IEEE 802.11-23 MLD Roaming Scenarios

This contribution focuses on discussing MLD roaming scenarios to enable seamless roaming for non-AP MLD STAs, aiming to reduce packet loss and latency during roaming through methods like make before break. Various aspects of Intra V-MLD Roaming architecture are explored, including optimizing data paths, providing lossless roaming, and coordination between MLDs and APs in different frequency bands.

• IEEE
• MLD
• Roaming
• Seamless
• Latency

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1. November 2023 doc.: IEEE 802.11-23/xxxxr0 MLD Roaming scenarios Date: 2024-01-12 Authors: Name Affiliations Address Phone email Gabor Bajko MediaTek James Yee Frank Hsu Yonggang Fang Kaiying Lu Submission Slide 1 MediaTek

2. November 2023 doc.: IEEE 802.11-23/xxxxr0 Abstract This contribution discusses MLD roaming scenarios with enabling seamless roaming for non-AP MLD STAs o Make before break o Eliminate the packet loss STA assists in the roaming to reduce packet loss and latency Submission Slide 2 MediaTek

3. November 2023 doc.: IEEE 802.11-23/xxxxr0 Scenario 1. Intra V-MLD Roaming DS Purpose: - Extend the EHT architecture to allow APs/MLDs to be not co-located - Optimize data path to DS to reduce latency - Provide lossless roaming - Each MLD may consist of one or more Affiliated APs ETH switch Data path Virtual MLD Virtual MLD Management path (proprietary) MLD1 MLD2 Roaming/Virtual MLD: - Non-Link specific management frame endpoint - STA MLD associates with V-MLD MAC address - Reordering buffer is in the MLDs only (no buffer in the V-MLD) - V-MLD does not have access to the DS STA MLD Submission Slide 3 Mediatek

4. November 2023 doc.: IEEE 802.11-23/xxxxr0 Initial phase: Router DL Data Ethernet Switch DL Ethernet frame UL Data UL Ethernet frame AP MLD1 AP MLD2 2.4GHz 5GHz 5GHz 2.4GHz DL Data & UL DATA STA MLD Submission Slide 4 MediaTek

5. November 2023 doc.: IEEE 802.11-23/xxxxr0 Transition step 1 - STA sends ML reconfig to MLD1 to set up link(s) with MLD2. This step can be - STA initiated - MLD triggered Submission Slide 5 MediaTek

6. November 2023 doc.: IEEE 802.11-23/xxxxr0 Transition Step 2a Router Ethernet Switch 1. MLD Roaming Indication AP MLD1 AP MLD2 2.4GHz 5GHz 5GHz 2.4GHz STA MLD - STA initiates roaming by sending a Roaming Indication frame to MLD1 Submission Slide 6 MediaTek

7. November 2023 doc.: IEEE 802.11-23/xxxxr0 Transition Step 2b Router Ethernet Switch UL Data UL Ethernet frame 2a. Flush UL Data frames received from STA MLD 2b. V-MLD coordination (context tr) AP MLD1 AP MLD2 2.4GHz 5GHz 5GHz 2.4GHz STA MLD MLD1 flushes UL data to DS Submission Slide 7 MediaTek

8. November 2023 doc.: IEEE 802.11-23/xxxxr0 Transition Step 3 STA Requests DS Map Update to MLD2 (DS stops sending DL data through MLD1) STA sending UL data (if any) through MLD2 does DS Map update automatically STA may request MLD2 to buffer its DL data until ready to receive Router Ethernet Switch DS Mapping update DS Map update Req AP MLD1 AP MLD2 2.4GHz 5GHz 5GHz 2.4GHz STA MLD DL data for STA MLD Submission Slide 8 MediaTek

9. November 2023 doc.: IEEE 802.11-23/xxxxr0 During transition Depending on STA capabilities, DL data is retrieved by the STA either sequentially or in parallel from the MLDs If sequential, STA requests MLD2 to buffer DL data for STA until STA receives all DL from MLD1 Router DL Data Ethernet Switch DL Ethernet frame UL Data UL Ethernet frame MLD2 to buffer DL Data frames until STA ready to receive DL from MLD2 AP MLD1 AP MLD2 2.4GHz 5GHz 5GHz 2.4GHz STA MLD DL Data UL Data Submission Slide 9 MediaTek

10. November 2023 doc.: IEEE 802.11-23/xxxxr0 Transition Step 4a - STA releases its links with MLD1 - Requests the DL data from MLD2 Submission Slide 10 MediaTek

11. November 2023 doc.: IEEE 802.11-23/xxxxr0 Transition Step 4b STA request for DL Data (if buffering was requested) Router Ethernet Switch AP MLD1 AP MLD2 2.4GHz 5GHz 5GHz 2.4GHz STA MLD UL/DL data with MLD2 Submission Slide 11 MediaTek

12. November 2023 doc.: IEEE 802.11-23/xxxxr0 Roaming complete Router DL Data Ethernet Switch DL Ethernet frame UL Data UL Ethernet frame P a c k STA MLD DL Data & UL DATA AP MLD1 AP MLD2 2.4GHz 5GHz 5GHz 2.4GHz Submission Slide 12 MediaTek

13. November 2023 doc.: IEEE 802.11-23/xxxxr0 What is proposed to enable this roaming scenario Define procedures which allows MLDs to indicate they belong to a V-MLD STA to indicate roaming intent and MLD buffer flush request STA to request DS Map Update STA to request DL data buffering for the roaming transition period Submission Slide 13 MediaTek

14. March 2023 doc.: IEEE 802.11-23/xxxxr0 Scenario 2. Inter V-MLD roaming DS ETH switch Data path Virtual MLD2 Virtual MLD1 Management path (proprietary) MLD1 MLD3 MLD2 STA MLD Submission Slide 14 MediaTek

15. Month Year doc.: IEEE 802.11-23/xxxxr0 Inter V-MLD roaming Inter MLD roaming from STA pov is when (V-)MLD2 MAC is different than (V-)MLD1 MAC STA uses ReAssociation Request frame instead of Reconfiguration Request This ReAssociation Request to not trigger an automatic DS mapping change - There is no common V-MLD to assist with context transfer between MLDs, but retain the Mobility Domain concept - Sequence of events same as in Intra V-MLD case, except context transfer to be done by the STA itself - STA to use an updated Fast BSS Transition procedure to transfer BA agreement (and other needed context) Submission Slide 15 John Doe, Some Company

16. November 2023 doc.: IEEE 802.11-23/xxxxr0 What is proposed to enable this roaming scenario Define an enhanced Fast BSS Transition procedure which Allows the STA to do the context transfer itself between the serving and target MLDs Does the blue box functionality from slide 7 Integrates with the procedures to be defined for the intra V-MLD roaming scenario Submission Slide 16 MediaTek

17. November 2023 doc.: IEEE 802.11-23/xxxxr0 Conclusion We propose a non-AP MLD centric roaming procedures. We prefer to minimize information sharing and interaction between AP MLDs. Spec should define minimal features to allow minimizing/eliminating packet loss during roaming Submission Slide 17 MediaTek