UNDERWATER ACUSTIC SENSOR NETWORKS UWASNs

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UNDERWATER ACUSTIC SENSOR NETWORKS (UW-ASNs)

• Daladier Jabba Molinares
• Department of Computer Science and Engineering
• University of South Florida
• Tampa, FL 33620
• daladier_at_cse.usf.edu

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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

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INTRODUCTION
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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)

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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)

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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)

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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)

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INTRODUCTION (Cont)

• Challenges
• Available bandwidth is limited
• Propagation delayUnderwater5 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

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COMMS ARCHITECTURE
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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

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COMMS ARCHITECTURE (Cont)

• 1. Static two-dimensional UW-ASNs for ocean
  bottom monitoring
• Components

Gateway
not necessary
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COMMS ARCHITECTURE (Cont)
Satellite comms
RF comms
Comms with the surface station
Acoustic link comms
Comms. Intra clusters (using CH)
anchored
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• 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

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COMMS ARCHITECTURE (Cont)

• 2. Three-dimensional Underwater Sensor
• Networks
• Components

not necessary
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COMMS ARCHITECTURE (Cont)
Satellite comms
RF comms
Comms with the surface station
Acoustic link comms
anchored
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• 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

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COMMS ARCHITECTURE (Cont)

• 3. Sensor Networks with Autonomous
• Underwater vehicles
• Components

AUV
not necessary
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COMMS ARCHITECTURE (Cont)
Satellite comms
RF comms
Comms with the surface station
Acoustic link comms
anchored
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UW-ASNDESIGN CHALLENGES
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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

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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

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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 delayUnderwater5 x Radio
  Frequency(RF)ground

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MEDIUM ACCESS CONTROL LAYER
Biomimetic Underwater Robot, Robolobster
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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)

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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

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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

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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)

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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

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NETWORK LAYER
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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

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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

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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 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

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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

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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

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TRANSPORT LAYER
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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

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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

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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

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Clusters in Mobile Ad hoc Networks
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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

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Clusters in Mobile Ad hoc Networks (Cont)

• Problems
• Hidden Terminal problem
• Exposed Terminal problem

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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

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Challenge

• Minimum Cut problem applied to UW-ASN (Network
  layer)
• To reduce interference

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References

• I. F. Akyildiz, D. Pompili, and T. Melodia.
  Underwater Acoustic Sensor Networks Research
  Challenges. Ad Hoc Networks (Elsevier), vol.
  3(3), pp. 257279, 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. WUWNet06, September 25, 2006.
• Ian F. Akyildiz, Dario Pompili, and Tommaso
  Melodia. State of the Art In Protocol Research
  for Underwater Acoustic Sensor Networks.
  WUWNet06, September 25, 2006.

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Questions