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:Low Energy Subgroup Report Date Submitted: 11 March, 2009 Source: Wei Hong, Company: Arch Rock Corporation Address: 501 2nd Street, Suite 410, San Francisco, CA 94707, USA Voice: 415-692-0828, FAX: 415-278-0441, E-Mail: whong@archrock.com Re:Final Proposal for 802.15.4e Abstract:Proposal review and subgroup status update. Purpose:Subgroup update for 802.15.4e 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. Wei Hong, Arch Rock Corporation

2. Low Energy Subgroup Report Wei Hong Arch Rock Corp. Wei Hong, Arch Rock Corporation

3. FactoryAutomation ISA, HCF Contention-Free Contention-Free TDMA E-GTS ZigBee, 802.15.5 Contention Access Contention Access Low Energy CAP Low Energy Discovery Low Energy CSMA nonbeacon-enabled PAN beacon-enabled PAN Overhead Reduction/Security Low Energy Channel Diversity 802.15.4 <Pat Kinney>, <Kinney Consulting LLC>

4. Subgroup Members • Mike McInnis (Boeing) • Rene Struik (Certicom) • Ben Rolfe (Blind Creek) • Betty Zhao (Hua Wei) • Liang Li (Vinno, Chinese WPAN) • Corné van Puijenbroek (Nanotron) • Barbara Staehle (UniWuerzburg) • Kris Pister (UC Berkeley, Dust Networks) • David Culler (UC Berkeley, Arch Rock) • Jonathan Hui (Arch Rock) • ETGS Wei Hong, Arch Rock Corporation

5. Key Extensions To 802.15.4 • Low-energy(LE) FFD-FFD communication • LE FFD – LE RFD communication • Secure ACK with integrity • Multi-channel communication • Responsive, low-power operation Wei Hong, Arch Rock Corporation

6. Guiding Principles • Permit migration path from current hardware • MUST be possible to operate in low power in entire network lifecycle • associate, discovery, join, recovery, etc. • Facilitate efficient upper-layer protocols • including IP and other industrial protocols • Routing and local connectivity • Able to operate without central control • Simple baseline implementations Wei Hong, Arch Rock Corporation

7. Key To Low-energy Mesh • Low energy: < 1% duty cycle, multi-year battery life • Minimize idle listening Ptotal = Plisten + Prx + Ptx • Low-energy RFD • turn off radio when not transmitting • Low-energy FFD • How to duty-cycle the radio while forwarding traffic from other FFDs and RFDs? Wei Hong, Arch Rock Corporation

8. Basic Sampled Listening • Sampled Listening • DARPA Packet Radio 1987 • Aloha-PS, B-MAC, X-MAC, etc. wakeup signal data frame sender t channel sample reception receiver t Wei Hong, Arch Rock Corporation

9. Advantages of Sampled Listening • Always-on illusion • Good for IP • Good for manageability • Good for asynchronous, event-driven communication • Good for mobility and discovery • Shifting overhead to transmissions • Good tradeoff for infrequent communication • Simplicity • Stateless: no prior synchronization of time and state required • No routing required • Other low-energy techniques can be layered on top Wei Hong, Arch Rock Corporation

10. Coordinated Sampled Listening (CSL) Over 802.15.4 • Wakeup signal • Back-to-back 15.4 frame (wakeup frame) • Introduce a new frame type in 15.4e • Can be a data frame for backward compatibility • CSMA only at the beginning of wakeup sequence • Channel sampling • Staged-wakeup of receiver based on RSSI threshold and SFD detection • Receive wakeup frame • Abort if DST is for someone else, otherwise • Turn off receiver until rendezvous time (RZTime) then receive data frame optional 2 4 1 1 2 1 2 2 2 1 Preamble SFD Len FCF DSN DSTPAN DST RZTime Chan CRC Wei Hong, Arch Rock Corporation

11. Key Properties of Basic CSL • Overhearing cost ≤ cost of receiving 1 wakeup frame • Receive cost ≤ cost of receiving 1 wakeup+ 1 data • Wakeup frame sequence is not needed for sending to a non-duty cycled FFD • Wakeup frame sequence is not needed once synchronized with receiver’s channel sample schedule Wei Hong, Arch Rock Corporation

12. How to Broadcast • Always send wakeup frame sequence • Set DST in wakeup frames to FF Wei Hong, Arch Rock Corporation

13. Secure and Robust Acknowledgement(to be incorporated with Overhead Reduction/Security Proposal) • Problems in current 15.4 ACK frame • Lack of addressing information  false positives • Lack of security  vulnerability to link-layer attacks • Lack of payload  difficulty to piggyback neighbor info • New ACK frame • Same as data frame except frame type is ACK • Addressing + DSN to eliminate ambiguity • Same security modes as data frame • Payload for piggybacking schedule information • Relax ACK timing requirement 4 1 1 2 1 variable variable variable variable 2 Preamble SFD Len FCF DSN Addressing Security Header Payload MIC CRC Wei Hong, Arch Rock Corporation

14. Local Scheduling • Include channel sampling phase and period in ACK payload • Sender wait to transmit right before receiver’s next channel sampling time scheduled unscheduled sender t receiver t Wei Hong, Arch Rock Corporation

15. Local Scheduling (cont) • Short wakeup frame sequencebefore transmission to guard against synchronization error • Worst case bounded by channel sample interval • Schedule information as a hint, not required • Each node determines its own schedule • Each node decides which neighbors’ schedules to track • Global synchronization manager not required although can be incorporated Wei Hong, Arch Rock Corporation

16. Streaming over Sampled Listening • Set Frame Pending bit in 15.4 header when communicating multiple frames back-to-back to the same destinations • Receiver keeps listening when Frame Pending bit is set • Sender only send wakeup sequenceat the beginning of stream • Better throughput and efficiency framestream sender t receiver t Wei Hong, Arch Rock Corporation

17. Multi-channel Operation 11 March, 2009 • Generalize single-channel operation • Wakeupframe optionally contains channel for data frame • ACK optionally contains channel information with schedule • Simple extension, but maintains all design principles • Purely local interactions • No added overhead in the common case • Allow communication when no information is known • Robust, low-latency • Low-energy join and discovery 2 2 2 Phase Period ChanMask Slide 17 Wei Hong, Arch Rock Corporation

18. Multi-channel Operation (cont) • Spread channel samples across c channels • No increase in cost when receiver schedule is known Transmitter Receiver • Increase transmit cost by c times when nothing is known Transmitter Receiver Wei Hong, Arch Rock Corporation

19. Proposal Summary • WakeupFrame: one new frame type • Secure ACK Frame: extend existing ACK frame • Add Coordinated Sampled Listening (CSL) to 15.4e MAC optional 2 4 1 1 2 1 2 2 2 1 Preamble SFD Len FCF DSN DSTPAN DST RZTime Chan CRC 4 1 1 2 1 variable variable variable 2 6 Preamble SFD Len FCF DSN Addressing Security Header Payload MIC CRC 2 2 2 optional Phase Period ChanMask Wei Hong, Arch Rock Corporation

20. New PIB Attributes 11 March, 2009 Slide 20 Wei Hong, Arch Rock Corporation

21. Low-Energy PAN Maintenance(proposed by Vinno, SIMIT and Huawei) • Node performs active/passive/orphaned channel scan via sampled listening in low duty cycle • Coordinator transmit wakeup frame sequence before each beacon frame • Prepend beacon request command frame with wakeup command sequence to low-energy coordinators Wei Hong, Arch Rock Corporation

22. Answers to Subgroup Questions • Changes to Standard • Backward Compatibility Description • Application Support Levels Wei Hong, Arch Rock Corporation

23. Changes To Standard • 7.2 MAC frame formats • Add Wakeup frame and new ACK frame • 7.4.2 MAC PIB attributes • Add cslSamplePeriod and cslChannelMask • 7.5.2 Starting and maintaining PANs • Add low-energy channel scan option • 7.5.6 Transmission, reception, and Acknowledgement • Add CSL mechanism Wei Hong, Arch Rock Corporation

24. Backward Compatibility Description • cslSamplePeriod defaults to 0 – identical behavior as 15.4 2006 • Sampled Listening when cslSamplePeriod > 0 Wei Hong, Arch Rock Corporation

25. Application Support Levels • Add Low Energy option to all contention-based channel access modes in 15.4 • Can benefit all intended applications in 15.4e • In particular to applications with • Mobility • Unpredictable network load • Dynamic network environment • Low-energy operations in entire network life cycle Wei Hong, Arch Rock Corporation

26. Thanks You • Questions? Wei Hong, Arch Rock Corporation