dynamic forwarding over tree-on-dag for scalable data aggregation in sensor networks

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HHigh-igh-SSpeed peed NNetworking etworking LLab.ab.HHigh-igh-SSpeed peed NNetworking etworking LLab.ab.

Dynamic Forwarding over Tree-on-DAG for SDynamic Forwarding over Tree-on-DAG for Scalable Data Aggregation in Sensor Networkscalable Data Aggregation in Sensor Networks

High-Speed Networking Lab.High-Speed Networking Lab.Dept. of CSIE, Fu-Jen Catholic UniversityDept. of CSIE, Fu-Jen Catholic University

Adviser: Jenn Wei Lin Adviser: Jenn Wei Lin Speaker: Tzung-Lin YuSpeaker: Tzung-Lin Yu

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OutlineOutline• AbstractAbstract• IntroductionIntroduction• Related WorkRelated Work

– DAA (Data Aware Anycast)DAA (Data Aware Anycast)• Dynamic Forwarding over ToDDynamic Forwarding over ToD

– One dimentionalOne dimentional– Two dimentionalTwo dimentional

• Performance EvaluationPerformance Evaluation• ConclusionConclusion• ReferenceReference

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• Computing and maintaining network structures for Computing and maintaining network structures for efficiefficient data aggregation incurs high overheadent data aggregation incurs high overhead for dynamic efor dynamic eventsvents where the set of nodes sensing an where the set of nodes sensing an event changes wevent changes with timeith time. .

• We propose We propose Tree on DAG (ToD),Tree on DAG (ToD), a a semistructuredsemistructured appr approach that uses oach that uses Dynamic ForwardingDynamic Forwarding to support to make to support to make the network the network efficient aggregationefficient aggregation in large-scale networks in large-scale networks..

I. AbstractI. Abstract

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Direct CommunicationDirect Communication

Sensor node

Base station

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LEACHLEACH100 m

叢集區

觀測區域

Base Station

Sensor (Non Cluster Head)

Sensor (Cluster Head)

Initial Data

Aggregated Data

~100m

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II. IntroductionII. Introduction• Sensor networks Sensor networks data aggregationdata aggregation can often reduce the can often reduce the

communication cost by communication cost by eliminating redundancyeliminating redundancy..

• Various Various structured approachesstructured approaches for data aggregation for data aggregation have been proposed for have been proposed for data gathering applicationsdata gathering applications and and event-based applicationsevent-based applications.. fixed structures cannot efficiently aggregate data fixed structures cannot efficiently aggregate data change the structure dynamically incur change the structure dynamically incur high high maintenance overhead maintenance overhead

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II. IntroductionII. Introduction• We propose an efficient and scalable data aggregation We propose an efficient and scalable data aggregation

mechanism that mechanism that can achieve early aggregationcan achieve early aggregation without iwithout incurring overheadncurring overhead of constructing a structure. of constructing a structure.

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III. III. Related WorkRelated Work• DAA (Data Aware Anycast)DAA (Data Aware Anycast)

– StructurelessStructureless protocol protocol– Packets have to be transmitted to the Packets have to be transmitted to the same nodesame node at t at t

he he same timesame time to be aggregated to be aggregated– Spatial convergence:Spatial convergence:

forward to the forward to the nodes that have packetsnodes that have packets (by radio) (by radio)– Temporal convergence:Temporal convergence:

using using Randomized WaitingRandomized Waiting to increase the chance to increase the chanceDisadvantage:Disadvantage:– if no neighbor has packets for aggregation if no neighbor has packets for aggregation

to to sink sink ((high costhigh cost) or return to DAA) or return to DAA– Does Does not guaranteenot guarantee the aggregation of all packetsthe aggregation of all packets

when the when the network growsnetwork grows..

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III. III. Related WorkRelated Work

• Fixed tree structures – Long stretch problem:

Packets from adjacent nodes have to be forwarded many hops away before aggregation.

EventEventSourceSource

SinkSink

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD• When no further aggregation can be achieved, we When no further aggregation can be achieved, we forwforw

ard packets on ToDard packets on ToD instead of forwarding to the sink ( instead of forwarding to the sink (DAA).DAA).

• We propose a We propose a dynamic forwarding mechanism over Todynamic forwarding mechanism over ToDD to avoid the long stretch problem of fixed structure. to avoid the long stretch problem of fixed structure.

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD• ToD in ToD in One-DimentionalOne-Dimentional Network Network

– basic of Two-Dimentionalbasic of Two-Dimentional– Network is divided into Network is divided into cellscells– cell: cell: a square (length = a square (length = ))

> Max-diameter of an > Max-diameter of an eventevent can spancan span

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F-aggregatorF-aggregator S-aggregatorS-aggregator

IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD• F&S-Tree, Cell, Cluster, and Aggregator

– Each Each F-aggregatorF-aggregator creates a shortest path creates a shortest path ((SPTSPT) to the sink.) to the sink.

–F-clustersF-clusters’ size is large ’ size is large enough to cover the enough to cover the cells an cells an eventevent can span. can span.

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD• For all sets of nearby cells that can be triggered by an For all sets of nearby cells that can be triggered by an

eventevent, either they will be , either they will be in the same F-clusterin the same F-cluster, or they , or they will be will be the same S-clusterthe same S-cluster..

to avoid the long stretch problem to avoid the long stretch problem

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToDDynamic ForwardingDynamic Forwarding1.1. using the using the DAADAA to aggregate to aggregate2.2. no further aggregation:no further aggregation:

forwarding their packets to their forwarding their packets to their F-aggregatorsF-aggregators(i) event in(i) event in single F-cluster single F-cluster using using F-tree F-tree forward the packets to theforward the packets to the sink sink ex: cell A, Bex: cell A, B(ii) event in(ii) event in multiple F-cluster multiple F-cluster select the select the S-aggregatorS-aggregator for further aggregation for further aggregation ex: cell C, D ex: cell C, D

[Property1][Property1]For For any two adjacent nodesany two adjacent nodes in ToD in 1D network, in ToD in 1D network, their packtheir packets willets will be aggregated either at an F-aggregator or S-aggregbe aggregated either at an F-aggregator or S-aggregatorator..

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD

ToD in Two-Dimentional Network• ToD in 1D works because an event always in the same

F-cluster or S-cluster.• In 2D scenarios, if an event spans multiple F-clusters, e

ach F-aggregator may have multiple choices of S-aggregators.

• Assumption:1. size of a grid cell > maximum size of an event2. event is contiguous3. Dynamic Forwarding requires each F-aggregator knows the location of S-aggregator.

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD• 5 × 5 F-clusters

F-ClusterF-Cluster

cellcellS-ClusterS-Cluster

F-ClusterF-Cluster

F-aggregatorF-aggregator

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD• an event spans cells in the an event spans cells in the

(1) same F-cluster (1) same F-cluster aggregated at the F-aggregator aggregated at the F-aggregator(2) multiple F-clusters (2) multiple F-clusters

• four basic scenariosfour basic scenarios

Generate PacketsGenerate Packets( Source)( Source)

Corresponding Corresponding S-clusterS-cluster

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD(2) multiple F-clusters

packets originate from (i) 3 or 4 cells in the same F-cluster no other nodes in other F-clusters have packets forward to the sink

F -clusterF -cluster F -clusterF -cluster

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(ii) 1 or 2 cells possible that other F-clusters also have packet (a) 1 cell: in the same S-cluster F-aggregator forward packets to S-aggregator

(b) 2 cells: must be in different S-cluster 3 cases :

F -clusterF -cluster

F -clusterF -cluster

S -clusterS -cluster

F -clusterF -cluster F -clusterF -cluster

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD• Case 2: X-Cluster 2 cell, Y-Cluster 1 cell

– to guarantee that the packets can meet at least at one S-aggregator two F-aggregators select one S-aggregator (closer to the sink) be the 2nd S-aggregators

– S-aggregator only forwards packets to the 2nd S-aggregators if the packets it received come from two cells in one F-cluster

– 2nd S-aggregator wait longer than the 1st S-aggregator

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD

[Property2][Property2]any two adjacent nodesany two adjacent nodes in ToD, their packet will be ag in ToD, their packet will be aggregated at the gregated at the F-aggregatorF-aggregator, at the 1, at the 1stst

S-aggregatorS-aggregator, or , or at the 2at the 2nd nd S-aggregatorS-aggregator

• even if the even if the size of event is not knownsize of event is not known, this approach ca, this approach can work and n work and efficiently than DAAefficiently than DAA

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToD• F&S-clusters select an aggregator

– nodes play this role in turn distribute the energy consumption

– nodes can elect themselves – Frequency of updating can be low.– Using a hash function to hash current time to a node.

select the kth node be the aggregator

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IV. Dynamic Forwarding over ToDIV. Dynamic Forwarding over ToDchoose a Aggregating Clusterchoose a Aggregating Cluster• to to SimplifySimplify the cluster-head selection process the cluster-head selection process • Choose an Choose an F-clusterF-cluster, called , called Aggregating ClusterAggregating Cluster, for each , for each S-S-

clustercluster. (closet to the sink). (closet to the sink)• Use the Use the F-aggregatorF-aggregator of of Aggregating ClusterAggregating Cluster as the S-cluster’s as the S-cluster’s

S-aggregatorS-aggregator..• The common aggregator for both the shaded F-cluster and S-The common aggregator for both the shaded F-cluster and S-

clustercluster

FFSS Aggregating ClusterAggregating Cluster aggregator aggregator

(Use the (Use the F-aggregatorF-aggregator as the as the S-S-aggregatoraggregator))

Select the Select the Aggregating ClusterAggregating Cluster aggregator instead of aggregator instead of S-ClusterS-Cluster

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V. V. Performance EvaluationPerformance Evaluation• Kansei sensor testbed

– Nodes: 105 Mica2-based motes – 7×15 grid network with 3-ft spacing– Each mote is hooked onto a Stargate– Stargate:

» a 32-bit hardware device from CrossBow running Linux» be connected to the server using wired Ethernet» program motes, send messages and signals to motes through Stargate

– Radio signal: using default transmission power covers most nodes – Limit nodes only to receive packets from two-grid neighboring nodes

neighbors : Each node has a maximum of 12 neighbors– Event size: not limit– Generated an Event report: Node is triggered by an event (store in a repo

rt queue)– Both the application layer and Anycast MAC layer can access the report

queue– Divide the network into 2 F-clusters in ToD– The smallest cell to have only 9 sensor nodes

• do not consider energy of consumption on idle listening

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V. V. Performance EvaluationPerformance Evaluation• Protocol

– Dynamic Forwarding over (ToD)– DAA: structureless approach – SPT: node send packets to the sink through the SPT immedia

tely after sensing an event– SPT-D (SPT with Fixed Delay ): SPT with delay according t

o their height

• Normalized number of transmissions (NNT)Normalized number of transmissions (NNT) = = Number of transmissionsNumber of transmissions in the entire network in the entire network ÷÷ useful information useful information from sources to the sink from sources to the sink

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V. V. Performance EvaluationPerformance Evaluation• NNT vs. Event SizeNNT vs. Event Size

– fixed event locationfixed event location– Diameter: 12 ~ 36 ftDiameter: 12 ~ 36 ft– Node Node 2~6 grid-hops of the event2~6 grid-hops of the event will be triggered will be triggered– Sink : at one corner Sink : at one corner

Performance:Performance:• Size Size , ToD , ToD (more chances(more chances

to aggregated)to aggregated)• Size Size ,SPT-D ,SPT-D

(long stretch problem)(long stretch problem)• fixed structured fixed structured affects affects

performance significantlperformance significantlyy

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V. V. Performance EvaluationPerformance Evaluation• NNT vs. Maximum DelayNNT vs. Maximum Delay

– Delay: 0 ~ 8 sec. Delay: 0 ~ 8 sec. – All node generate one packet every 10 sec. All node generate one packet every 10 sec.

Performance:Performance:• SPT-DSPT-D (structured-based) (structured-based)

heavily heavily depends on the delaydepends on the delay

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V. V. Performance EvaluationPerformance Evaluation• Large-Scale SimulationLarge-Scale Simulation

– NS2 simulatorNS2 simulator– ToD, DAA, SPT andToD, DAA, SPT and OPT OPT– 2000 × 12002000 × 1200 m grid network with m grid network with 35-m node separation35-m node separation– 1938 nodes1938 nodes– Transmission Transmission rangerange of nodes: of nodes: >50m >50m– Event movesEvent moves: : random waypoint mobility model at speed of 10 m/s for 40random waypoint mobility model at speed of 10 m/s for 40

0 seconds.0 seconds.Event Size: 400m in diameterEvent Size: 400m in diameter

– OPT (Optimal Aggregation Tree):OPT (Optimal Aggregation Tree):» nodes forward their packets on thenodes forward their packets on the aggregation tree aggregation tree» aggregation tree:aggregation tree: rooted atrooted at center of the event center of the event» Nodes Nodes know where to forwardknow where to forward packet to and packet to and how long to waithow long to wait» change when event moveschange when event moves» not considerate the construction overheadnot considerate the construction overhead

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Total Unit of Useful Info. Received by Sink vs. Event Size

OPT:OPT:best performance,best performance,but but overhead notoverhead notconsideredconsidered

V. V. Performance EvaluationPerformance EvaluationNTT vs. Event SizeNNT vs. Event Size

closer to the sourcecloser to the source

Aggregate packets earlyAggregate packets early

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V. V. Performance EvaluationPerformance EvaluationNNT vs. Distance to the SinkNNT vs. Distance to the Sink NTT vs. Distance to the SinkNTT vs. Distance to the Sink

Number of Packet Received at the sink per event Number of Packet Received at the sink per event vs. Distance to the Sinkvs. Distance to the Sink

The lower the betterThe lower the better(ratio of aggregation is high)(ratio of aggregation is high)

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VI. ConclusionVI. Conclusion• We proposed a semistructured approach.• Dynamic Forwarding on ToD to avoid the long stretch

problem in fixed structured and eliminates the overhead of constructing and maintaining dynamic structures.

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VII. Reference

• Dynamic Forwarding over Tree-on-DAG for Scalable Dynamic Forwarding over Tree-on-DAG for Scalable Data Aggregation in Sensor NetworksData Aggregation in Sensor NetworksFan, Kai-Wei; Liu, Sha; Sinha, Prasun;Fan, Kai-Wei; Liu, Sha; Sinha, Prasun;Mobile Computing, IEEE Transactions onVolume 7, Volume 7, Issue 10, Oct. 2008 Page(s):1271 - 1284 , Oct. 2008 Page(s):1271 - 1284 Digital Object Identifier 10.1109/TMC.2008.55 Digital Object Identifier 10.1109/TMC.2008.55

dynamic forwarding over tree-on-dag for scalable data aggregation in sensor networks

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