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Analysis and Performance Enhancement of MAC Layer Protocols in Vehicular Ad Hoc Networks

Ghafourian Ghahramani, Amir Ali | 2017

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  1. Type of Document: Ph.D. Dissertation
  2. Language: English
  3. Document No: 49736 (52)
  4. University: Sharif University of Technology, International Campus, Kish Island
  5. Department: Science and Engineering
  6. Advisor(s): Afshin Hemmatyar, Ali Mohammad
  7. Abstract:
  8. The Intelligent Transportation Systems (ITS) are aimed to provide innovative services to improve safety of the traffic and make the use of the transport networks more coordinated. Such services are implemented by establishing wireless communications among the vehicles. The resulting mobile ad hoc network formed among the moving vehicles is called the Vehicular Ad Hoc Network (VANET). The IEEE 802.11p has been emerged as the first standardized contention-based MAC protocol for VANETs. The overall performance of the contention-based MAC protocols is directly dependent on the number of the contending nodes . To analyze the performance of the 802.11p protocol, most of the existing approaches consider the number of the contending vehicles as a fixed predefined number for each traffic condition. This approach results in an average-based performance analysis for this protocol, that is the average value of important performance metrics are analyzed for different vehicular traffic conditions while the deviations of the performance metrics from their average values are neglected. On the other hand, in VANETs, the number of contending vehicles varies quite often in each traffic condition, thus, it can be regarded as a random variable being described by stochastic processes. In this thesis, we propose two methods to approximate such stochastic processes. As the first method, we analyzed the distribution of the inter-vehicle spacing in different vehicular traffic and we applied the renewal theory to obtain the related counting processes. In the second method, we considered the communication graph formed among vehicles in vehicle- to-vehicle (V2V) communications and, by applying the network science methodologies, we proposed a network model to analyze its unique structural properties. We utilized the structural properties of the communication graph in VANETs to derive the probability distribution of the number of contending vehicles. Then, these two methods are combined with a recently proposed Semi-Markov Process (SMP) model resulting in a hybrid analytical framework. This hybrid analytical frame- work is used to evaluate the broadcasting mode of the 802.11p protocol in terms of the important performance metrics like the Packet Delivery Ratio (PDR), Packet Reception Ratio (PRR), and the transmission delay quantitatively, where the boundary levels (i.e., the lower, dominant and upper levels) of these important performance metrics, the fraction of vehicles that may reach to such boundary levels, and the degree of deviation of important performance metrics from their average values are analyzed. Based on the insights gained from such analyses, we proposed an enhancement in the 802.11p protocol that combines the CSMA/CA and OFDMA mechanisms to improve its performance in terms of the PDR and PRR, while preserving its distributed and lightweight nature
  9. Keywords:
  10. Packet Delivery Ratio ; Vehicular Ad Hoc Network (VANET) ; Institiute Electrical and Electronic Engineers (IEEE)802.11 Standard ; Performance Evaluation ; Intelligent Transportation System (ITS) ; Packet Reception Ratio

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  • Author's Declaration
  • Abstract
  • Acknowledgements
  • Dedication
  • List of Figures
  • List of Tables
  • List of Symbols and Abbreviations
  • Introduction
    • Motivation
    • Dataset Descriptions
  • Specifications of the IEEE 802.11p Protocol
    • IEEE 802.11 Distributed Coordination Function (DCF)
    • Physical Sub-layer in IEEE 802.11p
    • MAC Sub-layer in IEEE 802.11p
  • Literature Review
    • Performance Analysis of the IEEE 802.11p
    • Performance Enhancement of MAC Protocols in VANETs
  • The Semi-Markov Process Model
    • Random Processes
    • Analysis of Markov Chains
      • Discrete Parameter Case
      • Continuous Parameter Case
      • State Classification of Markov Chains
    • Long-term Behaviour of Markov Chains
    • Long-term Behaviour of Semi-Markov Chains
    • Explanation of the SMP Model
    • Solving the SMP Model
    • Summary
  • Quantitative Performance Evaluation
    • Problem Statement and System Assumptions
    • Evaluation of the i.i.d Assumption for Inter-vehicle Spacing
      • The Correlation Coefficient between Inter-vehicle Spacing
      • The Wald-Wolfowitz Runs Test
      • The Kolmogrov-Smirnov Test
    • Traffic-Dependent Counting Processes
      • The Renewal Theory and the Inter-vehicle Spacing Distribution
      • The Lognormal-distributed Inter-vehicle Spacing
      • The GEV-distributed Inter-vehicle Spacing
      • Validation
        • Validation for Lognormal-distributed Inter-vehicle Spacing
        • Validation for GEV-distributed Inter-vehicle Spacing
    • Quantitative Performance Evaluation of the IEEE 802.11p Protocol
      • Packet Delivery Ratio
        • Quantitative Analysis of PDR in Intermediate Traffic
        • Quantitative Analysis of PDR in Semi-sparse Traffic
      • The Mean Transmission Delay
        • Quantitative Analysis of Transmission Delay in Intermediate Traffic
        • Quantitative Analysis of Transmission Delay in Semi-sparse Traffic
    • The Interpretation of Results
    • Summary
  • A Network Model for VANETs
    • Motivation
    • System Assumptions
    • The Attachment Mechanism in Highway VANETs
    • Degree Distribution
      • Backward Degree Distribution
      • Forward Degree Distribution
      • Total Degree Distribution
    • Clustering Coefficient
    • Average Length of Shortest Paths
    • Validation
      • The I-80 Highway
      • The A6 and M40 Highways
    • Discussion
      • Non Scale-Free Degree Distributions and Absence of Hub Nodes
      • High Clustering Coefficient
      • Absence of Small-World Property
    • On the Independence of the Vehicles' Velocities
    • On Dynamics of the Vehicles' Velocities
      • The A6 Highway, 8:00 - 8:30
      • The A6 Highway, 11:30 - 12:00
      • The M40 Highway, 8:00 - 8:30
      • The M40 Highway, 11:30 - 12:00
    • More Examples for highly consistent conditions based on the BHL data set
      • More examples for highly consistent conditions in March 2011, during 16:00 - 17:00
      • More examples for highly consistent conditions in March 2011, during 17:00 - 18:00
      • More examples for highly consistent conditions in April 2011, during 16:00 - 17:00
      • More examples for highly consistent conditions in April 2011, during 17:00 - 18:00
    • Summary
  • Graph-based Performance Analysis
    • The Two-hop Degree Distribution
      • The Backward Two-hop Degree Distribution
      • The Forward Two-hop Degree Distribution
      • The Total Two-hop Degree Distribution
    • The Average Number of Common Neighbours
    • Packet Delivery Ratio
    • Packet Reception Ratio
    • Results
      • Structural Properties of the Communication Graph
        • Structural Properties of the Communication Graph in Intermediate Traffic
        • Structural Properties of the Communication Graph in Semi-sparse Traffic
      • The Quantitative Performance Analysis of the 802.11p Protocol in Broadcast Mode
        • Quantitative Analysis of the Packet Delivery Ratio (PDR)
        • The Quantitative Analysis of Packet Reception Ratio (PRR)
      • Comparative Analysis with Existing Approaches
      • Interpretation of Results
    • Summary
  • Performance Enhancement
    • Motivation
    • The Proposed Mechanism
    • Results
      • Average-based Performance Analysis
      • Quantitative Performance Analysis
    • Summary
  • Conclusion
  • Bibliography
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