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Issues of Wireless Sensor Networks


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this presentation presents the major issues relative to the WSN. It gives, also, a brief description of the potential solutions

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Issues of Wireless Sensor Networks

  1. 1. 1/24/2014 Networking Issues in Wireless Sensor Networks Presented by: Souhaiel Ben Tekaya 1
  2. 2. Introduction fields(forest, military, surveillance, transportatio 1/24/2014 • Emerging field in different n…) • Role: collect data then transfer it to central locations. • Focus on fundamental issues: • Networking • Power 2
  3. 3. Networking issues • Limited energy supply, • limited computing power, • limited bandwidth of the wireless links connecting data. 1/24/2014 • Differs from classic networks on : • Routing challenges: • Data aggregation, • Coverage/ scalability, • Data reporting methods (protocols). 3
  4. 4. Networking issues Critical task since we need to consider some factors: • Node heterogeneity, • Node failure tolerance, • Quality of service, 1/24/2014 • Design issues:  Prevent connectivity degradation by employing energy management techniques. 4
  5. 5. Networking issues (protocols) • Use position of routers & packet destination to make forwarding destination. • Sensitive to rate of change of the network and number of routers in the network. • 2 algorithms: 1/24/2014 • Greedy perimeter stateless Routing (GSPR): • Greedy forwarding: decision made locally (node) based on closest node to destination. • Perimeter forwarding: when previous not applicable. Chooses one of the surrounding nodes based on the right hand rule. 5
  6. 6. Networking issues • Consider energy factor and avoid flooding packets. 1. packet outside region: 1/24/2014 • Geographical and Energy Aware Routing (GEAR) routing with energy aware metrics (calculate the less energy consuming way to destination) 2. Packet within region: restricted flooding algorithm 6
  7. 7. Power conservation while maintaining multi-hop routing consumer in a sensor. 1/24/2014 • the transceiver is considered the largest energy • Powering off the sensor will be the best way. But, areas in the sensor network will be isolated and inaccessible by queries. • Most proposed solution: Duty-cycling. 7
  8. 8. duty-cycling Duty-cycling exploit node redundancy in sensor network, by putting Three categories: 1/24/2014 in a sleep state all unnecessary sensors for connectivity. Sleep and wake-up: independent from the network topology and MAC protocol. low duty cycle combined with MAC protocols: integrated in the MAC protocol. duty-cycle control through topology management: Exploiting the dense aspect of sensor networks. 8
  9. 9. Sleep and wake-up
  10. 10. a. Sleep and wake-up independent from the network topology and MAC protocol. Three categories: • On-demand: wakeup only when another node wants to talk with it using two different radios. • Scheduled rendezvous: closed node are wakeup at exactly the same time. • Asynchronous schemes: nodes wakeup independently while always guaranty an overlapped active period
  11. 11. b. low duty cycle combined with MAC protocols
  12. 12. b. low duty cycle combined with MAC protocols • TDMA-based: channel access is done on a slot-by-slot basic, Bluetooth and LEACH are two examples. • Contention-based: similar to sleep/wakeup scheme, integrating the sleep/wakeup algorithm to the MAC protocol. • Hybrid protocols: combines both TDMA and contention protocols.
  13. 13. c. duty-cycle control through topology management • Exploiting the dense aspect of sensor networks. • Most common protocols: a. GAF: divide the network to fixed square grids. b. SPAN: sleep state or to join the backbone upon the connectivity information given by the routing protocol. c. ASCENT: packet loss and connectivity information.