Re: [STDS-802-11-TGM] CID 4766 (ETSI BRAN related, Figure 17-4)
--- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
Hi Edward,
I agree with Mark Rison's review comments about CID 4766 in
https://mentor.ieee.org/802.11/dcn/19/11-19-2163-11-000m-resolutions-for-some-initial-sa-ballot-comments-on-11md-d3-0.docx
I agree with Edward Au's note to commenter.
I made two mistakes in the comment, as the figure shows, the preamble
tested in BRAN is
8 STF + 8 LTF + 4 SIGNAL + 4 Data1+ 4 Data2 = 28 microseconds, not 32
microseconds.
The second mistake was I should have referenced device testing that
several companies have undertaken, with a variety of results, the worst
of which is/was that testing has shown the some devices in use in Europe
fail to honor the duration in the SIGNAL symbol if it is the last symbol
transmitted, some devices in use in Europe only honor the duration in
the SIGNAL symbol if the Data1 and Data2 symbols are transmitted with
BPSK modulation.
The testing continued, no significant failures were found when OFDM
preambles with the 28 microseconds of information described here were used.
Best Regards,
petere
On 3/1/2020 11:29 PM, Edward Au wrote:
--- This message came from the IEEE 802.11 Task Group M Technical Reflector ---
Hi,
For CID 4766, the comment is about a discussion on Figure 17-4 of IEEE
802.11md Draft 3.0 as follows:
"Discussion in ETSI TC BRAN about Figure 17-4 shows shipping devices
need to see all of Data 1 and Data 2 to conclude they have received a
valid preamble (32 microseconds). BRAN(19)104031 slide 4 last bulleted
item. Please include the trailing edge of Data 2 symbol in Figure 17-4
so all outside 802.11 can understand the time is 32 microseconds, not
less than 32 microseconds."
The resolution proposed by the commenter is as follows:
"Please rescale Figure 17-4 to include the trailing edge of Data 2
symbol in Figure 17-4."
During the discussion of this CID in the February ad-hoc
(https://mentor.ieee.org/802.11/dcn/19/11-19-2163-11-000m-resolutions-for-some-initial-sa-ballot-comments-on-11md-d3-0.docx),
while there is a common understanding that the trailing edge of Data 2
symbol should be re-scaled, there are arguments that Figure 17-4 does
not indicate that all OFDM transmissions must be at least 32 us long.
For example, one comment as documented in 19/2163r11 is as follows:
a) Nothing in the references to F17-4 says it shows the minimum
required set of symbols
b) Even with Data 2 shown in full the structure shown only lasts 8+8+3*4 = 28 us
As per Dorothy's request, please review the current proposed
resolution of this CID as shown in 19/2163r11 and post to the email
reflector on your thought on this comment and the proposed resolution,
especially on whether the time is 32 microseconds. It is expected to
continue the discussion on this CID in one of the upcoming TGmd
teleconference calls.
Thanks and Regards,
Edward
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