As the term Internet of Things (IoT) became commonplace, the early predictions of the rapid growth in the amount of more or less sophisticated devices connected to the Internet are being partially fulfilled by an increasing number of real-life implementations.
Besides the SigFox, ZigBee, Bluetooth LE (4.0), LTE-M, IQRF or any other IoT technologies, LoRa is a wireless radio-frequency technology developed as a radio physical layer mostly for long-range machine to machine communication (M2M) which is considered within the IoT concept. Not only thanks to its low energy consumption it is predetermined for future usage in more up-to-date IoT – smart measuring, monitoring or other control reporting devices. The key enabler of this predetermined development is the increasing coverage by the LPWAN in unlicensed spectra extending the availability of IoT solutions to any public or private networks operators as opposed to licensed spectra preferably intended for cellular network operators.
For connection establishing and maintaining among the involved machines, LoRa uses a LoRaWAN link layer protocol. This protocol allows communication with data rate from 0.3 kbps to 50 kbps (1). In some cases, such data rate is more than the device requires for its primary functionality. There comes the idea of using several data bytes to for position calculation. Assuming that LoRa becomes popular in future M2M communication, there will be a vast number of these devices. Many of the M2M applications could find helpful if there was a possibility of an overview about devices location.
A solution like LoRa localizing technology would be requested especially with applications where GPS is not the best choice e.g in places where the GPS signal coverage is not sufficient as many of the LoRa endpoint devices endpoints sending the data packets from the sensors via a radio channel to a gateway and further to the network – are unable to receive weak signal with GPS message as they can often be placed in a cellar or somewhere in a strong signal attenuation or fading environment like a factory hall.
Furthermore, the price for the extension GPS receiving chip and its energy consumption is comparable with the whole LoRa endpoint device. Hence, using additional GPS chip would cost money and the advantage of the long battery life. If we imagined an area of use where the accuracy of the determined position doesn’t have to be as excellent, it would be very tempting to obtain the localization feature only with updating your LoRa device firmware.
LoRa, LoRaWAN technology
LoRa, as a physical layer wireless technology, was developed to provide long-range radio connection between IoT devices and a network, usually the internet. The IoT devices, usually sensors, actuators and other types of machines, which in LoRa terminology are considered as nodes, sends data to the network, where the data can be processed, via base stations, in LoRa terminology called gateways. LoRaWAN provides a protocol for communication between the IoT devices and the network, including QoS and security mechanisms, and defines the logical architecture of the LoRaWAN network ().
Neither manufacturers nor LoRa Alliance, which is an association responsible for standard certification [5], do not specify any physical network architecture – the network can be realized arbitrarily. In general, the deployed networks can use a mesh topology, or a star topology or any other. However, the chosen topology affects the connectivity range or battery lifetime. In a LoRaWAN network, nodes are not associated with a specific gateway. Instead, data transmitted by a node is typically received by multiple gateways, depending on a distance between the node and the gateway. Each gateway will forward (viz. packet forwarder) the received packet from the node to the network server via backhaul connection (Wi-Fi, 3G or Ethernet)(3). Then, the network server can remove redundant received packets, perform security checks and schedule acknowledgment messages through the optimal gateway. The figure below illustrates possible reception of the data packet coming from the node to the gateway. As we can see, thanks to the high sensitivity of the gateway receiver, the reception ranges of the gateways are overlapped.