Gateway IoT Nodo Nema Dual Band Nodo Zhaga Dual Band
Public lighting remote
control: flexibility
as a key element
Point to point remote control in public lighting
brings several benefits in terms of management
and energy saving, as well as becoming an
infrastructure that enables Smart City applications.
Considering that a system is typically going to
work for more than 10 years, the choice of the
solution to implement must be based not only on
current evaluations but also, and particularly, on
future developments: first of all, of Smart City
services that can be added and more importantly
of the evolution of remote control systems and
communication protocols, as well as of
environmental issues.
The choice of the network topology
In a “mesh” network, all nodes of the network
communicate with each other and cooperate in
order to convey the information to any point of
the network itself, offsetting the typically limited
span of the radio range (about 100/200 meters). In
this case, the tighter the mesh is the better the
communication works, because the network can
convey much more information at the same time,
without noise and interferences. This topology is
ideal for more homogeneously distributed
coverage (e.g. streetlights) and “peer to peer”
communication, i.e. communication between the
nodes of the network at local level (e.g. dynamic
lighting).
In a “star” network, each node of the network
communicates with a central point with a direct
radio connection, using low frequencies and
higher transmission power to connect with the
center of the star, which is typically distant
hundreds meters (or even kilometers) from each
node. In order to have radio visibility with all the
nodes, the “star center” must be placed in high
positions, often beyond the installation area of the
system. This topology is more suited when the
nodes are less frequent and more distant from the
center. This topology allows for a greater
extension of the network, but the distance
between the nodes and the center is more subject
to interferences and the node could more easily
remain isolated.
The choice of the radio frequency
Taking into consideration only free use bands, the
main decision is whether to adopt a system
working on 2,4 GHz or 868 MHz frequency
(others less used are 443 MHz and 169 MHz).
For a proper choice, the environmental setting
where the solution will be implemented must be
considered, bearing in mind that free bands are
going to be shared with thousands of other
devices and services. Therefore, there is the
possibility that some of these users are not fully
respectful of the regulatory limitations (e.g. the
“duty cycle” on the 868 MHz channel limited to
the 2.8% of the time), with an impact on the
actual functioning.
868 MHz band allows long distance
communications, using higher transmission
powers compared to 2,4 GHz mesh network.
However, it is much more likely to be interfered
because it has to share the “radio space” with a
much higher number of potential competitors.
Additionally, if the IEEE 802.15.4 standard is
applied, only one 868,3 MHz radio channel can be
used, with the serious risk of “clogging”.
Also on the 2.4 GHz frequency there may be
interferences due to the presence of strong signals,
but, in any case, the 16 available channels will
allow to find one that is free from such
interferences. On the other hand, WiFi or
Bluetooth signals are less or not impacting at all
and they can coexist with 802.15.4.
Conclusions
To sum up, the ideal solution would be to use the
best of each architecture and technology,
adjusting the functioning to follow technological
and regulatory evolutions or future problems not
foreseeable during the design phase.
This is why Algorab has developed innovative
Double Band nodes, both with a 2,4 GHz radio, to
accomplish the short range, mesh and peer to
peer functionalities, and a 868 MHz radio, which
supports different communication standards,
among which 802.15.4 and LoRa WAN. The
nodes are able to implement the Bluetooth
standard as well, in order to have a connection
with the world of smart phones and other
Bluetooth devices.
This flexibility allows to remotely manage a
network simultaneously with mesh and star
topology using the two frequencies according to
the needs, while the update of the firmware OTA
(On The Air) allows to redefine via software all
the features of the devices. Therefore, this ensures
the compliance to new communication standards
or new required functionalities over time.
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