UL Beamforming Feedback for IEEE 802.11-24: Enhancing Wireless Communication
Explore the advancements in UL beamforming for IEEE 802.11-24, focusing on feedback mechanisms, throughput gains, and multiple beamforming approaches. Understand the procedures for UL and DL MU-MIMO transmissions, coordinated precoding, and the challenges with feedback in UL sounding. Discover how multiple UL beamforming codebooks can improve robustness for STAs in wireless communication.
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May 2024 doc.: IEEE 802.11-24/0869r0 Beamforming Feedback for UL Beamforming Date: 2024-05-03 Authors: Name Leonardo Lanante Affiliations Ofinno Address Phone email llanante@ofinno.com Serhat Erkucuk Jeongki Kim Jiayi Zhang Tuncer Baykas Submission Slide 1 Leonardo Lanante, Ofinno
May 2024 doc.: IEEE 802.11-24/0869r0 Abstract UL Beamforming has been discussed as a potential feature in 802.11bn [1-4]. In [1,2], it was shown that STAs applying beamforming using both SU PPDUs or UL MU-MIMO can have considerable throughput gains. In [3], it was shown that a coordinated precoding approach can provide even higher throughput gains by designing the precoding matrix independently. In [4], a protocol design for UL Beamforming was discussed In this contribution, we discuss how to support multiple types of beamforming approaches in the UL. Submission Slide 2 Leonardo Lanante, Ofinno
May 2024 doc.: IEEE 802.11-24/0869r0 HE/EHT TB sounding for DL MU-MIMO transmission MU PPDU NDPA NDP BFRP AP beamformed BA BFR STA 1 BA BFR STA 2 HE/EHT TB sounding for DL MU-MIMO transmission is shown above. 1. The AP sounds the composite DL channel to multiple STAs. 2. The STAs generates beamforming feedback reports and send back to the AP. 3. The AP generates steering matrices and link parameters (Nss, MCS, RU) for the following MU PPDU. Submission Slide 3 Leonardo Lanante, Ofinno
May 2024 doc.: IEEE 802.11-24/0869r0 UHR UL sounding for UL TB transmission TF TF BFR BA AP NDP TB PPDU STA 1 beamformed NDP TB PPDU STA 2 beamformed A possible procedure for UHR UL sounding for UL TB transmission is shown above. 1. The AP sounds the composite UL channel from multiple STAs. 2. The AP generates beamforming feedback for use by the STAs during UL TB transmissions. 3. The AP sends the beamforming feedback to the STAs and associated link parameters (Nss, MCS, RU) Each STA then uses the indicated beamforming feedback and link parameters to transmit the TB PPDU. Submission Slide 4 Leonardo Lanante, Ofinno
May 2024 doc.: IEEE 802.11-24/0869r0 Problem with Beamforming Feedback in UL Sounding As mentioned in [2], non-AP STAs during UL TB PPDU simply follows the indications by the AP (e.g. MCS, NSS in the trigger frame). This includes whether the non-AP STAs should apply beamforming or not. Thus, it is possible for an AP to generate custom steering matrices and send this to the non-AP STAs instead of the V matrices (e.g. AP coordinated precoding matrices in [3]). In contrast, if we restrict the AP from generating custom steering matrices (i.e. only regular V matrix support), the non-AP STA may reuse the V matrix feedback when transmitting beamformed SU PPDUs. BA BFR TF AP SU PPDU TB PPDU STA 1 beamformed Not beamformed TB PPDU STA 2 beamformed Submission Slide 5 Leonardo Lanante, Ofinno
May 2024 doc.: IEEE 802.11-24/0869r0 Feedback of Multiple UL Beamforming Codebooks To enable STAs to perform both UL SU and UL MU beamforming robustly, the AP may send two or more sets of UL beamforming feedback - one set can be the set of right singular V matrices used for SU PPDU or in non-MU-MIMO UL TB PPDU transmission. - another set can be for AP coordinated precoding or any implementation dependent precoding. BFR MU BFR SU TF BA AP TB PPDU SU PPDU STA 1 Beamformed (BFR MU) Beamformed (BFR SU) TB PPDU STA 2 Beamformed (BFR MU) Submission Slide 6 Leonardo Lanante, Ofinno
May 2024 doc.: IEEE 802.11-24/0869r0 Other solutions While feedback of multiple beamforming codebooks can enable the non-AP STA to perform both SU and TB PPDU beamforming, it is more complex to implement for both APs and non-APs (e.g. memory requirements). Other possible solutions include Solution 1: Restrict the AP operation to only feedback right singular V matrices during UL sounding. The STA uses the V matrices corresponding as steering matrices regardless of the type of PPDU it transmits. Solution 2: The AP indicates to the STA the type of BFR (e.g. whether the BFR comprises right singular V matrices or not). The non-AP STA uses the BFR for beamforming in SU PPDU based on the indication. Submission Slide 7 Leonardo Lanante, Ofinno
May 2024 doc.: IEEE 802.11-24/0869r0 Other issues - The non-AP STAs may not know when to discard UL BFRs that are no longer useful (e.g. channel aging reasons). - The AP can indicate during a TB PPDU exchange whether the BFR can or will no longer be used after the TB PPDU exchange (e.g. due to channel aging, etc.) - The non-AP STA may also discard UL BFRs without telling the AP to free up its memory resources. - The AP/STA can also negotiate a timeout value for the UL BFRs. Within the timeout value, the non- AP STA will keep a received BFR in its memory. Submission Slide 8 Leonardo Lanante, Ofinno
May 2024 doc.: IEEE 802.11-24/0869r0 References [1] https://mentor.ieee.org/802.11/dcn/23/11-23-0263-00-0uhr-triggered- beamforming-in-uhr.pptx [2] https://mentor.ieee.org/802.11/dcn/24/11-24-0108-00-00bn-triggered- beamforming-in-tgbn-follow-up.pptx [3] https://mentor.ieee.org/802.11/dcn/23/11-23-0725-00-0uhr-uplink-mu- mimo-precoding-follow-up.pptx [4] https://mentor.ieee.org/802.11/dcn/24/11-24-0243-00-00bn-protocol- design-for-ul-beamforming.pptx Submission Slide 9 Leonardo Lanante, Ofinno
