state of the art in protocol research for underwater acoustic sensor networks (uw-asns) date : 2007....

State of the Art in Protocol Research for State of the Art in Protocol Research for UnderWater Acoustic Sensor NetworksUnderWater Acoustic Sensor Networks

(UW-ASNs)(UW-ASNs)

Date : 2007. 11. 22 (Date : 2007. 11. 22 ( 木木 ))

Name : Jeong-Chun, Joo.Name : Jeong-Chun, Joo.

2006, ACM_WUWNet'062006, ACM_WUWNet'06Ian F. Akyildiz, Dario Pompili, and Tommaso Melodia

Georgia Institute of Technology

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

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IntroductionIntroduction



Applications (1/2)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)

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Applications (2/2)Applications (2/2)

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Underwater NetworksUnderwater 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

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Challenges in design of UW-ASNsChallenges in design of UW-ASNs

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

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Communication ArchitectureCommunication Architecture



Communication ArchitectureCommunication 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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Static two-dimensional UW-ASNs (1/2)Static two-dimensional UW-ASNs (1/2)

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Comms. Intra clusters (using CH)

Comms with the surface station

anchored

Acoustic link comms

RF comms

Satellite comms



Static two-dimensional UW-ASNs (2/2)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

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Three-dimensional UW-ASNs (1/2)Three-dimensional UW-ASNs (1/2)

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anchored

RF comms

Satellite comms


Acoustic link comms



Three-dimensional UW-ASNs (2/2)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

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Sensor Networks with AUVSensor Networks with AUV

anchored

RF comms

Satellite comms


Acoustic link comms



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UW-ASN:DESIGN CHALLENGESUW-ASN:DESIGN CHALLENGES



UWSNs vs Terrestrial Sensor NetworksUWSNs 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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Acoustic Propagation in UWSNsAcoustic 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

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Influencing FactorsInfluencing 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 delayUnderwater = 5 x Radio Frequency(RF)ground

Doppler spread

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MEDIUM

ACCESS

CONTROL

LAYER



Multiple access techniquesMultiple 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)

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CSMA Based MAC ProtocolsCSMA 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

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CDMA-based MAC ProtocolsCDMA-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

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Open research issuesOpen 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

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NETWORK LAYERNETWORK LAYER



existing routing protocols (1/3)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

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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

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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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Routing Protocols for UW-ASNs (1/3)Routing Protocols for UW-ASNs (1/3)

VBF (Vector-Based Forwarding)(’06.5) Location-based routing protocol

Only nodes in routing pipe forward messages

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Virtual circuit routing technique (’06.6) 1st phase : Centralized Routing Problem

determine optimal node-disjoint primary and backup multihop data

paths

2nd phase : Localized Network Restoration

Guarantee survivability of the network to node and link failures

by locally repairing paths

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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

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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

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TRANSPORT LAYERTRANSPORT LAYER



Transport protocol of UW-ASNsTransport 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- - 3333 / 38 - / 38 -



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Requirement of a transport layer for Requirement of a transport layer for UW-ASNsUW-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



SDRT SDRT (Segmented Data Reliable Transport)(’06)(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.- - 3535 / 38 - / 38 -




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

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ConclusionsConclusions

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

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QuestionsQuestions

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state of the art in protocol research for underwater acoustic sensor networks (uw-asns) date : 2007....

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