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11-10-1244-01-00ac-transmission-mechanism-in-mu-mimo

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  • pg 1
									 Nov.2010                                                       doc.: IEEE 802.11-10/1244r1


     Transmission Mechanism in MU-MIMO
                                     Date: 2010-11-10
Authors:
    Name           Affiliations           Address              Phone                Email
Sun Bo         ZTE Corporation     No.10 Sth Tangyan Rd.   86 29 88723975 Sun.Bo1@zte.com.cn
                                   Xi’an, China
Tian Kaibo     ZTE Corporation     No.10 Sth Tangyan Rd.   86 29 88723973 tian.kaibo@zte.com.cn
                                   Xi’an, China
Lv Kaiying     ZTE Corporation     No.10 Sth Tangyan Rd.   86 29 88724130 lv.kaiying@zte.com.cn
                                   Xi’an, China
Zhendong Luo   China Academy of    No.52 Huayuan Bei Rd.   86 10 62300171 luozhendong@catr.cn
               Telecommunication   Beijing, China
               Research (CATR)
Siyang Liu     China Academy of    No.52 Huayuan Bei Rd.   86 10 62300175 liusiyang@catr.cn
               Telecommunication   Beijing, China
               Research (CATR)
Liang Peng     China Telecom       No. 118, Xizhimengnei 86 10 58552342 liangpeng@ctbri.com.cn
                                   St., Beijing, China




Submission                                     Slide 1                                Sun Bo, ZTE Corp
 Nov.2010                              doc.: IEEE 802.11-10/1244r1


                         Abstract

      A detailed transmission mechanism for MU-MIMO are
      proposed in this contribution, including protective
      mechanism with CTS-to-Self and scheduled multiple
      RTS/CTS frame changes, MU-MIMO data
      transmission, scheduled ACK and exception handling.




Submission                   Slide 2                   Sun Bo, ZTE Corp
 Nov.2010                                         doc.: IEEE 802.11-10/1244r1


                              Background
  • Current data transmission mechanism was designed
    for SU-MIMO only
        – Tx STA sends RTS addressing one Rx STA with one RA field.
        – Rx STA addressed by the RA field responds with CTS.
        – Not all recipients’ neighbors can be protected.
  • Challenges to MU-MIMO data transmission:
        –    Define multiple recipients RTS/CTS protective mechanism.
        –    Define MU-MIMO data selection method.
        –    Define multiple recipients ACK scheduling.
        –    Define retransmission rules.
        –    Be compatible with legacy devices.


Submission                            Slide 3                     Sun Bo, ZTE Corp
  Nov.2010                                      doc.: IEEE 802.11-10/1244r1

         MU-MIMO Transmission Mechanism
• A short PPDU, e.g. CTS-to-Self is used to start MU-MIMO
  transmission and reserve the MAX transmission duration, including all
  RTS/CTSs, MU-MIMO data frames, scheduled ACKs and all xIFSs.

• Multiple RTS/CTS frame exchanges are used to reserve bandwidth for
  multiple recipients
   • The RTS/CTSs for primary STAs will be arranged first.
   • If no CTS is correctly received from any primary STA, the current
     MU-MIMO transmission is failed. If the remaining time within the
     TXOP duration is sufficient to complete an MU-MIMO transmission,
     AP may initiate a new transmission or retry the previous MU-MIMO
     transmission. AP may terminate the TXOP with a CF-END.
   • Otherwise, if a CTS is not correctly received, AP should issue the next
     RTS, until RTS/CTS exchanges for all rest scheduled recipients are
     issued.
 Submission                         Slide 4                     Sun Bo, ZTE Corp
 Nov.2010                                     doc.: IEEE 802.11-10/1244r1

MU-MIMO Transmission Mechanism (cont.)

• MU-MIMO data streams are carried in a MU-MIMO data frame
  based on above reservation.
   • Only data with successfully received CTS will be carried in the MU-
      MIMO data frame;
   • Planned data without a successfully received CTS will be removed
      from the MU-MIMO data frame.

• Scheduled ACKs are used for each recipient to acknowledge the
  receiving of data carried in MU-MIMO data frame.

• A CF-END may be used to terminate a MU-MIMO transmission if the
  transmission is terminated before the duration reserved by CTS-to-
  Self.

Submission                        Slide 5                     Sun Bo, ZTE Corp
 Nov.2010                                                                                              doc.: IEEE 802.11-10/1244r1

         MU-MIMO Transmission Mechanism
                   Analysis
  • A CTS-to-Self is used to reserve a long duration allowing MU-MIMO
    transmission through “duration” field
  • AP checks scheduled recipient one by one by RTS/CTS exchanges
  • The RTS(s) for primary STA(s) should be arranged firstly.
                                        SIFS




                                                                  SIFS
                                                     xIFS




                                                                                   xIFS




                                                                                                SIFS




                                                                                                                           SIFS




                                                                                                                                         SIFS
                           xIFS




                                                                                                              xIFS
   AP        CTS-to-Self          RTS                       RTS                           RTS                        RTS                        Multi-use-data


  STA1                                         CTS


  STA2                                                                    CTS


  STA3                                                                                                  CTS


  STA4                                                                                                                            CTS



Submission                                                               Slide 6                                                        Sun Bo, ZTE Corp
      Nov.2010                                                                                  doc.: IEEE 802.11-10/1244r1

             MU-MIMO Transmission Mechanism
                    Analysis (cont.)
       • If AP does not detect a valid CTS frame within one SIFS period plus a delta
         time (TBD) following the RTS transmission, AP shall initiate the next
         RTS/CTS frame exchange, or start MU-MIMO data frame transmission.
       • The data for a scheduled recipient with unsuccessful RTS/CTS frame
         exchange will be removed from the transmitted MU-MIMO data frame.


                                                               delta
                                    SIFS




                                                              SIFS




                                                                                 SIFS




                                                                                                           SIFS




                                                                                                                        SIFS
                                                 xIFS
                       xIFS




                                                                                              xIFS
AP       CTS-to-Self          RTS                       RTS            RTS                           RTS                       MU-MIMO data




STA1                                       CTS


STA2

STA3                                                                                    CTS


STA4                                                                                                              CTS

                                                         CTS is missed

     Submission                                                        Slide 7                                                 Sun Bo, ZTE Corp
 Nov.2010                                                                   doc.: IEEE 802.11-10/1244r1

        MU-MIMO Transmission Mechanism
               Analysis (cont.)
   •    The ACK(s) is (are) scheduled based on the stream information indicated in
        the Nsts field of MU-MIMO data frame.




                                                       SIFS




                                                                     SIFS




                                                                                  SIFS
                                        SIFS
                  AP     MU-MIMO data




                  STA1                         ACK


                  STA2                                         ACK


                  STA3                                                      ACK


                  STA4                                                                   ACK




Submission                                           Slide 8                                   Sun Bo, ZTE Corp
 Nov.2010                                                                  doc.: IEEE 802.11-10/1244r1
                  MU-MIMO Transmission Mechanism
                         Analysis (cont.)

  • If one ACK is missed, the other STA(s) will send ACK at the
    scheduled time shown as below.




                                               SIFS




                                                            SIFS




                                                                         SIFS
                                  SIFS




                                                                                      SIFS
             AP     MU-MMO data                                                              retransmission


             STA1                        ACK


             STA2

             STA3                                                  ACK



             STA4                                                               ACK


                                           ACK is missed



Submission                                            Slide 9                                          Sun Bo, ZTE Corp
 Nov.2010                                      doc.: IEEE 802.11-10/1244r1

        MU-MIMO Transmission Mechanism
               Analysis (cont.)
 • Only when any primary STA failed to receive MU-MIMO data, the
   AP will initiate retransmission.
 • The retransmission could be:
    • retransmitted MU-MIMO data frame which includes at least the
       data for a primary STA failed in previous MU-MIMO
       transmission, and the data for other STA(s) failed in previous MU-
       MIMO transmission, or
    • retransmitted SU-MIMO data frame which includes the data for a
       primary STA failed in previous MU-MIMO transmission, or
    • retransmitted MU-MIMO data frame which includes at least the
       data for a primary STA failed in previous MU-MIMO
       transmission, and the data for other STA(s) failed in previous MU-
       MIMO transmission, and new data for other STA(s) succeeded in
       previous MU-MIMO transmission
Submission                         Slide 10                    Sun Bo, ZTE Corp
 Nov.2010                                    doc.: IEEE 802.11-10/1244r1


                           Summary

 • The proposed MU-MIMO transmission mechanism provides
   following advantages:
    – Avoiding hidden node problems in BSS and OBSS
    – Compatibility with legacy devices
    – Reuse of legacy RTS/CTS frame exchanges
    – Avoiding unexpected confliction during the gap when a CTS is
       missed
    – Efficient MU-MIMO transmission




Submission                       Slide 11                    Sun Bo, ZTE Corp
 Nov.2010                               doc.: IEEE 802.11-10/1244r1


                       References

 [1] Yun.Joo.Kim , et. al., “considerations-on-mu-mimo-
    protection-in-11ac” IEEE 802.11-10/335r01.
 [2] Allan Zhu, et. al, “txop-sharing-for-dl-mu-mimo-support”
    IEEE 802.11-10/1123r00
 [3] Tian Kaibo, et. al, “Multiple CTSs in MU-MIMO
    transmission” IEEE 802.11-10/1067r00




Submission                   Slide 12                   Sun Bo, ZTE Corp
 Nov.2010                 doc.: IEEE 802.11-10/1244r1




             Thank you!




Submission                                Sun Bo, ZTE Corp

								
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