1. Low Energy Subgroup Report
<month year>
doc.: IEEE <doc#>
21 September, 2009
Low Energy Subgroup Report
Wei Hong (Arch Rock Corp.)
Wei Hong, Arch Rock Corporation
<author>, <company>

2. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
21 September, 2009
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: Low Energy Subgroup Report
Date Submitted: 21 September, 2009
Source: Wei Hong
Company: Arch Rock Corporation
Address: 501 2nd Street, Suite 410, San Francisco, CA 94707, USA
Voice: , FAX: ,
Re: Subgroup status report for e
Abstract: Proposal review and subgroup status update.
Purpose: Subgroup update 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>

3. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
21 September, 2009
Status
All required changes are included in combined draft doc 604 rev3 except for
Changes between doc 427 rev5 and rev4
Will communicate with Ludwig to include them
Wei Hong, Arch Rock Corporation
<author>, <company>

4. Major Changes Since SF Meeting
<month year>
doc.: IEEE <doc#>
21 September, 2009
Major Changes Since SF Meeting
Added Receiver Initiated Transmission (RIT) as an alternative low-energy mechanism to Coordinated Sampled Listening (CSL)
Clarified how the upper layer can turn off and on sampled listening to reduce latency for urgent messages
Wei Hong, Arch Rock Corporation
<author>, <company>

5. Coordinated Sampled Listening (CSL) Review
21 September, 2009
Coordinated Sampled Listening (CSL) Review
Receiver periodically performs channel sampling for radio traffic
Every macCSLPeriod (ms)
Sender transmits wakeup frame sequence prior to payload frame
Full wakeup sequence (macCSLMaxPeriod) if unsynchronized with receiver, i.e., first time to send to the receiver
Short wakeup sequence for guard time if synchronized with receiver
Set frame pending bit for streaming traffic

6. Note on Channel Occupancy and Latency
<month year>
doc.: IEEE <doc#>
21 September, 2009
Note on Channel Occupancy and Latency
Channel Occupancy
Unsynchronized transmissions are rare
First time communication between nodes
Broadcast traffic
Synchronized transmissions have minimal channel overhead
Latency
Frame pending bit can be set for low latency streaming
Upper layer has the option to turn off sampled listening temporarily
Setting macCSLPeriod to zero on receiver
Setting macCSLMaxPeriod to zero on the sender
Coordination between sender and receiver
Wei Hong, Arch Rock Corporation
<author>, <company>

7. Receiver Initiated Transmission (RIT) Review
21 September, 2009
Receiver Initiated Transmission (RIT) Review
Receiver periodically broadcasts datareq frames and listen for a short amount of time (macRitDataWaitPeriod) for incoming transmissions every macRitPeriod
Sender waits until receiving datareq frame from receiver then immediately transmit payload frame
Broadcast not directly supported
Simulated by a sequence of unicasts

8. Tradeoff between CSL and RIT
<month year>
doc.: IEEE <doc#>
21 September, 2009
Tradeoff between CSL and RIT
CSL
Channel sample typically takes 0.5ms
Idle listen duty cycle = 0.05% when macCSLPeriod = 1000ms
Achieves low energy with <= 1s per-hop latency
Tradeoff between latency and energy consumption
RIT
Datareq frame transmission typically takes 10ms
Idle listen duty cycle = 0.05% when macRitPeriod = 20s
Works better when higher latency can be tolerated
Works with regulations which limit continuous transmission duration (e.g., Japan)
Wei Hong, Arch Rock Corporation
<author>, <company>

9. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
21 September, 2009
Informative Annex
If link latency needs to be less than a second, use CSL.
If link latency can be greater, consider RIT
Best with 10s of seconds of latency to reduce datareq overhead
If regulation limits continuous transmission duration, use RIT
Wei Hong, Arch Rock Corporation
<author>, <company>

10. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
21 September, 2009
Thanks You
Questions?
Wei Hong, Arch Rock Corporation
<author>, <company>