Page 164 - From Smart Grid to Internet of Energy

Power line communication technologies in smart grids Chapter 4 141

FIG. 4.5 Reference model of ITU-T Rec. G.9902 (Gh.nem). (From Narrowband orthogonal fre-
quency division multiplexing power line communication transceivers for ITU-T G.hnem networks,
ITU-T Rec. G.9902, October 2012. [Online] Available: http://www.itu.int/rec/T-REC-G.9902
(Fig. 5-12), with permission.)

The A reference point is a transition point among network layer and DLL
layer, and its structure may change according to the selected network layer such
as IPv6, Ethernet, and so on. Application protocol convergence (APC), which is
a sublayer, is responsible to provide an interface for network layer. The logical
link control (LLC) sublayer manages all connections with other nodes by taking
into account the quality of service (QoS) requirements of each connection. The
last sublayer of DLL is the MAC that organizes the access to the medium by
using CSMA/CA algorithm. The PMI reference point is a transition stage
between DLL and PHY layer. The PHY layer contains three sublayers called
physical coding sublayer (PCS), physical medium attachment sublayer
(PMA) and physical medium dependent sublayer (PMD). The PCS ensures
bit-rate adaptation among PHY and MAC layers in addition to controlling
and managing several processes in the PHY layer. The PMA sublayer maintains
forward error correction (FEC) encoding and interleaving processes in the PHY
layer. The last sublayer performs modulation and demodulation processes in
this layer.
On the other hand, this standard also describes a management interface
employed by upper layers to manage transactions of PHY and DLL layers.
The ITU-T Rec. G.9902 (G.hnem) network topology is established in a logical
domain structure in which each domain has specific sets of nodes related to the