Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Adaptive Frequency Hopping - An Simple Instant Channel Replacement Approach for both ACL and SCO Links] Date Submitted: [September, 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:[61 3 9614 6299 , FAX: [61 3 9614 6699] E-Mail:[h.gan, b.treister, v.sapozhnykov@bandspeed.com.au] Re: [A Simple Approach for Adaptive Frequency Hopping, as a non-collaborative coexistence mechanism] 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 802.15.2] Notice: This document has been prepared to assist the IEEE P802.15. 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 P802.15. H. Gan, V. Sapozhnykov, et. al.

2. Adaptive Frequency Hopping (AFH) - A Simple Instant Channel Replacement Approach for both ACL and SCO Hongbing Gan, Vitaliy Sapozhnykov, Bijan Treister, Stan Skafidas, et. al. Bandspeed Inc. H. Gan, V. Sapozhnykov, et. al.

3. Benefits of the Simple AFH Approach Mechanism • Channel replacement on a per channel pair basis instantly, NO complicated ACL and SCO partition sequence generator is needed. • A simple AFH mechanism to cover all traffic types (ACL, SCO, Mixed ACL/SCO), high priority traffic such as SCO can get more good channels • A simple AFH to cover both low power and high power modes • Better backward compatibility with legacy devices • Master’s Transmitting Good channels are kept in the original positions in the hoping sequence, good for piconet synchronization, broadcast, Park mode, Sniff mode, beacon channel, etc. • Legacy devices also benefits from the new AFH approach • Random number generator seamlessly integrated • A harmonized simple AFH mechanism H. Gan, V. Sapozhnykov, et. al.

4. Definition of Channel Pair 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, i.e., 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 Odd-numbered Timeslot Even-numbered Timeslot Odd-numbered Timeslot Even-numbered Timeslot H. Gan, V. Sapozhnykov, et. al.

5. 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 • BN: Bad channel to be removed legally from the hopping sequence • BK: Bad channel to keep in the hopping sequence • NG, NB, NBN, NBK: Number of good channel, Number of bad channel, Number of bad channel to remove, Number of bad channel to keep, respectively • N = NG + NB • NB = NBK + NBN H. Gan, V. Sapozhnykov, et. al.

6. AFH Covers All Possible Channel Classification Scenarios • Scenario 1: NBN > 0, NBK= 0 (Ideal scenario) • All Bad channels are replaced with Good channels in the new hopping sequence • (e.g., in low power mode, all bad channels removed, or once FCC law changed for high power devices) • Scenario 2: NBN > 0, NBK > 0, • AFH removes BN , replaces it with randomly selected good channels G or BK (to maintain equal channel usage of G and BK), • AFH intelligently use BK in the new hoping sequence • (e.g., in high power mode, a maximum of 4 channels can be removed, the rest bad channels if any have to be kept) H. Gan, V. Sapozhnykov, et. al.

7. AFH Covers All the Traffic Types H. Gan, V. Sapozhnykov, et. al.

8. AFH Approach - Standard Instant Channel Replacement (Standard ICR) (Details in IEEE 802.15 Document 01/435r0, 01/438r0) H. Gan, V. Sapozhnykov, et. al.

9. G B G B G G B B G B B G B G B G Principle of Standard ICR Pass Re-transmission Blocked Blocked Original New Pass Pass Blocked Blocked • 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, et. al.

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

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

12. Standard ICR 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, et. al.

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

14. AFH Approach - ‘Fit Best’ Instant Channel Replacement (Fit Best ICR) The only difference from Standard ICR is that higher priority traffic such as SCO voice link can have more good channels H. Gan, V. Sapozhnykov, et. al.

15. How Fit Best ICR works • At higher priority timeslots such as reserved HV2 SCO timeslots: • Case 1: ‘Good Good’ ‘Good Good’ • Case 2: ‘Good Bad’ ‘Good Good’ • Case 3: ‘Bad Good’‘Good Good’ • Case 4: ‘Bad Bad’ ’Good Good’ • For every Case 3 replacement, a Good Channel Usage Debt (GUD) Counter is incremented by 1; For every Case 4 replacement, the GUD Counter is incremented by 2. • At lower priority timeslots, if there is any GUD debt, it must be repaid • ‘Good Bad’ ‘Bad Bad’ , to repay the GUD by 1; • ‘Good Good’ ‘Bad Bad’, to repay the GUD by 2. • If No GUD debt, just do standard ICR. • GUD balance is always towards ZERO, to maintain equal channel usage H. Gan, V. Sapozhnykov, et. al.

16. Fit Best ICR Processing Table At timeslots for higher priority traffic, such as voice HV2 Repay the debt At timeslots for lower priority traffic Repay the Good Channel Usage Debt (GUD) H. Gan, V. Sapozhnykov, et. al.

17. Guaranteed GUD Convergence • If Number of Good Channels (NG) is enough to fill high priority traffic such as HV2, GUD converges. • For example, NG > NBK, as HV2 take 50% of timeslots, then all HV2 slots are filled with Good channels. • If Number of Good Channels (NG) is NOT enough to fill high priority traffic such as HV2, GUD STILL converges. • Why GUD still converges? By saving Good channel usage first at ACL timeslots, then use the Good channels in the HV2 timeslots • Just like a Savings account • For example, 40% of channels are Good, 60% are Bad, HV2 takes 50% timeslots, all Good channels are fitted to HV2 slots, then 80% of HV2 slots are fitted with Good channels H. Gan, V. Sapozhnykov, et. al.

18. In Case Not Enough Good Channels • At lower priority timeslots, save good channel usage for high priority timeslots • ‘Good Bad’ ‘Bad Bad’, Decrease GUD by 1, i.e. save 1 good usage; • ‘Good Good’ ‘Bad Bad’, Decrease GUD by 2, i.e. save 2 good usage; • ‘Bad Good’ ‘Bad Bad’ • ‘Bad Bad’ ‘Bad Bad’ • At higher priority timeslots such as reserved HV2 SCO timeslots: • Case 1: ‘Good Good’ ‘Good Good’ • Case 2: ‘Good Bad’ ‘Good Good’ • Case 3: ‘Bad Good’, if GUD < -1, ‘Good Good’, increment GUD by 1 • if GUD > -1, ‘Bad Bad’ • Case 4: ‘Bad Bad’, if GUD < -1, ’Good Good’, increment GUD by 2 • if GUD > -1, ‘Bad Bad’ • GUD is always converged towards ZERO, to maintain equal channel usage H. Gan, V. Sapozhnykov, et. al.

19. General Principle of Fit Best ICR • For HV2 and HV3 link: • Fit the best channels to channel pairs of the reserved SCO Timeslots • For mixed SCO + ACL: • Fit the best channels to channel pairs of the reserved SCO Timeslots, if SCO has higher priority • Fit the best channels to channel pairs of the ACL Timeslots, if ACL has higher priority • Use Standard ICR if neither ACL nor SCO has higher priority H. Gan, V. Sapozhnykov, et. al.

20. T T T T T T T T T T T T R R R R R R R R R R R R Mixed SCO (HV2, HV3) and ACL Links HV2 ACL HV2 ACL HV2 ACL HV2 reserves half Timeslots, transmits every four Timeslots HV3 ACL ACL HV3 ACL ACL HV3 reserves one third Timeslots, transmits every six Timeslots H. Gan, V. Sapozhnykov, et. al.

21. G G BK G BK BK G G G G BK G G BK G BK BK G G BK G BK BK BK G G G G G BK BK BK G G G BK BK G G G BK BK G G BK G BK G G BK G G G BK G G How Fit Best ICR works(Assuming HV2 has higher priority) ACL HV2 ACL HV2 ACL HV2 HV2 1 2 3 4 5 6 7 ACL HV2 ACL HV2 ACL HV2 ACL 8 9 10 11 12 13 14 AFH ACL HV2 ACL HV2 ACL HV2 HV2 1 2 3 4 5 6 7 ACL HV2 ACL HV2 ACL HV2 ACL 8 9 10 11 12 13 14 H. Gan, V. Sapozhnykov, et. al.

22. Summary: AFH Approach v.s. Traffic Type H. Gan, V. Sapozhnykov, et. al.

23. Conclusion • A simple AFH mechanism to cover all traffic types (ACL, SCO, Mixed ACL/SCO), high priority traffic such as SCO can get more good channels • A simple AFH to cover both low power and high power modes • AFH removes as many Bad channels as legally possible • Kept Bad channels are intelligently used in the hopping sequence • The AFH channel replacement works on a per channel pair basis instantly, NO complicated ACL and SCO partition sequence generator is needed. • Better backward compatibility with legacy devices. Master’s Tx Good channels are kept in the original positions in the hoping sequence, good for piconet synchronization, broadcast, Park mode, Sniff mode, beacon channel, etc. • Legacy devices also benefits from the new AFH approach • A harmonized simple AFH mechanism H. Gan, V. Sapozhnykov, et. al.