2 research outputs found
Performance Modeling and Analysis of Wireless Local Area Networks with Bursty Traffic
The explosive increase in the use of mobile digital devices has posed great challenges in the design and implementation of Wireless Local Area Networks (WLANs). Ever-increasing demands for high-speed and ubiquitous digital communication have made WLANs an essential feature of everyday life. With audio and video forming the highest percentage of traffic generated by multimedia applications, a huge demand is placed for high speed WLANs that provide high Quality-of-Service (QoS) and can satisfy end user’s needs at a relatively low cost. Providing video and audio contents to end users at a satisfactory level with various channel quality and current battery capacities requires thorough studies on the properties of such traffic. In this regard, Medium Access Control (MAC) protocol of the 802.11 standard plays a vital role in the management and coordination of shared channel access and data transmission. Therefore, this research focuses on developing new efficient analytical models that evaluate the performance of WLANs and the MAC protocol in the presence of bursty, correlated and heterogeneous multimedia traffic using Batch Markovian Arrival Process (BMAP). BMAP can model the correlation between different packet size distributions and traffic rates while accurately modelling aggregated traffic which often possesses negative statistical properties.
The research starts with developing an accurate traffic generator using BMAP to capture the existing correlations in multimedia traffics. For validation, the developed traffic generator is used as an arrival process to a queueing model and is analyzed based on average queue length and mean waiting time. The performance of BMAP/M/1 queue is studied under various number of states and maximum batch sizes of BMAP. The results clearly indicate that any increase in the number of states of the underlying Markov Chain of BMAP or maximum batch size, lead to higher burstiness and correlation of the arrival process, prompting the speed of the queue towards saturation.
The developed traffic generator is then used to model traffic sources in IEEE 802.11 WLANs, measuring important QoS metrics of throughput, end-to-end delay, frame loss probability and energy consumption. Performance comparisons are conducted on WLANs under the influence of multimedia traffics modelled as BMAP, Markov Modulated Poisson Process and Poisson Process. The results clearly indicate that bursty traffics generated by BMAP demote network performance faster than other traffic sources under moderate to high loads.
The model is also used to study WLANs with unsaturated, heterogeneous and bursty traffic sources. The effects of traffic load and network size on the performance of WLANs are investigated to demonstrate the importance of burstiness and heterogeneity of traffic on accurate evaluation of MAC protocol in wireless multimedia networks.
The results of the thesis highlight the importance of taking into account the true characteristics of multimedia traffics for accurate evaluation of the MAC protocol in the design and analysis of wireless multimedia networks and technologies
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Analysis and improvement of medium access control protocols in wireless networks. Performance modelling and Quality-of-Service enhancement of IEEE 802.11e MAC in wireless local area networks under heterogeneous multimedia traffic.
In order to efficiently utilize the scarce wireless resource as well as keep up
with the ever-increasing demand for Quality-of-Service (QoS) of multimedia
applications, wireless networks are undergoing rapid development and dramatic
changes in the underlying technologies and protocols. The Medium Access Control
(MAC) protocol, which coordinates the channel access and data transmission of
wireless stations, plays a pivotal role in wireless networks.
Performance modelling and analysis has been and continues to be of great
theoretical and practical importance in the design and development of wireless
networks. This research is devoted to developing efficient and cost-effective
analytical tools for the performance analysis and enhancement of MAC protocols in
Wireless Local Area Networks (WLANs) under heterogeneous multimedia traffic.
To support the MAC-layer QoS in WLANs, the IEEE 802.11e Enhanced Distributed
Channel Access (EDCA) protocol has proposed three QoS differentiation schemes
in terms of Arbitrary Inter-Frame Space (AIFS), Contention Window (CW), and
Transmission Opportunity (TXOP). This research starts with the development of
new analytical models for the TXOP scheme specified in the EDCA protocol under
Poisson traffic. A dynamic TXOP scheme is then proposed to adjust the TXOP
limits according to the status of the transmission queue. Theoretical analysis and
simulation experiments show that the proposed dynamic scheme largely improves
the performance of TXOP. To evaluate the TXOP scheme in the presence of
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heterogeneous traffic, a versatile analytical model is developed to capture the traffic
heterogeneity and model the features of burst transmission. The performance results
highlight the importance of taking into account the heterogeneous traffic for the
accurate evaluation of the TXOP scheme in wireless multimedia networks.
To obtain a thorough and deep understanding of the performance attributes of
the EDCA protocol, a comprehensive analytical model is then proposed to
accommodate the integration of the three QoS schemes of EDCA in terms of AIFS,
CW, and TXOP under Poisson traffic. The performance results show that the TXOP
scheme can not only support service differentiation but also improve the network
performance, whereas the AIFS and CW schemes provide QoS differentiation only.
Moreover, the results demonstrate that the MAC buffer size has considerable impact
on the QoS performance of EDCA under Poisson traffic. To investigate the
performance of EDCA in wireless multimedia networks, an analytical model is
further developed for EDCA under heterogeneous traffic. The performance results
demonstrate the significant effects of heterogeneous traffic on the total delay and
frame losses of EDCA with different buffer sizes. Finally, an efficient admission
control scheme is presented for the IEEE 802.11e WLANs based on analytical
modelling and a game-theoretical approach. The admission control scheme can
maintain the system operation at an optimal point where the utility of the Access
Point (AP) is maximized with the QoS constraints of various users