June 2006

Assaf Kasher (Intel)

Slide 1

doc.: IEEE 802.11-06/1595r1

Submission

PAPR in LTF’s in with and without rotation of the upper subcarrier

Notice: This document has been prepared to assist IEEE 802.11. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

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Date: 2006-06-06Authors:

Name Company Address Phone email

Assaf Kasher Intel assaf.kasher@intel.com

June 2006

Assaf Kasher (Intel)

Slide 2

doc.: IEEE 802.11-06/1595r1

Submission

Abstract

• This presentation addresses letter ballot comments with the CID’s in the table on the right:

• These comments propose to remove the 90° rotation from the upper 20Mhz of a 40MHz channel.

• These comments should be countered based on the analysis given in this presentation

June 2006

Assaf Kasher (Intel)

Slide 3

doc.: IEEE 802.11-06/1595r1

Submission

137 18 20.1.3 rotation by j does not change the PAPR as seen by the analog electronics

delete the sentence "To reduce the pak-to-average …."

221 9 20.3.3.2.1.2

90 degree rotation does not help the PAPR as seen by the analog section

delete line 9-10

222 12 20.3.3.2.1.2

90 degree rotation is not required remove gamma in equation 20-7

223 1 20.3.3.2.1.2

delete the definition of Gamma delete the definition of Gamma

225 10 20.3.3.2.1.3

90 degree rotation is unnecessary delete line 10

227 18 20.3.3.2.1.3

90 degree rotation is unnecessary delete line 18

226 15 20.3.3.2.1.3

90 degree rotation is unnecessary remove Gamma

229 1 20.3.3.2.1.4

90 degree rotation is unnecessary remove j multiplication in row 3 cloumn 2 of table n66

231 1 20.3.3.2.2.2

90 degree rotationin the upper 20MHz band is unnecessary

change equation in row 3 column 2 accordingly

234 17 20.3.3.2.2.3

90 degree rotation is unnecessary delete Gamma and the definition of Gamma

235 9 20.3.3.2.2.3

90 degree rotation is unnecessary delete Gamma and the definition of Gamma

237 15 20.3.3.3 90 degree rotation is unnecessary delete Gamma and the definition of Gamma

238 14 20.3.3.3.3.2

90 degree rotation is unnecessary modify the equation for the tones in the upper band accordingly.

239 6 20.3.3.3.4 90 degree rotation is unnecessary delete Gamma

June 2006

Assaf Kasher (Intel)

Slide 4

doc.: IEEE 802.11-06/1595r1

Submission

Introduction

• The 90° rotation of the upper channel has been introduced to reduced PAPR (Peak to Average Power Ratio) in the transmission of the STF and LTF’s.

• PAPR is defined as:

12

01

2

0

maxN

nN

n

abs x n

abs x n

N

June 2006

Assaf Kasher (Intel)

Slide 5

doc.: IEEE 802.11-06/1595r1

Submission

PAPR results: L-STF

Peak to Average Power Ratio [dB]  

real imaginary absolute

No Rotation 40Msps 8.07601047 8.0760105 5.0996852

With Rotation 40Msps 2.7929476 4.3188525 2.0893852

No Rotation 80Msps 8.07601047 8.0760105 5.0996852

With Rotation 80Msps 6.124772 6.9110635 5.249665

June 2006

Assaf Kasher (Intel)

Slide 6

doc.: IEEE 802.11-06/1595r1

Submission

PAPR results: L-LTF

Peak to Average Power Ratio [dB]  

real imaginary absolute

No Rotation 40Msps 6.11823959 6.0918767 3.1658108

With Rotation 40Msps 6.59219725 5.8947039 4.1857537

No Rotation 80Msps 6.11823959 6.0918767 3.1658108

With Rotation 80Msps 6.87894257 6.1259336 4.1857537

June 2006

Assaf Kasher (Intel)

Slide 7

doc.: IEEE 802.11-06/1595r1

Submission

PAPR results – HT-LTF

 

Peak to Average Power Ratio [dB]  

  real imaginary absolute

No Rotation 40Msps 8.54 7.27 5.63

With Rotation 40Msps 6.32 6.34 3.41

No Rotation 80Msps (FFT 256) 8.54 7.27 5.63

With Rotation 80Msps (FFT 256) 9.37 7.49 6.36

June 2006

Assaf Kasher (Intel)

Slide 8

doc.: IEEE 802.11-06/1595r1

Submission

Conclusion• We can see that the 90° rotation improves PAPR

significantly in the L-STF and in the HT-LTF when the sampling rate is 40Msps.

• There is not significant degradation in PAPR in the other cases.

• We therefore propose to keep the 90° rotation.• We propose removing the sentence “To reduce the peak

to average power ratio,” from page 186, line 71.• We propose removing the sentence “The 90 rotation

helps keep the PAPR of the L-STF in 40 MHz comparable to that in 20 MHz.” from line 14 of page 214.looooon