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Real-time Multimedia Monitoring in Large-Scale Wireless Multimedia Sensor
Networks: Research Challenges Joint work by:M.Cesana, A.Redondi – Politecnico di MilanoN. Tiglao, A. Grilo – INESC-ID/INOV/ISTJ. M. Barcelo-Ordinas, M. Alaei – Universitat Politecnica de CatalunyaP. Todorova – Fraunhofer FOKUS
MWMSN Project
Multi-tier Wireless Multimedia Sensor Networks Goal: To enable support for enhanced monitoring and tracking applications through multimedia visual/audio wireless sensor nodes
2NGI 2012, Karlskrona, Sweden
Outline
Introduction Real-time multimedia monitoring applications Efficient delivery of visual data in WMSNsMAC Layer Network Layer Transport Layer
Research challenges and final discussion
3NGI 2012, Karlskrona, Sweden
Introduction
WSN equipped with multimedia sensors givebirth to WMSN.
They enable a new class of monitoringapplications, but demanding in terms of: computational resources energy resources
Need for innovative solutions: combination/optimization techniques atthe different layers of the protocol stack
4NGI 2012, Karlskrona, Sweden
Real-Time Multimedia Monitoring
Supervised monitoring (Image/Video-based) Delivery of compressed image/video flows,analyzed by a human operator
Low bitrate achievable with complex encoders(e.g. H.264/AVC), not supported by WMSN
Suitable solutions: Object-based approaches,Distributed Video Coding
Challenge: Successful implementation of these techniques
5NGI 2012, Karlskrona, Sweden
Real-Time Multimedia Monitoring
Unsupervised monitoring (Feature-based) Use visual features to describe the underlying pixelcontent
Suitable for a broad range of monitoring tasks(e.g., object recognition, face detection…)
Main challenges: Coding of visual features Low-complexity feature extraction algorithms Rate-accuracy models for resources allocation
6NGI 2012, Karlskrona, Sweden
MAC Layer
Main requirements for video streamingover WMSN: Steady-flow of information Delay-bounded delivery of packets
As a consequence, the MAC layer has to: support reliable communication be QoS-aware save as much energy as possible
7NGI 2012, Karlskrona, Sweden
MAC Layer – available solutions
Available solutions to tune QoS metrics: Power control Traffic class differentiation (Q-MAC) Contention-free vs. contention-based approaches Duty-cycling control Queuing and scheduling mechanisms Error control mechanisms
For WMSN, most important features are: Intra/Inter-node traffic class differentiation Node synchronization (duty-cycling control)
8NGI 2012, Karlskrona, Sweden
MAC Layer – available solutions
9NGI 2012, Karlskrona, Sweden
Network Layer: Routing
Traditional solutions for WSN focused on energyconsumption In the WMSN case, need also for real-time delivery Desirable features Traffic differentiation and joint-optimization ofmultiple QoS goals Resource balancing Fast adaptation to change in monitoring conditions Support to in-network processing / cross-layer opt. Scalability Energy-harvesting awareness
10NGI 2012, Karlskrona, Sweden
Network Layer – available solutions
11NGI 2012, Karlskrona, Sweden
Transport Layer
Similarly to the network layer case, availablesolutions are not suitable for WMSN.
Design guidelines Differentiated reliability Trade-off between reliability/timelinessMedia-centric collaborative reliability Congestion control Cross-layer optimization
12NGI 2012, Karlskrona, Sweden
Transport Layer – available solutions
13NGI 2012, Karlskrona, Sweden
Collaborative Sensing in WMSN
Multimedia nodes are characterized by a directional sensing model (FoV)
They can be grouped basing on their common sensing coverage
Several challenges Directional coverage Clustering / Scheduling Collaboration protocols
14NGI 2012, Karlskrona, Sweden
Conclusions and Research Challenges
Application Layer (feature-based): Novel coding techniques Practical implementations
MAC Layer Service differentiation Dynamic duty-cycling control
Network Layer: In-network processing Energy harvesting
Transport LayerMedia-centric reliability Cross-layer optimization with routing
15NGI 2012, Karlskrona, Sweden
Thank your for your attention!
16NGI 2012, Karlskrona, Sweden
Project Members
M. Cesana, A. Redondi – {cesana, redondi}@elet.polimi.itMultimedia coding, Application
N. Tiglao, A. Grilo – {nestor.tiglao, antonio.grilo}@inesc-id.pt
Routing and Transport
J. M. Barcelo-Ordinas, M. Alaei –{joseb,malaei}@ac.upc.eduMAC Layer
P. Todorova –petia.todorova@fokus.fraunhofer.de
Collaborative Sensing17NGI 2012, Karlskrona, Sweden
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