Doc.: IEEE 802.11-14/1398r0 Submission November 2014 Slide 1 Shiwen He, Haiming Wang Preamble Sequence for IEEE 802.11aj (45GHz) Authors/contributors:

doc.: IEEE 802.11-14/1398r0

Submission

November 2014

Slide 1 Shiwen He, Haiming Wang

Preamble Sequence for IEEE 802.11aj (45GHz)

Name Company Address Phone Email Shiwen HE

Southeast University (SEU)

2 Sipailou, Nanjing 210096, China

+86-25-5209 1653-3121 (ext.) [email protected]

Haiming WANG +86-25-5209 1653-301 (ext.) [email protected]

Yongming HUANG [email protected]

Wei HONG +86-25-5209 1650 [email protected]

Lvxi YANG [email protected]

Yu WANG [email protected]

Bo SUN ZTE [email protected]

Authors/contributors:

Date: 2014-11-5Presenter: Haiming Wang

doc.: IEEE 802.11-14/1398r0

Submission

November 2014

Shiwen He, Haiming WangSlide 2

Common preamble introduction

• Preamble is the beginning part of a PPDU—used for packet detection, AGC, frequency/timing synchronizations and channel estimation.

• The SC and OFDM systems for both 540MHz and 1080MHz bandwidth share a common preamble:

– Better support of the coexistence between various types of devices.

– Each device, especially Dual-Mode device (the device which supports SC mode and OFDM mode), needs to achieve packet detection/ synchronization/channel estimation for SIG mechanism only once .

– Appropriate re-sampling mechanism is required.

Given that OFDM and SC Data portions use different sampling rates.

doc.: IEEE 802.11-14/1398r0

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November 2014


Common preamble requirements• Low peak side lobe of periodic auto-correlation and low maximum value of

periodic cross-correlation.

− to accurate the timing synchronization

• Large zero correlation zone of periodic auto-correlation and periodic cross-correlation.

− 11aj maximum multipath delay spread: 100ns

− The time of zero correlation zone should be larger than 100ns to eliminate interference of multipath delay.

• The elements of preamble sequence should belong to finite collection of symbols, and low-complexity periodic correlator is needed.

– to simplify transmitter/receiver processing and reduce the power consumption

• Preamble sequence set should contain several sequences.

– to implement the MIMO technology

doc.: IEEE 802.11-14/1398r0

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Definition of ZCZ sequence set

• The sequence set is called Zero Correlation Zone (ZCZ)

sequence set when the following formula is satisfied:

where, denotes the periodic correlation between and , denotes the

energy of the sequence, denotes the ZCZ length, denotes the number of

ZCZ sequences.

1 2, , , QZ Z Z

,

, 0,, 1, ,0, 1 ,

0, 0 ,i jZ Z

E n i jC n i j Qn Z i j

n Z i j

iZ jZ,i jCZ Z E

Z Q

doc.: IEEE 802.11-14/1398r0

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November 2014


Proposed Generator for ZCZ sequence set• The initial mutually orthogonal aperiodic sequence sets:

• The iteration method:

where denotes the length of the column vector ,

and denotes identity matrix and zero matrix of the size ,

, denotes the diagonal

matrix with diagonal element , is element of the Discrete

Fourier Transform (DFT) matrix, is element of the

coefficient matrix, denotes all 1 column vector, denotes Kronecker product.

(0) (0)1,1 1,

(0)

,) (1

( 0),

0

Q

Q Q Q

a a

a a

A

1 1 1

1 1 1

1 1 1

1,

2, 1

,

k k k

k k k

k k k

Q L Q L Q L

k Q L Q L Q L

Q L Q L Q L

k

k

k

k

Q k

k

w

w

w

I 0 0

0 I 0

0 0 I

D 1

B A

A B

1 1 1 11,1 1, Q,1 Q,=Diag , , , , ,k k k kQ QQ L Q L Q L Q Lf f f f D I I I I

L (0), , 1, , , 1, ,i j i Q j Q a 1kQ L

I

1kQ L0 1 1k kQ L Q L

, , 1, , , 1, ,i jw i Q j K

Diag υ

υ , , 1, , , 1, ,i jf i Q j Q

1

doc.: IEEE 802.11-14/1398r0

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November 2014


Properties of ZCZ sequence set

• ZCZ sequence set :

− denotes the length of ZCZ sequence, denotes the number of ZCZ sequence,

denotes zero correlation zone of ZCZ sequence.

• The large length of periodic zero correlation zone:

• The coefficient matrix is variable.

• Changing the coefficient matrix to search optimized ZCZ sequence set with

low PSL and CL.

• The elements of ZCZ sequence set belong to the finite alphabet set.

2

3

1 , =21 2 , 3

K

K

Q Q L KZ

Q Q Q Q L K

, ,N Q ZZN Q

Z

doc.: IEEE 802.11-14/1398r0

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Example of ZCZ sequence set

• A kind of is designed to be 802.11aj preamble sequence .

• The peak side lobe of normalized periodic auto-correlation is 0.1976 and the

maximum value of normalized periodic cross-correlation is 0.3125.

− enhance the robustness of time synchronization

• The length of zero correlation zone is 56.

− the time of zero correlation zone:

− eliminate interference of multipath delay

• Quadriphase sequences:

− simplify receiver processing

• The generation parameters of and are detailed in

annex.

56 / 440MHz=127.3ns

256,4,56Z

256,4,56Z 512, 4,112Z

doc.: IEEE 802.11-14/1398r0

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Common preamble frame format

• Q-band training field (QTF) is composed of 14 repetitions of ZCZ sequences

which are denoted as .

− Chip-level π/2-QPSK modulation.

− The antenna transmits QTF .

− Using 14 repetitions of is a good tradeoff between PPDU efficiency, preamble

detection/synchronization sensitivity and channel estimation accuracy.

• Preamble det/sync SNR sensitivity matches those for decoding Payload with

MCS0

256iZ

256 , 1,2,3, 4i i Z

thi

256iZ

. . .QTF, 14periods (3584chips), transmitted by the antenna

QTF SIG-A Data

doc.: IEEE 802.11-14/1398r0

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Packet detection algorithm

• Delay correlation algorithm:

where denotes receiving QTF, denotes the length of ZCZ sequence, denotes

delay correlation of QTF , denotes energy of ZCZ sequence, denotes decision

value.

− If is greater than the certain threshold, and lasts for a certain period, then the

packet is detected.

− 3 repetitions of ZCZ sequence are used for packet detection and AGC convergence.

-1 -1

* 2

0 0

( ) ( ) ( ) , ( ) | |

| ( ) |( )( )

N N

k k

C n r n k N r n k P n r n k N

C nm nP n

r N C

P m

m

doc.: IEEE 802.11-14/1398r0

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Frequency synchronization algorithm• Frequency synchronization algorithm:

where denotes receiving QTF without frequency offset, denotes the sampling

interval, denotes frequency offset, denotes the angle of .

− The simulation shows that 6 repetitions of ZCZ sequence are a good tradeoff

between PPDU efficiency and frequency synchronization sensitivity.

2 2 ( )

-1 *0

,

( ) ( )

2

offset s offset sj f nT j f n N T

D

koffset

s

r n x n e r n N x n N e

r n k r n k Nf

NT

x sT

offsetf

doc.: IEEE 802.11-14/1398r0

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November 2014


Timing synchronization algorithm

• Local correlation algorithm:

where denotes local ZCZ sequence element, denotes timing synchronization

position.

− Timing synchronization is performed coherently with channel estimation.

*

1

( ) 0,1, , 1

arg max

N

m

C n r m n a m n N

n C n

a n

doc.: IEEE 802.11-14/1398r0

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November 2014


Channel estimation algorithm

• Linear least square (LS) estimation algorithm

where denotes time domain channel with 56 multipath, is a column vector

which denotes the local ZCZ sequence, denotes chips circular

shift of , denotes the receiving sequences with chips.

− The simulation shows that 5 repetitions of ZCZ sequence are a good tradeoff

between PPDU efficiency and channel estimation sensitivity.

56 1 11 Circ ,0 ,Circ ,1 , ,Circ ,55 NN

h a a a r

56 1h a

Circ , kaa

k

1Nr N

doc.: IEEE 802.11-14/1398r0

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November 2014


Conclusion

• ZCZ sequence set and its fast periodic correlator are applied in preamble to simplify receiver processing.

• A common preamble is proposed for different PHY modes.– SC and OFDM MCSs share the same preamble structure.

doc.: IEEE 802.11-14/1398r0

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Annex

1. Generator of ZCZ sequence set2. Generation parameters of 3. Generation parameters of 4. Simulation of correlation5. Simulation of packet detection6. Simulation of frequency offset estimation7. Simulation of channel estimation

256,4,56Z

256,4,56Z 512, 4,112Z

doc.: IEEE 802.11-14/1398r0

Submission

November 2014


Generator of ZCZ sequence set

Decom

position of colum

ns

Kronecker product

Kronecker product

...

......

...

......

......

. . .

. . .

......

......

...

...

...

... ...

Matrix

multiplication

Matrix

multiplication

doc.: IEEE 802.11-14/1398r0

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November 2014


Generation parameters of .

• Finite collection of symbols:

• Initial mutually orthogonal aperiodic sequence sets:

• DFT matrix:

• Coefficient matrix:

256,4,56Z

= 1, , 1,j j M

(0)

1 1 1 11 11 1 1 11 1

j j

j j

A

4

1 1 1 11 11 1 1 11 1

j jF

j j

1 11

1 11

j jj j j

j jj j j

W

doc.: IEEE 802.11-14/1398r0

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November 2014


Generation parameters of .

• Finite collection of symbols:

• Initial mutually orthogonal aperiodic sequence sets:

• DFT matrix:

• Coefficient matrix:

= 1, , 1,j j M

4

1 1 1 11 11 1 1 11 1

j jF

j j

512,4,112Z

(0)

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

A

1

11

j j jj j j jj j jj j j

W

doc.: IEEE 802.11-14/1398r0

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November 2014


Correlation of .

-300 -200 -100 0 100 200 3000

0.05

0.1

0.15

0.2

0.25

0.3

0.35

Shift chip

Peri

odic

ZC

Z-cc

orr

Periodic cross-correlation of ZCZ sequences

-300 -200 -100 0 100 200 3000

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Shift chip

Peri

odic

ZC

Z-ac

orr

Periodic auto-correlation of ZCZ sequence

256,4,56Z

doc.: IEEE 802.11-14/1398r0

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November 2014


Packet detection (1)

It is shown that threshold 0.2 is a better choice to satisfy the demand of packet detection sensitivity.

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.910

-5

10-4

10-3

10-2

10-1

100

threshold

mis

sing

det

ectio

n pr

obab

ility

false negative ratio, 1x1 antenna

false negative ratio:SNR=-20dBfalse negative ratio:SNR=-15dBfalse negative ratio:SNR=-10dBfalse negative ratio:SNR=-5dBfalse negative ratio:SNR=0dBfalse negative ratio:SNR=5dBfalse negative ratio:SNR=10dBfalse negative ratio:SNR=15dBfalse negative ratio:SNR=20dB

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.910

-4

10-3

10-2

10-1

threshold

fals

e de

tect

ion

prob

abili

ty

false positive ratio, 1x1 antenna

false positive ratio:SNR=-20dBfalse positive ratio:SNR=-15dBfalse positive ratio:SNR=-10dBfalse positive ratio:SNR=-5dBfalse positive ratio:SNR=0dBfalse positive ratio:SNR=5dBfalse positive ratio:SNR=10dBfalse positive ratio:SNR=15dBfalse positive ratio:SNR=20dB

doc.: IEEE 802.11-14/1398r0

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November 2014




0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.910

-4

10-3

10-2

10-1

100

threshold

mis

sing

det

ectio

n pr

obab

ility



0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.910

-5

10-4

10-3

10-2

10-1

threshold

fals

e de

tect

ion

prob

abili

ty



doc.: IEEE 802.11-14/1398r0

Submission

November 2014




0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.910

-4

10-3

10-2

10-1

100

threshold

mis

sing

det

ectio

n pr

obab

ility



0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.910

-4

10-3

10-2

10-1

threshold

fals

e de

tect

ion

prob

abili

ty



doc.: IEEE 802.11-14/1398r0

Submission

November 2014


Frequency offset estimation

It is shown that 6 repetitions of ZCZ sequence satisfy the demand of frequency synchronization sensitivity.

-5 0 5 1010

-3

10-2

10-1

100

SNR (dB)

RM

SE

(ppm

)

nTx=4, nRx=4, 540MHz

frequency offset estimation 2 symbolsfrequency offset estimation 4 symbolsfrequency offset estimation 6 symbolsfrequency offset estimation 8 symbols

21F

RMSEF

F denotes the number of frames in simulation, denotes real frequency offset, denotes estimated frequency offset.

doc.: IEEE 802.11-14/1398r0

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Channel estimation

It is shown that 5 repetitions of ZCZ sequence satisfy the demand of channel estimation sensitivity.

-5 0 5 10-20

-18

-16

-14

-12

-10

-8

-6

-4

-2

0

SNR (dB)

NM

SE

(dB

)

nTx=4, nRx=4, 540MHz

channel estimation 3 symbolschannel estimation 4 symbolschannel estimation 5 symbolschannel estimation 6 symbols

doc.: IEEE 802.11-14/1398r0

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November 2014


Thanks for Your Attention.

Documents

Doc.: IEEE 802.11-14/1398r0 Submission November 2014 Slide 1 Shiwen He, Haiming Wang Preamble Sequence for IEEE 802.11aj (45GHz) Authors/contributors: