Indoor localization is the process of locating people or objects in a large indoor environment such as an office space, a healthcare facility, a museum, an educational center, or a mass transport facility. Based on wireless technologies such as WiFi, Radio Frequency Identification Device (RFID), Ultra-wide Band (UWB), etc., indoor localization techniques aid in optimal facility management and support smart architecture such as smart buildings and smart cities.
This post discusses key aspects of each indoor localization technique and presents technological aspects which support in successfully implementing an indoor localization system.
Also read our blog How Does An Indoor Navigation System Technology Work in Locating Assets?
Making Indoor Localization Possible: Wireless Technologies
Used primarily for connecting different devices to the internet and provide networking capabilities to the user, WiFi is one of the most popular wireless technologies in the 21st century. As most devices such as Smartphones, tablets and personal computers are enabled for WiFi, it makes this wireless technology cost-effective as well as ubiquitous.
Usage of Bluetooth for connecting devices and sharing data has been a common practice at indoor environments as it allows for hassle-free exchange of information within limited spaces. However, with the introduction of Bluetooth Low Energy (BLE), the data rate has improved in addition to the coverage range which is now around 70-90 meters.
Being the latest in entrant in wireless technologies which power indoor localization, Zigbee is widely used in home automation and to crate personal area networks. Zigbee’s range is around 10 – 20 meters, hence it is not effective in large indoor environments.
Radio Frequency Identification Device (RFID)
This technology uses electromagnetic radio waves for transferring or storing data in large indoor environments. RFID systems can operate at wide distances and are therefore quite effective indoor localization system.
Ultra-wide Band (UWB)
Despite its use as a short-range communication system, UWB has gained significant usage as an indoor application since other signals cannot interfere with its transmission. UWB signals can penetrate a wide variety of materials including walls.
Light Emitting Diodes (LED) acts as Beacons to transmit signal and data which is then picked up by receivers for indoor localization. An emerging technology, Visible Light Communication (VLC) uses certain ranges of visible light for high-speed data transfer.
Indoor Localization: Key Aspects of Technologies
Received Signal Strength Indicator (RSSI)
This is one of the simplest and hence widely used approach for indoor localization.
While RSSI is easy to install & implement, cost-effective, and can be used in combination with multiple other technologies, it is prone to lower localization accuracy and environmental noise.
RSSI requires fingerprinting for indoor localization accuracy.
Channel State Information (CSI)
CSI provides better multipath information, more stable measurements, and higher localization accuracy when compared to RSSI.
However, despite its robust compatibility and good quality output, CSI is yet to gain popularity. It’s availability also is a major concern.
This technology requires an environmental survey to obtain fingerprints or features of the environment where localization has to be installed.
While Fingerprinting/Scene Analysis is fairly easy to use it is quite intricate as new fingerprints will be required each time there is a minor variation in the indoor space.
Angle of Arrival (AoA)
This approach uses antennae arrays to estimate the angle at which the signal intrudes on the receiver, by exploiting and calculating the time difference of arrival.
The prime advantage of AoA is that user location can be estimated in both 2D and 3D environments with the right infrastructure.
AoA provides high location accuracy but requires complex hardware and components, apart from the risk of decreasing performance with increase in distance between transmitter and receiver.
Return Time of Flight (RToF)
This technology measures the transmitter-receiver-transmitter signal propagation time for indoor localization.
While RToF provides high accuracy and does not require any fingerprinting, it requires clock synchronization, and there could be processing delay for shorter range measurements.
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