1. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 1 Multicast Transmission in WLAN Date: 2008-05-13 Authors:

2. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 2 Abstract -Participation in Multicast Session signalling and request for Reliable Multicast Transmission -Message flow for reliable multicast setup and operation -Synchronization of sequence numbers

3. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 3 Need for Signaling to indicate participation in Multicast Group Multicast recipient needs reliable Multicast Transmission –Poor link condition –Multicast stream needs reliability to ensure QoS Allow power save –If the STA is a PSMP capable STA, AP can schedule Multicast and Unicast transmissions to the STA in the same PSMP sequence

4. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 4 Determining Unicast entities that are part of Multicast Group Explicit signaling : –AP indicates support for reliable Multicast Broadcast (RMB) in the capability field : B7 in Wireless Network Management Capabilities –STAs can transmit Reliable MB Request Frame to signal participation in a Multicast Group and request for setting up a reliable Multicast Transmission

5. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 5 Reliable MB Request frame MAC HeaderFrame BodyFCS Category(3) 1 byte Action = 3 1 bytes Dialong Token 1 byte Multicast Address 6 bytes 1 1 11Bits Trigger Code 1 byte RMB TIDReserved BA Valid TID 4 Unicast frame transmitted by MB Recipient to the MB transmitter Interpretation of the fields in next slide

6. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 6 Interpretation of the fields Field Interpretation and usage of the field RMB = 0, Valid TID = 0 Interpretation : Address = Multicast / Broadcast address. Rest of the fields in Trigger Code is a Don’t care Usage : STA transmits this frame to signal participation in a MB Session RMB = 0, Valid TID = 1 Address = Multicast / Broadcast address. Rest of the fields in Trigger Code are Don’t care Usage : STA transmits this frame to signal that it is no longer participating in the multicast stream as indicated in the Address field RMB = 1, Valid TID = 0 Interpretation : The TID field is a Don’t care, recipient signals that it is participating in the MB session If BA = 1 then the recipient is requesting the transmitter to establish a BA session for the stream. BA = 0 is not a valid setting Usage : If the Multicast stream cannot use any of the current BA sessions established for the recipient or if this is the first request from the recipient to establish a reliable multicast session from the recipient RMB = 1, Valid TID = 1 Interpretation : Recipient signals that it is participating in the MB session If BA = 1 then, the recipient is signaling to the transmitter to use the existing BA session for TID as signaled in the TID field for the multicast stream signaled in the request. If BA = 0 then, the recipient is signaling to the transmitter to tear down the BA session associated with the TID as indicated in the TID field Usage : With BA =1 this field is used to allow a recipient to add a new multicast stream to an existing BA session With BA = 0 this field is used to delete an established BA session because this is the only flow that was using that BA session

7. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 7 Reliable MB Response frame MAC HeaderFrame BodyFCS Category(3) 1 byte Action = 4 1 bytes Dialong Token 1 byte Multicast Address 6 bytes 1 1 11Bits Trigger Code 1 byte RMB TIDRetransmitBA Valid TID 4 RMB field is copied from the Request Frame Unicast frame transmitted by MB Transmitter and destined to a specific recipient Interpretation of the fields in next slide

8. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 8 Interpretation of the fields Field Interpretation and usage of the field RMB = 0, Valid TID = 0 Interpretation : Address = Multicast / Broadcast address. Rest of the fields in Trigger Code is a Don’t care Usage : Transmitter transmits this frame to acknowledge the recipients participation in a MB Session RMB = 0, Valid TID = 1 Address = Multicast / Broadcast address. Rest of the fields in Trigger Code are Don’t care Usage : Transmitter transmits this frame to acknowledge that the recipient is no longer participating in the MB Session RMB = 1, Valid TID = 0 Interpretation : Address field has the Retransmission address, BA = 0 is not a valid setting If BA = 1 then the transmitter is signaling to the recipient that it will use the BA session associated with the TID field for the data of the Multicast Address Retransmit = 1 : Data is retransmitted after receiving BA from all the recipients Retransmit = 0 : Data is retransmitted even with out soliciting BA from all the recipients Usage : Signal retransmission address and the TID that will be used for the stream RMB = 1, Valid TID = 1 Interpretation : Address field has the Retransmission address If BA = 1 then, the transmitter is signaling to the transmitter that it will create a new BA session for the stream using the TID as indicated in the TID field Retransmit = 1 : Data is retransmitted after receiving BA from all the recipients Retransmit = 0 : Data is retransmitted even with out soliciting BA from all the recipients If BA = 0 then, the transmitter is signaling to the transmitter that it will tear down the BA session associated with the TID as indicated in the TID field (Retransmit field is Don’t care) Usage : With BA =1 new BA session will be established With BA = 0 last session that is using an existing BA session

9. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 9 Retransmission Address Assign locally administered “Multicast Address” –Retransmitted data needs to be encrypted (new value in Address 1 field) –Nothing needs to be specified in the standard Flip one bit in the prefix that would be appended to the IP multicast address to create the “Multicast Address” – If the retransmitted data is not encrypted then in the standard it needs to be specified that the recipient should flip the AAD field of the received retransmitted data –If the retransmitted data is encrypted again (with new value in Address 1 field) nothing needs to be specified in the standard

10. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 10 Proposed Algorithm Messages marked in blue color are present if the Multicast Recipient requests for reliable multicast session (RMB bit = 1 in Reliable MB Request frame) and the transmitter signals that it is going to set up a new BA session Reliable MB Request Frame MSG 1 MSG 2 MSG 3 MSG 4 Reliable MB Response Frame ADDBA Request Frame Multicast/Broadcast Data Receiver ADDBA Response Frame Multicast/Broadcast Data Transmitter Multicast Data Transmission Explicit BAR Frame / Implicit Signalling during PSMP BA Frame Repeat for recepients who requested Reliable Multicast Broadcast Retransmit Multicast Data with signalled MAC address for retransmission

11. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 11 Mapping of Multicast/Broadcast (MB) Stream for each STA STAs that require/support reliability in receiving MB streams should have a TID assigned for each MB stream for which they need reliability TIDs are assigned dynamically (QoS type TID’s) and the STA has prior knowledge of the current BA sessions established between the AP and the STA

12. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 12 Multicast Data frame QoS Multicast Data frame –ACK Policy bit setting When transmitting Multicast data with in a PSMP sequence the rules of ACK Policy setting follow the rules as described in PSMP When transmitting Multicast data outside PSMP sequence –the ACK policy shall be set to “No Ack” –STAs that need reliable Multicast map the received “Multicast Address” to a the corresponding TID –STAs transmit BA in response to explicit BAR only Non QoS Multicast Data –STAs that need reliable Multicast map the received “Multicast Address” to a specific TID and the STA transmits a BA/MTBA in response to explicit BAR/MTBAR

13. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 13 Synchronizing Sequence numbers after BA Setup RX side –The starting sequence number is set to the sequence number of data frame received after setting up the BA TX side –The starting sequence number is set to the starting sequence number of the first frame transmitted after setting up the BA

14. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 14 Rules at TX BA is requested explicitly outside PSMP Explicit request: BAR/MTBAR frame has Bit 3 in BA control field to indicate that the request is for MB stream, TID corresponds to the TID of the MB stream at the RX STA ACK Policy B0 MT BA/BAR B1 Multicast/Broadcast MB (B2) Reserved (B3-B11) TID (B12-15) Window updates are done as per the rules of regular BA Decision to retransmit the data (either using multicast address or unicast address) is at the discretion of the transmitter

15. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 15 Rules at RX BA/MTBA frames that carry the bitmap of MB stream shall set Bit 3 in BA control field, and the TID value corresponds to the MB stream that was signaled for this STA for the specific MB stream ACK Policy (B0) MTBA/BAR (B1) Multicast/Broadcast MB (B2) Reserved (B3-B11) TID (B12-B15) Window updates are done as per the rules of regular BA if data is received addressed to the multicast address or if data for the TID is transmitted as a unicast frame When the window is full and there is new data received the starting sequence number of the Bit Map is shift to accommodate the new data

16. doc.: IEEE 802.11-08/0615r0 Submission May 2008 Naveen K. Kakani, Nokia IncSlide 16 FBMS Based Streams If the AP supports FBMS then STAs that are participating in reliable Multicast/Broadcast can negotiate a specific DTIM period for the retransmission data (using retransmission MAC address) Nothing new required for the baseline FBMS mechanism to setup the DTIM period for the retransmission data