IEEE 802.11-20/0783r2 EHT-SIG Compression Modes Overview
Explore the compression modes introduced in IEEE 802.11 standards, including HE-SIG-B compression in 11ax and compression modes 1 and 2 in 11be. Learn about the different modes of EHT-SIG and the alignment requirements for MS-EHT-SIG in 11be for multi-segment structures.
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May 2020 doc.: IEEE 802.11-20/0783r2 EHT-SIG Compression Format Date: 2020-05-12 Authors: Affiliations Address Phone email Name Ross Jian Yu ross.yujian@huawei.com Huawei Mengshi Hu Huawei Ming Gan Huawei Submission Slide 1 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Recap 11ax SIG compression In 11ax, a compression mode of HE-SIG-B is introduced, there is no common field in HE-SIG-B for compression mode. In HE-SIG-A, there exist HE-SIG-B Compression field and Number Of HE- SIG-B Symbols Or MU-MIMO Users Field. When the HE-SIG-B compression field indicates 1, Number Of HE-SIG-B Symbols Or MU-MIMO Users Field indicates the number of MU-MIMO users and is set to the number of MU- MIMO users minus 1. In 11ax, for compression mode, the exact number of OFDM symbols in the HE- SIG-B field is calculated based on the number of User fields in the HE-SIG-B content Channel. Submission Slide 2 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Recap 11be SIG compression In [1], two compression modes are proposed for 11be: Compression mode 1: Used for Full BW SU or Full BW MU-MIMO; RU allocation info in the common field is omitted Compression mode 2: Used for Punctured SU or Punctured MU-MIMO; RU allocation info in the common field is replaced by a punctured channel info with granularity of 20MHz Submission Slide 3 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Three modes of EHT-SIG The following three modes are considered for EHT-SIG: Non-compressed mode (for OFDMA case): RU allocation subfields only, and the n umber of RU allocation subfields is equal to N, and N can be defined as in 11ax Compressed mode 1 (punctured non-OFDMA case): there is no RU allocation subfi eld, only one preamble puncture subfield or only one special RU allocation subfield , which contains entries for large MRU combinations. People may have different pr eference regarding terminology. Compressed mode 2 (non-punctured non-OFDMA case): no RU allocation subfield s/preamble puncture indication. This mode can also be seen as a special mode of co mpressed mode 1, where within the puncture indication/special RU allocation subfi eld, it indicates RU types of no puncture, e.g., 2*996, 3*996, 4*996. There should exist indication in U-SIG differentiating: Non-compression Mode, Compression Mode 1 and Compression Mode 2 Non-compression Mode and Compression Mode Under the above assumptions, we further discuss the alignment issues reg arding compression mode. Submission Slide 4 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Alignment Requirement for MS-EHT-SIG In 11be, considering multi-segment EHT-SIG or A-PPDU structure [2,3], EHT- SIG needs to be aligned between each segments. The group has the following SPs in green [4,6] and this requirement is also mentioned in [2]: Submission Slide 5 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Alignment issues of compression mode If 11be follows 11ax, the number of EHT-SIG symbols is reinterpreted as the number of MU-MIMO users for a non-OFDMA transmission, then the exact number of OFDM symbols in the EHT-SIG field is calculated based on the number of User fields in the EHT-SIG content Channel: For sub-PPDU-2 with 2 users full MU-MIMO, in each CC, there only exists 1 user field with CRC and tail. Assuming 38 bits, and also assume 4 bits U-SIG overflow info, with MCS 0, then there will be 2 EHT-SIG symbols for sub-PPDU-2. The above method cannot indicate the exact number of EHT-SIG symbols after padding. Aggregated PPDU Sub-PPDU-3 (non-compression mode with 8 EHT-SIG symbols) Sub-PPDU-2 (2 users, full BW MU-MIMO), need to padding to 8 EHT-SIG symbols 80MHz 80MHz Sub-PPDU-1 (non-compression mode with 8 EHT- SIG symbols) 160MHz Hence, compression mode cannot be applied (also mentioned in [2]). Or we can say with MS-EHT-SIG or A-PPDU structure, compression mode can be seldom applied in EHT PPDU. Submission Slide 6 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Simple solution to enable compression mode If the number of EHT-SIG symbols is always used to indicate number of EHT-SIG symbols and not reinterpreted as anything else. Then the issue is solved. Enable alignment all the time For the number of MU-MIMO users field (up to 4 bits), it is indicated in the common field of the EHT-SIG instead. May be only needed for compression mode, can also be merged to preamble puncture indication The cost of maximum 4 bits saves the overhead of one or multiple RU allocation subfields (8/9/10 bits multiplies by N) variable symbol 2 symbols ... RL- SIG EHT-SIG L-STF L-LTF L-SIG U-SIG 0 or TBD bits 4 bits Preamble puncture indication Number of MU-MIMO users Number of EHT-SIG Symbols (5 bits) ... ... ... CRC+Tail User specific field Submission Slide 7 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Extending applicable scenario of compression mode Level 0: if 11be follows 11ax, then compression mode can seldom be applied. Can only be applied if no alignment is needed, usually non-OFDMA transmission across the whole BW. Also cannot be applied in A-PPDU concept Level 1: By the previous simple solution, compression mode can be further applied if the transmission is non-OFDMA within a sub-PPDU. 4 4 10 28 10 U-SIG Overflow MU- MIMO # EHT-SIG CC11 CRC+Tail CRC+Tail User field 1 L-preamble+U-SIG1 U-SIG Overflow MU- MIMO # EHT-SIG CC12 Data CRC+Tail User field 2 CRC+Tail L-preamble+U-SIG1 STA1,2 Padding MU-MIMO (STA1-STA2) MU- MIMO # U-SIG Overflow BW=80Mhz EHT-SIG CC11 CRC+Tail CRC+Tail User field 1 L-preamble+U-SIG1 EHT-SIG CC12 MU- MIMO # U-SIG Overflow L-preamble+U-SIG1 CRC+Tail User field 2 CRC+Tail U-SIG Overflow MU- MIMO # EHT-SIG CC21 User field 3 User field 4 CRC+Tail CRC+Tail L-preamble+U-SIG2 U-SIG Overflow MU- MIMO # EHT-SIG CC22 Data CRC+Tail User field 5 User field 6 CRC+Tail L-preamble+U-SIG2 MU-MIMO (STA3-STA6) STA3-STA6 U-SIG Overflow MU- MIMO # EHT-SIG CC21 User field 3 User field 4 CRC+Tail CRC+Tail L-preamble+U-SIG2 BW=80Mhz U-SIG Overflow MU- MIMO # EHT-SIG CC22 User field 5 User field 6 CRC+Tail CRC+Tail L-preamble+U-SIG2 4 4 10 28 28 10 Submission Slide 8 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Extending applicable scenario of compression mode Level 2: Below we introduce a more flexible scenario for compression mode. The compression mode can be applied if the transmission of the STAs of one parking segment is non-OFDMA, then the compression mode can be applied. Data of STA1-6 is OFDMA, whilst data of STA3-6 is non-OFDMA. Can be implementation specific and transparent to STAs if level 1 is supported. Total: 72 bits, 3 symbols with MCS0 before padding 4 10 10 10 28 10 Data STA1 Data STA2 U-SIG Overflow RU allocation subfield 1 RU allocation subfield 3 EHT-SIG CC11 CRC+Tail CRC+Tail User field 1 L-preamble+U-SIG1 U-SIG Overflow RU allocation subfield 2 RU allocation subfield 4 EHT-SIG CC12 CRC+Tail User field 2 CRC+Tail L-preamble+U-SIG1 STA1,2 U-SIG Overflow RU allocation subfield 1 RU allocation subfield 3 BW=80Mhz EHT-SIG CC11 CRC+Tail CRC+Tail User field 1 L-preamble+U-SIG1 EHT-SIG CC12 U-SIG Overflow RU allocation subfield 2 RU allocation subfield 4 L-preamble+U-SIG1 CRC+Tail User field 2 CRC+Tail Preamble puncture indication Preamble puncture indication Preamble puncture indication Preamble puncture indication U-SIG Overflow MU- MIMO # EHT-SIG CC21 Data User field 3 User field 4 CRC+Tail CRC+Tail L-preamble+U-SIG2 Preamble puncture indication will indicate xx11 1111 in segment 2. MU-MIMO (STA3-STA6) U-SIG Overflow MU- MIMO # EHT-SIG CC22 CRC+Tail User field 5 User field 6 CRC+Tail L-preamble+U-SIG2 STA3-STA6 U-SIG Overflow MU- MIMO # EHT-SIG CC21 User field 3 User field 4 CRC+Tail CRC+Tail L-preamble+U-SIG2 BW=160Mhz U-SIG Overflow MU- MIMO # EHT-SIG CC22 User field 5 User field 6 CRC+Tail CRC+Tail L-preamble+U-SIG2 Total: 92 bits, 4 symbols with MCS0 4 8 4 10 28 28 10 Submission Slide 9 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Bitwidth for the number of EHT-SIG symbols field In 11ax, the bitwidth for the number of HE-SIG-B symbols is 4. And it is proved not enough for 11ax if the HE-SIG-B-MCS field is set to 0, 1, 2, or 3 regardless of the value of the HE-SIG-B DCM field, or the HESIG-B-MCS field is set to 4 and the HE-SIG-B DCM field is set to 1 [5]. With 16 HE-SIG-B symbols, only up to 24 users can be scheduled in one OFDMA PPDU no matter how large the bandwidth of OFDMA PPDU is if SIG B uses MCS 0 In 11be, the bandwidth is even larger, and the number of scheduled users can be even larger. So it is proposed to have 5 bits for the number of EHT-SIG symbols field. Can support up to 32 number of EHT-SIG symbols, about 48 users with MCS0. Submission Slide 10 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Summary We discuss the alignment issue of compression mode in 11be under the scenario of MS-EHT-SIG. A simple solution would be that the number of EHT-SIG symbols field always exist in a PPDU transmitted to multiple users. We then further discuss extending applicable scenario of compression mode. Submission Slide 11 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Straw Poll #1 Do you agree that the bitwidth of number of EHT-SIG symbols field is 5 if it exists in U-SIG? Submission Slide 12 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Straw Poll #2 Do you agree that the number of EHT-SIG symbols field always exist in a PPDU transmitted to multiple users? The filed is not reinterpreted as the number of MU-MIMO users Submission Slide 13 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 References [1] https://mentor.ieee.org/802.11/dcn/20/11-20-0049-02-00be-ppdu-types-and- u-sig-content.pptx, Sammer Vermani, Qualcomm [2] https://mentor.ieee.org/802.11/dcn/20/11-20-0693-00-00be-aggregated- ppdu-for-large-bw.pptx, Rui Cao, NXP [3] https://mentor.ieee.org/802.11/dcn/20/11-20-0674-00-00be-forward- compatible-ofdma.pptx, Xiaogang Chen, Intel [4] https://mentor.ieee.org/802.11/dcn/20/11-20-0545-01-00be-multi-segment- eht-sig-design-discussion.pptx, Ross Jian Yu, Huawei [5] https://mentor.ieee.org/802.11/dcn/18/11-18-0541-01-00ax-fix-the-issue-on- number-of-he-sig-b-symbols.pptx, Ming Gan, Huawei [6] https://mentor.ieee.org/802.11/dcn/20/11-20-0566-18-00be-compendium-of- straw-polls-and-potential-changes-to-the-specification-framework- document.docx, Edward Au, Huawei Submission Slide 14 Ross Jian Yu, et al Huawei Technologies
May 2020 doc.: IEEE 802.11-20/0783r2 Appendix: Number of HE-SIG-B Symbols Or MU-MIMO User field and HE-SIG-B Compression Field Submission Slide 15 Ross Jian Yu, et al Huawei Technologies
May 2020 Appendix: Example without compression mode doc.: IEEE 802.11-20/0783r2 Total: 72 bits, 3 symbols with MCS0 before padding 4 10 10 10 28 10 Data STA1 Data STA2 U-SIG Overflow RU allocation subfield 1 RU allocation subfield 3 EHT-SIG CC31 CRC+Tail CRC+Tail User field 1 L-preamble+U-SIG3 U-SIG Overflow RU allocation subfield 2 RU allocation subfield 4 EHT-SIG CC32 CRC+Tail User field 2 CRC+Tail L-preamble+U-SIG3 STA1,2 U-SIG Overflow RU allocation subfield 1 RU allocation subfield 3 BW=80Mhz EHT-SIG CC31 CRC+Tail CRC+Tail User field 1 L-preamble+U-SIG3 EHT-SIG CC32 U-SIG Overflow RU allocation subfield 2 RU allocation subfield 4 L-preamble+U-SIG3 CRC+Tail User field 2 CRC+Tail U-SIG Overflow RU allocation subfield 5 RU allocation subfield 7 RU allocation subfield 9 RU allocation subfield 11 EHT-SIG CC41 CRC+Tail CRC+Tail User field 3 User field 4 Data L-preamble+U-SIG4 MU-MIMO (STA3-STA6) EHT-SIG CC42 U-SIG Overflow RU allocation subfield 6 RU allocation subfield 8 RU allocation subfield 10 RU allocation subfield 12 L-preamble+U-SIG4 User field 5 User field 6 CRC+Tail CRC+Tail STA3-STA6 RU allocation subfield 5 RU allocation subfield 7 RU allocation subfield 9 RU allocation subfield 11 U-SIG Overflow EHT-SIG CC41 User field 3 User field 4 CRC+Tail CRC+Tail L-preamble+U-SIG4 BW=160Mhz EHT-SIG CC42 RU allocation subfield 6 RU allocation subfield 8 RU allocation subfield 10 RU allocation subfield 12 U-SIG Overflow L-preamble+U-SIG4 User field 5 User field 6 CRC+Tail CRC+Tail Total: 120 bits, 5 symbols with MCS0 4 10 10 10 10 10 28 28 10 Submission Slide 16 Ross Jian Yu, et al Huawei Technologies
May 2020 Appendix 2: examples in A-PPDU: save 3 symbols of EHT-SIG overhead doc.: IEEE 802.11-20/0783r2 Total: 61 bits, 3 symbols with MCS0 before padding 10 10 10 21 10 Data STA1 Data STA2 RU allocation subfield 1a RU allocation subfield 3a HE-SIG-B CC1 CRC+Tail CRC+Tail User field 1 L-preamble+HE-SIG-A HE-SIG-B CC2 RU allocation subfield 2a RU allocation subfield 4a CRC+Tail User field 2 CRC+Tail L-preamble+HE-SIG-A STA1,2 RU allocation subfield 1a RU allocation subfield 3a BW=80Mhz HE-SIG-B CC1 CRC+Tail CRC+Tail User field 1 L-preamble+HE-SIG-A HE-SIG-B CC2 RU allocation subfield 2a RU allocation subfield 4a L-preamble+HE-SIG-A CRC+Tail User field 2 CRC+Tail U-SIG Overflow RU allocation subfield 1b RU allocation subfield 3b RU allocation subfield 15b EHT-SIG CC21 ... CRC+Tail CRC+Tail User field 3 User field 4 Data L-preamble+U-SIG2 MU-MIMO (STA3-STA6) EHT-SIG CC22 U-SIG Overflow RU allocation subfield 2b RU allocation subfield 4b RU allocation subfield 16b L-preamble+U-SIG2 ... User field 5 User field 6 CRC+Tail CRC+Tail STA3-STA6 RU allocation subfield 1b RU allocation subfield 3b RU allocation subfield 15b U-SIG Overflow EHT-SIG CC21 ... User field 3 User field 4 CRC+Tail CRC+Tail L-preamble+U-SIG2 BW=320Mhz EHT-SIG CC22 RU allocation subfield 2b RU allocation subfield 4b RU allocation subfield 16b U-SIG Overflow L-preamble+U-SIG2 ... User field 5 User field 6 CRC+Tail CRC+Tail Total: 160 bits, 7 symbols with MCS0, non- compressed mode ... 4 80 10 28 28 10 U-SIG Overflow Preamble puncture MU-MIMO users CRC+Tail CRC+Tail User field 3 User field 4 Total: 86 bits, 4 symbols with MCS0, compressed mode U-SIG Overflow Preamble puncture MU-MIMO users User field 5 User field 6 CRC+Tail CRC+Tail U-SIG Overflow Preamble puncture MU-MIMO users User field 3 User field 4 CRC+Tail CRC+Tail U-SIG Overflow Preamble puncture MU-MIMO users User field 5 User field 6 CRC+Tail CRC+Tail 3 or more 4 3 10 28 28 10 Submission Slide 17 Ross Jian Yu, et al Huawei Technologies
