ABSTRACT
Contents 1.1 Introduction ..................................................................................... 4 1.2 Applications of Wireless Multimedia Sensor Networks....................... 6 1.3 Design and Characteristics of Wireless Multimedia Sensor
Networks.......................................................................................... 7 1.4 Network Architecture...................................................................... 10
1.4.1 Reference Architecture ........................................................... 10 1.4.2 Single-versus Multitier Sensor Deployment............................ 12 1.4.3 Coverage ............................................................................... 13 1.4.4 Internal Organization of a Multimedia Sensor......................... 13
1.5 Application Layer............................................................................ 14 1.5.1 Traffic Classes ........................................................................ 15 1.5.2 Multimedia Encoding Techniques........................................... 16
1.5.2.1 Pixel-Domain Wyner-Ziv Encoder .............................. 18 1.5.2.2 Transform-Domain Wyner-Ziv Encoder ...................... 20
1.5.3 System Software and Middleware........................................... 20 1.5.4 Collaborative In-Network Processing...................................... 22
1.6.1 Transport-Layer Protocols ...................................................... 24
1.6.1.1 TCP/UDP and TCP-Friendly Schemes for WMSNs ....... 24 1.6.1.2 Application-Specific and Nonstandard Protocols ......... 26
1.6.2 Network Layer ....................................................................... 27 1.6.2.1 QoS Routing Based on Network Conditions ............... 27 1.6.2.2 QoS Routing Based on Traffic Classes......................... 28 1.6.2.3 Routing Protocols with Support for Streaming ............ 28
1.6.3 MAC Layer ............................................................................. 29 1.6.3.1 Channel Access Policies ............................................. 29 1.6.3.2 Contention-Based Protocols........................................ 29 1.6.3.3 Contention-Free Single-Channel Protocols .................. 30 1.6.3.4 Contention-Free Multi-Channel Protocols.................... 32 1.6.3.5 Scheduling ................................................................. 33 1.6.3.6 Link-Layer Error Control ............................................. 34
1.6.4 Cross-Layer Protocols............................................................. 35 1.7 Physical Layer................................................................................. 36
1.7.1 Ultra Wideband Communications........................................... 37 1.7.1.1 Ranging Capabilities of UWB...................................... 38 1.7.1.2 Standards Based on UWB........................................... 39 1.7.1.3 Open Research Issues ................................................ 39
1.8 Conclusions.................................................................................... 40 Acknowledgment.................................................................................. 40 References ............................................................................................ 40
Low-cost CMOS cameras, microphones, and sensors have recently become ubiquitously available. This has fostered the development of the so-called wireless multimedia sensor networks (WMSNs), that is, distributed systems composed of wirelessly interconnected devices that can ubiquitously retrieve multimedia content such as video and audio streams, still images, and scalar sensor data from the environment. This chapter discusses the state-of-the-art in algorithms, protocols, and hardware for WMSNs; open research issues are discussed in detail. Architectures for WMSNs are explored, along with their advantages and drawbacks. Existing solutions and open research issues at the application, transport, network, link, and physical layers of the communication stack are investigated, along with possible cross-layer synergies and optimizations.
