Bits Consideration for SIGNAL fields Month Year Month Year doc.: IEEE 802.11-yy/xxxxr0 doc.: IEEE 802.11-10/0382r0 Bits Consideration for SIGNAL fields Date: 2010-03-15 Authors: Slide 1 Joonsuk Kim, et. al.. Page 1 John Doe, Some Company Joonsuk Kim

Preamble Structure [1] T Rate=6Mbps Length determined by T 2 symbols L-STF L-LTF L-SIG VHTSIGA VHT-STF VHT-LTFs VHTSIGB VHTData T VHT auto-detection Joonsuk Kim, et. al..

Different Natures for VHT-SIGs in MU VHT-SIGA contains the “common” bits for all clients. Bits/Fields that deliver common information for all users need to be located in VHT-SIGA Information on the number of VHT-LTFs to follow also need to be located in VHT-SIGA Better to indicate the number of spatial streams earlier for a receiver to be prepared for decoding DATA Bandwidth indication also needs to be informed earlier before VHT-STF. VHT-SIGB contains user-specific information (e.g. modulation and coding rate) and is spatially multiplexed for different clients. Typically, VHT-STF,VHT-LTFs and VHT-SIGB are being beamformed in order to minimize the interference terms for other users It is placed after all the VHT-LTFs to enable better receiver side interference mitigation in DL-MU before decoding VHT-SIGB. Joonsuk Kim, et. al..

Bits/Fields to Consider in VHT-SIGs Bandwidth  VHT-SIGA Needs to be informed early before VHT-STF Group ID Field  VHT-SIGA It indicates the number of VHT-LTFs and the stream numbers to decode for each STA MCS  VHT-SIGB MCS is a user-specific information STBC  VHT-SIGA If Nsts is not the same as Nss with STBC encoded symbols, it needs to be informed early for a recipient to be prepared to decode symbols correctly. Short GI Sounding Smoothing Coding Type CRC & Tail: Located at both VHT-SIGA and SIGB. Bits in Italic font are not covered in this presentation Other new bits/fields are possible to consider if necessary, for example, MAC ID, Number of Extension Streams and Resolvable/Non-resolvable LTF Indication Joonsuk Kim, et. al..

GroupID Field in VHT-SIG A [2] VHT-SIG A tells the number of columns of Qk (steering matrix for user k) in the order of assigned user number in the group-definition-field. All STAs can listen to VHT-SIG A, so each participating user knows when to start to detect its own stream. VHT-SIG A includes following field (called GroupID field) Some of these bits may be reused for SU-MIMO packet Usage scenario of GroupID If it is non–zero The receiving STA(s) use the GroupID as described above If it is zero (Only the first 3 bits out of x bits in Nsts field are sufficient to indicate the number of streams), the packet can be either Single user transmission (SU-MIMO packet) A transmission when the group membership between the transmitter and the receiving STA(s) is not established yet. A transmission that needs to bypass a group (for example, a broadcast packet) y bits x bits Group ID # of columns of Qk (Nsts_k) for k=1,2,3,4 Qk is the steering matrix for user k x>0, y >0 x bits indicate the number of columns of Nsts for user 1,2,3 and 4. Details are TBD It is possible Nsts_k = 0 for certain k if STA k is not a recipient of MU-MIMO packet. Joonsuk Kim, et. al..

MCS Field in VHT-SIG B For 802.11n, we have 77 MCS sets to cover many combinations for up to 4 streams with unequal modulations. For 802.11ac, we’re talking about 256 QAM and up to 8 streams, which may end up with too many combinations. For testing purpose, we have too many modes. With simpler design for MCS table, we don’t need a giant LUT for implementation. We propose not to allow unequal modulation for 11ac MCS set. Joonsuk Kim, et. al..

STBC Bits in VHT-SIG A Spatial Mapping STBC . . . Nss Nsts Ntx 802.11n has a hybrid mode of SDM and STBC (for example, Nss=3 and Nsts=4) If we allow this with up to 8 streams for 11ac, it also causes a lot of STBC modes (testing issue) We propose only one bit for STBC mode (Almouti scheme) If Nsts is even, Nsts = 2*Nss If Nsts is odd, Nsts = 2*Nss – 1 (only one stream is not STBC encoded) Whether or not we allow this case (Nsts is odd) is TBD If it is allowed, the position of spatial-stream that is not encoded by STBC is TBD Joonsuk Kim, et. al..

Reference [1] 11-10/0070r5 “802.11ac Preamble.ppt” [2] 11-10/0073r2 “GroupID Concept for Downlink MU-MIMO Transmission.ppt” Joonsuk Kim, et. al..

Straw Poll on Bit Allocation in VHT-SIGs Do you support including bits for Bandwidth, STBC and GroupID field in VHT-SIGA and including MCS field in VHT-SIGB, and editing the spec framework document, 11-09-0992, accordingly? Yes: No: Abs: Joonsuk Kim, et. al..

Straw Poll on MCS field Do you support allowing only equal modulation MCS across all streams per user and stating this in the spec framework document, 11-09-0992? Yes: No: Abs: Joonsuk Kim, et. al..

Straw Poll on STBC bit Do you support to have one bit to indicate STBC mode and to edit the spec framework document, 11-09-0992, accordingly? Yes: No: Abs: Joonsuk Kim, et. al..

Straw Poll on GroupID Do you support adopting the value of GroupID (whether it is zero or not) as a method as described in Slide 5 of 11-10-0382r0 and editing the spec framework document, 11-09-0992, accordingly? Yes: No: Abs: Joonsuk Kim, et. al..