Wireless Sensor Networks COE 499 Sleep-based Topology Control I

1. Wireless Sensor Networks COE 499Sleep-based Topology Control I Tarek Sheltami KFUPM CCSE COE http://faculty.kfupm.edu.sa/coe/tarek/coe499.htm

2. Outline • Overview • Constructing topologies for connectivity • BEAC/AFECA • GAF, CEC • ASCENT • SPAN

3. Overview • Topology control can be defined as the process of configuring or reconfiguring a network’s topology through tunable parameters after deployment. There are three major tunable parameters for topology control: • Node mobility • Power of transmission • Sleep scheduling • In practice, a limited number of expensive nodes are deployed in specific locations and must be active at all time. On the other hand, inexpensive nodes are redundant, deployed in remote locations and their precise location is not essential • Over deploying the network may provide some significant advantages: • Longer lifetime • Robustness • Tunable coverage/connectivity

4. Constructing topologies for connectivity Basic/adaptive fidelity energy conserving algorithms (BECA/AFECA)

5. Constructing topologies for connectivity.. Geographic adaptive fidelity (GAF)

6. Constructing topologies for connectivity.. • Geographic adaptive fidelity (GAF).. • Deployed in virtual grid topology • The priority scheme based on the residual power • Each node broadcast its ID, grid ID and residual power • The grid cell size, r, is sufficiently small (r< ) • A related Cluster-based Energy Conservation (CEC) eliminates the need of geographic info to setup the virtual grid • A node is elected as clusterhead if it has a higher residual power • Gateways are allowed to communicate with more than one clusterhead • Sleep timers are set so that nodes wake-up to run a re-election before the clusterhead’s energy depleted • Node may wake up to send data

7. Constructing topologies for connectivity.. Adaptive self-configuring sensor network topology control (ASCENT) Unless the number of neighbors > NT or its participation will increase the loss rate

8. Constructing topologies for connectivity.. • Adaptive self-configuring sensor network topology control (ASCENT).. • Intended for highly dynamic environment • Nodes wakeup to assist in routing depending on the number of neighbors and the measured data lose in their vicinity • Nodes are expected to be active until they die • What are the tunable parameters?

9. Constructing topologies for connectivity.. Neighborhood coordinators (SPAN)

10. Constructing topologies for connectivity.. • Neighborhood coordinators (SPAN).. • Only a subset of nodes, call coordinators nodes are active • Non-coordinating nodes go to sleep, waking up periodically to go to test state, send HELLO messages and check for eligibility to become coordinators: • If two neighbors can’t reach each other or via <3 coordinators • The eligibility decision is based on the content of HELLO messages sent by all nodes announcing their coordinators and neighbors • The algorithm ensures that there are coordinators in every radio broadcast range in the network to minimize congestion • Nodes give up their rules as coordinators if they no longer satisfy the eligibility rule or after time period to ensure load balancing