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doc.: IEEE 802.11-10/0264r3
Submission
March 2010
André Bourdoux, IMECSlide 1
Channel Estimation Sequence for TGadDate: 2010-02-27
Name Affiliations Address Phone email André Bourdoux IMEC Kapeldreef 75,
3001 Leuven, Belgium
+32-16-288.215 [email protected]
Authors:
doc.: IEEE 802.11-10/0264r3
Submission
March 2010
André Bourdoux, IMECSlide 2
Abstract
A channel estimation sequence construction is proposed for TGad. It allows to estimate easily the channel response and the IQ imbalance parameters.
doc.: IEEE 802.11-10/0264r3
Submission
Channel estimation sequence (CES) constructed from Golay complementary pair
March 2010
André Bourdoux, IMECSlide 3
a256 =
[aL aR] aR aL
b256 =
[bL bR] bR bL
Cyclic prefix Cyclic postfix
• a256 and b256 are complementary Golay sequences i.e. a Golay Complementary Pair (GCP)
• Main advantage:• sum of auto-correlation sequences is ideal (see next slide)• easy generation and correlation with lattice structure [Budisin – Electronic Letters – January 1991]
NB: - this construction was proposed in an early draft of SC PHY in IEEE802.15.3c - length 256 is illustrated here as an example
doc.: IEEE 802.11-10/0264r3
Submission
Periodic correlation of “randomly” chosen GCP
March 2010
André Bourdoux, IMECSlide 4
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|X(a,a*)|
|X(b,b*)|
|X(a,a*)+X(b,b*)|
Non zero-side lobes
Non zero-side lobes
Zero-side lobes
• X(a,a*) is the correlation with a*=conj(a) i.e. the matched filter
• X(a,a*) and X(b,b*) are not usable alone because of non-zero sidelobes
• Only X(a,a*)+X(b,b*) is exploitable
doc.: IEEE 802.11-10/0264r3
Submission
Basic CES processing
March 2010
André Bourdoux, IMECSlide 5
hCESX( . ,a*)
X( . ,b*)
ca
cb
ca +cb
ca
cb
ca + cb`
X(a,a*) ▪ ▪ ▪ X(b,a*)
X(a,b*) ▪ ▪ ▪ X(b,b*)
z-2N
▪ ▪ ▪ X(a,a*) ▪ ▪ + ▪ ▪ ▪ X(b,b*) ▪ ▪ ▪
doc.: IEEE 802.11-10/0264r3
Submission
Received ca and cb with “randomly” chosen GCP
March 2010
André Bourdoux, IMECSlide 6
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ca
cb
ca + cb
AWGN Multipath
doc.: IEEE 802.11-10/0264r3
Submission
First desired cyclic correlation properties of the GCP
March 2010
André Bourdoux, IMECSlide 7
|X(a,a*)|
|X(b,b*)|
|X(a,a*)+X(b,b*)|
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• X(a,a*) and X(b,b*) are usable alone because of zero-correlation zone of length N/4=64
• X(a,a*)+X(b,b*) is also exploitable
doc.: IEEE 802.11-10/0264r3
Submission
Second desired cyclic correlation properties of the GCP
March 2010
André Bourdoux, IMECSlide 8
|X(a,a)|
|X(b,b)|
|X(a,a)+X(b,b)|
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• X(a,a) and X(b,b) also have a zero-correlation zone of length N/4=64
doc.: IEEE 802.11-10/0264r3
Submission
Third desired cyclic correlation properties of the GCP
March 2010
André Bourdoux, IMECSlide 9
|X(a,b*)|
|X(b,a*)|
|X(a,b*)+X(b,a*)|
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• X(a,b*) and X(b,a*) also have a zero-correlation zone of length N/4=64
becausea = -b*
doc.: IEEE 802.11-10/0264r3
Submission
Response with good GCP
March 2010
André Bourdoux, IMECSlide 10
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AWGN Multipath
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ca
cb
ca + cb
doc.: IEEE 802.11-10/0264r3
Submission
Response with a256 and b256 from the approved SC PHY in IEEE802.15.3c
March 2010
André Bourdoux, IMECSlide 11
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AWGN Multipath
ca
cb
ca + cb
doc.: IEEE 802.11-10/0264r3
Submission
RX IQ imbalance creates self-interference
March 2010
André Bourdoux, IMECSlide 12
The desired signal is corrupted by its complex conjugate
doc.: IEEE 802.11-10/0264r3
Submission
Response with IQ imbalance, good GCP
March 2010
André Bourdoux, IMECSlide 13
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With IQ imbalanceWithout IQ imbalance
Nh Nh*
NhNh*
Nh
Nh
The ratio /* can easily be estimated
ca
cb
ca + cb
doc.: IEEE 802.11-10/0264r3
Submission
IQ compensation
March 2010
André Bourdoux, IMECSlide 14
Received signal:
*xxr
For the compensation of the received signal, we just need /*:
x
xxxx
rrrcomp
*
22
****
*
**
|
)(
This small amplitude coefficient will be compensated for by the equalizer
doc.: IEEE 802.11-10/0264r3
Submission
March 2010
André Bourdoux, IMECSlide 15
Summary
• A Golay complementary pair (GCP) is a good candidate for the channel estimation sequence
• The GCP can be chosen to ease the estimation of the IQ imbalance parameters: in particular, GCP with maximal length (N/4) zero-correlation zones are ideal
• Easy estimation of channel response and IQ imbalance possible if:– GCP have properties in slide 7,8 and 9 (zero correlation zones)
– Preamble is built as in slide 3 (pre- and post-fix)
doc.: IEEE 802.11-10/0264r3
Submission
Staw Poll Questions
• Do you support inclusion of the technique,– Golay complementary pair with maximum length zero-correlation
zone for the estimation of the channel response and IQ imbalance
• as described in 10/0264r3 in the TGad draft amendment?
March 2010
André Bourdoux, IMECSlide 16
doc.: IEEE 802.11-10/0264r3
Submission
March 2010
André Bourdoux, IMECSlide 17
References
• 11-09-0296-16-00ad-evaluation-methodology.doc
• 11-09-0228-05-00ad-functional-requirements.doc
• IEEE Std 802.15.3c™-2009
• IEEE P802.15.3c/DF3
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