[LoRa] LoRaWAN and Wi-Fi: Made for Each Other

[Jesus Cea]

https://www.eetimes.com/lorawan-and-wi-fi-made-for-each-other/

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LoRaWAN and Wi-Fi: Made for Each Other
By Remi Lorrain  12.18.2019 0
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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).
Remi Lorrain

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.
LoraWAN and WiFi complement each other.

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

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-- 
Jesús Cea Avión                         _/_/      _/_/_/        _/_/_/
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"El amor es poner tu felicidad en la felicidad de otro" - Leibniz

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