Wireless Connectivity

Petar Popovski is a Professor of Wireless Communications at Aalborg University and Fellow of the IEEE. He received his Dipl.-Ing and M. Sc. degrees in Communication Engineering from the University of Sts. Cyril and Methodius in Skopje and the Ph.D. degree from Aalborg University in 2005. He has over 300 publications in journals, conference proceedings, and edited books. He holds over 30 patents and patent applications. He received an ERC Consolidator Grant (2015), the Danish Elite Researcher award (2016), IEEE Fred W. Ellersick prize (2016), and IEEE Stephen O. Rice prize (2018). He is featured in the list of Highly Cited Researchers 2018, compiled by Web of Science. His research interests are in the area of wireless communication and communication theory.

• Foreword xvAcknowledgments xixAcronyms xxi1 An Easy Introduction to the Shared Wireless Medium 31.1 How to Build a Simple Model for Wireless Communication 41.1.1 Which Features We Want from the Model 41.1.2 Communication Channel with Collisions 41.1.3 Trade-offs in the Collision Model 71.2 The First Contact 91.2.1 Hierarchy Helps to Establish Contact 91.2.2 Wireless Rendezvous without Help 111.2.3 Rendezvous with Full-Duplex Devices 121.3 Multiple Access with Centralized Control 121.3.1 A Frame for Time Division 131.3.2 Frame Header for Flexible Time Division 141.3.3 A Simple Two-Way System that Works Under the Collision Model 151.3.4 Still Not a Practical TDMA System 181.4 Making TDMA Dynamic 191.4.1 Circuit-Switched versus Packet-Switched Operation 191.4.2 Dynamic Allocation of Resources to Users 201.4.3 Short Control Packets and the Idea of Reservation 221.4.4 Half-Duplex versus Full-Duplex in TDMA 241.5 Chapter Summary 251.6 Further Reading 251.7 Problems and Reflections 262 Random Access: How to Talk in Crowded Dark Room 292.1 Framed ALOHA 302.1.1 Randomization that Maximizes the ALOHA Throughput 322.2 Probing 352.2.1 Combining ALOHA and Probing 392.3 Carrier Sensing 392.3.1 Randomization and Spectrum Sharing 392.3.2 An Idle Slot is Cheap 412.3.3 Feedback to the Transmitter 432.4 Random Access and Multiple Hops 452.4.1 Use of Reservation Packets in Multi-Hop 472.4.2 Multiple Hops and Full-Duplex 472.5 Chapter Summary 482.6 Further Reading 482.7 Problems and Reflections 483 Access Beyond the Collision Model 533.1 Distance Gets into the Model 533.1.1 Communication Degrades as the Distance Increases 533.1.2 How to Make the Result of a Collision Dependent on the Distance 553.2 Simplified Distance Dependence: A Double Disk Model 573.3 Downlink Communication with the Double Disk Model 583.3.1 A Cautious Example of a Design that Reaches the Limits of the Model 613.4 Uplink Communication with the Double Disk Model 623.4.1 Uplink that Uses Multi-Packet Reception 643.4.2 Buffered Collisions for Future Use 643.4.3 Protocols that Use Packet Fractions 663.5 Unwrapping the Packets 683.6 Chapter Summary 693.7 Further Reading 703.8 Problems and Reflections 704 The Networking Cake: Layering and Slicing 754.1 Layering for a One-Way Link 754.1.1 Modules and their Interconnection 754.1.2 Three Important Concepts in Layering 774.1.3 An Example of a Two-Layer System 784.2 Layers and Cross-Layer 794.3 Reliable and Unreliable Service from a Layer 814.4 Black Box Functionality for Different Communication Models 844.5 Standard Layering Models 864.5.1 Connection versus Connectionless 874.5.2 Functionality of the Standard Layers 884.5.3 A Very Brief Look at the Network Layer 894.6 An Alternative Wireless Layering 914.7 Cross-Layer Design for Multiple Hops 924.8 Slicing of the Wireless Communication Resources 944.8.1 Analog, Digital, Sliced 944.8.2 A Primer on Wireless Slicing 964.8.2.1 Orthogonal Wireless Slicing 964.8.2.2 Non-Orthogonal Wireless Slicing 984.9 Chapter Summary 1004.10 Further Reading 1004.11 Problems and Reflections 1005 Packets Under the Looking Glass: Symbols and Noise 1055.1 Compression, Entropy, and Bit 1055.1.1 Obtaining Digital Messages by Compression 1065.1.2 A Bit of Information 1065.2 Baseband Modules of the Communication System 1075.2.1 Mapping Bits to Baseband Symbols under Simplifying Assumptions 1085.2.2 Challenging the Simplifying Assumptions about the Baseband 1095.3 Signal Constellations and Noise 1105.3.1 Constellation Points and Noise Clouds 1105.3.2 Constellations with Limited Average Power 1135.3.3 Beyond the Simple Setup for Symbol Detection 1145.3.4 Signal-to-Noise Ratio (SNR) 1165.4 From Bits to Symbols 1175.4.1 Binary Phase Shift Keying (BPSK) 1175.4.2 Quaternary Phase Shift Keying (QPSK) 1185.4.3 Constellations of Higher Order 1195.4.4 Generalized Mapping to Many Symbols 1225.5 Symbol-Level Interference Models 1235.5.1 Advanced Treatment of Collisions based on a Baseband Model 1245.6 Weak and Strong Signals: New Protocol Possibilities 1265.6.1 Randomization of Power 1275.6.2 Other Goodies from the Baseband Model 1295.7 How to Select the Data Rate 1305.7.1 A Simple Relation between Packet Errors and Distance 1305.7.2 Adaptive Modulation 1325.8 Superposition of Baseband Symbols 1345.8.1 Broadcast and Non-Orthogonal Access 1355.8.2 Unequal Error Protection (UEP) 1375.9 Communication with Unknown Channel Coefficients 1385.10 Chapter Summary 1415.11 Further Reading 1425.12 Problems and Reflections 1426 A Mathematical View on a Communication Channel 1476.1 A Toy Example: The Pigeon Communication Channel 1476.1.1 Specification of a Communication Channel 1496.1.2 Comparison of the Information Carrying Capability of Mathematical Channels 1506.1.3 Assumptions and Notations 1516.2 Analog Channels with Gaussian Noise 1516.2.1 Gaussian Channel 1526.2.2 Other Analog Channels Based on the Gaussian Channel 1526.3 The Channel Definition Depends on Who Knows What 1546.4 Using Analog to Create Digital Communication Channels 1586.4.1 Creating Digital Channels through Gray Mapping 1586.4.2 Creating Digital Channels through Superposition 1616.5 Transmission of Packets over Communication Channels 1636.5.1 Layering Perspective of the Communication Channels 1636.5.2 How to Obtain Throughput that is not Zero 1646.5.3 Asynchronous Packets and Transmission of “Nothing” 1676.5.4 Packet Transmission over a Ternary Channel 1696.6 Chapter Summary 1716.7 Further Reading 1716.8 Problems and Reflections 1727 Coding for Reliable Communication 1777.1 Some Coding Ideas for the Binary Symmetric Channel 1777.1.1 A Channel Based on Repetition Coding 1777.1.2 Channel Based on Repetition Coding with Erasures 1797.1.3 Coding Beyond Repetition 1817.1.4 An Illustrative Comparison of the BSC Based Channels 1827.2 Generalization of the Coding Idea 1837.2.1 Maximum Likelihood (ML) Decoding 1877.3 Linear Block Codes for the Binary Symmetric Channel 1887.4 Coded Modulation as a Layered Subsystem 1927.5 Retransmission as a Supplement to Coding 1947.5.1 Full Packet Retransmission 1957.5.2 Partial Retransmission and Incremental Redundancy 1977.6 Chapter Summary 1997.7 Further Reading 1997.8 Problems and Reflections 1998 Information-Theoretic View on Wireless Channel Capacity 2038.1 It Starts with the Law of Large Numbers 2038.2 A Useful Digression into Source Coding 2048.3 Perfectly Reliable Communication and Channel Capacity 2078.4 Mutual Information and Its Interpretations 2098.4.1 From a Local to a Global Property 2098.4.2 Mutual Information in Some Actual Communication Setups 2118.5 The Gaussian Channel and the Popular Capacity Formula 2148.5.1 The Concept of Entropy in Analog Channels 2148.5.2 The Meaning of “Shannon’s Capacity Formula” 2158.5.3 Simultaneous Usage of Multiple Gaussian Channels 2178.6 Capacity of Fading Channels 2198.6.1 Channel State Information Available at the Transmitter 2198.6.2 Example: Water Filling for Binary Fading 2218.6.3 Water Filling for Continuously Distributed Fading 2228.6.4 Fast Fading and Further Remarks on Channel Knowledge 2238.6.5 Capacity When the Transmitter Does Not Know the Channel 2258.6.5.1 Channel with Binary Inputs and Binary Fading 2258.6.5.2 Channels with Gaussian Noise and Fading 2298.6.6 Channel Estimation and Knowledge 2308.7 Chapter Summary 2328.8 Further Reading 2338.9 Problems and Reflections 2339 Time and Frequency in Wireless Communications 2379.1 Reliable Communication Requires Transmission of Discrete Values 2379.2 Communication Through a Waveform: An Example 2399.3 Enter the Frequency 2429.3.1 Infinitely Long Signals and True Frequency 2429.3.2 Bandwidth and Time-Limited Signals 2459.3.3 Parallel Communication Channels 2479.3.4 How Frequency Affects the Notion of Multiple Access 2489.4 Noise and Interference 2509.4.1 Signal Power and Gaussian White Noise 2509.4.2 Interference between Non-Orthogonal Frequencies 2529.5 Power Spectrum and Fourier Transform 2559.6 Frequency Channels, Finally 2589.6.1 Capacity of a Bandlimited Channel 2599.6.2 Capacity and OFDM Transmission 2619.6.3 Frequency for Multiple Access and Duplexing 2619.7 Code Division and Spread Spectrum 2639.7.1 Sharing Synchronized Resources with Orthogonal Codes 2639.7.2 Why Go Through the Trouble of Spreading? 2659.7.3 Mimicking the Noise and Covert Communication 2689.7.4 Relation to Random Access 2699.8 Chapter Summary 2709.9 Further Reading 2709.10 Problems and Reflections 27010 Space in Wireless Communications 27510.1 Communication Range and Coverage Area 27610.2 The Myth about Frequencies that Propagate Badly in Free Space 27810.3 The World View of an Antenna 28010.3.1 Antenna Directivity 28010.3.2 Directivity Changes the Communication Models 28210.4 Multipath and Shadowing: Space is Rarely Free 28310.5 The Final Missing Link in the Layering Model 28610.6 The Time-Frequency Dynamics of the Radio Channel 28810.6.1 How a Time-Invariant Channel Distorts the Received Signal 28810.6.2 Frequency Selectivity, Multiplexing, and Diversity 29110.6.3 Time-Variant Channel Introduces New Frequencies 29210.6.4 Combined Time-Frequency Dynamics 29510.7 Two Ideas to Deal with Multipath Propagation and Delay Spread 29610.7.1 The Wideband Idea: Spread Spectrum and a RAKE Receiver 29710.7.2 The Narrowband Idea: OFDM and a Guard Interval 29910.8 Statistical Modeling of Wireless Channels 30010.8.1 Fading Models: Rayleigh and Some Others 30110.8.2 Randomness in the Path Loss 30310.9 Reciprocity and How to Use It 30310.10 Chapter Summary 30510.11 Further Reading 30510.12 Problems and Reflections 30511 Using Two, More, or a Massive Number of Antennas 30911.1 Assumptions about the Channel Model and the Antennas 31011.2 Receiving or Transmitting with a Two-Antenna Device 31111.2.1 Receiver with Two Antennas 31111.2.2 Using Two Antennas at a Knowledgeable Transmitter 31311.2.3 Transmit Diversity 31411.3 Introducing MIMO 31511.3.1 Spatial Multiplexing 31711.4 Multiple Antennas for Spatial Division of Multiple Users 31911.4.1 Digital Interference-Free Beams: Zero Forcing 32011.4.2 Other Schemes for Precoding and Digital Beamforming 32211.5 Beamforming and Spectrum Sharing 32511.6 What If the Number of Antennas is Scaled Massively? 32711.6.1 The Base Station Knows the Channels Perfectly 32811.6.2 The Base Station has to Learn the Channels 32911.7 Chapter Summary 33111.8 Further Reading 33111.9 Problems and Reflections 33112 Wireless Beyond a Link: Connections and Networks 33512.1 Wireless Connections with Different Flavors 33512.1.1 Coarse Classification of the Wireless Connections 33512.1.2 The Complex, Multidimensional World of Wireless Connectivity 33712.2 Fundamental Ideas for Providing Wireless Coverage 33912.2.1 Static or Moving Infrastructure 34012.2.2 Cells and a Cellular Network 34112.2.3 Spatial Reuse 34312.2.4 Cells Come in Different Sizes 34512.2.5 Two-Way Coverage and Decoupled Access 34712.3 No Cell is an Island 34812.3.1 Wired and Wireless Backhaul 34812.3.2 Wireless One-Way Relaying and the Half-Duplex Loss 34912.3.3 Wireless Two-Way Relaying: Reclaiming the Half-Duplex Loss 35112.4 Cooperation and Coordination 35512.4.1 Artificial Multipath: Treating the BS as Yet Another Antenna 35512.4.2 Distributing and Networking the MIMO Concept 35712.4.3 Cooperation Through a Wireless Backhaul 35912.5 Dissolving the Cells into Clouds and Fog 36012.5.1 The Unattainable Ideal Coverage 36012.5.2 The Backhaul Links Must Have a Finite Capacity 36212.5.3 Noisy Cooperation with a Finite Backhaul 36312.5.4 Access Through Clouds and Fog 36412.6 Coping with External Interference and Other Questions about the Radio Spectrum 36612.6.1 Oblivious Rather Than Selfish 36612.6.2 License to Control Interference 36712.6.3 Spectrum Sharing and Caring 36912.6.4 Duty Cycling, Sensing, and Hopping 37112.6.5 Beyond the Licensed and Unlicensed and Some Final Words 37212.7 Chapter Summary 37412.8 Further Reading 37412.9 Problems and Reflections 375Bibliography 377Index 381