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Hi, Yunbo , Dmitry and all,
Thank you all for comments on the contribution of 11-20/0469r1 in 11be MAC conference call. As the discussion time was limited in the coherence call, I would like to have offline discussion for the joint ML EDCA backoff counter for high priority and low latency service.
Fairness
– Existing multi-channel access: 802.11 specifies the channel access on the secondary channel in PIFS after the primary channel EDCA backoff counter reaches to “0”. If the station senses the secondary channel idle in PIFS , the station will perform the multi-channel access on both primary and secondary channels. Therefore other stations (OBSS ) operating on the secondary channel may feel unfair as well.
– Joint ML EDCA backoff channel access: each of ML senses on its channel independently but shares the joint backoff counter. When the backoff counter reaches to “0”, the MLD can perform channel access on the channels being sensed as idle at the joint ML backoff counter = 0. In the extreme case that a channel is only idle at the time that the joint backoff counter is 0, the joint ML EDCA backoff procedure is same as the existing multi-channel access in term of fairness. In other case, the joint ML EDCA backoff would be more fair than the existing "CCA+PIFS" multiple channel access to OBSS stations.
Channel Access Delay
– Comparing to the existing channel access in the multiple channels, the minimum channel access delay depends on the primary channel access. Even the secondary channel is idle, the station cannot perform the channel access on the secondary channel if the primary channel is busy.
– Comparing to the independent ML channel access, the minimum channel access delay depends on the first available channel with the backoff counter = 0 among multiple links. Even when multiple channels are idle, the ML channel access delay would not be reduced significantly. It is possible to reduce the CW size of ML for the low latency service to speedup channel access, but it may not take advantage of ML to further reduce the channel access time. The joint ML EDCA hackoff is not conflict with the CW size reduction, it can further reduce the channel access time on top of CW size reduction for the time sensitive services.
– Joint ML EDCA backoff channel access delay depends on the number of idle channels at same time in addition to other common factors like CW size, channel load, etc. When only one channel is in idle, the joint ML channel access delay is the same as the independent ML channel access. But when X channels are sensed idle in the same time, the ML channel access delay will be reduced by about X times.
If there is other question or comment, I am glad to discuss them as well.
Best Regards
Yonggang Fang
ZTE (TX)
Phone 858-883-7984
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