Page 124 - From Smart Grid to Internet of Energy

108 From smart grid to internet of energy

(may be also referred as rank value) to preserve its status in the DAG. The rela-
tion of a node with the other nodes in the DAG is given by the index value of a
node. A DAG has a directed graph and tree-like structure, where whole edges
are directional and having no cycles (i.e., closed path). In addition, every DAG
has a root which is basically a GW node in wireless mesh networks (WMNs). In
order to prevent any routing loop, the index value of nodes at any path to a DAG
root should be varied regularly. The DAG is constructed on the basis of control
information announcement whose details are available in [18, 19]. It is impor-
tant to note that many issues need to be investigated in SG applications.
However, one of the most crucial issues is how to customize the RPL to address
particular needs of SG NANs.
The RPL is implemented on AMI system in [19] where authors of the paper
deployed a stationary multi-hop wireless AMI network that contains many SM
nodes and one GW node. For the proper implementation of network, first of all it
is required to provide network information to every node present in the network
which is compulsory to be store and uphold by each node. Later, incoming and
outgoing unicast forwarding rules are defined for all the nodes. These rules are
also considered as data traffic rules. An expected transmission time (ETX)
depending on the DAG scheme is also presented in this study where ETX value
of each connection may vary on the basis of data traffic of communication links.
Novel DAG establishment and maintenance methods were also developed in
this proposal, where ETX variation of a node will broadcast over the whole net-
work by using control messages, and activates the maintenance technique of
whole nodes for adaptation to ETX. In this way, incoming unicast traffic prob-
lems can be resolved by ensuring that E2E transmission has high reliability.
However, to resolve the challenges of routing for outgoing unicast traffic, a
method known as reverse path recording is recommended. Every node can save
the source and last-hop node of inward data transmission via this new method,
without any additional protocol overhead.
A WMN having single GW node may not be appropriate for SG NANs. An
improved RPL solution for the SG NANs is suggested in [18]. Since the network
topology is in the form of multiple trees, every tree belongs individual GW and
functions in its private channel in order to prevent interference with each other.
In these scenarios, SM nodes have to be capable to discover automatic GW and
detect connectivity loss, however, primary RPL does not support this feature.
Two components into the routing tables of every node were included to over-
come this issue. First component is a data record structure where an array is
employed to accumulate channel number and related optimal index value infor-
mation. In the routing process, on the basis of routing messages received, a node
will save and update the record array, and search for the best available channel
for data transmission. The second one is a counter that is responsible to store
number of failures occurred in transmissions. The present connectivity of
channel is missing, if number of failures goes beyond the predefined threshold
value. Hence, a channel scan process should be initiated by the node.