1. doc.: IEEE 802.15-09-0114-00-004g-Trends-in-SUN-capacity
<month year>
Apr. 2013
Project: IEEE P Working Group for Wireless Personal Area Networks(WPANs)
Submission Title: Comment on OFDM LTF sequence and its resolution
Date Submitted: Apr. 2013
Source: Jaehwan Kim, Byounghak Kim, Cheolho Shin, Mi-Kyung Oh, Sangsung Choi (ETRI) and Soo-Young Chang (SYCA)
Contact:
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Re: LB88 Comment
Abstract:
Purpose: Notice: This document has been prepared to assist the IEEE P 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 acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P
Slide 1
ETRI
Emmanuel Monnerie, Landis+Gyr

2. Current LTF Sequence LTF sequence Goal of LTF sequence design
Apr. 2013
Current LTF Sequence
LTF sequence
Goal of LTF sequence design
To find the best sequence for OFDM symbol boundary detection and channel estimation, etc
Tone#
Value
-64
-48 1
-32
-16 16 32 48
-63
-47
-31
-15 -1 17 33 49
-62
-46
-30
-14 2 18 34 50
-61
-45
-29
-13 3 19 35 51
-60
-44
-28
-12 4 20 36 52
-59
-43
-27
-11 5 21 37 53
-58
-42
-26
-10 6 22 38 54
-57
-41
-25 -9 7 23 39 55
-56
-40
-24 -8 8 24 40 56
-55
-39
-23 -7 9 25 41 57
-54
-38
-22 -6 10 26 42 58
-53
-37
-21 -5 11 27 43 59
-52
-36
-20 -4 12 28 44 60
-51
-35
-19 -3 13 29 45 61
-50
-34
-18 -2 14 30 46 62
-49
-33
-17 15 31 47 63
ETRI

3. OFDM Symbol Boundary Detection
Apr. 2013
OFDM Symbol Boundary Detection
Current SHR
To achieve symbol boundary detection, cross correlation of received signal and LTF should be checked in time domain
Problem
With 32 tap and 64 tap LTF cross correlations, about 3 dB and 0 dB SNRs are required respectively, for satisfied symbol boundary detection
To calculate cross correlation with more than 64 taps, data should be synchronized at symbol boundary detection point
Higher latency and hardware complexity are required
ETRI

4. Proposed LTF Sequence Proposed LTF sequence Apr. 2013 ETRI Tone# Value
-64
-48 -1
-32
-16 1 16 32 48
-63
-47
-31
-15 17 33 49
-62
-46
-30
-14 2 18 34 50
-61
-45
-29
-13 3 19 35 51
-60
-44
-28
-12 4 20 36 52
-59
-43
-27
-11 5 21 37 53
-58
-42
-26
-10 6 22 38 54
-57
-41
-25 -9 7 23 39 55
-56
-40
-24 -8 8 24 40 56
-55
-39
-23 -7 9 25 41 57
-54
-38
-22 -6 10 26 42 58
-53
-37
-21 -5 11 27 43 59
-52
-36
-20 -4 12 28 44 60
-51
-35
-19 -3 13 29 45 61
-50
-34
-18 -2 14 30 46 62
-49
-33
-17 15 31 47 63
ETRI

5. Proposed LTF Sequence Property of the proposed LTF sequence
Apr. 2013
Proposed LTF Sequence
Property of the proposed LTF sequence
IFFT result of the first 32 tap is similar to negative s in STF
ETRI

6. Benefits from Proposed LTF Sequence
Apr. 2013
Benefits from Proposed LTF Sequence
Higher OFDM symbol boundary detection probability
Autocorrelation for the proposed LTF has more distinctive than Cross correlation for current LTF at detection point
With the new LTF, -1 dB SNR is needed to detect symbol boundary
Current LTF needs about 3 dB SNR for symbol boundary detection
ETRI

7. Apr. 2013
Conclusion
Current LTF sequence is less proper to perform time domain correlation for OFDM symbol boundary detection
Proposed LTF can increase the symbol boundary detection probability
It is recommended to change the current LTF sequence to the proposed LTF sequence
ETRI