelligence An error that often occurs in the previous solutions is that the user can walk “through walls”, i.e. the position of the user is erroneously switched to a neighbouring room. In order to solve this, we use the map information to determine the exact room. More precisely, with each door a sensor node is associated and we have to pass by this node in order to enter or leave a room. Map information was received by TeleAtlas. Hybrid Solution Finally, we have implemented a hybrid solution that combines the three solutions above. This has lead to an average accuracy of 3m, both in hallways as in larger rooms. This accuracy is linked to the node density and will most likely increase when the node density decreases. Further testing is needed to investigate this effect. DEUS Proof of Concept implementation The DEUS positioning solution can be used for indoor navigation. The user’s position is determined via the sensor network and navigation info is given to the user by a GUI interface. The map info is provided by TeleAtlas and the navigation software by GeoSolutions.
  4. 4. DEUS Deployment and Ease Use of wireless Services Project partners In cooperation with IBBT research groups UGent - IBCN http://www.ibcn.intec.ugent.be UGent - WiCa http://www.wica.intec.ugent.be UA - PATS http.www.pats.ua.ac.be KU Leuven – DistriNet http.www.distrinet.cs.kuleuven.be KU Leuven – CUO http://ww.soc.kuleuven.be/com/mediac/cuo UHasselt - EDM http://www.edm.uhasselt.be/