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Power line communication technologies in smart grids Chapter 4 153

l There are two options for number of preamble symbols, which are 9.5 and
13.5.
l Two different guard interval (GI) may be used in this standard. The first one
is called standard GI with 30 samples that is the same as used in G3-PLC.
The second is optional one with 52 samples, which can be exploited in FCC
and ARIB bandplans.
l A super robust mode is available for the payload where FEC is performed by
using RS code, CC and repetition code. This mode is optional for CENELEC
bands while mandatory for others.

4.4.4.2 MAC layer
Similar to the ITU-T Rec. G.9903 (G3-PLC), the IEEE 1902.1 MAC layer
employs services of IEEE 802.15.4-2006. Both standards use the same defini-
tions for medium access, interframe spacing structure, ARQ procedure, tone
map negotiation and segmentation of frames. The one remarkable difference
among these standards is related to the optional multi-tone mask mode where
it can operate in both beacon-enabled and non-beacon enabled modes [30, 61,
87]. The network model of the standard can be reduced to two devices as,

l A PAN coordinator that is the network coordinator can be taken into account
as a master node.
l An IEEE 1901.2 device that includes an application of IEEE 1901.2-
2013 MAC.
In addition, the network can be established in star, tree or mesh topology. None-
theless, each network should have one IEEE 1901.2 device to serve as the net-
work coordinator. The access to physical medium is realized via CSMA/CA
protocol.

4.5 EMC regulations for PLC systems
The PLC system operates together, not in an isolated environment. Especially,
the power lines are principally constructed to feed electrical loads, devices and
home appliances instead of transmitting PLC signals. Thus, it is evident that
PLC devices should obey regulations that aim to control level of signals con-
nected to the power lines. In addition, PLC systems should comply with radiated
emission limits [28, 88]. Since EMC regulations aim to exist together with other
communication systems, they restrict frequency band and signal levels inserted
to power lines by the PLC systems. This aim can be accomplished by restricting
both radiated and conducted emissions. Radiated emissions occur owing to the
common mode (CM) currents that is also called as antenna currents. Differential
mode currents occur because of the fact that the PLC signals are injected
between two power lines. At the same time, CM currents also emerge owing
to the irregularities of the network [30, 89]. While the CM currents flow in