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Protocols for Self-Organization of a Wireless Sensor Network

Protocols for Self-Organization of a Wireless Sensor Network. K. Sohrabi, J. Gao, V. Ailawadhi, and G. J. Pottie IEEE Personal Comm., Oct. 2000. Presented By: earl. Introduction. Self-Organization Wireless Sensor Network --wireless sensing + data networking

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Protocols for Self-Organization of a Wireless Sensor Network

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  1. Protocols for Self-Organization of a Wireless Sensor Network K. Sohrabi, J. Gao, V. Ailawadhi, and G. J. Pottie IEEE Personal Comm., Oct. 2000. Presented By: earl

  2. Introduction • Self-Organization • Wireless Sensor Network --wireless sensing + data networking • Group of sensors (nodes) linked by wireless medium to perform distributed sensing tasks. • Example: • surveillance, security, health monitoring systems, etc

  3. Goals • Operate under dynamic condition: • startup, steady state, failure • operate unattended • Energy-efficiency

  4. Wireless Sensor Node

  5. Wireless Sensor Node http://today.cs.berkeley.edu/800demo/

  6. Design Challenges • Hardware: • digital circuit design • Wireless networking: • modulation, channel access, robust & energy efficient protocols, routing, mobility etc. • Applications: • detection and data collection, data diffusion, notification

  7. Main difference • Conventional Wireless Networks • High QoS (high throughput/low delay) & High bandwidth efficiency • Sensor Network • Length of network’s lifetime need to conserve energy • Performance highly depends on energy efficiency of algorithms

  8. Energy-Conserving • Energy consumptions: • Sensing • Data processing • Communications • Communications is the major energy consumer • Therefore, local processing is key

  9. ORM concept • O -Organization of nodes to access shared medium  network formation • R -Routing in the network • M -Mobility management

  10. Protocols • Self-Organization Medium Access Control for Sensor Networks (SMACS) • Network startup and link layer • Eavesdrop-And-Register (EAR) Algorithm • Seamless interconnection of mobile nodes in the field of stationary wireless nodes (mobility management) • Sequential Assignment Routing (SAR) • Facilitates multi-hop routing • Single Winner Election (SWE) and Multi-Winner Election (MWE) • Facilitates local cooperative information processing

  11. SMACSProtocol • Used for network startup and link-layer organization • Forms a flat topology

  12. b c a i f d e h g SMACSProtocol • SMACS Operation • Discover neighbors • Assign a channel to a links between neighboring nodes • Channel (time slot) = pair of time intervals (transmission/reception pattern) • Each link operates on a different frequency (which is randomly chosen) • Only local knowledge  quick  energy saving • Node turns on/off communication according to its timeslots

  13. SMACS Protocol • Node topology

  14. SMACS Protocol

  15. SMACS Protocol Type1: invitation [to B、G] (node’s id and number of attached neighbors) Type2: response to Type1 [from B、G] (inviter and invitee’ addresses and invitee’s attached state)

  16. SMACS Protocol • Type3: response to Type2 to notify chosen node [to B] • Inviter not attached : none • Inviter, invitee, attached : inviter’s schedule and frame epoch • Invitee not attached, inviter attached: proposed channel for the link, calculated by inviter

  17. SMACS Protocol • Type4: response to Type3 [from B] • Invitee not attached, inviter not attached: channel determined by the invitee • Invitee not attached, inviter attached: none • Invitee attached, inviter not attached: channel determined by the invitee

  18. EAR Protocol • The Ear algorithm’s motivation • Designed to provide continuous communication capability between mobile and stationary nodes • Mobile nodes join stationary wireless nodes • Mobile node is “eavesdropping” on control signals • Both side keep a “registry” of neighbors’ information

  19. EAR Protocol • EAR algorithm • Broadcast Invite (BI): • The stationary node invites other nodes to join • Mobile Invite (MI): • The mobile responds to BI to request a connection • Mobile Response (MR): • The stationary node accepts the MI response • Mobile Disconnect (MD): • The mobile informs the stationary response is needed node of a disconnect; no stationary node mobile node BI [MI/MD] MR BI triggers EAR BI:{SNR, node ID, Tx Power,…} If MI info. possible, assign slot in TDMA frame Connect and disconnect thresholds

  20. EAR Protocol • Mobile nodes have the onus to manage connections/disconnections with stationary nodes based on the received signal-to-noise (SNR) ratio • Connection and disconnection thresholds determine connectivity: • Connection Threshold (CT) : minimum level where connectivity is enabled (SNR > CT) • Disconnection Threshold (DT) : maximum level of connectivity (SNR < DT)

  21. EAR Protocol 3 1 2 MOBILE [ SNR > CT ] MI Message BI Message MR Message 6 5 Mobile Connectivity List: EAR is an adaptable protocol that allows stationary and mobile nodes to self-organize and establish connectivity 1 2 6 5

  22. SAR Protocol • Supports multi-hop routing • Route must be robust to failure • It takes into consideration the energyresource and QoS on each path

  23. sink Consider power,QoS Backup route SAR for Multi-hop routing • Failure Protection • Creates multiple trees where the root of each tree is a one-hop neighbor from the sink

  24. SWE & MWE Protocols • Handle signaling and data transfer in local cooperative signal processing: • Noncoherent Processing  SWE • Coherent Processing  MWE • Elect Central Node (CN) for sophisticated information processing • Sufficient energy reserve, computational capability, high SNR

  25. Noncoherent Cooperative Function • No need for path optimality • 3-Phase process: • Phase I: Target detection, data collection, and preprocessing • Phase II: Membership declaration • Phase III: Central node election

  26. CN Election • 2 components • SWE algorithm —handle signaling for candidate information “Elecmessage” • Each node can announce itself as a CN candidate • Compare information, keep record of 1 best candidate • Disseminate information throughout the network • Spanning Tree (ST) algorithm —compute a min-hop ST rooted at the CN

  27. Multi-Winner Election(SWE) Process

  28. Coherent Cooperative Function • Differ from noncoherent algorithm • Explicit computation of minimum energy path: Path optimality for energy efficiency • Limited number of sensor source nodes (SNs) • MWE • Select SNs • Calculate minimum energy paths from sensor node to each SN • Use SWE to select CN from minimum energy consumption

  29. Single Winner Election (SWE) Process

  30. Simulation • Network of 45 randomly scattered nodes having a density of 0.04 nodes/m2 • 1mW transmit power, Tframe = 8.0s

  31. Simulation

  32. Simulation

  33. Simulation

  34. Conclusion • Wireless Sensor Network Protocols • Low mobility, enough BW, energy-constrained • Self-Organization Medium Access Control for Sensor Networks (SMACS) • Eavesdrop-And-Register (EAR) Algorithm • Sequential Assignment Routing (SAR) • Single Winner Election (SWE) and Multi-Winner Election (MWE) • Future work • Determine Min energy bound for network formation • Higher mobility

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