July 2009 doc IEEE 802 11 090851 r

July 2009 doc. : IEEE 802. 11 -09/0851 r 0 DMS Termination Issue Date: 2009 -07 -14 Authors: Submission 1 Yongho Seok, LGE

July 2009 doc. : IEEE 802. 11 -09/0851 r 0 DMS Termination • DMS is terminated by either STA or AP – STA may terminate DMS when it leaves the multicast session – AP may terminate DMS when the network is overloaded • Some issues are occurred when AP terminates DMS – Termination by AP is general situation and not corner case – Now the next slides focus that AP terminates DMS Submission 2 Yongho Seok, LGE

July 2009 doc. : IEEE 802. 11 -09/0851 r 0 DMS Termination Category • Case 1) – The delivery rate of legacy multicast frame is faster than that of DMS converted frame – This situation may be occurred when the STA is in PS mode • When DTIM interval is one beacon interval and STA does not frequently wakeup AP Beacon Multicast Multicast DMS DMS converted Legacy STA DMS capable STA Submission 3 Yongho Seok, LGE

July 2009 doc. : IEEE 802. 11 -09/0851 r 0 DMS Termination Category • Case 2) – The delivery rate of DMS converted frame is faster than that of legacy multicast frame – This situation is very general because the PHY rate of DMS converted frame is more higher than that of legacy multicast frame Also, when other station is in PS mode, the legacy multicast frame is delivered at DTIM interval AP Beacon Multicast DMS DMS DMS converted converted Legacy STA DMS capable STA Drop Submission Drop 4 Yongho Seok, LGE

July 2009 doc. : IEEE 802. 11 -09/0851 r 0 DMS Termination Category • Case 3) – The delivery rate of legacy multicast frame and DMS converted frame is same (But, exactly it is a race condition) – For making this case, AP shall transmit legacy multicast frame and DMS converted frame iteratively and shall use one queue for the multicast and unicast frames (It is really corner case) AP Beacon Multicast DMS DMS Multicast converted Legacy STA DMS capable STA Drop Submission Drop 5 Drop Yongho Seok, LGE

July 2009 doc. : IEEE 802. 11 -09/0851 r 0 Which problem is occurred in Case 2? • AP terminates DMS because the network is overloaded • After receiving DMS termination message (unsolicited DMS Response frame), the STA starts to receive legacy multicast frame as specified in TGv Draft • But, as shown in Case 2, the STA already received a number of multicast frames by DMS • The received multicast frames after the DMS termination are almost duplicated but the STA doesn’t know which frame is duplicated Submission 6 Yongho Seok, LGE

July 2009 doc. : IEEE 802. 11 -09/0851 r 0 Which problem is occurred in Case 2? AP Beacon Multicast 5 6 7 DMS 10 DMS 11 DMS 12 DMS 13 DMS 14 Unsolicited DMS Response Legacy STA DMS capable STA Drop AP Beacon Drop DMS Terminated Multicast Multicast Multicast 8 9 10 11 12 13 14 15 16 Legacy STA DMS capable STA Duplicated Duplicated Submission 7 Yongho Seok, LGE

July 2009 doc. : IEEE 802. 11 -09/0851 r 0 Which problem is occurred in Case 2? • Last question is how many frames are duplicated • I think that it is absolutely not a little – In previous example, the number of duplicated frames are 7 – The number of duplicated frames may increases as the delivery rate of DMS converted frame is more faster than that of legacy multicast frame – Nobody can say that the number of duplicated frame is a few Submission 8 Yongho Seok, LGE

July 2009 doc. : IEEE 802. 11 -09/0851 r 0 Conclusion • As shown in previous cases, Case 2 is almost general situation of DMS • When AP terminates DMS, STA already received a lot of DMS converted frames • The difference between transmitted DMS converted frames and transmitted legacy multicast frames is the number of duplicated frame in STA • This issue is not corner case of DMS termination and DMS shall resolve this issue Submission 9 Yongho Seok, LGE