1. DMG Base MCS and Length Supplementary Slides
May 2016
doc.: IEEE /0707r0
May 2016
DMG Base MCS and Length Supplementary Slides
Date:
Authors:
Hiroyuki Motozuka, Panasonic
Hiroyuki Motozuka, Panasonic

2. May 2016
doc.: IEEE /0707r0
May 2016
Abstract
The current text in draft D5.4 of REVmc defines the Base MCS and Length field in the PHY SC header for extended MCS.
But the formula for Length field value causes duration calculation error for some Ns (number of PSDU octets.)
The submission 11-16/0670r5 proposes modified text and formulae to fix it.
This submission includes supplementary slides for /0670r5.
Hiroyuki Motozuka, Panasonic
Hiroyuki Motozuka, Panasonic

3. Duration calculation error
May 2016
doc.: IEEE /0707r0
May 2016
Duration calculation error
Base MCS and Length field value in SC Header should be set so that the duration calculated from Header equals to the actual duration.
The formula in D5.4 causes duration errors for some Ns (numbers of octets.)
Potential risks to fairness and interoperability on IFS/backoff procedures
Extended MCS capable STA sees this duration
example)
Actual MCS, PPDU octets
MCS9.1, N = 70
actual PPDU duration = 3.09 usec
Header values
Base MCS6, Length=40
(according to the formula in D5.4)
duration calculated from Header = 2.80 usec
-0.29 usec
Extended MCS non-capable STA sees this duration
Observed duration errors -0.29us ~ +0.58us
Hiroyuki Motozuka, Panasonic
Hiroyuki Motozuka, Panasonic

4. Proposed Modification – Base MCS
May 2016
doc.: IEEE /0707r0
May 2016
Proposed Modification – Base MCS
Base MCSs (6 to 12) are mapped to Extended MCSs in natural order.
Extended MCS
value in Base MCS field
9.1 6
12.1 7
12.2 8
12.3 9
12.4 10
12.5 11
12.6 12
Hiroyuki Motozuka, Panasonic
Hiroyuki Motozuka, Panasonic

5. Proposed Modification - Length
May 2016
doc.: IEEE /0707r0
May 2016
Proposed Modification - Length
Proposed Length formula is based on NBLKS (number of symbol blocks)
Avoid errors caused by number of parity bits
set according to given duration
used for recovery of number of data octets (N) at receivers
MCS
Base_Length1
Base_Length2
value in Base MCS field
9.1 6
Hiroyuki Motozuka, Panasonic
Hiroyuki Motozuka, Panasonic

6. Proposed Modification – Length(cont’d)
May 2016
doc.: IEEE /0707r0
May 2016
Proposed Modification – Length(cont’d)
MCS
Base_Length1
Base_Length2
value in Base MCS field
12.1 7
12.2 8
12.3 9
12.4 10
12.5 11
12.6 12
Hiroyuki Motozuka, Panasonic
Hiroyuki Motozuka, Panasonic

7. Proposed Modification - SI
May 2016
doc.: IEEE /0707r0
May 2016
Proposed Modification - SI
Similar to 11-16/0220r3, two bits out of SI field are used for recovery of the actual number of octets at receiver STA.
Formula is as follows: =
Hiroyuki Motozuka, Panasonic
Hiroyuki Motozuka, Panasonic

8. Observed duration error 0 usec
May 2016
doc.: IEEE /0707r0
May 2016
Verification
Duration error is eliminated with proposed formula.
Recovery of the number of data octets works.
We verified it throughout: MCS {9.1, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6} x Number of octets:
example)
Actual MCS, PPDU octets
MCS9.1, N = 70
actual PPDU duration = 3.09 usec
Header values
Base MCS6, Length=68
duration calculated from Header = 3.09 usec
Observed duration error 0 usec
Hiroyuki Motozuka, Panasonic
Hiroyuki Motozuka, Panasonic

9. References [1] Draft P802.11REVmc_D5.3
May 2016
doc.: IEEE /0707r0
May 2016
References
[1] Draft P802.11REVmc_D5.3
[2] 11-16/0220r3 Clause 20 SC MCS Extension
[3] 11-16/0233r0 Additional SC MCSs in clause 20 (DMG PHY)
[4] 11-16/0670r5 Base MCS and Length Calculation for Extended MCS Set
Hiroyuki Motozuka, Panasonic
Hiroyuki Motozuka, Panasonic