1. Topology Considerations on Contention-based Directional MAC Simulation
July 2009
Topology Considerations on Contention-based Directional MAC Simulation
Date:
Authors:
W. Y. Lee et. al

2. July 2009
Impact of Topology on Simulation of Contention-based Directional MAC (1/2)
Topology and Service Scenario of Directional MAC observes different behaviors in simulation.
For example, CRTS and CRCM have been tested under different topology.
G Jakllari, J Broustis, T Korakis,S V. Krishnamurthy, and L Tassiulas, "Handling Asymmetry in Gain in Directional Antenna Equipped Ad Hoc Networks," Proc. IEEE 16th International Symposium on PIMRC, pp , 2005
M Takata, M Bandai and T Watanabe, "MAC Protocol with Directional Antennas for Deafness Avoidance in Ad Hoc Networks," Proc. IEEE Goblecom 2007, pp , 2007
CRCM
CRTS
Randomly distributed 100 Nodes in 1500x1500m 1 2 3 4
<4 nodes in linear topology>
<Randomly distributed topology>
Slide 2
W. Y. Lee et. al 2

3. July 2009
Impact of Topology on Simulation of Contention-based Directional MAC (1/2)
We observe the throughput performance of the two is reversed with different topology
=> Hence, a standardized approach is necessary.
CRCM
CRTS
<4 node in linear topology>
<Randomly distributed topology>
Slide 3
W. Y. Lee et. al 3

4. Three Performance Indices need to be analyzed
July 2009
Three Performance Indices need to be analyzed
Deafness problem (e.g., deafness ratio)
Hidden node problem (e.g., failure rate due to hidden nodes)
Spatial reuse
W. Y. Lee et. al

5. Deafness Problem
Definition: deafness occurs if a device does not answer an RTS message addressed to it.
Consequences: originator of the RTS will try more RTSs while increasing contention window, during which messages toward other devices are subject to be blocked.
Two examples

6. Deafness Example #1 Assume 3 nodes. July 2009 1 2 A 4 3 1 2 1 2 X B 4
Slide 6
W. Y. Lee et. al 6

7. Deafness Example #1 Node A has a data to send B. A sends DRTS.
July 2009
Deafness Example #1
Node A has a data to send B.
A sends DRTS. A 1 2 4 3
DRTS X 1 2 4 3 B 1 2 4 3
W. Y. Lee et. al

8. Deafness Example #1 Node B responds with DCTS. July 2009 1 2 A DCTS 43
DCTS X 1 2 4 3 B 1 2 4 3
Slide 8
W. Y. Lee et. al 8

9. July 2009
Deafness Example #1
Other beams except one in communication are blocked. A 1 2 4 3
In Communication X 1 2 4 3 B 1 2 4 3
Slide 9
W. Y. Lee et. al 9

10. July 2009
Deafness Example #1
Now, node X has a data to send A, it will send DRTS to A. (node A is deaf now.) A 1 2 4 3
Deafness
DRTS X 1 2 4 3 B 1 2 4 3
Slide 10
W. Y. Lee et. al 10

11. Deafness Example #2 Four nodes. Now, node S has a data to send D.
July 2009
Deafness Example #2
Four nodes.
Now, node S has a data to send D. A 1 2 4 3 D 1 2 4 3 B 1 2 4 3 S 1 2 4 3
W. Y. Lee et. al

12. Deafness Example #2 Four nodes. Now, node S has a data to send D.
July 2009
Deafness Example #2
Four nodes.
Now, node S has a data to send D. A 1 2 4 3 D 1 2 4 3 B 1 2 4 3 S 1 2 4 3
DRTS
Slide 12
W. Y. Lee et. al 12

13. Deafness Example #2 Nodes A and B overhear the DRTS from S.
July 2009
Deafness Example #2
Nodes A and B overhear the DRTS from S.
Nodes A and B block their beams 3 and 4, respectively. A 1 2 4 3 D 1 2 4 3 B 1 2 4 3 S 1 2 4 3
DRTS
Slide 13
W. Y. Lee et. al 13

14. Deafness Example #2 Node D responds with DCTS.
July 2009
Deafness Example #2
Node D responds with DCTS.
Node B overhears the DCTS and blocks beam 2. A 1 2 4 3 D 1 2 4 3 B 1 2 4 3 S 1 2 4 3
DCTS
Slide 14
W. Y. Lee et. al 14

15. Deafness Example #2 Nodes S and D are in communication. July 2009 A 14 3 D 1 2 4 3 B 1 2 4 3 S 1 2 4 3
In Communication
Slide 15
W. Y. Lee et. al 15

16. Deafness Example #2 Now, B has a data to A, so it sends DRTS to A.
July 2009
Deafness Example #2
Now, B has a data to A, so it sends DRTS to A.
But, node A’s beam 3 is blocked (Another deafness problem).
Deafness A 1 2 4 3 D 1 2 4 3
DRTS B 1 2 4 3 S 1 2 4 3
DCTS
Slide 16
W. Y. Lee et. al 16

17. July 2009
Hidden Terminal
W. Y. Lee et. al

18. Hidden Terminal Problem
Definition: hidden terminal problem occurs if another device interfere on-going communication by causing collision.
Consequences: throughput of on-going communication is degraded.
Two examples

19. Hidden Terminal Example #1
Assume nodes sense carrier omni-directionally.
Sensing Range D C B A
Slide 19
W. Y. Lee et. al

20. Hidden Terminal Example #1
Now, node B has a data to A D C B A
Slide 20
W. Y. Lee et. al

21. Hidden Terminal Example #1
Node B has a data to A
DRTS D C B A
Slide 21
W. Y. Lee et. al

22. Hidden Terminal Example #1
Node B changes it receiving antenna mode to directional one. D C B A
Slide 22
W. Y. Lee et. al

23. Hidden Terminal Example #1
Node A sends back to B with DCTS.
DCTS D C B A
Slide 23
W. Y. Lee et. al

24. Hidden Terminal Example #1
Node A turns its receiving antenna mode to directional one, and communication is going on.
In Communication D C B A
Slide 24
W. Y. Lee et. al

25. Hidden Terminal Example #1
Now, node D has a data to send C.
But, D’s RTS accidentally reaches to node A’s receiving range due to some channel conditions.
In Communication D C B A
Collision
Slide 25
W. Y. Lee et. al

26. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
4 nodes
Node A has a data to B. S 1 2 4 3 D 1 2 4 3 A 1 2 4 3 B 1 2 4 3
Slide 26
W. Y. Lee et. al 26

27. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Node A sends DRTS to B. S 1 2 4 3 D 1 2 4 3 A 1 2 4 3
DRTS B 1 2 4 3
W. Y. Lee et. al

28. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Node B responds with DCTS. S 1 2 4 3 D 1 2 4 3 A 1 2 4 3
DCTS B 1 2 4 3
Slide 28
W. Y. Lee et. al 28

29. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Nodes A and B are in communication. S 1 2 4 3 D 1 2 4 3 A 1 2 4 3
In Communication B 1 2 4 3
Slide 29
W. Y. Lee et. al 29

30. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Now, node S has a data to send D, so it sends DRTS to D. S 1 2 4 3 D 1 2 4 3
DRTS A 1 2 4 3
In Communication B 1 2 4 3
Slide 30
W. Y. Lee et. al 30

31. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Node D responds with DCTS. S 1 2 4 3 D 1 2 4 3
DCTS A 1 2 4 3
In Communication B 1 2 4 3
Slide 31
W. Y. Lee et. al 31

32. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Nodes S and D are in communication. S 1 2 4 3 D 1 2 4 3
In Communication A 1 2 4 3
In Communication B 1 2 4 3
Slide 32
W. Y. Lee et. al 32

33. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Further, nodes A and B complete their communication. S 1 2 4 3 D 1 2 4 3
In Communication A 1 2 4 3
Communication completed B 1 2 4 3
Slide 33
W. Y. Lee et. al 33

34. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Again, node A has a data to D. S 1 2 4 3 D 1 2 4 3
In Communication A 1 2 4 3
Now, A has a data to D B 1 2 4 3
Slide 34
W. Y. Lee et. al 34

35. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Node A sends DRTS to D since A did not hear previous DRTS from S nor DCTS from D. S 1 2 4 3 D 1 2 4 3
In Communication A 1 2 4 3
DRTS B 1 2 4 3
Slide 35
W. Y. Lee et. al 35

36. Hidden Terminal Example #2
July 2009
Hidden Terminal Example #2
Collision due to unheard RTS/CTS.
Collision S 1 2 4 3 D 1 2 4 3
In Communication A 1 2 4 3
DRTS B 1 2 4 3
Slide 36
W. Y. Lee et. al 36

37. Spatial Reuse Benefit from directivity of directional antennas.
Two examples

38. Spatial Reuse July 2009 D 1 2 4 3 E 1 2 4 3 F 1 2 4 3 A 1 2 4 3 B 1 2C 1 2 4 3
W. Y. Lee et. al

39. Spatial Reuse July 2009 1 2 D 4 3 1 2 A 4 3 1 2 B 4 3 1 2 S 4 3
W. Y. Lee et. al

40. An Example of Topology in Simulation
July 2009
An Example of Topology in Simulation
W. Y. Lee et. al

41. Scenarios (Conference Room)
July 2009
Scenarios (Conference Room)
Deafness Example#1
W. Y. Lee et. al

42. Scenarios (Conference Room)
July 2009
Scenarios (Conference Room)
Antenna blocked
Deafness Example #2
W. Y. Lee et. al

43. Scenarios (Conference Room)
July 2009
Scenarios (Conference Room)
Hidden Terminal Problem Example#1
W. Y. Lee et. al

44. Scenarios (Conference Room)
July 2009
Scenarios (Conference Room)
Communication
Completed
Hidden terminal example #2
W. Y. Lee et. al

45. Scenarios (Conference Room)
July 2009
Scenarios (Conference Room)
Spatial reuse
W. Y. Lee et. al

46. Scenarios (Conference Room)
July 2009
Scenarios (Conference Room)
W. Y. Lee et. al

47. July 2009
References
[1] R. R. Choudhury, X. Yang, R. Ramanathan and NH Vaidya, “On designing MAC protocols for wireless networks using directional antennas,” IEEE Trans. Mobile Computing, Volume 5, Issue 5, May 2006, pp.477 – 491
[2] R.R. Choudhury, X. Yang, N.H. Vaidya, and R. Ramanathan, “Using Directional Antennas for Medium Access Control in Ad Hoc Networks,” Proc. ACM MobiCom, June 2002
[3] M. Takata, M. Bandai and T. Watanabe, "MAC Protocol with Directional Antennas for Deafness Avoidance in Ad Hoc Networks," Proc. IEEE GLOBECOM, pp , 2007
[4] G. Jakllari, J. Broustis, T. Korakis,S V. Krishnamurthy, and L. Tassiulas, "Handling Asymmetry in Gain in Directional Antenna Equipped Ad Hoc Networks," Proc. IEEE 16th International Symposium on PIMRC, pp
Slide 47
W. Y. Lee et. al 47