doc.: ieee 802.11-10/0130r0 submission january 2010 yung-szu tu, et al., ralink tech.slide 1...

January 2010

Yung-Szu Tu, et al., Ralink Tech.

Slide 1

doc.: IEEE 802.11-10/0130r0

Submission

Proposed TGac Preamble

Date: 2010-01-20

Name Company Address Phone email Yung-Szu Tu [email protected]

Yen-Chin Liao [email protected]

Cheng-Hsuan Wu

5F., No.36, Taiyuan St., Jhubei City, Hsinchu County 302, Taiwan

+886-3-560-0868

[email protected]

Peter Loc +1-408- 807-0868 [email protected]

Tom Pare [email protected]

Kiran Uln

Ralink Technology 20833 Stevens Creek

Blvd, Suite 200., Cupertino CA 95014

+1-408-725-8070 [email protected]

Leonardo Lanante [email protected]

Yuhei Nagao [email protected]

Wahyul Amien Syafei

Kyushu Institute of Technology

Kawazu 680-4, Iizuka, JAPAN

+81-948-29-7692

[email protected]

Hiroshi Ochi [email protected]

Thet Htun Khine Radrix Corp. Kawazu 680-4, Iizuka, JAPAN

+81-948-29-7692 [email protected]

Shin Chon Park Korea Advanced Institute of Science and Technology

2201 Creation Hall, KAIST-ICC, 103-6, Munji-Dong, Yuseong-Gu, KOREA

+82-42-350-6921

[email protected]

Authors:

January 2010


Slide 2

doc.: IEEE 802.11-10/0130r0

Submission

Outline

• PPDU format• VHT-SIG• Legacy Rx state machine for VHT-SIG• VHT-LTF

– 2 options

• Conclusion and future work

January 2010


Slide 3

doc.: IEEE 802.11-10/0130r0

Submission

PPDU Format

January 2010


Slide 4

doc.: IEEE 802.11-10/0130r0

Submission

VHT PPDU Format Design Considerations

• Immediate (no symbol delay) detection• Reliable• Backward compatibility with 11a/n• Low PAPR

January 2010


Slide 5

doc.: IEEE 802.11-10/0130r0

Submission

Possible VHT PPDU Formats

• All packet types present in MM-VHT network– Support for VHT-GF is optional

HT-SIG2HT-SIG1L-SIG

DATA2DATA1L-SIG

VHT-SIGn VHT-STF VHT-LTFVHT-SIG1L-SIG

11aLegacy

11nMM

11acMM

VHT-DATA1

HT-STF HT-LTF HT-DATA1

HT-SIG2HT-SIG111nGF HT-LTF HT-DATA1

11a Legacy Packet

VHT-SIGn VHT-LTFVHT-SIG111acGF

VHT-DATA1

11n Packet Types

11ac Packet Types

L-LTFL-STF

L-LTFL-STF

HT-LTF1HT-GF-STF

L-LTFL-STF

VHT-LTF1VHT-GF-STF

January 2010


Slide 6

doc.: IEEE 802.11-10/0130r0

Submission

Phase Rotation

• 09/1174r0 [2] mentioned phase rotation over 4 sub-bands is required for low PAPR

• Our simulation result on phase rotation agrees with 09/0847r1 [3] by Leonardo et al., i.e. 1 j 1 -j

• We also found other sets of rotation that yield low PAPR

January 2010


Slide 7

doc.: IEEE 802.11-10/0130r0

Submission

VHT-SIG

January 2010


Slide 8

doc.: IEEE 802.11-10/0130r0

Submission

VHT Signal Field

• Challenges for VHT-SIG design• Immediate and Reliable detection on first symbol after L-SIG

– Minimize false detection• Backward compatibility

– With 11a/n• Efficiency

– Support enhanced features of TGac with no unnecessary fields

January 2010


Slide 9

doc.: IEEE 802.11-10/0130r0

Submission

Previously Proposed VHT Preamble Format

• Proposed Signaling scheme allows MM/GF structure identical to 11n• Alternating subcarriers get 90-degree shift

– “Orthogonal shift” compared to 0-degree and 90-degree

HT-SIG2HT-SIG1L-SIG

DATA2DATA1L-SIG11aLegacy

11nMM HT-STF HT-LTF HT-DATA1

VHT-SIGn VHT-STF VHT-LTFVHT-SIG1L-SIGVHTMM

VHT-DATA1

90 degreerotation

90 degreeAlternate

subcarriers

January 2010


Slide 10

doc.: IEEE 802.11-10/0130r0

Submission

11n HT-SIG Field detection using 90 degree BPSK

• 90 degree detector– Operate on 1st symbol following L-SIG– Detection:

• Measure FEQ output • Compare I vs Q energy levels: High Q energy HT packet• Legacy data symbols: low Q, or equal I and Q components

-1 +1

L-SIG

-j

+j

HT-SIG

Q

DATA(QPSK e.g.)

I

Q

I

Q

I

January 2010


Slide 11

doc.: IEEE 802.11-10/0130r0

Submission

Previously Proposed VHT-SIG modified 90 degree BPSK

• Alternate 0/90 degree BPSK symbols on odd/even subcarriers

• Will not be detected as 11n HT-SIG field

-1 +1

VHT-SIG

-j

+jQ

I

Q

I

OddSC’s

EvenSC’s

January 2010


Slide 12

doc.: IEEE 802.11-10/0130r0

Submission

Previously Proposed VHT-SIG MM Detection Scheme

xHT-SIGn xHT STF xHT-LTFxHT-SIG1L-SIG xHT-DATA1

2 2

1

Nsc

i ii

I Q

2 2 2 2

, ,

Nsc Nsc

i i k ki even k odd

I Q I Q

11n Detection

11ac Detection

nS

acS

Metric Data Symbol 11a L-SIG 11n HT-SIG 11ac VHT-SIG

11n 0 S -S 0

11ac 0 0 0 -S

January 2010


Slide 13

doc.: IEEE 802.11-10/0130r0

Submission

Newly Proposed VHT-SIG with +45/+135 degree BPSK

• Rotate VHT BPSK symbols +45 degrees– Alternate +45/-45 (+135) degree BPSK symbols on odd/even

subcarriers– Will not be detected as 11n HT-SIG field

• Even just a few subcarriers would detect equal I/Q energy

VHT-SIG

(1-j)

(-1+j)Q

I

Q

I

OddSC’s

EvenSC’s

(1+j)

(-1-j)

45.0°

45.0°

January 2010


Slide 14

doc.: IEEE 802.11-10/0130r0

Submission

Newly Proposed VHT-SIG MM Detection with Rotation

xHT-SIGn xHT STF xHT-LTFxHT-SIG1L-SIG xHT-DATA1

2 2

1

Nsc

i ii

I Q

2 2 2 2

, ,

Nsc Nsc

i i k ki even k odd

I Q I Q

11n Detection

VHT Detection

nS

acS-45-deg rotation

4je

• Detection metrics unchanged• More robust 11n spoofing

• All subcarriers appear as QPSK to 11n detector (i.e., data symbol)• VHT detection on de-rotated symbols

– Recovers original orthogonal 90-degree BPSK shift

January 2010


Slide 15

doc.: IEEE 802.11-10/0130r0

Submission

Orthogonal shift provides better backward compatibility

• Both VHT-SIG1, 2 appear as QPSK data to 11n detector– All subcarriers contain both I/Q energy– Both VHT-SIG fields appear as data symbols under 11n detection

• Delayed-90 shift could result in “false positive” 11n detection – Certain 11n implementations could trigger off either HT-SIG field

to declare 11n packet• More efficient SIG field design

– Open possibility to QPSK VHT-SIG2– No need for VHT-SIG3– Or, pack twice as much VHT descriptor info. by employing higher-

order Modulation and Code Rate

January 2010


Slide 16

doc.: IEEE 802.11-10/0130r0

Submission

Detection Timeline with and without Rotation of VHT-SIG1

• With VHT-SIG1 rotation, 11ac devices can recognize 11ac packets at FEQ output

immediately after VHT-SIG1

VHT-SIG3 VHT-STF VHT-LTFVHT-SIG1L-SIG11acMM

VHT-DATA1L-LTFL-STF

No rotation of

VHT-SIG1

VHT-SIG2

with rotation of

VHT-SIG1

11ac detectedStart VHT processing

11ac detectedStart VHT processing

January 2010


Slide 17

doc.: IEEE 802.11-10/0130r0

Submission

Straightforward Extension to Greenfield

• Allows highly efficient all-GF operation– Eventual phase-out of 11a devices: all 11n/ac network

HT-SIG2HT-SIG1L-SIG11nMM HT-STF HT-LTF HT-

DATA1

HT-SIG2HT-SIG111nGF HT-STF HT-LTF HT-

DATA1

VHT-SIGn VHT-STF VHT-LTFVHT-SIG1NewVHTGF

VHT-DATA1

Orthogonal Shift0-degree shift 90-degree shiftSHIFT DEFINITIIONS

January 2010


Slide 18

doc.: IEEE 802.11-10/0130r0

Submission

Rx State Machine

January 2010


Slide 19

doc.: IEEE 802.11-10/0130r0

Submission

11a PLCP Rx State Machine

January 2010


Slide 20

doc.: IEEE 802.11-10/0130r0

Submission

11n PLCP Rx State Machine

January 2010


Slide 21

doc.: IEEE 802.11-10/0130r0

Submission

Legacy Rx State Machine

• 11a devices can recognize L-SIG but not the following VHT-SIG, so it will wait LENGTH indicated in L-SIG

• 11n devices cannot recognize VHT-SIG, so three ways at “RX HT-SIG” are all possible1. Carrier lost2. HT-SIG, but CRC will fail3. Claimed as 11a/g, but can’t be decoded wait LENGTH– 1 and 2 will return to IDLE state when the PPDU is over, just as

invalid and corrupted 11n PPDU

All legacy devices are not affected

January 2010


Slide 22

doc.: IEEE 802.11-10/0130r0

Submission

Summary

• Use “orthogonal shift” to signal new VHT packet format– Take advantage of OFDM property to expand signaling space– More robust detection VHT-SIG1,2 appear as QPSK to 11n detector

• More efficient SIG field design– Open possibility to QPSK VHT-SIG2

• No need for VHT-SIG3 • Additional user data

• GF compatibility– Extends gracefully to VHT-GF operation

January 2010


Slide 23

doc.: IEEE 802.11-10/0130r0

Submission

VHT-LTF

January 2010


Slide 24

doc.: IEEE 802.11-10/0130r0

Submission

Channel Estimation by P Matrix

28:28

28:28

28:28

28:28

Tx1= * 1 1 1 1

Tx2= * 1 1 1 1

Tx3= * 1 1 1 1

Tx4= * 1 1 1 1

HTLTF

HTLTF

HTLTF

HTLTF

CSD Q IFFT

January 2010


Slide 25

doc.: IEEE 802.11-10/0130r0

Submission

Generation of the New P matrixfor More Tx Antenna

• Requirement of generating P– P must be a unitary matrix ( )– The element of P must be +1 or -1

• Ensures the Tx and Rx power the same as payload. – The 2x2 P must be a sub-matrix of 3x3 P

1 TP P

January 2010


Slide 26

doc.: IEEE 802.11-10/0130r0

Submission

Compatible with 11n P Matrix• The size of the P matrix must be even.• There exists no 6x6 P matrix which is also compatible with the 11n P

matrix(4x4)

1 -1 1 1 1 -1 1 1 1 1 -1 1 1 1 -1 1 1 1 1 -1 1 1 1 -1-1 1 1 1 -1 1 1 1 1 1 1 1 -1 -1 -1 -1 1 -1 1 -1 -1 1 -1 1 1 1 -1 -1 -1 -1 1 1 1 -1 -1 1 -1 1 1 -1

88

87

86

85

44

43

22

11

NDLTFNSTS

January 2010


Slide 27

doc.: IEEE 802.11-10/0130r0

Submission

MIMO Channel Estimation by FDM LTF (1)

LTF1

LTF2

LTF6

IFFT

January 2010


Slide 28

doc.: IEEE 802.11-10/0130r0

Submission

MIMO Channel Estimation by FDM LTF (2)

LTF1 LTF2 LTF3 LTF4 LTF5 LTF6 Data






Tx1

Tx6

Tx2

Tx3

Tx4

Tx5

January 2010


Slide 29

doc.: IEEE 802.11-10/0130r0

Submission

Mean Square Error for 6x6

• Channel B • Channel D

January 2010


Slide 30

doc.: IEEE 802.11-10/0130r0

Submission



January 2010


Slide 31

doc.: IEEE 802.11-10/0130r0

Submission



January 2010


Slide 32

doc.: IEEE 802.11-10/0130r0

Submission

Comparison

• FDM is more efficiency– For FDM, No. of symbols = No. of streams– For P matrix, No. of symbols = 8 for 5~7 streams– At the expense of worse MSE

• P matrix method is compatible with 11n and has lower MSE

January 2010


Slide 33

doc.: IEEE 802.11-10/0130r0

Submission

Conclusion and Future Work

• VHT-SIG is refined with extra 45 degree rotation, compared with 09/1258r0

• VHT-SIG is backward compatible with legacy Rx state machine

• Two options of VHT-LTF are proposed• Future work:

– Simulation of VHT-SIG– More PHY designs

January 2010


Slide 34

doc.: IEEE 802.11-10/0130r0

Submission

References

• [1] Yug-Szu Tu, et. al., Proposal for TGac VHT Format , IEEE 802.11-09/1258r0, Nov. 19, 2009

• [2] Hongyuan Zhang , et. al., 802.11ac Preamble, IEEE 802.11-10/0070r0, Jan. 19, 2010

• [3] Leonardo Lanante , et. al., IEEE802.11ac Preamble with Legacy 802.11a/n Backward Compatibility, IEEE 802.11-09/0847r1, Nov. 16, 2009

doc.: ieee 802.11-10/0130r0 submission january 2010 yung-szu tu, et al., ralink tech.slide 1...

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