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Document Type

Dissertation

Degree

Doctor of Philosophy

Department

Electrical Engineering

First Advisor's Name

Kia Makki

First Advisor's Title

Committee Co-Chair

Second Advisor's Name

Hao Zhu

Second Advisor's Title

Committee Co-Chair

Third Advisor's Name

Shih-Ming Lee

Fourth Advisor's Name

Niki Pissinou

Date of Defense

11-3-2008

Abstract

Due to low cost and easy deployment, multi-hop wireless networks become a very

attractive communication paradigm. However, IEEE 802.11 medium access control

(MAC) protocol widely used in wireless LANs was not designed for multi-hop wireless

networks. Although it can support some kinds of ad hoc network architecture, it does not

function efficiently in those wireless networks with multi-hop connectivity. Therefore,

our research is focused on studying the medium access control in multi-hop wireless

networks. The objective is to design practical MAC layer protocols for supporting multihop

wireless networks. Particularly, we try to prolong the network lifetime without

degrading performances with small battery-powered devices and improve the system

throughput with poor quality channels.

In this dissertation, we design two MAC protocols. The first one is aimed at

minimizing energy-consumption without deteriorating communication activities, which

provides energy efficiency, latency guarantee, adaptability and scalability in one type of

multi-hop wireless networks (i.e. wireless sensor network). Methodologically, inspired by the phase transition phenomena in distributed networks, we define the wake-up

probability, which maintained by each node. By using this probability, we can control the

number of wireless connectivity within a local area. More specifically, we can adaptively

adjust the wake-up probability based on the local network conditions to reduce energy

consumption without increasing transmission latency. The second one is a cooperative

MAC layer protocol for multi-hop wireless networks, which leverages multi-rate

capability by cooperative transmission among multiple neighboring nodes. Moreover, for

bidirectional traffic, the network throughput can be further increased by using the

network coding technique. It is a very helpful complement for current rate-adaptive MAC

protocols under the poor channel conditions of direct link. Finally, we give an analytical

model to analyze impacts of cooperative node on the system throughput.

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