using soft-line recursive response to improve query aggregation in wireless sensor networks

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

Using Soft-line Recursive Response to ImUsing Soft-line Recursive Response to Improve Query Aggregation in Wireless Senprove Query Aggregation in Wireless Sen

sor Networkssor Networks

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

Adviser: Jonathan C. Lu, Ph.D.Adviser: Jonathan C. Lu, Ph.D.Speaker: Tzung-Lin YuSpeaker: Tzung-Lin Yu

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OutlineOutline• AbstractAbstract• IntroductionIntroduction• Related WorkRelated Work• SRR protocolSRR protocol• EvaluationEvaluation• ConclusionConclusion• ReferenceReference

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I. AbstractI. Abstract

BSBS

Query forQuery fork-typek-type data data

ResponseResponse

• BS BS queryquery for for k-typek-type data data• sensors sensors responseresponse the k-type packets the k-type packets

waiting with waiting with a delay timea delay time

waiting with waiting with a delay timea delay time

kk

kk

kk

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• In WSNs, In WSNs, aggregatedaggregated or or compressed datacompressed data along the way t along the way toward the BS is desirable for oward the BS is desirable for saving energysaving energy . .

• Each hop might incur Each hop might incur varying delaysvarying delays due to medium acce due to medium access contention, transmission and computation delays.ss contention, transmission and computation delays.

• The common method to aggregate data uses a The common method to aggregate data uses a hard-line phard-line precomputed timerrecomputed timer..

• We develop a novel method, We develop a novel method, Soft-line Recursive ResponSoft-line Recursive Response (SRR)se (SRR), that bases response-wait on, that bases response-wait on actual response ti actual response timesmes to previous queries using a to previous queries using a history buffer history buffer..

I. AbstractI. Abstract

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21 transmissions21 transmissions1010 88

33

10 transmissions10 transmissions

I. AbstractI. AbstractAn An exampleexample to motivate to motivate SRRSRR • Once Once aggregation missesaggregation misses, downstream data will , downstream data will not be able to not be able to

catch upcatch up with the upstream traffic. with the upstream traffic.

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II. Introduction• Sensors in some areas might have Sensors in some areas might have different transmission abilitiesdifferent transmission abilities

from sensors in from sensors in other areasother areas therefore introducing therefore introducing different different transmission delaytransmission delay..

• Under the presence of network failure or delay fluctuations, we Under the presence of network failure or delay fluctuations, we want to want to maximize the amount of trafficmaximize the amount of traffic going back to the sink in going back to the sink in the the least amount of timeleast amount of time..

• Our goal is to Our goal is to have query responses flowhave query responses flow from the network edge from the network edge towards the BS while towards the BS while maximizing aggregation maximizing aggregation using shortest using shortest paths.paths.

– the event of the event of failure or temporal delayfailure or temporal delay, the aggregation process should , the aggregation process should skip skip those nodes those nodes for more aggregationfor more aggregation

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III. Related Work - III. Related Work - iBubble InfrastructureiBubble Infrastructure

• SRRSRR adapt to the adapt to the iBubbleiBubble infrastructure with infrastructure with minimal minimal modification.modification.

• iBubbleiBubble routing protocol allows efficient query in routing protocol allows efficient query in heterheterogeneousogeneous networks networks

– KeywordsKeywords for describing sensor for describing sensor data typedata type and sending the and sending the keywords towards the BS to keywords towards the BS to guide and restrict queriesguide and restrict queries..

– original: not consider aggregationoriginal: not consider aggregation

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III. Related Work - III. Related Work - iBubble InfrastructureiBubble InfrastructureiBubble in Heterogeneous WSNiBubble in Heterogeneous WSN

• since since N7N7 has received keyword has received keyword kk from downstream from downstream when BS queries for when BS queries for kk, N7 will , N7 will forward the queryforward the query to its to its children (N3, N6) announced children (N3, N6) announced kk waitswaits for both nodes to replyfor both nodes to reply

• N3, N4: N3, N4: forwardforward the query the query• N5, N6: N5, N6: sendsend data upstreamdata upstream immediately immediately

hopcounthopcount

can sense type kcan sense type k

{type of sensing device} {keywords}{type of sensing device} {keywords}

88

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A. When Network A. When Network Connection Is PerfectConnection Is Perfect (using Basic Recursive Response) (using Basic Recursive Response)

1.1. Homogenous NetworkHomogenous Network1) edge nodes 1) edge nodes respond to a query respond to a query immediatelyimmediately 2) others 2) others waitwait forfor responsesresponses from from allall of its downstream of its downstream

2.2. Heterogeneous NetworkHeterogeneous Network• using iBubble Infrastructureusing iBubble Infrastructure

IV. SRR protocolIV. SRR protocol

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IV. SRR protocolIV. SRR protocolB. When the Network is B. When the Network is Not Perfect)Not Perfect) (Using the (Using the Soft-lineSoft-line ThresholdThreshold to Override Recursion) to Override Recursion)

• When a node When a node receives a query requestreceives a query request, it will , it will calculate how long it calculate how long it should wait should wait for the downstream response using the for the downstream response using the α– percentileα– percentile of of the previous downstream response delay values it tracks in its the previous downstream response delay values it tracks in its two two history buffershistory buffers..

– 11stst buffer buffer : : » store all store all history response-timeshistory response-times» record record even time-out last timeeven time-out last time» for calculating the nextfor calculating the next» if buffer is full: if buffer is full: FIFO queueFIFO queue

– 22ndnd buffer buffer ::» same values as 1same values as 1stst but a but a sorted listsorted list» binary search to insert a new response timebinary search to insert a new response time

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IV. SRR protocolIV. SRR protocolEx: node Ex: node xx, sorted list (1, 2, 3, 4), sorted list (1, 2, 3, 4)

the next the next response comesresponse comes in in xx computes the response-time = 2.5 (response - query) computes the response-time = 2.5 (response - query) list = (1, 2, 2.5, 3, 4) list = (1, 2, 2.5, 3, 4)a a new query comesnew query comes in (with in (with α– percentile = 80%α– percentile = 80%)) 5 (elements) × 80% = 4, 5 (elements) × 80% = 4, index = 4, index = 4,it will it will wait forwait for downstream query responses for downstream query responses for 3 seconds3 seconds

• insertion and deletion intoinsertion and deletion into FIFO FIFO (1(1stst buffer): buffer): constant timeconstant time • insertion and deletion into insertion and deletion into sorted listsorted list (2 (2stst buffer): buffer): logarithmic timelogarithmic time• computation of computation of α–percentile: constant timeα–percentile: constant time SRR SRR operation times at mostoperation times at most O (log b) computation time O (log b) computation time

(b= history buffer size) (b= history buffer size)

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V. EvaluationV. Evaluation

• 500 nodes randomly in a WSN • 1000 × 1000m2 area• BS centered at the middle of the area.• Node’s radio transmission range: 240m

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V. EvaluationV. Evaluation

• Larger buffer Larger buffer reduce morereduce more aggregation aggregation missesmisses

• fixing buffer size:fixing buffer size:αα↑, ↑, aggregation miss↓aggregation miss↓

α=10%α=10%

α=100%α=100%

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V. EvaluationV. EvaluationSRR’s two advantage over hard-line• when α increases when α increases

SRR: SRR: aggregation aggregation miss tolerance increasesmiss tolerance increases & & end to end end to end delay decreasingdelay decreasing

RSSRSS

response delays of three distributions (buffers)response delays of three distributions (buffers)

– Average end to end node Average end to end node response delay to BSresponse delay to BS

– Average response delays Average response delays from nodes situated at from nodes situated at network edge to BSnetwork edge to BS

– Contrast aggregation miss Contrast aggregation miss between the hard-line and between the hard-line and SRRSRR

Miss SavingMiss Saving

DelayDelay SavingSavingSoft / Hard Soft / Hard SavingSaving

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VI. ConclusionVI. Conclusion

• Our simulations show that SRR can improve aggregatiOur simulations show that SRR can improve aggregation on opportunities up to 120%opportunities up to 120% over the hard-line approac over the hard-line approach, while h, while increasing response delay less than 5%increasing response delay less than 5%..

• SRR SRR reduces query response trafficreduces query response traffic and data redundanc and data redundancy in both y in both homogeneoushomogeneous and and heterogeneousheterogeneous staticstatic and and mmobileobile WSNs with a maximum WSNs with a maximum O(N)O(N) transmission overhtransmission overheadead in large WSNs of N nodes and in large WSNs of N nodes and O (log b) update cosO (log b) update costt. (b= history buffer size). (b= history buffer size)

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VII. Reference

• Using Soft-Line Recursive Response to Improve Query Aggregation in Wireless Sensor NetworksXiaoming Lu; Spear, M.; Levitt, K.; Matloff, N.S.; Wu, S.F.;Communications, 2008. ICC '08. IEEE International Conference on

19-23 May 2008 Page(s):2309 - 2316 Digital Object Identifier 10.1109/ICC.2008.440

using soft-line recursive response to improve query aggregation in wireless sensor networks

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