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| --- This message came from the IEEE 802.11 Working Group Reflector ---
Hi, Osama, My apologies that this reply took so long – I seem to have missed your e-mail, until now. My response: I don’t see any response on my comment (1)(a). I reiterate that if the new group will make changes to the MAC, I think making those new behaviors unique/specific to only some bands is likely unnecessary, and
likely awkward. My assumption is that any such changes would have some sort of backward compatibility support (only used if a capability bit is indicated, and so forth), so I don’t know why the changes can’t apply to all bands. I would prefer not to put
any further language in the MAC clauses that is tied to specific PHYs (or bands). On my comment (1)(b): I would note that the PAR says that the scope is for modifications of PHY(s), not for creation of a new PHY. If a new PHY is intended, the PAR should be corrected to state that. Assuming that is the case (that a new PHY will be created), I presume this is being envisioned to become “the popular PHY” in some future time (like 11ac was, compared to 11n, and 11n was, compared to 11a/g,
etc.) If that is the case, then I think having an 11af PHY which is almost identical to the 11ac PHY (and thus can leverage lots of implementation work), but have the 11af band not be able to do the same thing for the HEW PHY is unnecessarily limiting, and
actually creates complexity for implementations to keep the new functions isolated. I admit, I’m not a PHY implementer/expert, so perhaps those in the HEW room have a better understanding of this than I do, but it seems an intuitive concept to me. Comment (2)(a): Given the way this PAR is written, I don’t see any implication that the 11n/11ac channel models would be applied here, in terms of mobility. Leaving the whole concept of indoor speeds or mobility
silent, leaves me with no understanding of the intent at all. This is then related to (2)(b), which is asking if the group is planning to discuss mobility (in which I would include BSS transition) at all. I gather from your response that it is not a consideration. I think
that may be missing an opportunity – but I also understand completely if the group does not want to tackle an even broader scope (and mobility concerns are a non-trivial topic, I am well aware
J).
I agree that I read “mobility” (and BSS transition) into the statement about outdoor speed, when it is actually not mentioned. I now understand that this bullet was meant only to refer to channel models that
can handle devices in motion. I think it would help be clear if the bullet was clarified that this applies to the intended channel modeling. Bottom line: (2)(a) and (2)(b) result in simple, editorial changes to make this clear, I think. (1)(a) and (1)(b) seem more fundamental, making the true nature of the work described by the PAR completely unclear
to me, and would request the language be changed to sort this out (and then the implications on the band limitations be reconsidered in that light). Thanks. Mark From: Osama AboulMagd [mailto:Osama.AboulMagd@xxxxxxxxxx]
Hi Mark, Thanks for your comments. Please find my response inline. I hope other people will jump in and offer their views. Regards; Osama. From: *** IEEE stds-802-11 List *** [mailto:STDS-802-11@xxxxxxxx]
On Behalf Of Hamilton, Mark --- This message came from the IEEE 802.11 Working Group Reflector ---
HEW folks, You may have been there, or heard about, my questions during the closing plenary in Los Angeles about the draft PAR being put forward by the HEW SG. At the time, Bruce clarified that the agenda item at the time was to get the draft PAR
into the process for review, and that my questions would be better asked during the review. So, I am putting them forward here, now, instead of taking the time during that plenary session, in an interest in getting it clarified before/at the Beijing meeting. 1.
I am wondering about the band restrictions. To quote from the draft PAR: “This amendment defines operations in frequency bands between 1 GHz and 6 GHz.” It was confirmed at the plenary that the intent is to not cover the TV white space
bands. These leads me to two questions:
a.
The PAR talks about making changes to both/either MAC and PHY. If the MAC is changed, how are those changed envisioned to be band-specific? This seems to me to be some combination of cumbersome in the text (a lot of added “If such-and-such
MIB attribute is true” language around all of the changes), and complex and unnecessary restriction in implementations to only use the new features if the specified bands are in use.
b.
If there are changes to the PHY, for example the 11ac PHY (which is specifically called out as focus for the improvements, per the PAR), will those changes not be reflected in the 11af PHY (which is currently an intentional “copy” of
the 11ac PHY)? This again seems unnecessary and an unfortunate complication for implementations. [osama] I believe the intention of the group members is to produce a new PHY clause rather than tweaking clause 22. I think the PAR is clear in saying that the improvement will be relative to 11ac and 11n under
the same scenarios, rather than saying introduce changes to 11ac PHY. For example if some of the technologies discussed in the SG, e.g. UL MU MIMO, are introduced in HEW, do you think they should be added to 11af? It seems to me that 11af TG did a good job
producing clause 23 (a modified version of clause 22), but it is not clear the intention was to track all the changes in future amendments. It will be a heavy burden on future work. I also would like to point out that initially 11af was proposing to use 11n
PHY (draft D1.0), not 11ac, which supports my assertion that the intention wasn’t to track changes to be introduced by future amendments. [osama] The focus of the group (as well as the motion to start the SG) is on the 2.4 and 5 GHz bands where most (if not all) of WLAN deployments are. Issues related to the band selection was discussed in the
SG during the January meeting. Some favored to be specific about the bands of interest and state 2.4 and 5 GHz explicitly in the PAR scope. Others preferred to keep the door open to if and when new bands become available. Hence the language in the PAR. There
was no intention to go back and modify everything that was done before. 2.
I also wonder about the language discussing mobility.
a.
The PAR has this bullet: “Outdoor operation is limited to stationary and pedestrian speeds.” (In the section 5.2.b extended comments at the bottom – which is an excellent addition, by the way – this made the PAR one of the most clear
about its intent in recent memory!) There seems to be no matching discussion of indoor operation while mobile. [osama] My understanding is we needed to qualify the outdoor speeds only. Indoor speeds are probably straightforward and are not different from what is in 11n and 11ac channel models.
b.
Between the above sentence, and the specific mention of mobile devices as a target stakeholder, I am assuming that some aspect of mobility is being considered as part of the problem set of the scope. Although, I don’t see any other
discussion that clarifies this. (As many of you know, I am very interested in mobility performance, and would like to understand if there is overlap or other relationship to the proposed work.) If mobility factors are to be considered, I believe more language
describing that is needed in the PAR. If mobility is not going to be considered, I don’t understand the discussion of (outdoor) mobility speeds, and suggest that bullet be changed to say that mobility is not being considered. [osama] I believe the qualification of the outdoor speeds was mainly introduced to affect the channel models the group is developing. While not an expert in mobility, I am sure that mobility means more than just
channel models. As far as I remember there hasn’t been discussion in the SG on supporting mobility (anyone can correct me if I am wrong). I think the bullet is appropriate the way it is to serve its intended purpose. I also note that the word “mobility” wasn’t
mentioned anywhere in the PAR. Thanks for any clarification on these items. Mark Hamilton _______________________________________________________________________________
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