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# Performance of Greedy Scheduling Algorithm in Wireless Networks

## Material Information

Title: Performance of Greedy Scheduling Algorithm in Wireless Networks
Physical Description: 1 online resource (114 p.)
Language: english
Creator: Li, Bo
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

## Subjects

Subjects / Keywords: channel-fading -- interference -- local-pooling -- longest-queue-first -- stability -- wireless-network-scheduling
Computer and Information Science and Engineering -- Dissertations, Academic -- UF
Genre: Computer Engineering thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

## Notes

Abstract: One of the major challenges in wireless networking is how to optimize the link scheduling decisions under interference constraints. Recently, a few algorithms have been introduced to address the problem. However, solving the problem to optimality for general wireless interference models typically relies on a solution of an NP-hard sub-problem. To meet the challenge, one stream of research currently focuses on finding simpler sub-optimal scheduling algorithms and on characterizing the algorithm performance. In the first piece of our work, we investigate the performance of a specific scheduling policy called Longest Queue First (LQF), which has gained significant recognition lately due to its simplicity and high efficiency in empirical studies. There has been a sequence of studies characterizing the guaranteed performance of the LQF schedule, culminating at the construction of the $\sigma$-local pooling concept by Joo et al. We refine the notion of $\sigma$-local pooling and use the refinement to capture a larger region of guaranteed performance. In the second piece of our work, we deeply analyze the performance guarantee of the LQF algorithm in order to shape the stability region furthermore. The contribution of this study is to describe three new achievable rate regions, which are larger than the previously known regions. In particular, the new regions include all the extreme points of the capacity region and are not convex in general. We also discover a counter-intuitive phenomenon in which increasing the arrival rate may sometime help to stabilize the network. This phenomenon can be well explained using the theory developed in this study. In the third piece of our work, we study the performance of LQF algorithm based on a more practical wireless network model, where channel fading effect is considered. Unlike the previous discussed network model, the wireless channel state is time varying under the effect of channel fading. As a result, the corresponding interference relationship among links could change under different channel states. Moreover, a subset of links, which determined by the current channel state, may be prohibited to transmit data and hence be pre-exclude from the scheduling process. We adopt a more generic channel fading model than that studied by Reddy et al, so that the variation of underlying interference relationship is allowed. We derive a larger stability region $\Sigma^*(G) \Lambda$, compared to the existed result, where $\Sigma^*(G)$ is a diagonal matrix. We also propose an estimation algorithm of $\Sigma^*(G)$, which provides a performance lower bound of LQF under any given channel fading structure.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Bo Li.
Thesis: Thesis (Ph.D.)--University of Florida, 2012.

## Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2012
System ID: UFE0044095:00001

## Material Information

Title: Performance of Greedy Scheduling Algorithm in Wireless Networks
Physical Description: 1 online resource (114 p.)
Language: english
Creator: Li, Bo
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2012

## Subjects

Subjects / Keywords: channel-fading -- interference -- local-pooling -- longest-queue-first -- stability -- wireless-network-scheduling
Computer and Information Science and Engineering -- Dissertations, Academic -- UF
Genre: Computer Engineering thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

## Notes

Abstract: One of the major challenges in wireless networking is how to optimize the link scheduling decisions under interference constraints. Recently, a few algorithms have been introduced to address the problem. However, solving the problem to optimality for general wireless interference models typically relies on a solution of an NP-hard sub-problem. To meet the challenge, one stream of research currently focuses on finding simpler sub-optimal scheduling algorithms and on characterizing the algorithm performance. In the first piece of our work, we investigate the performance of a specific scheduling policy called Longest Queue First (LQF), which has gained significant recognition lately due to its simplicity and high efficiency in empirical studies. There has been a sequence of studies characterizing the guaranteed performance of the LQF schedule, culminating at the construction of the $\sigma$-local pooling concept by Joo et al. We refine the notion of $\sigma$-local pooling and use the refinement to capture a larger region of guaranteed performance. In the second piece of our work, we deeply analyze the performance guarantee of the LQF algorithm in order to shape the stability region furthermore. The contribution of this study is to describe three new achievable rate regions, which are larger than the previously known regions. In particular, the new regions include all the extreme points of the capacity region and are not convex in general. We also discover a counter-intuitive phenomenon in which increasing the arrival rate may sometime help to stabilize the network. This phenomenon can be well explained using the theory developed in this study. In the third piece of our work, we study the performance of LQF algorithm based on a more practical wireless network model, where channel fading effect is considered. Unlike the previous discussed network model, the wireless channel state is time varying under the effect of channel fading. As a result, the corresponding interference relationship among links could change under different channel states. Moreover, a subset of links, which determined by the current channel state, may be prohibited to transmit data and hence be pre-exclude from the scheduling process. We adopt a more generic channel fading model than that studied by Reddy et al, so that the variation of underlying interference relationship is allowed. We derive a larger stability region $\Sigma^*(G) \Lambda$, compared to the existed result, where $\Sigma^*(G)$ is a diagonal matrix. We also propose an estimation algorithm of $\Sigma^*(G)$, which provides a performance lower bound of LQF under any given channel fading structure.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Bo Li.
Thesis: Thesis (Ph.D.)--University of Florida, 2012.