QoS Scheduling in IEEE801.16/WiMAX Networks QoS Scheduling in IEEE802.16/WiMAX Networks Mohammad Hamidullah

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  • QOS SCHEDULING IN IEEE802.16/WIMAX NETWORKS

    Mohammad Hamidullah Ahmad

    A thesis

    in

    The Department

    of

    Computer Science & Software Engineering

    Presented in Partial Fulfillment of the Requirements

    For the Degree of Master of Computer Science

    Concordia University

    Montréal, Québec, Canada

    June 2011

    c⃝ Mohammad Hamidullah Ahmad, 2011

  • CONCORDIA UNIVERSITY

    School of Graduate Studies

    This is to certify that the thesis prepared By: Mohammad Hamidullah Ahmad Entitled: QoS Scheduling in IEEE802.16/WiMAX Networks and submitted in partial fulfillment of the requirements for the degree of Master of Computer Science complies with the regulations of the University and meets the accepted standards with respect to originality and quality. Signed by the final examining committee: ______________________________________ Chair Dr. Y. Yan ______________________________________ Examiner Dr. L. Narayanan ______________________________________ Examiner Dr. T. Fancott ______________________________________ Supervisor Dr. B. Jaumard Approved by ________________________________________________ Chair of Department or Graduate Program Director

    ________________________________________________ Dr. Robin A.L. Drew, Dean

    Faculty of Engineering and Computer Science

    Date __________________________________________

  • Abstract

    QoS Scheduling in IEEE802.16/WiMAX Networks

    Mohammad Hamidullah Ahmad

    WiMAX/IEEE802.16 is a major broadband wireless access technology that provides an

    affordable alternative to conventional wired techniques in supporting high-speed data, video

    and voice services. It is quite challenging to provide Quality of Service (QoS) in wireless

    networks, which guarantees different service classes meeting specific requirements. In our

    current work, we have presented a bandwidth scheduling algorithm to facilitate end-to-

    end QoS in IEEE802.16/WiMAX network. A differentiated service (DiffServ) approach

    is adopted, which serves QoS provisioning by differentiating multiple traffic classes into

    individual service flows. There exists a number of well-known traffic scheduling algorithms

    for scheduling wireless traffic. However, a few of them can differentiate services and, in

    the literature, attempts have been made to use different scheduling algorithms for different

    services to meet the service class constraints. This approach of having different algorithms

    dealing different traffic classes leads to increased scheduler design complexity and eventual

    challenging implementation. Furthermore, the majority of these available algorithms assume

    the preexistence of Call Admission Control and thus describes the scheduling and resource

    allocation algorithm without having any interactivity with Admission Control mechanism.

    This approach is unrealistic since scheduling and admission control are strongly related

    in QoS provisioning. In this thesis, a novel scheduling algorithm has been proposed in

    iii

  • combination with a Call Admission policy for WiMAX OFDMA/TDD systems, utilizing

    dynamic preference function that determines transmission order and bandwidth allocation

    on sub-carrier basis. The dynamic preference function takes into account the required

    throughput of a request, the current data rate, the expiry of the remaining bits and the

    signal strength to dynamically determine the best subcarrier through the usage of adaptive

    modulation and coding. The QoS requests get allocation in the order of the best subcarrier

    available; that is, the highest priority QoS requests are allotted the best subcarriers with

    greater bandwidth capacity in an OFDMA symbol, whereas the lowest priority requests

    get allocation of lower quality subcarriers, if required more than one of them to maintain

    the required data rate. Consequently, in our method the lower priority QoS requests also

    have a chance of being served in every round of scheduler execution. Thus our algorithm

    allows fairness for all classes of requests, also maintaining priorities for the higher classes

    of traffic. System performance is evaluated using simulations. Numerical results show that

    the proposed scheduling algorithm is efficiently able to handle multi-class QoS in WiMAX

    uplink systems with fair allocation of available resources among the admitted requests.

    iv

  • Acknowledgments

    I would like to thank the Almighty God for His divine guidance and blessings bestowed

    upon me throughout my life and particularly during this time that have made this thesis

    possible.

    I am grateful to my supervisor, Dr. Brigitte Jaumard who provided guidelines on

    how to select the research topic and progress with the research work. Her understanding,

    encouragement, personal guidance, and great efforts to explain things clearly and simply to

    me, have provided a good basis for this thesis work.

    I also wish to thank all the faculty members and staff of the Computer Science De-

    partment. I am grateful to the Faculty of Engineering and Computer Science, Concordia

    University for supporting this thesis work.

    My special gratitude goes to my friends and family. Without their encouragement and

    mental support it would have been impossible for me to continue and complete this long

    journey.

    Finally, I would like to dedicate my thesis to my parents, who have always been an

    immense source of support and encouragement in a way that none can ever be.

    v

  • Contents

    List of Figures ix

    List of Tables xi

    Acronym xii

    1 Introduction 1

    1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

    1.2 Research Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

    1.3 Thesis Contribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

    1.4 Thesis Organization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

    2 Overview of Broadband Wireless Access (BWA) 6

    2.1 The Key Technologies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

    2.1.1 WiMAX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

    2.1.2 LTE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

    2.1.3 LTE vs. WiMAX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

    2.2 A Brief History of WiMAX/IEEE802.16 . . . . . . . . . . . . . . . . . . . . 8

    2.3 Packet Transmission Systems . . . . . . . . . . . . . . . . . . . . . . . . . . 11

    vi

  • 2.3.1 MAC layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

    2.3.2 PHY layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

    2.3.3 Popular PHY-MAC Configurations . . . . . . . . . . . . . . . . . . . 14

    2.4 QoS in Wireless Networks . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

    2.4.1 QoS Parameters in IEEE802.16/WiMAX . . . . . . . . . . . . . . . 17

    2.4.2 QoS Mechanisms in IEEE802.16/WiMAX . . . . . . . . . . . . . . . 18

    2.4.3 Traffic Classes (Scheduling Services in the Standard) . . . . . . . . . 19

    3 Literature Review 21

    3.1 General Scheduling Algorithms . . . . . . . . . . . . . . . . . . . . . . . . . 22

    3.2 Non-QoS Scheduling Algorithms - Mesh and Relay Based Network . . . . . 23

    3.3 QoS scheduling algorithms - Mesh Network and Relay Based Network . . . 23

    3.4 QoS scheduling algorithms - PMP Network - Area of Investigation . . . . . 24

    4 QoS Scheduling and Resource Allocation in IEEE802.16 Network 30

    4.1 OFDMA Resource Allocation Model . . . . . . . . . . . . . . . . . . . . . . 30

    4.2 Channel Fading Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

    4.3 Scheduling and Resource Allocation in WiMAX network . . . . . . . . . . . 37

    4.3.1 Problem Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

    4.3.2 Mathematical Formulation . . . . . . . . . . . . . . . . . . . . . . . 37

    4.3.3 Multi-class QoS Scheduling and Resource Allocation Algorithm . . . 39

    4.4 Admission Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

    4.4.1 Bandwidth Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

    4.4.2 Delay Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

    4.4.3 Relating Bandwidth and Delay . . . . . . . . . . . . . . . . . . . . . 46

    vii

  • 5 Experimental Results and Analysis 51

    5.1 Simulation Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

    5.2 Simulation Results: Proper Management of the QoS Requirements . . . . . 52

    5.3 Comparison of Resource Allocation performance with other QoS scheduling

    schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

    5.4 Comparison of Admission Control policy performance . . . . . . . . . . . . 58

    6 Conclusion 64

    6.1 Summary of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

    6.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

    Bibliography 75

    vii