Energy-Driven Adaptive Clustering Hierarchy (EDACH) for Wireless Sensor Networks

1. Energy-Driven Adaptive Clustering Hierarchy (EDACH) for Wireless Sensor Networks Kyung Tae Kim, Hee Yong Youn (Sungkyunkwan University) Research supported by the “uAuto” Project

2. Outline • Introduction • System Model • Proposed Protocol - EDACH • Performance Evaluation

3. WSN • Wireless sensor network enables the collection of useful information in real life. • It is composed of hundreds or thousands of sensor nodes. • Since sensor nodes carry constrained power source, power conservation is a critical design issue for routing protocol.

4. Clustering-based Routing • Selects a set of cluster-heads among the nodes in the network, and clusters the rest of nodes (member nodes) with the cluster-heads • 2 clustering-based routing protocol referred to: • LEACH • EDACH

5. LEACH • Low-Energy Adaptive Clustering Hierarchy, a protocol proposed to solve the energy consumption problem • Employs randomized rotation of the cluster-heads to evenly distribute the energy load among the sensor nodes in the network

6. EDACH • Energy-Driven Adaptive Clustering Hierarchy, an enhanced version of LEACH • Increases the lifetime and reliability of sensor network in the presence of faults at the cluster-head

7. Outline • Introduction • System Model • Proposed Protocol - EDACH • Performance Evaluation

8. Single-Hop Clustered Network • Nodes and cluster-heads are homogenous • Communication over wireless link

9. Energy Model of a Sensor • 1st order radio model • A radio dissipates Eelec (e.g. 50nJ/bit) to run the transmitter or receiver circuitry and εamp (e.g. 100pJ/bit) for the transmitter amplifier

10. Fault Model • Consider only data transmission faults of cluster-head

11. Outline • Introduction • System Model • Proposed Protocol - EDACH • Performance Evaluation

12. LEACH Overview • The operation is divided into rounds. • Each of these rounds consists of 2 phases: a set-up phase and a steady-state phase. • During the set-up phase cluster-heads are determined and the clusters are organized. • During the steady-state phase data trans-ference to the base station occurs.

13. EDACH Overview • Periodic operation of the following 2 phases: a set-up phase and a self-organized data collection and transmission phase. • The set-up phase is identical to LEACH. • The 2nd phase is modified to deal with the possible problem that cluster-heads in the LEACH have no sufficient energy to carry out the duty of cluster-head.

14. Enhancement • If a cluster encounters a problematic cluster-head, then a proxy is selected to operate in replace of the original cluster-head.

15. Set-up Phase • In order to select cluster-heads, each node chooses a random number between 0 and 1. • If the number is smaller than a threshold, the node becomes a cluster-head for the current round.

16. Set-up Phase • The threshold is set as: where P is the desired percentage of cluster-heads, r is the current round, and G is the set of nodes that have not been cluster-heads in the last 1/P rounds. • Every node becomes a cluster-head exactly once within 1/P rounds.

17. Set-up Phase • After selection, every selected cluster-head advertises its token by CSMA/CA MAC protocol to all its neighbors. • Comparing the signal strength of the token, non cluster-head nodes choose among the strongest and broadcasts an answer packet including node’s position and remaining energy also by CSMA/CA.

18. Set-up State • At last, the cluster-head node creates a TDMA schedule telling each node when it can transmit.

19. Self-organized Data Collection and Transmission Phase • Starts after the set-up phase. • Every nodes collected local data, and sends the packet to the cluster-head in its allocated transmission time. • No doubt that cluster-heads consumes much more power and more likely to suffer from depletion.

20. Ways to Save the Energy • For member nodes, by using the minimal amount of energy to transmit according to the signal strength of the token received • For member nodes, by turning off until its allocated transmission time • A Cluster-head aggregates the data gathered before sending it to the base station.

21. Difference • A threshold value ETH is used as a measure for deciding if the current cluster-head has become obsolete. where kj is the length of the aggregated message in the j-th cluster-head, dCH is the distance between cluster-head and the base station

22. Difference • Once the energy of a cluster-head drops below the threshold, the proxy node selection process begins. • A cluster-head of EDACH maintains a table of remaining energy and nodes’ position of its members so it can select a member node to be a proxy node by comparing the 2 factors.

23. Proxy Node Determination

24. Indicator Control Message Advertisement Process

25. Outline • Introduction • System Model • Proposed Protocol - EDACH • Performance Evaluation

26. Network Lifetime

27. Number of Alive Sensors as the round proceeds with 0.25J/node

28. Location of Alive (Circle) and Dead (Dot) Sensor Nodes

29. Conclusion • EDACH outperforms the LEACH more significantly when the initial energy is relatively high. • The residual energy is well balanced among all the sensors because the protocol select the most capable node to be a proxy when facing problematic cluster-head. • The dead nodes of EDACH well dispersed.