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: IEEE802.15.3: Modified Power Save GTS Date Submitted: 13 March, 2002 Source: Dr. William Shvodian Company: XtremeSpectrum, Inc. Address: 8133 Leesburg Pike, Suite 700, Vienna, VA 22182 Voice: 703-269-3047 , FAX: 703-269-3092 , E-Mail: bshvodian@REMOVETHISxtremespectrum.com Re: [ ] Abstract: Proposal for Unified Power Save Purpose: To provide a unified, simplified power save proposal 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 Dr. William Shvodian

2. Overview • Power save requirements • What’s wrong with current Power Save? • Unified Power Save Proposal • Unified Power Save Summary • Conclusion Dr. William Shvodian

3. PS Requirements • Power save is critical for battery powered devices • Power save needs to be as simple as possible • Power save DEVs need to go into and out of a low power mode Dr. William Shvodian

4. Problems with Power Save • We now have two modes: APS and SPS • Sub-rate SPS slots can result in blocking of active streams while only using a fraction of the available bandwidth • SPS Next issue: May always be lagging and is not really needed. • It is unclear why a multiple devices need to have all their GTS in the same sub-rate superframes • Asynchronous power save plus support for sub-rate slots enable simple, effective power save Dr. William Shvodian

5. SPS Slot Blocking • A small number of low rate GTS slots can block all GTS slots for isochronous streams for the piconet CTR Interval = 8 Wake Beacon SPS Slots Dr. William Shvodian

6. SPS with different wake interval • SPS slots could be assigned with a SPS Interval that is less than the CRT Interval • One problem with this is that SPS DEVs need to wake up for beacons that it may not have any GTS slots in. • Another problem with this is that the SPS Interval is determined when the SPS set is created and cannot be changed. The total number of DEVs in the SPS set or the SPS GTS slots will not be known in advance. CTR Interval = 8 SPS Interval Dr. William Shvodian

7. Sub-Rate Slot Spreading • Allowing the PNC to spread out sub-rate GTS slots makes much better use of the available resources! • Power of 2 sub-rates ensure that sub rate slots can be conveniently allocated. CTR Interval = 8 Sub-rate Slots Dr. William Shvodian

8. Next Awake Beacon Issues • “PNC shall keep the next awake beacon for that set updated at all times.” • The PNC doesn’t know in advance when the DEV will receive the frame with the SPS Next value, so the superframe could be passed before the intended DEV receives and processes the command. • Continuous calculation of Next Awake Beacon is a waste of PNC resources. • Given a single superframe number where a power of 2 sub-rate slot is active and knowing the CTR Interval it is trivial for a DEV to calculate the next superframe where that slot will occur. Dr. William Shvodian

9. Replacement of Next Awake Beacon • Add Active Beacon Number and CTR Interval to Channel Time Status command instead of Next Awake Beacon in SPS. Dr. William Shvodian

10. Power Save CTR • Use a single bit to indicate if the Channel time request is a power save request or not. • If the request is a power save request, it shall continue to be allocated when the DEV goes into power save mode. • If it is not a power save request, it shall not be allocated when the DEV goes into power save. Dr. William Shvodian

11. Unified Power Save Summary • Use Sub Rate Slots for power save DEVs so that the PNC can allocate slots without unnecessarily blocking superframe channel time. • Replace the Next Awake Beacon concept with Active Beacon Number and CTR Interval in the Channel Time Status command • Replace SPS with Sub-Rate Slots and Power Save Channel time requests • Require the PNC to send a channel time status command to PS DEVs so they don’t have to process all beacons. Dr. William Shvodian

12. Conclusions • Unified Power Save with Power Save Sub Rate Slots can provide the functionality of SPS without the complexity or the superframe blocking problems. • If SPS has to stay in the standard as is, please make it optional! Let the market decide the need. Dr. William Shvodian