Artificial Cobweb Intelligent Routing Algorithm for Low-Voltage Power Line Communication - Intelligent Computing for Sustainable Energy and Environment - page 367

1) Central node 13 sends reconstruction broadcast to the nodes in its same
subnet.
2) Nodes, which intercept the instructions of routing reconstruction, transmit
the instructions in turns and add their own logical ID in the data packet.
3) Node 11 records the physical strength of reconstruction broadcast signals,
calculate and select the node of max to be a relay node (node 12 in this paper),
send response to node 12. Node 11 establishes communication route to central
node 13 with the node 12 as relay.
4) Node 12 sends information to node 13, node 13 updates the routing table.
5) Node 13 informs the corresponding node to update routing table up layer
by layer until the BS. With this the routing reconstruction process of bad node
after networking is completed. When bad node appeared in the network, it is not
necessary for all nodes to reconstruct route, only the nodes in the same subnet
with bad nodes are involved, so that it highly shorten the route reconstruction
and maintenance time, and improve the eciency of the system.

3.3 Algorithm Timing

The PLC only allows one node to send data at any time, so it is necessary to
present a reasonable timing strategy. Otherwise the channel conflict will seri-
ously affect the performance of system. According to artificial cobweb routing
algorithm (ACRA), a data transmission timing of nodes in subnet is established
to make a comparative simulation with the clustered simple polling (CSP) algo-
rithm mentioned in reference [11]. The interval time of communication between
two meter nodes T WT in ACRA is defined as (1). T P represents the manage
processing delay of one meter unit; T T is the signal transmission time among
nodes; T R indicates the communication redundant time. Generally, the signal
transmission time T T in power line is fast enough to be ignored.
T WT >T P + T T + T R

(1)

According to the protocol and the experimental results, T WT is taken as 150
ms in this paper. Finally the communication effectiveness of cobweb structure
is confirmed from the aspect of data collision and channel utilization percent.
Figure 7(a) is timing of ACRA, horizontal axis is time, single-layer cobweb is
consist of n nodes, node n is the central node, the rest are peripheral nodes, every
node sends data message according to the logical ID from small to large in turns
to central node of its subnet with a interval T WT . After receiving messages from
all nodes, the central node then sends them to the central node or BS. So that
it avoids the channel data collision caused by occupation of channel by several
nodes at the same time. Figure 7(b) is the timing of CSP, it takes 5 nodes for
instance. The node of medium distance will communicate with the BS through
the node of close distance as a relay.
Without constant relay nodes and strict timing, the 5 nodes will find the close
node by sending random messages, so as to result a large amount of collision of
data in the channel. The corresponding simulation result is described in details
in the fourth part of this paper.