An Intelligent Opportunistic Routing Algorithm for Wireless Sensor Networks and Its Application Towards e-Healthcare

. 2020 Jul 13;20(14):3887. doi: 10.3390/s20143887

Algorithm 2. Forwarder_Node_Selection (S = Source, D = Destination)

//when any node S wants to send a packet toward D and it has already constructed a forwarder list, it will follow this algorithm.

Notations

FL(S):	Forwarder List of source node S
Ri:	ith node in the forwarder list
PRR:	Packet Reception Ratio)
RE:	Residual Energy
D:	Distance
P:	Probability
ArrProb[Ri]:	Array to store probability of a given node
Pmax:	Maximum probability
D:	Destination/Target

Input

R: R is set of nodes in the forwarder list (FL) i.e., R = {R1, R2, …, Rn}

Process
START

Let R1, R2, …, Rn are the nodes in the FL of source node S. Each node Ri∈ FL(S) where i = 1, 2, …, n
Declare three float variables X₁, X₂, and X₃ to represent the properties of Ri, i.e., PRR (Packet Reception Ratio), RE (Residual Energy), and D (distance), respectively.
For each node Ri∈ FL(S) repeat

Compute P(Ri|S)//Probability of selection of Ri given S, i.e.,

P_k = P(R_i|S) for i = 1, 2 …, n and Assign k←i
Compute the probability of P(R_i|S) by computing the probability of each parameter separately, given S.
$P_{k} = P (R i | S) = P (R i_{X 1} | S) * P (R i_{X 2} | S) * P (R i_{X 3} | S)$
where,
$P (R i_{X 1} | S) = \frac{P (S | R i_{X 1}) * P (R i_{X 1})}{P (S)}$

$P (R i_{X 2} | S) = \frac{P (S | R i_{X 2}) * P (R i_{X 2})}{P (S)}$

$P (R i_{X 3} | S) = \frac{P (S | R i_{X 3}) * P (R i_{X 3})}{P (S)}$
Make an unsorted array of probability values of n nodes, i.e., R1, R2, …, Rn from step 6.

For i = 1 to n and k = i, ArrProb[Ri]←P_k//To find the node with maximum probability.
Select the first node of the array ArrProb[0] as the node with maximum value Pmax i.e., Pmax←ArrProb[0]
Go through the rest of the elements of the array, i.e., from the 2nd element to the last (n − 1)

element, for i = 1 to n − 1.
For i = 1 to n − 1, if any value in the array ArrProb[i] is found to be greater than the current value Pmax. i.e.,

if ArrProb[i] > Pmax then, Pmax← ArrProb[i]
When the end of the array is reached, then the current value of the Pmax is the greatest value in the array, Pmax←ArrProb[i].
The node Ri with Pmax value is selected as a relay node from the forwarder list, as

the node with the highest probability. The node with the next highest probability acts as a relay node in case the first selected relay node fails to broadcast.
Broadcast transmission of the data packet as {Ri, coordinates, data}
Destination node D is reached, if Yes, go to step 15. Else, apply Algorithm 1 on Ri

S←Ri and go to step 2.
END

Output: A potential forwarder node is selected from the list of forwarder nodes.