1. Routing Performance in the Presence of Unidirectional Links in Multihop Wireless Networks Mahesh K. Marina and Samir R. Das ACM MOBIHOC’02

2. Outline Introduction Introduction Benefit of unidirectional links for routing Benefit of unidirectional links for routing Technical of handling unidirectional links in AODV Technical of handling unidirectional links in AODV Performance evaluation Performance evaluation Conclusions Conclusions

3. Introduction(1) 3 reason cause unidirectional link 3 reason cause unidirectional link Difference in radio transceiver capabilities Difference in radio transceiver capabilities Use of transmission range control Use of transmission range control Difference in wireless channel interference experienced by different nodes Difference in wireless channel interference experienced by different nodes

4. Introduction(2) 2 conceivable advantages over using only bidirectional links 2 conceivable advantages over using only bidirectional links Improvement of the network connectivity Improvement of the network connectivity Better and shorter paths are provided Better and shorter paths are provided

5. Introduction(3) B communicates C directly B communicates C directly C requires 2 hops to communicate with B C requires 2 hops to communicate with B Without unidirectional link, the graph will separate into two parts Without unidirectional link, the graph will separate into two parts

6. Introduction(4) Many common link-layer protocols for medium access and address resolution Many common link-layer protocols for medium access and address resolution Assume bidirectional link Assume bidirectional link Depend on two-way handshakes and acknowledges Depend on two-way handshakes and acknowledges Ex: IEEE 802.11 DCF Ex: IEEE 802.11 DCF RTS-CTS-DATA-ACK RTS-CTS-DATA-ACK

7. Benefit of Unidirectional Links for Route(1) 3 models for evaluation of unidirectional links 3 models for evaluation of unidirectional links Two Power Two Power Random Power Random Power Rodoplu and Meng (R&M) Rodoplu and Meng (R&M)

8. Benefit of Unidirectional Links for Route(2)

9. Benefit of Unidirectional Links for Route(3)

10. Benefit of Unidirectional Links for Route(4)

11. Benefit of Unidirectional Links for Route(5)

12. Forgoing Observation Unidirectional links Unidirectional links Provide only incremental benefit Provide only incremental benefit Do not improve connectivity in most cases Do not improve connectivity in most cases Improve shortest path cost in general Improve shortest path cost in general Provide small benefit with per-hop acknowledge under certain densities and radio ranges Provide small benefit with per-hop acknowledge under certain densities and radio ranges

13. Technical of handling unidirectional links in AODV(1) RREQ DISCARD RREP

14. Technical of handling unidirectional links in AODV(2) 3 techniques to handle unidirectional links in AODV 3 techniques to handle unidirectional links in AODV Black Listing Black Listing Hello Hello Reverse path Search Reverse path Search

15. Technical of handling unidirectional links in AODV(3) RREQ RREP BRREP RREP BRREP RREP

16. Performance Evaluation(1)

17. Performance Evaluation(2)

18. Performance Evaluation(3)

19. Conclusions Reverse Path Search technique performs the best Reverse Path Search technique performs the best IEEE 802.11 MAC performance degrades in the presence of unidirectional links IEEE 802.11 MAC performance degrades in the presence of unidirectional links A new efficient MAC protocol to handle unidirectional links is needed A new efficient MAC protocol to handle unidirectional links is needed