Your Low-Power Wide-Area Network: Selecting The Best Location Positioning Option

Low-power wide-area network (LPWAN) first surfaced as a result of the need for IoT devices to be smaller and cheaper, while also maintaining battery efficiency and meeting all form requirements. By providing long-distance, low-power, and low-bandwidth communication, LPWANs meet the operating needs of many IoT use cases. They reduce both the cost and the battery consumption of the devices, which not only extends the life, but also decreases both the size and cost of their operational overhead. In many of these use cases, the performance is dependent on one critical feature: accurate location capabilities. These location methods can include GNNS, WiFi positioning, and more.

A big chunk of future growth in 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 all of which offer these unique capabilities. These networks have use cases including asset tracking solutions, smart city infrastructure, and smart metering. Let's discuss how to choose the best location positioning option depending on the use case needs.

LoRaWAN: The Low-Power Wide-Area Network Specification

Low- power wide-area networks 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 devices periodically transmit and receive small amounts of data.

LoRaWAN is an LPWAN specification intended for wireless battery operated devices in a regional, national or global network. The ideal use case for LoRa, or long-range radio, involves small industrial devices that transmit small amounts of data infrequently and move within an area where LoRa infrastructure is deployed.  From reducing energy bills, 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.

Built-In Location Technology for Low-Power Wide-Are Networks

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, that being the LoRa gateways. Location of mobile phones and devices using TDOA was developed more than 20 years ago. 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, 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 low-power wide-area network base stations deployed. As mentioned, this varies greatly 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, which is an advantage for deployment costs, but a challenge for TDOA. This is where GNSS or WiFi come in to provide the most accurate and cost-effective location capabilities.

GNSS & WiFi Positioning: The Advantages and Disadvantages

Satellite-based location methods like Global Navigation Satellite System (GNSS) seem to have more negative aspects than positives. First, let's look at one strong advantage: GNSS devices are very accurate in areas where the satellites can be seen by the device, such as an outdoor environment. This can help, especially when other location positioning options are not accurate outdoors. Now, let's move on to the disadvantages.

Disadvantages of GNSS:

• Not very accurate indoors
• Not very accurate in dense urban environments, such as most cities
• GNSS chipsets and receivers may be expensive
• Can drain the device battery, offsetting some of LPWAN's main benefits

WiFi positioning, another location positioning option, uses existing infrastructure and WiFi access points (APs). For WiFi location, the device must be able to scan for nearby access points (APs) and transmit the information over LoRa where the low-power wide-area network can determine the device’s location. The device needs to be able to see the WiFi AP, but it does not need to connect to it.

Advantages of WiFi Positioning

• Optimal because it can be combined with other signals (hybrid) to create an improved location system compared to any single choice on its own
• Provides indoor location capability and accuracy
• Significant cost advantage because gateway over-deployment is not required to reach an equivalent level of accurate
• Can achieve 15-30 meter accuracy in urban environments due to higher APs

Disadvantages of WiFi Positioning

• Incremental power consumed by a WiFi scan relative to TDOA. This is a tradeoff for a significantly improved indoor and outdoor location
• Less optimal location accuracy in rural areas due to less APs

In use cases where precise location tracking is critical, WiFi positioning is a clear winner. Combining WiFi location with low-power wide-area network-based location improves the overall location accuracy and reliability across the network. Also, by adding WiFi location to the system, it extends the reach of devices and provides a higher precision location technology. Lastly, by acquiring a WiFi scan and sending that to the network for localization, the battery drain to the device is minimized. These benefits make WiFi an optimal choice for low-power wide-area deployments.

The Takeaway For Your Low-Power Wide-Area Network

Low-power wide-area networks work to reduce costs and battery usage of devices, providing smarter use opportunities. However, the performance of these networks depends on accurate location capabilities. Selecting the correct location positioning option will ensure proper functioning. When precise location tracking is necessary, WiFi positioning should be used as it improves the overall location accuracy and reliability across the network.