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Indoor localization using Bluetooth low energy
During the last couple of years, there was a change in demand for Bluetooth technology. Bluetooth devices are not a new technology, but in recent years the Bluetooth technology is used for different new applications, especially with the energy saving version of Bluetooth: Bluetooth Low Energy(BLE).
Today, navigation systems such as GPS are available for everyone. But when it comes to a highly dense area with a minimum line of sight such as inside a building, the GPS systems fail to provide accurate data. For such indoor positioning, Bluetooth devices are employed. Wifi enabled indoor navigation systems are also available, but the low cost, low energy Bluetooth devices are preferable.
Bluetooth indoor navigations can be implemented in two ways. One is the client side solution in which only a Bluetooth enabled smartphone is used and the data are collected using some mobile applications. On the other hand, that is the server-based solutions use Bluetooth beacons for tracking objects.
An indoor positioning system is a system to locate objects or people within a limited area by calculating the distance of the object which transmits some radiations, from a receiver that collect the transmitted waves and estimate the location of that object.
Indoor localizations are usually done through analyzing the strength of radio waves. This method is called Received Signal Strength Indicator(RSSI). The Bluetooth devices covering a limited area transmits the radio signals that are captured by a receiver that calculates the strength of received signals and thus the distance of the transmitting device from the receiver. The ordinary Bluetooth called the Bluetooth Classic was not satisfactory enough to be used for indoor localization because it requires more time to find a nearby Bluetooth device and the scenario changed by the discovery of Bluetooth 4.0(BLE). It is a low cost, low energy consuming device that also requires less time for configuration. One more reason that prefers the Bluetooth is that it does not require any routing devices that are used by today’s wifi systems.
Bluetooth beacons are small devices that can replace the wifi access points. These beacons are more accurate than wifi. Beacon is a transmitter that contains a Bluetooth and a transmitting antenna. A powerful receiver is also employed that is enabled with Bluetooth 4.0 or upgraded version. The transmitting device broadcast Bluetooth packets that consist of-
- MAC address
- UUID(Universal Unique Identifier)
Other parameters such as transmitting power can be configured with the transmitting packet.
The hardware specifications are,
- Protocol: Bluetooth 4.0
- RX sensitivity : 103 dBm
- Range: 30 m
- Consumption : sleep(0.4uA)/RX (8 mA)
Bluetooth beacons are used mainly for home automation systems and for location-based content reception and also for navigation through a building. Android support for BLE enables it to be used in many scenarios. BLE enabled mobile phones can be tracked within the range of Bluetooth receiver. This tracking system is used in many complex buildings for advertising or to find the visitors flow. In this case, the android phones act like the receiver, it receives the radio waves transmitting from another Bluetooth device fixed at some point. When the mobile phone approaches the transmitting device some actions can be triggered in the phone such as popping up a notification or something. From API level 18 (version 4.3), Android supports BLE. From API level 21 (version 5) onwards, Android provides separate package for Bluetooth configuration. Android offers a Bluetooth Manager class that scans for nearby Bluetooth devices automatically.
Organizations use BLE navigation methods to provide a better service to the customers. Practical applications of BLE positioning are,
- Shops can advertise their product through notifications to the mobile phones
- A location-based narration system in a museum or at any places with the help of a map.
- Location-based home automation systems
- For analyzing the visitor flow or crowd
Bluetooth beacon devices are independent and do not interfere with other signals. So they are more secure. Interference can occur in a situation when BLE is used along with a lot of Wi-Fi signals where both the Bluetooth and wifi uses same frequency(2.4GHz) for transmitting signals. But this problem can be eliminated configuring the channels used for transmission of signals from Wi-Fi and Bluetooth.