  This paper presents the design procedure of the NS-3 script for WLAN that is
organized according to the hierarchical manner of TCP/IP model. We configure
all layers by using NS-3 model objects and set and modify the values used by
objects to investigate the effects of MAC parameters (access mechanism, CWmin,
CWmax and retry limit) on the performance metrics viz. packet delivery ratio,
packet lost ratio, aggregated throughput, and average delay. The simulation
results show that RTS/CTS access mechanism outperforms basic access mechanism
in saturated state, whereas the MAC parameters have no significant impact on
network performance in non-saturated state. A higher value of CWmin improves
the aggregated throughput in expense of average delay. The tradeoff
relationships among the performance metrics are also observed in results for
the optimal values of MAC parameters. Our design procedure represents a good
guideline for new NS-3 users to design and modify script and results greatly
benefit the network design and management.
