July 2010
doc.: IEEE 802.11-10/0786r0
Pilot Sequence design up to 8 Spatial Streams
Date: 2010-07-13
Authors:
Name
Daewon Lee
Bonghoe Kim
Byeongwoo Kang
Submission
Affiliations
Address
LG R&D Complex 533,
Hogye-1dong, Dongan-Gu,
LG Electronics, Inc.
Anyang-Shi, Kyungki-Do,
431-749, Korea
LG R&D Complex 533,
Hogye-1dong, Dongan-Gu,
LG Electronics, Inc.
Anyang-Shi, Kyungki-Do,
431-749, Korea
LG R&D Complex 533,
Hogye-1dong, Dongan-Gu,
LG Electronics, Inc.
Anyang-Shi, Kyungki-Do,
431-749, Korea
Slide 1
Phone
email
+82-31-450-7897
[email protected]
+82-31-450-4131
[email protected]
+82-31-450-4131
[email protected]
m
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Abstract
We discuss some of the pilot design principles for 11ac
and propose use a single pilot mother matrix in which all
pilots for each bandwidth and spatial stream get its pilot
sequence values
Submission
Slide 2
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Pilot Sequence Design
• Design Target
– Pilot sequences must be defined up to 8 spatial streams
– Pilot sequence also must be defined for 80 MHz
• Design principles
– Performance difference between different pilot sequences is not
expected to be large
– Rather than defining a pilot sequence for each instance (number of
spatial streams & bandwidth size) define a large sequence matrix
for all spatial streams and bandwidth may be preferable
Submission
Slide 3
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Discussion (1/2)
• performance in various scenarios
– It will be important to consider tracking performance in various
scenarios
– orthogonal pilot sequence across spatial streams may give robust
performance in case of correlated Tx antenna configurations
– some studies [1] show that having orthogonal pilot design may be
more robust for highly correlated channels
• pilot tracking functionality
– Orthogonal pilots do not necessary mean pilot tracking
functionality is mandated to gather pilots over multiple OFDM
symbols for processing
Submission
Slide 4
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Discussion (2/2)
• Complexity for supporting orthogonal pilot design
– 11n pilots has been design to be orthogonal between spatial streams (note
that not all pilot tones in 40MHz are time domain orthogonal)
– if orthogonal pilot tone tracking is implemented for 11n then same
functionality can be re-utilized in 11ac
– no mandate of separate phase tracking per spatial stream
• may not be needed if single LO is used at Tx/Rx
– no additional complexity for phase tracking is expected
• PAPR of pilot sequence
– PAPR increase due to certain ‘bad’ pilot sequences design is expected to
be marginal because OFDM data tones will effect the PAPR the most
– some PAPR analysis for pilot in VHT data portion is shown in the Annex
Submission
Slide 5
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Pilot Sequence for 20 MHz
• 20 MHz Pilot Sequence Positions
: pilot subcarrier
-21
-7
7
21
Subcarrier index
: data subcarrier
• 11n Pilot Sequence


s4  0,,0, piSTS ,n4 ,0,,0, piSTS ,n14 ,0,,0, piSTS ,n24 ,0,,0, piSTS ,n34 ,0,,0
• Proposed 11ac Pilot Sequence


s4  0,,0, piSTS ,n8 ,0,,0, piSTS ,n18 ,0,,0, piSTS ,n28 ,0,,0, piSTS ,n38 ,0,,0
Submission
Slide 6
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Pilot Sequence for 40 MHz
• 40 MHz Pilot Sequence Positions
: pilot subcarrier
-53
-25
-11
11
25
: data subcarrier
53
Subcarrier index
• 11n Pilot Sequence

0, ,0, piSTS ,n6 ,0,,0, piSTS ,n 16 ,0,,0, piSTS ,n  26 ,0, ,0, piSTS ,n 36 ,0,,0,

s6  


p
,
0
,

,
0
,
p
,
0
,

,
0


iSTS , n  4 6
iSTS , n  5 6


• Proposed 11ac Pilot Sequence
0, ,0, piSTS ,n8 ,0, ,0, piSTS ,n 18 ,0,,0, piSTS ,n  28 ,0,,0, piSTS ,n 38 ,0, ,0,
s6  

 piSTS ,n  48 ,0, ,0, piSTS ,n 58 ,0, ,0

Submission
Slide 7
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Pilot Sequence for 80 MHz
• 80 MHz Pilot Sequence Positions
: pilot subcarrier
: data subcarrier
-103
-75
-39
-11
11
39
75
103
Subcarrier index
• Proposed 11ac Pilot Sequence
0, ,0, piSTS ,n8 ,0, ,0, piSTS ,n 18 ,0,,0, piSTS ,n  28 ,0, ,0, piSTS ,n 38 ,0,,0 
s8  

,0, ,0, piSTS ,n  48 ,0, ,0, piSTS ,n 58 ,0, ,0, piSTS ,n  68 ,0,,0, piSTS ,n  78 ,0, ,0
Submission
Slide 8
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Proposed pilot sequence mother matrix
• Pilot Sequence mother matrix
NSTS
iSTS
piSTS,0
piSTS,1
piSTS,2
piSTS,3
piSTS,4
piSTS,5
piSTS,6
piSTS,7
1~8
1
1
1
1
-1
1
1
1
1
2~8
2
-1
1
1
1
1
1
-1
-1
3~8
3
1
-1
1
1
1
-1
1
-1
4~8
4
1
1
-1
1
1
-1
-1
1
5~8
5
1
1
1
-1
-1
-1
-1
-1
6~8
6
-1
1
1
1
-1
-1
1
1
7~8
7
1
-1
1
1
-1
1
-1
1
8
8
1
1
-1
1
-1
1
1
-1
Submission
Slide 9
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Summary
• We give one candidate proposal for the pilot sequences
for data portion of the VHT PLCP preamble
• We propose to further consider different pilot sequence
for each spatial streams
• We propose to further consider orthogonal pilot
sequence design to make pilot tracking more robust
against various deployment scenarios
Submission
Slide 10
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Reference
• [1] Aoki, T.; Sandell, M.; , "Analysis of pilots for
residual frequency offset estimation in MIMO OFDM
systems," Wireless Communications, IEEE
Transactions on , vol.8, no.3, pp.1128-1132, March
2009.
Submission
Slide 11
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Annex
Submission
Slide 12
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Annex. PAPR analysis of proposed pilot
sequence (1/3)
• Data PAPR analysis as reference
• 20 MHz BW with proposed pilot sequence
• Different CDF curves represent CDF of each spatial stream
Data PAPR [dB] CDF
1
PAPR [dB] CDF of 20 MHz BW
1
20MHz
40MHz
80MHz
0.9
0.8
0.9
0.8
0.7
0.7
0.6
CDF
CDF
0.6
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0
0
0
2
Submission
4
6
8
PAPR [dB]
10
12
14
Slide 13
0
2
4
6
8
PAPR [dB]
10
12
14
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Annex. PAPR analysis of proposed pilot
sequence (2/3)
• 40 MHz BW with proposed pilot sequence & PAPR reduction γ
sequence [ +1 +j ] used
• Different CDF curves represent CDF of each spatial stream
PAPR [dB] CDF of 40 MHz BW
Data PAPR [dB] CDF
1
1
20MHz
40MHz
80MHz
0.9
0.8
0.7
0.7
0.6
0.6
CDF
CDF
0.8
0.9
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0
0.1
0
2
Submission
4
6
8
PAPR [dB]
10
12
14
0
Slide 14
0
2
4
6
8
PAPR [dB]
10
12
14
Daewon Lee, LG Electronics
July 2010
doc.: IEEE 802.11-10/0786r0
Annex. PAPR analysis of proposed pilot
sequence (3/3)
• 80 MHz BW with proposed pilot sequence & PAPR reduction γ
sequence [ +1 +j +1 +j ] used
• Different CDF curves represent CDF of each spatial stream
Data PAPR [dB] CDF
PAPR [dB] CDF of 80 MHz BW
1
1
20MHz
40MHz
80MHz
0.9
0.8
0.9
0.8
0.7
0.7
0.6
CDF
CDF
0.6
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0
0
2
Submission
4
6
8
PAPR [dB]
10
12
0
14
Slide 15
0
2
4
6
8
PAPR [dB]
10
12
14
Daewon Lee, LG Electronics