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

Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: A Wise AFH Solution for WPAN Date Submitted: November 1, 2001 Source: YC Maa, HK Chen, Shawn Liu and KC Chen Company : Integrated Programmable Communications, Inc.

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

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: A Wise AFH Solution for WPAN Date Submitted: November 1, 2001 Source:YC Maa, HK Chen, Shawn Liu and KC Chen Company: Integrated Programmable Communications, Inc. Address: Taiwan Laboratories Address: P.O. Box 24-226, Hsinchu, Taiwan 300 TEL +886 3 516 5106, FAX: +886 3 516 5108, E-Mail: {ycmaa, hkchen, shawnliu, kc}@inprocomm.com Re: [IEEE 802.15-00/367r1, IEEE 802.15-01/082r1, IEEE 802.15-01/246r1, IEEE 802.15-01/252r0, IEEE 802.15-01/366r1, IEEE 802.15-01/382r0, IEEE 802.15-01/385r0, IEEE 802.15-01/386r0, IEEE 802.15-01/443r0, IEEE 802.15-01/471r0, IEEE 802.15-01/491r0] Abstract: This document presents a wise AFH scheme for 802.15 TG2 Coexistence Mechanism . Purpose: Submission to TG2 for AFH draft consideration. 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. YC Maa et al., InProComm, Inc.

  2. A Wise AFH Solution for WPAN KC Chen,YC Maa, HK Chen, and Shawn Liu Integrated Programmable Communications, Inc. YC Maa et al., InProComm, Inc.

  3. Outline • Review on Channel Naming • Considerations • Regulation Change Effect • Implementation and Complexity • Conclusion and Recommendation • Appendix: Complexity Estimation for AFH YC Maa et al., InProComm, Inc.

  4. Review on Channel Naming YC Maa et al., InProComm, Inc.

  5. Review of AFH Channel Naming • Channels are classified into 3 groups: (dynamic classification) • Usablechannel setSU: uninterfered or “good” channels (size = NU) • Keptchannel setSK: interfered channels kept for AFH (size = NK) • Removedchannel setSR : interfered channels left out in AFH (size = NR) • NU + NK + NR = 79 • Define Nmin to be the minimum number of channels that a Bluetooth device must hop over. • Usable and Kept need to be considered, based on Nmin, NU: • Nmin NU: only use usable channels in the hopping sequence • Nmin> NU: require kept channels in addition to usable channels in the new hopping sequence, where kept channels NK= Nmin–NU • When kept channels are required, both “partition sequence” and “mapping” mechanisms are executed. • Mode L uses usable and “fill-in” channels blindly • When kept channels are not required, only “mapping” mechanism is executed. YC Maa et al., InProComm, Inc.

  6. Considerations YC Maa et al., InProComm, Inc.

  7. Worldwide Regulations • United States (FCC): • Currently FH devices must hop over a minimum of 75 channels. • NPRM suggests a new minimum hopset of 15 channels. • Two other proposed rule changes on the same NPRM • DSSS processing gain • new Digital Transmission Technologies (DTS) • Decision for ruling may drag on • Europe (ETSI): • FH devices must hop over a minimum of 20 channels, • France allows operation at 2.4465-2.4835 GHz, a total of 37MHz, but Bluetooth devices only use 23 channels. • Spain recently increased to a total of 79 channels • Japan: • No restriction on the minimum number of channels today. • Asia (especially China) • Rule change usually falls behind US or Europe by 2+ years. YC Maa et al., InProComm, Inc.

  8. Mode H & L under FCC/Global Regulation • Mode H works under current FCC regulation • Works for all Bluetooth devices (type 1, 2, 3) today • Will always work under FCC regulation, regardless what Nminmay be. • Mode L may not always work under current FCC • Does not work for type 1 & 2 Bluetooth devices (high power) • May work only for type 3 device (low power constraints) • May work better under future FCC regulation (if Nmin= 15) • Mode H always complies with current and future FCC/global regulation, while mode L does not • As the ISM band gets more crowded, the benefit of Mode H is more significant. YC Maa et al., InProComm, Inc.

  9. Important Usage Scenarios: Three 802.11b APs (01/443r0) • Agreed by all, including TI and Bandspeed, as very important scenario in Mar01 meeting. • Three collocated access points (on channel 1, 6, 11) will be common in the enterprise environment. • The three networks will occupy a total (30-dB) bandwidth of 66 MHz, which implies that these networks occupy 67 Bluetooth channels. • only 12 Bluetooth channels are free of interference (NU = 12). • if Nmin = 15, then we are forced to use 3 kept channels in the adapted hopping sequence. • if Nmin = 20 then we are forced to use 8 kept channels in the adapted hopping sequence. • Kept channels must be used intelligently, otherwise - • Higher packet error rate, which leads to unacceptable voice quality • Lower throughput. YC Maa et al., InProComm, Inc.

  10. Effects of the NPRM (01/443r0) • Proposed rules in NPRM are less strict than the current rules. • NPRM was issued to allow new modulation schemes, such as PBCC-22 and OFDM, into the 2.4 GHz band. • An OFDM signal has a larger bandwidth than the current IEEE 802.11b signals. • Spectral mask 20dB-Bandwidth: 22MHz • Spectral mask 28dB-Bandwidth: 40MHz • Thus, spectrum free of interference will become even more difficult to find! YC Maa et al., InProComm, Inc.

  11. Regulation Change Effect • New NPRM seems to justify Mode L. • Yet new application scenarios, enabled by NPRM - • Booming enterprise WLAN deployments • New technologies, such as OFDM, PBCC-22 will lead to a more crowded ISM band spectrum, which will not leave enough Usable channels for Mode L or FH schemes with small hopset! • Mode H is significantly more effective in a more crowded ISM band. YC Maa et al., InProComm, Inc.

  12. Implementation and Complexity • Implementation • One shot design vs. Incremental redesign • One-shot design • Design right at the first time • Works under any regulation • Incremental redesign • Occurs as regulation changes • Overwhelming effort and complexity at a great cost • Complexity • Relative complexity • In % gates to a typical implementation • In % MIPS to a typical mC processing power • Much cheaper than the incremental redesign cost!! YC Maa et al., InProComm, Inc.

  13. Complexity Estimates for mode H & L(01/471r0) • Examined: • Mapping & Partition functions • Software and hardware realizations • Left out: • Channel classification algorithm • Pseudo-random number generator • Assumption: • The basic time unit for AFH mechanisms is one slot – 625 us. YC Maa et al., InProComm, Inc.

  14. AFH Complexity Estimation Summary • Hardware complexity • mode H - 5.1K gates • mode L - 3.1K gates • Difference of 2k gates, or • 2% for a typical 100K-gate Bluetooth design, or • 0.4% for a typical 500K-gate co-located Bluetooth/WLAN design • Software complexity • mode H - 0.19~0.64 MIPS • mode L - 0.17 MIPS • up to 1.18% more, based on a 40-MIPS micro-controller • The added complexities are miniscule • Compared to today’s HW & SW design overall complexity • Compared to the overwhelming incremental-redesign costs • For details, please refer to Appendix YC Maa et al., InProComm, Inc.

  15. Conclusion & Recommendation YC Maa et al., InProComm, Inc.

  16. Conclusion and Recommendation (1) • NPRM leads to more crowded ISM band use • Booming enterprise WLAN deployments & new technologies, such as OFDM, PBCC-22 • Insufficient usable channels for mode L • Mode H not only conforms to current and future FCC regulation, but also adapts to future ISM band wireless boom. • Only < 2% complexity added by Partition Sequence, a universal design • spares a lot of re-design/re-spin cost and efforts. • works all over the world. YC Maa et al., InProComm, Inc.

  17. Conclusion and Recommendation (2) • AFH merger proposal (01/382r0) and AFH draft (01/491r0)- Wise AFH Solution for WPAN • Technically, intelligent AFH Scheme • Product-wise, deal with current and future market needs while avoiding re-design cost • Industry-wise, a wise decision to harmonize AFH schemes in 802.15 TG2 and Bluetooth SIG Coexistence WG YC Maa et al., InProComm, Inc.

  18. Appendix : Complexity Estimation for AFH YC Maa et al., InProComm, Inc.

  19. Appendix:Complexity Estimation for AFH • Examined: • Mapping & Partition functions • Software and hardware realizations • Left out: • Channel classification algorithm • Pseudo-random number generator • Assumption: • The basic time unit for AFH mechanisms is one slot – 625 us. YC Maa et al., InProComm, Inc.

  20. Software Implementation Assumption(1) • Division/Mod operation • A=B*Q+R, Q=floor(A/B), R = A mod B • It can be implemented in software by long-division. Each iteration requires 8 operations: • Two shift operations • One compare • One conditional jump • One subtraction, and one addition • Two instructions for loop: one subtraction, and one conditional jump • Number of iterations required is equal to the width ( number of bits) of A, WA. • The total instruction cycles required is roughly 8* WA. YC Maa et al., InProComm, Inc.

  21. Software Implementation Assumption(2) • Multiplication • Many processors have special instruction for multiplication (C=A*B). • If not, it can be implemented in software • Each iteration requires 5 operations: • Two shift operation • One conditional addition • Two instructions for loop: one subtraction, and one conditional jump • Number of iterations required is equal to min{WA ,WB} • The total instruction cycles required is roughly 5*(min{WA ,WB}) YC Maa et al., InProComm, Inc.

  22. Software Implementation: Mode L Mapping • Instructions • Mod operation x 1: • Assume 12-bits pseudo-random signal, thus 12-bit mod operation • 96 instruction cycles • Misc. instructions • Add/if-then-else/table-lookup/load-store variables • 10 instruction cycles • Totally 106 instruction cycles • Load • 106/625us = 0.1696 MIPS YC Maa et al., InProComm, Inc.

  23. Software Implementation: Mode H Partition Sequence-SCO (1) • For the first MAU (master-slave pair) • Distribution unit: Variables initial calculations • Six div/mod operations • 27bits x 1, 9bits x 1, 8bits x 1, 7bits x 3 • 8*(27+9+8+7*3)= 520 instruction cycles • Two multiplications • 2bits x 2 • 2*5*2=20 instructions cycles • Misc instructions(logic/compare/jump/add-sub/load) • 30 instruction cycles • Arrangement unit: • if-then-else/table-lookup • 10 instruction cycles • Totally 580 instruction cycles YC Maa et al., InProComm, Inc.

  24. Software Implementation: Mode H Partition Sequence-SCO (2) • For the remaining MAUs within one superframe • Distribution unit: • Variables update • 25 instructions cycles • Arrangement unit: • if-then-else/table-lookup • 10 instruction cycles • Totally 35 instruction cycles • For MAUs after one superframe • The partition sequence is periodic with superframe • The maximum length of superframe is 3*79 MAUs • Require 237 bits (about 30 bytes) to store one period • Table-lookup/index update: 10 instructions YC Maa et al., InProComm, Inc.

  25. Software Implementation: Mode H Mapping • Instructions • Mod operation x 1: • Assume 12-bits pseudo-random signal, thus 12-bit mod operation • 96 instruction cycles • Misc instructions • Add/if-then-else/table-lookup/load-store variables • 15 instruction cycles • Totally 111 instruction cycles • Load • 111/625us = 0.1776 MIPS YC Maa et al., InProComm, Inc.

  26. Software Implementation: Mode H • The complexity of mode H is the sum of mapping and partition sequence • Note that partition sequence is not calculated every slot, but every MAU (two slots) • For the first MAU: • 0.1776MIPS + 580/(625us*2) = 0.6416 MIPS • For the remaining MAUs within one superframe • 0.1776MIPS + 35/(625us*2) = 0.2056 MIPS • After one superframe • 0.1776MIPS + 10/(625us*2) = 0.1856 MIPS YC Maa et al., InProComm, Inc.

  27. Hardware Implementation Assumption(1) • Unit of gate count: NAND gate. • Use one hardware block for multiple occurrences of the same operation. • Ex: there may be several mod operations, but only one div/mod hardware is needed. • Variable storage/mapping table: 4 gates per bits. • Division/Mod operation • A=B*Q+R, Q=floor(A/B), R = A mod B • It can be implemented in hardware by long-division: • Multiple clock implementation, shift-in one bit of operand “A” at each clock. • Require WA clocks to finish one operation. • Gate count required is in proportional to WB . YC Maa et al., InProComm, Inc.

  28. Hardware Implementation: Mode L Mapping • Hardware blocks: • Adder • 12-bits • Gate count = 0.1K • Mod • WB=7 • Gate count = 1K • Mapping table • 79*7 bits • Gate count = 2K • Total gate count = 3.1K YC Maa et al., InProComm, Inc.

  29. Hardware Implementation: Mode H Mapping • Hardware blocks: • Adder • 12-bits • Gate count = 0.1K • Mod • WB=7 • Gate count = 1K • Mapping table • 79*7 bits • Gate count = 2K • Misc • 0.2 K • Total gate count = 3.3K YC Maa et al., InProComm, Inc.

  30. Hardware Implementation: Mode H Partition Sequence • Hardware blocks: • Multiplier: 8bit x 8 bit, parallel multiplier • Gate count = 0.5K • Division/Mod • WB=8 • Gate count = 1K • Add/Sub • Gate count = 0.1K • Variable storage and procedure control • Gate count = 1K • Misc • Gate count = 0.2K • Total gate count = 2.8 K YC Maa et al., InProComm, Inc.

  31. Hardware Implementation: Mode H • The complexity of mode H is the sum of mapping and partition sequence • Direct summation of the two gate count numbers: 3.3K + 2.8K = 6.1K • Note that the mod/division block can be further shared • Gate count can be reduced to 5.1K YC Maa et al., InProComm, Inc.

  32. Complexity Considerations with Reference Numbers for Bluetooth • The hardware implementation of LC is about 70K-100K gates • The computation power required for LMP, L2CAP, and HCI is about 10 ~ 20 MIPs, while typical processors can easily provide up to 40 MIPs. • The complexity added, in software or hardware, is miniscule! YC Maa et al., InProComm, Inc.

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