A Probabilistic and opportunistic flooding algorithm

in wireless sensor networks

Seung-gyu, BYEONhrfeel@mobile.re.kr

Mobile Networking & Computing Lab.Dept. of Electrical & Computer Eng.

Pusan National University

IntroductionThe Purpose of FloodingGeneral formsTypical Issues of FloodingAnother Issue in WSNs

POFAMotivationKey IdeaRA-MPRRA-MPR SelectionRetransmission Policy

Numerical ResultFlooding EfficiencyAchieving the target Reliability

Conclusions

Contents

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Introduction

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The primaryPropagates a message throughout a networks for certain purposeTo make sure that all the nodes in a network receive the sameNOT Routing

The Purpose of Flooding

SourceRelayDestina-tion

The applicationRoutingBridging

Introduction

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Blind floodingAll the nodes rebroadcast / relays / forwards the received message

General forms

An general form, also called as Simple FloodingMore transmission occurred, as the node density increases

SourceRelayDestina-tion

Advanced Flooding schemesProbability-basedArea-basedNeighbor Knowledge Method-based / Topology-based / Tree-based

Introduction

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Typical issues of Flooding

Efficiency or Reliability

SourceRelayDestina-tion

Tradeoff RelationIf # of the predetermined relay nodes is reduced, they could fail to receive a broadcast packet If # of the predetermined relay nodes is increased, they could incur Broadcast Storm

Introduction

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Another Issue of WSNs

Nasty Wireless LinksHard to achieve high reliabilityRetransmissions are needed / exploited

SourceRelay

New QuestionHow many timesWhich node

POFA

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Multipoint Relay (MPR) SelectionAlgorithm used to solve MCDS problem, in OSLRKnown as optimum solution

Motivation

Me1-hop Nbr2-hop NbrMPR

Every link presumed to be error-freeNot guarantee Reliability

POFA

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Limitations of MPR SelectionDo not Aware Link error ratesCan not assure Reliability

Key Idea

Proposed schemeto assure Reliability r

More 1-hop neighbors like MPRMore transmission (Retransmission / Rebroadcast)

POFA

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Expected Delivery Probability (EDP) : Error Rate of the Link i to jas 1 times

RA-MPR

m

s

1−𝑙𝑠𝑚 𝑖𝑓 𝑚∈𝑁1

m

Me1-hop Nbr2-hop Nbr

1−∏𝑘∈𝑁1

[1− (1− 𝑙𝑠 𝑘) (1− 𝑙𝑘𝑚 ) ]𝑖𝑓 𝑚∈𝑁 2𝐸𝐷 𝑃𝑚= {¿

𝐸𝐷 𝑃𝑚𝑛={ 1−𝑙𝑠𝑚

𝑛 𝑖𝑓 𝑚∈𝑁1  

1−∏𝑘∈𝑁1

[1− (1− 𝑙𝑠𝑘𝑛 ) (1− 𝑙𝑘𝑚 ) ] 𝑖𝑓 𝑚∈𝑁2  

as n times

𝐸𝐷 𝑃𝑚𝑛 ={ 1−𝑙𝑠𝑚

𝑛 𝑖𝑓 𝑚∈𝑁1  

1− ∏𝑘∈𝑁𝑅

[1− (1− 𝑙𝑠𝑘𝑛 ) (1− 𝑙𝑘𝑚 ) ] 𝑖𝑓 𝑚∈𝑁2  

POFA

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Reliability-aware multipoint relay (RA-MPR) SelectionTo achieve a given Reliabilitynot to cover all 2-hop neighbors

RA-MPR Selection

𝐸𝐷 𝑃𝑛

RA-MPR Selection AlgorithmMe iteratively selects an RA-MPR among non-RA-MPR neighbors so as to increase the EDP mostUntil the EDP satisfies the target reliability R

Me1-hop Nbr2-hop Nbr

0.2

0.12

0.02

0.1

0.14

0.1

0.071) R = 0.4

2) R = 0.95

¿∑

𝑚∈𝑁1𝑜𝑟 𝑁2

𝐸𝐷𝑃𝑚𝑛

|𝑁1|+|𝑁2|

POFA

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The result of the real worldeither a success or a failure in contrast to the probabilistic calculation like 0.3141592…The number of the received packet MUST be a Natural Number

Retransmission Policy

ms

Opportunistic RetransmissionOverhearing / BACK(Broadcast ACK) handling

msStop!

Online EDP : Recalculated EDP with Real Result

Implicit ACK explicit ACK

Success :

Failure : −𝑃 (𝑀|𝐴 ),𝑃 (𝑀∩ 𝐴)𝑃 ( 𝐴 )

=¿¿∑𝑘=1

𝑛

(𝑛𝑘) (1− 𝑙 )𝑘 𝑙𝑛

¿∑𝑘=0

𝑛

(𝑛𝑘) (1−𝑙 )𝑘𝑙𝑛¿1− 𝑙𝑛

𝑃 ( 𝐴 )

Numerical Results

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Simulation Environment

Link Error RateCan be controlled (?)

Numerical Results

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NTPThe total # of broadcasts divided by the # of nodes

Flooding Efficiency

As the link error rate increasesNot only a node, but also its 1-hop and 2-hop neighbors, probably, retransmit the packet more timesBut can achieve high reliability (?)

Numerical Results

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ATRThe achieved Reliability divided by the target reliability

Achieving the target Reliability

As the link error rate increasesif including all one-hop neighbors as RA-MPRs cannot make the EDP greater than the target relia-bilityA sender increments the # of transmissions

Optimum Efficiency

Conclusions

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Predetermining TechniqueThe Predetermined RA-MPRs only can forwards the received packets the Predetermined time(s)But retransmits opportunistically (but little)

The opportunistic transmissionIn ExOR, MORE and SOAR, any node amongst Forwarder Candidate can forward it

This is not opportunistic flooding

Future workContribution Level based Opportunistic Flooding for Wireless Multihop Networks, 2015. 6

– 1 time revisedOpportunistic Flooding in Low-Duty-Cycle Wireless Sensor Networks with Unreliable Links, 2014.11

- 16 times re-vised

Mobile Networking and Computing Lab.

I appreciate your deep interest