doc.: IEEE /0015r0 Submission Month YearJanuary 2005 Bryan Wells, DENSO, LA LabsSlide 1 Proposed MAC Enhancements Report Notice: This document has been prepared to assist IEEE 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 Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, 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 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 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at. Date: Authors:

doc.: IEEE /0015r0 Submission Month YearJanuary 2005 Bryan Wells, DENSO, LA LabsSlide 2 Abstract p WAVE-MAC-Supplement- Proposal was presented at the November Plenary meeting. An ad hoc meeting and teleconference was held November 30, 2004 to discuss including the proposed MAC enhancements. The Cancel Transmit Primitive was determined to be useful. The proposal to require the MAC to process only one packet at a time was determined to be unnecessary.

doc.: IEEE /0015r0 Submission Month YearJanuary 2005 Bryan Wells, DENSO, LA LabsSlide p WAVE-MAC-Supplement-Proposal Review MAC Cancel Transmit Primitive –Allows upper layers to withdraw packets submitted to the MAC for transmission, but not yet transmitted. MAC processes only one packet at a time –Allows an upper layer to effectively cancel a lower priority message destined for transmission on the current channel in favor of a higher priority message destined for transmission on the current channel.

doc.: IEEE /0015r0 Submission Month YearJanuary 2005 Bryan Wells, DENSO, LA LabsSlide 4 Operation MAC Cancel Transmit Primitive – Operation Receipt of this message would cause the MAC to abandon its attempt to transmit the current message, and reinitialize its operation in preparation for another transmit request. The withdrawn packet may be re-queued or dropped by the upper layer requesting the cancellation.

doc.: IEEE /0015r0 Submission Month YearJanuary 2005 Bryan Wells, DENSO, LA LabsSlide 5 Use Case 1 MAC Cancel Transmit Primitive – Use Case 1 Ensure packets are not transmitted on the wrong channel p MAC specification does not include channel switching operations (Channelization) between the Control Channel and Service Channels. This will be handled by upper layers. If messages are queued in the MAC for transmission on a Service Channel when the Channelization Manager determines the radio needs to tune to the Control Channel, there is currently no way to remove the pending transmit packets from the MAC queue(s). If not removed from the MAC queue(s) prior to changing channels, these packets may be transmitted on the Control Channel instead of the intended Service Channel, resulting in undesirable and unnecessary Control Channel traffic, and potential delay of high- priority safety messages.

doc.: IEEE /0015r0 Submission Month YearJanuary 2005 Bryan Wells, DENSO, LA LabsSlide 6 Use Case 2 MAC Cancel Transmit Primitive – Use Case 2 Allows multi-channel QoS to be performed above the MAC layer p will specify using e functionality to provide QoS for single channel operation. Upper layers are expected to provide multi-channel QoS for WAVE. –Upper layers can prevent high priority messages destined for transmission on a different channel from being blocked until lower priority messages destined for transmission on the current channel have been transmitted. Avoid having to wait until all messages have been transmitted before changing channels. –For proper synchronization, upper layers must be able to flush the e queue(s) in the MAC prior to changing channels.

doc.: IEEE /0015r0 Submission Month YearJanuary 2005 Bryan Wells, DENSO, LA LabsSlide 7 Conclusion MAC Cancel Transmit Primitive – Conclusion No unanimous agreement, but consensus was the Cancel Transmit primitive is useful to prevent a packet from being transmitted after it is no longer useful. DENSO was asked to investigate the feasibility of including this functionality. –Atheros has indicated to DENSO that their current generation chipsets support the functionality required by the MAC Cancel Transmit primitive.

doc.: IEEE /0015r0 Submission Month YearJanuary 2005 Bryan Wells, DENSO, LA LabsSlide 8 MAC Process Only One Packet at a Time OperationOperation –If the MAC were to receive a new packet for transmission while there is still a packet pending transmission in the MAC, the MAC would cancel the pending transmission and send the new packet. Use CaseUse Case –This functionality would allow upper layers to override pending lower priority or outdated packets with higher priority or updated packets destined for transmission on the same channel. ConclusionsConclusions –802.11e may already provide sufficient QoS. –Cancel Transmit primitive could sufficiently support the desired functionality, making this requirement unnecessary.

doc.: IEEE /0015r0 Submission Month YearJanuary 2005 Bryan Wells, DENSO, LA LabsSlide 9 References p WAVE-MAC-Supplement-Proposal Review