Maximizing OFDM Performance Through Real Time Adaptivity

224 Pages·2017·14.69 MB·English

by  Christian Blümm

UNIVERSITY
PRESS
Broadband wireless communication is nowadays dominated by the waveform
principle Orthogonal Frequency Division Multiplexing (OFDM). Its parameters
are typically designed conservatively to cope with the expected worst case
propagation channel. This makes the system more robust than required most
of the time, but it does conflict with throughput maximization. Next generation
standards, such as 5G, will not tolerate this waste of resources anymore and
also state-of-the-art systems call for optimization, especially those in extremely
varying environments.
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This book addresses an OFDM system, which configures itself in real time as ti
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a response to actual radio channel conditions. This makes it an adaptive radio, d
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which has been implemented in the course of diverse aeronautical projects
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for Airbus Group Innovations, Germany. It runs entirely on an FPGA platform, m
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which allows for real-time customization of various key parameters, including
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cyclic prefix, fast Fourier transformation, modulation and coding, dynamic e
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spectrum access and time division multiple access. Some of these parameters h
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are optimized through the results of an integrated channel sounder, which u
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reveals the actual delay spread and Doppler spread of the channel. h
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Proof of concept is provided by three demanding case studies: Aircraft-to- e
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ground flight telemetry, a communication scenario with an unmanned aerial n
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vehicle (UAV) and intra aircraft cabin dynamic spectrum access. m
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ISBN 978-3-96147-038-9 TY PRE Y PRES Blü
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Christian Blümm
Maximizing OFDM Performance Through Real Time Adaptivity
FAU Studien aus der Elektrotechnik

Band 8

Herausgeber der Reihe:

Prof. Dr. Günter Roppenecker
Christian Blümm
Maximizing OFDM Performance
Through Real Time Adaptivity
Erlangen
FAU University Press
2017
Bibliografische Information der Deutschen Nationalbibliothek:
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Sie sind nutzbar unter der Creative Commons Lizenz BY-NC-ND.

Der vollständige Inhalt des Buchs ist als PDF über den OPUS Server
der Friedrich-Alexander-Universität Erlangen-Nürnberg abrufbar:
https://opus4.kobv.de/opus4-fau/home

Verlag und Auslieferung:
FAU University Press, Universitätsstraße 4, 91054 Erlangen

Druck: docupoint GmbH

ISBN: 978-3-96147-038-9 (Druckausgabe)
eISBN: 978-3-96147-039-6 (Online-Ausgabe)
ISSN: 2363-8699
Maximizing OFDM Performance
Through Real Time Adaptivity
Maximierte OFDM-Effizienz
durch Echtzeit-Adaptivität
Der TechnischenFakultätder
UniversitätErlangen-Nürnberg
zurErlangungdes Grades
DOKTOR-INGENIEUR
vorgelegtvon
Christian Blümm
ausMünchen
AlsDissertationgenehmigtvonderTechnischenFakultät
derFriedrich-Alexander-UniversitätErlangen-Nürnberg
TagdermündlichenPrüfung: 25.10.2016
VorsitzenderdesPromotionsorgans: Prof. Dr.-Ing. ReinhardLerch
Gutachter: Prof. Dr.-Ing. Dr.-Ing. habil. RobertWeigel
Univ.-Prof. Dr.techn. MarioHuemer
Acknowledgments
In the preparation for my PhD, I carried out this work for many pleasant
yearsatAirbusGroupInnovations,OttobrunnincooperationwiththeInsti-
tuteforElectronicsEngineering,Friedrich-AlexanderUniversityofErlangen-
Nuremberg. Airbus provided an innovative multicultural and application-
oriented research environment with high-end equipment and appropriate
funding. Itmaderesearchenjoyableandfruitful.
First and foremost, I would like to express my deepest gratitude to my
mentorandsupervisorinOttobrunn, ChristophHeller. Healwaysinspired
mewithhisenthusiasmforsignalprocessingandelectronicsandsharedhis
amazinglywideandprofoundknowledgewithexpertiseandstrongpassion.
Withouthiscommitment,motivationandwillingnesstosupportandcoop-
erate in all situations, no matter what, when or how, this work would not
havebeenpossible.
I would like to thank especially my doctoral supervisor Prof. Robert
Weigel. With his charismatic “can do” and “go ahead” attitude and his way
tothinkofsolutionsratherthanofproblems,hegavemeallthefreedomto
focusonthatwhatreallymatters,theresearch.
I am grateful for Josef Schalk’s effort to provide me an Airbus position and
keepitopenagainstallodds. Heappreciatedmyworkandbelievedinme.
Next, I would like to thank Prof. Huemer from the JKU Institute of Signal
Processing,Linzforreviewingthiswork. IwouldhavelovedtoworkonUW-
OFDM,hadtheopportunitybeenavailable.
Furthermore, I gratefully acknowledge my students Alexandros Elefsiniotis
andAlexanderGanisfortheircontribution,enthusiasmandcommitmentto
thiswork.
I very much appreciate the support of Maximilian Hofmann, who encour-
agedmetokeepworkingandtookcareofthesubmissionprocedure.
IthankSuzanneGallagherforthelinguisticrevisionofthiswork.
Finally, I would like to thank my parents for all their boundless confidence
andencouragement. Theytrulygavemerootsandwings.
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Abstract
Withitselegantmixofsimplicityandefficiency,thewaveformprincipleor-
thogonal frequency division multiplexing (OFDM) became a tremendous
success in wireless and wired broadband communication within the past
few years. However, its dominance in most related standards nowadays is
just a momentary snapshot within a very dynamic technology field. More
efficientwaveformswillberequiredinthenearfuturetocopewiththeever-
increasingdemandfordatacommunication.
ThisthesishasemanatedfromresearchconductedforAirbusGroupIn-
novations, Germany. It gives insights of an implementation-centric study
fordiverseaeronauticalprojectsonhowefficiencyofwirelessOFDMcanbe
increased through applied parameter flexibility. Waveform parameters are
configuredaccordingtoactualchannelconditionsandrequirementsrather
thandesigningthemfortheexpectedworstcase,asdoneforstateoftheart
systems.
For the time being, the only thoroughly studied and established form
ofreal-timeadaptivityismodulationandcodingschemes(MCSs). Broader
deploymentofadaptivityhasbeensofarpreventedbyhithertomissingreal-
timeflexibilityoffurtherparameters. Asolutionisthedesignofasoftware
definedradio(SDR)entirelyonafieldprogrammablegatearray(FPGA)plat-
form. Thisstudypresentssuchademonstratorwithreal-timeflexiblekeypa-
rametersforOFDMsubcarrierusage,OFDMframelayoutandtimedivision
multipleaccess(TDMA)configurations,inadditiontoMCSs. Asecondpre-
requisiteforadaptivityistheabilitytofindthemostbeneficialparametriza-
tion. The proposed solution is an integrable channel sounder. It reveals
theactualdelayspreadandDopplerspread,whichhelpstooptimizecyclic
prefix(CP)andfastFouriertransformation(FFT)configurations. Moreover,
dynamic spectrum access (DSA) is implemented with a spectral energy de-
tectionscheme. Theoutcomeisafullyoperationalend-to-endcommunica-
tionsystemonaprototypelevel,whichcoversnetworklayer,linklayerand
component layer in both hardware and firmware aspects. Another novelty
isspectrallyflexibletimeandfrequencysynchronization.
Proof of concept and system characterizations have been carried out in
simulations,hardware-in-the-loop(HIL)measurementsandincasestudies.
Those case studies include an unmanned aerial vehicle (UAV) communica-
tionscenario,intra-aircraft-cabinDSAandaircraft-to-groundflightteleme-
try.
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