First Advisor

Fu Li

Term of Graduation

Spring 2007

Date of Publication

5-1-2007

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.) in Electrical and Computer Engineering

Department

Electrical and Computer Engineering

Language

English

Subjects

Computer networks -- Management, Mobile communication systems, Wireless communication systems, Wireless LANs

DOI

10.15760/etd.8002

Physical Description

1 online resource (2, x, 132 pages)

Abstract

In Wireless Local Access Networks (WLANs), the Medium Access Control (MAC) protocol is the primary element that determines the efficiency of sharing the limited communication bandwidth of the wireless channel. IEEE 802.11 MAC uses the contention-based Distributed Coordination Function (DCF) as a fundamental medium access mechanism. However, the dynamic nature of the wireless environment creates mobility challenges of maintaining maximum channel capacity, of obtaining optimal throughput and latency, and of retaining good security in a distributed wireless network.

This dissertation first introduces a set of parameters to characterize the medium status and radio environment, and a mechanism for mobile devices to exchange measurements in order to obtain broad and comprehensive knowledge of the wireless environment. Then the dissertation proposes a distributed cooperative wireless architecture and framework, and three cooperative algorithms to optimize wireless network performance. The cooperative algorithms allow wireless devices to cooperatively adjust configurations and optimize operations based on the characteristics of the environment.

The first algorithm adaptively adjusts the contention window size to reduce the number of collisions as the number of mobile devices increases, in order to reach maximum channel utilization. However, if a channel reaches the saturated state, the throughput per user decreases significantly. Therefore, the second algorithm discussed in this dissertation is to select the best Access Point (AP) in overlapped AP coverage areas to balance network loads and maximally utilize the network capacity. When the mobile device transitions from one AP to another AP, it may take milliseconds to seconds due to required re-association and re-authentication with the new AP. Thus, the third cooperative algorithm optimizes the device transition to provide an acceptable balance of latency and security. The corresponding simulation or experiment results that demonstrate a significant improvement of wireless network performance are explained for each algorithm.

Forgery and confidentiality are major concerns for distributed radio resource measurement and cooperation. Thus, this dissertation concludes with an analysis of security threats to radio resource measurement and cooperation, and proposes an action frame protection scheme to ensure secure distributed cooperative wireless networks.

Rights

In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/

This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).

Comments

If you are the rightful copyright holder of this dissertation or thesis and wish to have it removed from the Open Access Collection, please submit a request to pdxscholar@pdx.edu and include clear identification of the work, preferably with URL.

Persistent Identifier

https://archives.pdx.edu/ds/psu/38596

Download

Share

COinS