Considerations on Multi-Link Operation in IEEE 802.11-19/1181r1
Explore the technical aspects of multi-link operation in IEEE 802.11-19/1181r1 for enhanced throughput and reduced latency, covering channel access methods, reliable data transfer, and entity configurations. Learn about transmission procedures, including independent and simultaneous transmissions across multiple links.
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July 2019 doc.: IEEE 802.11-19/1181r1 Consideration on Multi-link Operation Date: 2019-07-15 Authors: Name Sunghyun Hwang Jinhyung Oh Affiliations Address ETRI Phone email shwang@etri.re.kr ETRI jinhyung@etri.re.kr Kyumin Kang ETRI kmkang@etri.re.kr Yongsu Gwak Korea National University of Transportation Yonsei Univ. onlimono@gmail.c om Hanseul Hong hhs0811@yonsei.a c.kr ronnykim@ut.ac.kr Ronny Yongho Kim Korea National University of Transportation Yongsu Gwak, Korea National University of Transportation Submission Slide 1
July 2019 doc.: IEEE 802.11-19/1181r1 Introduction According to PAR[1], the two main objectives of 802.11be are: Enhanced high peak throughput Reduced latency and jitter The multi-link operation is suggested as a key candidate feature in EHT to achieve the objectives [2], [3] For efficient multi-link operation, technical issues including the following ones should be well investigated: Channel access method in multi-link Reliable transfer (Block Ack) over multi-link In this contribution, considerations on multi-link are presented Yongsu Gwak, Korea National University of Transportation Submission Slide 2
July 2019 doc.: IEEE 802.11-19/1181r1 Entity for Multi-link Operation In case of using multiple links for one TID: Tx STA queues the data in upper MAC Tx STA allocates data to links considering channel access process: use same SN Transmission procedure performed in Lower MAC and PHY Rx STA receives the PPDU in different links, extracts MPDU, and perform aggregation The aggregation includes the reordering of SN coming from different links Yongsu Gwak, Korea National University of Transportation Submission Slide 3
July 2019 The Options of Multi-link Transmission Procedure [4] doc.: IEEE 802.11-19/1181r1 Independent transmission The transmission on multiple channel/link may proceeded different time Busy Link 1 Contention performed independently in each channel Busy Busy Link 2 Simultaneous transmission The transmission on both channel occurs on same time Busy Link 1 Contention performed in both channel and simultaneous transmission Busy Link 2 Yongsu Gwak, Korea National University of Transportation Submission Slide 4
July 2019 doc.: IEEE 802.11-19/1181r1 Channel Access for Independent Transmission For independent transmission, contention is performed independently Channel access is performed independently on each link Simultaneous Tx and Rx of multiple links on non-AP STAs may not be preferred Yongsu Gwak, Korea National University of Transportation Submission Slide 5
July 2019 doc.: IEEE 802.11-19/1181r1 Block Ack Procedure in Independent Transmission Depending on the capabilities of 802.11be devices, the BA cannot be received since link2 is still transmitting Link2 should wait while receiving BA 1 2 3 4 1 2 3 4 Link1 Link2 5 6 7 8 9 10 5 6 7 8 BA from recipient BAR Yongsu Gwak, Korea National University of Transportation Submission Slide 6
July 2019 doc.: IEEE 802.11-19/1181r1 Channel Access for Simultaneous Transmission As in the legacy wide-band operation, the simultaneous multi-link channel access may be performed with one primary link Backoff procedure in one link, ED sensing in the other link(s) Backoff end Backoff end Busy Link 1 xIFS xIFS Busy No transmission Link 2 Yongsu Gwak, Korea National University of Transportation Submission Slide 7
July 2019 Head-of-line Blocking Delay in Simultaneous Transmission doc.: IEEE 802.11-19/1181r1 Simultaneous transmission QoS data frames share sequence number (SN), one window size, and one reordering buffer over multi-link QoS data blocks which are simultaneously transmitted have to end at the same time Simultaneous Tx and Rx transmission shall not be performed Link1 1 2 3 4 5 11 12 13 14 15 Reordering Buffer Link2 6 7 8 9 10 Busy Yongsu Gwak, Korea National University of Transportation Submission Slide 8
July 2019 Head-of-line Blocking Delay in Simultaneous Transmission (cont.) doc.: IEEE 802.11-19/1181r1 HoLblocking delay QoS data frame which has SN from 6 would not go up to LLC until SN 5 frame is received. Reordering buffer in recipient would be wasted LLC 4 5 11 12 13 14 15 1 2 3 6 7 8 9 10 Busy Yongsu Gwak, Korea National University of Transportation Submission Slide 9
July 2019 doc.: IEEE 802.11-19/1181r1 Conclusion Multi-link operation can be classified into independent transmission and simultaneous transmission Channel access for simultaneous transmission should be discussed Reliable transfer with block ack mechanism in multi-link should be carefully considered Yongsu Gwak, Korea National University of Transportation Submission Slide 10
July 2019 doc.: IEEE 802.11-19/1181r1 Straw Poll 1 Do you agree that simultaneous Tx and Rx transmission shall not be performed according to the capabilities of 802.11be devices? Y/N/A Yongsu Gwak, Korea National University of Transportation Submission Slide 11
July 2019 doc.: IEEE 802.11-19/1181r1 Straw Poll 2 Do you agree that 802.11be devices shall deal with HoL blocking delay in multi-link transmission? Y/N/A Yongsu Gwak, Korea National University of Transportation Submission Slide 12
July 2019 doc.: IEEE 802.11-19/1181r1 Reference [1] 18/1231r5 EHT draft proposed PAR [2] 19/764r0 Multi-Link Aggregation: Gain Analysis [3] 19/766r1 Enhanced Multi-band/Multi-channel Operation [4] 19/0823r0 Multi-Link Operation: Design Discussion Yongsu Gwak, Korea National University of Transportation Submission Slide 13
