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SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker:...
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Transcript of SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker:...
![Page 1: SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker: Chien-Wen.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649f445503460f94c656cf/html5/thumbnails/1.jpg)
SEEDEX: A MAC protocol for ad hoc
networks
SEEDEX: A MAC protocol for ad hoc
networksR. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001
speaker: Chien-Wen
![Page 2: SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker: Chien-Wen.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649f445503460f94c656cf/html5/thumbnails/2.jpg)
Outline• INTRODUCTION• THE IEEE 802.11 PROTOCOL• THE SEEDEX MAC PROTOCOL• SIMULATION• CONCLUSION
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INTRODUCTION• to avoid collisions without making
explicit reservation• to employ a random schedule• pseudo-random number generator• exchanging the seeds within a
two-hop neighborhood
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THE IEEE 802.11 PROTOCOL
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THE IEEE 802.11 PROTOCOL
• the wasteful scenarios– two neighborhoods are silenced– four way handshake– Backoff scheme
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SEEDEX: CHOOSING A RANDOM SCHEDULE
• preface– all nodes could publish their
schedules– two states
• L: listening• PT: possibly sending
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• choosing a slot as follows– Node T is in state PT– Node R is in state L– All of node R'sneighbors are in state L
SEEDEX: CHOOSING A RANDOM SCHEDULE
![Page 8: SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker: Chien-Wen.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649f445503460f94c656cf/html5/thumbnails/8.jpg)
• use an i.i.d. Bernoulli sequence• With probability p to be PT state• using random schedule
SEEDEX: CHOOSING A RANDOM SCHEDULE
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THE CENTRAL IDEA OF SEEDEX
• the i.i.d. Bernoulli schedule– the use of a pseudo-random number gen
erator– initial value is called the “seed”
• publishing random schedules by exchanging seeds
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THE CENTRAL IDEA OF SEEDEX
• exchanging seeds– two-hop neighborhood– fan-in and fan-out
• fan-out– broadcasts the seeds to all its neighbors
• fan-in– hearing a similar broadcast from each of its
neighbors
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SEEDEX: CHOOSING A RANDOM SCHEDULE
![Page 13: SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker: Chien-Wen.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649f445503460f94c656cf/html5/thumbnails/13.jpg)
WHEN DOES A NODE TRANSMIT A
PACKET?• Waiting for a slot
– Sender is in PT state– Receiver is in L state– if Other neighbors of Rx are in L state
then transmitElse
Min{α/n+1, 1} //n is the num. of others which are in PT state
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WHEN DOES A NODE TRANSMIT A
PACKET?• The use of α
– a Possibly Transmit state– in light traffic
• α≒2.5– in heavy traffic
• α≒1.5
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WHAT IS A GOOD CHOICE OF P?
node T is in PT state
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WHAT IS A GOOD CHOICE OF P?
node R is in L state
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WHAT IS A GOOD CHOICE OF P?
j other neighbors are in PT state, and the remaining neighbors are in L state
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WHAT IS A GOOD CHOICE OF P?
Only node T decides to trans.
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WHAT IS A GOOD CHOICE OF P?
When N=6 , p =0.246
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WHAT IS A GOOD CHOICE OF P?
Optimal p =0.21
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SIMULATION RESULT :SOME PERFORMANCE NUMBERS
• Conducted on NS• 100 nodes• chooses a random neighboring
recipient for each packet
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SIMULATION RESULT :SOME PERFORMANCE NUMBERS
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USING SEEDEX FOR RTS RESERVATIONS
• using SEEDEX only on the RTS packet
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SIMULATION RESULT :PERFORMANCE COMPARISON OF
SEEDEX-R WITH IEEE 802.11
![Page 26: SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker: Chien-Wen.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649f445503460f94c656cf/html5/thumbnails/26.jpg)
SIMULATION RESULT : PERFORMANCE COMPARISON OFSEEDEX-R WITH IEEE 802.11
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SIMULATION RESULT : PERFORMANCE COMPARISON OFSEEDEX-R WITH IEEE 802.11
![Page 28: SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker: Chien-Wen.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649f445503460f94c656cf/html5/thumbnails/28.jpg)
CONCLUSION• Avoid making reservations• Does not employ backoff scheme• Does not require silencing both
neighbors of Tx and Rx
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Futher Investigation• Fan-in procedure• The adaption of α• Impact of topology
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Disscusion
T R
PT L
L
L
LL
T R
PT L
L
L
L
PT
α /n+1
Hidden
Probability !!
![Page 31: SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker: Chien-Wen.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649f445503460f94c656cf/html5/thumbnails/31.jpg)
Disscusion
TR
PT
L
L
L
L
T R
PT L
L
L
L
Exposed
transmitt !!
![Page 32: SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker: Chien-Wen.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649f445503460f94c656cf/html5/thumbnails/32.jpg)
Disscusion
T
RPT
L
L
L
L
T R
L
L
L
Collision??
PT
PT
α /2
![Page 33: SEEDEX: A MAC protocol for ad hoc networks R. Rozovsky and P. R. Kumar ACM ACM MobiHoc 2001 speaker: Chien-Wen.](https://reader036.fdocuments.us/reader036/viewer/2022062320/56649f445503460f94c656cf/html5/thumbnails/33.jpg)
Disscusion
T
RPT
L
L
L
L
T R
PT L
L
L
Probability !!
PT
α /2