Presentation on theme: "GroupID Concept for Downlink MU-MIMO Transmission"— Presentation transcript:
1 GroupID Concept for Downlink MU-MIMO Transmission January 2010doc.: IEEE /0073r0January 2010GroupID Concept for Downlink MU-MIMO TransmissionDate:Authors:Joonsuk Kim, Broadcom Corp.Joonsuk Kim
2 Background Non-resolvable LTFs Resolvable LTFs January 2010BackgroundNon-resolvable LTFs# LTF symbols = maxi(# spatial streams for user i)Each user cannot estimate HiQi reliably unless ||HiQj||=0We cannot guarantee this assumption in general.AdvantageShorter preambleDisadvantageIncompatible with high-performance MU downlink algorithmsIncompatible with certain antenna configurationsIncompatible with interference suppressionResolvable LTFs# of LTF symbols >= total # of spatial streamsEach user can measure both its signal channel and all interference channelsWe can enhance the MU-MIMO performance that cannot be obtained with unresolvable LTFs at the cost of longer preamble.For resolvable LTFs, we need a mechanism to identify which streams are for which user.Joonsuk Kim, Broadcom Corp.
3 January 2010doc.: IEEE /0073r0January 2010Group ID DefinitionA group ID (y bits) is used to specify a group of K MU-MIMO users in a specified orderGroup ID is defined by AP and is communicated to STAsGroup ID may be transmitted within the body of a management frameManagement frame may be a sounding frame or a non-sounding frameManagement frame without sounding may be used to indicate AID list for a Group ID without requesting channel measurement feedback frame (when the management frame transmitter already has CSI information)A group ID is modified or created by transmitting group-definition-fieldSee next slideGroup ID may be overloaded. AP may assign same Group ID to mutually exclusive sets of users if necessaryA station can be member of up to 2^y groupsJoonsuk Kim, Broadcom Corp.Joonsuk Kim
4 Group-definition-field January 2010Group-definition-fieldGroup-definition-field is defined as followingK number of MU-MIMO users per group (K=4 for example)Several group-definition-fields may be transmitted in one management or sounding frameAnother field indicates how many group-definition-fields are included in the management or sounding frameUpon reception of Group-definition-field, each STA knows its own STA number (one to four in this example) associated with group ID.Group ID is managed by AP.AID2AID3AID4Group IDAID1AID stands for Associated IdentifierAID may be replaced by some other field that identifies STAsJoonsuk Kim, Broadcom Corp.
5 An Example of Sounding Mechanism January 2010An Example of Sounding MechanismSoundingAPIn sounding packet, four AIDs are included in MAC header or DATA.Each AID represents MAC address to sound for MU-MIMOFrom this order, each destination STA knows the assigned number (1 to 4)STA1STA2STA3STA4MU-MIMO PackettimeGroup-definition-field in DATA or MAC headerGroup-ID-field in VHT-SIG AFeedback Frames- Details are TBD -Sounding packet includes the MAC addresses of recipients to sound (possible candidates for MU-MIMO packet recipients)The order of AIDs (Associated ID) in Group-definition-field in the PHY payload indicates the station number (1 to 4).AP will choose the participating STAs for MU-MIMO packet based on available downlink traffic and current channel state information for all the STAsAll of STAs that were included in Group-definition-field are not required to be recipients of MU-MIMO packet.Joonsuk Kim, Broadcom Corp.
6 Stream Number Indication in VHT-SIG A  January 2010Stream Number Indication in VHT-SIG A VHT-SIG A tells the number of columns of Qk (steering matrix for user k) in the order of assigned user number in the sounding frame.All STAs can listen to VHT-SIG A, so each participating user knows when to start to detect its own stream.VHT-SIG A may include following bits (called MU-MIMO bits)Some of these bits may be reused for SU-MIMO packetMU indication1 bit# of columns of Qk (Nsts_k) for k=1,2,3,4x bitsGroup IDy bitsQk is the steering matrixfor user kx bits indicate the number of columns of Nsts for user 1,2,3 and 4. Details are TBDIt is possible Nsts_k = 0 for certain k if STA k is not a recipient of MU-MIMO packet.Joonsuk Kim, Broadcom Corp.
7 January 2010SummaryMU-MIMO with resolvable LTFs requires a mechanism to indicate which streams are for which user.Group ID and MU-MIMO bits in VHT-SIG field are introduced for this informationIn MU-MIMO bits,For SU, MU-MIMO indication bit is set to 0Some of MU-MIMO bits may be reused for other purposeFor MU, MU-MIMO indication bit is set to 1.Joonsuk Kim, Broadcom Corp.
8 Reference  “11-10-0070-00-00ac-802-11ac-preamble.ppt" January 2010 Joonsuk Kim, Broadcom Corp.