1. AP Power Down Notification
Month Year
doc.: IEEE yy/xxxxr0
July 2008
AP Power Down Notification
Date:
Authors:
Allan Thomson, Cisco Systems
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
July 2008
Abstract
Enterprise customers want to control when their AP network is active and when it is powered down to save energy costs
This proposal shows a mechanism for the AP network to communicate to clients when one or more APs will be powered down
Allan Thomson, Cisco Systems
John Doe, Some Company

3. July 2008
The problem…
Enterprise customers will schedule shutdown of one or more APs in the network during off-peak hours
Example: Banking institutions with strict working hours do not require active wireless network outside of banking hours
The issue is that STAs are not aware of this shutdown and therefore will continuously scan looking for alternate networks to associate with
At the time of power down it is expected STAs are low mobility devices (i.e. unattended)
Handhelds, Laptops, Desktop, Printers, Copiers
Most devices will be plugged in
Upon shutdown of infrastructure, dual interface STAs may have alternate network connectivity (i.e. enet interface)
Allan Thomson, Cisco Systems

4. July 2008
The solution…
Provide a mechanism for the AP network to notify STAs that one or more APs will be shutdown for an extended period of time
Therefore allowing the STA to choose whether or not to take advantage of this knowledge to save power itself
Allan Thomson, Cisco Systems

5. Use Case #1: Entire Floor Shutdown
July 2008
Use Case #1: Entire Floor Shutdown
Allan Thomson, Cisco Systems

6. Use Case #2: Partial Floor Shutdown
July 2008
Use Case #2: Partial Floor Shutdown
Allan Thomson, Cisco Systems

7. Use Case #3: Exception Handling
July 2008
Use Case #3: Exception Handling
Allan Thomson, Cisco Systems

8. Solution Details Two options to update existing features…
July 2008
Solution Details
Two options to update existing features…
Solution #1: BSS Transition Management
TGv feature
Solution #2: Neighbor Report
TGk feature
Allan Thomson, Cisco Systems

9. Solution #1: Protocol Details
July 2008
Solution #1: Protocol Details
Modify BSS Transition Management Request Frame to indicate power down information
Frame may be sent individually addressed or group addressed
New Power Down Duration field
A 2 octet unsigned integer that represents the number of minutes the APs specified in the candidate list are going to be shutdown for
Field is reserved if value 0
If the candidate list is empty then all APs in the ESS will be shutdown for the duration
A STA may choose to sleep for Power Down Duration
Allan Thomson, Cisco Systems

10. Solution #1: Modified Request Mode
July 2008
Solution #1: Modified Request Mode
Additional bit added to Request Mode field
Power Down bit indicates the STA may take notice of the Power Down Duration field
Allan Thomson, Cisco Systems

11. Solution #1: Power Down Response
July 2008
Solution #1: Power Down Response
STAs may be send a BSS Transition Management Response frame in response to a BSS Transition Management Request frame
Two new status codes
1) Allows a STA to indicate to the AP that it requests the AP remains active
2) Allows a STA to indicate to the AP that it requests a delay in the shutdown by X minutes
STA would provide power down delay parameter in addition to status code
AP policy (beyond scope) may choose to accept or deny STA’s request
New Status code value as indicated
Allan Thomson, Cisco Systems

12. Solution #2: Protocol Details
July 2008
Solution #2: Protocol Details
Neighbor Report Request frame introduced in 11k
Solution #2 will
A) Add Neighbor Report information element to the Neighbor Report Request frame
B) Modify Neighbor Report element to indicate power down information element in the optional sub-element list as part of the Neighbor Report element
C) Define procedures to allow a STA to respond differently to the neighbor request if related to a power down vs non-power-down
i.e. If power down then the STA must respond with the list of neighbors it wants to keep alive
Allan Thomson, Cisco Systems

13. Solution #2: Power Down Sub-Element
July 2008
Solution #2: Power Down Sub-Element
Add optional sub-element to indicate power down information
Sub-element ID: 72
Name: Power Down
A 2 octet unsigned integer that represents the number of minutes the APs specified in the candidate list are going to be shutdown for
If the candidate list is empty then all APs in the ESS will be shutdown for the duration
Allan Thomson, Cisco Systems

14. Solution #2: Power Down Response
July 2008
Solution #2: Power Down Response
Neighbor Report information element return in the Neighbor Report Response frame would include additional sub-element for Power Down Response
Add sub-element to indicate power down response information
Sub-element ID: 73
Name: Power Down Response
A status code field that indicates accept or denied response (similar values to BSS Transition response for power down)
A 2 octet unsigned integer that represents the number of minutes the STA requests the AP remains awake
Allan Thomson, Cisco Systems

15. BSS Transition and Neighbor List Synchronization
July 2008
BSS Transition and Neighbor List Synchronization
As APs shutdown the list of available APs must be synchronized with the neighbor reports AND transition management
Regardless whether Solution #1 or Solution #2 is chosen, both features will be impacted by APs disappearing off the network
If BSS Transition Management is used to communicate active power down, Neighbor lists will be updated once power down is complete
If Neighbor Request/Report frames are used then BSS Transition management will be affected
Allan Thomson, Cisco Systems

16. July 2008
Client Impact #1
Problem – what happens if a client goes to sleep for the period notified but then a user moves the device to a region where a network is active and the user wants to access the network
Solution #A – Add a motion sensor to the device that reactivates the network scanning behavior after motion is detected
Solution #B – Add a user interface that indicates to the user the network has gone to “green-sleep” and prompts them to reactivate upon demand.
Solution #C – Use out-of-band sensor/receiver in handheld to indicate device has entered an area of network that has been shutdown
ALL above are out of scope of proposal
Allan Thomson, Cisco Systems

17. July 2008
Client Impact #2
Problem – what happens in a partial network shutdown where the network (and therefore client) has reduced bandwidth. Does the client have any indication of such an environment?
Solution #1 – APs that remain active could continue to advertise that other parts of the network have shutdown, would inform the client that the network is in partial shutdown
Possible addition to proposal?
Allan Thomson, Cisco Systems

18. July 2008
Questions ?
Allan Thomson, Cisco Systems

19. July 2008
Straw Poll #1
Do you think a normative text proposal on AP Power Notification should be considered for inclusion in TGv?
Yes:
No:
Don’t care:
Allan Thomson, Cisco Systems

20. Straw Poll #2 Which Solution do you prefer? (one vote only)
July 2008
Straw Poll #2
Which Solution do you prefer? (one vote only)
Solution #1: BSS Transition Management
Yes:
Solution #2: Neighbor Report
Both Solution #1 and Solution #2
Other solution
Allan Thomson, Cisco Systems