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석사 1 학기 홍혁진 2009.4.27

An Opportunistic Directional MAC Protocol for Multihop Wireless Networks with Switched Beam Directional Antennas. 석사 1 학기 홍혁진 2009.4.27. Contents. Introduction Directional antennas Basic Directional MAC Protocol Opportunistic Directional MAC Protocol(OPDMAC) Conclusion. Introduction.

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석사 1 학기 홍혁진 2009.4.27

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  1. An Opportunistic Directional MAC Protocol forMultihop Wireless Networks with Switched BeamDirectional Antennas 석사1학기 홍혁진 2009.4.27

  2. Contents • Introduction • Directional antennas • Basic Directional MAC Protocol • Opportunistic Directional MAC Protocol(OPDMAC) • Conclusion

  3. Introduction • Motivation • MAC protocol aims to fully exploit the benefits of spatial reuse introduced by the use of directional antennas.

  4. Directional antennas • Directional antennas Directional antennas in multihop wireless networks offer a potential increase in the spatial reuse of the wireless channel • Pros- spatial reuse, - reduce interference, - extend the transmission range - reduce power consumptions

  5. Directional antennas Silenced Node C B A D A • Omni-directional Antennas

  6. Directional antennas Not possible using Omni C B A D A • Directional Antennas

  7. A B C D E RTS RTS CTS CTS DATA DATA ACK ACK 802.11 MAC Protocols with omi-directional This mechanism overcome hidden terminal problems but waste a large portion of the network capacity. When B communicate with C, D defer the transmission to E until B, C completed.

  8. D-MAC Example 1. DRTS-DCTS-DDTAT-DACK RTS(Request to Send) CTS(Clear to Send) DRTS A B C D E F

  9. (c) 2002 Nitin Vaidya, UIUC D-MAC Example 1. DRTS-DCTS-DDTAT-DACK RTS(Request to Send) CTS(Clear to Send) DCTS A B C D E F

  10. (c) 2002 Nitin Vaidya, UIUC D-MAC Example 1. DRTS-DCTS-DDTAT-DACK DDATA A B C D E F

  11. D-MAC Example 1. DRTS-DCTS-DDTAT-DACK DACK A B C D E F

  12. D-MAC Example 2.ORTS-OCTS-DDTAT-DACK RTS(Request to Send) CTS(Clear to Send) ORTS A B C D E F

  13. D-MAC Example 2.ORTS-OCTS-DDTAT-DACK RTS(Request to Send) CTS(Clear to Send) OCTS A B C D E F

  14. D-MAC Example 2.ORTS-OCTS-DDTAT-DACK DATA A B C D E F

  15. D-MAC Example 2.ORTS-OCTS-DDTAT-DACK ACK A B C D E F

  16. A B DATA RTS C Deafness

  17. A B DATA B CTS ACK CTS RTS Data RTS A RTS C RTS Backoff RTS Backoff C Deafness • C retransmits RTS and back off longer (it mis-deduces the congestion as the failure reason) • Underutilizes channel

  18. D-MAC Example 3. DBTMA/DA(Dual busy Tone Multiple Access Protocol using direcitional Antenna) DRTS A B C D E F

  19. D-MAC Example 3. DBTMA/DA(Dual busy Tone Multiple Access Protocol using direcitional Antenna) BTr(Receive busy tone) BTt(Transmit busy tone) DCTS A B C D E F BTr BTr

  20. D-MAC Example 3. DBTMA/DA(Dual busy Tone Multiple Access Protocol using direcitional Antenna) BTr(Receive busy tone) BTt(Transmit busy tone) DATA A B C D E F BTt BTt BTt

  21. D-MAC Example 3. DBTMA/DA(Dual busy Tone Multiple Access Protocol using direcitional Antenna) ACK A B C D E F

  22. D-MAC Example 4. RI-DMAC(Receviver-Initiated Directional Mac Protocol DRTS A B C D E F RTS1

  23. D-MAC Example 4. RI-DMAC(Receviver-Initiated Directional Mac Protocol DCTS A B C D E F RTS2

  24. D-MAC Example 4. RI-DMAC(Receviver-Initiated Directional Mac Protocol DATA A B C D E F RTS3

  25. D-MAC Example 4. RI-DMAC(Receviver-Initiated Directional Mac Protocol RTR(Ready to Receive) ACK A B C D E F RTR

  26. Basic OPDMAC Protocol • OPDMAC(Opportunistic Directional MAC Protocol ) If a node is foced to backoff due to a missing CTS, OPDMAC explores transmission opportunity in other direction • Pros- minimizesthe idle wait time of the wireless channel - increase the channel utilization. - decrease the effect of deafness without additional control overhead

  27. Operation Of OPDMAC Protocol • In case of a missing response A B RTS DATA Z

  28. Operation Of OPDMAC Protocol • In case of a missing response C RTS A B DATA Z

  29. Conclusion • OPDMAC is effective in alleviating the effect of both deafness and directional hidden terminal problems • OPDMAC also outperforms both IEEE 802.11 and Basic DMAC in terms of throughput, delay and fairness

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