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Data Aggregation

Data Aggregation. By Valliappan Annamalai. Wireless Sensor networks (WSN): A collection of sensors deployed in an environment form a network to collectively accomplish a task Characteristics Low data rate Many to one data flow. Wireless Sensor Networks. To External network.

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Data Aggregation

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  1. Data Aggregation By Valliappan Annamalai

  2. Wireless Sensor networks (WSN): A collection of sensors deployed in an environment form a network to collectively accomplish a task • Characteristics • Low data rate • Many to one data flow

  3. Wireless Sensor Networks To External network Base station (BS) or Sink Inaccessible Environment Wireless Communication link Sensors

  4. Monitoring Application • Monitoring application involve dissemination of request and data gathering. • Dissemination: Dissemination of request is done by sink node to all or a set of nodes in the network. • Data gathering: Data collection from all a set of source nodes towards the sink node.

  5. Data Gathering • Issues • Route construction • Energy consumption • In-network data aggregation • Latency incurred • Channel access

  6. Energy Consumption • Energy Consumed in a sensor can be divided into • Energy to run transceiver circuitry • Amplification energy • Choosing shortest path • Minimum number of hops • Minimum amplification energy

  7. Aggregation • Helps in • reducing energy consumed • In-network data processing • Types • Linear • Intermediate • Perfect

  8. Latency • Dependent on aggregation. • Other delays • Transmission delay • Propagation delay • Retransmission delay

  9. Collision arises when • Two nodes transmit to the same node • A node receiving data is in the communication range of another transmission

  10. Avoiding collision • Contention-based scheme (IEEE 802.11): using control packets. • Contention-free scheme (Channel allocation): Assigning channel to each pair of communicating entities.

  11. Suboptimal data aggregation [1] • CNS: Source closest to the sink is chosen as the aggregation point • SPT: Shortest path from each source to sink is constructed • GIT: Each source connects to the existing tree via shortest path.

  12. PEGASIS [2] • Chain based data aggregation. • Proposed for perfect data aggregation. Base station (BS) or Sink

  13. Convergecasting in WSNs [3] • Construct a tree: done by reducing number of hops and choosing the shortest route. • Channel allocation: Done based on interfering neighbors.

  14. Convergecasting in WSN based on balanced tree construction [4] • Balanced tree helps in reducing latency. • Channel allocation

  15. References • “Modelling Data-Centric Routing in Wireless Sensor Networks” by B. Krishnamachari, D. Estrin, S. Wicker Published in IEEE INFOCOM • “PEGASIS: Power-Efficient Gathering in Sensor Information Systems” by S. Lindsey C. S. Raghavendra Published in IEEE Aerospace Conference Proceedings • “On Tree-Based Convergecasting in Wireless Sensor Networks” by V. Annamalai, S. K. S. Gupta and L. Schwiebert Published in IEEE Wireless Communications and Networking Conference • “A low-latency and energy-efficient algorithm for convergecast in wireless sensor networks” byS. Upadhyayula, V. Annamalai and S. K. S. Gupta Published in Proceedings of GLOBECOM 2003.

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