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
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Assaf Kasher (Intel)
John Doe, Some Company

2. Abstract This presentation addresses letter ballot comment CID 3492
Month Year
doc.: IEEE yy/xxxxr0
June 2006
Abstract
This presentation addresses letter ballot comment CID 3492
3492 Y
192 DT
HT-LTF for 40 MHz has the same values as the non-zero tones of the 20 MHz HT-LTF in the control channel for all subcarriers between -58 and -2. The tones in the extension channel are also the same as the non-zero 20 MHz HT-LTF values, except for subcarrier location +5 which is -1 while the 20 MHz HT-LTF is +1 at this location. This means you need to use different HT-LTF patterns for 20 and 40 MHz modes, while you could use only one pattern if all non-zero tones would use the same values.
Change subcarrier at location +5 of the 40 MHz HT-LTF from -1 to +1.
Assaf Kasher (Intel)
John Doe, Some Company

3. June 2006
Original Text
Assaf Kasher (Intel)

4. June 2006
Design reasoning
To save storage space, both sequences are based on the clause 17 LTF sequence.
In the 20MHz sequence 4 bits are added to extend the sequence from -26:26 to -28:28
In the 40MHz sequence the legacy sequence is placed at tones 6:58 and -58: bits are added filling the legacy DC tone and the tones -5:-2 and 5:2.
The needed storage is 52 bits for the legacy sequence, 4 new bits for the HT 20MHz, and 10 bits for the 40MHz sequence.
The filling tones were chosen to minimize the PAPR in the real and imaginary parts
Assaf Kasher (Intel)

5. PAPR results Real Imaginary abs Without Change 7.5 3.7 With Change 8.3
June 2006
PAPR results
Real
Imaginary
abs
Without
Change
7.5
3.7
With Change
8.3
7.3
4.3
Assaf Kasher (Intel)

6. Conlclusion The PAPR difference is not large.
June 2006
Conlclusion
The PAPR difference is not large.
The saving in changing the value of the bit are insignificant – I can’t see how it help.
My proposal – Reject the comment.
Assaf Kasher (Intel)