
H. TANG ET AL.
Copyright © 2013 SciRes. CN
The worst grey relevance coefficient as show in Equa- tion(5):
min min
min min
min min() max max
() .
() max max
i ii
ik ik
ii ii
ik
kXkkkXk
kkXkkkXk
−|Ζ()− ()|+ρ|Ζ()− ()|
γ=|Ζ()−()|+ρ|Ζ()−()|
(5)
Here,
is the distinguishing coefficient and its gen-
eral value is 0.5.
7) Calculate the grey relevance degree:
We use
to represent the optimal grey relevance
degree, use
to represent the worst grey relevance
degree. Generally grey relevance degree is to take the
mean of grey relevance coefficient, but here we take into
account the actual impact of each factor of the selected
route is not the same degree of influence, so we use
weighting to calculate grey relevance degree. The o ptim-
al grey relevance degree as shown in Equation (6):
(6)
The worst grey relevance degree as show in Equation
(7):
(7)
Here,
is the weight of each impact factor, and
.
8) Calculate the grey relevance degree of each RREQ
message and select a RREQ message with the highest
grey relevance degree:
We use
to represent the grey relevance degree of
each RREQ message, the grey relevance degree as show
in Equati o n ( 8):
(8)
3.2. The Implementation of GRA-AODV
Routing Protocol
Comparing with the traditional AODV protocol, the GRA-
AODV routing protocol has been improved mainly in the
routing building phase the route maintenance phase is the
same with the traditional AODV routing protocol. The
main step of routing building phase of GRA-AODV
routin g protocol as f ol lows:
1) Studies have shown that synthesizing the informa-
tion of physical layer, data link layer and routing layer to
design routing protocol can greatly improve QoS of net-
work [8]. So we add the information which consists of
the remaining energy of node and the remaining queue
length of nodes into the RREQ packet header, and use th e
hop count which is carried on the RREQ packet header as
the information of routing layer.
2) Due to the performance of whole link depends on
the worst state node in the link, we collect the minimum
remaining energy and the m inim um remaining queue length
of nodes to reflect the information of whole link.
3) When the source nodes want to send data to the
destination node, the source nodes check whether its own
routing table has the path to the destination node at first.
If there is a path to destination node, then send data pack-
ets by this path; if there is not a path to the destination
node, then broadcasts RREQ route request message to its
neighbor node to launch a route discovery process.
4) When the intermediate node received a RREQ route
request message, we should first check the destination
node address of RREQ packet header. If the destination
node is itself, then follow the step (5) to handle. If the
destination node is not itself , we compare the destination
sequence number, the remaining energy and the remain-
ing queue length in its own route table to those of RREQ
packet header, updating the destination sequence number
in the RREQ packet header as the maximum one, and
updating the remaining energy and the remaining queue
length of node in the RREQ packet header as the mini-
mum one, and the hop-count plus one. The difference
with the traditional AODV routing protocol is that we
don’t use the path to the destination which may be caught
in the route table of intermediate node, which aim to en-
sure that the RREQ message received by target node can
more accurately reflect the information of the whole link.
5) When the destination node received the first RREQ
message, then we start a timer, this is done to receive
more RREQ message so that we can make use of gray
relevance algorithm to choose the best one. When the
timer expired, we extract the information which consist
of the remaining energy, the remaining queue length and
the hop-count from the RREQ packet header as the im-
pact factors, we take the remaining energy of node and
the remaining queue length of nodes as benefit type to
handle, and take the hop-count as cost type to handle,
then we calculate the gr ey relevance degree of each RREQ
message.
6) The destination node only to send the RREP mes-
sage to source node according to the RREQ message with
the maximum grey relevance degree. Finally the source
node sends da te to the de s t inati on by this path.
4. Simulation
In this paper, we take average end to end delay, packet