Analyse et amélioration conjointe de la consommation d'énergie et des débits de TCP dans les réseaux ad hoc sans fil, TCP performance study and enhancements within wireless multi-hop ad hoc network environments

Alaa Seddik

Description

Sous la direction de Nazim Agoulmine
Thèse soutenue le 30 mars 2009: Evry-Val d'Essonne
Les réseaux ad hoc diffèrent des réseaux filaires par la multitude de perturbation auxquels ils sont sujets. Alors qu’une rupture de lien est un événement plutôt rare sur des réseaux filaires, et généralement imputable à l’état physique du matériel intermédiaire, cet événement est courant avec les communications radio. Ceci est lié à la qualité du signal reçu de l’autre extrémité ou à la configuration de l’environnement. Les perturbations causées par l’environnement ne mènent pas seulement à une rupture d’un lien, elles peuvent avoir un impact sur la réception des données. La volatilité des liens est typique dans les réseaux sans fil alors pour les réseaux filaires ce problème est inexistant. TCP, qui est prévu pour assurer la transmission fiable des données, n’a été conçu qu’en tenant compte des contraintes des réseaux filaires. Ainsi, certains événements dans la transmission de données sans fil peuvent être mal interprétés et engendrer une mauvaise réaction de TCP. Pour améliorer la performance de TCP dans les réseaux ad hoc, l’objectif de cette thèse est double. Dans un premier temps, une étude complète des performances de TCP dans les réseaux ad hoc est dressée. Celle-ci concerne à la fois les débits atteignables et aussi la consommation d’énergie induite par l’utilisation de ce protocole de transport dans un réseau ad hoc. Cette étude permet d’identifier les points d’amélioration de TCP pour qu’il soit utilisable dans les réseaux ad hoc. Dans un second temps, nous proposons une nouvelle variante de TCP, appelée TCP-WELCOME, dont l’objectif est de traiter de façon adéquate les différents types de perte de paquets sur un réseau ad hoc et optimiser la performance de TCP.
-Optimisation de performance
Wireless ad hoc networks are different from wired networks by the multitude of data packet loss situations they are subjected to. This is due to the characteristics of wireless channel that might obstruct the proper reception of data packet at the destination end. In some case, these vulnerabilities of wireless channel can result in a complete link failure. Although link failure is of low probability in wired networks, it is rather common in wireless networks. The volatility of communication channel is a typical problem with wireless links, which is not the case with wired cables. TCP is a transport protocol that aims at ensuring high reliability and guarantying reception of data packets. However, TCP was designed for wired networks to address congestion, which is the main cause for data packet loss in wired networks. Therefore, other types of data packet loss encountered in wireless networks are prone to misinterpretation by TCP, which will lead to TCP performance degradation within the network. To overcome the performance limitation of TCP when used within ad hoc networks, the aim of this thesis is twofold. First, a complete performance study of TCP over ad hoc networks is achieved. This evaluation concerns two performance metrics: the achievable throughput and the energy consumption of TCP within ad hoc networks. This study allows identifying the potential room of improvement to enhance TCP efficiency in ad hoc networks. Second, we propose a new TCP variant, TCP-WELCOME that optimizes the performance of TCP in ad hoc networks through its ability to distinguish among, and efficiently deal with, different data packet loss situations, within ad hoc networks.
-Performance optimization
Source: http://www.theses.fr/2009EVRY0006/document

Informations

• Publié par: Thesee
• Nombre de lectures: 16
• Langue: English
• Poids de l'ouvrage: 2 Mo

Extrait

DEDICATION


To my father, who had been the source of my motivation and inspiration,
whose presence I feel all the time though he's no longer among us.
To my mother, who encouraged and cared for me.
To my husband whose backing and support never faltered along the way.
To my dear daughters who, though I wasn't always there, kept loving me
every day.






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ACKNOWLEDGEMENT
This work would have never been possible without all those wonderful people who
surrounded me and supported me every step in the way.
I would like to express my deep and sincere gratitude to my supervisor, Dr. Yacine GHAMRI-
DOUDANE, Professor at ENSIIE. I've been fortunate to benefit from his wide knowledge and deep
experience. He's been always driving me to pursue excellence and go beyond what I deemed
possible. His understanding, encouragement, and personal guidance were what made it possible
to complete this thesis.
I warmly thank Dr. Sidi-Mohammed SENOUCI, Orange Labs, for his valuable advice and
continuous support. I'm grateful for his help in presenting and coordinating my work with
Orange Labs that lead to the successful delivery of the research project to France Telecom.
I am very grateful to Professor Dr. Nazim AGOULMINE, Head of LRSM, University of Evry, for
his detailed and constructive comments, and for his significant support and guidance throughout
this work.
I would like to thank Professor Véronique VEQUE, University Paris-Sud 11, and Professor
Tijani CHAHED, INT, for accepting to review my work and for their constructive comments.
Also, I would like to thank Dr. Bashar EL HASSAN, Faculty of engineering, University of
Libanon, and Professor André-Luc BEYLOT, ENSEEIHT, IRIT Laboratory, for accepting to
evaluate my work.
I also want to thank my colleagues with whom I collaborated and for whom I have great
regard, and I wish to extend my warmest thanks to all those who have helped me with my work
in LRSM, ENSIIE, and the Univeristy of Evry.
My thanks go as well to France Telecom's Orange Labs, who provided scientific and financial
sponsorship for this research and provided all the means to have it realized.
I owe my loving thanks to my family, my husband Khaled SEDDIK and my daughters Rana
and Noura. Without my husband’s encouragement, understanding, and the love of my daughters,
it would have been impossible for me to make this achievement.
Evry, France, March 2009
Alaa GHALEB


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RÉSUMÉ
Les réseaux sans fil ad hoc diffèrent des réseaux filaires traditionnels principalement par la
multitude de perturbation auxquels ils sont sujets. Alors qu’une rupture de lien est un
événement plutôt rare sur des réseaux filaires, et généralement imputable à l’état physique du
matériel intermédiaire (câbles, routeurs, etc.), cet événement est courant avec les
communications radio. Ceci peut être lié à la qualité du signal reçu de l’autre extrémité ou à la
configuration de l’environnement (épaisseur et quantité des obstacles intermédiaires,
perturbations électromagnétiques…). De plus, même si les perturbations causées par
l’environnement ne mènent pas toujours à une rupture d’un lien, elles peuvent aussi avoir un
impact sur la réception sans erreurs des données. Cette volatilité des liens est typique dans les
réseaux sans fil alors que pour les réseaux traditionnels filaires ce problème est inexistant.
Le protocole TCP, qui est prévu pour assurer la transmission fiable des données, n’a été conçu
qu’en tenant compte des contraintes des réseaux filaires. Ainsi, certains événements dans la
transmission de données sans fil peuvent être mal interprétés et engendrer une mauvaise
réaction de la part de TCP. Cette mauvaise interprétation affaiblit les performances plus qu’elle
ne l’améliorerait.
Pour réduire le fossé de performance dont souffre TCP dans les réseaux sans fil ad hoc,
l’objectif de cette thèse est double. Dans un premier temps, une étude complète des
performances de TCP dans les réseaux ad hoc est dressée. Celle-ci concerne à la fois les débits
atteignables mais aussi la consommation d’énergie induite par l’utilisation de ce protocole de
transport dans un réseau sans fil ad hoc. Cette étude permet d’identifier les points
d’amélioration du protocole TCP pour qu’il soit utilisable dans les réseaux sans fil ad hoc. Dans
un second temps, nous proposons une nouvelle variante de TCP, appelée TCP-WELCOME, dont
l’objectif est de traiter de façon adéquate les différents types de perte de paquets sur un réseau
ad hoc sans fil et par la même optimiser la performance de TCP.
iii
ABSTRACT
Wireless ad hoc networks are differentiated from traditional wired networks by the
multitude of data packet loss situations that they are subjected to. This is due to the intrinsic
characteristics of the wireless channel (e.g. signal fading, interference, obstacles, and
environment effects) that might obstruct the proper reception of data packet at the other
communication end. Moreover, in some case, these vulnerabilities of the wireless channel can
result in a complete link failure. Although link failure is of low probability in wired networks
since physical cables constitute the data transmission media, it is rather common wireless
networks (due to nodes’ mobility, battery depletion, obstacles, or some other wireless-channel-
related effect). The volatility of the communication channel is a typical problem with wireless
links, which is not the case with wired cables.
TCP is a transport protocol that aims at ensuring high reliability and guaranteed reception of
data packets. However, TCP was designed primarily for wired networks to address network
congestion, which is the main cause for data packet loss in wired networks. Therefore, other
types of data packet loss encountered in wireless networks are prone to misinterpretation by
TCP, which, in turn, will lead to degradation in the performance of TCP within the network.
In order to overcome the performance limitation of TCP when used within wireless ad hoc
networks, the aim of this thesis is twofold. First, a complete performance evaluation study of
TCP over wireless ad hoc networks is achieved. This evaluation deals with two performance
metrics: the achievable throughput and the energy consumption of TCP within wireless ad hoc
networks. This study allows identifying the potential room of improvement to enhance TCP
efficiency in wireless ad hoc networks. Second, we propose a new TCP variant we called TCP-
WELCOME, that optimizes the performance of TCP in wireless ad hoc networks through its
ability to distinguish among, and efficiently deal with, different data packet loss situations,
encountered within wireless ad hoc networks.
iv
GLOSSARY

Ad Hoc A wireless, autonomous communication mode that does not
require infrastructure configuration.

Acknowledgement, ACK A packet message, used in the Transmission Control Protocol
that is sent by the receiver to acknowledge the sender the
receipt of a certain packet(s).

Congestion A saturation of communication links due to much data
transmitted simultaneously by the network’s nodes. This results
in both data packet loss and extra transmission delays over the
connection.

Congestion Window, CWND The maximum amount of data bytes that can be sent out over
the connection without being acknowledged.

Congestion Avoidance A phase where TCP enters after Slow-Start phase. In this phase,
the TCP CWND increases slowly in order to avoid network
congestion.

Duplicate ACK, dupack TCP receivers generate a duplicate acknowledgment when out-
of-sequence segment is received. This one acknowledges only
some of packets outstanding at the start of the Fast Recovery.

MANET A type of wireless ad hoc network that is self-configuring
network of mobile devices connected through wireless links.
Each MANET device is free to move independently.

Segment A TCP segment is the packet of information that TCP uses to
exchange data with its peers. TCP receives data from a data
stream, segments it into chunks, and adds a TCP header creating
a TCP segment.

Slow Start Threshold, SSThresh The slow-start threshold that is used to define the transition
from slow-start phase to congestion avoidance phase.

Round Trip Time, RTT RTT is the delay that corresponds to the time needed by the TCP
sender after sending a data packet to receive its
acknowledgment.

Retransmission Time out, RTO RTO is the maximum time that TCP waits for the data
acknowledgment before declaring that the packet is lost.




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TABLE OF CONTENTS
Dedication ...................................................................................................................................................................