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Subject: search.filters.subject.IEEE 802.11 (Standard)

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    Performance improvements to the 802.11 wireless network medium access control sub-layer : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Computer Systems Engineering at Massey University
    (Massey University, 2005) Morrison, Michael Philip
    This thesis presents the outcome into the research and development of improvements to the 802.11 wireless networking medium access control (MAC) sublayer. The main products of the research are three types of improvement that increase the efficiency and throughput of the 802.11 protocol. Beginning with an overview of the original 802.11 physical layer and MAC sub-layer standard, the introductory chapters then cover the many supplements to the original standard (including a brief on the future 802.11n supplement). The current state of the 802.11 MAC sub-layer is presented along with an assessment of the realistic performance available from 802.11. Lastly, the motivations for improving the MAC sub-layer are explained along with a summary of existing research into this area. The main improvement presented within the thesis is that of packet aggregation. The operation of aggregation is explained in detail, along with the reasons for the significant available throughput increase to 802.11 from aggregation. Aggregation is then developed to produce even higher throughput, and to be a more robust mechanism. Additionally, aggregation is formally described in the form of an update to the existing 802.11 standard. Following this, two more improvements are shown that can be used either with or without the aggregation mechanism. Stored frame headers are designed to reduce repetition of control data, and combined acknowledgements are an expansion of the block acknowledgement system introduced in the 802.11e supplement. This is followed by a description of the simulation environment used to test the three improvements presented, such as the settings used and metrics created. The results of the simulations of the improvements are presented along with the discussion. The developments to the basic improvements are also simulated and discussed in the same way. Finally, conclusions about the improvements detailed and the results shown in the simulations are drawn. Also at the end of the thesis, the possible future direction of research into the improvements is given, as well as the aspects and issues of implementing aggregation on a personal computer based platform.
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    Performance study of IEEE 802.11p for vehicle to vehicle communications using OPNET : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Telecommunications and Network at Massey University, Auckland, New Zealand
    (Massey University, 2011) Sun, Ning
    IEEE 802.11p is the recently finalised protocol located at the bottom of the Dedicated Short Range Communication (DSRC) protocol suite, which supports Intelligent Transportation System (ITS) applications for both road safety and added value communication purposes. It has evolved from widely applied Wireless Local Area Network (WLAN) standards and it cooperates with peculiar higher layer protocols in order to carry out inter-vehicle communication. In this thesis, we focus on the performance study of road safety communication as being the vital application in ITS, which is very necessary not only because IEEE 802.11p is a relatively new protocol but also because it heavily relies on broadcast mode, thus distinguishing itself from other 802.11 counterparts. With the aid of OPNET, a powerful commercial simulator, different scenarios have been deployed in which one or more variable factors are involved, such as vehicle number, data packet size, communication distance, vehicle fleet topology, etc., in order to find out their impacts on DSCR and characteristics of 802.11p. After analysing results data collected from hundreds of simulations, we found out that 802.11p represented a desirable performance in terms of latency and priority-oriented services throughout our simulation scenarios. However, packet collision caused by either media contention or hidden nodes turned out to be a relatively serious issue of vehicle communication and 802.11p seems in shortage of an effective mechanism to deal with it. What we can only hope is that under practical application, the media should always be lightly occupied and that there are few ACs with high priorities trying to contend resources simultaneously at any given time. Meanwhile, our analyses indicate that current 802.11p protocol might still need further modifications in order to address its inherent issues and enhance the communication performance.
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    Performance evaluation of multihop wireless network : a thesis presented in fulfillment of the requirements for Master of Engineering degree in Electronics and Communications Engineering, School of Engineering and Advanced Technology, Massey University at Albany, New Zealand
    (Massey University, 2010) Liang, Shuai
    In recent years, there has been an upsurge of interest in wireless broadband access networks in both industry and academia. This study aims at evaluating the performance of wireless access networks implemented in the multihop mesh architecture based on IEEE802.11 standards. An implementation model is defined with the objectives to assess the impact of the variation of several network parameters including the number of mesh access points (MAPs) and stations (STAs), supported profiles, etc. A detailed analysis of the results gathered from 168 simulation runs in OPNET Modeler reveals that the number of MAPs in each extended service set (ESS) could be configured up to 4, the number of STAs associated to each MAP could be up to 8. On the other hand, the EDCA mechanism for QoS support from IEEE802.11e has been considered in the evaluation on both STAs and MAPs. The results show that enabling EDCA mechanism improves the global multihop network performance significantly in the scenarios with more streaming service (more bandwidth demanding) and more real-time applications (more delay stringent and more uplink bandwidth required.