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UNDERWATER ACUSTIC SENSOR NETWORKS UWASNs

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Title: UNDERWATER ACUSTIC SENSOR NETWORKS UWASNs


1
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

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 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

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-ASNDESIGN 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 delayUnderwater5 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 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

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
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. 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.

45
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