## 6 Case of Study: IPS at St. Olavs Hospital
### Mechanism of Performing of EBIM IPS in St. Olavs Hospital  
In general, IPS is related to technologies that facilitate the network of devices to locate objects and people. In this regard, location engines have a key role in estimating and calculating the position of an object being tracked [26]. The location can be computed by using a combination of geometry, topography, and algorithms filters. Cisco Mobility Services Engine (MSE) [33] is a location engine that is used to gather tracking data from different environments and employs them in other applications. It can be run as a physical or virtual device and obtain data from RTLS tags which are linked to the Wi-Fi network. RTLS tag beacons are collected by one or more Wi-Fi access points (Wi-Fi AP) and the picked-up information is used to compute and estimate the position of the tags. By using Wi-Fi hotspots in a building for interior spaces, multipurpose use is possible. It is important to position Wi-Fi AP in a way that enhances the accuracy of the measurement. This means that Wi-Fi AP should be located near walls and, in the case of large spaces, they should be placed in the center of the room (Figure 4) [18]. In St. Olavs Hospital, Cisco MSE obtains the relevant data from AP on the Wi-Fi network and uses the time difference of arrival (TDOA) and received signal strength indication (RSSI) to compute tag locations. Accordingly, Cisco MSE computes positional floor plan coordinates for the tag based on TDOA and RSSI. The precise positioning data for the tags are sent by using a TCP (transmission control protocol) stream from the Cisco MSE server to the model server, where the Windows service is running. The Windows service is installed on the model server with the aim of obtaining the location of data as a TCP stream from the Cisco MSE server. The service loops constantly and it waits for new information to arrive. When data are imported, it strives to process them and save any XML (extensible markup language) files, before waiting for more information. Indeed, the files received by the Windows service from Cisco MSE must be analyzed and imported to the EBIM system. Therefore, it is necessary that all received XML files have all the attributes and values in each of them. Positioning data are ultimately visualized for the end user through a web application known as the St. Olavs Eiendoms portal. It allows users to search for and find their equipment with a mounted tag at the hospital [18]. In other words, the TCP stream service creates a communication with Cisco MSE and collects the data stream collected from the asset tags (Figure 5). Subsequently, the required data will be written by the service to an XML file that contains features such as the current location and time, and stores it in a defined folder [26]. When data are saved as objects in the database, the objects must be linked to the structural model in which they are located. In this instance, tags as an object have potential to move among different buildings of the hospital, and they present the possibility to switch between the building models that they belong to. When a tag is inserted into the database as an object, it is presented with numerous attributes. Then, more features can be assigned to the tags, such as IDs for  
Figure 4: Simple illustrations summarizing the access point placement concepts. Adapted from [18]. equipment mounted on them. The tags are saved as devices with all tracking records which are linked to each tag. Each time a tag sends a beacon, it indicates its location and the tracking data are saved as a track record for each tag. The track records are added to a list for the appropriate tag, and they provide the possibility to see the tag's position. The main features in these track records are time, floor, longitude and latitude. The time stamp creates information about the time that the tag sent its location.