Design and Simulation of Spectrum Management Methods for Wireless Local Area Networks

263 Pages·2010·1.65 MB·English

by  Andreas Könsgen

Andreas Könsgen
Design and Simulation of Spectrum Management Methods
for Wireless Local Area Networks
VIEWEG+TEUBNER RESEARCH
Advanced Studies Mobile Research Center Bremen
Herausgeber | Editors:
Prof. Dr. Otthein Herzog
Prof. Dr. Carmelita Görg
Prof. Dr.-Ing. Bernd Scholz-Reiter
Das Mobile Research Center Bremen (MRC) erforscht, entwickelt und
erprobt in enger Zusammenarbeit mit der Wirtschaft mobile Informatik-,
Informations- und Kommunikationstechnologien. Als Forschungs- und
Transferi nstitut des Landes Bremen vernetzt und koordiniert das MRC
hochschulü bergreifend eine Vielzahl von Arbeitsgruppen, die sich mit der
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ergebnisse aus der Forschungstätigkeit der Mitglieder des MRC.
In close collaboration with the industry, the Mobile Research Center Bremen
(MRC) investigates, develops and tests mobile computing, i nformation and
communication technologies. This research association from the state of
Bremen links together and coordinates a multiplicity of research teams from
different universities and institutions, which are concerned with the deve-
lopment and application of mobile solutions. The series “Advanced Studies“
presents a selection of outstanding results of MRC’s research projects.
Andreas Könsgen
Design and Simulation
of Spectrum Management
Methods for Wireless
Local Area Networks
VIEWEG+TEUBNER RESEARCH
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Dissertation Universität Bremen, 2009
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Für meine Eltern • For my parents
(cid:0)(cid:0)(cid:2)(cid:3)(cid:2) • For Ira

Preface
Wireless communication has become an integral part of daily life which results
inanincreasingnumberofwirelessLANdevicesdeployedbothinbusiness,ed-
ucationalandresidentialenvironmentsandthusinincreasingmutualinterference
betweenthesedevices.Inaddition,therequirementsforthetransmissionplatforms
areincreasing:voice-over-IPorvideotelephonyrelyonquality-of-serviceguaran-
tees which have to be maintained even in case of concurrent access of multiple
users.
Thisworkdiscussespossiblesolutionsfortheabove-mentionedproblemsbased
on research work which I did in two projects funded by the German Research
Foundation (Deutsche Forschungsgemeinschaft, DFG): In CoCoNet, automated
spectrummanagementbetweenneighbouringnetworkstoreducemutualinterfer-
encewasinvestigatedwhileinXLayer,thefocuswastheresourceallocationofa
wireless LAN base station which serves a number of mobile terminals with data
flows.
IthankProf.CarmelitaGörgforgivingtheopportunitytoperformthisresearch
work under her supervision, and to Prof. Bernhard Walke, Stefan Mangold and
Guido Hiertz, Aachen University of Technology, for the cooperation in the Co-
CoNet research project and for providing the WARP2 simulator which was used
asaworkingbasisinthisanalysis.FurtherthankstoProf.Karl-DirkKammeyer,
University of Bremen, who co-supervised the XLayer project and was also a re-
viewerofthiswork.Furthermore,IthankRonaldBöhnkeandAndreasTimm-Giel
forthecooperationintheXLayerproject.
I also thank the development community of Linux and various software tools,
inparticulartheTEX/LATEXtypesettingsystem,whichwereusedtorunthesimu-
lationsandeditthemanuscript.
Finally,IwishtosaythankyoutomywifeIranganiforherendlesspatienceand
mentalsupportduringtheyearsthatIworkedonthisresearchproject.
AndreasKönsgen

Abstract
Wireless local area networks (WLANs) according to the IEEE802.11 standards
haverapidlyemergedinrecentyears.Increasingdemandsforqualityofservicere-
quireanefficientusageofspectrumresources.Optimisingtheworkingprinciples
of WLANs is possible in different ways. The interference between neighbouring
networks can be reduced by methods defined in the 802.11h standard: Dynamic
Frequency Selection (DFS) can change the frequency channel during an ongo-
ingconnection,whereasTransmitPowerControl(TPC)reducesthetransmission
powertoaminimumwhichisrequiredtotransmitwithagivendatarate.Forthe
data traffic inside a network, further optimisations are possible by centralised al-
location of airtime by the access point so that each user is served at an optimum
time;thisisdefinedin802.11e.Improvementscanalsobeachievedbyenhancing
theradiotransmissionbymultiple-antennasystems(MIMO),whichisconsidered
in802.11n.
However, the standards only describe the signalling, for example to initiate a
measurementortheassignmentofairtimetoacertainstation.Thedecisionmeth-
odstoaccessradiochannelresourcessuchasallocatingtransmitpowerorairtime
arenottreatedinthestandard.
Thesedecisionmethodsforthespectrummanagementarethetopicofthiswork.
The theoretical basics for the design of spectrum management methods are dis-
cussed. Based on this, different spectrum assignment methods for decentralised
and centralised networks are developed. In case of centralised channel access, a
cross-layer approach between the media access layer and the physical layer is
introduced which allows the assignment of channel resources both considering
the quality-of-service requirements of the applications and the conditions of the
MIMOradiochannel.
FortheinvestigationofnetworkscomplianttotheIEEE802.11standard,asim-
ulatorcalledWARP2isusedwhichisextendedbythespectrummanagementfunc-
tionsmentionedabove.
Theeffectsofthedifferentspectrummanagementalgorithmsontheinterference
andthequality-of-serviceparametersofthethroughputandlatencyareevaluated.
Itisshownthatbyspectrummanagementtheseparameterscanbesignificantlyim-
proved;thebestresultsareachievedifthedifferentspectrummanagementmeth-
ods are combined. An increase of the throughput also reduces the latency due to
smallerqueueingdelaysandlesschannelcongestion.Incaseofcentralisedaccess