| Summary: | The performance of the IEEE Project 802.11 Wireless Media Access Control (WMAC)
protocols for wireless local area networks (WLANs) is studied. In particular, the asynchronous
data service in the contention period of the protocol is simulated in both adhoc and infrastructure
network topologies. Ptolemy, a powerful mixed-mode and object-oriented simulator, is used as the
engine for all discrete-event computer simulations. The sensitivity of network geometry, traffic
flow, queueing size, channel models, hardware, and backoff parameters on performance is
extensively studied. Moreover, the "hidden terminal problem" is also examined. It turns out that
the connectivity and the hidden terminal parameter, P[sub h], can be used to predict the performance of
the system with different geometries. In the worst case considered in this thesis where both the
connectivity and P[sub h] are high, the throughput performance for the Carrier Sensing Multiple Access
with Collision Avoidance (CSMA/CA) protocol using RTS/CTS and ACK frames drops down to
16% of the data rate. However, the throughput is kept steady even when the system load is twice
the data rate.
Various other parameters used in the simulation can also affect the performance to some
extent. Near optimal values for the queueing size, the receiver sensitivity, the carrier sense threshold,
the contention window size, and the maximum retransmission value can be found through
computer simulations. On the whole, it appears that the performance of the CSMA/CA basic
access protocol in the 802.11 standard is acceptable even under adverse channel conditions.
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