■ FIGURE 4. This graphic shows
the many possible uses of PLC for
M2M applications in the home. It
includes appliance monitoring and
control, security, and connection
back to the electric grid via the
smart meter. (Courtesy Texas
intermediate gateway between the sensor node and the
cellular network. The sensor talks to the gateway via Wi-Fi.
Other sensor nodes may also use the same gateway. The
gateway serves as an aggregation point for a whole
network of sensors and/or actuators for a specific
application. The gateway then is used as the backhaul
connection through a cellular network or an Ethernet link
to the remote collection and control computer. An
example of such a system is one from B&B Electronics
(see Figure 3). The embeddable Wi-Fi module is shown in
the lower right. The Airborne Access Point is shown in two
places and has an Ethernet port and two serial ports. This
system uses the IEEE 802.11b/g standards. These products
are designed primarily for industrial applications but will
no doubt find other M2M applications.
The ZigBee wireless standard is another option for
remote sensor networks. It is even lower in cost than Wi-Fi
and cellular connections, and features even lower power
consumption — something that benefits remote sensors
whose battery life is essential over a long period of time.
ZigBee also has a mesh network mode that allows one
node to talk to any other node either directly or indirectly.
ZigBee is a low power, short range technology limited to
10 meters or so.
If a sensor node is not near enough to the gateway, it
can send its data through closer adjacent nodes that serve
as repeaters. The data may travel through multiple nodes
in the mesh network to get to the collection point. Other
wireless technologies with potential for M2M are Z-Wave
which is popular in home control and Bluetooth that has
both low power and mesh networking capability making it
an option for some applications. Another possibility is
proprietary systems based on ISM (
industrial-scientific-medical) band radios in the 433 and 915 MHz ranges.
Even short range technologies like RFID and NFC
could find a use in some M2M applications. Radio
62 August 2012
frequency identification (RFID) is
the use of passive (no battery
power) tags to locate and track
items to which they are attached.
The transmit/receive range is short
from a few inches to several feet
which limits their use, but they’re a
good fit for applications such as
inventory and shipping control.
(NFC) is that short range
technology using the 13. 56 MHz
band for payments and access. An
NFC powered smartphone can use
While wireless communication technologies dominate
M2M, power line communications (PLC) is another
option. This is the use of the AC power lines for data
transmission. The binary data from a sensor of a control
signal to an actuator is used to modulate a carrier that is
superimposed on the 60 Hz AC power voltage for
While transmission distances are generally limited to
a home or neighborhood, it is a low cost way to transmit
data. In some smart energy systems, a PLC node sends
its data to a nearby collection or aggregation point that
is then connected via cellular backhaul to the utility.
Figure 4 shows the full potential of PLC in a home
THE INTERNET OF THINGS
You may have already heard of this movement which
has the goal of connecting everything to the Internet.
Since we have already networked virtually all the PCs,
laptops, tablets, and cell phones, it’s time to move on to
everything else. Also called the “Internet of Everything,”
this is the use of M2M to provide a way to connect even
the smallest, cheapest, and non-significant devices to the
Internet for potential monitoring or control. It is being
done right now but with low cost wireless and PLC
transceivers with Internet interfaces. Literally anything can
be attached. For example, you could control a specific
light switch in your home from your smartphone. Or, you
could use your iPad or other tablet to monitor a security
camera in your home from anywhere in the world.
There are so many examples of this and so much
potential, it is difficult to cover them all. You can think up