January 2017
doc.: IEEE 802.11-17/0105r0
L-Header spoofing for EDMG SC PPDU
Date: 2017-01-16
Authors:
Name
Affiliations
Hiroyuki Motozuka Panasonic
Address
Phone email
600 Saedo-cho,
Tsuzuki-ku,
Yokohama, Japan
+81-5036868793
[email protected]
Takenori Sakamoto Panasonic
[email protected]
Gaius Wee
Panasonic
[email protected]
Huang Lei
Panasonic
[email protected]
Yutaka Murakami
Panasonic
[email protected]
Kazu Takahashi
Panasonic
[email protected]
Submission
Slide 1
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Abstract
In this presentation, the spoofing method and requirements
for EDMG SC PPDUs are discussed.
We propose to specify that the Length field in the L-Header
of an EDMG SC PPDU is set so that the spoofing error
shall be smaller than one symbol block (512*Tc) and
non-negative.
Tc is the SC Chip Time defined in 20.3.4 of [1].
Tc = 0.57 ns = 1/1.76 GHz
[1] IEEE802.11-2016
Submission
Slide 2
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Overview of spoofing and the requirements
Submission
Slide 3
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Spoofing overview
• In an EDMG PPDU, actual MCS and length are
included in the EDMG-Header-A/B [2].
• The L-Header includes spoof MCS and length so that
legacy STAs can compute the TXTIME of the EDMG
PPDU.
[2] 11-16/1358r9 Specification Framework for TGay
EDMG SC PPDU
L-STF
TXTIME
L-CEF
EDMGHeader-A
L-Header
spoof MCS, Length, TRN-Len
E-STF
E-CEF
Data
actual MCS, Length, TRN-Len
Legacy STA sees: TXTIME_spoofing – calculated by spoof MCS and Length
L-STF
Submission
L-CEF
L-Header
DMG payload
Slide 4
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Spoofing error
• The spoofing is not always perfect due to difference of
the frame formats between DMG and EDMG.
• The error is defined as follows:
Spoofing error = TXTIME_spoofing – TXTIME
• TXTIME is the duration of the EDMG PPDU
• TXTIME_spoofing is the duration calculated based on L-Header
Spoofing error
EDMG SC PPDU
TXTIME
L-STF
L-CEF
L-Header
EDMGHeader-A
E-STF
E-CEF
Data
Legacy STA sees: TXTIME_spoofing – calculated by spoof MCS and Length
L-STF
Submission
L-CEF
L-Header
DMG payload
Slide 5
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Requirement for spoofing error
• Small spoofing error is desirable to assure fairness
during backoff procedure and avoid potential issues on
interoperability.
• Since the receiver should hold the carrier sense signal
busy at least during actual TXTIME, the spoofing
error should be non-negative.
Submission
Slide 6
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Requirement for spoofing error (cont’d)
• In MU PPDU case, the receiver may calculate the
actual TXTIME by L-Header fields since the receiver
may not decode the Length field(s) which is in the
EDMG-Header-B intended for the other STAs.
• The spoofing error should be less than one symbol
block (512*Tc, 0.29us) so that the receiver can calculate
the exact number of symbol blocks using the L-Header
fields.
Submission
Slide 7
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Requirement for spoofing error (cont’d)
• We propose to specify that the spoofing error shall be
less than the duration of a symbol block (512*Tc,
0.29us) and the error shall not be negative.
Submission
Slide 8
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Analysis on the spoofing error
Submission
Slide 9
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Resolution of spoofing
• In DMG, the relationship between the Length and the
TXTIME is not linear, but step-wise, due to symbol block
structure.
• The step height depends on the modulation type.
0.58 us
0.29 us
DMG
Note: The Training Length
field is set to 0.
Submission
Slide 10
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Resolution of spoofing (cont’d)
• If MCS 6, 7, ..., or 12 is used in the L-Header of an EDMG
SC PPDU, the resolution of spoofing will be 0.29 us.
• It will be 0.58 us, if MCS 1, 2, ..., or 5 is used.
Submission
DMG MCS
(MCS in L-Header)
The step height
(Resolution of spoofing)
MCS1-5
(BPSK)
0.58 us
(2 symbol blocks, 1024 * Tc)
MCS6-12
(QPSK, 16QAM)
0.29 us
(1 symbol block, 512 * Tc)
Slide 11
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Maximum TXTIME
• The Maximum duration of an EDMG PPDU is 2ms [2].
• Only DMG PPDUs of MCS 1, 2 or 3 can reach the duration
of 2 ms. So we should set the MCS field in L-Header to 1, 2
or 3, for long EDMG PPDUs.
of DMG PPDUs
5.46
Submission
Slide 12
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Effect of Training Length field
• Use of Training Length field may provide finer resolution
of 384*Tc (512*0.75*Tc).
• Such adjustment with the Training Length field cannot be
applied to small packets, since the minimum duration of
DMG BRP packet is specified to about 10us (Nblks=18.)
• For long packets, when the MCS in L-Header is set to 1-5,
the Training Length field can be set so that the spoofing
error is reduced to less than 512*Tc.
(DMG)
BRP packet
L-STF
L-CEF
Data
L-Header
512 * Nblks
symbols
Submission
Slide 13
AGC
TRN
512 * 9.75 *TRN_LEN
symbols
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Conclusions
• In an EDMG SC PPDU, the Length field in L-Header
should be set so that the spoofing error is less than 512*Tc
and non-negative.
• It is achievable when the MCS field in L-Header is set to 6 or above,
in which the resolution of spoofing is 512*Tc.
• It is also achievable when the MCS field in L-Header is set to 5 or
below, if the packet duration is long enough to adjust spoofing error
using the Training Length field.
• We recommend to use MCS6 or above for short PPDUs, while use
MCS5 or below for long PPDUs. But we don’t specify any threshold
between short and long PPDUs.
Submission
Slide 14
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
References
[1] IEEE802.11-2016
[2] 11-16/1358r9 Specification Framework for TGay
Submission
Slide 15
Hiroyuki Motozuka, Panasonic
January 2017
doc.: IEEE 802.11-17/0105r0
Straw Poll
Do you agree to add the following to the SFD
“For an EDMG SC PPDU, the Length field in the L-Header
is set so that the spoofing error shall be smaller than one
symbol block (512*Tc) and non-negative, where
Spoofing error =
(TXTIME calculated based on L-Header) – (TXTIME)
”
Submission
Slide 16
Hiroyuki Motozuka, Panasonic