An energy-aware and reliable MAC protocol for wireless sensor networks :Doctoral Dissertation - Major: Information Technology

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AN ENERGY-AWARE AND

RELIABLE MAC PROTOCOL

FOR WIRELESS SENSOR NETWORKS

Advisor: Prof. HOON OH

A thesis submitted to

The School of Computer Engineering and Information technology

The University of Ulsan

In partial fulfillment of the requirements for the degree of

Doctor of Philosophy

June 2011

The University of Ulsan

The School of Computer Engineering and Information Technology

HAN TRUNG DINH

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Approved by the Guidance Committee

for Han Trung Dinh’s Ph.D. Dissertation

Date approved: June 10th, 2011

The University of Ulsan

The School of Computer Engineering and Information Technology

HAN TRUNG DINH

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[ABSTRACT]

AN ENERGY-AWARE AND RELIABLE MAC PROTOCOL

FOR WIRELESS SENSOR NETWORKS

HAN TRUNG DINH

People and their properties are invaluable assets in society. However, workers may lose their lives

due to explosion, fire, suffocation by smoke or poisonous gas in industry working areas, and thus safe

work environments are critical for workers. Some safety applications were developed for ensuring

safety in the shipbuilding areas in Hyundai Heavy Industries Co., Ltd. (HHI); however, these

applications could not handle the problems of low power and reliable transmission because of lacking

reliable and energy efficient communication protocols. In this thesis, we aim at designing a new MAC

protocol that supports reliable communication and efficient energy management in terms of low power

consumption as well as the balancing of energy consumption throughout the network.

The thesis presents a robust sensor MAC protocol named I-MAC that can deal with reliable

transmission in mobility environment as well as supports energy efficiency and balancing. The I-MAC

is a TDMA-based MAC protocol that works on tree topology and requires a scheduling of time slots

throughout the whole free topology. Thus, we performed an in-depth study of slot scheduling

algorithm, and proposed a new slot scheduling algorithm named DSA (demand-based slot assignment).

This algorithm allocates time slots based on the bandwidth demand of each node in a tree topology. In

general, nodes at lower tree depths process more packets and consume more power than ones at higher

tree depths, and thus the imbalanced power consumption shortens network lifetime. The proposed

algorithm allocates a sequence of receiving slots, and then a sequence of transmission slots to each

node in tree topology. This way of slot assignment not only improves channel efficiency by removing

the number of wasted slots, but also contributes to reducing the power consumption of nodes at lower

depths greatly by allowing efficient data aggregation and filtering. The proposed algorithm is

compared with the frame-slot pair assignment algorithm which has been employed by the TreeMAC.

Simulation results show that the proposed algorithm far outperforms over the frame-slot assignment

algorithm in improving channel efficiency and in balancing power consumption.

The I-MAC employs the DSA algorithm for scheduling time slots for the nodes in a tree. In

addition, the I-MAC modifies the RTS/CTS and ACK control messages in order to react quickly to the

change of network topology and to perform efficient clock synchronization between pairs of

communication nodes. The simulation results show that the proposed I-MAC is robust not only in

static scenarios, but also in dynamic ones.

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ACKNOWLEDGEMENTS

To My Advisor – Prof. Hoon Oh

I would like to express my deep gratitude to Professor Hoon Oh, who gave me an opportunity to do my Ph.D. at the

Ubicom Lab. During three years at Korea, he not only taught me how to do research, but also supported me about living

accommodations. Before my family came to Korea for visiting, he drove me around the university to rent a house. It is a

really nice memory for me about him since a professor rarely supports a student like that. Moreover, he used to take me

somewhere for drinking and talking after work. By taking together, we gradually understood each other. This not only gave

us a chance to share our thinking but also help us to work efficiently; therefore, we achieved many positive results on our

research. Especially, he gave me an opportunity to come back Vietnam for supporting my wife when my second daughter

was born last year. This proved that he is very kind and generous. Those things let me know that he is the best professor

that I have never seen. Again, I would like to say thank you to him, my professor.

To My Lab Members

I would like to say thank you to you all, especially Korean members, who supported me during the time I stayed in Korea.

To My Parents

My achievement today is a gift that I would like to give for my parents. Although the gift is too late for my father since he

had passed away for a long time due to incurable illness, I know that he is attending to what I am doing. For my mother, the

achievement is the biggest gift of her life. She is waiting for me day after day since I went to South Korea for studying at

2008. I know that she always worries about me even though I am adult now. I cannot give her anything instead of giving

her special thanks with all my respects. I pray that my mother has good health and happy life. I love you, my mother.

To My Wife

I would like to give special thanks to my wife for her love and support. She not only has been working and taking care of

my daughters, but also encouraging me to continue my study for the last three years. I know that she is almost exhausted

due to a large amount of pressured works. However, I cannot do anything to help her except that I have tried my best to

finish my Ph.D. so that I comeback Vietnam to share her works. I know that my study achievement is the biggest present

for her because she expects very much about my career. I would like to send my love words to her and I wish that we have

a happy life. I am going to comeback with you, my darling.

To My Daughters

The biggest happiness of my life is having you two, my daughters. I miss you very much but I have to control myself to

work. Sometimes, I cannot concentrate on my work due to thinking of you two. I am trying my best to have the best living

accommodations for our family. I wish that you two grow into healthy, beautiful, brilliant girls, and filial respect to your

parents. I love you so that I can do everything for you. You are my invaluable assets, my daughters.

Ulsan April 13rd, 2011

Han Trung Dinh