# A Low Energy IoT Application Using Beacon for Indoor Localization
## 2 Related Works  
Unlike what happens for an outdoor location, an indoor one cannot refer to and rely on a single technology; for this reason, it is much more complex. Indoor localization, therefore, requires both instruments other than satellite ones--that is, it cannot depend on the use of GPS--and knowledge of the nature of the environment in which the localization must be implemented [15]. To compensate for the ineffectiveness of the GPS signal in an indoor environment, localization systems have been designed based both on different sensing technologies, such as defined radio localization--technologies such as Wi-Fi and Bluetooth--and on methods that require a priori knowledge of the structure where the indoor localization system is to be applied (an example is dead reckoning). All these technologies used today for indoor localization differ in terms of accuracy, costs and efforts, although in recent years, there has been a marked improvement in the accuracy-cost ratio. Radio localization is a method that allows the estimation of the position in real time through the use of radio antennas arranged in fixed and well-defined positions known a priori. A technology that is widely used in indoor environments is Bluetooth: \"small Bluetooth antennas are used that allow you to interact with the mobile phones of people who are at distances up to 70 m from the antenna\". Bluetooth technology is widely used in not very large environments, so all signals transmitted by the antennas are received by the device. These particular antennas, which appear to be inexpensive, small and with a long battery life, take advantage of a low-power, wireless connectivity, defined as BLE--Bluetooth low energy [16]. With BLE technology, it is possible to take advantage of Wi-Fi connectivity: the results are good in closed environments and fragmented by walls, such as hospitals or buildings, where the solution is used to track in real time the positioning of assets such as medical equipment or hospital operators. The most used method under WLAN connection to locate the user, who must have a device with Wi-Fi connectivity with them, is to exploit the power of the signals sent to the device by the access points at regular intervals of time. Another technology that follows Wi-Fi and Bluetooth is that of Ultra WideBand (UWB). This technology represents a method capable of providing, with low energy consumption, a short-range communication but at high speed. Ultra WideBand does nothing but send many short duration pulses so as to be able to filter the signals reflected from the original signal: in other words, the low frequency of UWB pulses allows the signal to pass effectively through obstacles, such as walls and objects. This last statement makes us understand how this technology is widely used to improve the accuracy of the position calculation [17; 18]. Another method that can be used is represented by dead reckoning: the positioning is determined starting from a previously known position, using an estimate of speed, direction and time. It is possible to determine these estimates through elementary movements, such as walking or running, using mechanical and electrical sensors: in this way, the values of speed, direction and time are obtained [17; 19]. RFID technology, on the other hand, consists of three fundamental elements:  
* Tag: A small electronic device consisting of a microchip with simple control logic functions connected to an antenna, both mounted on a substrate, similar to an adhesive label, which supports them. This chip (of a few millimeters) represents the smart part and consists of a non-volatile memory and a unique code, which is transmitted to the reader, which has the task of processing all the data received;
* Reader: A transceiver controlled by a microprocessor, used to receive and acquire the information from the tags;
* Management System: A system that allows, starting from the univocal code, to retrieve all the various information available and to manage them.