Holger Karl is currently assistant professor in the Networking Group (Prof. Adam Wolisz) at the Technical University of Berlin.  His research interests focus on wireless and mobile networks, with a certain emphasis on ad-hoc networks. He has published numerous papers and research articles in international journals (e.g. IEEE, IEE, CPE). Andreas Willig is currently assistant professor at the University of Potsdam. His areas of interest comprise communication networks (wireless LANs, real-time systems and ad-hoc and sensor networks) and performance evaluation.

"…this book represents an authoritative yet open-minded source to acquire a solid understanding of the fundamentals of WSNs.  It is a recommended and enjoy read." (Computing Reviews, March 11, 2008)

• Preface xiiiList of abbreviations xvA guide to the book xxiii1 Introduction 11.1 The vision of Ambient Intelligence 11.2 Application examples 31.3 Types of applications 61.4 Challenges for WSNs 71.4.1 Characteristic requirements 71.4.2 Required mechanisms 91.5 Why are sensor networks different? 101.5.1 Mobile ad hoc networks and wireless sensor networks 101.5.2 Fieldbuses and wireless sensor networks 121.6 Enabling technologies for wireless sensor networks 13Part I Architectures 152 Single-node architecture 172.1 Hardware components 182.1.1 Sensor node hardware overview 182.1.2 Controller 192.1.3 Memory 212.1.4 Communication device 212.1.5 Sensors and actuators 312.1.6 Power supply of sensor nodes 322.2 Energy consumption of sensor nodes 362.2.1 Operation states with different power consumption 362.2.2 Microcontroller energy consumption 382.2.3 Memory 392.2.4 Radio transceivers 402.2.5 Relationship between computation and communication 442.2.6 Power consumption of sensor and actuators 442.3 Operating systems and execution environments 452.3.1 Embedded operating systems 452.3.2 Programming paradigms and application programming interfaces 452.3.3 Structure of operating system and protocol stack 472.3.4 Dynamic energy and power management 482.3.5 Case Study: TinyOS and nesC 502.3.6 Other examples 532.4 Some examples of sensor nodes 542.4.1 The “Mica Mote” family 542.4.2 EYES nodes 542.4.3 BTnodes 542.4.4 Scatterweb 542.4.5 Commercial solutions 552.5 Conclusion 563 Network architecture 593.1 Sensor network scenarios 603.1.1 Types of sources and sinks 603.1.2 Single-hop versus multihop networks 603.1.3 Multiple sinks and sources 623.1.4 Three types of mobility 623.2 Optimization goals and figures of merit 633.2.1 Quality of service 643.2.2 Energy efficiency 653.2.3 Scalability 663.2.4 Robustness 673.3 Design principles for WSNs 673.3.1 Distributed organization 673.3.2 In-network processing 673.3.3 Adaptive fidelity and accuracy 703.3.4 Data centricity 703.3.5 Exploit location information 733.3.6 Exploit activity patterns 733.3.7 Exploit heterogeneity 733.3.8 Component-based protocol stacks and cross-layer optimization 743.4 Service interfaces of WSNs 743.4.1 Structuring application/protocol stack interfaces 743.4.2 Expressibility requirements for WSN service interfaces 763.4.3 Discussion 773.5 Gateway concepts 783.5.1 The need for gateways 783.5.2 WSN to Internet communication 793.5.3 Internet to WSN communication 803.5.4 WSN tunneling 813.6 Conclusion 81Part II Communication Protocols 834 Physical layer 854.1 Introduction 854.2 Wireless channel and communication fundamentals 864.2.1 Frequency allocation 864.2.2 Modulation and demodulation 884.2.3 Wave propagation effects and noise 904.2.4 Channel models 964.2.5 Spread-spectrum communications 984.2.6 Packet transmission and synchronization 1004.2.7 Quality of wireless channels and measures for improvement 1024.3 Physical layer and transceiver design considerations in WSNs 1034.3.1 Energy usage profile 1034.3.2 Choice of modulation scheme 1044.3.3 Dynamic modulation scaling 1084.3.4 Antenna considerations 1084.4 Further reading 1095 MAC protocols 1115.1 Fundamentals of (wireless) MAC protocols 1125.1.1 Requirements and design constraints for wireless MAC protocols 1125.1.2 Important classes of MAC protocols 1145.1.3 MAC protocols for wireless sensor networks 1195.2 Low duty cycle protocols and wakeup concepts 1205.2.1 Sparse topology and energy management (STEM) 1215.2.2 S-mac 1235.2.3 The mediation device protocol 1265.2.4 Wakeup radio concepts 1275.2.5 Further reading 1285.3 Contention-based protocols 1295.3.1 CSMA protocols 1295.3.2 PAMAS 1315.3.3 Further solutions 1325.4 Schedule-based protocols 1335.4.1 LEACH 1335.4.2 SMACS 1355.4.3 Traffic-adaptive medium access protocol (TRAMA) 1375.4.4 Further solutions 1395.5 The IEEE 802.15.4 MAC protocol 1395.5.1 Network architecture and types/roles of nodes 1405.5.2 Superframe structure 1415.5.3 GTS management 1415.5.4 Data transfer procedures 1425.5.5 Slotted CSMA-CA protocol 1425.5.6 Nonbeaconed mode 1445.5.7 Further reading 1455.6 How about IEEE 802.11 and bluetooth? 1455.7 Further reading 1465.8 Conclusion 1486 Link-layer protocols 1496.1 Fundamentals: tasks and requirements 1506.2 Error control 1516.2.1 Causes and characteristics of transmission errors 1516.2.2 ARQ techniques 1526.2.3 FEC techniques 1586.2.4 Hybrid schemes 1636.2.5 Power control 1656.2.6 Further mechanisms to combat errors 1666.2.7 Error control: summary 1676.3 Framing 1676.3.1 Adaptive schemes 1706.3.2 Intermediate checksum schemes 1726.3.3 Combining packet-size optimization and FEC 1736.3.4 Treatment of frame headers 1746.3.5 Framing: summary 1746.4 Link management 1746.4.1 Link-quality characteristics 1756.4.2 Link-quality estimation 1776.5 Summary 1797 Naming and addressing 1817.1 Fundamentals 1827.1.1 Use of addresses and names in (sensor) networks 1827.1.2 Address management tasks 1837.1.3 Uniqueness of addresses 1847.1.4 Address allocation and assignment 1847.1.5 Addressing overhead 1857.2 Address and name management in wireless sensor networks 1867.3 Assignment of MAC addresses 1867.3.1 Distributed assignment of networkwide addresses 1877.4 Distributed assignment of locally unique addresses 1897.4.1 Address assignment algorithm 1897.4.2 Address selection and representation 1917.4.3 Further schemes 1947.5 Content-based and geographic addressing 1947.5.1 Content-based addressing 1947.5.2 Geographic addressing 1987.6 Summary 1988 Time synchronization 2018.1 Introduction to the time synchronization problem 2018.1.1 The need for time synchronization in wireless sensor networks 2028.1.2 Node clocks and the problem of accuracy 2038.1.3 Properties and structure of time synchronization algorithms 2048.1.4 Time synchronization in wireless sensor networks 2068.2 Protocols based on sender/receiver synchronization 2078.2.1 Lightweight time synchronization protocol (LTS) 2078.2.2 How to increase accuracy and estimate drift 2128.2.3 Timing-sync protocol for sensor networks (TPSN) 2148.3 Protocols based on receiver/receiver synchronization 2178.3.1 Reference broadcast synchronization (RBS) 2178.3.2 Hierarchy referencing time synchronization (HRTS) 2238.4 Further reading 2269 Localization and positioning 2319.1 Properties of localization and positioning procedures 2329.2 Possible approaches 2339.2.1 Proximity 2339.2.2 Trilateration and triangulation 2349.2.3 Scene analysis 2379.3 Mathematical basics for the lateration problem 2379.3.1 Solution with three anchors and correct distance values 2389.3.2 Solving with distance errors 2389.4 Single-hop localization 2409.4.1 Active Badge 2409.4.2 Active office 2409.4.3 Radar 2409.4.4 Cricket 2419.4.5 Overlapping connectivity 2419.4.6 Approximate point in triangle 2429.4.7 Using angle of arrival information 2439.5 Positioning in multihop environments 2439.5.1 Connectivity in a multihop network 2449.5.2 Multihop range estimation 2449.5.3 Iterative and collaborative multilateration 2459.5.4 Probabilistic positioning description and propagation 2479.6 Impact of anchor placement 2479.7 Further reading 2489.8 Conclusion 24910 Topology control 25110.1 Motivation and basic ideas 25110.1.1 Options for topology control 25210.1.2 Aspects of topology-control algorithms 25410.2 Controlling topology in flat networks – Power control 25610.2.1 Some complexity results 25610.2.2 Are there magic numbers? – bounds on critical parameters 25710.2.3 Some example constructions and protocols 25910.2.4 Further reading on flat topology control 26510.3 Hierarchical networks by dominating sets 26610.3.1 Motivation and definition 26610.3.2 A hardness result 26610.3.3 Some ideas from centralized algorithms 26710.3.4 Some distributed approximations 27010.3.5 Further reading 27310.4 Hierarchical networks by clustering 27410.4.1 Definition of clusters 27410.4.2 A basic idea to construct independent sets 27710.4.3 A generalization and some performance insights 27810.4.4 Connecting clusters 27810.4.5 Rotating clusterheads 27910.4.6 Some more algorithm examples 28010.4.7 Multihop clusters 28110.4.8 Multiple layers of clustering 28310.4.9 Passive clustering 28410.4.10 Further reading 28410.5 Combining hierarchical topologies and power control 28510.5.1 Pilot-based power control 28510.5.2 Ad hoc Network Design Algorithm (ANDA) 28510.5.3 Clusterpow 28610.6 Adaptive node activity 28610.6.1 Geographic Adaptive Fidelity (GAF) 28610.6.2 Adaptive Self-Configuring sEnsor Networks’ Topologies (ASCENT) 28710.6.3 Turning off nodes on the basis of sensing coverage 28810.7 Conclusions 28811 Routing protocols 28911.1 The many faces of forwarding and routing 28911.2 Gossiping and agent-based unicast forwarding 29211.2.1 Basic idea 29211.2.2 Randomized forwarding 29211.2.3 Random walks 29311.2.4 Further reading 29411.3 Energy-efficient unicast 29511.3.1 Overview 29511.3.2 Some example unicast protocols 29711.3.3 Further reading 30111.3.4 Multipath unicast routing 30111.3.5 Further reading 30411.4 Broadcast and multicast 30511.4.1 Overview 30511.4.2 Source-based tree protocols 30811.4.3 Shared, core-based tree protocols 31411.4.4 Mesh-based protocols 31411.4.5 Further reading on broadcast and multicast 31511.5 Geographic routing 31611.5.1 Basics of position-based routing 31611.5.2 Geocasting 32311.5.3 Further reading on geographic routing 32611.6 Mobile nodes 32811.6.1 Mobile sinks 32811.6.2 Mobile data collectors 32811.6.3 Mobile regions 32911.7 Conclusions 32912 Data-centric and content-based networking 33112.1 Introduction 33112.1.1 The publish/subscribe interaction paradigm 33112.1.2 Addressing data 33212.1.3 Implementation options 33312.1.4 Distribution versus gathering of data – In-network processing 33412.2 Data-centric routing 33512.2.1 One-shot interactions 33512.2.2 Repeated interactions 33712.2.3 Further reading 34012.3 Data aggregation 34112.3.1 Overview 34112.3.2 A database interface to describe aggregation operations 34212.3.3 Categories of aggregation operations 34312.3.4 Placement of aggregation points 34512.3.5 When to stop waiting for more data 34512.3.6 Aggregation as an optimization problem 34712.3.7 Broadcasting an aggregated value 34712.3.8 Information-directed routing and aggregation 35012.3.9 Some further examples 35212.3.10 Further reading on data aggregation 35512.4 Data-centric storage 35512.5 Conclusions 35713 Transport layer and quality of service 35913.1 The transport layer and QoS in wireless sensor networks 35913.1.1 Quality of service/reliability 36013.1.2 Transport protocols 36113.2 Coverage and deployment 36213.2.1 Sensing models 36213.2.2 Coverage measures 36413.2.3 Uniform random deployments: Poisson point processes 36513.2.4 Coverage of random deployments: Boolean sensing model 36613.2.5 Coverage of random deployments: general sensing model 36813.2.6 Coverage determination 36913.2.7 Coverage of grid deployments 37413.2.8 Further reading 37513.3 Reliable data transport 37613.3.1 Reliability requirements in sensor networks 37713.4 Single packet delivery 37813.4.1 Using a single path 37913.4.2 Using multiple paths 38413.4.3 Multiple receivers 38813.4.4 Summary 38913.5 Block delivery 38913.5.1 PSFQ: block delivery in the sink-to-sensors case 38913.5.2 RMST: block delivery in the sensors-to-sink case 39513.5.3 What about TCP? 39713.5.4 Further reading 39913.6 Congestion control and rate control 40013.6.1 Congestion situations in sensor networks 40013.6.2 Mechanisms for congestion detection and handling 40213.6.3 Protocols with rate control 40313.6.4 The CODA congestion-control framework 40813.6.5 Further reading 41114 Advanced application support 41314.1 Advanced in-network processing 41314.1.1 Going beyond mere aggregation of data 41314.1.2 Distributed signal processing 41414.1.3 Distributed source coding 41614.1.4 Network coding 42014.1.5 Further issues 42114.2 Security 42214.2.1 Fundamentals 42214.2.2 Security considerations in wireless sensor networks 42314.2.3 Denial-of-service attacks 42314.2.4 Further reading 42514.3 Application-specific support 42514.3.1 Target detection and tracking 42614.3.2 Contour/edge detection 42914.3.3 Field sampling 432Bibliography 437Index 481

Holger Karl is currently assistant professor in the Networking Group (Prof. Adam Wolisz) at the Technical University of Berlin.  His research interests focus on wireless and mobile networks, with a certain emphasis on ad-hoc networks. He has published numerous papers and research articles in international journals (e.g. IEEE, IEE, CPE). Andreas Willig is currently assistant professor at the University of Potsdam. His areas of interest comprise communication networks (wireless LANs, real-time systems and ad-hoc and sensor networks) and performance evaluation.

"…this book represents an authoritative yet open-minded source to acquire a solid understanding of the fundamentals of WSNs.  It is a recommended and enjoy read." (Computing Reviews, March 11, 2008)

• Preface xiiiList of abbreviations xvA guide to the book xxiii1 Introduction 11.1 The vision of Ambient Intelligence 11.2 Application examples 31.3 Types of applications 61.4 Challenges for WSNs 71.4.1 Characteristic requirements 71.4.2 Required mechanisms 91.5 Why are sensor networks different? 101.5.1 Mobile ad hoc networks and wireless sensor networks 101.5.2 Fieldbuses and wireless sensor networks 121.6 Enabling technologies for wireless sensor networks 13Part I Architectures 152 Single-node architecture 172.1 Hardware components 182.1.1 Sensor node hardware overview 182.1.2 Controller 192.1.3 Memory 212.1.4 Communication device 212.1.5 Sensors and actuators 312.1.6 Power supply of sensor nodes 322.2 Energy consumption of sensor nodes 362.2.1 Operation states with different power consumption 362.2.2 Microcontroller energy consumption 382.2.3 Memory 392.2.4 Radio transceivers 402.2.5 Relationship between computation and communication 442.2.6 Power consumption of sensor and actuators 442.3 Operating systems and execution environments 452.3.1 Embedded operating systems 452.3.2 Programming paradigms and application programming interfaces 452.3.3 Structure of operating system and protocol stack 472.3.4 Dynamic energy and power management 482.3.5 Case Study: TinyOS and nesC 502.3.6 Other examples 532.4 Some examples of sensor nodes 542.4.1 The “Mica Mote” family 542.4.2 EYES nodes 542.4.3 BTnodes 542.4.4 Scatterweb 542.4.5 Commercial solutions 552.5 Conclusion 563 Network architecture 593.1 Sensor network scenarios 603.1.1 Types of sources and sinks 603.1.2 Single-hop versus multihop networks 603.1.3 Multiple sinks and sources 623.1.4 Three types of mobility 623.2 Optimization goals and figures of merit 633.2.1 Quality of service 643.2.2 Energy efficiency 653.2.3 Scalability 663.2.4 Robustness 673.3 Design principles for WSNs 673.3.1 Distributed organization 673.3.2 In-network processing 673.3.3 Adaptive fidelity and accuracy 703.3.4 Data centricity 703.3.5 Exploit location information 733.3.6 Exploit activity patterns 733.3.7 Exploit heterogeneity 733.3.8 Component-based protocol stacks and cross-layer optimization 743.4 Service interfaces of WSNs 743.4.1 Structuring application/protocol stack interfaces 743.4.2 Expressibility requirements for WSN service interfaces 763.4.3 Discussion 773.5 Gateway concepts 783.5.1 The need for gateways 783.5.2 WSN to Internet communication 793.5.3 Internet to WSN communication 803.5.4 WSN tunneling 813.6 Conclusion 81Part II Communication Protocols 834 Physical layer 854.1 Introduction 854.2 Wireless channel and communication fundamentals 864.2.1 Frequency allocation 864.2.2 Modulation and demodulation 884.2.3 Wave propagation effects and noise 904.2.4 Channel models 964.2.5 Spread-spectrum communications 984.2.6 Packet transmission and synchronization 1004.2.7 Quality of wireless channels and measures for improvement 1024.3 Physical layer and transceiver design considerations in WSNs 1034.3.1 Energy usage profile 1034.3.2 Choice of modulation scheme 1044.3.3 Dynamic modulation scaling 1084.3.4 Antenna considerations 1084.4 Further reading 1095 MAC protocols 1115.1 Fundamentals of (wireless) MAC protocols 1125.1.1 Requirements and design constraints for wireless MAC protocols 1125.1.2 Important classes of MAC protocols 1145.1.3 MAC protocols for wireless sensor networks 1195.2 Low duty cycle protocols and wakeup concepts 1205.2.1 Sparse topology and energy management (STEM) 1215.2.2 S-mac 1235.2.3 The mediation device protocol 1265.2.4 Wakeup radio concepts 1275.2.5 Further reading 1285.3 Contention-based protocols 1295.3.1 CSMA protocols 1295.3.2 PAMAS 1315.3.3 Further solutions 1325.4 Schedule-based protocols 1335.4.1 LEACH 1335.4.2 SMACS 1355.4.3 Traffic-adaptive medium access protocol (TRAMA) 1375.4.4 Further solutions 1395.5 The IEEE 802.15.4 MAC protocol 1395.5.1 Network architecture and types/roles of nodes 1405.5.2 Superframe structure 1415.5.3 GTS management 1415.5.4 Data transfer procedures 1425.5.5 Slotted CSMA-CA protocol 1425.5.6 Nonbeaconed mode 1445.5.7 Further reading 1455.6 How about IEEE 802.11 and bluetooth? 1455.7 Further reading 1465.8 Conclusion 1486 Link-layer protocols 1496.1 Fundamentals: tasks and requirements 1506.2 Error control 1516.2.1 Causes and characteristics of transmission errors 1516.2.2 ARQ techniques 1526.2.3 FEC techniques 1586.2.4 Hybrid schemes 1636.2.5 Power control 1656.2.6 Further mechanisms to combat errors 1666.2.7 Error control: summary 1676.3 Framing 1676.3.1 Adaptive schemes 1706.3.2 Intermediate checksum schemes 1726.3.3 Combining packet-size optimization and FEC 1736.3.4 Treatment of frame headers 1746.3.5 Framing: summary 1746.4 Link management 1746.4.1 Link-quality characteristics 1756.4.2 Link-quality estimation 1776.5 Summary 1797 Naming and addressing 1817.1 Fundamentals 1827.1.1 Use of addresses and names in (sensor) networks 1827.1.2 Address management tasks 1837.1.3 Uniqueness of addresses 1847.1.4 Address allocation and assignment 1847.1.5 Addressing overhead 1857.2 Address and name management in wireless sensor networks 1867.3 Assignment of MAC addresses 1867.3.1 Distributed assignment of networkwide addresses 1877.4 Distributed assignment of locally unique addresses 1897.4.1 Address assignment algorithm 1897.4.2 Address selection and representation 1917.4.3 Further schemes 1947.5 Content-based and geographic addressing 1947.5.1 Content-based addressing 1947.5.2 Geographic addressing 1987.6 Summary 1988 Time synchronization 2018.1 Introduction to the time synchronization problem 2018.1.1 The need for time synchronization in wireless sensor networks 2028.1.2 Node clocks and the problem of accuracy 2038.1.3 Properties and structure of time synchronization algorithms 2048.1.4 Time synchronization in wireless sensor networks 2068.2 Protocols based on sender/receiver synchronization 2078.2.1 Lightweight time synchronization protocol (LTS) 2078.2.2 How to increase accuracy and estimate drift 2128.2.3 Timing-sync protocol for sensor networks (TPSN) 2148.3 Protocols based on receiver/receiver synchronization 2178.3.1 Reference broadcast synchronization (RBS) 2178.3.2 Hierarchy referencing time synchronization (HRTS) 2238.4 Further reading 2269 Localization and positioning 2319.1 Properties of localization and positioning procedures 2329.2 Possible approaches 2339.2.1 Proximity 2339.2.2 Trilateration and triangulation 2349.2.3 Scene analysis 2379.3 Mathematical basics for the lateration problem 2379.3.1 Solution with three anchors and correct distance values 2389.3.2 Solving with distance errors 2389.4 Single-hop localization 2409.4.1 Active Badge 2409.4.2 Active office 2409.4.3 Radar 2409.4.4 Cricket 2419.4.5 Overlapping connectivity 2419.4.6 Approximate point in triangle 2429.4.7 Using angle of arrival information 2439.5 Positioning in multihop environments 2439.5.1 Connectivity in a multihop network 2449.5.2 Multihop range estimation 2449.5.3 Iterative and collaborative multilateration 2459.5.4 Probabilistic positioning description and propagation 2479.6 Impact of anchor placement 2479.7 Further reading 2489.8 Conclusion 24910 Topology control 25110.1 Motivation and basic ideas 25110.1.1 Options for topology control 25210.1.2 Aspects of topology-control algorithms 25410.2 Controlling topology in flat networks – Power control 25610.2.1 Some complexity results 25610.2.2 Are there magic numbers? – bounds on critical parameters 25710.2.3 Some example constructions and protocols 25910.2.4 Further reading on flat topology control 26510.3 Hierarchical networks by dominating sets 26610.3.1 Motivation and definition 26610.3.2 A hardness result 26610.3.3 Some ideas from centralized algorithms 26710.3.4 Some distributed approximations 27010.3.5 Further reading 27310.4 Hierarchical networks by clustering 27410.4.1 Definition of clusters 27410.4.2 A basic idea to construct independent sets 27710.4.3 A generalization and some performance insights 27810.4.4 Connecting clusters 27810.4.5 Rotating clusterheads 27910.4.6 Some more algorithm examples 28010.4.7 Multihop clusters 28110.4.8 Multiple layers of clustering 28310.4.9 Passive clustering 28410.4.10 Further reading 28410.5 Combining hierarchical topologies and power control 28510.5.1 Pilot-based power control 28510.5.2 Ad hoc Network Design Algorithm (ANDA) 28510.5.3 Clusterpow 28610.6 Adaptive node activity 28610.6.1 Geographic Adaptive Fidelity (GAF) 28610.6.2 Adaptive Self-Configuring sEnsor Networks’ Topologies (ASCENT) 28710.6.3 Turning off nodes on the basis of sensing coverage 28810.7 Conclusions 28811 Routing protocols 28911.1 The many faces of forwarding and routing 28911.2 Gossiping and agent-based unicast forwarding 29211.2.1 Basic idea 29211.2.2 Randomized forwarding 29211.2.3 Random walks 29311.2.4 Further reading 29411.3 Energy-efficient unicast 29511.3.1 Overview 29511.3.2 Some example unicast protocols 29711.3.3 Further reading 30111.3.4 Multipath unicast routing 30111.3.5 Further reading 30411.4 Broadcast and multicast 30511.4.1 Overview 30511.4.2 Source-based tree protocols 30811.4.3 Shared, core-based tree protocols 31411.4.4 Mesh-based protocols 31411.4.5 Further reading on broadcast and multicast 31511.5 Geographic routing 31611.5.1 Basics of position-based routing 31611.5.2 Geocasting 32311.5.3 Further reading on geographic routing 32611.6 Mobile nodes 32811.6.1 Mobile sinks 32811.6.2 Mobile data collectors 32811.6.3 Mobile regions 32911.7 Conclusions 32912 Data-centric and content-based networking 33112.1 Introduction 33112.1.1 The publish/subscribe interaction paradigm 33112.1.2 Addressing data 33212.1.3 Implementation options 33312.1.4 Distribution versus gathering of data – In-network processing 33412.2 Data-centric routing 33512.2.1 One-shot interactions 33512.2.2 Repeated interactions 33712.2.3 Further reading 34012.3 Data aggregation 34112.3.1 Overview 34112.3.2 A database interface to describe aggregation operations 34212.3.3 Categories of aggregation operations 34312.3.4 Placement of aggregation points 34512.3.5 When to stop waiting for more data 34512.3.6 Aggregation as an optimization problem 34712.3.7 Broadcasting an aggregated value 34712.3.8 Information-directed routing and aggregation 35012.3.9 Some further examples 35212.3.10 Further reading on data aggregation 35512.4 Data-centric storage 35512.5 Conclusions 35713 Transport layer and quality of service 35913.1 The transport layer and QoS in wireless sensor networks 35913.1.1 Quality of service/reliability 36013.1.2 Transport protocols 36113.2 Coverage and deployment 36213.2.1 Sensing models 36213.2.2 Coverage measures 36413.2.3 Uniform random deployments: Poisson point processes 36513.2.4 Coverage of random deployments: Boolean sensing model 36613.2.5 Coverage of random deployments: general sensing model 36813.2.6 Coverage determination 36913.2.7 Coverage of grid deployments 37413.2.8 Further reading 37513.3 Reliable data transport 37613.3.1 Reliability requirements in sensor networks 37713.4 Single packet delivery 37813.4.1 Using a single path 37913.4.2 Using multiple paths 38413.4.3 Multiple receivers 38813.4.4 Summary 38913.5 Block delivery 38913.5.1 PSFQ: block delivery in the sink-to-sensors case 38913.5.2 RMST: block delivery in the sensors-to-sink case 39513.5.3 What about TCP? 39713.5.4 Further reading 39913.6 Congestion control and rate control 40013.6.1 Congestion situations in sensor networks 40013.6.2 Mechanisms for congestion detection and handling 40213.6.3 Protocols with rate control 40313.6.4 The CODA congestion-control framework 40813.6.5 Further reading 41114 Advanced application support 41314.1 Advanced in-network processing 41314.1.1 Going beyond mere aggregation of data 41314.1.2 Distributed signal processing 41414.1.3 Distributed source coding 41614.1.4 Network coding 42014.1.5 Further issues 42114.2 Security 42214.2.1 Fundamentals 42214.2.2 Security considerations in wireless sensor networks 42314.2.3 Denial-of-service attacks 42314.2.4 Further reading 42514.3 Application-specific support 42514.3.1 Target detection and tracking 42614.3.2 Contour/edge detection 42914.3.3 Field sampling 432Bibliography 437Index 481