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148 From smart grid to internet of energy

FIG. 4.9 Reference protocol layer model for ITU-T Rec. G.9904. (From Narrowband orthogonal
frequency division multiplexing power line communication transceivers for PRIME networks, ITU-T
Rec. G.9904, October 2012. [Online] Available: http://www.itu.int/rec/T-REC-G.9904 (Fig. 4-1),
with permission.)

The reference model of PRIME standard is depicted in Fig. 4.9. The conver-
gence layer (CL) manages classifying the traffic that is associated with the
appropriate MAC connection. In addition, this layer also exploits the mapping
of all traffic to be covered by MAC service data units (MSDUs). Several Service
Specific Convergence Sublayers (SSCSs) are created to host several types of
traffic in the MSDUs. The MAC layer ensures important transactions such as
fundamental MAC operations, connection construction and maintenance, band-
width allocation and topology resolution. On the other hand, the PHY layer
sends and receives the MPDUs among neighbor nodes by employing OFDM.
Typically, a PRIME system consists of several subnetworks where each sub-
network is characterized in the scope of a transformer station. A subnetwork can
be modeled as a tree structure that contains two kinds of nodes called “base
node” and “service nodes”. The base node is also called as “master node” that
administers resources and connections of subnetworks through beacon signal
transmitted periodically. In addition, the base node has a charge of PLC channel
access, and each network can only contain one base node. While the base nodes
are considered as the root of tree structure, the service nodes are considered as
leaves or branch points of the tree structure. The service nodes are firstly in dis-
connected mode and should perform a registration process to be a part of the
network. They take over two duties. One of them is to keep connectivity to
the other nodes in the network while the second is the switching the data to
expand connectivity.

4.4.3.1 PHY layer
The PHY layer of this standard is based on the OFDM method and serves in
CENELEC-A band covered between 3 and 95 kHz. A typical block diagram
of the PHY layer transmitter is illustrated in Fig. 4.10. The existing spectrum