Author: Varun Singla, Technical Test Lead
Location these days carry a lot of importance in indoors as well as outdoors. Outdoor localization, these days is, widely used in many applications with the help of versatile sensors and technologies like GPS, accelerometer, gyroscope etc.
People have been exploiting these technologies in various applications like vehicle tracking, booking the cabs, sending locations through apps like WhatsApp etc. Realizing the importance of outdoor localization, locating humans indoors is also very interesting and important. An Indoor location is as important as outdoor, as it carries a lot of value commercially and for various organizations like IT companies, Shopping Malls etc. Timely advertisements and offers can be displayed on users' smartphones while based on his/her location in the shopping mall to increase the sale. Various organizations are interested in resource management and infrastructure management for maximum utilization.
Locating the user precisely in an indoor environment, that where he exactly is, on which floor and on which location, is the Indoor Localization.
This can be achieved through variety of methods:
Fig. 1. An illustration of device-based and device-free indoor localization systems 
Figure 1 illustrates the device free and device based indoor localization systems. Device based systems are those where the user has to carry a device with him/her whereas in the device free systems user need not to carry any devices with them. In this blog I will discuss about one Wi-Fi based device based.
Device Based Method
Most common device based methods these days exploit the smartphones of the users as each and every individual carries the smartphones and it does not add to any extra costs. Figure 2 below shows the reality of smartphones, and the sensors available in today's smartphones. There are a wide variety of sensors available in the phones, which are capable of doing almost anything. All kind of modalities (e.g., WiFi, cellular, FM radio, Bluetooth, microphone, inertial sensors, etc.) can be used separately or integrally for localization purposes.
Fig. 2. Candidate sensing modalities on smartphones for indoor localization
Wi-Fi based method
In Wi-Fi based techniques the existing infrastructure is used as can be seen in Figure 3. First of all, the entire building is divided into the landmarks. Maybe each cubicle can be a landmark on each floor, which means number of landmarks can be equal to the number of cubicles. Similarly, each table can be a unique landmark in a food court.
After this all the landmarks are fingerprinted, with the RSSI values reported by different Access Points from the smartphones. An example can be taken from Figure 3: Let's assume to take the fingerprints at that landmark where the phone is. As can be seen, this phone is reported by three different APs (AP1, AP2 and AP3). Suppose the signal strength of AP1 to this Phone is say X, and from AP2 is X-1 and from AP3 is X+1. Then the finger prints at this landmark will be:
A database of fingerprints is then developed. When users move around in real time in the organization, this database is consulted every time to figure out which database fingerprints closely match to the reported RSSI values. Accordingly, the location of a person is determined in the real time.
How it can be used in an organization like Infosys
This technique can be used to manage the resources of the company. Heat maps of an organization can be generated, with which it can be estimated which conference rooms, meeting rooms, etc are occupied, or which cubicles are occupied and which are empty.
Fig. 3. An overview of WiFi-based indoor localization systems
One more interesting application of this technique is to manage the staff. An example to this is: if access points be installed in wash rooms or nearby areas, then it can be reflected through heat maps, that which washrooms are more occupied. This information can be exploited by the cleaning staff, or their manager to decide, where more cleaning people are used and where less. This can lead to more efficient use of resources and staff within the organization.
There are various other methods which can be used for indoor localization other than using Wi-Fi. These solutions include:
- Bluetooth based solutions
- Wi-Fi + Acoustics
- Inertial Sensors
Wi-Fi based solutions are easy to deploy as most of the leading organizations these days are equipped with Wi-Fi Access points and achieve these type of solutions, one does not need to spend on any additional infrastructure. So the solution can be achieved in the existing infrastructure which almost no additional hardware costs.
Xiao, Jiang, et al. "A Survey on Wireless Indoor Localization from the Device Perspective." ACM Computing Surveys (CSUR) 49.2 (2016): 25.