A Novel QoS-Aware MPEG-4 Video Delivery Algorithm over the Lossy IEEE 802.11 WLANs to Improve the Video Quality by Tanmoy Debnath BSc (Eng.), MSc (Eng.) A thesis submitted to the Dublin Institute of Technology for the degree of Doctor of Philosophy (PhD) Supervisor: Dr. Mark Davis Communications Network Research Institute (CNRI), School of Electronic and Communications Engineering, Dublin Institute of Technology (DIT), Dublin, Ireland. 2012 Declaration I certify that this thesis which I now submit for examination for the award of PhD, is entirely my own work and has not been taken from the work of others, save and to the extent that such work has been cited and acknowledged within the text of my work. This thesis was prepared according to the regulations for postgraduate study by research of the Dublin Institute of Technology and has not been submitted in whole or in part for another award in any Institute. The work reported on in this thesis conforms to the principles and requirements of the Institute's guidelines for ethics in research. The Institute has permission to keep, lend or copy this thesis in whole or in part, on condition that any such use of the material of the thesis be duly acknowledged. Signature: Date: 2 Acknowledgements I would like to express my gratitude to Dr Mark Davis for his valuable guidance over the years. I wish to thank the SFI (Science Foundation Ireland) for providing me with a scholarship. I am also grateful to Dr Mike Murphy, Dr Marek Rebow, and Dr Gerry Farrell for arranging additional funding which helped me to complete this research. Dr Nicola Cranley was gracious in sharing her knowledge of video and IP networks. Mr Stuart Wallace, Ms Yi Ding, and Ms Carina Teixeira De Oliveira were very helpful regarding discussion of programming codes while implementing the novel QoS aware MPEG-4 video delivery algorithm presented in this work. I am also appreciative of all the other CNRI staff, past and present, for creating a high quality working environment during the last number of years: Dr Mirosław Narbutt, Dr Marek Bykowski, Dr Claus Jürgensen, Dr Karol Kowalik, Dr Brian Keegan, Dr Mustafa Ramadhan, Mr Enrique Roqués Gómez, Mr Piotr Soboński, Mr David McGrath, Mr Chenzhe Zhang, Mr Yin Chen, Mr Jianhua Deng, and Mr Fuhu Deng. I would also like to thank Dr Hugh Byrne, Ms Louisa Hartnett, Ms Rosa Lopez, and Ms Sabrina Lane of the FOCAS building for their assistance over the years and Ms Gerolmina Di Nardo of the Graduate Research School and Ms Helen Jones of the Research Accounts for guiding me in various practical matters regarding the rules and regulations of our institution. No words can ever describe the enduring support and encouragement I receive from my parents, Anil Debnath and Ava Debnath, who gave me the license to pursue my dreams when I was a teenager. And the love and unswaying patience of my wife and best friend Dr Sourabhi Debnath have always helped me to overcome the rainy days. Our son Kingshuk Debnath was born just a week before my viva. I look forward to spending a happy and prosperous life with you guys! 3 Abstract Video traffic is bursty in nature and has different network requirements compared to other types of traffic (e.g. voice, data) in terms of bandwidth, delay, jitter, and loss etc. So it becomes important to manage video traffic on a WLAN carefully to achieve acceptable levels of Quality of Service (QoS). The unique contribution of this work is that it presents experimental and simulation studies of the performance of real video content streamed over WLAN networks. Under various test scenarios the performance of the WLAN network in terms of delay, loss, throughput etc. is analysed in the presence of background traffic. The effects of different types of server configurations and access contention between stations are also investigated for IEEE 802.11b and IEEE 802.11e networks. This work specifically considers the IPB fame based nature of MPEG- 4 encoded video. A novel QoS aware MPEG-4 video delivery algorithm is proposed and evaluated using a computer model written in the C programming language. The model exploits two mechanisms namely frame retransmission (ReTx) and GOP truncation (GOPT). The ReTx mechanism effectively increases the QoS by minimising the transmission losses at the expense of an increased buffer overflow probability. The GOPT mechanism reduces the probability of buffer overflow at the expense of a reduced QoS. The QoS aware MPEG-4 video delivery algorithm aims to achieve an optimal trade off between these two mechanisms in order to eliminate buffer overflow and minimise transmission losses. The algorithm aims to replace uncontrolled packet loss due to buffer overflow, MAC collisions, and transmission errors by a controlled prioritized packet loss scheme that permits a graceful degradation in MPEG-4 video quality streamed over IEEE 802.11b networks. This ensures the realisation of the most favourable network conditions for the delivery of MPEG-4 video frames on WLANs. Through extensive simulations it has been shown to provide a significant improvement in the QoS performance for video streaming applications for both uplink and downlink network scenarios in the presence of background traffic. 4 Table of Contents DECLARATION ................................................................................................2 ACKNOWLEDGEMENTS ....................................................................................3 ABSTRACT ................................................................................................4 LIST OF TABLES ..............................................................................................10 LIST OF FIGURES .............................................................................................12 ABBREVIATIONS AND ACRONYMS................................................................15 CHAPTER 1 INTRODUCTION................................................................21 1.1 Framework of the Thesis and Motivation ....................................................22 1.1.1 Problem Statement ............................................................................23 1.1.2 Significance of the Problem ...............................................................25 1.1.3 Contributions of This Thesis ..............................................................27 1.2 Thesis Outline............................................................................................31 1.3 Publications Arising from This Work ..........................................................32 CHAPTER 2 TECHNICAL BACKGROUND ...............................................33 2.1 Introduction to Wireless Local Area Networks ...........................................33 2.1.1 Different Standards.............................................................................34 2.1.2 General Description of the IEEE 802.11 WLANs ................................38 2.2 IEEE 802.11 Architecture............................................................................40 2.2.1 CSMA with Collision Detection (CSMA/CD)........................................41 2.2.2 CSMA with Collision Avoidance (CSMA/CA) ......................................41 2.2.3 Distributed Coordination Function (DCF) ............................................42 2.2.3.1 MAC Frame Types......................................................................42 2.2.3.2 The Access Method ....................................................................43 2.2.3.3 Inter-Frame Spacing (IFS) ..........................................................46 2.2.4 Shortcomings of the IEEE 802.11b Networks.....................................47 2.2.5 QoS for IEEE 802.11e – Enhancements to the MAC..........................48 2.2.6 IEEE 802.11e Modes..........................................................................49 2.2.6.1 Enhanced Distributed Channel Access (EDCA) .........................50 5 2.2.6.1.1 ECWmin and ECWmax ..........................................................53 2.2.6.1.2 Arbitration Inter-Frame Space Number (AIFSN) .................54 2.2.6.1.3 Transmission Opportunity (TXOP)......................................55 2.2.6.2 IEEE 802.11e HCCA ..................................................................57 2.2.6.3 IEEE 802.11n..............................................................................58 2.2.7 Different Types of Losses ...................................................................64 2.2.7.1 MAC Collision Loss.....................................................................64 2.2.7.2 Buffer Overflow Loss ..................................................................65 2.2.7.3 Transmission Loss......................................................................67 2.3 Video...........................................................................................................67 2.4 Video Streaming .........................................................................................78 2.4.1 Video Streaming Solutions..................................................................80 2.4.1.1 Commercial Video Streaming Solutions......................................80 2.4.1.2 Free and Open Source Video Streaming Solutions ....................82 2.5 Quality of Service (QoS) .............................................................................84 2.6 Challenges Associated with Video Streaming over WLANs.......................89 2.6.1 Video Quality Metrics..........................................................................91