IEEE 802.11-24 Seamless Roaming Implementation Insights
Explore the seamless handover experiences and trials of implementing WLAN make-before-break seamless handover systems using multiple interfaces for efficient roaming in large-scale networks. Discover key considerations for MLD roaming and real-world trial results from 2003. Witness the success of seamless video transfer up to 260km/h and low packet loss in UDP TX/RX.
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May 2024 doc.: IEEE 802.11-24/0106r5 Seamless Roaming Consideration Date: 2024-05-14 Authors: Name Hitoshi Morioka Affiliations SRC Software Address Fukuoka JAPAN Phone email hmorioka@src-soft.com Submission Slide 1 Hitoshi Morioka (SRC Software)
May 2024 doc.: IEEE 802.11-24/0106r5 Abstract This presentation intends to share our experiences of seamless handover implementation on MLD. Submission Slide 2 Hitoshi Morioka (SRC Software)
May 2024 doc.: IEEE 802.11-24/0106r5 Our Experiences We have implemented WLAN make-before-break seamless handover system from 20 years ago. We would like to share our experiences. We have implemented: Use 2 wireless physical interfaces Use multiple logical interfaces on a single wireless physical interface. This implementation has a restriction that all APs have to be operated on the same channel. Use multiple logical interfaces on multiple wireless physical interfaces We used MISP (base idea of IEEE 802.11ai. please refer 11-05/0859r0) / IEEE 802.11ai for fast authentication and IP layer setup. It is not necessary but better to be used. Mobile IP for IP layer transparency Our system had to support inter-LAN handover for large scale network. Non-AP MLD used home address (a fixed IP address) instead of MLD MAC address. It is not required for roaming in a LAN. Submission Slide 3 Hitoshi Morioka (SRC Software)
May 2024 doc.: IEEE 802.11-24/0106r5 Multiple Interfaces Seamless Handover Implementation 1. A non-AP MLD communicates through AP1 with the non-AP STA1 (STA1). Non-AP STA2 (STA2) performs channel scan. The non-AP MLD finds AP2 on the non-AP STA2 and associates to it by the STA2. At this point, the non-AP MLD has two links, STA1-AP1 and STA2- AP2. The non-AP MLD still uses AP1 link on the STA1 for communication. In certain condition, the non-AP MLD decides to use STA2-AP2 link. (implementation dependent) The non-AP MLD notifies its location to the network. The non-AP MLD transmits packets to AP2 while the non-AP MLD can receive packets from both AP1 and AP2. This means the non-AP MLD can receive buffered packets from AP1. (No packet losses) In certain condition, the non-AP MLD decides to disconnect from AP1. (implementation dependent) Seamless roaming from AP1 to AP2 completes. 2. 3. AP1 AP2 4. 5. 6. 7. STA1 STA2 This system was used for V2I communication of train surveillance in some places. Non-AP MLD Submission Slide 4 Hitoshi Morioka (SRC Software)
May 2024 doc.: IEEE 802.11-24/0106r5 Our Trial in 2003 Antennas of the non-AP MLD We tested seamless handover on a test course for automobile in 2003. We installed 4 APs along the course. The distance of each AP was 300m. The non-AP MLD had 2 non-AP STAs. Realtime video transfer (DVTS) was tested. Seamless video transfer was observed up to 260km/h (speed limit of the vehicle). Non-AP MLD In this vehicle We have also tested in a laboratory. We got the results that indicated no packet losses for 1ms interval UDP TX/RX. AP Submission Slide 5 Hitoshi Morioka (SRC Software)
May 2024 doc.: IEEE 802.11-24/0106r5 MLD Roaming Consideration Key points of seamless roaming: UL is simple. Just use the preferred link. DL needs To change routing in the LAN To prevent dropping buffered packets How to change routing in the LAN Non-AP MLD can notify its location by transmitting a broadcast frame to the LAN with the MLD MAC address as the source address. (e.g Gratuitous ARP/NDP) After receiving the broadcast frame, IEEE 802.1Q compliant devices will update the routing table and forward the frames correctly. (IEEE 802.1Q-2022 8.7 The Learning Process) How to prevent buffered packets from dropping Keep link connected until it is considered that no buffered packets are remaining. Seamless roaming can be realized by existing IEEE 802.11. Just a non-AP MLD implementation issue. Submission Slide 6 Hitoshi Morioka (SRC Software)
May 2024 doc.: IEEE 802.11-24/0106r5 What should be standardized? We should consider standardization issue and implementation issue separately. Standardization is required if interactions with other STAs are required. MLD seamless roaming can be realized only by non-AP MLD implementation, without any changes on AP side. In other words, we can implement seamless roaming without any changes / violations of the existing standards. Although I am open to make a new standard for seamless roaming, I wonder if it is really required. Submission Slide 7 Hitoshi Morioka (SRC Software)
May 2024 doc.: IEEE 802.11-24/0106r5 References H. Morioka, M. Ohmori, M. Ohta, H. Mano, Development of a Seamless Handover Method Using Two Wireless LAN Devices on a Mobile Node , The 10th IPSJ DPS Workshop, 2002 (Japanese) H. Morioka, H. Mano, M. Ohmori, M. Ohta, M. Hirabaru, M. Hasegawa, M. Inoue, "Seamless Handover with Wireless LAN, Mobile IP, MISP and PDMA", The 9th International Symposium on Wireless Personal Multimedia Communications, 2006 Submission Slide 8 Hitoshi Morioka (SRC Software)
May 2024 doc.: IEEE 802.11-24/0106r5 Mobile IP vs 802.11be MLD Mobile IP Care of Address Home Address Mobile IP registration 802.11be MLD non-AP STA MAC address MLD MAC address Broadcast a frame to 802.1Q network with MLD MAC address as the source address Local address Identifier of the node Location notification to the network The table shows equivalences of mobile IP and 802.11be MLD. Our implementation that used mobile IP can be applied to 802.11be MLD. Submission Slide 9 Hitoshi Morioka (SRC Software)
