UNDERWATER ACUSTIC SENSOR NETWORKS (UW-ASNs)

1. UNDERWATER ACUSTIC SENSOR NETWORKS (UW-ASNs) Daladier Jabba Molinares Department of Computer Science and Engineering University of South Florida Tampa, FL 33620 daladier@cse.usf.edu

2. UNDERWATER ACUSTIC SENSOR NETWORKS (UW-ASNs) • Introduction • Communication architecture • UW-ASN: Design challenges • Principal layers • MAC Layer • Network Layer • Transport Layer • Clusters in Mobile Ad hoc Networks • Minimum Cut problem applied to UW-ASN • References • Questions

3. INTRODUCTION

4. INTRODUCTION • Group of sensors and vehicles deployed underwater and networked via acoustic links, performing collaborative tasks • Equipment • Autonomous Underwater Vehicles (AUVs) • Underwater sensors (UW-ASN)

5. INTRODUCTION (Cont…) • Objectives • UW_ASNs • To exploit multi hop paths • To minimize the signaling overhead for building underwater paths • AUVs • Rely on local intelligence • Less dependent on communications from online shores • Control strategies (autonomous coordination obstacle avoidance)

6. INTRODUCTION (Cont…) • Applications • Environment monitoring • Review how human activities affect the marine ecosystem • Undersea explorations • Detect underwater oilfields • Disaster prevention • Monitoring ocean currents and winds (Tsunamis) • Assisted navigation • Locate dangerous rocks in shallow waters • Distributed tactical surveillance • Intrusion detection (Navy)

7. INTRODUCTION (Cont…) • Acoustic comms  physical layer technology in underwater networks • High attenuation  radio waves propagation problems • Links for underwater networks based on acoustic wireless communications (typically used)

8. INTRODUCTION (Cont…) • Challenges • Available bandwidth is limited • Propagation delayUnderwater=5 x Radio Frequency(RF)ground • High bit errors and temporary loss of connectivity • Limited battery power • Tendency of failure in the underwater sensors because of corrosion

9. COMMS ARCHITECTURE

10. COMMS ARCHITECTURE • Two-dimensional Underwater Sensor Networks : for ocean bottom monitoring • Three-dimensional Underwater Sensor Networks : for ocean-column monitoring • Sensor Networks with Autonomous Underwater vehicles : for underwater explorations

11. COMMS ARCHITECTURE (Cont…) 1. Static two-dimensional UW-ASNs for ocean bottom monitoring • Components: Gateway *: not necessary

12. COMMS ARCHITECTURE (Cont…) Satellite comms RF comms Comms with the surface station Acoustic link comms Comms. Intra clusters (using CH) anchored

13. Static two-dimensional UW-ASNs for ocean bottom monitoring (Cont…) • Problems • Long distances between gateways and UW-ASNs • Power to transmit decay easy • It is better multi hop paths • Bandwidth limitations • Greater bandwidth for a shorter transmission distance • Increasing the UW-ASNs density generates routing complexity • Solving the problems • Energy savings • Increase network capacity

14. COMMS ARCHITECTURE (Cont…) 2. Three-dimensional Underwater Sensor Networks • Components: *: not necessary

15. COMMS ARCHITECTURE (Cont…) Satellite comms RF comms Comms with the surface station Acoustic link comms anchored

16. Three-dimensional Underwater Sensor Networks (Cont…) • Problems • If they are attached to a surface buoy • They can be easily detected by enemies • Floating buoys are vulnerable to the weather and pilfering • ship navigations can be a problem • Increasing the UW-ASNs density generates routing complexity • Solving the problems • Be anchored to the bottom of the ocean (to an anchors by wires) • Energy savings • Increase network capacity

17. COMMS ARCHITECTURE (Cont…) 3. Sensor Networks with Autonomous Underwater vehicles • Components: AUV *: not necessary

18. COMMS ARCHITECTURE (Cont…) Satellite comms RF comms Comms with the surface station Acoustic link comms anchored

19. UW-ASN:DESIGN CHALLENGES

20. DESIGN CHALLENGES (Cont…) • UWSNs vs Terrestrial Sensor Networks • Cost • Terrestrial sensor networks will be cheaper and cheaper with the time • UWSNs are expensive • Deployment • Terrestrial SNs are densely deployed • UWSNs are generally more sparse • Power • For UWSNs is higher • Memory • Terrestrial sensors have less capacity

21. DESIGN CHALLENGES (Cont…) • Basics of acoustic propagation in UWSNs • Radio waves propagation for long distances through sea water only at frequencies of 30-300 Hz • High transmission power • Large antennas • Poor available Bandwidth * In 802.11b : between 2.412 GHz to 2.484 GHz

22. DESIGN CHALLENGES (Cont…) • Some factors that affect the design • Path loss • Attenuation provoked by absorption due to conversion of acoustic energy into heat • Because of the spreading sound energy as a result of the expansion of the wavefronts • Noise • Man-made noise • Ambient noise • High delay • Propagation delayUnderwater=5 x Radio Frequency(RF)ground

23. MEDIUM ACCESS CONTROL LAYER Biomimetic Underwater Robot, Robolobster

24. MAC LAYER (Cont…) • Multiple access techniques • Code Division Multiple Access (CDMA) • Carrier Sense Multiple Access (CSMA) • Time Division Multiple Access (TDMA) • Frequency Division Multiple Access (FDMA)

25. MAC LAYER (Cont…) • Proposed MAC protocols • Slotted Fama • Applies control packets before starting transmission to avoid multiple transmissions at the same time • Issue: handshaking process can generate low throughput

26. MAC LAYER (Cont…) • Adapted MACA to underwater acoustic networks • It uses CTS-RTS-DATA exchange and for Error detection STOP and WAIT ARQ • Retransmitting packets because of timeout in receiving ACK • The source drops the communication after K trials • Problems • Energy consumption because of repeating RTS several times before receiving a CTS • Deadlock problems • Solutions • To add a WAIT commands (destination tells that is busy) • Add an assignment priority to every packet

27. MAC LAYER (Cont…) • Clustering and CDMA/TDMA multiple access • For distributed UW-ASNs • Communication intra cluster uses TDMA (time slots) • CDMA by each cluster using a different code for transmission • Problem • Number of code is limited • Solution proposed • Reusable code (possible because the acoustic signal fades due to distance)

28. MAC LAYER (Cont…) • Open research issues • Design access codes for CDMA taking into account minimum interference among nodes • Maximize the channel utilization • Distributed protocols to save battery consumption

29. NETWORK LAYER

30. NETWORK LAYER (Cont…) • Proactive routing protocols • Dynamic Destination Sequenced Distance Vector (DSDV), Optimizing Link State Routing (OLSR) • They are not suitable for UW-ASNs • Large signaling overhead every time network topology has to be updated • All nodes are able to establish a path with others and it is not necessary

31. NETWORK LAYER (Cont…) • Reactive routing protocols • Ad hoc On Demand Distance Vector (AODV) and Dynamic Source Routing (DSR) • They are not suitable for UW-ASNs • It requires flooding of control packets at the beginning to establish paths (excessive signaling overhead) • High latency on establishment of paths • Must of the reactive protocols rely in symmetrical links

32. NETWORK LAYER (Cont…) • Geographical routing protocols • Routing with Guaranteed Delivery in Ad Hoc Wireless Networks (GFG) and Optimal local topology knowledge for energy efficient geographical routing in sensor networks (PTKF) • Establish source destination paths by leveraginglocalization information • A node selects its next hop based on the position of its neighbors and of the destination node • Problems • They work with GPS (GPS uses waves in the 1.5 GHz band) • It has not been improved the localization information in the underwater environment

33. NETWORK LAYER (Cont…) • Solution proposed • Network layer protocols specifically tailored to underwater environment • Example • A routing protocol was proposed that autonomously establishes the underwater network topology, control network resources and establishes the network flows using a centralized management

34. NETWORK LAYER (Cont…) • Open research issues • Develop algorithms that reduces the latency • Handle loss of connectivity using mechanisms without generating retransmission • Algorithms and protocols needs to improve the way to deal with disconnections because of failures of battery depletion • How to integrate AUV with UW-ASNs and able communication among them

35. TRANSPORT LAYER

36. TRANSPORT LAYER (Cont…) • Unexplored area • It has to perform: • Flow control • To avoid that network devices with limited memory are overwhelmed by data transmissions • Congestion control • To prevent the network being congested • TCP implementations are not suited • The long Round Trip Time (RTT) in underwater environment affect the throughput

37. TRANSPORT LAYER (Cont…) • A transport layer for UW-ASNs requieres: • Reliability hop by hop • In case of congestion, transport layer need to be adapted faster to decrease the response time • Minimum energy consumption • To avoid many feedbacks with the ACK mechanism that can utilize bandwidth unnecessarily

38. TRANSPORT LAYER (Cont…) • Open research issues • Flow control strategies to reduce not only the high delay but also delay variance of the control messages • Efficient mechanisms to find the cause of packet loss • To create solutions for handling the effect of losses of connectivity caused by shadow zones

39. Clusters in Mobile Ad hoc Networks

40. Clusters in Mobile Ad hoc Networks (Cont…) • Reduce the overhead in the network • Reduce power consumption • Different type of nodes • Cluster head • Gateway • Nodes in the cluster • Communication • Intra cluster • Inter cluster

41. Clusters in Mobile Ad hoc Networks (Cont…) • Problems • Hidden Terminal problem • Exposed Terminal problem

42. Clusters in Mobile Ad hoc Networks (Cont…) • Topology control (Cluster Initialization) • LIDCA algorithm • lowest identifier • HCCA algorithm • high connectivity • Minimum cut problem (graph theory) • Contract nodes • Routing protocols • Maintenance

43. c b a a x c b x b,c e d f e d f a x D,e,f b,c X,a,b,c e f d Connectivity Challenge • Minimum Cut problem applied to UW-ASN (Network layer) • To reduce interference

44. References • I. F. Akyildiz, D. Pompili, and T. Melodia. Underwater Acoustic Sensor Networks: Research Challenges. Ad Hoc Networks (Elsevier), vol. 3(3), pp. 257–279, May 2005. • K. Kredo and P. Mohapatra. Medium Access Control in Wireless Sensor Networks. to appear in Computer Networks (Elsevier), 2006. • F. Salva-Garau and M. Stojanovic. Multi-cluster Protocol for Ad Hoc Mobile Underwater Acoustic Networks. In Proc. Of MTS/IEEE OCEANS. San Francisco, CA, Sep. 2003. • Hayat DOUKKALI and Loutfi NUAYMI. Analysis of MAC protocols for Underwater Acoustic Data Networks. 0-7803-8887-9/05. (c)2005 IEEE • Jim Partan, Jim Kurose Brian Neil Levine. A Survey of Practical Issues in Underwater Networks. • Borja Peleato and Milica Stojanovic. A MAC Protocol for Ad Hoc Underwater Acoustic Sensor Networks. WUWNet’06, September 25, 2006. • Ian F. Akyildiz, Dario Pompili, and Tommaso Melodia. State of the Art In Protocol Research for Underwater Acoustic Sensor Networks. WUWNet’06, September 25, 2006.

45. ? Hi!!!, your look is cool Questions