Wi-Fi and LoRaWAN work well together as an end-to-end solution in IoT applications and more.
If you’re in the process of implementing the Internet of Things (IoT), you’ve probably spent a lot of time researching wireless connectivity solutions, for which there are many (perhaps too many) choices. However, two — Wi-Fi and LoRaWAN — have a synergy that makes them very appealing as an end-to-end solution from the edge to the cloud. It’s the reason they’re being used together in applications from industrial facilities to entire cities throughout the world. To see why, let’s examine how they work so well together.
The Internet of things requires connectivity from the edge devices, such as various types of sensors, to the Internet. At the edge, a typical protocol choice is one of the 802.15.4-based standards, Bluetooth or Wi-Fi, as each one has mesh networking capability. From there, the data is transmitted to a gateway, and after that, to the Internet via either cellular or a low-power wireless area network.
Wi-Fi is the only protocol that can deliver blistering data rates, but its access points consume lots of power. Wi-Fi also has a line-of-sight range of only about 200 meters, uses channel bandwidths of 20 MHz or more, and as it operates at 2.4 and 5 GHz, doesn’t penetrate structures as well as lower frequencies. In contrast, edge devices using LoRaWAN consume microamps of current and can operate for years on a coin-cell battery. The protocol uses very narrow channel widths of 500 kHz or less and a maximum transmit power of 20 dBm (50 mW). Additionally, operation from 914 to 928 MHz in North America enables structure penetration and inherently long range.
The last metric, long-distance coverage, might seem counter-intuitive for a technology whose transmit power is minimal and antennas that are often electrically short. But because the LoRa radio uses chirp spectrum modulation and a correlation mechanism based on band-spreading, even extremely weak signals 19.5 dB below the noise level can be demodulated by the receiver. Not surprisingly, hobbyists have put this to the test, and their results were impressive, even amazing. Last July, a team of tinkerers in Spain set a record — 766 kilometers (476 mi.) — using balloon-mounted directional antennas and an RFM95W transceiver from Hope Electronics with RF output of 14 dBm (25 mW).
Why not just LoRaWAN alone?
It might be logical to assume that LoRaWAN could simply be used alone rather than in combination with Wi-Fi, as it provides everything necessary for an end-to-end solution and is used this way very successfully in more than 140 countries throughout the world. However, Wi-Fi can reach throughput and low latency performance that LoRaWAN is not intended to deliver. This means that in a growing number of situations, the two very different technologies are being used together to produce solutions that neither Wi-Fi nor LoRaWAN could serve alone. This powerful combination therefore opens up an even broader array of application uses.
It is also remarkably easy to integrate the two. Multiple device manufacturers make transceivers and gateways that support both Wi-Fi and LoRaWAN, and Wi-Fi access point adapters are available that plug into LoRaWAN gateways. The latest LoRaWAN/Wi-Fi gateways are smaller than their predecessors, typically about the size of two smartphones stacked together, and their cost is decreasing to price points lower even than standard consumer Wi-Fi access points. Many also include support for Bluetooth, GPS and all of LoRaWAN’s features, including multiple levels of security. Setting up a dual-protocol gateway is a simple process via the gateway’s software or a smartphone app.
The process of moving data generated by LoRaWAN sensors to Wi-Fi is accomplished almost instantaneously and can be tailored to activate on specific conditions. For example, when a camera using LoRaWAN detects motion and video recording begins, transmission can be handed off to Wi-Fi, which has the bandwidth and speed required to send it to the cloud.
Another example is location and tracking, where the LoRaWAN sensor “sniffs” for Wi-Fi access points and transmits the number of satisfactory access points to the LoRaWAN cloud, after which geolocation is achieved through triangulation and precise time-stamping. Even a single IoT device can achieve Wi-Fi-based geolocation accuracy of about 10 meters indoors, depending on the number of available Wi-Fi access points. Vertical elevation positioning is about 5 meters with five strong Wi-Fi signals, and outdoors in urban areas about 20 meters.
Accuracy can also be increased when fine timing measurements (also called round trip time, or RTT) available with the IEEE 802.11mc standard are employed. IEEE 802.11mc is one of the least known recent advances in precise location technologies, as it hasn’t gotten much media attention until recently. It was incorporated in Android P and is expected to become more widely deployed in the coming years. IEEE 802.11mc can increase positioning accuracy to about 1 meter and provide vertical (Z-axis) location information, which has eluded a solution in the past.
Wi-Fi RTT reduces location error to about 1 meter in all three axes, making it possible, for example, for first responders to locate someone using a smartphone to call 911 and be precisely located in an apartment in a multistory building. When RTT-enabled Wi-Fi access points and LoRaWAN are used together, this same precision extends to remote locations as well.
LoRaWAN and Wi-Fi simply play well together, something that cannot be said for other wireless communications technologies, whether short or long range. Cellular networks can accomplish most of what LoRaWAN can, but require much more infrastructure, are more costly to deploy, consume more device battery lifetime, and give you limited control over your IoT communications network. As a result, LoRaWAN has risen to become the most widely deployed LPWAN technology, and thanks to Wi-Fi’s extremely high data rates over short distances, it trumps all other solutions by an order of magnitude. Together, they offer a unique solution.
-Remi Lorrain, LoRaWAN ambassador, Semtech