Data Dissemination and Fusion In Sensor Networks

Data Dissemination and Fusion

In Sensor Networks

The need for Data Dissemination and Fusion

– Energy efficiency is an essential factor; therefore, short-range hop-by-Energy efficiency is an essential factor; therefore, short-range hop-by-hop communication is preferred over direct long-range communication hop communication is preferred over direct long-range communication to the destinationto the destination

– Since sensor network contains large amount of data for the end user, Since sensor network contains large amount of data for the end user, methods of combining or aggregating data into small set of information methods of combining or aggregating data into small set of information is necessary and contributes to energy savingsis necessary and contributes to energy savings

– Data aggregation (aka data fusion) can combine unreliable data Data aggregation (aka data fusion) can combine unreliable data readings to produce accurate signal by improving the common signal readings to produce accurate signal by improving the common signal and reducing the noiseand reducing the noise

– LEACHLEACH (Low-Energy Adaptive Clustering Hierarchy) is a clustering-based (Low-Energy Adaptive Clustering Hierarchy) is a clustering-based

protocol that utilizes the randomized rotation of local cluster base stations protocol that utilizes the randomized rotation of local cluster base stations

to evenly distribute the energy load within the network of sensorsto evenly distribute the energy load within the network of sensors

– It is a distributed, does not require any control information from base station It is a distributed, does not require any control information from base station

(BS) and the nodes do not need to have knowledge of global network for (BS) and the nodes do not need to have knowledge of global network for

LEACH to functionLEACH to function

– The energy saving of LEACH is achieved by combining compression with The energy saving of LEACH is achieved by combining compression with

data routingdata routing

– Key features of LEACH include:Key features of LEACH include:

Localized coordination and control of cluster set-up and operationLocalized coordination and control of cluster set-up and operation

Randomized rotation of the cluster base stations or clusterheads and their Randomized rotation of the cluster base stations or clusterheads and their

clustersclusters

Local compression of information to reduce global communicationLocal compression of information to reduce global communication

Energy-Efficient Communication Protocol Architecture for Wireless Microsensor Networks (LEACH Protocol)[Heinzelman+ 2000, 2002]

– Considered microsensor network has the following characteristics:Considered microsensor network has the following characteristics:

The base station is fixed and located far from the sensorsThe base station is fixed and located far from the sensors

All the sensor nodes are homogeneous and energy constrainedAll the sensor nodes are homogeneous and energy constrained

– Communication between sensor nodes and the base station is expensive and no Communication between sensor nodes and the base station is expensive and no

high energy nodes exist to achieve communicationhigh energy nodes exist to achieve communication

– By using clusters to transmit data to the BS, only few nodes need to transmit for By using clusters to transmit data to the BS, only few nodes need to transmit for

larger distances to the BS while other nodes in each cluster use small transmit larger distances to the BS while other nodes in each cluster use small transmit

distancesdistances

– LEACH achieves superior performance compared to classical clustering algorithms LEACH achieves superior performance compared to classical clustering algorithms

by using adaptive clustering and rotating clusterheads; assisting the total energy of by using adaptive clustering and rotating clusterheads; assisting the total energy of

the system to be distributed among all the nodesthe system to be distributed among all the nodes

– By performing load computation in each cluster, amount of data to be transmitted to By performing load computation in each cluster, amount of data to be transmitted to

BS is reduced. Therefore, large reduction in the energy dissipation is achieved BS is reduced. Therefore, large reduction in the energy dissipation is achieved

since communication is more expensive than computationsince communication is more expensive than computation

LEACH

Algorithm OverviewAlgorithm Overview

– The nodes are grouped into local clusters with one node acting as the local base The nodes are grouped into local clusters with one node acting as the local base

station (BS) or clusterhead (CH)station (BS) or clusterhead (CH)

– The CHs are rotated in random fashion among the various sensorsThe CHs are rotated in random fashion among the various sensors

– Local data fusion is achieved to compress the data being sent from clusters to the Local data fusion is achieved to compress the data being sent from clusters to the

BS; resulting the reduction in the energy dissipation and increase in the network BS; resulting the reduction in the energy dissipation and increase in the network

lifetimelifetime

– Sensor elect themselves to be local BSs at any any given time with a certain Sensor elect themselves to be local BSs at any any given time with a certain

probability and these CHs broadcast their status to other sensor nodesprobability and these CHs broadcast their status to other sensor nodes

– Each node decided which CH to join based on the minimum communication energyEach node decided which CH to join based on the minimum communication energy

– Upon clusters formation, each CH creates a schedule for the nodes in its cluster Upon clusters formation, each CH creates a schedule for the nodes in its cluster

such that radio components of each non-clusterhead node need to be turned OFF such that radio components of each non-clusterhead node need to be turned OFF

always except during the transmit timealways except during the transmit time

– The CH aggregates all the data received from the nodes in its cluster before The CH aggregates all the data received from the nodes in its cluster before

transmitting the compressed data to BStransmitting the compressed data to BS

LEACH

Algorithm OverviewAlgorithm Overview

– The transmission between CH and BS requires high energy transmissionThe transmission between CH and BS requires high energy transmission

– In order to evenly distribute energy usage among the sensor nodes, clusterheads In order to evenly distribute energy usage among the sensor nodes, clusterheads

are self-elected at different time intervalsare self-elected at different time intervals

– The nodes decides to become a CH depending on the amount of energy it has leftThe nodes decides to become a CH depending on the amount of energy it has left

– The decisions to become CH are made independently of the other nodesThe decisions to become CH are made independently of the other nodes

– The system can determine the optimal number of CHs prior to election procedure The system can determine the optimal number of CHs prior to election procedure

based on parameters such as network topology and relative costs of computation based on parameters such as network topology and relative costs of computation

vs. communication (Optimal number of CHs considered is 5% of the nodes)vs. communication (Optimal number of CHs considered is 5% of the nodes)

– It has been observed that nodes die in a random fashionIt has been observed that nodes die in a random fashion

– No communication exists between CHsNo communication exists between CHs

– Each node has same probability to become a CHEach node has same probability to become a CH

LEACH

Algorithm DetailsAlgorithm Details

– The operation of LEACH is achieved by The operation of LEACH is achieved by roundsrounds

– Each round begins with a set-up phase (clusters are selected) followed by steady-Each round begins with a set-up phase (clusters are selected) followed by steady-

state phase (data transmission to BS occurs)state phase (data transmission to BS occurs)

1.1. Advertisement Phase: Advertisement Phase:

– Initially, each node need to decide to become a CH for the current round based Initially, each node need to decide to become a CH for the current round based

on the suggested percentage of CHs for the network (set prior to this phase) on the suggested percentage of CHs for the network (set prior to this phase)

and the number times the node has acted as a CHand the number times the node has acted as a CH

– The node (n) decides by choosing a random number between 0 and 1The node (n) decides by choosing a random number between 0 and 1

– If this random number is less than T(n), the nodes become a CH for this roundIf this random number is less than T(n), the nodes become a CH for this round

– The threshold is set as follows:The threshold is set as follows:

LEACH

1P

P

1 – P * (rmod )

0 Otherwise T(n) =

If n C G P = desired percentage of CHsr = current roundG = set of nodes that have not been CHs in the last 1/P rounds


1. Advertisement Phase: 1. Advertisement Phase:

– Assumptions are (i) each node starts with the same amount of energy and (ii) Assumptions are (i) each node starts with the same amount of energy and (ii)

each CHs consumes relatively same amount of energy for each nodeeach CHs consumes relatively same amount of energy for each node

– Each node elected as CH broadcasts an advertisement message to the restEach node elected as CH broadcasts an advertisement message to the rest

– During this “clusterhead-advertisement” During this “clusterhead-advertisement” phase, the non-clusterhead nodes phase, the non-clusterhead nodes

hear the ads of all CHs and decide which CH to joinhear the ads of all CHs and decide which CH to join

– A node joins to a CH in which it hears with its advertisement with the A node joins to a CH in which it hears with its advertisement with the highest highest

signal strengthsignal strength

2. Cluster Set-Up Phase:2. Cluster Set-Up Phase:

– Each node informs its clusterhead that it will be member of the clusterEach node informs its clusterhead that it will be member of the cluster

3. Schedule Creation:3. Schedule Creation:

– Upon receiving all the join messages from its members, CH creates a TDMA Upon receiving all the join messages from its members, CH creates a TDMA

schedule about their allowed transmission time based on the total number of schedule about their allowed transmission time based on the total number of

members in the clustermembers in the cluster

LEACH


4. Data Transmission: 4. Data Transmission:

– Each node starts data transmission to their CH based on their TDMA scheduleEach node starts data transmission to their CH based on their TDMA schedule

– The radio of each cluster member nodes can be turned OFF until their The radio of each cluster member nodes can be turned OFF until their

allocated transmission time comes; minimizing the energy dissipationallocated transmission time comes; minimizing the energy dissipation

– The CH nodes must keep its receiver ON to receive all the dataThe CH nodes must keep its receiver ON to receive all the data

– Once all the data is received, the CH compresses the data to send it to BSOnce all the data is received, the CH compresses the data to send it to BS

Multiple ClustersMultiple Clusters

– In order to minimize the radio interference between nearby clusters, each CH In order to minimize the radio interference between nearby clusters, each CH

chooses randomly from a list of spreading CDMA codes and it informs its chooses randomly from a list of spreading CDMA codes and it informs its

cluster members to transmit using this codecluster members to transmit using this code

– The neighboring CHs radio signals will be filtered out to avoid corruption in the The neighboring CHs radio signals will be filtered out to avoid corruption in the

transmissiontransmission

LEACH

LEACH

Advantages:Advantages:

– Localized coordination to enable scalability, and robustness for dynamic Localized coordination to enable scalability, and robustness for dynamic

networksnetworks

– Incorporates data fusion into the routing protocol in order to reduce the Incorporates data fusion into the routing protocol in order to reduce the

amount of information transmitted to BSamount of information transmitted to BS

– Distributes energy dissipation evenly throughout the sensors, thus increasing Distributes energy dissipation evenly throughout the sensors, thus increasing

the system lifetime of the networkthe system lifetime of the network

LEACH

Disadvantages:Disadvantages:

– How to decide the percentage of cluster heads for a network? The topology, How to decide the percentage of cluster heads for a network? The topology,

density and number of nodes of a network could be different from other networksdensity and number of nodes of a network could be different from other networks

– No suggestions about when the re-election needs to be invokedNo suggestions about when the re-election needs to be invoked

– The clusterheads farther away from the base station will use higher power and die The clusterheads farther away from the base station will use higher power and die

more quickly than the nearby onesmore quickly than the nearby ones

LEACH

Suggestions/Improvements/Future Work:Suggestions/Improvements/Future Work:

– Extensions can be included to have hierarchical clustering where each CH Extensions can be included to have hierarchical clustering where each CH

will communicate with “super-clusterhead” until the top layer of hierarchy in will communicate with “super-clusterhead” until the top layer of hierarchy in

which the data needs to be sent to BSwhich the data needs to be sent to BS

– The degree and remaining energy of a node may be considered as The degree and remaining energy of a node may be considered as

parameters to decide a clusterhead in a round. If a clusterhead with a limited parameters to decide a clusterhead in a round. If a clusterhead with a limited

power used up its power in a round, the data to be transmitting may be lostpower used up its power in a round, the data to be transmitting may be lost

– Since TDMA schedule is used, a large delay may be introduced between Since TDMA schedule is used, a large delay may be introduced between

event detection and notification at base station. Therefore, the protocol is not event detection and notification at base station. Therefore, the protocol is not

suitable for a real-time applicationsuitable for a real-time application

– SPINSPIN (Sensor Protocols for Information via Negotiation) is a family of (Sensor Protocols for Information via Negotiation) is a family of

negotiation-based information dissemination protocols which is designed to negotiation-based information dissemination protocols which is designed to

address the deficiencies of classic flooding by address the deficiencies of classic flooding by negotiationnegotiation and and resource-resource-

adaptationadaptation

– SPIN disseminates each sensor readings to all sensors in the network, SPIN disseminates each sensor readings to all sensors in the network,

treating all sensors as potential sink nodestreating all sensors as potential sink nodes

– Nodes using SPIN protocols names their data using high-level data Nodes using SPIN protocols names their data using high-level data

descriptors, called meta-data and usage of meta-data negotiations descriptors, called meta-data and usage of meta-data negotiations

eliminate transmission of redundant data in the networkeliminate transmission of redundant data in the network

– Communication decisions can be based upon both application-specific Communication decisions can be based upon both application-specific

knowledge of the data and knowledge of the resources available to nodesknowledge of the data and knowledge of the resources available to nodes

Negotiation-Based Protocols for Disseminating Information in Wireless Sensor Networks (SPIN Protocols)[Kulik+ 2002]

– SPIN has two basic ideas:SPIN has two basic ideas:

Operate efficiently and conserve energy: Operate efficiently and conserve energy: communicate with each other communicate with each other

about the sensor data received already and the data needed stillabout the sensor data received already and the data needed still

Monitor and adapt changes in their own energy resources:Monitor and adapt changes in their own energy resources: extend the extend the

lifetime of the systemlifetime of the system

– Four difference SPIN protocols:Four difference SPIN protocols:

SPIN-PPSPIN-PP

SPIN-ECSPIN-EC

SPIN-BCSPIN-BC

SPIN-RLSPIN-RL

Meta DataMeta Data

– Used to uniquely and completely describe the data being collected by sensorsUsed to uniquely and completely describe the data being collected by sensors

– If two pieces of actual data are distinguishable, then their meta-data should also If two pieces of actual data are distinguishable, then their meta-data should also

be distinguishablebe distinguishable

– Since the format of meta-data is application-specific, each application needs to Since the format of meta-data is application-specific, each application needs to

interpret and synthesize its own meta-datainterpret and synthesize its own meta-data

SPIN

Meta DataMeta Data

– SPIN applications must define a meta-data format for representing data that SPIN applications must define a meta-data format for representing data that

concerns with the costs of storing, retrieving and managing the meta-dataconcerns with the costs of storing, retrieving and managing the meta-data

– SPIN nodes uses three types of communication messages:SPIN nodes uses three types of communication messages:

ADVADV (new data advertisement) (new data advertisement)

REQREQ (request for data) (request for data)

DATA DATA (data message)(data message)

– ADV and REQ messages contain only meta-data that is smaller than the DATA ADV and REQ messages contain only meta-data that is smaller than the DATA

messagemessage

SPIN Resource ManagementSPIN Resource Management

– SPIN applications are resource-aware and resource-adaptiveSPIN applications are resource-aware and resource-adaptive

– By knowing the resources at hand, the nodes makes informed decisions about By knowing the resources at hand, the nodes makes informed decisions about

using their resources effectivelyusing their resources effectively

– SPIN specifies an interface that applications can use to find out their available SPIN specifies an interface that applications can use to find out their available

resources rather than specifying a specific energy management protocolsresources rather than specifying a specific energy management protocols

SPIN

The ProblemThe Problem

– In conventional classic flooding, the source nodes sends data to all its neighbors In conventional classic flooding, the source nodes sends data to all its neighbors

and the neighbors check their record of already sent data to see if they have and the neighbors check their record of already sent data to see if they have

forwarded the data to their neighbors. If not, they forward the data and update forwarded the data to their neighbors. If not, they forward the data and update

the recordthe record

– This requires small amount of protocol state at any node, disseminates data This requires small amount of protocol state at any node, disseminates data

quickly in the network where neither the bandwidth is scarce and the links are quickly in the network where neither the bandwidth is scarce and the links are

error proneerror prone

– The problems include: The problems include: implosionimplosion, , overlapoverlap and and resource blindnessresource blindness

Implosion:Implosion: A node always sends data to its neighbors without being concerned aboutA node always sends data to its neighbors without being concerned about

if the same data has been received by the neighbors from other nodesif the same data has been received by the neighbors from other nodes

Overlap:Overlap: The nodes waste energy and bandwidth by sending the overlapping dataThe nodes waste energy and bandwidth by sending the overlapping data

Resource Blindness:Resource Blindness: Nodes do not make decisions based on the energy available Nodes do not make decisions based on the energy available

SPIN

The SolutionThe Solution

– SPIN provides solution to the problems of implosion and overlap by negotiating SPIN provides solution to the problems of implosion and overlap by negotiating

with each other before transmitting data eliminates the transmission of with each other before transmitting data eliminates the transmission of

redundant dataredundant data

– Nodes poll their resources before transmitting or processing data by probing the Nodes poll their resources before transmitting or processing data by probing the

resource manager which keeps track of the resource consumptionresource manager which keeps track of the resource consumption

– Nodes can make efficient decisions based on the available energy levelNodes can make efficient decisions based on the available energy level

– The use meta-data descriptors eliminates the possibility of overlap since the The use meta-data descriptors eliminates the possibility of overlap since the

nodes can name the part of the data the nodes are interested in receivingnodes can name the part of the data the nodes are interested in receiving

– Resource-awareness of local resources allow sensors to make meaningful Resource-awareness of local resources allow sensors to make meaningful

decisions to extend longevitydecisions to extend longevity

SPIN

SPIN ProtocolsSPIN Protocols

1. SPIN-PP: A Three–stage handshake protocol for point-to-point media1. SPIN-PP: A Three–stage handshake protocol for point-to-point media

– This protocol works in three stages (ADV-REQ-DATA) with each stage This protocol works in three stages (ADV-REQ-DATA) with each stage

corresponding to one of the messagescorresponding to one of the messages

– The node sends ADV message to its neighborsThe node sends ADV message to its neighbors

– Neighbors check to see if they already have received or requested this dataNeighbors check to see if they already have received or requested this data

– If not, the neighbors respond by sending REQ message to the sender If not, the neighbors respond by sending REQ message to the sender

– The sender responds to the REQ message sent by sending the actual DATA to The sender responds to the REQ message sent by sending the actual DATA to

the neighbors requesting the datathe neighbors requesting the data

– If the neighbor already has the advertised data, it does not send any messageIf the neighbor already has the advertised data, it does not send any message

– Simplicity is the main strength, meaning that nodes make simple decisions, Simplicity is the main strength, meaning that nodes make simple decisions,

resulting in usage of small energy in computationresulting in usage of small energy in computation

– Each node only needs to know about its one hop neighborsEach node only needs to know about its one hop neighbors

SPIN


2. SPIN-EC: SPIN-PP with low-energy threshold2. SPIN-EC: SPIN-PP with low-energy threshold

– Adds simple energy-conservation heuristic to the SPIN-PP protocolAdds simple energy-conservation heuristic to the SPIN-PP protocol

– When energy is abundant, SPIN-EC acts as SPIN-PP protocolWhen energy is abundant, SPIN-EC acts as SPIN-PP protocol

– Whenever energy comes close to low-energy threshold, it adapts by reducing its Whenever energy comes close to low-energy threshold, it adapts by reducing its

participationparticipation

– The node will only participate in the full protocol if it believes that it has enough The node will only participate in the full protocol if it believes that it has enough

energy to complete the protocol without reaching below the threshold valueenergy to complete the protocol without reaching below the threshold value

– It does not prevent nodes from receiving messages such as ADV or REQ below It does not prevent nodes from receiving messages such as ADV or REQ below

its low-energy threshold, but prevents the nodes to handle a DATA message its low-energy threshold, but prevents the nodes to handle a DATA message

below the thresholdbelow the threshold

SPIN


3. SPIN-BC: A Three–stage handshake protocol for broadcast media3. SPIN-BC: A Three–stage handshake protocol for broadcast media

– Improves upon SPIN-PP for broadcast networks by using cheap, one-to-many Improves upon SPIN-PP for broadcast networks by using cheap, one-to-many

communications, meaning that all messages are sent to broadcast address and communications, meaning that all messages are sent to broadcast address and

processed by all the nodes that are within transmission range of the senderprocessed by all the nodes that are within transmission range of the sender

– This approach is often called This approach is often called broadcast-message-suppressionbroadcast-message-suppression

– SPIN-BC has three main differences from SPIN-PP are:SPIN-BC has three main differences from SPIN-PP are: All SPIN-BC nodes send their messages to the broadcast address such that all nodes All SPIN-BC nodes send their messages to the broadcast address such that all nodes

within the transmission range of sender will receive messagewithin the transmission range of sender will receive message

Upon receiving ADV message, each node checks to see if they already have the Upon receiving ADV message, each node checks to see if they already have the

data. If not, node sets a random timer to expire, uniformly chosen from a data. If not, node sets a random timer to expire, uniformly chosen from a

predetermined interval. After timer expires, the node sends an REQ message to the predetermined interval. After timer expires, the node sends an REQ message to the

broadcast address, including the original advertiser in the header of message. When broadcast address, including the original advertiser in the header of message. When

the nodes who are not original advertiser receive the REQ, they cancel their own the nodes who are not original advertiser receive the REQ, they cancel their own

request timers, preventing from sending out redundant copies of the same REQrequest timers, preventing from sending out redundant copies of the same REQ

The nodes will send out the requested data to the broadcast address only once to get The nodes will send out the requested data to the broadcast address only once to get

the data all its neighbors. It will not respond to multiple requests of the same datathe data all its neighbors. It will not respond to multiple requests of the same data

SPIN


4. SPIN-RL: SPIN-BC for lossy networks4. SPIN-RL: SPIN-BC for lossy networks

– Reliable version of SPIN-BC which disseminates data through a broadcast Reliable version of SPIN-BC which disseminates data through a broadcast

network even in the cases of network loses packets or communication is network even in the cases of network loses packets or communication is

asymmetricasymmetric

– Adds two adjustments to SPIN-BC to achieve reliability:Adds two adjustments to SPIN-BC to achieve reliability:

Each node maintains a record of which advertisements it hears from which Each node maintains a record of which advertisements it hears from which

nodes, and if does not receive the data within a set time after request, node nodes, and if does not receive the data within a set time after request, node

rerequests the datarerequests the data

Nodes limit the frequency with which they will resend the data, meaning Nodes limit the frequency with which they will resend the data, meaning

that it will wait for a set time before responding to any additional requests that it will wait for a set time before responding to any additional requests

for the same datafor the same data

SPIN

SPIN


– Meta-data negotiation and resource adaptationMeta-data negotiation and resource adaptation

– Maintains only local information about the nearest neighborsMaintains only local information about the nearest neighbors

– Suitable for mobile sensors since the nodes base their forwarding decisions Suitable for mobile sensors since the nodes base their forwarding decisions

on local neighborhood informationon local neighborhood information


– Study SPIN protocols in mobile wireless network modelsStudy SPIN protocols in mobile wireless network models

– Develop more sophisticated resource-adaptation protocols to use available Develop more sophisticated resource-adaptation protocols to use available

energy wellenergy well

– Design protocols that make adaptive decisions based not only on the cost of Design protocols that make adaptive decisions based not only on the cost of

communicating data, but also the cost of synthesizing it communicating data, but also the cost of synthesizing it


– It cannot isolate the nodes that do not want to receive information; It cannot isolate the nodes that do not want to receive information;

unnecessary power may be consumedunnecessary power may be consumed

– Motivated by scaling, robustness and energy efficiency requirementsMotivated by scaling, robustness and energy efficiency requirements

– Directed diffusion is Directed diffusion is data-centricdata-centric in that all communication is for in that all communication is for namednamed data data

– Data generated by sensor nodes is Data generated by sensor nodes is namednamed using attribute-value pairs using attribute-value pairs

– All nodes in the network are application-awareAll nodes in the network are application-aware

– A node requests data by sending A node requests data by sending interestsinterests for named data for named data

– A sensing task is disseminated via sequence of local interactions throughout A sensing task is disseminated via sequence of local interactions throughout

the sensor network as an the sensor network as an interestinterest for named data for named data

– Nodes diffusing the interest sets up their own Nodes diffusing the interest sets up their own cachescaches and and gradientsgradients within the within the

network to which channel the delivery of datanetwork to which channel the delivery of data

– During the data transmission,During the data transmission, reinforcement reinforcement and negative reinforcement are and negative reinforcement are

used to converge to efficient distributionused to converge to efficient distribution

– Intermediate nodes fuse interests, aggregate, correlate or cache dataIntermediate nodes fuse interests, aggregate, correlate or cache data

Directed Diffusion[Intanagonwiwat+ 2000]

– Assumes that sensor networks are task-specific – the task types are known at the Assumes that sensor networks are task-specific – the task types are known at the

time the sensor network is deployed time the sensor network is deployed

– An essential feature of directed diffusion is that interest, data propagation and An essential feature of directed diffusion is that interest, data propagation and

data aggregation are determined by data aggregation are determined by local interactionslocal interactions

– Focused on design of dissemination protocols for tasks and eventsFocused on design of dissemination protocols for tasks and events

Naming

– Task descriptions are Task descriptions are namednamed (specifies an interest for data matching the list of (specifies an interest for data matching the list of

attribute-value pairs) and also called as attribute-value pairs) and also called as interestinterest

– Example task: “Every Example task: “Every II ms, for the next ms, for the next TT seconds, send me a location of any seconds, send me a location of any

four-legged animal in subregion four-legged animal in subregion R R of the sensor field.”of the sensor field.”

task = four-legged animaltask = four-legged animal // detect animal location// detect animal location

interval = 20 msinterval = 20 ms // send back events every 20 ms// send back events every 20 ms

duration = 10 secondsduration = 10 seconds // … for the next 10 seconds// … for the next 10 seconds

rect = [-100, 100, 200, 400]rect = [-100, 100, 200, 400] // from sensors within rectangle// from sensors within rectangle

Directed Diffusion

Naming

– A sensor detecting an animal may generate the following data:A sensor detecting an animal may generate the following data:

task = four-legged animaltask = four-legged animal // type of animal seen// type of animal seen

instance = horseinstance = horse // instance of this type// instance of this type

location = [150, 200]location = [150, 200] // node location// node location

intensity = 0.5intensity = 0.5 // signal amplitude measure// signal amplitude measure

confidence = 0.85confidence = 0.85 // confidence in the match// confidence in the match

timestamp = 01:30:45timestamp = 01:30:45 // event generation time// event generation time

Interests and Gradients

– Interest is generally given by the sink nodeInterest is generally given by the sink node

– For each active task, sink periodically broadcasts an interest message to each of For each active task, sink periodically broadcasts an interest message to each of

its neighbors (including rect and duration attributes)its neighbors (including rect and duration attributes)

– Sink periodically refreshes each interest by sending re-sending the same interest Sink periodically refreshes each interest by sending re-sending the same interest

with monotonically increasing timestamp attribute for reliability purposeswith monotonically increasing timestamp attribute for reliability purposes

Directed Diffusion


– Every node maintains an interest cache where each item in the cache Every node maintains an interest cache where each item in the cache

corresponds to a corresponds to a distinctdistinct interest (different interest (different typetype, , intervalinterval attributes with disjoint attributes with disjoint

rectrect attributes) attributes)

– Interest entries in the cache do not contain information about the sinkInterest entries in the cache do not contain information about the sink

– In some cases, definition of distinct interests allows interest In some cases, definition of distinct interests allows interest aggregationaggregation

– The interest entry contains several The interest entry contains several gradientgradient fields, up to one per neighbor fields, up to one per neighbor

– When a node receives an interest, it determines if the interest exists in the cacheWhen a node receives an interest, it determines if the interest exists in the cache

1.1. If no matching exist, the node creates an interest entryIf no matching exist, the node creates an interest entry

This entry has single gradient towards the neighbor from which the This entry has single gradient towards the neighbor from which the

interest was received with specified data rateinterest was received with specified data rate

Individual neighbors can be distinguished by locally unique identifiersIndividual neighbors can be distinguished by locally unique identifiers

2.2. If the interest entry exists, but no gradient for the sender of interestIf the interest entry exists, but no gradient for the sender of interest

Node adds a gradient with the specified valueNode adds a gradient with the specified value

Updates the entry’s timestamp and duration fieldsUpdates the entry’s timestamp and duration fields

Directed Diffusion


3.3. If there exists both entry and a gradient, If there exists both entry and a gradient,

The node updates the entry’s timestamp and duration fieldsThe node updates the entry’s timestamp and duration fields

– When a gradient expires, it is removed from its interest entryWhen a gradient expires, it is removed from its interest entry

– When all gradients for an interest entry have expired, the interest entry is When all gradients for an interest entry have expired, the interest entry is

removed from the cacheremoved from the cache

– After receiving an interest, a node may re-send the interest to subset of its After receiving an interest, a node may re-send the interest to subset of its

neighborsneighbors

– To the neighbors, it may seem that interest originated from the sending node To the neighbors, it may seem that interest originated from the sending node

even though it may have been generated a distant sink. This represents a local even though it may have been generated a distant sink. This represents a local

interactioninteraction

– This way, interest diffuse throughout the network and not each interest have been This way, interest diffuse throughout the network and not each interest have been

sent to all the neighbors if a node sent matching interest recentlysent to all the neighbors if a node sent matching interest recently

– Gradient specifies data rate (value) and a direction in directed diffusion, whereas Gradient specifies data rate (value) and a direction in directed diffusion, whereas

the values can be used to probabilistically forward data in different paths in other the values can be used to probabilistically forward data in different paths in other

sensor networkssensor networks

Directed Diffusion

Data propagation

– Data message is unicast individually to the relevant neighborsData message is unicast individually to the relevant neighbors

– A node receiving a data message from its neighbors checks to see if matching A node receiving a data message from its neighbors checks to see if matching

interest entry in its cache exists according the matching rules describedinterest entry in its cache exists according the matching rules described

1.1. If no match exist, the data message is droppedIf no match exist, the data message is dropped

2.2. If match exists, the node checks its data cache associated with the matching If match exists, the node checks its data cache associated with the matching

interest entryinterest entry

If a received data message has a matching data cache entry, the data If a received data message has a matching data cache entry, the data

message is droppedmessage is dropped

Otherwise, the received message is added to the data cache and the Otherwise, the received message is added to the data cache and the

data message is re-sent to the neighborsdata message is re-sent to the neighbors

– Data cache keeps track of the recently seen data items, preventing loopsData cache keeps track of the recently seen data items, preventing loops

– By checking the data cache, a node can determine the data rate of the received By checking the data cache, a node can determine the data rate of the received

eventsevents

Directed Diffusion

Reinforcement

– After the sink starts receiving low data rate events, it After the sink starts receiving low data rate events, it reinforces reinforces one neighbor in one neighbor in

order to “draw down” higher quality (higher data rate) eventsorder to “draw down” higher quality (higher data rate) events

– This is achieved by data driven local rulesThis is achieved by data driven local rules

– To enforce a neighbor, the sink may re-send the original interest with higher data To enforce a neighbor, the sink may re-send the original interest with higher data

raterate

– When the data rate is higher than before, the node node must also reinforce at When the data rate is higher than before, the node node must also reinforce at

least one neighborleast one neighbor

– Reinforcement can be carried out from neighbors to other neighbors in a Reinforcement can be carried out from neighbors to other neighbors in a

particular path (i.e., if a path when a path delivers an event faster than others, particular path (i.e., if a path when a path delivers an event faster than others,

sink attempts to use this path to draw down high quality data)sink attempts to use this path to draw down high quality data)

– In Summary, reinforce one path, or part of it, based on observed losses, delay In Summary, reinforce one path, or part of it, based on observed losses, delay

variances, and so onvariances, and so on

– Negative reinforce certain paths because resource levels are lowNegative reinforce certain paths because resource levels are low

Directed Diffusion

Directed Diffusion

[Figure adapted from Intanagonwiwat+ 2000]

Directed Diffusion


– Data-centric disseminationData-centric dissemination

– Robust multi-path deliveryRobust multi-path delivery

– Reinforcement-based adaptation to the empirically best network pathReinforcement-based adaptation to the empirically best network path

– Energy savings with in-network data aggregation and cachingEnergy savings with in-network data aggregation and caching

– Gives designers the freedom to attach different semantics to gradient valuesGives designers the freedom to attach different semantics to gradient values

– Reinforcement can be triggered not only by sources but also by intermediate Reinforcement can be triggered not only by sources but also by intermediate

nodesnodes


– Exploration of possible naming schemesExploration of possible naming schemes


– It may consume memory since all the attribute list is being sentIt may consume memory since all the attribute list is being sent

References [Heinzelman+ 2002] W. Heinzelman, A.P. Chandrakasan and H. Balakrishnan, An Application-

Specific Protocol Architecture for Wireless Microsensor Networks, IEEE Transactions on Wireless Communications, Vol. 1, No. 4, October 2002, pp. 660-670.

[Heinzelman+ 2000] W. Heinzelman, A.P. Chandrakasan and H. Balakrishnan, Energy-Efficient Communication Protocol for Wireless Microsensor Networks, IEEE Proceedings of the Hawaii International Conference on System Sciences, January 4-7, 2000, Maui, Hawaii.

[Intanagonwiwat + 2000] C. Intanagonwiwat, R. Govindan and D. Estrin, Directed Diffusion: A Scalable and Robust Communication Paradigm for Sensor Networks, In Proceedings of the Sixth Annual International Conference on Mobile Computing and Networks (MobiCOM 2000), August 2000, Boston, Massachusetts

[Kulik+ 2002] J. Kulik, W. Heinzelman and H. Balakrishnan, Negotiation-Based Protocols for Disseminating Information in Wireless Sensor Networks, Wireless Networks 8, 2002, pp. 169-185.

Data Dissemination and Fusion In Sensor Networks

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