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Cognitive radio based smart grid communications Chapter 6 229

signal/traffic load level in the CCC may change depending on the type of trans-
ferred data. For instance, one-bit decision from CR devices may be enough for
some CSS algorithms while multiple decision bits may be required for other
algorithms. In addition, insufficient clustering of CR devices for cooperation
may not ensure the desired performance in the CSS. For instance, the sensing
knowledge acquired from the CR devices concentrated in a narrow region may
indicate high similarity because those devices may suffer from the same
destructive effects. In centralized CSS, collaborated CR devices sense the spec-
trum bands and the sensed data are send to the central data center where the
received data are analyzed to decide whether the spectrum is idle, or not. In dis-
tributed CSS, the CR devices change their perceived data between each other
over the CCC, and each CR device creates its own sensing decision by combin-
ing the collected data.

6.5 CR based communication systems in smart grids

The communication infrastructure of SGs can be constituted by using several
communication protocols that may be based on wired and/or wireless commu-
nication technologies. The power line communication (PLC) is a promising
wired communication technology for the SG systems. This technology intends
to efficiently exploit current power lines as a communication environment as
well as their power delivery task. For instance, the PLC systems can ensure high
data transmission rates up to the 200 Mbps over the single-phase networks.
Although this technology is able to provide the advantage of canceling instal-
lation cost because of employing existing power lines, the power lines may lead
to important performance degradation problems due to serving for many years.
In addition, the changing channel impedances and dissimilar noise types of
power lines also cause considerable problems [66–68]. Besides wired technol-
ogies, there exist several popular wireless communication technologies depend-
ing on wireless personal area network (WPAN) called IEEE 802.15.4 standard
and the WRAN called IEEE 802.22 standard [69–75]. Furthermore, the insuf-
ficiencies of the PLC systems that are especially shown at high frequencies may
be eliminated by exploiting wireless communication technologies [76].
The IEEE 2030-2011 standard, which is accepted as a main guideline for the
SG systems, describes communication system requirements of the SG systems.
The SG communication architecture characterized by the standard is illustrated
in Fig. 6.15 where the communication infrastructure is formed according to a
three-section model. The first segment of this definition that covers HAN,
building area network (BAN) and industrial area network (IAN) is established
on the consumer side through special networks. The second part of the defini-
tion that is based on the WAN containing NAN and FAN is constituted on the
distribution side of the SGs. Both FANs and NANs perform monitoring and
controlling processes of AMI, phasor measurement unit (PMU) and remote ter-
minal units. The third one is referred as core network that is located at