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Bits Consideration for SIGNAL fields

Bits Consideration for SIGNAL fields. Date: 2010-03-15. Authors:. Slide 1. Preamble Structure [1]. Rate=6Mbps Length determined by T. 2 symbols. 1 symbol. L-STF. L-LTF. L-SIG. VHTSIGA. VHT-STF. VHT-LTFs. VHTSIGB. VHTData. T. VHT auto-detection.

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Bits Consideration for SIGNAL fields

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  1. Bits Consideration for SIGNAL fields Date: 2010-03-15 Authors: Slide 1 Joonsuk Kim, et. al..

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

  3. 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..

  4. 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..

  5. 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 Qk is the steering matrix for user k Group ID # of columns of Qk (Nsts_k) for k=1,2,3,4 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..

  6. 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..

  7. STBC Bits in VHT-SIG A Spatial Mapping STBC • 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 . . . . . . . . . Nss Nsts Ntx Joonsuk Kim, et. al..

  8. 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..

  9. Straw Poll on Bit Allocation in VHT-SIGs • Do you support including TBD bits for Bandwidth and STBC 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..

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

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

  12. 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..

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