Page 210 - From Smart Grid to Internet of Energy

186 From smart grid to internet of energy

and low-energy consumption features. Especially, the LECIM networks aim to
serve for outdoor applications containing thousands of nodes with low data rate.
Some application areas of the LECIM networks are related to SG, smart meter-
ing, smart city, IoT applications, transportation, industrial monitoring, agricul-
ture, and so on [22]. The major properties of the LECIM networks are minimum
infrastructure requirement with star network topology, wide coverage areas
with high receiver sensitivity and low power consumption [21].
In order to support LECIM applications, there exist two different PHY layer
specifications [23–25]. While one of them is based on frequency shift keying
(FSK) modulation, the other is based on the DSSS method. The DSSS based
PHY layer of the IEEE 802.15.4k defined for a star topology can reach to
15
148 dBm receiver sensitivity by employing 32,768 (2 ) spreading factor.
Thus, the coverage area of the LECIM may be widen to tens of kilometers in
rural areas and several kilometers in urban areas. The data rate of DSSS based
LECIM networks may change according to utilized frequency band and region.
There are different frequency bands for the LECIM networks. For instance, 400
and 917 MHz frequencies are used in South Korea, 470 and 780 MHz frequency
bands are employed in China, 868 MHz is exploited in Europe, 902 MHz is uti-
lized in North America, 920 MHz is used in Japan and 2.4 GHz ISM band is
available all over the world. On the other hand, the FSK based PHY layer of
LECIM systems does not aim to present a multi-rate PHY [25]. This type of
the PHY layer can operate in the frequencies of 863, 915, 920, and
2450 MHz by taking into account different mapping and channel parameters.

5.3.4 ZigBee

There exist new wireless technologies that have been developed based on the
IEEE 802.15.4 standard. As stated earlier, the standard merely defines PHY
and MAC layer specifications whereas the technologies such as ZigBee [26],
WirelessHART [27], ISA100.11a [28], 6LoWPAN [29] and 6TiSCH [30] iden-
tify the upper layers separately. The ZigBee Alliance has developed ZigBee
technology as an extensive wireless protocol for applications with low-power
consumption. This technology can support control and monitoring applications
with low cost, and ZigBee transceivers can be simply embedded in many
devices. In addition, the ZigBee systems can be operated via small batteries
over several years due to low power consumption feature of the technology.
Therefore, the use of this technology prevents the need for frequent replacement
of device batteries. The ZigBee Alliance has identified network layer and appli-
cation layer above the IEEE 802.15.4 MAC layer. The network layer of ZigBee
handles the routing processes whereas the application layer accomplishes suit-
able frameworks for several application types. The technology can operate on
either 2.4 GHz or 868/915 MHz unlicensed ISM bands to empower network
topologies based on the star, mesh, or cluster tree schemes in the WSNs. There
exist 16 channels in the 2.4 GHz frequency band, and each of them is composed