Routing Performance in the PrRouting Performance in the Presence of Unidirectional Links esence of Unidirectional Links in Multihop Wireless Networksin Multihop Wireless Networks

Mahesh K. Marina and Samir R. DasMahesh K. Marina and Samir R. Das

ACM MOBIHOC’02ACM MOBIHOC’02

OutlineOutline

IntroductionIntroductionBenefit of unidirectional links for routingBenefit of unidirectional links for routingTechnical of handling unidirectional links in Technical of handling unidirectional links in

AODVAODVPerformance evaluationPerformance evaluationConclusionsConclusions

Introduction(1)Introduction(1)

3 reason cause unidirectional link3 reason cause unidirectional linkDifference in radio transceiver capabilitiesDifference in radio transceiver capabilitiesUse of transmission range controlUse of transmission range controlDifference in wireless channel interference Difference in wireless channel interference

experienced by different nodesexperienced by different nodes

Introduction(2)Introduction(2)

2 conceivable advantages over using only 2 conceivable advantages over using only bidirectional linksbidirectional links Improvement of the network connectivityImprovement of the network connectivityBetter and shorter paths are providedBetter and shorter paths are provided

Introduction(3)Introduction(3)

B communicates C directlyB communicates C directlyC requires 2 hops to communicate with BC requires 2 hops to communicate with B

Without unidirectioWithout unidirectional link, the graph nal link, the graph will separate into twill separate into two partswo parts

Introduction(4)Introduction(4)

Many common link-layer protocols for Many common link-layer protocols for medium access and address resolutionmedium access and address resolutionAssume bidirectional linkAssume bidirectional linkDepend on two-way handshakes and Depend on two-way handshakes and

acknowledgesacknowledgesEx: IEEE 802.11 DCFEx: IEEE 802.11 DCF

RTS-CTS-DATA-ACKRTS-CTS-DATA-ACK

Benefit of Unidirectional Links for Benefit of Unidirectional Links for Route(1)Route(1)

3 models for evaluation of unidirectional lin3 models for evaluation of unidirectional linksksTwo PowerTwo PowerRandom PowerRandom PowerRodoplu and Meng (R&M)Rodoplu and Meng (R&M)

Benefit of Unidirectional Links for RBenefit of Unidirectional Links for Route(2)oute(2)

Benefit of Unidirectional Links for RBenefit of Unidirectional Links for Route(3)oute(3)

Benefit of Unidirectional Links for RBenefit of Unidirectional Links for Route(4)oute(4)

Benefit of Unidirectional Links for RBenefit of Unidirectional Links for Route(5)oute(5)

Forgoing ObservationForgoing Observation

Unidirectional linksUnidirectional linksProvide only incremental benefitProvide only incremental benefitDo not improve connectivity in most casesDo not improve connectivity in most cases Improve shortest path cost in generalImprove shortest path cost in generalProvide small benefit with per-hop Provide small benefit with per-hop

acknowledge under certain densities and acknowledge under certain densities and radio rangesradio ranges

Technical of handling unidirectional Technical of handling unidirectional links in AODV(1)links in AODV(1)

RREQ

RREQ RREQ

RREQ

RREQ DISCARD

RREPRREP

Technical of handling unidirectional Technical of handling unidirectional links in AODV(2)links in AODV(2)

3 techniques to handle unidirectional links 3 techniques to handle unidirectional links in AODVin AODVBlack ListingBlack ListingHelloHelloReverse path SearchReverse path Search

Technical of handling unidirectional Technical of handling unidirectional links in AODV(3)links in AODV(3)

RREQ

RREQ

RREQ

RREQ

RREQ

RREQ

RREQ

RREQ

RREQ

RREQRREPRREP

RREP

RREP

BRREP

RREP

BRREP

RREP

Performance Evaluation(1)Performance Evaluation(1)

Performance Evaluation(2)Performance Evaluation(2)

Performance Evaluation(3)Performance Evaluation(3)

ConclusionsConclusions

Reverse Path Search technique performs Reverse Path Search technique performs the bestthe best

IEEE 802.11 MAC performance degrades IEEE 802.11 MAC performance degrades in the presence of unidirectional linksin the presence of unidirectional links

A new efficient MAC protocol to handle A new efficient MAC protocol to handle unidirectional links is neededunidirectional links is needed