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Hi Minyoung, Thanks for your questions, please see my response below in-line. Regards, Yunbo 发件人: Minyoung Park [mailto:mpark.ieee@xxxxxxxxx]
Hello Yunbo, As I commented during the call, you are not doing apple to apple comparison. A NSTR MLD has two fully capable radios (two independent PHY/MAC blocks) whereas a single radio non-AP MLD operating in EMLSR has one fully
capable radio. The NSTR MLD is close to double the complexity/cost of the non-AP MLD that has the EMLSR capability. The complexity/cost has to be considered in the comparison. [Yunbo] The performance is much easier to compare because it has clear measurement criteria, that is an important reason we show performance in the presentation.
For complexity, it related to too much implementation issues, it is hard to compare. I think it may reasonable to say NSTR MLD close to double the cost of MLSR, but I don’t know how to compare with EMLSR. Because EMLSR has a full radio and a “half radio”,
so it can receive initial control simultaneously in two links. We don’t know what’s the complexity and cost of this “half radio”. Maybe you or some RF/PHY expert can give a detailed explain about how to implement this “half radio”, and compare it with NSTR
MLD. For now, I don’t think it is reasonable to say that “The NSTR MLD is close to double the complexity/cost of the non-AP MLD that has the EMLSR capability”. Another observation is that a NSTR non-AP MLD with two 1x1 radios is actually less spectral efficient than 2x2 non-AP MLD in EMLSR mode since the NSTR non-AP MLD is using two 80 MHz links with 1ss on each link whereas
the non-AP MLD in EMLSR mode is using one 80 MHz link with 2ss. For a busy network environment with many OBSSs that are not synchronized on both links (i.e. busy/idle are not synchronized on both links), this becomes a bigger problem to the NSTR non-AP MLD
since most of time the two links are not idle at the same time and only 1ss can be used on one idle link whereas for the non-AP MLD in EMLSR mode it can still use 2ss on one idle link. [Yunbo] It is true for SU and large packet transmission. For small packet transmission. It is not a big difference between single or two streams transmission. If
MU-MIMO is used, there will be no difference, because it can aggregate more STAs to reach the same total number spatial streams. Considering the initial control overhead, the performance will worse than NSTR. I also couldn't understand clearly why delay results are so high. There will be many cases where a STA can sync to the medium by receiving a frame from its own BSS or OBSS, by transmitting an RTS based on the current
11be spec, perform CCA if a STA is not doing 2ss tx, soliciting uplink traffic with a trigger frame, etc. [Yunbo] Base on my understanding, for low traffic load scenarios, the initial control and switch delay are the main reasons to introduce a large delay. For middle
load scenario, the load of EMLSR will be larger than NSTR, because initial control before each transmission will occupy a significant portion of airtime, so it increase the load of EMLSR, and furtherly increase the collision rate during the contention.
Regards, Minyoung On Wed, Mar 23, 2022 at 9:48 AM Liyunbo <00001846a2e5e0c1-dmarc-request@xxxxxxxxxxxxxxxxx> wrote:
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