Signals and Communication Technology Forfurther volumes: http://www.springer.com/series/4748 Hermann Rohling Editor OFDM Concepts for Future Communication Systems 123 Editor HermannRohling Institut fürNachrichtentechnik Technische UniversitätHamburg-Harburg Eißendorfer Str.40 21073Hamburg Germany e-mail: [email protected] ISSN 1860-4862 ISBN978-3-642-17495-7 e-ISBN 978-3-642-17496-4 DOI10.1007/978-3-642-17496-4 SpringerHeidelbergDordrechtLondonNewYork (cid:2)Springer-VerlagBerlinHeidelberg2011 This work is subject to copyright. 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Coverdesign:eStudioCalamar,Belin/Figueres Printedonacid-freepaper SpringerispartofSpringerScience+BusinessMedia(www.springer.com) The contents of this book is based on the work of the Priority Pro- gram TakeOFDM (SPP1163), funded by the German Research Foun- dation (Deutsche Forschungsgemeinschaft, DFG). v Preface Dearreaders, dearfriends, The Orthogonal Frequency-Division Multiplexing (OFDM) digital transmission technique has several advantages in broadcast and mobile communications appli- cations. Therefore, the German Research Foundation (DFG) funded a so-called priority program “Techniques, Algorithms, and Concepts for Future OFDM Sys- tems” (TakeOFDM), which started in 2004. The main objective of this research program is to study the specific research topics in a collaborative work between experts andyoung scientists fromdifferent universities. In broadcast applications like Digital Audio Broadcast (DAB), Digital Video broadcast (DVB-T), Digital Radio Mondiale (DRM), and single-cell WLAN sys- tems,the OFDM transmission technique is already mature and operational forsev- eral years. However, in wireless and wireline communications there is still need for furtherresearchandoptimization. TheOFDMtransmissiontechniquehasgaineda lotofattentioninresearch,andithasproventobeasuitablechoiceinthedesignof digitaltransmissionconceptsformobileapplications,suchastheLongTermEvolu- tion(LTE)standard,whichisthesystemproposalforthefourthgeneration(4G)of mobilecommunicationsystems. TheOFDMtransmission method,specific medium accesstechniques,cellularnetworkswithfullcoverage,andmultipleantennasystems have been playing an important andever-growing role in the 4Gdevelopment. Since2004,morethan15differentuniversitiesinover40specificresearchprojects have been contributing to the TakeOFDM program, covering a large variety of de- tailed aspects of OFDM and all related system design aspects. This TakeOFDM researchprojectledtoseveralPhDthesesandisabasisfortheyounggenerationof excellentscientificresearchersandstaff. Theresultshavebeenexchangedinseveral workshops,conferences, anddirectcooperations. Besidestopicsregardingthephys- ical layer, such as coding, modulation, and non-linearities, a special emphasis was putonsystemaspectsandconcepts,inparticularfocusingoncellularnetworksand multiple antenna techniques. The challenges of link adaptation, adaptive resource allocation, and interference mitigation in such systems were addressed extensively. Moreover, the domain of cross-layer design, i.e., the combination of physical layer aspects andissues ofhigher layers, was considered in detail. Thisbooksummarizesthemainresultsandgivesanoverviewofthecombinedre- searcheffortswhichhavebeenundertakeninthepast6yearswithintheTakeOFDM priority program. As a coordinator of the program, I would like to express my gratitude to the German Research Foundation (DFG) for their generous funding, continuous support and fruitful collaboration throughout the lifetime of the Take- OFDM project. Moreover, my sincere thanks go to all scientists for their excellent work on ahigh scientific level and their valuable contributions over the last years. vii viii Preface The aim of this book is to give a good insight into these efforts, and provide the reader with a comprehensive overview of the scientific progress which was achieved intheframeworkofTakeOFDM.Iamconvincedthatalsointhefuture,theseresults will facilitate and stimulate further innovation and developments in the design of modern communication systems, based on the powerful OFDM transmission tech- nique. Prof. Dr. Hermann Rohling Hamburg, June 2010 Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Radio Channel Behavior. . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Basics of the OFDM Transmission Technique. . . . . . . . . . . 5 1.3 OFDM Combined with Multiple Access Schemes . . . . . . . . 10 2 Channel Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 2.1 Joint Space-Time-Frequency Representation. . . . . . . . . . . . 16 2.1.1 Multidimensional Channel Sounding. . . . . . . . . . . . 17 2.1.2 Extraction of Parameters for Dominant MPCs . . . . 17 2.2 Deterministic Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.2.1 Relevant GTD/UTD Aspects. . . . . . . . . . . . . . . . . 18 2.2.2 Vechicle2X Channel Modeling . . . . . . . . . . . . . . . . 19 2.3 Stochastic Driving of Multi-Path Model . . . . . . . . . . . . . . . 20 2.3.1 Usage of the Large-Scale Parameters for Channel Characterization. . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.3.2 Relaying . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 2.3.3 Cooperative Downlink . . . . . . . . . . . . . . . . . . . . . . 24 3 Link-Level Aspects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.1 OFDM Data Detection and Channel Estimation. . . . . . . . . 33 3.1.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.1.2 Data Detection in the Presence of Nonlinear Distortions. . . . . . . . . . . . . . . . . . . . . 33 3.1.3 Joint Data Detection and Channel Estimation . . . . 39 3.2 Spreading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3.2.2 MC-CDM and MC-CAFS. . . . . . . . . . . . . . . . . . . . 48 3.2.3 Simulation Results. . . . . . . . . . . . . . . . . . . . . . . . . 49 3.2.4 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . 51 ix x Contents 3.3 Iterative Diversity Reception for Coded OFDM Transmission Over Fading Channels. . . . . . . . . . . . . . . . . . 54 3.3.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 3.3.2 Turbo Diversity. . . . . . . . . . . . . . . . . . . . . . . . . . . 55 3.3.3 Optimization for Turbo Diversity. . . . . . . . . . . . . . 56 3.3.4 Performance Evaluation. . . . . . . . . . . . . . . . . . . . . 57 3.3.5 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.4 MMSE-based Turbo Equalization Principles for Frequency Selective Fading Channels . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.4.2 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 3.4.3 MMSE Turbo Equalization Principles. . . . . . . . . . . 62 3.4.4 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 3.5 Peak-to-Average Power Ratio Reduction in Multi-Antenna Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 3.5.1 Introduction and Overview on PAR Reduction Schemes . . . . . . . . . . . . . . . . . . . . . . . . 69 3.5.2 PAR Reduction Schemes for MIMO Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 3.5.3 Numerical Results . . . . . . . . . . . . . . . . . . . . . . . . . 74 3.5.4 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 3.6 Single- vs. Multicarrier Transmission in MIMO and Multiuser Scenarios. . . . . . . . . . . . . . . . . . . . . . . . . . . 81 3.6.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 3.6.2 Point-to-Point MIMO Transmission. . . . . . . . . . . . 81 3.6.3 Up- and Downlink Scenarios in Multiuser Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 3.6.4 Aspects of Channel Coding. . . . . . . . . . . . . . . . . . . 84 3.6.5 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 3.7 Successive Bit Loading Concept . . . . . . . . . . . . . . . . . . . . . 90 3.7.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 3.7.2 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 3.7.3 Bit Loading Algorithm. . . . . . . . . . . . . . . . . . . . . . 92 3.7.4 Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94 3.7.5 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 3.8 Adaptive Transmission Techniques. . . . . . . . . . . . . . . . . . . 98 3.8.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 3.8.2 Adaptive Modulation and Coding. . . . . . . . . . . . . . 98 3.8.3 Adaptive MIMO Transmission. . . . . . . . . . . . . . . . 99 3.8.4 Signaling of the Bit Allocation Table . . . . . . . . . . . 102 3.8.5 Automatic Modulation Classification . . . . . . . . . . . 103 3.8.6 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Contents xi 4 System Level Aspects for Single Cell Scenarios . . . . . . . . . . . . . . 109 4.1 Efficient Analysis of OFDM Channels. . . . . . . . . . . . . . . . . 109 4.1.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 4.1.2 The Channel Matrix G. . . . . . . . . . . . . . . . . . . . . . 109 4.1.3 Common Channel Operator Models . . . . . . . . . . . . 111 4.1.4 Computing the Channel Matrix G . . . . . . . . . . . . . 112 4.2 Generic Description of a MIMO-OFDM-Radio- Transmission-Link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 4.2.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 4.2.2 System Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 4.2.3 Performance Analysis. . . . . . . . . . . . . . . . . . . . . . . 116 4.2.4 Generic Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 4.2.5 Summary and Further Work . . . . . . . . . . . . . . . . . 120 4.3 Resource Allocation Using Broadcast Techniques . . . . . . . . 122 4.3.1 Motivation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 4.3.2 Resource Allocation Algorithms . . . . . . . . . . . . . . . 122 4.4 Rate Allocation for the 2-User Multiple Access Channel with MMSE Turbo Equalization. . . . . . . . . . . . . . . . . . . . . 128 4.4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128 4.4.2 Turbo Equalization . . . . . . . . . . . . . . . . . . . . . . . . 128 4.4.3 Rate Allocation using EXIT Charts . . . . . . . . . . . . 129 4.4.4 Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 4.5 Coexistence of Systems. . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 4.6 System Design for Time-Variant Channels . . . . . . . . . . . . . 136 4.6.1 Multicarrier Systems for Rapidly Moving Receivers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 4.6.2 Highly Mobile MIMO-OFDM-Transmission in Realistic Propagation Scenarios . . . . . . . . . . . . . . . 138 4.7 Combination of Adaptive and Non-Adaptive Multi-User OFDMA Schemes in the Presence of User-Dependent Imperfect CSI. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 4.7.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142 4.7.2 Combining Transmission Schemes . . . . . . . . . . . . . 142 4.7.3 Numerical Results . . . . . . . . . . . . . . . . . . . . . . . . . 143 4.8 Integration of COFDM Systems with Multiple Antennas and Design of Adaptive Medium Access Protocols . . . . . . . 146 4.8.1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 4.8.2 MAC Frame for SDMA Operation and Spatial Grouping. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 4.8.3 Hardware Implementation of COFDM Systems with Multiple Antennas . . . . . . . . . . . . . . . . . . . . . 147 4.9 Large System Analysis of Nearly Optimum Low Complex Beamforming in Multicarrier Multiuser Multiantenna Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150