January 2011 doc IEEE 802 11 110065 r

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 GCR for mesh Date: January 2011 Authors: Submission Slide 1 Ivan Pustogarov, IITP RAS

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 Groupcast with Retries in TGaa • Groupcast with Retries (GCR) is a flexible service defined in TGaa draft to improve the delivery of group addressed frames while optimizing for a range of criteria. • GCR defines two retransmission policies for group addressed frames: – GCR-Unsolicited-Retry • When using the GCR-Unsolicited-Retry delivery method for a group address, the AP retransmits an MSDU one or more times to increase the probability of correct reception at STAs that are listening to this group address. – GCR-Block-Ack • The GCR-Block-Ack delivery method extends the block acknowledgement mechanism to group addressed frames. Submission Slide 2 Ivan Pustogarov, IITP RAS

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 What can TGaa do for mesh? • According to PAR, TGaa is indented to improve audio and video streaming, including multicast/broadcast audio and video streams • TGaa PAR does not specify directly the type of BSS, however the current TGaa draft is written with Infrastructure BSS in mind (AP and non-AP STAs are mentioned everywhere in the text) • Audio/video applications for mesh are of the same (very high) importance as for infrastructure BSS • Some TGaa mechanisms may be adapted for usage in a mesh: in particular GCR mechanism, especially given that little effort shall be done. Submission Slide 3 Ivan Pustogarov, IITP RAS

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 GCR procedure Mesh BSS Infrastructure BSS • TCLAS information element carries the group address • TSPEC information element carries the schedule • GCR group addressed MSDUs shall be sent in an A-MSDU frame format with the RA set to the GCR Concealment address prevents group addressed frames transmitted via GCR from being passed up the MAC-SAP of GCR-incapable STAs. Submission Slide 4 Ivan Pustogarov, IITP RAS

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 Changes required • Introduce new definitions: – Groupcast transmitter: An access point (AP) or a mesh station (mesh STA) that transmits group addressed frames. – Groupcast receiver: A non-access point (non-AP) station (STA) or a mesh STA that receives group addressed frames. • • • Replace “AP” with “Groupcast transmitter” and “non-AP STA” with “Groupcast receiver” Allow using TCLAS and TSPEC elements by mesh STAs to establish a GCR agreement (same is done in TGv for DMS agreement) Concealment scales to mesh networks – An option is to make the concealment address the same for all STAs in a mesh and distribute it in an information element like Mesh ID… – … however it is not necessary. The concealment address may be chosen by each groupcast transmitter locally and stored by a groupcast receiver within a GCR agreement instance. • Mesh STAs shall be taught to wake up according to the GCR schedule carried in TSPEC (same is done for MCCA and already in TGs draft) Submission Slide 5 Ivan Pustogarov, IITP RAS

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 Back up slides Submission Slide 6 Ivan Pustogarov, IITP RAS

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 Multicast approaches in mesh • Two approaches exist in TGs to organize multicast traffic delivery to the intended receivers Unreliable Nonscalable Multicast frames are broadcasted Multicast frames are converted to unicast frames Submission Slide 7 Ivan Pustogarov, IITP RAS

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 Example of more efficient multicast approach in mesh • Multicast tree approach can be used to decrease total number of retransmissions : – We exploit broadcast nature of the medium and use one-hop multicast in branch points. – NOTE: Branch points determine the next stations in the route according to a proprietary tree setup mechanism • Do we have appropriate tools to implement such an approach? Improved Multicast tree approach (minimum one multicast packet transmission in branchpoints). Submission Slide 8 Ivan Pustogarov, IITP RAS

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 GCR-Block. Ack as a building block for efficient multicast in mesh • In the example of multicast tree approach: – Group addressed MCCA reservation can be used to protect onehop multicast traffic from collisions with packets sent by stations in the two-hop neighborhood, BUT: – Currently no ARQ-like mechanism exists to react on multicast transmission errors. Hence: • groupcast audio/video quality may degrade significantly due to packet losses. • Group addressed topology control frames may be lost which leads to broken routes. – One solution is to use GCR-Block. Ack Submission Slide 9 Ivan Pustogarov, IITP RAS

January 2011 doc. : IEEE 802. 11 -11/0065 r 0 Example of draft change Submission Slide 10 Ivan Pustogarov, IITP RAS