Wifi power saving mode - Revision history

imported_>joerg_rw: fixed dangling link - lart pipermail!

2013-10-20T07:02:47Z

fixed dangling link - lart pipermail!

← Older revision		Revision as of 07:02, 20 October 2013
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	The tablets support what is called Wifi Power Saving Mode (PSM). PSM allows the tablet to switch its wifi radio on and off several times a second to save battery. While this does greatly improve battery life (6-8 hours idle on Wifi without PSM, 3-4 days with), there are still many routers on the market which do not support PSM or have a buggy implementation and this can cause problems for the tablets.		The tablets support what is called Wifi Power Saving Mode (PSM). PSM allows the tablet to switch its wifi radio on and off several times a second to save battery. While this does greatly improve battery life (6-8 hours idle on Wifi without PSM, 3-4 days with), there are still many routers on the market which do not support PSM or have a buggy implementation and this can cause problems for the tablets.

	Because using PSM introduces extra latency for incoming packets, the tablets try to optimize performance by remaining in Constant Active Mode (CAM) if there is constant traffic. On the other hand, CAM consumes a lot of power, so the timeout should be as short as possible. For more detailed description, see [http://lists.maemo.org/pipermail/maemo-users/2008-July/~~034755~~.html this posting on the subject].		Because using PSM introduces extra latency for incoming packets, the tablets try to optimize performance by remaining in Constant Active Mode (CAM) if there is constant traffic. On the other hand, CAM consumes a lot of power, so the timeout should be as short as possible. For more detailed description, see [http://lists.maemo.org/pipermail/maemo-users/2008-July/011430.html this posting on the subject].

	== How it works ==		== How it works ==

imported_>joerg_rw: /* Ad-hoc prevents PSM */ further correcting my own former nonsense

2013-10-20T06:55:21Z

Ad-hoc prevents PSM: further correcting my own former nonsense

← Older revision		Revision as of 06:55, 20 October 2013
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	PSM can be configured on a per-connection basis in the Connectivity control panel (Application menu -> Settings -> Control panel -> Connectivity). Under the Other tab of Advanced settings when editing a saved connection. There are 3 options available: On (Maximum), On (Intermediate), and Off (note, the WLAN transmission power setting will not significantly impact battery life—though it will impact Wifi roaming distance—and is simply there for legislative reasons). Maximum and Intermediate change the timeout period (200ms and 1000ms, respectively), and Off turns off PSM entirely.		PSM can be configured on a per-connection basis in the Connectivity control panel (Application menu -> Settings -> Control panel -> Connectivity). Under the Other tab of Advanced settings when editing a saved connection. There are 3 options available: On (Maximum), On (Intermediate), and Off (note, the WLAN transmission power setting will not significantly impact battery life—though it will impact Wifi roaming distance—and is simply there for legislative reasons). Maximum and Intermediate change the timeout period (200ms and 1000ms, respectively), and Off turns off PSM entirely.

	== ~~<s>~~Ad-hoc prevents PSM~~</s>~~ ==		== Ad-hoc prevents PSM ==

	~~<s>~~Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes.</s> (This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm]) \|\| Anyway any master would need to send beacons every few fractions of a second, something that largely defeats the purpose of powersaving. Otherwise the time sync between the two peers gets lost rather quickly which basically means the connection gets lost or huge delay gets introduced.		Ad-hoc mode cannot use power-saving modes other than reduce transmit power <s>- since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes.</s> (This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm])

			Smart Environments: Technology, Protocols and Applications
			books.google.de
			Diane Cook, Sajal Das - ‎2004 - 404 pages
			Power Management in Infrastructure-less WLANS In an IBSS, power management is a fully distributed process managed by the individual mobile stations. The station that initializes the IBSS defines the beacon interval. At the beginning of the ...

			Anyway any master would need to send beacons every few fractions of a second, something that largely defeats the purpose of powersaving. Otherwise the time sync between the two peers gets lost rather quickly which basically means the connection gets lost or huge delay gets introduced. As far as I understand. Fact is N900 eats tons of power in ad hoc hotspot mode.

	http://en.wikipedia.org/wiki/IEEE_802.11		http://en.wikipedia.org/wiki/IEEE_802.11

imported_>joerg_rw: /* Ad-hoc prevents PSM */ 802.11 wiki

2013-10-20T06:40:05Z

Ad-hoc prevents PSM: 802.11 wiki

← Older revision		Revision as of 06:40, 20 October 2013
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	<s>Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes.</s> (This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm]) \|\| Anyway any master would need to send beacons every few fractions of a second, something that largely defeats the purpose of powersaving. Otherwise the time sync between the two peers gets lost rather quickly which basically means the connection gets lost or huge delay gets introduced.		<s>Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes.</s> (This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm]) \|\| Anyway any master would need to send beacons every few fractions of a second, something that largely defeats the purpose of powersaving. Otherwise the time sync between the two peers gets lost rather quickly which basically means the connection gets lost or huge delay gets introduced.

			http://en.wikipedia.org/wiki/IEEE_802.11
			* Power Management: This bit indicates the power management state of the sender after the completion of a frame exchange. Access points are required to manage the connection and will never set the power saver bit.
			* More Data: The More Data bit is used to buffer frames received in a distributed system. The access point uses this bit to facilitate stations in power saver mode. It indicates that at least one frame is available and addresses all stations connected.

	== Routers known to be incompatible with PSM mode ==		== Routers known to be incompatible with PSM mode ==

imported_>joerg_rw: /* how it works */

2013-10-20T06:22:44Z

how it works

← Older revision		Revision as of 06:22, 20 October 2013
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	Because using PSM introduces extra latency for incoming packets, the tablets try to optimize performance by remaining in Constant Active Mode (CAM) if there is constant traffic. On the other hand, CAM consumes a lot of power, so the timeout should be as short as possible. For more detailed description, see [http://lists.maemo.org/pipermail/maemo-users/2008-July/034755.html this posting on the subject].		Because using PSM introduces extra latency for incoming packets, the tablets try to optimize performance by remaining in Constant Active Mode (CAM) if there is constant traffic. On the other hand, CAM consumes a lot of power, so the timeout should be as short as possible. For more detailed description, see [http://lists.maemo.org/pipermail/maemo-users/2008-July/034755.html this posting on the subject].

			== How it works ==
			E.G. http://features.techworld.com/mobile-wireless/4103/a-guide-to-wi-fi-power-save-technologies/ explains:

			'''Power Save Mode (PSM).''' This is the original power-conservation technique defined in 802.11, and was tested in this article. The methodology is for the mobile device to suspend radio activity after a variable but pre-determined (by the vendor) period of inactivity, and then wake up periodically (usually about three ''beacon frames'', which are normally 100 ms each) to see if the infrastructure has queued any traffic for it.
			Some AccessPoints allow to configure beacon rate and the number of beacons to pass by before the client wakes up again (a parameter that gets negotiated between AP and client)

	== Issues ==		== Issues ==

imported_>joerg_rw: /* Ad-hoc prevents PSM */ comment on comment on PSM in adhoc mode

2013-10-20T06:12:21Z

Ad-hoc prevents PSM: comment on comment on PSM in adhoc mode

← Older revision		Revision as of 06:12, 20 October 2013
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	== <s>Ad-hoc prevents PSM</s> ==		== <s>Ad-hoc prevents PSM</s> ==

	<s>Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes.</s> (This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm])		<s>Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes.</s> (This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm]) \|\| Anyway any master would need to send beacons every few fractions of a second, something that largely defeats the purpose of powersaving. Otherwise the time sync between the two peers gets lost rather quickly which basically means the connection gets lost or huge delay gets introduced.

	== Routers known to be incompatible with PSM mode ==		== Routers known to be incompatible with PSM mode ==

imported_>joerg_rw: /* Ad-hoc prevents PSM */

2011-08-16T18:29:34Z

Ad-hoc prevents PSM

← Older revision		Revision as of 18:29, 16 August 2011
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	PSM can be configured on a per-connection basis in the Connectivity control panel (Application menu -> Settings -> Control panel -> Connectivity). Under the Other tab of Advanced settings when editing a saved connection. There are 3 options available: On (Maximum), On (Intermediate), and Off (note, the WLAN transmission power setting will not significantly impact battery life—though it will impact Wifi roaming distance—and is simply there for legislative reasons). Maximum and Intermediate change the timeout period (200ms and 1000ms, respectively), and Off turns off PSM entirely.		PSM can be configured on a per-connection basis in the Connectivity control panel (Application menu -> Settings -> Control panel -> Connectivity). Under the Other tab of Advanced settings when editing a saved connection. There are 3 options available: On (Maximum), On (Intermediate), and Off (note, the WLAN transmission power setting will not significantly impact battery life—though it will impact Wifi roaming distance—and is simply there for legislative reasons). Maximum and Intermediate change the timeout period (200ms and 1000ms, respectively), and Off turns off PSM entirely.

	== Ad-hoc prevents PSM ==		== <s>Ad-hoc prevents PSM</s> ==

	Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes. (This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm])		<s>Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes.</s> (This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm])

	== Routers known to be incompatible with PSM mode ==		== Routers known to be incompatible with PSM mode ==

imported_>amigadave: /* Ad-hoc prevents PSM */ fix link

2010-08-02T09:26:45Z

Ad-hoc prevents PSM: fix link

← Older revision		Revision as of 09:26, 2 August 2010
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	== Ad-hoc prevents PSM ==		== Ad-hoc prevents PSM ==

	Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes. [This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm]]		Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes. (This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm])

	== Routers known to be incompatible with PSM mode ==		== Routers known to be incompatible with PSM mode ==

imported_>mtrower2: /* Ad-hoc prevents PSM */

2010-07-26T07:17:54Z

Ad-hoc prevents PSM

← Older revision		Revision as of 07:17, 26 July 2010
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	== Ad-hoc prevents PSM ==		== Ad-hoc prevents PSM ==

	Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes.		Ad-hoc mode cannot use power-saving modes other than reduce transmit power - since there's no master or slave where the slave can spend a lot of time "asleep", it prevents power saving modes. [This is false and needs fixed. The stations trade off acting as "master". [http://books.google.com/books?id=9rHnRzzMHLIC&pg=PA193&lpg=PA193&dq=ibss+power+management&source=bl&ots=3wzOD62aBr&sig=lUehrHBabk4WX8NT6_XEyIjxy5Y&hl=en&ei=9zVNTOjWD4z4sAPg2PhI&sa=X&oi=book_result&ct=result&resnum=7&ved=0CC0Q6AEwBg#v=onepage&q=ibss%20power%20management&f=false 802.11 ibss psm]]

	== Routers known to be incompatible with PSM mode ==		== Routers known to be incompatible with PSM mode ==

91.153.237.37: /* Routers known to be incompatible with PSM mode */

2010-07-18T06:33:51Z

Routers known to be incompatible with PSM mode

← Older revision		Revision as of 06:33, 18 July 2010
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	== Routers known to be incompatible with PSM mode ==		== Routers known to be incompatible with PSM mode ==

	* ~~Fon2200~~		* La Fonera (FON2100, FON2200)
	* French ISP Free.fr Freebox ([https://bugs.maemo.org/show_bug.cgi?id=3481 Maemo #3481] and [http://bugs.freeplayer.org/task/2538 Free #2538])		* French ISP Free.fr Freebox ([https://bugs.maemo.org/show_bug.cgi?id=3481 Maemo #3481] and [http://bugs.freeplayer.org/task/2538 Free #2538])

imported_>corsac: add freebox to incompatible access point

2009-12-03T12:15:18Z

add freebox to incompatible access point

← Older revision		Revision as of 12:15, 3 December 2009
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	* Fon2200		* Fon2200
			* French ISP Free.fr Freebox ([https://bugs.maemo.org/show_bug.cgi?id=3481 Maemo #3481] and [http://bugs.freeplayer.org/task/2538 Free #2538])

	[[Category:Connectivity]]		[[Category:Connectivity]]
	[[Category:WiFi]]		[[Category:WiFi]]
	[[Category:Power users]]		[[Category:Power users]]