New Twist on More Data Bit March 2005 doc.: IEEE 802.11-05/0151r0 March 2005 New Twist on More Data Bit Date: 2005-03-07 Authors: Name Organization E-Mail Jon Edney Nokia email@jon.edney.name Jari Jokela Notice: This document has been prepared to assist IEEE 802.11. 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 grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.11. Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures <http:// ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair <stuart.kerry@philips.com> as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.11 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at <patcom@ieee.org>. Edney, Jokela - Nokia Edney, Jokela - Nokia

March 2005 doc.: IEEE 802.11-05/0151r0 March 2005 Abstract This submission presents a proposal to use the “More Data Bit” in MPDUs sent to active stations to give a hint about the status of queues in the sending AP and avoid lost frames on transition. Edney, Jokela - Nokia Edney, Jokela - Nokia

Loss of packets during transition March 2005 Loss of packets during transition It has been noted (doc 05/1646) that packets might be lost during a transition Proposals have been made for schemes to avoid / prevent losses Such schemes benefit from better knowledge of AP queue state This submission proposes a simple method to communicate queue state This can be used by itself to avoid, but not eliminate, packet loss Edney, Jokela - Nokia

March 2005 Causes of lost packets Packets are queued at the old access point but STA transitions away without waiting for delivery Packets arrive over the DS after the STA has transitioned from the old AP but before the DS has been updated to route packets to the new AP New frames go to wrong AP DS not yet updated HUB AP1 AP2 STA has associated STA Edney, Jokela - Nokia

Reducing losses due to queued frames March 2005 Reducing losses due to queued frames If STA knows that Old AP has frames queued for delivery it can delay transition until frames are delivered Therefore we need a way for AP to notify STA that is has queued frames Mechanism already exists to do this in power save mode: the “More Data” bit Propose to allow use of More Data Bit during active mode for TGr STAs Edney, Jokela - Nokia

Use of More Data Bit in base standard March 2005 Use of More Data Bit in base standard When responding to PSPoll from STA in power save mode, AP sets More Data Bit if it has more frames queued for transmission to the STA. AP sets More Data Bit in transmissions to both active and power save STAs during DTIM (broadcasts) STA may set More Data Bit when responding to CF_Poll in contention free period. Edney, Jokela - Nokia

Use of More Data Bit in Draft 802.11e March 2005 Use of More Data Bit in Draft 802.11e Operation of More Data Bit is extended for use with APSD power save mode QAP can also signal to STA the there are queued frames in response to a frame sent from the STA by setting More Data Bit in ACK frames Edney, Jokela - Nokia

Proposed extension (1) AP Behaviour (2) STA Behaviour March 2005 Proposed extension (1) AP Behaviour When sending to a STA that supports TGr extensions…. the AP may set the More Data Bit in any directed MPDU transmission…. if the AP has any data frames queued for transmission to the STA (2) STA Behaviour While in active mode…. a TGr capable may read the More Data Bit on directed frames and use the information as part of a decision when to transition…. but is not required to do so. Edney, Jokela - Nokia

Conclusion A small addition with a useful benefit March 2005 Conclusion A small addition with a useful benefit Presented for discussion If there is interest we will bring normative text after first draft of TGr has been created. Edney, Jokela - Nokia

References 11-05-1646-00-000r-no-packet-left-behind.ppt March 2005 Edney, Jokela - Nokia