A Survey on Wireless Multimedia Sensor Networks

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A Survey on Wireless Multimedia Sensor Networks

• Present by Yuyan Xue _at_ UNL

Based on Akyildiz, et al., "A Survey on Wireless
Multimedia Sensor Networks", to be appeared on
Computer Networks Journal, March 2007
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Outline

• Introduction to WMSN
• Deploying WMSN
• Layered Research Issues (Application, Transport
  and Network)
• Cross-layer and Other Research Issues

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Definition

• Networks of wirelessly interconnected devices
  that allow retrieving video and audio streams,
  still images, and scalar sensor data.

• Be able to store, process in real-time, correlate
  and fuse multimedia data originated from
  heterogeneous sources.

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Reference Architecture of WMSN
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New Applications

• Storage and Retrieval of Interesting Activities-
  e.g., IrisNet93. (2004)
• Traffic congestion avoidance, traffic.
  enforcement and control systems.
• Smart parking advice system29. (2005)
• Automated Assistance for the elderly and family
  monitors106. (2005)
• Habitat monitoring- e.g.,sandbar evolution.58
  (2004)
• Manufacturing process control for semiconductor
  chip, food or pharmaceutical products.

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Advantages

• Enlarging the Views
• Provide multiple disparate viewpoints to overcome
  occlusion effects
• Enhancing the Views
• Redundancy provides enhanced quality
• Enabling Multi-resolution Views
• Heterogeneous media streams with different
  granularity can be acquired from the same point
  of view

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• Introduction to WMSN
• Deploying WMSN
• Layered Research Issues
• Cross-layer and Other Research Issues

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Design Considerations

• Application-specific QoS requirements
• Snapshot and Streaming multimedia
• Flexible architecture to support heterogeneous
  applications
• Multimedia source coding
• intra-frame/inter-frame
• distributed source coding
• Multimedia in-network processing
• Multimedia coverage model development
• Power consumption

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Enabling Hardware Platforms

• Low resolution imaging motes
• Cyclops Module (CMOS cam- MICA)
  http//www.engineer.ucla.edu/news/2006/cyclops.htm
  l
• CMUcam 3(software compression)
• 32-bit processor V.S. 8-bit processor
• Medium-resolution imaging motes based on the
  Stargate platform
• Developed by Intel and Crossbow
• Imote 2

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Energy Harvesting

• Photovoltaic cells coupled with supercapacitors
  and rechargeable batteries
• Generate energy from background radio signals
  (0.26 µW/cm2 v.s. 100 µW/cm2)
• Vibrational magnetic power generators based on
  moving magnets or coils (10µW/cm2 )

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Examples of Deployed WMSN

• SensEye
• Three tasks
• object detection, recognition and tracking.
• Objective
• Demonstrate a camera sensor network
  containing heterogeneous elements provides
  numerous benefits over traditional homogeneous
  sensor networks.

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Examples of Deployed WMSN

• Broadband and Wireless Networking Laboratory, GIT
• Three different types of multimedia sensors
• Low-end imaging sensors,
• Medium-quality webcam-based multimedia sensors,
• High resolution Pan-tilt cameras mounted on
  Acroname GARCIA mobile robots.

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Example of Software Platform to Deploy
Heterogeneous Services on WMSNs

• IrisNet (Internet-scale Resource-Intensive Sensor
  Network Services)
• Developed by Intel Research Pittsburgh
  (http//www.intel-iris.net/research.html)
• Allows users to perform Google-like queries to
  video sensors and other data.
• The user views the sensor network as a single
  unit that can be queried through a high-level
  language.

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IrisNet Cont.

• Different sensing services are run simultaneously
  on the architecture.
• Sensing agents (SA) and Organizing agents(OA)
• SA can execute services oriented data sensing by
  software filters (called senselets). After
  senselet processing, the distilled information is
  sent to a nearby OA.
• OAs is responsible for collecting data and
  organizes the information in a distributed
  database to answer the class of relevant queries.
  (OpenDHT?)
• Sensor data is represented in XML, which allows
  easy organization of hierarchical data.

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• Introduction to WMSN
• Deploying WMSN
• Layered Research Issues
• Cross-layer and Other Research Issues

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Application Layer

• The services offered by the application layer
  include
• Providing traffic management and admission
  control functionalities
• Performing source coding according to application
  requirements and hardware constraints, by using
  advanced multimedia encoding techniques
• Developing flexible OS and Middleware to make
  functional abstractions and information gathered
  by the scalar and multimedia sensors available
  to higher layer applications

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Traffic Management and Admission Control

• Tasks
• Prevent applications from establishing data flows
  when the network resources needed are not
  available
• Traffic classes - provide differentiated service
  between real-time and delay-tolerant
  applications, and loss-tolerant and
  loss-intolerant applications.
• Related work
• An application admission control algorithm is
  proposed whose objective is to maximize the
  network lifetime subject to bandwidth and
  reliability constraints97.(2003)
• An application admission control method is
  proposed to determine admissions based on the
  added energy load and application rewards28.
  (2003)

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Multimedia Encoding Techniques

• Tasks
• High compression efficiency
• Low complexity on node end
• Robust and Error resiliency
• Related work
• Intra-frame and Inter-frame compression
• Distributed source coding WynerZiv coding
  technology (lossy compression at node end and
  achieve performance comparable to inter-frame
  encoding with complexity at sink end)13(2004)

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Transport Layer

• TCP or UDP?
• For real-time applications like streaming media,
  UDP seems preferred over TCP
• Effect of dropping packets in UDP
• Support for traffic heterogeneity
• TCP with appropriate modifications is preferable
  over UDP for WMSNs, if standardized protocols are
  to be used.

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Problems with TCP

• Effect of jitter induced by TCP
• Applying TCP Friendly Rate Control (TFRC) style
  protocol in WMSN 92. (2001)
• Congestion control algorithms need to be tuned
  for immediate response and yet avoid oscillations
  of data rate
• Overhead of the reliability mechanism in TCP
• Distributed TCP Caching (DTC) 43 (2004)
  overcomes these problems by caching TCP segments
  inside the sensor network and by local
  retransmission of TCP segments.

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Problems with TCP (cont.)

• Distinguish packet loss due to bad channel
  conditions and network congestion
• ARC - the Analytical Rate Control scheme for
  real-time traffic in wireless networks(2004)
• Package reordering due to multi-path
• Information that cannot be used in the proper
  sequence becomes redundant, thus stressing on the
  need for transport layer packet reordering.

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Non-Standard Protocols

• Focusing on reliability
• Reliable Multi-Segment Transport (RMST)
  119(2004) or the Pump Slowly Fetch
  Quickly(PSFQ) protocol 127(2005)
• Loss intolerant packets are separated and ensured
  to be successfully transmitted
• Loss intolerant packets are buffered at
  intermediate nodes, allowing for faster
  retransmission in case of packet loss.
• other packets are transmitted in UDP manner
• No congestion avoidance
• Event-to-Sink Reliable Transport (ESRT) protocol
  17(2005)
• Not best effort but reliable requirement based
  rate control
• Congestion detection and avoidance

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Using Multiple Paths

• Regulating streaming through multiple TCP
  connections 94. (2005)
• Sender send the desired streaming rate and the
  allowed throughput reduction to the receiver.
• Receiver measures the actual throughput, controls
  the rate within the allowed bounds by using
  multiple TCP connections and dynamically changing
  its TCP window size for each connection.
• Spliting a large burst of data into several
  smaller bursts
• Multi-flow Real-time Transport Protocol (MRTP)
  79. (2006)
• Allows the sink to regulate multiple sources
  associated with a single event
• COngestion Detection and Avoidance (CODA)
  protocol 128. (2003)

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Network Layer

• Classification of Existing Routing Protocols

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• Introduction to WMSN
• Deploying WMSN
• Layered Research Issues
• Cross-layer and Other Research Issues

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Cross-layer Design

• Why not layered Design?
• Redundancy for service interface
• Functions handled at different layers are highly
  coupled.
• Scheduling with rate allocation (MACRouting)
• Routing and power control (capacity based on
  transmission power)

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Other Research Issues

• Coordination of Sensing and Actuation
• Network Synchronization
• Inter-media synchronization
• Localization
• Network security

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Recommended Reading

• Energy harvesting96
• Deploying hardware and software6993
• In-network Processing137
• Localization techniques for WMSNs111
• Comprehensive surveys of the major routing
  schemes in WSN19
• Crosslayer Design112