1. State of the Art in Protocol Research for UnderWater Acoustic Sensor Networks (UW-ASNs) Date : 2007. 11. 22 ( 木 ) Name : Jeong-Chun, Joo. 2006, ACM_WUWNet'06 Ian F. Akyildiz, Dario Pompili, and Tommaso Melodia Georgia Institute of Technology

2. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Contents Introduction Communication Architecture UW-ASN: Design Challenges Medium Access Control (MAC) Layer Network Layer Transport Layer Conclusion - 2 / 38 -

3. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. - 3 / 38 - Introduction

4. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Applications (1/2) 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) - 4 / 38 -

5. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Applications (2/2) - 5 / 38 -

6. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Underwater Networks Traditional approach : deploy underwater sensors that record data  No real-time monitoring, No on-line system reconfiguration, No failure detection, Limited Storage Capacity Wireless links that rely on acoustic communications  Acoustic communication ⇒ physical layer technology in underwater networks  High attenuation ⇒ radio waves propagation problems  Links for underwater networks are typically based on acoustic wireless communications - 6 / 38 -

7. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Challenges in design of UW-ASNs Available bandwidth is limited Propagation delay underwater = 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 - 7 / 38 -

8. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. - 8 / 38 - Communication Architecture

9. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Communication 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 - 9 / 38 -

10. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Static two-dimensional UW-ASNs (1/2) - 10 / 38 - Comms. Intra clusters (using CH) Comms with the surface station anchored Acoustic link comms RF comms Satellite comms

11. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Static two-dimensional UW-ASNs (2/2) 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 - 11 / 38 -

12. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Three-dimensional UW-ASNs (1/2) - 12 / 38 - anchored RF comms Satellite comms Comms with the surface station Acoustic link comms

13. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Three-dimensional UW-ASNs (2/2) 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 - 13 / 38 -

14. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. - 14 / 38 - Sensor Networks with AUV anchored RF comms Satellite comms Comms with the surface station Acoustic link comms

15. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. - 15 / 38 - UW-ASN:DESIGN CHALLENGES

16. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. 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 - 16 / 38 -

17. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. 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 - 17 / 38 -

18. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Influencing Factors Transmission 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 Multipath High delay and delay variance  Propagation delay Underwater = 5 x Radio Frequency(RF) ground Doppler spread - 18 / 38 -

19. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. - 19 / 38 - MEDIUM ACCESS CONTROL LAYER

20. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Multiple access techniques Frequency Division Multiple Access (FDMA)  the narrow bandwidth in UW-A channels  The vulnerability of limited band systems to fading and multipath Time Division Multiple Access (TDMA)  Limited bandwidth efficiency  Long time guards required in the UW-A channel Carrier Sense Multiple Access (CSMA) Code Division Multiple Access (CDMA) - 20 / 38 -

21. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. CSMA Based MAC Protocols Slotted FAMA(’06.9) : Floor Acquisition Multiple Access  Applies control packets before starting transmission to avoid multiple transmissions at the same time PCAP(’06.9) : Propagation-delay-tolerant Collision Avoidance Protocol  Fix the time spent on setting up links for data frames  Avoid collisions by scheduling the activity of sensors Distributed energy-efficient MAC protocol (’05)  Minimize the energy consumption  Don’t consider bandwidth utilization or access delay - 21 / 38 -

22. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. CDMA-based MAC Protocols UW-MAC (’06.8 by Pompili)  Goals  high network throughput  low access delay  low energy consumption  Main Feature  unique and flexible solution for different architectures  fully distributed  intrinsically secure since it uses chaotic codes  efficiently supports multicast transmissions  robust against inaccurate node position and interference information - 22 / 38 -

23. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Open research issues Design access codes for CDMA taking into account minimum interference among nodes Maximize the channel utilization Design low-complexity encoders and decoders Distributed protocols to save battery consumption - 23 / 38 -

24. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. - 24 / 38 - NETWORK LAYER

25. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. existing routing protocols (1/3) 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 - 25 / 38 -

26. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. existing routing protocols (2/3) Reactive routing protocols  Ad hoc On Demand Distance Vector (AODV), 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  Most of the reactive protocols rely in symmetrical links - 26 / 38 -

27. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. existing routing protocols (3/3) 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 leveraging localization 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 - 27 / 38 -

28. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Routing Protocols for UW-ASNs (1/3) VBF (Vector-Based Forwarding)(’06.5)  Location-based routing protocol  Only nodes in routing pipe forward messages - 28 / 38 -

29. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Routing Protocols for UW-ASNs (2/3) Virtual circuit routing technique (’06.6)  1 st phase : Centralized Routing Problem  determine optimal node-disjoint primary and backup multihop data paths  2 nd phase : Localized Network Restoration  Guarantee survivability of the network to node and link failures by locally repairing paths - 29 / 38 -

30. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Routing Protocols for UW-ASNs (3/3) Geographical routing algorithms for the 3D underwater environment (’06.9 by Pompili)  Objectives  Increasing the efficiency of the channel  Limiting the packet error rate  Algorithm for Delay-insensitive applications  Guarantee a low packet error rate  Maximize the probability that a packet is correctly decoded at receiver → Minimize the number of required packet retransmissions  Algorithm for Delay-sensitive applications  next hops are selected by also considering maximum per-packet allowed delay - 30 / 38 -

31. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Open research issues Develop algorithms that reduces the latency Develop mechanisms to handle loss of connectivity without generating retransmission Accurate network modeling and realistic simulation modes / tools is needed Algorithms and protocols need to improve the way to deal with disconnections because of failures of battery depletion How to integrate AUVs with UW-ASNs and enable communication between sensors and AUVs - 31 / 38 -

32. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. - 32 / 38 - TRANSPORT LAYER

33. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Transport protocol of UW-ASNs 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 RTT(Round Trip Time) in underwater environment affect the throughput of most TCP implementation  The variability of the underwater RTT would make it hard to effectively set the timeout of the window-based mechanism - 33 / 38 -

34. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. - 34 / 38 - Requirement of a transport layer for UW-ASNs Correct handling of Shadow zones Minimum energy consumption Rate-based transmission of packets Out-of-sequence packet forwarding Timely reaction to local congestion  In case of congestion, transport layer need to be adapted faster to decrease the response time Cross-layer-interaction based protocol operation Reliability hop by hop SACK(selective acknowledgment)-based loss recovery

35. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. SDRT (Segmented Data Reliable Transport)(’06) Key Idea  Transfer encoded packets, block by block and hop by hop  Use Tornado codes to recover errored packets Operations  Sender  Encodes a block using random forward-error correction codes.  Keeps pumping a stream of encoded packets (in a random order), until receiving a positive feedback from the receiver  Receiver  Keeps receiving packets until it can reconstruct the original data packets, and sends a positive feedback to the sender  Encodes the reconstructed packets and relay them to the next hop. - 35 / 38 -

36. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. 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 Reliability-metric definitions based on the event model and on the underwater acoustic channel model To study the effects of multiple concurrent events To statistically model loss of connectivity events To create solutions for handling the effect of losses of connectivity caused by shadow zones - 36 / 38 -

37. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Conclusions Overview of the state of the art in underwater acoustic sensor network Ultimate objective : Encourage research efforts Goods :  A good introduction of Underwater Acoustic Sensor Networks.  Many related researches are well explained. Bads :  Surface explanations  Lack of experiment results - 37 / 38 -

38. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Questions ? Hi!!!, your look is cool Biomimetic Underwater Robot, Robolobster

39. Korea Advanced Institute of Science and Technology [CS712] Topics in Parallel Processing [20075183] Jeong-Chun, Joo. Tornado Encoding and Decoding