doc.: ieee 802.11-09/0847r1 submission slide 1leonardo lanante, ochi lab, kit november 2009...

doc.: IEEE 802.11-09/0847r1

Submission Slide 1 Leonardo Lanante, Ochi Lab, KIT

November 2009

IEEE802.11ac Preamble with Legacy 802.11a/n Backward Compatibility

Date: 2009-11-18Name Affiliations Address Phone email Leonardo Lanante Kyushu Institute

of Technology Kawazu 680-4, Iizuka, JAPAN

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

Wahyul Amien Syafei

Kyushu Institute of Technology

Kawazu 680-4, Iizuka, JAPAN


Yuhei Nagao Kyushu Institute of Technology

Kawazu 680-4, Iizuka, JAPAN


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]

Hiroshi Ochi Radrix Corp. Kawazu 680-4, Iizuka, JAPAN


Authors:

doc.: IEEE 802.11-09/0847r1


November 2009

Outline

I. Introduction

II. Proposed Preamble Format (modified)

III. Preamble Waveform

IV. Compatibility Simulations (added)

V. PAPR (modified)

VI. Preamble Efficiency

VII. Conclusion

doc.: IEEE 802.11-09/0847r1


November 2009

I. IntroductionFunctional requirements for TGac.

A) System Performance1. Shall operate in 5GHz frequency band

2. At least 1Gbps at MAC SAPs utilizing 80MHz

3. At least 500Mbps for Single STA

4. Spectral efficiency at least 7.5 bps/Hz

B) Shall ensure backward compatibility with IEEE 802.11a/n.

C) Enable coexistence and spectrum sharing with IEEE 802.11a/n.

D) Compliance to PAR

Doc.IEEE802.11-09/0304r0 March 2009

doc.: IEEE 802.11-09/0847r1


November 2009

II. Proposed Preamble

• Main Features– Uses 80MHz channel and meets all functional

requirements for a VHT preamble– Three preamble modes to minimize overhead– Seamless upgrade from 802.11n preamble– Almost identical PAPR characteristics with

802.11n– Comparable Preamble Efficiency to 802.11n

doc.: IEEE 802.11-09/0847r1


November 2009

Proposed Preamble Modes

A) Mixed 11a/n Mode1. 56us duration

2. Backward compatible with 802.11a/n

B) Mixed 11n Mode1. 44us duration

2. Backward compatible with 802.11n

C) VHT Greenfield Mode1. 36us duration

2. VHT only mode

doc.: IEEE 802.11-09/0847r1


November 2009

A) Mixed 11a/n Mode Frame Format

Mixed 11a/n Mode: Backward compatible with IEEE802.11a/n

Duration=56μs *

L-STFL-STF L-LTFL-LTF L-SIGL-SIG HT-SIGHT-SIG VHT-SIGVHT-SIG VHT STFVHT STF

VHT LTF1VHT LTF1

VHTLTF4VHTLTF4

DataData DataData

8μs 8μs 4μs 8μs 8μs 4μs 4μs per LTF 4/3.6μs per Data

* 4 spatial streams

L-STFL-STF L-LTFL-LTF L-SIGL-SIG HT-SIGHT-SIG HT STFHT STF

HT LTF1HT

LTF1HT

LTF4HT

LTF4DataData DataData

8μs 8μs 4μs 8μs 4μs 4μs per LTF 4/3.6μs per Data

Duration=48μs *

802.11n Mixed Mode Preamble

A new SIG field is defined to accommodate changes in VHT while maintaining compatibility

doc.: IEEE 802.11-09/0847r1


November 2009

Subcarrier Extension for 80 MHz Channel

630-64

802.11n 40MHz case

S = subcarrier pattern for 20MHz system

-Direct Extension of subcarriers results in best compatibility with 11a/n devices-The phase shift vector [1 j ejθ jejθ] results in a high PAPR preamble for any value of θ

0-64 64-128 127

Direct Extension 80MHzDirect Extension 80MHz

ejθ(S)jSS ejθ(jS)

S jS

doc.: IEEE 802.11-09/0847r1


November 2009

Proposed Phase Rotation for 80 MHz Channel to Maintain Low PAPR

0-64 64-128 127

Proposed scheme for 80MHz

-The phases in the proposed scheme [1 j 1 –j] were chosen to give low PAPR properties-All 80MHz symbols need to be phase shifted by the same scheme either for compatibility or for PAPR reduction

0-64 64-128 127

Direct Extension 80MHzDirect Extension 80MHz

ejθ(S)jSS

S jS S -jS

ejθ(jS)

doc.: IEEE 802.11-09/0847r1


November 2009

4

j

eA 2.

jeA 12

5

.

jeA 12

11

.

jeA

Subcarriers #0-64 64-128 127

L-STF 20MHz

STS3

s8 s

s0.8s

STS4STS1 STS2 STS5 STS6 STS7 STS8 STS9 STS10

SOP AGC Frame synch. Frequency synch.

4

j

eA 2.

jeA 12

5

.

jeA 12

11

.

jeA

Subcarriers #0-64 64-128 127

L-STF 20MHz

STS3

s8 s

s0.8s



STS3

s8 s

s0.8s



Legacy – Short Training FieldL-STFL-STF L-LTF L-SIG HT-SIG VHT-SIG VHT

STFVHT LTF1

VHTLTF4

Data Data

S jS S jS

Subcarriers #

0-64 64-128 127

1 for 64

64 0

1 0 64

64

k

k

j k

k

j k

L-STF 20MHz

doc.: IEEE 802.11-09/0847r1


November 2009

Legacy - Long Training Field

A 2.

jeA 12

5

.

jeA 12

11

.

jeA

Subcarriers #0-64 64-128 127

LTF1_1

L-LTF 20MHz

LTF1_2GI

s3.2 ss3.2 ss1.6 s

LTFsGI

s3.2 ss0.8 s

…

A 2.

jeA 12

5

.

jeA 12

11

.

jeA

Subcarriers #0-64 64-128 127

LTF1_1

L-LTF 20MHz

LTF1_2GI

s3.2 ss3.2 ss1.6 s

LTFsGI

s3.2 ss0.8 s

…

S jS S jS

Subcarriers #

0-64 64-128 127

L-STF L-LTF L-SIG HT-SIG VHT-SIG VHT STF

VHT LTF1

VHTLTF4

Data Data

L-LTF 20MHz

doc.: IEEE 802.11-09/0847r1


November 2009

Legacy - SIGNAL Field

S jS S jS

Subcarriers #

0-64 64-128 127

L-SIG 20MHz

L-SIGGI

s3.2 ss0.8 s


VHT LTF1

VHTLTF4

Data Data

doc.: IEEE 802.11-09/0847r1


November 2009

VHT – SIGNAL Field

MSB

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

MCS LENGTHB

WLSB LSB MSB

VHT-SIG1

VHT-SIG2

Smoo

thin

gN

o So

undi

ngA

ggre

gatio

n

LDPC

Cod

ing

Num

ber o

f Ext

ensi

onSp

atia

l str

eam

s

CRC

C7 C0

SIGNAL TAIL

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

Res

erve

d on

e

Shor

t GI

64 options of MCS. 131072 octet of data LENGTH = 2 X 802.11n. CRC protected.

STB

C

Shor

t GI

Res

erve

d on

e

STB

C

BW LSBBWMSB

LENGTH should be increased by one bit to

maintain preamble efficiency lost with the use

of 80MHz channel


VHT LTF1

VHTLTF4

Data Data

doc.: IEEE 802.11-09/0847r1


November 2009

B) Mixed 11n Mode Frame Format

Mixed 11n Mode: Backward compatibility with IEEE802.11n

Duration=44μs *

HT-STFHT-STF HT-LTFHT-LTF HT-SIGHT-SIG VHT-SIGVHT-SIG VHT LTF2VHT LTF2

VHTLTF4VHTLTF4

DataData DataData

8μs 8μs 8μs 8μs 4μs per LTF 4/3.6μs per Data

The difference with 802.11n greenfield preamble is the

additional SIG symbol

802.11n Greenfield Preamble

Duration=36μs *

HT-STFHT-STF HT-LTF1HT-LTF1 HT-SIGHT-SIG HT LTF2HT

LTF2HT

LTF4HT

LTF4DataData DataData

8μs 8μs 8μs 4μs per LTF 4/3.6μs per Data

* 4 spatial streams

doc.: IEEE 802.11-09/0847r1


November 2009

C) VHT Greenfield Mode Frame Format

VHT Greenfield Mode: No backward compatibility with IEEE802.11a/n

Duration=36μs*

VHT-STFVHT-STF VHT-LTF1VHT-LTF1 VHT-SIGVHT-SIG VHT LTF2VHT LTF2

VHTLTF4VHTLTF4

DataData DataData

8μs 8μs 8μs 4μs per LTF 4/3.6μs per Data

-Same purpose as the 802.11n greenfield format preamble

doc.: IEEE 802.11-09/0847r1


November 2009

III. Preamble Waveform

0 4 8 16 20 24 28 32 36 40 44 48 52 56 600

0.5

1

1.5

2

2.5

sTime ( )

L-STF L-LTFVHT-STF

VHT-LTF1

VHT-LTF2

VHT-LTF3

VHT-LTF4

L-SIG

HT-SIG1

HT-SIG2

VHT-SIG1

VHT-SIG2

doc.: IEEE 802.11-09/0847r1


November 2009

IV. Co-existence Simulations

• Co-existence with 11a/n device at any 20MHz channel

80 MHz device

S jS S -jS

Proposed 80MHz format11a/n devices at any 20MHz channel can properly detect the preamble

a=legacy 802.11a/HT STS, LTS, etc…

S jS S -jS

20 MHz device

80MHz 20MHz

doc.: IEEE 802.11-09/0847r1


November 2009

IV. Co-existence Simulations

• Co-existence with 11n device at 40MHz channel

80 MHz device

S jS S -jS

Proposed 80MHz format11n devices at the UPPER 40 MHz channel expects [1 j] subcarrier rotation and has a possible compatibility issue.a=legacy 802.11a/HT STS, LTS, etc…

S jS S -jS

40 MHz device

80MHz 40MHz

40 MHz device

40MHz

doc.: IEEE 802.11-09/0847r1


November 2009

Simulation Setup

• All receivers (40MHz HT) and transmitters (80MHz VHT) have 4 antennas

• Channel Model

– AWGN

– TGn channel model ‘B’

– TGn channel model ‘D’

• Simulation tests

– Frame Synchronization/Preamble Detection

• Auto-correlation

• Cross-correlation

– Channel Estimation and SIG field Detection

doc.: IEEE 802.11-09/0847r1


November 2009

Frame Synchronization/Preamble Detection

• SISO Case cross-correlation

• Autocorrelation Based Frame Synchronization algorithm is not affected because it doesn’t use an expected reference sequence.

0 200 400 600 800 10000

0.2

0.4

0.6

0.8

1Normalized Periodic Autocorrelation

sample delays0 200 400 600 800 1000

0

0.2

0.4

0.6

0.8

1Normalized Periodic Autocorrelation

sample delays

Cross-correlation of 40Mhz 11n STS

Cross-correlation of 40Mhz 11n STS when a [1 –j] phase rotated STS symbol is received

doc.: IEEE 802.11-09/0847r1


November 2009


-Error differences in the upper and lower 40Mhz channels is indiscernible-Performance only differs whether one uses auto-correlation or cross-correlation algorithm.

0 1 2 3 4 5 6 7 8 9 1010

-3

10-2

10-1

100

AWGN Channel

Fra

me

Syn

c E

rror

Rat

e

SNR [dB]

Lower 40Mhz, auto-correlationUpper 40Mhz, auto-correlationUpper 40Mhz, cross-correlationLower 40Mhz, cross-correlation

0 1 2 3 4 5 6 7 8 9 10

10-2

10-1

100 AWGN Channel

Fra

me

Syn

c E

rror

Rat

e

SNR [dB]

Lower 40Mhz, auto-correlationUpper 40Mhz, auto-correlation

Upper 40Mhz, cross-correlationLower 40Mhz, cross-correlation

doc.: IEEE 802.11-09/0847r1


November 2009


0 1 2 3 4 5 6 7 8 9 10

10-2

10-1

100 TGN Channel B

Fra

me

Syn

c E

rror

Rat

e

SNR [dB]


Upper 40Mhz, cross-correlationLower 40Mhz, cross-correlation

0 1 2 3 4 5 6 7 8 9 10

10-2

10-1

100 TGN Channel D

Fra

me

Syn

c E

rror

Rat

e

SNR [dB]


Upper 40Mhz, cross-correlationLower 40Mhz, cross-correlation Error differences

in the upper and lower 40MHz channels is indiscernible

doc.: IEEE 802.11-09/0847r1


November 2009

Channel Estimation and SIG field detection

• Because Data symbols also undergo the same subcarrier phase shifts, SIG detection is unaffected by our proposed phase shift method

• Synchronization errors were also counted as SIG-field symbol error

Error differences in the upper and lower 40MHz channels is indiscernible

0 5 10 15

10- 2

10- 1

100

SNR [dB]

SIG

-FIE

LD S

ymbo

l Err

or R

ate

AWGN Channel

Lower40MHz, auto-correlationUpper40MHz, auto-correlationUpper40MHz, cross-correlationLower40MHz, cross-correlation

doc.: IEEE 802.11-09/0847r1


November 2009

Channel Estimation and SIG field detection

0 5 10 15

10- 2

10- 1

100

SNR [dB]

SIG

-FIE

LD S

ymbo

l Err

or R

ate

TGn Channel B

Lower40MHz, auto- correlationLower40MHz, cross- correlationUpper40MHz, auto- correlationUpper40MHz, cross- correlation

0 5 10 15

10- 2

10- 1

100

SNR [dB]

SIG

-FIE

LD S

ymbo

l Err

or R

ate

TGn Channel D

Lower40MHz, auto-correlationLower40MHz, cross-correlationUpper40MHz, auto-correlationUpper40MHz, cross-correlation

Error differences in the upper and lower 40MHz channels is indiscernible

doc.: IEEE 802.11-09/0847r1


November 2009

V. PAPR

Field Nyquist Sampled 4x oversampled

802.11n 11ac-Proposed

11ac- Direct 802.11n 11ac-Proposed

11ac- Direct

L-STF 2.09 2.24 5.1 5.25 4.47 5.82

L-LTF 3.17 3.17 6.18 6.01 5.43 6.9

HT-LTF 3.41 4.03 6.42 6.36 5.57 7.09

doc.: IEEE 802.11-09/0847r1


November 2009

VI. Preamble Efficiency

131072131072131072

230230

230 94.2696.43

95.4396.23

95.29

The preamble efficiency is defined as

3648

564436

%100

PREAMBLESYMSYM

SYMSYM

TNTNT

doc.: IEEE 802.11-09/0847r1


November 2009

Conclusion

• We have been developing an 80MHz BW WLAN preamble which has backward compatibility with IEEE802.11a/n system.

• Our simulation results confirm our proposed preamble’s backward compatibility with 802.11n 40MHz devices

• The proposed preamble has comparable efficiency compared to IEEE802.11n’s preamble.

• The proposed preamble has lower PAPR compared with IEEE802.11n’s preamble.

doc.: IEEE 802.11-09/0847r1


November 2009

References

1. E. Perahia, ”IEEE P802.11 Wireless LANs: VHT below 6GHz PAR Plus 5C’s”, doc.:IEEE 802.11-08/0807r4.

2. ”Supplement to IEEE STANDARD for Information Technology – Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks - Specific Requirements”, IEEE Std 802.11a- 1999(R2003), June 2003.

3. ”Draft STANDARD for Information Technology – Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks - Specific Requirements”, IEEE P802.11n./D9.0, March 2009.

4. Peter L and Minho C, ”TGac Functional Requirements Rev.0”, doc.:IEEE 802.11-09/0304r0.

5. Rolf de V, ”802.11ac Usage Models Document”, doc.:IEEE802.11- 09/0161r2.

6. Minho C and Peter L, ”Proposal for TGac Evaluation Methodology”, doc.:IEEE802.11-09/0376r1.

doc.: ieee 802.11-09/0847r1 submission slide 1leonardo lanante, ochi lab, kit november 2009...

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