Study on Throughput of Network with Selfish Nodes Based on IEEE 802.15.4 - Advanced Research on Computer Education, Simulation and Modeling - page 414

In this paper, the selfish nodes minimize their BE once they sense the channel state
is busy while the common nodes increase their BE respect the backoff mechanism.
Therefore, the selfish nodes dramatically increase the probability to obtain the chan-
nel resource.
Analyzing the result of simulation, we get the throughput of each node, as illus-
trated in Fig. 3.
In Fig. 3, the throughput of each node is roughly the same when the nodes are all
common nodes. But when the network exist one selfish node, like the No.11 node, the
majority of the channel resources are occupied by the selfish node.

2.2 Different Network Size Simulation

For the further study of the impact of selfish nodes on the network, we change the
network size, and analyze the throughput and the packet loss rate. The number of
nodes in the network is increasing from 3 to 20. Fig. 4 illustrates the throughput of
selfish node and common nodes while increasing the network size. Fig. 5 respectively
illustrates the throughput of network exists selfish nodes and does not exist selfish
node.

4

Throughput of Nodes

x 10

14

Common-node
S elfish-node

13

12

11

10

9

8

7

6

5

2 4 6 8 10 12 14 16 18 20

Network size(node-number)

Fig. 4. Throughput of selfish node and common node

As shown in Fig. 4, when only 3 nodes exist in the network, this is, one selfish
source node, one common source node and one destination node, the selfish node
receives a great number of data packets, nearly occupy all the network resources,
while the common node only receives one data packet. With the increasing of the
common nodes in the network, the throughput of common nodes shows an upward
trend. When the number of the common nodes amounts to 19, the throughput of them
amounts to 2000 bytes, however, the throughput of the selfish node is 8,000 bytes.
With continuing increase network size, the throughput of the common source nodes
changes little. Therefore, when a selfish node exists in the network, with the network
size increasing, the throughputs of the common nodes increase but far from that of the
selfish node. The selfish node occupies the majority of the channel resources.