Performance Analysis of Frame Aggregation Based IEEE 802.11n Wireless Local Area Network (WLAN)

ABSTRACT 

The IEEE 802.11 Wireless Local Area Network (WLAN) standard was able to ease the communication difficulty by providing mobility and low cost of system deployment for its users. On the other hand, the WLAN has difficulty in meeting the optimum Quality of Service (QoS)demand for data applications. Consequently, a later variant of the amendment standard, IEEE 802.11n, came with improvement strategies. The introduction of frame aggregation, block acknowledgment and reverse direction protocol techniques at the Media Access Control (MAC) sub-layer of the Datalink layer reduced the overhead cost to an optimum value. This work analyzed the performance of MAC Service Data Unit (MSDU) frame aggregation technique at variable aggregation sizes and number of contending stations in an error-prone WLAN channel. The frame aggregation technique was selected for analysis based on its popularity as compared to other MAC improvement techniques. Firstly, an analytical approach that models the network based on discrete time Markov chain (DTMC) was developed and then simulated in MATLAB environment. The values of the MSDU frame aggregation sizes, the variable number of contending stations and variable bit-error-rate (BER) values of the WLAN channel were chosen arbitrarily but within the practical range for a number of simulation cycles. Based on the generated results, it was observed that the MSDU aggregation size should not be increased beyond 46 for the various BER values of the channel considered for this work else the performance throughput would depreciate. This performance information is very resourceful for optimal design and implementation of frame aggregation technique in the WLAN network.

TABLE OF CONTENTS

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TITLE PAGE - - - - - - - - - - - i

APPROVAL PAGE - - - - - - - - - - ii

CERTIFICATION - - - - - - - - - - iii

DECLARATION - - - - - - - - - - iv

DEDICATION - - - - - - - - - - v

ACKNOWLEDGEMENT- - - - - - - - - - vi

ABSTRACT - - - - - - - - - - - vii

TABLE OF CONTENTS - - - - - - - - - viii

LIST OF FIGURES - - - - - - - - - xii

LIST OF TABLES - - - - - - - - - - xiv

ACRONYMS - - - - - - - - - - xv

CHAPTER ONE INTRODUCTION - - - - - - - 1

1.1 Background - - - - - - - - - - 1

1.2 Problem Statement - - - - - - - - - 2

1.3 Objective - - - - - - - - - - 3

1.4 Scope - - - - - - - - - - - 3

1.5 Methodology - - - - - - - - - - 4

1.6 Thesis Outline - - - - - - - - - 4

CHAPTER TWO LITERATURE REVIEW - - - - - - 6

2.1 Background on IEEE 802.11 WLAN Technology - - - - - 6

2.1.1 IEEE802.11n - - - - - - - - - 7

2.1.2 IEEE 802.11 WLAN Architecture - - - - - - 10

2.1.2.1 Ad Hoc Topology - - - - - - - 10

2.1.2.2 Infrastructure Topology - - - - - - 11

2.1.2.3 Service Set - - - - - - - - 12

2.1.3 IEEE 802.11 WLAN Logical Service - - - - - 13

2.1.4 IEEE 802.11 Protocol of Operation - - - - - - 16

2.1.4.1 Distributed Coordination Function (DCF) - - - - 17

2.1.4.1.1 Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) Protocol - - - - - 18

2.1.4.2 Point Coordination Function (PCF) - - - - - 26

2.1.4.3 Hybrid Coordination Function (HCF) - - - - 26

2.1.5 IEEE 802.11 WLAN Frame Format - - - - - - 27

2.1.5.1 Frame Types - - - - - - - - 30

2.1.5.2 Frame Aggregation - - - - - - - 32

2.1.5.2.1 Aggregate MAC Service Data Unit (A-MSDU) - - 33

2.1.5.2.2 Aggregate MAC Protocol Data Unit (A-MPDU)- - 33

2.1.6 IEEE 802.11 MAC Management Mechanism - - - 35

2.1.6.1 Stations Registration Mechanism - - - - - 35

2.1.6.2 Stations Handoff Mechanism - - - - - 36

2.2 Research Works in the Area - - - - - - - - 37

2.2.1 Performance Analysis- - - - - - - - 37

2.2.2 Performance Improvement - - - - - - - 46

2.2.3 Conclusion - - - - - - - - - 50

CHAPTER THREE METHODOLOGY - - - - - - - 52

3.1 Background - - - - - - - - - - 52

3.2 IEEE 802.11n Network Architecture - - - - - - 52

3.3 System Modeling - - - - - - - - - 53

3.3.1 Analytical Model - - - - - - - - 54

3.3.2 Aggregation Frame Model - - - - - - - 58

3.3.3 Stations Contention Model - - - - - - - 60

3.3.3.1 Throughput - - - - - - - - 64

3.3.3.2 Average Access Delay - - - - - - - 66

3.3.4 Simulation Program Model - - - - - - - 67

CHAPTER FOUR RESULTS AND DISCUSSION - - - - - 71

4.1 Background - - - - - - - - - - 71

4.2 Simulation of Models - - - - - - - - - 71

4.2.1 Scenario One: Simulation ofan Increasing Number of Aggregationand a Fixed Number of Contending Stations - - 73

4.2.1.1 Throughput - - - - - - - - 73

4.2.1.2 Average Access Delay - - - - - - 75

4.2.2 Scenario Two: Simulation of an Increasing Number of Contending Stations

Anda Fixed Aggregation Size - - - - 77

4.2.2.1 Throughput - - - - - - - - 78

4.2.2.2 Average Access Delay - - - - - - 79

CHAPTER FIVE CONCLUSION AND RECOMMENDATION - - - 84

5.1 Background - - - - - - - - - - 84

5.2 Conclusion - - - - - - - - - - 84

5.3 Recommendation - - - - - - - - - 86

5.4 Further Work - - - - - - - - - - 86

REFERENCES - - - - - - - - - - 88

APPENDIX Matlab Script for the Simulation Model - - - - - 97