1. doc.: IEEE 802.15-09-0215-00-004e Submission Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Channel Diversity Sub group Report] Date Submitted: [March 11, 2009] Source: [Wun-Cheol Jeong, Chol Su Kang, Kuor-Hsin Chang, José A. Gutierrez, Ludwig Winkel, Rick Enns, Myung Lee, Tae Rim Park, Betty Zhao, Ghulum Bhatti, Ning Gu, Jie Shen, Wei Hong, Qin Wang] Address [] Voice:[+82-42-860-5104], FAX: [], E-Mail:[wjeong@etri.re.kr] Re: [IEEE P802.15.4e] Abstract:[ This document is a report of channel diversity subgroup for IEEE 802.15.4e.] Purpose:[Discussion in 802.15.4e Task Group] 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. Slide 1Channel Diversity

2. doc.: IEEE 802.15-09-0215-00-004e Submission March, 2009 Slide 2 Channel Diversity Subgroup Report ETRI, Dust Networks, Freescale, Emerson, Siemens, CUNY, MERL, Huawei, Samsung, Arch Rock, SIMIT, Vino, USTB, SIA Channel Diversity

3. doc.: IEEE 802.15-09-0215-00-004e Submission Contributors ETRI: Wun-Cheol Jeong, Changsub Shin, Anseok Lee, Seong-Soon Joo Dust Networks: Chol Su Kang, Kris Pister (UC Berkeley) Freescale: Kuor-Hsin Chang, Clinton Powell Emerson: José A. Gutierrez Siemens: Ludwig Winkel Rick Enns: Consultant CUNY MERL Huawei Samsung Arch Rock SIMIT Vino USTB SIA Slide 3Channel Diversity March, 2009

4. doc.: IEEE 802.15-09-0215-00-004e Submission Table of Contents 1.Description of Channel Diversity 2.Anticipated Changes 3.Backward Compatibility Slide 4Channel Diversity March, 2009

5. doc.: IEEE 802.15-09-0215-00-004e Submission Description of Channel Diversity Wireless channel introduces uncertainty due to the nature of wireless medium. “Diversity” exploits channel variations due to channel fading and mutual interferences. –Diversity schemes in Frequency/Time/Spatial Domain Slide 5Channel Diversity March, 2009 time frequency Space f Coherence Bandwidth PHY: Equalizer, OFDM, CDMA, Smart Antenna MAC: ARQ, Channel Diversity, Sector Ant. MAC NW; Path diversity

6. doc.: IEEE 802.15-09-0215-00-004e Submission Description of Channel Diversity Channel Hopping – changing channel according to the predefined orthogonal (channel hopping) sequence. Channel Adaptation – changing channel according to the channel quality measure such as CSI, packet error rate etc. Slide 6Channel Diversity March, 2009

7. doc.: IEEE 802.15-09-0215-00-004e SubmissionSlide 7 Channel Diversity Mitigate Channel Impairments –Channel hopping/channel adaptation add frequency diversity to mitigate the effects of interference and multipath fading If another network (like WiFi) is busy in a band of 802.15.4 channels, retries outside of the band will work The multipath coherence bandwidth ranges from 5 MHz for non- LOS to more than 20 MHz for near-LOS. A transmission on a faded channel can be retransmitted on other channels. Improved coexistance Increase Network Capacity –One timeslot can be used by multiple links at the same time by using different channels Channel resources can be managed either in centralized or decentralized manner. Channel Diversity March, 2009

8. doc.: IEEE 802.15-09-0215-00-004e SubmissionSlide 8 Channel Hopping Proposals for Channel Diversity: –Distributed Channel Hopping (DCH) –Time Slotted Channel Hopping (TSCH) – Enhanced GTS (EGTS) Channel Adaptation 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 802.15.4 Channels Slot n Slot n-1 Slot n-2 Slot n+1 Slot n+2 Channel Diversity March, 2009

9. doc.: IEEE 802.15-09-0215-00-004e Submission DCH: operation Timeslot operation –Idle timeslot : No Tx and Rx –Rx timeslot Tune to its own channel Enable receiver Receive data frame Turn to Tx mode Transmit Ack frame –Tx timeslot Jump to the receiver’s channel Transmit data frame Turn to Rx mode Receive Ack frame 0 2 Channel DiversitySlide 9 March, 2009

10. doc.: IEEE 802.15-09-0215-00-004e Submission DCH: Offset Assignment Empty offset selection - example –node 1’s Neighbor offset bitmap = {1,3,6,10} –node 3’s Neighbor offset bitmap = {1,3,12,13} –node 6’s Neighbor offset bitmap = {1,2,6,9} –node 12’s Neighbor offset bitmap = {3,12} –Available offsets = {0,4,5,7,8,11,14,15} Slide 10Channel Diversity March, 2009

11. doc.: IEEE 802.15-09-0215-00-004e Submission DCH: Timeslot Allocation - sender A B C E D Timeslot Request D’s available timeslot : 1 0 0 1 1 0 0 1 1 1 1 1 Slide 11Channel Diversity March, 2009

12. doc.: IEEE 802.15-09-0215-00-004e Submission DCH: Timeslot Allocation - receiver Timeslot Response A B C E D D’s available timeslot : 1 0 0 1 1 0 0 1 1 1 1 1 E’s available timeslot : 0 1 1 0 0 1 1 1 1 1 1 1 Allocated timeslot : 0 0 0 0 0 0 0 1 1 0 0 0 Channel Diversity Slide 12 March, 2009

13. doc.: IEEE 802.15-09-0215-00-004e SubmissionSlide 13 BABA BCBC BABA CADACADA BEBFBEBF B C TSCH: Link = (Timeslot, Channel Offset) A Time Chan. offset One Slot D The two links from B to A are dedicated D and C share a link for transmitting to A The shared link does not collide with the dedicated links FE Channel Diversity March, 2009

14. doc.: IEEE 802.15-09-0215-00-004e SubmissionSlide 14 B  A (ch 15) BEBFBEBF BCBC BABA CADACADA B  A (ch25) BCBC BABA BEBFBEBF CADACADA B  A (ch18) BCBC BABA CADACADA BEBFBEBF TSCH: Channel Hopping Each link rotates through k available channels over k cycles. –Ch # = Chan Hopping Seq. Table ( ( ASN + Channel Offset) % Number_of_Channels ) Blacklisting can be defined globally and locally. (In Europe a frequency hopping system in the 2.4 GHz band can blacklist only one channel, and adaptive blacklisting is not possible) Time Channel Offset N*4 Cycle N Cycle N+1 Cycle N+2 N*4+1(N+1)*4N*4+2N*4+3 ASN= Channel Diversity March, 2009

15. doc.: IEEE 802.15-09-0215-00-004e Submission First, choose a time slot (or slots), which has at least one vacant channel. –More than one slot can be allocated for each link (Tx & Rx pair). –Don’t assign two channels at the same time slot to a device. See Fig.1 –Considering multi-hop delay (as discussed in the 15-08-0775-01-004e). –Considering time schedule: try to assign time slots next to time slots haven been assigned to themselves. See Fig.2 time slots for A->B and B->C are successive Then, choose a channel that is available in that time slot –Considering adjacent channel interference avoidance –Considering channel switch: try to avoid channel switch. See Fig.2 channel for A->B and B->C is the same A->BB->C CH 1 CH 2 Fig.2 efficient GTS allocation Slots A->B B->C CH n CH m Slots Fig.1 conflicting GTS allocation EGTS(adaptation): Allocation Rule Slide 15Channel Diversity March, 2009

16. doc.: IEEE 802.15-09-0215-00-004e Submission Each node maintains a Neighborhood Allocation Bitmap Table (ABT) Example (MO = SO = 3) ABT size = 14 bytes 0: Vacant, 1: Allocated (self or neighbors) Row: time slot, Column: channel 00000000 01000100 01000100 00000000 00000000 00001000 00000100 00000000 00000000 00000000 01000000 00000000 00000000 Slide 16Channel Diversity EGTS(adaptation): Allocation Bitmap Table (ABT) March, 2009

17. doc.: IEEE 802.15-09-0215-00-004e Submission Entire bitmap may be too big to be transmitted by Beacon or EGTS command frames Example (MO = 7, SO = 3) ABT size = 224 bytes 0: Vacant,1: Allocated. Row: time slot, Column: channel Solution: Send a ABT sub-block (with an index indicating beginning & ending of a block) Example: 28 bytes sub-block. … 00000000 00001000 00000100 00000000 00000000 01000000 00001000 00000000 00000000 01000100 00000100 00000000 00001000 00000100 00000000 00000000 01000000 00000000 10000000 01000000 01000100 00000000 00001000 00000100 00000000 00000000 01000000 10000000 00000000 00000000 10000000 00000000 00000000 … Slide 17Channel Diversity EGTS(adaptation): ABT sub-block March, 2009

18. doc.: IEEE 802.15-09-0215-00-004e Submission Source Requesting destination Three command frames are transmitted during CAP period –EGTS request Unicast from a source to a destination. Providing locally available slots (28 byte ABT sub-block). Required number of slots (depending on data rate). –EGTS reply Broadcast from the destination. Select appropriate slots in the sub-block and announce the assigned EGTS slots to all neighbors (28 byte ABT sub-block). –EGTS notify Broadcast from the source Announce the assigned EGTS slots to all neighbors (28 bytes ABT sub-block) Schedule Update –Those nodes who are reachable by EGTS Rep and EGTS Notify. Beacons do not carry EGTS allocation information –Entire EGTS bitmap may be too big. –Periodically sending EGTS bitmap is energy consuming. Slide 18Channel Diversity EGTS: Three-way-handshake for Allocation March, 2009

19. doc.: IEEE 802.15-09-0215-00-004e Submission 2. EGTS reply, broadcast Payload : Dst addr (3) new allocated ABT sub-block {0000000000000000 0000100000000000 … 0000000000000000 } 1.EGTS request, unicast Payload : Number of slots ABT sub-block {0000000000100000 0000000000000000 … 0000000000000000 } Assuming slot (9,21) is already assigned from node 4 for transmitting frames to node 3 Slot = tuple (time slot, channel) MO = SO Node 1 assigns slot (10,15) for Node 3 Every node that hears the broadcasts updates its allocation bitmap table (ABT) 3. EGTS notify, broadcast Payload : Dst addr (1) new allocated ABT sub-block {0000000000000000 0000100000000000 … 0000000000000000 } Slide 19Channel Diversity EGTS(adaptation): Allocation Example March, 2009

20. doc.: IEEE 802.15-09-0215-00-004e Submission Duplicated allocation can happen Some nodes may miss some of EGTS reply or notify. (Broadcast is not reliable) New joining node requests a slot not knowing the slot allocation state in the area. Send EGTS collision notification during CAP period The existing owner of the slot detects duplicated allocation by hearing neighbor’s EGTS reply or notify. EGTS duplicated allocation notification (Unicast) from the existing owner. Duplicated slot id (time slot, channel). ABT sub-block (28 bytes) around the colliding time slot. Forces the source and the destination nodes to retry three-way-handshake EGTS allocation. Slide 20Channel Diversity EGTS: Duplicated Allocation Notification March, 2009

21. doc.: IEEE 802.15-09-0215-00-004e Submission EGTS Expiration If an allocated EGTS is not used for longer than N beacon intervals, the allocation expires. Each destination device maintains a counter table for EGTS Expiration. EGTS Deallocation Deallocation also uses three-way- handshake (request, reply, notify). Deallocation is performed when a source device finds out EGTS expiration. when a destination device does not need to use EGTS any longer. ABT Table Slide 21Channel Diversity EGTS: Deallocation & Expiration March, 2009

22. doc.: IEEE 802.15-09-0215-00-004e Submission Anticipated Changes to Standard Slide 22Channel Diversity March, 2009

23. doc.: IEEE 802.15-09-0215-00-004e Submission MAC PIB Supporting Channel Hopping DCH: –Channel Hopping Sequence –Channel Offset Value –Beacon Index –Allocation Bitmap Table TSCH: –Default Channel Hopping Sequence –Channel Hopping Sequence Tables Channel DiversitySlide 23 March, 2009

24. doc.: IEEE 802.15-09-0215-00-004e Submission TSCH MAC Primitives Supporting Channel Hopping SET-SLOTFRAME Request parameters – slotframe size – channel page – channel map SET-LINK Request parameters –Timeslot number –Channel offset Channel DiversitySlide 24 March, 2009

25. doc.: IEEE 802.15-09-0215-00-004e Submission A new parameter in a MAC Primitive –MLME-GTS.request (GTSCharacteristics, SecurityLevel, KeyIdMode, KeySource, KeyIndex, EGTSCharacteristics) –MLME-GTS.confirm (GTSCharacteristics, status, EGTSCharacteristics) –MLME-GTS.indication (DeviceAddress, GTSCharacteristics, SecurityLevel, KeyIdMode, KeySource, KeyIndex, EGTSCharacteristics) A new command frame : EGTS Request –Sub-fields: MHR fields, Commands frame identifier, EGTSCharacteristics EGTS MAC Primitives and Commands Supporting Channel Diversity Channel DiversitySlide 25 March, 2009

26. doc.: IEEE 802.15-09-0215-00-004e Submission Backward Compatibility Slide 26Channel Diversity March, 2009

27. doc.: IEEE 802.15-09-0215-00-004e Submission Backward Compatibility Backward Compatibility is provided if the proposed protocol can coexist with legacy protocol. No changes on the existing frame format Only additions that are optional –New frame format, primitives, and PIB attributes Two modes in 15.4-2006: Beacon enabled mode and non-beacon enabled mode Slide 27Channel Diversity March, 2009

28. doc.: IEEE 802.15-09-0215-00-004e Submission nonbeacon-enabled PAN beacon-enabled PAN E-GTS TDMA Contention Access 802.15.4 Contention-Free Factory Automation ISA, HCF ZigBee, 802.15.5 Overhead Reduction/Security Low Energy Channel Diversity Slide 28 March, 2009

29. doc.: IEEE 802.15-09-0215-00-004e Submission Sub-clauses for general description GeneralSub-clausetype Channel diversity5.5.4.x channel diversitynew Slide 29Channel Diversity