We present a Markov chain analysis for studying the performance of wireless ad
hoc networks. The models presented in this dissertation support an arbitrary backoff
strategy. We found that the most important parameter affecting the performance of
binary exponential backoff is the initial backoff window size. Our experimental results
show that the probability of collision can be reduced when the initial backoff window
size equals the number of terminals. Thus, the throughput of the system increases
and, at the same time, the delay to transmit the frame is reduced.
In our second contribution, we present a new analytical model of a Medium
Access Control (MAC) layer for wireless ad hoc networks that takes into account
frame retry limits for a four-way handshaking mechanism. This model offers flexibility
to address some design issues such as the effects of traffic parameters as well as
possible improvements for wireless ad hoc networks. It effectively captures important
network performance characteristics such as throughput, channel utilization, delay,
and average energy. Under this analytical framework, we evaluate the effect of the
Request-to-Send (RTS) state on unsuccessful transmission probability and its effect on
performance particularly when the hidden terminal problem is dominant, the traffic is
heavy, or the data frame length is very large. By using our proposed model, we show
that the probability of collision can be reduced when using a Request-to-Send/Clear-
to-Send (RTS/CTS) mechanism. Thus, the throughput increases and, at the same
time, the delay and the average energy to transmit the frame decrease.
In our third contribution, we present a new analytical model of a MAC layer for
wireless ad hoc networks that takes into account channel bit errors and frame retry
limits for a two-way handshaking mechanism. This model offers flexibility to address
design issues such as the effects of traffic parameters and possible improvements for
wireless ad hoc networks. We illustrate that an important parameter affecting the
performance of binary exponential backoff is the initial backoff window size. We show
that for a low bit error rate (BER) the throughput increases and, at the same time,
the delay and the average energy to transmit the frame decrease. Results show also
that the negative acknowledgment-based (NAK-based) model proves more useful for
a high BER.
In our fourth contribution, we present a new analytical model of a MAC layer
for wireless ad hoc networks that takes into account Quality of Service (QoS) of
the MAC layer for a two-way handshaking mechanism. The model includes a high
priority traffic class (class 1) and a low priority traffic class (class 2). Extension of
the model to more QoS levels is easily accomplished. We illustrate an important
parameter affecting the performance of an Arbitration InterFrame Space (AIFS) and
small backoff window size limits. They cause the frame to start contending the channel
earlier and to complete the backoff sooner. As a result, the probability of sending the
frame increases. Under this analytical framework, we evaluate the effect of QoS on
successful transmission probability and its effect on performance, particularly when
high priority traffic is dominant. / Graduate
| Identifer | oai:union.ndltd.org:uvic.ca/oai:dspace.library.uvic.ca:1828/3632 |
| Date | 19 October 2011 |
| Creators | Khayyat, Khalid M. Jamil |
| Contributors | Gebali, Fayez |
| Source Sets | University of Victoria |
| Language | English, English |
| Detected Language | English |
| Type | Thesis |
| Rights | Available to the World Wide Web |
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