Posted by Larry Dodds
Low-power wide area networks (LPWAN) came about as a result of the need for IoT devices to be smaller and cheaper, while also maintaining battery efficiency and still meeting all form requirements. By providing long-distance, low-power, low-bandwidth communication, LPWANs meet the operating needs of many IoT use cases. It reduces both the cost and the battery consumption of the devices, which extends the life and decreases both the size and cost of the devices and their operational overhead. A big chunk of the future growth in the number of IoT devices is expected to come from low-power wide area networks. By 2025, it is expected that more than 2 billion devices will be connected through LPWAN.
There are several different networks, such as NB-IoT, LoRaWAN, Sigfox or LTE Cat-M that all offer unique capabilities and use cases that range from asset tracking solutions or smart city infrastructure to smart metering. In many of these use cases, the performance is dependent on one critical feature: accurate location capabilities. For this post, the primary focus will be on LoRaWAN™ and how to choose the best location positioning option depending on the use case needs.
LPWANs have a longer range than traditional mobile networks, enabling them to transmit small amounts of data (per device) at a lower cost. LPWANs are ideal for use cases where lots of very small, low-cost things periodically transmit and receive small amounts of data.
LoRaWAN is an LPWAN 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.
From smart city; reducing energy bills through smart lighting and optimized waste collection, to smart metering and supply chain and logistics, LoRaWAN’s opportunities are plentiful. That said, these use cases rely heavily on location to perform properly.
LoRa enables these applications using a type of “built-in” location technology called Time Difference of Arrival (TDOA). TDOA technology locates devices using the wireless infrastructure, in this case LoRa gateways. Location of mobile phones and devices using TDOA was pioneered by Skyhook more than 20 years ago as it worked to create an accurate location solution for use in E-911 and other applications. This work resulted in the development of a large intellectual property portfolio that patented many methods and systems for TDOA implementations. In the years since Skyhook’s early work, TDOA has been adapted to support native LoRa TDOA locations for IoT. 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.
Accuracy with TDOA is heavily reliant on the density of LPWAN base stations deployed which, as mentioned, varies greatly today by geography and morphology (urban versus suburban, etc.). While this wide area location may be acceptable for certain IoT use cases, TDOA may not be a cost effective option if a more accurate understanding of the position of the device is needed.
LoRa’s low range transmission capabilities mean that the network nodes are spaced far apart - an advantage for deployment costs but challenging for TDOA. This is where GNSS or Wi-Fi come in to provide the most accurate and cost-effective location capabilities
Satellite-based location methods like GNSS are very accurate in areas where the satellites can be seen by the device, like in an outdoor environment. However, GNSS is not accurate indoors or in dense urban environments like most cities. In addition, GNSS chipsets and receivers can be expensive and it also drains the battery which offsets some of LPWAN’s main benefits.
Then there’s Wi-Fi positioning. Wi-Fi location uses existing infrastructure and Wi-Fi access points (APs) to calculate location. For Wi-Fi location, the device must be able to scan for nearby APs and transmit the information over LoRa where the network can determine the device’s location. The device needs to be able to see the Wi-Fi AP but does not need to connect to it. Wi-Fi is optimal because it can be combined with other signals (hybrid) to create an improved location system compared to any single choice on its own and it also provides indoor location capability and accuracy. There is also a significant cost advantage of Wi-Fi because gateway over-deployment is not required to reach an equivalent level of accuracy. One disadvantage of using Wi-Fi is the incremental power consumed by a Wi-Fi scan relative to TDOA. While there are methods to minimize the power performed by a scan - this is a tradeoff for significantly improved indoor and outdoor location.
Like TDOA and cell-based methods, the higher the number of access points, the better the location accuracy. In urban or other environments with many APs, Wi-Fi can achieve 15-30-meter accuracy. In contrast, in rural areas that contain few APs, Wi-Fi may not be the optimal location solution.
eleven-x is a leading full-service low power IoT solution provider and operator of Canada’s first and only public coast-to-coast network optimized for IoT. They offer complete device to cloud LoRaWAN™ solutions, comprised of accurate and reliable sensor networks delivering secure data through easy to use dashboards and industry standard APIs.
“The idea of combining two teams who are experts in respective technology fields to develop a cost-efficient and long-lasting solution for location-based tracking was really exciting for us,” said eleven-x CEO, Dan Mathers. “The potential of this hybrid solution has the ability to really disrupt the current asset tracking space and specifically Smart Cities and industrial use cases where current GPS tracking solutions are simply too costly.”
Some of the key features of the eleven-x LoRaWAN IoT-optimized network include low power consumption, long range, scalability, reliability and high security measures, so data and privacy are always protected. Additionally, the units are battery operated and last for over ten years with almost zero maintenance, resulting in a low total cost of ownership.
eleven-x worked with Skyhook to build a Wi-Fi scanner in their XIU hardware platform. eleven-x also designed a custom-made mapping application to display location tracking. As a result, Skyhook could easily demonstrate the value of Wi-Fi location in a standard LoRa deployment. Wi-Fi makes a great addition to any LoRa network because it significantly reduces the cost required to “over deploy” LoRa gateways in order to achieve precise location in populated areas.
Skyhook performed testing with the eleven-x device in center city Philadelphia on the MachineQ LoRa network. This was an out of the box test with no calibration, no data collection and no integration with the network. The image below is an example of a walking test in and around the downtown area of Philadelphia.
In use cases where precise location tracking is critical, Wi-Fi positioning is a clear winner. Combining Wi-Fi location with LPWAN network-based location improves the overall location accuracy and reliability across the network. Also, by adding Wi-Fi location to the system, it extends the reach of devices and provides a higher precision location technology. Lastly, by acquiring a Wi-Fi scan and sending that to the network for localization, the battery drain to the device is minimized. These benefits make Wi-Fi an optimal choice for LPWAN deployments.