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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: Locally-scheduled low-power extensions to for supporting scalable WPANs Date Submitted: 29 August, 2008 Source: Wei Hong, Company: Arch Rock Corporation Address: 501 2nd Street, Suite 410, San Francisco, CA 94707, USA Voice: , FAX: , Re: Final Proposal for e Abstract: This talk proposes locally-scheduled low-power extensions to for supporting scalable WPANs. Purpose: Final Proposal for e 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 Wei Hong, Arch Rock Corporation <author>, <company>
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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 Locally-scheduled Low-power Extensions to for Supporting Scalable WPANs Wei Hong, Ph.D. Jonathan Hui, Ph.D. Arch Rock Corp. David Culler, Ph.D. UC Berkeley & Arch Rock Corp. Wei Hong, Arch Rock Corporation <author>, <company>
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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 Key Extensions To Low-power(LP) FFD-FFD communication LP FFD – LP RFD communication Secure ACK with integrity Multi-channel communication Responsive, low-power operation Wei Hong, Arch Rock Corporation <author>, <company>
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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 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 <author>, <company>
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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 Outline Review of low-power techniques Sampled Listening Coordinated Sampled Listening (CSL) Multi-channel operation Proposal Summary Evaluation Conclusion Wei Hong, Arch Rock Corporation <author>, <company>
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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 Key To Low-power Mesh Low power: < 1% duty cycle, multi-year battery life Minimize idle listening Ptotal = Plisten + Prx + Ptx Low-power RFD turn off radio when not transmitting Low-power FFD How to duty-cycle the radio while forwarding traffic from other FFDs and RFDs? Wei Hong, Arch Rock Corporation <author>, <company>
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Review Of Low-power Techniques
<month year> doc.: IEEE <doc#> 8 September, 2008 Review Of Low-power Techniques 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 <author>, <company>
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Review Of Low-power Techniques (cont)
<month year> doc.: IEEE <doc#> 8 September, 2008 Review Of Low-power Techniques (cont) Listen cost Sync overhead Latency Scheduling e.g. S-MAC, T-MAC, TSMP, etc transmission sender t listen slot receiver t Wei Hong, Arch Rock Corporation <author>, <company>
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Review Of Low-power Techniques (cont)
<month year> doc.: IEEE <doc#> 8 September, 2008 Review Of Low-power Techniques (cont) Unpredictable latency Buffer requirements Listen After Send e.g , (for RFD) ack transmission sender t probe reception receiver t Wei Hong, Arch Rock Corporation <author>, <company>
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Advantages of Sampled Listening
<month year> doc.: IEEE <doc#> 8 September, 2008 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-power techniques can be layered on top Wei Hong, Arch Rock Corporation <author>, <company>
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Coordinated Sampled Listening (CSL) Over 802.15.4
<month year> doc.: IEEE <doc#> 8 September, 2008 Coordinated Sampled Listening (CSL) Over Wakeup signal Back-to-back 15.4 packets (chirp packets) Introduce a new frame type in 15.4e Can be a data frame for backward compatibility CSMA only at the beginning of chirp sequence Channel sampling Staged-wakeup of receiver based on RSSI threshold and SFD detection Receive chirp packet 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 <author>, <company>
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Key Properties of Basic CSL
<month year> doc.: IEEE <doc#> 8 September, 2008 Key Properties of Basic CSL Overhearing cost ≤ cost of receiving 1 chirp Receive cost ≤ cost of receiving 1 chirp + 1 data RFD does not need to chirp to send to a non-duty cycled FFD Stay tuned for optimizations to reduce sender cost Wei Hong, Arch Rock Corporation <author>, <company>
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Secure and Robust Acknowledgement
<month year> doc.: IEEE <doc#> 8 September, 2008 Secure and Robust Acknowledgement 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 <author>, <company>
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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 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 <author>, <company>
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Local Scheduling (cont)
<month year> doc.: IEEE <doc#> 8 September, 2008 Local Scheduling (cont) Short chirps before 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 <author>, <company>
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Streaming over Sampled Listening
<month year> doc.: IEEE <doc#> 8 September, 2008 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 chirps at the beginning of stream Better throughput and efficiency packet stream sender t receiver t Wei Hong, Arch Rock Corporation <author>, <company>
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Multi-channel Operation
<month year> doc.: IEEE <doc#> 8 September, 2008 Multi-channel Operation Generalize single-channel operation Chirp frame 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-power join and discovery 2 2 2 Phase Period ChanMask Slide 17 Wei Hong, Arch Rock Corporation Page 17 <author>, <company>
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Multi-channel Operation (cont)
<month year> doc.: IEEE <doc#> 8 September, 2008 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 <author>, <company>
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Multi-channel Operation (cont)
<month year> doc.: IEEE <doc#> 8 September, 2008 Multi-channel Operation (cont) Overhead analysis: Listen cost: no change Receive cost: no change Transmit cost: When receiver schedule known: no change When receiver schedule is unknown: c times per channel For node discovery only Relatively rare Slide 19 Wei Hong, Arch Rock Corporation Page 19 <author>, <company>
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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 Proposal Summary Chirp Frame: 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 6 variable 2 Preamble SFD Len FCF DSN Addressing Security Header Payload MIC CRC 2 2 2 optional Phase Period ChanMask Wei Hong, Arch Rock Corporation <author>, <company>
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New PIB Attributes Attribute Identifier Type Range Description Default
<month year> doc.: IEEE <doc#> 8 September, 2008 New PIB Attributes Attribute Identifier Type Range Description Default samplePeriod Integer 0-1023 Sampled listening period in ms. 0 means always listening. samplePhase Time to next sample from now in ms. channelMask 16-bit Bitmask for the channels to be used. Channel 25 Slide 21 Wei Hong, Arch Rock Corporation Page 21 <author>, <company>
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Evaluation: Link Layer Primitive Profiles
<month year> doc.: IEEE <doc#> 8 September, 2008 Evaluation: Link Layer Primitive Profiles Overhear Receive (26 bytes) Receive (127 bytes) Channel Sample Transmit (26 bytes) Transmit (127 bytes) Preamble + Transmit (64 ms) Preamble + Transmit (128 ms) Wei Hong, Arch Rock Corporation <author>, <company>
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Evaluation: Link Power Model
<month year> doc.: IEEE <doc#> 8 September, 2008 Evaluation: Link Power Model Wei Hong, Arch Rock Corporation <author>, <company>
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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 Conclusion Proposal to 15.4e New chirp frame Secure ACK frame Add Coordinated Sampled Listening (CSL) to MAC Advantages Low-power operation for entire network lifecycle for both FFD and RFD Always-on illusion, IP-friendly Responsive to asynchronous, unscheduled events Simple to implement Independent of central control Safety net for further optimizations Wei Hong, Arch Rock Corporation <author>, <company>
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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> 8 September, 2008 Thanks You Questions? Wei Hong, Arch Rock Corporation <author>, <company>
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