doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 1 Shiwen He ， Haiming Wang

Cyclic Shift Diversity Design for IEEE 802.11aj (45GHz)

Authors/contributors:

Date: 2015-01-21Presenter: Shiwen HE

Name Company Address Phone Email

Shiwen HE

Southeast University (SEU)

2 Sipailou, Nanjing 210096, China

+86-25-5209 1653-3121 (ext.)

hesw01@seu.edu.cn

Haiming WANG +86-25-5209 1653-301 (ext.)

hmwang@seu.edu.cn

Yongming HUANG huangym@seu.edu.cn

Wei HONG +86-25-5209 1650 weihong@seu.edu.cn

Luxi YANG lxyang@seu.edu.cn

Peng CHEN topcp@sina.com

Shimin MA sdtzmsm@126.com

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 2 Shiwen He ， Haiming Wang

Background

•Cyclic shift diversity (CSD) is a simple and valid strategy that can be

used to achieve spatial diversity.

•CSD can reduce the effects of unintended beamforming when correlated

signals are transmitted in multiple space-time streams.

•CSD can be achieved straightforwardly by introducing different cyclic

shifts to every part of the OFDM symbols or blocks in SC systems.

•802.11n and 802.11ac defined their CSD table values respectively.

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 3 Shiwen He ， Haiming Wang

Introduction In OFDM scenario:

- Cyclic delays are introduced to the effective parts of the OFDM symbols, illustrated as following.

In SC scenario:

- Cyclic delays are introduced to the parts of the blocks, illustrated as following.

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 4 Shiwen He ， Haiming Wang

The Optimization of CSD values ：

- When applying cyclic delay, the signal received via multiple transmitting

antennas in frequency domain is

where is the cyclic delay value at the transmitter antenna ， and

is the number of transmitter antenna, is the addictive noise.

- The cyclic delays can be seen respectively as phase rotations introduced to the channel frequency response

2

1

1( ) ( ) ( ) ( )

1,2,...,

Tx

i

Nj k

iiTx

FFT

Y k H k X k e Z kN

k N

，

2

1

1( ) ( )

Tx

i

Nj k

iiTx

H k H k eN

i thi

TxN ( )Z k

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 5 Shiwen He ， Haiming Wang

- It is assumed that the composite channels have similarly stochastic properties, expressed by a common correlation function

is a random gap of frequency.

- Then the correlation function of the composite channels can be expressed

as

Since

then which implies that the correlation is reduced.

*( ) { ( ) ( )}H i ik H k H k kE

2

1

1( ) ( )

Tx

i

Nj k

H HiTx

k k eN

k

2

1

1| | 1

Tx

i

Nj k

iTx

eN

2

1

1( ) ( ) ( )

Tx

i

Nj k

H H HiTx

k k e kN

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 6 Shiwen He ， Haiming Wang

- With selecting appropriately , it is possible to force a zero in the correlation function and to introduce better diversity to the composite channel.

where F is the sub-carrier spacing, and l, m are integer variables.

- Such a result is achieved for delays

i

( )( )

0H Tx

H

mF if m lNmF

otherwise

{ ,2 ,..., ( 1) }Txk F F N F

( 11

) FFTii

T Txx

Nn i

N

ior

N F

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 7 Shiwen He ， Haiming Wang

Four sub-channels realization of 4x1 system(OFDM):

0 50 100 150 200 250-20

-15

-10

-5

0

5channel transfer function

mag

nitu

de [d

B]

0 50 100 150 200 250-10

-5

0

5

mag

nitu

de [d

B]

channel transfer function

0 50 100 150 200 250-12

-10

-8

-6

-4

sub-carrier index

mag

nitu

de [d

B]

0 50 100 150 200 250-20

-15

-10

-5

sub-carrier index

mag

nitu

de [d

B]

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 8 Shiwen He ， Haiming Wang

Equivalent channel realization of 4x1 system(OFDM):

Without CSD Applying CSD

0 50 100 150 200 250-10

-8

-6

-4

-2

0

2

sub-carrier index

mag

nitu

de [

dB]

channel transfer function without CSD

0 50 100 150 200 250-14

-12

-10

-8

-6

-4

-2

0

2

4

sub-carrier index

mag

nitu

de [

dB]

channel transfer function with CSD

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 9 Shiwen He ， Haiming Wang

CSD Table for OFDM Data field :

TCS(n) values for the data fields of a PPDU

NSTS,total

Cyclic shift for space-time stream n (ns)

1 2 3 4

10 - - -

2 0 -128Ts - -

3 0 -170Ts -85Ts -

4 0 -128Ts -64Ts -192Ts

1 s

s

TF

æ ö÷ç ÷=ç ÷ç ÷çè ø

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 10 Shiwen He ， Haiming Wang

CSD cont: Spatial Extending for OFDM :

NSTS NTx Qk

1 2  

1 4  

2 4  

3 4  

11-1282 sT

é ùê úê úë û

1

-1281

-642

-192

s

s

s

T

T

T

1 0

0 11

-64 02

0 -64s

s

T

T

é ùê úê úê úê úê úê úë û

1 0 0

0 42 03

0 0 212

-192 0 0

s

s

s

T

T

T

é ùê úê úê úê úê úê úë û

1 s

s

TF

æ ö÷ç ÷=ç ÷ç ÷çè ø

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 11 Shiwen He ， Haiming Wang

CSD Table for SC Data field :

TCS(n) values for the data fields of a PPDU

NSTS,total

Cyclic shift for space-time stream n (ns)

1 2 3 4

10 - - -

2 0 -128Tc - -

3 0 -170Tc -85Tc -

4 0 -128Tc -64Tc -192Tc

1 c

c

TF

æ ö÷ç ÷=ç ÷ç ÷çè ø

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 12 Shiwen He ， Haiming Wang

CSD cont: Spatial Extending for SC :

NSTS NTx Qk

1 2  

1 4  

2 4  

3 4  

11-1282 cT

é ùê úê úë û

1

-1281

-642

-192

c

c

c

T

T

T

é ùê úê úê úê úê úê úê úë û

1 0

0 11

-64 02

0 -64c

c

T

T

é ùê úê úê úê úê úê úë û

1 0 0

0 42 03

0 0 212

-192 0 0

c

c

c

T

T

T

é ùê úê úê úê úê úê úë û

1 c

c

TF

æ ö÷ç ÷=ç ÷ç ÷çè ø

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 13 Shiwen He ， Haiming Wang

Simulation

Comparisons of error performance of the 2x1 OFDM system with QPSK Modulation and 1/2-rate.

0 1 2 3 4 5 6 7 8 910

-3

10-2

10-1

100

SNR/dB

PE

R

1x12x1,CSD2x1,STBC

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 14 Shiwen He ， Haiming Wang

Comparisons of error performance of the 2x1 SC system with QPSK Modulation and 1/2-rate.

0 2 4 6 8 1010

-3

10-2

10-1

100

SNR(dB)

PE

R

1x12x1,CSD2x1.STBC

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 15 Shiwen He ， Haiming Wang

Conclusion

•With QPSK modulation and 1/2-rate, PER performance can be improved about 1dB at the PER of 0.1 by using the proposed CSD table values .

•Compared with STBC, the proposed CSD scheme loses a little gain with QPSK modulation and 1/2-rate. However, CSD scheme has low additional complexity.

•The proposed CSD table values can be applied to the data field of the OFDM or SC scenario.

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 16 Shiwen He ， Haiming Wang

References

•[1] 11-06-0952-01-000n-lb84-csd-text-proposal-submission.•[2] 11-10-1301-00-00ac-legacy-csd-table-for-11ac.•[3] K. Witrisal, Y.-H. Kim and R. Prasad, “Antenna diversity for OFDM using cyclic delays”, Benelux: Roc. SCVT-2001, 2001.10, pp. 13-17.

doc.: IEEE 11-15/0210r0

Submission

September 2014

Slide 17 Shiwen He ， Haiming Wang

Thanks for Your Attention.