What are indoor positioning systems?
Indoor positioning systems (IPS) are the indoor equivalent of what GPS offers outdoors: visibility. They are able to locate people and objects inside buildings, usually using a mobile device, like a smartphone or tablet.
IPS relies on technologies like wall- or ceiling-mounted beacons that work together in detecting a user’s or object’s location, deriving accurate positioning, according to Senion. IPS systems can then detect the direction in which the device is traveling, and can predict the user’s pathway based on that information so the positioning remains accurate as the space is traversed.
Challenges of working indoor
Indoor environments are much more complex than outdoor environments because there are multiple objects that reflect signals and lead to delay problems. Also, due to the existence of various objects, indoor environments typically rely on non-line-of-sight (NLoS) propagation, when signals cannot travel directly in straight path from an emitter to a receiver which causes inconsistent time delays at the receiver
“Indoor navigation is very, very tricky,” said Kaveh Pahlavan, a professor of electrical and computer engineering at Worcester Polytechnic Institute, in Massachusetts, to the IEEE. “The fact is, what industry selects is important. Today, Wi-Fi localization is the most popular.”
There is currently no standard for an IPS system, with companies like Google, Huawei, Samsung and Apple all using different technologies to create their own indoor positioning systems.
Wireless solutions to IPS
Here are some technologies that are being used to create indoor positioning systems, many of which are combined for greater accuracy and range.
Wi-Fi-based positioning system (WPS)
Wi-Fi positioning system (WPS) is often used where GPS is inadequate. The most common technique used for Wi-Fi IPS is measuring the intensity of the received signal and the method of “fingerprinting.” According to a University of Pittsburg report, the fingerprinting technique associates location-dependent characteristics such as received signal strength to a location and uses these characteristics to infer the location. The advantage of this technique is that it is simple to deploy with no specialized hardware required. Any existing wireless local area network infrastructure can be reused for this kind of positioning system
https://www.youtube.com/watch?v=R3xGz1R__oI
Infsoft provides a list of pros and cons for using Wi-Fi as a solution:
Pros:
- indoor positioning works without GPS
- existing WiFi infrastructure can be used
- enabled WiFi is sufficient
- there is a back channel to the client
- large range (up to 150m)
- detects floor level
Cons:
- relatively inaccurate (5-15m) compared to BLE/RFID
- WiFi client based positioning is not possible with iOS devices – but BLE can be used as an alternative
- application required
Bluetooth
According to infsoft, Bluetooth is a good alternative to GPS for indoor positioning and indoor navigation. Bluetooth beacons are able to send out signals, but they can’t receive them. They are relatively cheap, can run on button cells up to two years and have a maximum range of 30 meters indoors and accuracy up to one meter.
Here are pros and cons of using Bluetooth for IPS, according to infsoft.
Pros:
- cost-effective, unremarkable hardware
- low energy consumption
- flexible integration into the existing infrastructure (battery-powered or power supply via lamps and the domestic electrical system)
- works where other positioning techniques do not have a signal
- compatible with iOS and Android
- high accuracy compared to WiFi (up to 1m)
Cons:
- additional hardware
- app is required for client based solutions
- relatively small range (up to 30m)
RFID
RFID is a promising technology for use in indoor positioning systems. Deployment is relatively low cost, and installation is simple.
RFID-based techniques provide a relatively large coverage area by a small number of devices, but they may have significant multi-path effects.
According to a paper by researchers at RMIT University in Australia, the advantages of RFID techniques for indoor positioning include:
- Simplicity of the system;
- Low-cost of the device;
- High portability;
- Ease of maintenance;
- Capability of providing both identification and location;
- A long effective range (up to 1000 m for a single transmitter in free space);
- High penetration capabilities;
- Flexible in tag size.
And the disadvantages of using RFID in indoor positioning are as follows:
- One-way communication links;
- Multipath effects;
- Unstable Received Signal Strength (RSS).
Ultrawide band (UWB)
With the use of ultra-wideband technology, it is possible to achieve indoor 3D positioning with centimeter accuracy. The ultra-wideband technology provides wireless message communication that enables automation and communication. The accuracy achieved with this ultra-wideband technology is several times better than traditional positioning systems based on WiFi, Bluetooth, RFID or GPS signals. Furthermore, the signals can penetrate walls and make it suitable for indoor environments, according to Pozyx.
The Federal Communications Commission (FCC) defines UWB as an RF signal occupying a portion of the frequency spectrum that is greater than 20% of the center carrier frequency, or has a bandwidth greater than 500 MHz. UWB is a communication channel that spreads information out over a wide portion of the frequency spectrum. This allows UWB transmitters to transmit large amounts of data while consuming little transmit energy.
Infrared (IR)
Infrared wireless communication makes use of the invisible spectrum of light just below the red edge of the visible spectrum, which makes this technology less intrusive than indoor positioning that is based on visible light. The Infrared Data Association (IrDA) uses a point-to-point data transmission standard designed for very low-power communications. IrDA requires line of sight communication between devices over a very short distance and up to 16 Mbps. On the other hand, diffuse IR has stronger signals than direct IR, and therefore it has a longer reach (9–12 m). Diffuse IR uses wide angle LEDs which emit signals in many directions, which means it does not require direct line of sight.
ZigBee
ZigBee is a low-power wireless local area network (WLAN) specification that was designed to provide small amounts of data using very little power, with most connected devices running off of a battery. Because of this, the open standard has been linked with machine-to-machine (M2M) communication and the industrial internet of things (IoT).
Unlike Wi-Fi, ZigBee uses a mesh network specification where devices are connected with many interconnections between other network nodes. Data is generally sent through mid-range distances of 10 to 100 meters, but ZigBee uses its mesh network to significantly extend that distance.
Practical applications
IPSs can be used for different IoT applications in private homes and IIoT solutions in public building applications. It can help detect and track items, providing assistance for elderly and disabled people in their daily activities and facilitating medical monitoring for vital signs and emergencies.
Public buildings can provide indoor navigation systems for blind and visually impaired people, and hospitals can use IPS to track patients and expensive equipment.
IPS can also help locate you within your house or a large department store or mall. Shopping centers can use the technology to send promotions and notifications of products that are within close proximity of shoppers.
