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In general, it may be good to clarify that the performance you mention below is mostly for latency. For throughput there could be low congestion scenarios where non-STR is clearly beneficial
compared to having data exchange on just one link at a time. It could be argued though whether such low congestion scenarios are rare or not.
“If the AP uses RTS/CTS (which is the default configuration in most cases): non-STR ML will follow the same procedure as TDM ML.
This is because, if there is any difference between channel access times on the two links, RTS/CTS cannot be exchanged with a non-STR non-AP STA on the link which gains access later.”
From: Sindhu Verma <000011381223f2e2-dmarc-request@xxxxxxxxxxxxxxxxx>
Dear All, This email is to start a discussion on the “TDM
Multilink operation” scheme as proposed in
0659r1. The basic principle of this scheme is very similar to
the “Enhanced Multilink single radio operation” scheme proposed in 0562r2. The common principle in these contributions is
listen on one or more links but Tx/Rx of data on only 1 link at a time. Different radio + baseband architectures can be used to achieve this principle and the specific architecture is not integral to the principle. Following are the advantages of this principle which we call TDM ML:
TDM ML at a non-AP STA provides the same or similar performance as conventional non-STR ML, but at a lower cost and lower complexity at the non-AP STA.
The complexity at an AP to support a TDM ML STA is the same as what is required to support a conventional non-STR non-AP STA.
STR ML performance can be better than TDM ML. However, STR ML is not expected to be implemented in R1 for any non-AP STA in 5G/6G due to the cost and complexity involved.
Given the above, TDM ML provides a more feasible and cost effective means at a non-AP STA to achieve non-STR ML performance in 5G/6G. The equivalence of performance between TDM ML and non-STR ML at a non-AP STA can be explained intuitively as follows:
Untriggered UL: UL for non-STR ML will follow the same procedure as UL for TDM ML,
except when a non-AP gains channel access on both links at exactly the same time. The chances of the latter happening are statistically miniscule.
Triggered UL: UL for non-STR ML will follow the same procedure as UL for TDM ML, except
when the AP gains channel access on both links at exactly the same time. The chances of the latter happening are statistically miniscule. This is because the triggered UL transmissions must start at the same time, as once a non-STR non-AP starts transmitting
on one link, it cannot receive DL data or a DL trigger or perform CCA for untriggered UL on the other link.
DL: The difference between non-STR ML and TDM ML will arise only when the AP wins a
second link to transmit to a non-STR STA while it has an ongoing transmission to the same STA on another link. In this case:
If the AP uses RTS/CTS (which is the default configuration in most cases): non-STR ML will follow the same procedure as TDM ML. This is because, if there is any difference between channel
access times on the two links, RTS/CTS cannot be exchanged with a non-STR non-AP STA on the link which gains access later.
If the AP does not use RTS/CTS (as is common mostly for short transmit durations): The AP in this case can start transmitting in parallel at different times on both links to a non-STR
ML STA, but has to ensure that the AMPDUs on both links have the same end time. The short duration of AMPDUs for high bandwidths + the restriction of making the AMPDU on the second link shorter due to end alignment with the AMPDU on the first link, leads to
insignificant gain for non-STR ML. Simulations presented in 0659r1 (slides 11 and 12) also show this equivalence. Please let us know your comments. Regards, To unsubscribe from the STDS-802-11-TGBE list, click the following link:
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