1. PAPR in LTF’s in with and without rotation of the upper subcarrier
Month Year
doc.: IEEE yy/xxxxr0
June 2006
PAPR in LTF’s in with and without rotation of the upper subcarrier
Date:
Authors:
Name
Company
Address
Phone
Assaf Kasher
Intel
Notice: This document has been prepared to assist IEEE 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.
Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE
Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures < ieee802.org/guides/bylaws/sb-bylaws.pdf>, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE Working Group. If you have questions, contact the IEEE Patent Committee Administrator at
Assaf Kasher (Intel)
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
June 2006
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 rejected based on the analysis given in this presentation
Assaf Kasher (Intel)
John Doe, Some Company

3. June 2006 Assaf Kasher (Intel) 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
90 degree rotation does not help the PAPR as seen by the analog section
delete line 9-10
222 12
90 degree rotation is not required
remove gamma in equation 20-7
223 1
delete the definition of Gamma
225 10
90 degree rotation is unnecessary
delete line 10
227
delete line 18
226 15
remove Gamma
229
remove j multiplication in row 3 cloumn 2 of table n66
231
90 degree rotationin the upper 20MHz band is unnecessary
change equation in row 3 column 2 accordingly
234 17
delete Gamma and the definition of Gamma
235
237
238 14
modify the equation for the tones in the upper band accordingly.
239 6
delete Gamma
Assaf Kasher (Intel)

4. Month Year
doc.: IEEE yy/xxxxr0
June 2006
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:
Assaf Kasher (Intel)
John Doe, Some Company

5. Peak to Average Power Ratio [dB]
Month Year
doc.: IEEE yy/xxxxr0
June 2006
PAPR results: L-STF
Peak to Average Power Ratio [dB]
real
imaginary
absolute
No Rotation 40Msps
With Rotation 40Msps
No Rotation 80Msps
With Rotation 80Msps
Assaf Kasher (Intel)
John Doe, Some Company

6. PAPR results: L-LTF June 2006 Peak to Average Power Ratio [dB] real
Month Year
doc.: IEEE yy/xxxxr0
June 2006
PAPR results: L-LTF
Peak to Average Power Ratio [dB]
real
imaginary
absolute
No Rotation 40Msps
With Rotation 40Msps
No Rotation 80Msps
With Rotation 80Msps
Assaf Kasher (Intel)
John Doe, Some Company

7. PAPR results – HT-LTF June 2006 Month Year doc.: IEEE 802.11-yy/xxxxr0
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)
With Rotation 80Msps (FFT 256)
9.37
7.49
6.36
Assaf Kasher (Intel)
John Doe, Some Company

8. Month Year
doc.: IEEE yy/xxxxr0
June 2006
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.
Assaf Kasher (Intel)
John Doe, Some Company