This blog is part two of a six part series dedicated to locating Low-Power Wide-Area Network (LPWAN) IoT devices. In our first post, we discussed locating Ingenu IoT devices. This post looks at the practical challenges associated with locating devices that communicate via the LoRa LPWAN protocol.
In the Internet of Things, millions of connected "things" record and communicate important data via the internet to central platforms or other “things”. With predictions of more than 20 billion connected devices by 2020 (Gartner), scale and cost are very important. LPWAN addresses these challenges by providing efficient, long range communications capabilities enabling devices to transmit small amounts of data (per device) at a lower cost.
Accurately and efficiently locating mobile "things" provides a key data element in an integrated IoT strategy. With its power, bandwidth and cost constraints, LPWAN presents unique location challenges.
Per the LoRa Alliance, “LoRa or LoRaWAN™ is a specification intended for wireless battery operated Things in a regional, national or global network.” The ideal use case for LoRa involves small industrial devices that transmit small amounts of data infrequently and move within an area where LoRa infrastructure is deployed.
Like other LPWAN technologies, LoRa's ability to transmit small amounts of data over very long distances while using very little power translates to lower costs. However, LoRa is a “specification”, rather than a technology per se. As long as they develop to the specification, individual companies are able to create their own LoRa infrastructure, albeit after paying a license to Semtech, the inventor.
Locating LoRa Devices
LoRa has a “built-in” location technology called Differential Time of Arrival (otherwise known as Time Difference of Arrival or TDOA) that locates devices using the cellular infrastructure, in this case LoRa gateways. Because the gateways are able to collect and transmit timing information, the devices can be located by comparing the times the signals arrive at multiple gateways.
For LoRa networks, TDOA is the least cost location method as it leverages the existing capabilities of the network and devices. However, if better accuracy is needed, Wi-Fi is advantageous over GPS in terms of cost and battery drain, and over Cell-based methods in terms of accuracy.
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