Slide1
Further discussion for 11be preamble
Date:2019-09-16
Authors:
Dongguk Lim, LG Electronics
Sept. 2019
Introduction
11be preamble isunder discussion.In [1 ~ 5], following issues were introduced and discussed.Backward compatibility and coexistenceIncluding of L-preamble ( L-STF , L-LTF and L-SIG ) in 11be preamblePacket classificationIndication using the PHY identifier (i.e., information bits) / RL-SIG/ signature sequence.Range extensionRL-SIG can be used to support the coverage extension such as 11ax.Contents and configuration of SIG fieldInthis contribution, we investigate how to differentiate the received PPDU when RL-SIG is assumed in 11be PPDU and take a look at the consideration for configuration of 11be SIG field to support the auto-detection.
Sept. 2019
Dongguk Lim, LG Electronics
Slide2
Recap : 11be preamble
As shown in [3], 11be PPDU can be composed as followsFor coexistence with legacy devices, L-Preamble should be included in 11be PPDUs.By using the L-preamble in 11be PPDU, it can prevent thecollision with legacydevices on the channel during 11be transmission.Inaddition,by including the RL-SIG inthe 11bePPDU, we can expect the followings.It enables to support the comparable coverage with 11ax.Itcan guarantee reliable transmission when small RU size is used for transmission.
Sept. 2019
Dongguk Lim, LG Electronics
Slide3
L-SIG
EHT-SIG
L-STF
L-LTF
RL-SIG
…
RL-SIG
Assuming RL-SIG is included in 11be PPDU, 11be devices can progress the auto-detection which has been adopted in 11ax.Auto-detection with RL-SIGFirst step : Repetition checkAs introduced in [6], multiple ways in frequency domain can be consideredSecond step : L-SIG contents checkParity check = OKRate check = 6MbpsLength field (mod 3) = ?By MRC of L-SIG and RL-SIG, enable range extension.
Sept. 2019
Dongguk Lim, LG Electronics
Slide4
Repetition check
MRC & Contents check
Legacydetection(11n/11ac/11a)
Received PPDU
N
N
Y
11ax or11be
Auto-detection (1/3)
By using the symbol modulated with BPSK after L-SIG and RL-SIG,11be devices candistinguish whetherreceivedPPDU is11be format or11n/11acformat.RL-SIG in 11be PPDU does not impact the detection of11n/11ac PPDU.For the distinction of PPDU between 11ax and 11be, we can consider the following options for length field of L-SIG.Option 1: length mod 3 != 0Option 2: length mod 3 = 0
Sept. 2019
Dongguk Lim, LG Electronics
Slide5
Auto-detection(2/3)
Option1Due to using of equal RL-SIG with11ax, itrequires the additional method such as PHY identifier(or fixed information bits)todifferentiate the 11be PPDU.itmay be included in symbol followstheRL-SIG.For example, it can be included in EHT-SIG fieldsSo, 11be devices can differentiate whether received PPDU is11be PPDU or not after decoding of symbols that include the PHY identifier (or fixed information bits).Itisnot easy toidentifyPPDU formatsearly.On the other hands, 11ax devices always treat the 11be PPDU as an 11ax PPDU and they will try to keep decoding subsequent fields (i.e., HE-SIG).11ax devices can wait for duration which is indicated in length fieldafterthe fail of validation check for HE-SIGA.
Sept. 2019
Dongguk Lim, LG Electronics
Slide6
L-SIG
EHT-SIG
L-STF
L-LTF
RL-SIG
…
Length mod 3 != 0
Auto-detection(3/3)
Option2Both 11ax devices and 11be devices can easily decide that it is not an 11ax PPDU by using the value of the length field.After checking the length field, 11ax jumps back to the legacy state machine. i.e., 11a/11n/11ac, if length mod 3 is zero.And, we can further identify 11be PPDU from 11ba PPDU. (ifneeded)By using another repetition check, 11be can distinguish whether the 11be or 11ba.Performing of repetition check with RL-SIG and one symbol after RL-SIG.
Sept. 2019
Dongguk Lim, LG Electronics
Slide7
L-SIG
EHT-SIG
L-STF
L-LTF
RL-SIG
…
Length mod 3 = 0
Comparison
Sept. 2019
Dongguk Lim, LG Electronics
Slide8
* :assuming proper design on SIG fields
Consideration for EHT SIG
To use the PHY identifier for the packet detection, it should be indicated asearlyas possible.However, generally, the SIG fields(ex., VHT-SIG, HE-SIGA) are configured with two OFDM symbols.The number of symbol for 11be SIG field may be larger than two.So, after finishing of decoding of two symbols if EHT-SIG consists of two OFDM symbols, we can confirm the PHY identifier for the indication of PPDU format.It can cause the late detection.
Sept. 2019
Dongguk Lim, LG Electronics
Slide9
L-SIG
EHT-SIG
L-STF
L-LTF
RL-SIG
Time
EHT-SIG
…
2 symbol
11bedetected
Configuration of SIG field
For the early indication and reasonable timing, SIG field can be composed of two parts.The first part(e.g., SIG1) can consistof one symbol containing26data bits.As contents for 26 data bits, PHY identifier, CRC, tail bit and other contents can be included in this part.CRC or Tail bits may be omitted.The second part(e.g.,SIG2) can consist of two or more symbols.The second part also includes the common control information , CRC and tail bit for data bits.Each part shall be encoded at the rate, R=1/2, be interleaved, be mapped to a BPSK constellation, separately.
Sept. 2019
Dongguk Lim, LG Electronics
Slide10
L-SIG
EHT-SIG1
L-STF
L-LTF
RL-SIG
EHT-SIG2
…
1 symbol
11bedetected
2 symbol or more
Summary
For the coexistence with legacy devices (i.e., 11a, 11n, 11ac, and 11ax), 11be PPDU should include the legacy preamble (i.e., L-STF, L-LTF and L-SIG).We take a look at the auto-detection method when RL-SIG is included in 11be PPDU.RL-SIG does not impact to auto-detection of legacy devices.For the distinction between PPDUs, the value of length field in L-SIG , as well as PHY identifier, can be considered.The PHY identifier can provide scalability to differentiate the nextwi-fi, but more time may be required for packet classification.For the early indication of PHY identifier and reasonable timing for detection, we can consider the EHT-SIG field that can be composed of two parts.First part canconsist of one symbol including the identifier.The second part can consist of two or more symbols.
Sept. 2019
Dongguk Lim, LG Electronics
Slide11
SP1
Do you agree that 11be PPDU shall include the legacy preamble (i.e., L-STF ,L-LTF and L-SIG) for coexistence with legacy PPDUs(i.e., 11a,11n,11ac,11ax)?
Sept. 2019
Dongguk Lim, LG Electronics
Slide12
SP2
Do you agree that the preamble of 11be PPDU includes repeated L-SIG after L-SIG?
Sept. 2019
Dongguk Lim, LG Electronics
Slide13
SP3
Which option do you prefer to classify the 11be PPDU from other PPDU?Option 1 : described in slide 6RL-SIG including the length field set to mod3 != 0Bit information for 11be packet indicationOption 2 :described in slide 7RL-SIGincluding the length field set to mod3=0Two repetition check (if classification with 11be is needed)
Sept. 2019
Dongguk Lim, LG Electronics
Slide14
SP4
Do you agree that thePHY identifier(or information bits)indicating the PPDU type(e.g., 11be and next ) is included in SIG field of 11be PPDU?
Sept. 2019
Dongguk Lim, LG Electronics
Slide15
Reference
[1] IEEE802.11-19/1021r1, PreambleDesign Harmonization[2] IEEE802.11-19/1099r1, Preamblestructure in 11be[3]IEEE802.11-19/1142r0,Discussionon the preamble for 11be[4]IEEE 802.11-19/1214r0, Preamble Design Consideration for802.11be[5]IEEE802.11-19/1085r0, high-level-eht-preamble-structure[6]IEEE802.11-15/0579r2, 802.11ax Preamble Design and Auto-detection
Sept. 2019
Dongguk Lim, LG Electronics
Slide16
Appendix
Sept. 2019
Dongguk Lim, LG Electronics
Slide17
Preamble Auto-Detection for legacy
Preamble for legacy
Sept. 2019
Dongguk Lim, LG Electronics
Slide18
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