Indoor Positioning System defines the tracking and monitoring of the people or objects inside the buildings. IPS is an acronym that stands for Indoor Positioning System. So basically, it is like a GPS for indoor positioning. In short, IPS is a network of devices. Consequently, it can communicate with internal sensors in Smartphones or Tablets. Above all, it uses mathematical algorithms to calculate indoor positioning with various technologies.
Position Trilateration Indoor Positioning System
Trilateration is a very common position calculation technique or method. It is defined as the process of determining absolute locations of points by measurement of distances, using the geometry of shapes for example circles, spheres, or triangles. The Venn diagram offers individual and intersecting points of circles. Similarly, Trilateration works by finding the intersection of a series of circles. In addition, It uses the known distance from at least three fixed points in 2D space or four fixed points in 3D space to calculate the position of an object. In other words, it is relatively simple since it uses common hardware and requires relatively simple math.
Source: Wikipedia
Technologies used for Indoor Positioning System
- Wireless fidelity
- Visible light communication
- Bluetooth low energy beacons
- Radio Frequency Identification
1. Wireless Fidelity(Wi-Fi)
Wi-Fi determines the user positions based on the received signal strength(RSS), indication, and information. A WLAN (Wireless Local Area Network) consisting of wireless Access Points(AP) enables locations, monitoring, and tracking in complex environments. Moreover, as a part of the IEEE 802.11 protocol, it uses Wi-Fi RTT(round-trip timing). Consequently, devices will be able to use the time of flight (ToF). After that consequently, it determines the distance from AP. For instance, Raspberry Pi-based IPS.
Raspberry Pi based IPS
Here, 4 Wi-Fi access points (APs) distributed along the experiment floor. The client’s mobile is an Android Smartphone and nothing was added to the mobile. Above all, the client’s Smartphone operates as a server as well. All of this was done by software. Firstly and after setup of the system, a calibration (radio map building) is needed before start locating the mobile client. After that, whenever a mobile client wants to be located, the mobile client receives the beacons being sent from APs and uses some algorithms to find the coordinates. In addition, the received signal strength (RSS) at each Raspberry Pi is needed to measure the path loss.
Source: ResearchGate
2. Visible light communication(VLC)
VLC uses visible light signals to light the particular space and subsequently transmit the information for tracking the position of a particular object or person. Firstly, the LED transmits periodical signals with different frequencies enough to avoid flickering. Further, these signals are recognized by the mobile-camera. After that the calculations for positioning take place.
Moreover, The updated version of the VLC is Li-Fi(light fidelity). So, Li-Fi is also a wireless communication technology that uses light to transmit the data and position coordinates between devices in the same vein as VLC.
3. Bluetooth low energy (BLE) beacons
Bluetooth is a form of wireless communication and designed especially for short-distance communication. It uses so-called BLE beacons (iBeacons) for the same purpose. A mobile device that detects the signal from the beacons and can roughly calculate the distance to beacons and therefore can estimate the location. In addition, Beacon contains a CPU, radio, and batteries and It repeatedly broadcasts the identifier. This is to say that the identifier is nothing but a unique ID and that is recognized by Smartphones and mark-out important places in them.
4. Radio Frequency Identification(RFID)
RFID is a simple technology that comprises RFID Tags or Cards and a Reader. RFID Reader consisting of a micro-controller, signal generator, and feedback signal receiver. It uses a radiofrequency electromagnetic field to read the data from the Tag and similarly for the Card.
In addition, firstly the reader continuously sends radio waves and during that period whenever the Tag or the Card is in the range, the reader receives a feed-back signal. After that using a load modulation technique reader reads the data of the particular RFID tag or the card. To clarify, the identification of the object’s location has been done by the tag or the card which is attached to the object.
COMPARISION
| Technology | Location | Accuracy | Range | Cost | Used for |
| Wi-Fi | Indoor/Outdoor | 5 -15 m | <150 m | Medium | Establishment of Wi-Fi is must for meter accuracy. |
| VLC | Indoor | <50 cm | <8 m | High | Indoor tracking, Smart lighting industry. |
| BLE Beacons | Indoor/Outdoor | ≤3 m | <30 m | Low | Peer-to-peer messaging, Passive notification. |
| RFID | Indoor | <10 cm | <100 m | High | Tracking of inventory, requirements for centimeter accuracy. |
CONCLUSION
In conclusion, various technologies for Indoor Positioning and their comparison are described. The selection of technology can be confusing. However, a comparison can be helpful for making a decision regarding the same. In short, based on the requirements of accuracy, range, and costing the client can install a system and get the appropriate positioning. To sum up it is a technology that allows us to accurately pinpoint the location of people or assets. In other words, it is a user-friendly system that can enhance indoor mapping inside buildings like malls, universities, theaters, auditoriums, etc.
