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Routing/Data Dissemination in Wireless Sensor Networks

Presented by

Kalyani Komarasetti

Computer Science, WMU

Spring 2004

Outline! Introduction! Flooding! Gossiping! SPIN! Shortest Path Minded SPIN Protocol! Directed Diffusion! LEACH! TTDD! SER! Romer’s Algorithm! Comparison of routing protocols! Conclusion

Wireless Sensor Network

! A wireless sensor network refers to a group of sensors, or nodes, linked by a wireless medium to perform distributed sensing tasks

• How Sensor Networks differ from Traditional Networks?

–sensor networks have severe energy constraints

–redundant low-rate data

–many-to-one flows

–sensor networks are data-centric, unlike traditional networks which are address-centric

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Communication Architecture

Internet and Satellite

Sink

Task managernode

User

Sensor nodesSensor field

A

B

CDE

Design Factors

! Fault Tolerancethe ability to sustain sensor network functionalities without any interruption due to sensor node failures because of lack of power, physical damage, or environmental interference.

! Scalabilitythe density of sensor nodes can range from few sensor nodes to few hundred sensor nodes in a region.

! Production Coststhe cost of sensor node should be much less than $1 in order for the sensor network to be feasible

! Environmentcan work in different environments.

! Transmission Medialinks between nodes can be formed by radio, infrared, or optical media.

! Power Consumptionbattery lifetimedesign of power-aware protocols and algorithmsPower consumption: sensing, communication, and data processing

Continue.. Design Factors

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Why Separate Routing Protocols?

! Traditional routing protocols cannot be used for sensor networks as they focus on avoiding congestion or maintaining connectivity when faced with mobility and not on limited energy supply

! Challenges! Energy-limited nodes! Computation

! Aggregate data! Suppress redundant information

! Communication! Bandwidth limited

Routing Techniques (Network Layer)

! Flooding! Send data to all neighbors! The receiving node stores a copy of data and sends a copy to all

its neighbors

B

D E

F

C

A

Conventional Approach

Limitations:–Implosion: Occurs when a node sends data to its neighbors, regardless of whether or not the neighbor has already received it–Overlap: Occurs when sensor nodes cover overlapping geographical area (wastage of energy and bandwidth)–Resource Blindness: Occurs when nodes do not modify their activities based on the amount of energy available to them at a give time

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Implosion

A

B C

D

(a)

(a)

(a)

(a)

A B

C (r,s)(q,r)

q sr

Data overlap

•Gossiping -- Each node floods all its data to one, randomly selected neighbor.

Resource Inefficiencies

Sensor Protocol for Information via Negotiation (SPIN)

! It incorporates negotiation and resource-adaptation to overcome the limitations of classic flooding

! Negotiation: Nodes negotiate with each other before transmitting data to ensure that only useful information is transferred

! eliminates implosion and overlap

! Achieved by naming the data descriptors (meta-data)

! Resource-Adaptation: Each node has its own resource manager which keeps track of resource consumption

! Nodes poll before data transmission

SPIN-1! It is a 3-stage protocol

! Nodes use 3 types of messages to communicate:! ADV - To advertise new data

! REQ - To request for data

! DATA – for actual message

! Advantages:! Simple

! Each node performs little decision making, therefore wastes little energy in computation

! Each node only needs to know about its single-hop network neighbors

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SPIN-1: Example

B

AADVREQDATAA

DVADV

ADV

AD

V ADV

REQ

REQ

RE

Q

REQ

DA

TA

DATA

DA

TA

DATA

I already have data, I don’t

need it

SPIN-2

! Extension to SPIN-1

! Incorporates threshold-based resource-awareness mechanism in addition to negotiation

! Each node decides its participation depending on the energy level ! If plenty, acts as SPIN-1 node

! if approaches low-energy threshold, it reduces its participation in protocol (This does not prevent a node in spending energy on ADV or REQ messages when goes below its low-energy threshold, but prevents from handling DATA message)

Shortest Path Minded SPIN Protocol

C

B

A

1

3

1

In original SPIN, A will send data to both of them with a total link cost of 1+3=4

With SPMS, the total link cost is 1+1=2

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Directed Diffusion

! It uses gradient based approach

! Used in networks where nodes coordinate to perform distributed sensing of environmental phenomenon

! Characteristics:

! data-centric (data generated by sensor nodes is named by attribute-value pair)

! application-aware (Enables to achieve energy savings by selecting good paths and robustness by caching and processing data in network)

Elements of Directed Diffusion! Naming

! Data is named using attribute-value pairs ! Interests

! A node requests data by sending interests for named data! Gradients (data rate, duration, direction…)

! Gradients is set up within the network to “draw” events, i.e. data matching the interest.

! Reinforcement! Sink reinforces particular neighbors to draw higher quality

( higher data rate) events

Directed Diffusion-Example

! TASK: Animal Tracking! Interest: Named Task Descriptor i.e., attribute-value pair that

describes the data ! It contains a timestamp field and several gradient fields

RequestRequest

Interest ( Task ) DescriptionType = four-legged animalInterval = 20 msDuration = 1 minuteLocation = [-100, -100; 200, 400]

Node dataType =four-legged animalInstance = elephantLocation = [125, 220]Confidence = 0.85Time = 02:10:35

ReplyReply

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Directed Diffusion (Cont…)

! The sink periodically broadcasts interest, which is a named taskdescriptor, to all sensors

! Each sensor node then stores the interest entry in its cache.! As the interest propagates throughout the network, the gradients

from source back to sink are setup! When the source has data for the interest, the source sends data

along the interest’s gradient path

! Advantage: Interest, data propagation and data aggregation are determined by localized interactions i.e., through messages exchanged between neighbors or nodes within some vicinity

Source

Sink

Interest = InterrogationGradient = Who is interested(data rate , duration, direction)

Setting Up Gradient

Neighbor’s choices :1. Flooding 2. Geographic routing3. Cache data to direct interests

Source

Sink

Reinforcing the Best Path

Low rate event Reinforcement = Increased interest

The neighbor reinforces a path:1. At least one neighbor2. Choose the one from whom it first received the latest event (low delay)3. Choose all neighbors from which new events were recently received

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Low-Energy Adaptive Clustering Hierarchy (LEACH)

! It is a clustering-based protocol

! Cluster heads are randomly selected and rotated (evenly distribute the load among the sensors in the network)

! Incorporates data fusion into routing protocol to reduce the amount of information to be transmitted to base station

! Operation of LEACH is separated into 2 phases

! Setup phase

! Steady state phase

LEACH (Cont…)

! Setup Phase: Cluster head selection! Node n chooses random number, s, between 0 and 1! If s is less than a threshold T(n), node n becomes a cluster head

in current round! Cluster heads broadcast an advertisement message to non-cluster

nodes who then decide to which cluster they want to belong to (generally based on signal strength of the advertisement)

! Cluster head then sends a TDMA schedule to members

LEACH (Cont..)

! Steady state phase:! Nodes begin sensing data and transmitting to cluster heads

! Cluster head aggregates and sends directly to sink

! After certain time, network goes back to setup phase

! Each cluster communicate using CDMA codes to reduce interference from nodes belonging to other clusters

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LEACH (Cont..)

! Advantages: Scalable and energy efficient

! Challenges:! How to dynamically use the right number of cluster heads?

! What if cluster heads fail?

! Can it be extended to multiple levels of hierarchy?

! Extension of LEACH (LEACH with negotiation)! Negotiates using meta-data as in SPIN to ensure that only data the

provides new information is transmitted to the cluster-head

TTDD: A Two-tier Data Dissemination Model for Large-scale Wireless Sensor

Networks! Fixed source and sensor nodes, mobile or stationary sinks

! nodes densely applied in large field

! Position-aware nodes, sinks not necessarily

! Once a stimulus appears, sensors surrounding it collectively process signal, one becomes the source to generate the data report

! Efficient and effective in supporting mobile sinks

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Sensor Network Model

SourceStimulus

Sink

Sink

Mobile SinkExcessive PowerConsumption

Increased WirelessTransmissionCollisions

State MaintenanceOverhead

Grid setup

! Source proactively divide the plane into αXα square cells, with itself at one of the crossing point of the grid.

! The source calculates the locations of its four neighboring dissemination points

! The source sends a data-announcement message to reach these neighbors using greedy geographical forwarding

! The node serving the point is called dissemination node

! This continues…

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TTDD Basics

Source

Dissemination Node

Sink

Data Announcement

Query

Data

Immediate DisseminationNode

TTDD Mobile Sinks

Source

Dissemination Node

Sink

Data Announcement

Data

Immediate DisseminationNode

Immediate DisseminationNode

TrajectoryForwarding

TrajectoryForwarding

TTDD Multiple Mobile Sinks

Source

Dissemination Node

Data Announcement

Data

Immediate DisseminationNode

TrajectoryForwarding

Source

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Grid Maintenance

Source

Dissemination Node

Data

Immediate DisseminationNode

X

Geography-Based Routing (for mobile ad-hoc networks)

! routes packets of data in an ad hoc digital radio-communication network on the basis of the current geographical positions of all the network nodes.

(1) the nodes are equipped with Global Positioning System receivers to determine their positions, (2) the nodes contain environmental sensors, and (3) the main purpose is to collect sensory data and relay them to a central node designated as home.

! Advantages:! does not require the maintenance of a routing table

! does not require the discovery of a route from a specific source node to a specific destination node

Stream Enabled Routing (SER)

! The routing protocol requires the sink to specify the sensor nodes that perform the tasks in their instructions.

! If the nodes do not have global positioning system (GPS), then they can use a location awareness protocol.

! It can be integrated with the application layer as it is based on instructions or tasks.

! Instead of assigning attributes to a task, an instruction is predefined as an identifier value. This way only the identifier is sent and not the whole-attribute list in order to conserve memory.

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Romer’s Algorithm

! Multipath routing algorithm described by Romer is 20 times more energy efficient than algorithms implemented in classical distributed systems

! The algorithm starts by discovering multiple paths from the source to destination, which are calculated based on reputation coefficient of the nodes (a coefficient that shows the way a specific node behaved in the past)

! One solution to node failure is to send same data over multiple paths, but requires large quantities of network resources (like bandwidth)

! Another solution to to split data into several pieces and send these parts

Romer’s Algorithm (Cont…)

! Romer’s solution to construct multipaths:! A main path is constructed by arranging all the source nodes, the

intermediate nodes and the destination nodes in a ring (using shortest path considerations)

! Splitting the ring into two half-rings gives us already two paths from source to destination. More paths can be constructed by diving each half-ring into several segments.

! Advantage: Assures 95 to 100% of the message delivery even in high mobility, with a routing packet overhead of 1% of the totalpackets sent.

Comparison of routing Algorithms

Cluster-head selectionGoodQuite FastLEACH

OK:Four neighbor, Constant

Reasonablelocal flooding+ reasonable aggregation

Very Fast TTDD

Complex:Neighbor X Interest

Higher than TTDD global flooding + strong aggregation

Quite Fast Directed Diffusion

Data- neighbor pairsHigher than aboveVery Fast SPIN

NoneLowest Random walk

Slowest Gossiping

Small, upstreamLow b/cImplosionFastest Flooding

State complexityEnergy Efficiency(data/energy ratio)Data Efficiency

Attributes

Algo.

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Conclusion

! MAIN Routing Algorithms:! SPIN: It addresses flooding by negotiation and resource adaptation. Operates

more efficiently and conserve energy by sending data that describe the sensor data, called meta-data, instead of sending all the data

! Directed Diffusion: It is a data-centric paradigm which uses query disseminating and processing

! LEACH: It is a clustering based energy-efficient communication protocol where the cluster membership and cluster-head is changed randomly. The cluster-head collects and aggregates information from sensors in its owncluster and passes in information to the sink

References! “Modelling Data-Centric Routing in Wireless Sensor Networks”,Bhaskar

Krishnamachari, Deborah Estrin, Stephen Wicker, IEEE INFOCOM 2002

! “Directed Diffusion: A Scalable and Robust Communication Paradigm for Sensor

Networks”, Chalermek Intanagonwiwat, Ramesh Govindan and Deborah Estrin, In

Proceedings of the Sixth Annual International Conference on Mobile Computing

and Networks (MobiCOM 2000), August 2000, Boston, Massachusetts.

! “Adaptive protocols for information dissemination in wireless sensor networks",

Wendi Rabiner Heinzelman, Joanna Kulik, Hari Balakrishnan, In Proc. 5th

ACM/IEEE Mobicom Conference, Seattle, WA, August 1999.

! “Energy-efficient Communication Protocols for Wireless Microsensor Networks,"

Wendi Rabiner Heinzelman, Anantha Chandrakasan, Hari Balakrishnan, Proc.

Hawaii Int'l Conf. on Systems Science, January 2000.

References (Cont…)! “Data Dissemination Protocol in Sensor Networks to Tolerate Node and

Link failures”, Gunjan Khanna, Yu-Sung Wu

! “A Stream Enabled Routing (SER) Protocol for Sensor Networks”,

F. Akyildiz, W. Su, Med-hoc-Net 2002, Sardegna, Italy, September

2002. (Review Due: 01/27/03)

! “Highly Resilient, Energy Efficient Multipath Routing in Wireless Sensor

Networks”, D. Ganesan, R. Govindan, S. Shenker and D. Estrin,

Mobile Computing and Communications Review (MC2R) Vol 1., No. 2.

2002.

! “Topology Control Protocols to Conserve Energy in Wireless Ad Hoc

Networks”, Ya Xu, Solomon Bien, Yutaka Mori, John Heidemann, and

Deborah Estrin, CENS Technical Report 0006, UCLA, Jan 2003.

! “ASCENT: Adaptive Self-Configuring Sensor Network Topologies”,

Alberto Cerpa and Deborah Estrin, University of California Los Angeles,

Feb 2001.

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Thank You !!!