1. doc.: IEEE 802.11-12/0102r2 SubmissionLiwen Chu Etc.Slide 1 TGah Power Saving Date: 2012-01-16 Authors: Date: Jan, 2012

2. doc.: IEEE 802.11-12/0102r2 Submission TGv Power Save Features BSS Max idle period management enables an AP to indicate a time period during which the AP does not disassociate a STA due to non-receipt of frames from the STA. WNM-Sleep mode enables a non-AP STA to signal to an AP that it will be sleeping for a specified length of time, defined as the number of DTIM intervals. Flexible Multicast Service (FMS) enables a non-AP STA to wake up at the alternate DTIM interval, rather than every DTIM, and enables significant power saving when a non-AP STA receives group addressed traffic. Direct Multicast Service (DMS) enables a non-AP STA to request the AP to transmit group addressed frames destined to the requesting STA as individually addressed frames. Proxy ARP capability enables an AP to indicate that the non-AP STA will not receive ARP frames and remain in power-save for longer periods of time. Slide 2 Date: Jan, 2012

3. doc.: IEEE 802.11-12/0102r2 Submission Why WNM-Sleep is not Good for TGah Almost all STAs in a Smart Grid BSS have the same power save requirement (e.g. long sleep period), but WNM-Sleep is suitable for a small number of STAs in a BSS. If WNM-Sleep is used for such STAs, beacon intervals other than DTIM beacon intervals are rarely used. With WNM-Sleep, TIM in Beacon may be as big as 6000/8 = 750bytes (e.g. when AID1 and AID5998 have the same awake DTIM and buffered frames at the awake DTIM). –It is difficult for an AP to group STAs with nearby AID to wake up at the same TBTT (e.g. AID 101 to AID 200). The same usage of the STAs in a Smart Grid BSS means the same wake up intervals of the STAs. A beacon interval can not finish polling all 6000 STAs in one 100ms beacon interval given the lower PHY rate of a Smart Grid BSS (~hundreds kbps): – (100bytes MPDU + 14bytes ACK) * 8 /200000= 4.56ms. –Actually transmission time is longer since Backoff, PS Poll, PHY overhead and IFS are needed. DTIM TIM STA with AID1 (STA1) negotiates WNM-Sleep with 2 DTIM intervals. STA with AID5998 (STA5998) negotiates WNM-Sleep with 2 DTIM intervals. STA1 wakes up.STA1 and STA5998 wake up. Slide 3 Date: Jan, 2012

4. doc.: IEEE 802.11-12/0102r2 Submission TGah Sleep Mode The AP allocates its associated STAs to different groups and matches each group’s TIM to its awake TBTT. –Option 1: nearby AIDs being allocated in a group. AID and enhanced TIM IE (2 bytes Bitmap Control with longer Bitmap Offset) can be used. –Option 2: similar power save requirement (or nearby position) being allocated in a group. Group member ID need to be defined and Enhanced Group TIM IE indicates group member’s buffered frame indication per member’s group ID. The AP notifies the TBTT and sleep interval of each group. Long sleep interval is supported through grouping of STAs. –Each group has a different awake TBTT. Group1 Group2 Group3 Group4 Group5 Group6 Group7 Group8 Group1Group3Group5 Group2Group4Group6 Sleep Interval Slide 4 Date: Jan, 2012

5. doc.: IEEE 802.11-12/0102r2 Submission Option 1: Nearby AIDs in a group Enhanced TIM element extends Bitmap Control field to 2 bytes if TIM IEs from multiple group can be included in a beacon. –Bit 0 of the field contains the Traffic Indicator bit associated with Association ID 0, In an AP with multiple BSSID, more bits are required for group frames indication. –The remaining bits of the field form Bitmap Offset of AID. Element ID LengthDTIM Count DTIM Period Bitmap ControlPartial Virtual Bitmap Octets: 111121--251 One octet Bitmap Control field can be used if TIM IEs from only one Group can be included in a Beacon. Partial Virtual Bitmap include relative AID (each bit related to AID-lowest AID in the group). Slide 5 Date: Jan, 2012 001001000……100110000Group5 AID bitmap: AID 2048 AID 2175 Relative AID 0 Relative AID 127 A STA needs to know the group that it belongs, the Group Sleep Interval in beacon intervals, wake up TBTT through management frames. Extended TIM

6. doc.: IEEE 802.11-12/0102r2 Submission Option 2: Similar power save requirement (nearby position) in a group Group TIM element extends Bitmap Control field to 2 bytes if TIM IE from multiple group can be included in a beacon. –Bit 0 of the field contains the Traffic Indicator bit associated with Association ID 0, In an AP with multiple BSSID, more bits are required for group frames indication –The remaining bits of the field form the group indication and Bitmap Offset of group member id. Element ID LengthDTIM Count DTIM Period Bitmap ControlPartial Virtual Group Bitmap Octets: 111121--251 One octet Bitmap Control field can be used if TIM IEs from only one Group can be included in a Beacon. Group ID is identified by TBTT. A STA needs to know the group that it belongs, group member ID, the Group Sleep Interval in beacon intervals, wake up TBTT through management frames. 000001000100100100110000Group5 AID bitmap: AID 5 has member ID 1, AID 9 has member ID 2, AID 13 has member ID 3………. Slide 6 Date: Jan, 2012 AID 5 AID 13 AID 9 Extended TIM

7. doc.: IEEE 802.11-12/0102r2 Submission Conclusion Extended TIM allows TIM IEs from multiple group to be included in a beacon. –Extended TIM is robust. One-byte Bitmap Control can be used when TIM IE(s) from only one group can be included in a beacon. –Partial Virtual Bitmap needs to be redefined. Slide 7 Date: Jan, 2012

8. doc.: IEEE 802.11-12/0102r2 Submission Straw Poll 1 Do you think that TIM IEs from only one Group can be included in a Beacon? –Y –N –A Slide 8 Date: Jan, 2012

9. doc.: IEEE 802.11-12/0102r2 Submission Straw Poll 2 Do you support 2-byte Bitmap Control? –Y –N –A Slide 9 Date: Jan, 2012