September 2016
30
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nternet
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of
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hings
LoRA wireless networking standard
opens up the smart city
By Simon Duggleby,
RS Components
This article describes the advantages
of the long range LoRa network for
creating IoT applications, not only in
cities but also spreading into the rural
environment.
The Internet of Things (IoT) is a revolution
in the way technology enables countless dif-
ferent systems to work together. It uses the
free flow of data to democratise technology
and let new types of business evolve and dis-
rupt traditional suppliers by reducing costs
and improving service. Like the IoT that it
serves, the LoRa wireless networking stan-
dard is showing that it can harness the same
driving forces and help unleash greater tech-
nological creativity.
Rather than wait for telecommunications
companies to build an IoT network, The
Things Network encouraged organisations
and inhabitants spread around Amsterdam to
create their own in the space of just six weeks
using the LoRa technology. Thanks to its long
range, the group was able to cover much of
the city with just ten gateway routers. Now
the group has turned its attention to other cit-
ies around the world, helping them to build a
wireless infrastructure for the IoT that will be
free of the subscription charges used by oper-
ators for conventional networks based on cel-
lular radio.
The LoRa protocol was originally developed
by the integrated-circuit (IC) supplier Sem-
tech to operate on unlicensed RF bands such
as the widely supported 868 MHz band in
Europe. To help spread use of the technology,
Semtech has licensed the technology to IC
manufacturers Microchip and STMicroelec-
tronics. The protocol uses a spread-spectrum
modulation scheme that ensures commu-
nications between gateways and devices do
not interfere with each other. Spread-spec-
trum coding creates a set of virtual channels
that increase the communications capacity
of each gateway. The possible and probable
emergence of multiple network operators
is not an issue for LoRa thanks to its use of
spread-spectrum to separate not just individ-
ual packets but communications to and from
different gateways within the same area.
The coding scheme lets devices choose the
most appropriate data rate for them without
affecting devices using other virtual channels.
This helps optimise not just network capacity
but maximises the battery life of sensor-node
devices. The data rate of a LoRa link can range
from 0.3kbit/s to 50kbit/s using a protocol
that dynamically adapts the transmission rate.
Devices can sit at distances of at least 15km
from a gateway for line-of-sight communica-
tions or up to 5km where line-of-sight is not
available, such as in dense urban environments.
Several layers of encryption are available to
protect data and ensure that messages to and
from critical infrastructure can be transmitted
securely across open, multi-tenant networks.
Different key pairs operate at the network
level, the application and device level, to allow
security needs to be fine-tuned. In contrast to
cellular technology where the operator must
carefully manage cell overlap, with LoRa a
message transmitted by an end device can be
received by one or more gateways. Every gate-
way that receives the message will forward it to
the network – servers deal with any duplica-
tion and ensure that replies are delivered to the
target application in the cloud. Servers in the
cloud can use not just point-to-point commu-
nication to talk to end devices but can also take
advantage of multicast packets to send com-
mands to groups of devices efficiently, allowing
for a wide range of application use cases.
One of the first use cases developed for the
Amsterdam network was a service to prevent
boats sinking in one of the many canals of the
city. The core of the idea is a water detector
installed on the floor of the boat. If the boat
starts to fill with water, it can send a message
to a server that then alerts the owner by a text
message to their phone. Replying “clear my
boat” would then send a service to check and
repair the boat before the water level causes it
to sink under the surface.
The severe flooding that Calderdale — an area
in the North of England — suffered in recent
years, provided the motivation for setting up
a Things Network community to build a LoRa
