Use of More Data Field Date: 2006-01-17 Authors: Jan 2006 Jan 2006 doc.: IEEE 802.11-06/0155r0 Jan 2006 Use of More Data Field Date: 2006-01-17 Authors: 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>. Jon Edney, Jari Jokela, Nokia Jon Edney, Jari Jokela, Nokia

Jan 2006 doc.: IEEE 802.11-06/0155r0 Jan 2006 Abstract This submission describes a modification to the use of the “More Data” field to enable the AP to signal the state of its transmission queue to stations that are not is power-save mode. Jon Edney, Jari Jokela, Nokia Jon Edney, Jari Jokela, Nokia

Review of basic Power Save Operation Jan 2006 Review of basic Power Save Operation The “More Data” bit is used to indicate that the AP has data waiting to be sent to the STA STA gets an indication of waiting data in the “TIM”: part of a beacon sent at DTIM. STA Polls AP for each MPDU AP sends MPDU and sets “More data” bit if there are further MPDUs waiting to be sent STA can keep polling until More Data bit is clear The more data bit is not used unless STA is in power save mode Jon Edney, Jari Jokela, Nokia

Jan 2006 Additions by 802.11e Power save mechanism extended to allow for sending of prioritized traffic from both STA and AP side. Designed to ensure low priority data from AP does not block high priority data from STA More Data bit can be set by QAP in ACK frame responding to data from QSTA Otherwise usage is similar and only appropriate to stations in power save mode. Jon Edney, Jari Jokela, Nokia

Jan 2006 New Proposal To use “More Data” bit also with STAs that are not in PS mode to indicate that data is ready to be delivered Purpose: To enable stations to delay the start of a transition until all pending data is delivered Jon Edney, Jari Jokela, Nokia

Benefit Analysis We considered two types of traffic: Jan 2006 Benefit Analysis We considered two types of traffic: Regular datagram type traffic (e.g. UDP) Streaming data with window acknowledge (e.g. TCP) Voice traffic might can use UDP to deliver a stream of packets at regular intervals File transfer or Web page access uses TCP to allow efficient bulk transfer of data Jon Edney, Jari Jokela, Nokia

Model for analysis Jan 2006 Packet Source Buffered Network Switch Local Switch AP1 AP2 STA Jon Edney, Jari Jokela, Nokia

Case 1: Constant Packet Rate (Datagram) Jan 2006 Case 1: Constant Packet Rate (Datagram) Packet Source Buffered Network Switch Low aggregate utilization Low buffer requirement in network or AP Unlikely the “More Data” bit will be set Local Switch AP1 AP2 STA Jon Edney, Jari Jokela, Nokia

Case 2: Streaming in busy network Jan 2006 Case 2: Streaming in busy network Packet Source Buffered Network Switch Source sends “TCP window” worth of data Due to network congestion or rate limitation TCP window is buffered in network Packet Source generates TCP window of data Packets are buffered in network router due to congestion Packets are released at fairly constant rate “More Data” Bit unlikely to be set Local Switch AP1 AP2 STA Jon Edney, Jari Jokela, Nokia

Case 3: Streaming in hi-capacity network Jan 2006 Case 3: Streaming in hi-capacity network Packet Source Buffered Network Switch Source sends “TCP window” worth of data Packet Source generates TCP window of data Packets pass quickly to AP - AP buffers the window Packets are released at fairly constant rate “More Data” Bit likely to be set Problem is that packets will always be queue until file transfer is completed. Might be better to transition now and wait for resend of entire window to AP2 Local Switch AP1 AP2 STA Jon Edney, Jari Jokela, Nokia

Jan 2006 Initial Conclusion For station operating in power active mode the use of “More Data” has some value: For regular (e.g. VoIP) traffic frames will not queue at AP For Streaming in busy network, frames queue in network - not AP For Streaming is fast network frames will queue in AP - but More Data bit will not clear until completion of TCP transfer However.... we need to consider case where STAs use power save Jon Edney, Jari Jokela, Nokia

Consequences of PS Mode Jan 2006 Consequences of PS Mode In power save mode STA might only wake-up every DTIM to receive beacons and check for data In case 1, STA is unlikely to be in PS mode because each datagram must be processed in timely manner In case 3, STA is unlikely to be in PS mode because data is constantly arriving In case 2 STA wants to go to PS mode after emptying buffer. Several packets may accumulate before STA activates again Jon Edney, Jari Jokela, Nokia

Case 3: Streaming in hi-capacity network Jan 2006 Case 3: Streaming in hi-capacity network Packet Source Buffered Network Switch Source sends “TCP window” worth of data Packet Source generates TCP window of data Packets pass quickly to AP - AP buffers the window Packets are released at fairly constant rate Frames are queued at AP1 because STA is sleeping STA switched to active mode to receive packets and prepare for transition STA wants to know when queued frames are delivered. More Data bit can inform the STA of the best time to transition. Local Switch AP1 AP2 STA Jon Edney, Jari Jokela, Nokia

Jan 2006 Conclusion Use of More Data bit of significant value to stations preparing to transition when power save mode is in operation. Jon Edney, Jari Jokela, Nokia

Key points of Normative Text Jan 2006 Key points of Normative Text Use of More Data bit only applies to Fast BSS STAs that are not in powersave mode. Setting of More Data bit by Fast BSS AP is optional (at the APs discretion) Use of More Data bit information by STA is not defined (although it is suggested it be used in the decision of when to transition) Jon Edney, Jari Jokela, Nokia

Jan 2006 Motion Move to adopt the text of 11-05-1091-00-000r-use-more-data-bit.doc into the TGr Draft Jon Edney, Jari Jokela, Nokia

References 11-05-0151-00-000r-new-twist-more-data-bit.ppt Jan 2006 References 11-05-0151-00-000r-new-twist-more-data-bit.ppt 11-05-1091-00-000r-use-more-data-bit.doc Jon Edney, Jari Jokela, Nokia