1. September, 2001
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Adaptive Frequency Hopping - An instant channel replacement approach ]
Date Submitted: [August, 2001]
Source: [H. Gan, V. Sapozhnykov, B. Treister, E. Skafidas, et. al.] Company [Bandspeed Inc.]
Address [Level 9, 500 Collins Street, Melbourne, Victoria, Australia]
Voice:[ , FAX: [ ]
[h.gan, b.treister,
Re: [A new simple approach for adaptive frequency hopping]
Abstract: [This document describes a new simple approach for adaptive frequency hopping, an instant channel replacement to intelligently use bad channels in the hopping sequence]
Purpose: [Introducing a new approach for adaptive frequency hoping to include in ]
Notice: This document has been prepared to assist the IEEE P It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
H. Gan, V. Sapozhnykov, B. Treister, et. al.

2. September, 2001
Adaptive Frequency Hopping (AFH) - A Simple Instant Channel Replacement Approach
Hongbing Gan, Vitaliy Sapozhnykov, Bijan Treister, Stan Skafidas, et. al.
Bandspeed Inc.
H. Gan, V. Sapozhnykov, B. Treister, et. al.

3. Outline Benefits of the AFH approach
September, 2001
Outline
Benefits of the AFH approach
Basic principle of the new AFH approach
Processing flowchart and table
Conclusion
Appendix:
Case study - Bluetooth and IEEE b coexistence
AFH implementation steps
Message Sequence Chart
Simulation results
References
H. Gan, V. Sapozhnykov, B. Treister, et. al.

4. Definition of Channel Pair
September, 2001
A channel pair is comprised of two channels:
First channel, Master Tx/Slave Rx channel, at even-numbered timeslot
Second channel, Slave Tx/Master Rx, ie, Slave return channel, at odd-numbered timeslot
Channel pair
Channel pair
Master Tx Rx Tx Rx f1 f3 f2 f4
Slave Rx Tx Rx Tx
Even-numbered
Timeslot
Odd-numbered
Timeslot
Even-numbered
Timeslot
Odd-numbered
Timeslot
H. Gan, V. Sapozhnykov, B. Treister, et. al.

5. Definitions N: Total number of hopping channels
September, 2001
Definitions
Definitions:
N: Total number of hopping channels
Nmin: Minimum number of channels to be used, set by regulations such as FCC
G: Good channel
B: Bad channel
N = Total number of G + Total number of B
BN: Bad channel to be removed legally from the hopping sequence
BK: Bad channel to keep in the hopping sequence
H. Gan, V. Sapozhnykov, B. Treister, et. al.

6. Benefits of the New AFH Approach
<month year>
doc.: IEEE <doc#>
September, 2001
Benefits of the New AFH Approach
Channel replacement on a per channel pair basis instantly
Simple to process, easy to implement, easy to integrate
Low memory or gate requirement
Significant performance improvement for all coexisting systems
Fully backward compatible with legacy devices
Master’s Tx channels are kept in the original positions in the hoping sequence, good for piconet synchronization, broadcast, Park mode beacon channel, etc.
Legacy devices also benefits from the new AFH approach
H. Gan, V. Sapozhnykov, B. Treister, et. al.
<author>, <company>

7. Basic Principle of the New AFH Approach
September, 2001
Basic Principle of the New AFH Approach
H. Gan, V. Sapozhnykov, B. Treister, et. al.

8. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
September, 2001
Purpose of AFH
Remove as many Bad channels as legally possible
The AFH uses only Good channels if all Bad channels can be removed legally
If some Bad channels still have to be used to meet regulation requirements, intelligently use the remaining Bad channels
Backward compatible with legacy devices
Throughput improvement for both AFH-enhanced and legacy devices, and minimize interference to other coexisting systems such as IEEE b WLAN
H. Gan, V. Sapozhnykov, B. Treister, et. al.
<author>, <company>

9. Four kinds of Channel pair
September, 2001
Four kinds of Channel pair
‘Good Bad’ channel pair, the packet needs retransmission from Master because of the Bad slave return channel, waste of a good channel
‘Bad Good’, Slave receives incorrectly, nothing returned to Master, waste of a good channel
‘Bad Bad’ channel pair, Slave receives incorrectly, nothing returned to Master
ONLY ‘Good Good’ channel pair, can secure a transaction between Master and Slave
H. Gan, V. Sapozhnykov, B. Treister, et. al.

10. General Principle of AFH (Simple Illustration)
September, 2001
General Principle of AFH (Simple Illustration) G B
Old
Pass
Blocked
Re-transmission
New
Original ‘Good Good’ and ‘Bad Bad’ channel pairs are kept in their original positions in the hopping sequence
‘Good Bad’ channel pairs are instantly replaced to ‘Good Good’ channel pairs
‘Bad Good’ channel pairs are instantly replaced to ‘Bad Bad’ channel pair
Throughput improved due to newly created ‘Good Good’ channel pairs
H. Gan, V. Sapozhnykov, B. Treister, et. al.

11. General Principle of AFH
September, 2001
General Principle of AFH
For each channel pair, starting from Master Tx channel:
Removing BN by replacing it with a randomly selected G or BK, to maintain equal usage of G and BK
Whenever Master Tx channel is OR replaced to G, replace the Slave return channel to G if it is BN or BK originally, to form a ‘G G’ channel pair and secure a transaction
Whenever Master Tx channel is OR replaced to BK, replace the Slave return channel to BK if it is BN or G originally, to form a ‘BK BK’ channel pair, to remove BN and save a usage of G
Channel replacement on a per channel pair basis
H. Gan, V. Sapozhnykov, B. Treister, et. al.

12. Simple AFH Processing Table
September, 2001
Simple AFH Processing Table
In case Master TX BN
replaced with a G
In case Master TX BN
replaced with a BK
When NO BK, Case 1, 3 ,4, 6 are processed
When NO BN, Case 1, 2, 10, 11 are processed
H. Gan, V. Sapozhnykov, B. Treister, et. al.

13. Example Portion of Original and AFH Hopping Sequence
September, 2001
Example Portion of Original and AFH Hopping Sequence G G BK G BN BN G BN BK BN G BK G G BK G BK BN G G BN G
AFH G G G G G G G BK G BK G BK G G
In this example, 7 more ‘Good Good’ channel pairs are created
H. Gan, V. Sapozhnykov, B. Treister, et. al.

14. Three Scenarios to consider
September, 2001
Three Scenarios to consider
Scenario 1:
BN = 0, Bk > 0, all Bad channels are kept, the AFH intelligently use BK in the new hopping sequence
Scenario 2:
BN > 0, BK > 0, the AFH replaces BN with good channels G or BK, and intelligently use BK in the new hoping sequence
Scenario 3: (Ideal scenario)
BN > 0, BK = 0, all Bad channels are replaced with Good channels in the new hopping sequence
H. Gan, V. Sapozhnykov, B. Treister, et. al.

15. September, 2001
Scenario 1: BN = 0, Bk > 0
All Bad channels are kept, the AFH intelligently use BK in the new hopping sequence
H. Gan, V. Sapozhnykov, B. Treister, et. al.

16. Channel Pair in the Bluetooth Hopping Sequence - Case 1
September, 2001
Channel Pair in the Bluetooth Hopping Sequence - Case 1
Master Tx Rx
‘Good Good’ channel pair
Master Tx channel Good
Slave return channel Good
Traffic transmission successful
Ideal case G G
Slave Rx Tx
H. Gan, V. Sapozhnykov, B. Treister, et. al.

17. Channel Pair in the Bluetooth Hopping Sequence - Case 2
September, 2001
Channel Pair in the Bluetooth Hopping Sequence - Case 2
‘Good Bad’ channel pair
Master Tx channel Good
Slave return channel Bad
Traffic from master to slave not acknowledged (ACKed), the same payload will be re-transmitted until master gets positive ACK from the slave through a Good return channel
Traffic can be flushed after a timeout
Waste Good channels
Master Tx Rx G BK
Slave Rx Tx
H. Gan, V. Sapozhnykov, B. Treister, et. al.

18. Channel Pair in the Bluetooth Hopping Sequence - Case 3
September, 2001
Channel Pair in the Bluetooth Hopping Sequence - Case 3
‘Bad Good’ channel pair
Master Tx channel Bad
Slave return channel Good
Slave receives incorrectly; access code correlation does not trigger; or HEC does not check; nothing will returned to master.
Waste a Good slave return channel
Master Tx Rx BK G
Slave Rx Tx
H. Gan, V. Sapozhnykov, B. Treister, et. al.

19. Channel Pair in the Bluetooth Hopping Sequence - Case 4
September, 2001
Channel Pair in the Bluetooth Hopping Sequence - Case 4
Master Tx Rx
‘Bad Bad’ channel pair
Master Tx channel Bad
Slave return channel Bad
Slave receives incorrectly, access code correlation does not trigger, or HEC does not check, nothing will returned to master. BK BK
Slave Rx Tx
H. Gan, V. Sapozhnykov, B. Treister, et. al.

20. Intelligent Use of Bad Channels in the Hopping Sequence
September, 2001
Intelligent Use of Bad Channels in the Hopping Sequence
H. Gan, V. Sapozhnykov, B. Treister, et. al.

21. September, 2001
H. Gan, V. Sapozhnykov, B. Treister, et. al.

22. September, 2001
Example of Channel Pairs Before and After Intelligent Use of Bad Channels
Channel pairs in the original hopping sequence
Channel pairs after intelligent use of Bad channels
H. Gan, V. Sapozhnykov, B. Treister, et. al.

23. Simple Illustrations of How to Use Bad Channels Intelligently
September, 2001
Simple Illustrations of How to Use Bad Channels Intelligently
Master
Please run full screen slide show for animation !!
Slave G G Tx Rx G G BK Rx Tx G
Bank of G
Bank of BK
H. Gan, V. Sapozhnykov, B. Treister, et. al.

24. Simple Illustrations of How to Use Bad Channels Intelligently
September, 2001
Simple Illustrations of How to Use Bad Channels Intelligently
Master
Slave BK BK Tx Rx BK G Bk Rx BK Tx
Bank of G
Bank of BK
H. Gan, V. Sapozhnykov, B. Treister, et. al.

25. Benefits of the Intelligent Use of Bad Channels
September, 2001
Benefits of the Intelligent Use of Bad Channels
Channel replacement on a per channel pair basis instantly
Processing is very simple, very easy to implement (*See processing flowchart and pseudo-code)
No long dead time
Fully backward compatible
Master’s Tx channels are kept in the original positions, good for piconet synchronization, broadcast, Park mode beacon channel, and most importantly, support legacy devices, etc.
H. Gan, V. Sapozhnykov, B. Treister, et. al.

26. Estimate of Throughput Improvement
September, 2001
Estimate of Throughput Improvement
Assuming channels 2/3 good, 1/3 bad, 100% duty cycle G G BK BK G BK
Old
Pass
Re-transmission
Blocked
Blocked
4/ / / /9
New G G BK BK
Pass
Pass
Blocked
Blocked
4/ / / /9
Estimated throughput Improvement: 50%
H. Gan, V. Sapozhnykov, B. Treister, et. al.

27. Estimate of Throughput Improvement
September, 2001
Estimate of Throughput Improvement
Assuming channels 1/2 good, 1/2 bad, 100% duty cycle
Old G G BK BK G BK
Pass
Re-transmission
Blocked
Blocked
1/ / / /4
New G G BK BK
Pass
Pass
Blocked
Blocked
1/ / / /4
Estimated Throughput Improvement: 100%
H. Gan, V. Sapozhnykov, B. Treister, et. al.

28. Scenario 2: BN > 0, Bk > 0
September, 2001
Scenario 2: BN > 0, Bk > 0
AFH replaces BN (which can be removed legally) with randomly selected good channel G or BK in the hopping sequence (See next few slides)
AFH intelligently use BK, the same method as in Scenario 1
On a per channel pair basis
H. Gan, V. Sapozhnykov, B. Treister, et. al.

29. September, 2001
H. Gan, V. Sapozhnykov, B. Treister, et. al.

30. September, 2001
H. Gan, V. Sapozhnykov, B. Treister, et. al.

31. September, 2001
Example channel pairs Before and After Replacing BN and Intelligent Using BK
H. Gan, V. Sapozhnykov, B. Treister, et. al.

32. Replacing BN and Intelligent Using BK on a per channel pair basis
September, 2001
Replacing BN and Intelligent Using BK on a per channel pair basis
Master
Slave G G Tx Rx G BN
or Bk G Rx G Tx
Bank of G
Bank of Bk
H. Gan, V. Sapozhnykov, B. Treister, et. al.

33. September, 2001
Replacing BN with G and Intelligent Using BK on a per channel pair basis
Master
Slave BN G Tx Rx G BN
or Bk G Rx G Tx
Bank of G
Bank of Bk
H. Gan, V. Sapozhnykov, B. Treister, et. al.

34. September, 2001
Replacing BN with BK and Intelligent Using BK on a per channel pair basis
Master
Slave BN BK Tx Rx BK G
or BN BK Rx BK Tx
Bank of G
Bank of Bk
H. Gan, V. Sapozhnykov, B. Treister, et. al.

35. Replacing BN and Intelligent Using BK on a per channel pair basis
September, 2001
Replacing BN and Intelligent Using BK on a per channel pair basis
Master
Slave Bk Bk Tx Rx Bk G
or BN Bk Rx Bk Tx
Bank of G
Bank of Bk
H. Gan, V. Sapozhnykov, B. Treister, et. al.

36. September, 2001
Scenario 3: BN > 0, Bk = 0
AFH replaces BN (which can be removed legally) with good channels
On a per channel basis, i.e., whenever the selection kernel outputs a BN, replace it with a good channel.
As BK =0, only good channels are used in the hopping sequence
H. Gan, V. Sapozhnykov, B. Treister, et. al.

37. September, 2001
H. Gan, V. Sapozhnykov, B. Treister, et. al.

38. Replacing BN instantly with good channels
September, 2001
Replacing BN instantly with good channels
H. Gan, V. Sapozhnykov, B. Treister, et. al.

39. Replacing BN with good channels
September, 2001
Replacing BN with good channels
Master
Slave
Please run full screen slide show for animation !! G G Tx Rx G G BN Rx Tx G
Bank of G
H. Gan, V. Sapozhnykov, B. Treister, et. al.

40. Replacing BN with good channels
September, 2001
Replacing BN with good channels
Master
Slave
Please run full screen slide show for animation !! BN G Rx Tx G G BN Rx Tx G
Bank of G
H. Gan, V. Sapozhnykov, B. Treister, et. al.

41. AFH Processing Flowchart
<month year>
doc.: IEEE <doc#>
September, 2001
AFH Processing Flowchart
Step 1: Determine exactly which channels belong to good channel G, bad channel to remove BN, and bad channel to keep BK
Step 2:
For Master Tx/Slave Rx timeslots, use flowchart A
For Slave Tx/Master Rx timeslots, use flowchart B
H. Gan, V. Sapozhnykov, B. Treister, et. al.
<author>, <company>

42. Simple AFH Processing Table
September, 2001
Simple AFH Processing Table
In case Master TX BN
replaced with a G
In case Master TX BN
replaced with a BK
When NO BK, Case 1, 3 ,4, 6 are processed
When NO BN, Case 1, 2, 10, 11 are processed
H. Gan, V. Sapozhnykov, B. Treister, et. al.

43. September, 2001
Flowchart A:
Used for Master Tx/Slave Rx timeslots, i.e., Even-numbered timeslot
H. Gan, V. Sapozhnykov, B. Treister, et. al.

44. September, 2001
Flowchart B:
Used for Slave Tx/Master Rx timeslots, i.e., Odd-numbered timeslot
H. Gan, V. Sapozhnykov, B. Treister, et. al.

45. Conclusion AFH removes as many Bad channels as legally possible
September, 2001
Conclusion
AFH removes as many Bad channels as legally possible
Kept Bad channels are intelligently used in the hopping sequence
The AFH works on a per ‘Master Transmits, then Slave Return’ channel pair basis
Simple to process, easy to implement, easy to integrate
Low memory and gate requirement
Significant performance improvement for all coexisting systems
Fully backward compatible with legacy devices
Legacy devices also benefits from the AFH approach
H. Gan, V. Sapozhnykov, B. Treister, et. al.

46. Appendix Case study - Bluetooth and IEEE 802.11b coexistence
September, 2001
Appendix
Case study - Bluetooth and IEEE b coexistence
Implementation steps
Message Sequence Chart
Simulation results
References
H. Gan, V. Sapozhnykov, B. Treister, et. al.

47. September, 2001
Case Study - Bluetooth and Wi-fi IEEE b WLAN coexist (1) Low power Bluetooth devices (2) High power bluetooth devices
H. Gan, V. Sapozhnykov, B. Treister, et. al.

48. Current FCC Regulations
September, 2001
Current FCC Regulations
For high power (> 1mW) Bluetooth devices in USA
A minimum of 75 channels should be used
For low power (< 1mW) Bluetooth devices, no restriction
FCC will allow as less as 15 channels for high power Bluetooth devices
H. Gan, V. Sapozhnykov, B. Treister, et. al.

49. Regulations in other countries
September, 2001
Regulations in other countries
How about regulation requirements in
Europe
Asia
Australia
etc.
Do we have to use a minimum of 75 channels in all countries for high power devices?
H. Gan, V. Sapozhnykov, B. Treister, et. al.

50. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
September, 2001
Coexistence between Bluetooth and IEEE b
802.11b
Assuming IEEE b occupies Bluetooth channel 0-22, for Bluetooth, channel 0-22 become Bad
…… … ……… ……
(Occupied by b)
Bluetooth / Channels
H. Gan, V. Sapozhnykov, B. Treister, et. al.
<author>, <company>

51. (1) Low power Bluetooth Devices coexists with IEEE 802.11b WLAN
September, 2001
(1) Low power Bluetooth Devices coexists with IEEE b WLAN
BN = Channel 0-22, Bk = Non (Scenario 3)
Whenever the selection kernel outputs a bad channel, AFH just replaces the bad channel with a randomly selected good channel
All bad channels are removed from the hopping sequence
H. Gan, V. Sapozhnykov, B. Treister, et. al.

52. (1) Low power Bluetooth Devices coexists with IEEE 802.11b WLAN
September, 2001
(1) Low power Bluetooth Devices coexists with IEEE b WLAN
Sample data of next slide from Page 968 of Bluetooth Specification 1.1
CLK start: 0x
ULAP: 0x6587cba9
IEEE b occupies Bluetooth channel 0-22,
Channels 0-22 are replaced with good channels, so only good channels are used in the hopping sequence for low power Bluetooth devices
(See sample data next slide)
H. Gan, V. Sapozhnykov, B. Treister, et. al.

53. Channels 0-22 will be replaced with randomly selected good channels
September, 2001
Channels 0-22 will be replaced with randomly selected good channels
H. Gan, V. Sapozhnykov, B. Treister, et. al.

54. (2) High Power Bluetooth Devices Coexist with IEEE 802.11b
September, 2001
(2) High Power Bluetooth Devices Coexist with IEEE b
High power Bluetooth devices can remove up to 4 channels occupied by IEEE b to meet FCC Nmin = 75 requirement
For high power Bluetooth devices, it has to keep at least 19 channels occupied by IEEE b
To simplify, in this example, all bad channels are kept, Bk = channel 0-22, fitting to scenario 1.
AFH intelligently use BK
On a per channel pair basis
H. Gan, V. Sapozhnykov, B. Treister, et. al.

55. (2) High Power Bluetooth Devices coexists with IEEE 802.11b WLAN
September, 2001
(2) High Power Bluetooth Devices coexists with IEEE b WLAN
IEEE b occupies Bluetooth channel 0-22,
channels 0-22 are intelligently used in the hopping sequence
Original ‘Good Good’ and ‘Bad Bad’ channel pairs are kept in the same positions as in the original hopping sequence
‘Good Bad’ channel pairs are replaced instantly to ‘Good Good’ channel pairs to make a successful transaction
‘Bad Good’ channel pairs are replaced instantly to ‘Bad Bad’ channel pairs to save a good channel
Channel replacement on a per channel pair basis
(See sample data next slide, from P968 of Bluetooth Specification 1.1)
H. Gan, V. Sapozhnykov, B. Treister, et. al.

56. 42 ‘Good Bad’ channel pairs out of 224 will be replaced instantly to ‘Good Good’ channel pairs
September, 2001
Sample data
‘Good Good’ and ‘Bad Bad’ channel pairs are kept in the same positions
H. Gan, V. Sapozhnykov, B. Treister, et. al.

57. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
44 ‘Bad Good’ channel pairs out of 224 will be replaced instantly to ‘Bad Bad’ channel pairs to save good channels
September, 2001
Sample data
‘Good Good’ and ‘Bad Bad’ channel pairs are kept in the same positions
H. Gan, V. Sapozhnykov, B. Treister, et. al.
<author>, <company>

58. Estimate of Throughput Improvement
September, 2001
(2) High Power Bluetooth Devices coexists with IEEE b WLAN
Estimate of Throughput Improvement
50%
H. Gan, V. Sapozhnykov, B. Treister, et. al.

59. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
September, 2001
Implementation Steps of AFH
1. Collect channel performance statistics
2. Classify channels as ‘Good’ or ‘Bad’
3. Collect slaves’ channel classifications (optional)
4. Synchronize Channel Classifications with slaves
6. Implementing adaptive hopping (Scenario 1, 2, 3)
7. Switching back to normal hopping
8. Repeat the above process
H. Gan, V. Sapozhnykov, B. Treister, et. al.
<author>, <company>

60. Pseudo-code & Simulation Results
September, 2001
Pseudo-code & Simulation Results
(Will provide ASAP)
H. Gan, V. Sapozhnykov, B. Treister, et. al.

61. Message Sequence Chart
September, 2001
Message Sequence Chart
H. Gan, V. Sapozhnykov, B. Treister, et. al.

62. Message Sequence Chart
<month year>
doc.: IEEE <doc#>
September, 2001
Message Sequence Chart
Slaves
Master
Slaves
LMP_Available_Channel_Request
LMP_Slave_Available_Channel ( )
LMP_Slave_Available_Channel ( )
H. Gan, V. Sapozhnykov, B. Treister, et. al.
<author>, <company>

63. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
September, 2001
Slaves
Master
Slaves
LMP_Adaptive_Hopping_Request ( )
LMP_Accepted
LMP_Not_Accepted
AFH
Timeout
LMP_Normal_Hopping
LMP_Accepted
Start Over, Re-classify channels
H. Gan, V. Sapozhnykov, B. Treister, et. al.
<author>, <company>

64. September, 2001
References
K. C. Chen, et al., Merged IPC and TI Adaptive Frequency Hopping Proposal [IEEE /246r1]
K. C. Chen, H. K. Chen, C. C. Chao, Selective Hopping for Hit Avoidance [IEEE /057r2]
A. Batra, K. Anim-Appiah, J.-M. Ho, An Intelligent Frequency Hopping Scheme for Improved Bluetooth Throughput in an Interference-Limited Environment [IEEE /082r1]
H. B. Gan et al., Adaptive Frequency Hopping [IEEE /367r1]
H. Gan, V. Sapozhnykov, B. Treister, et. al.