January 2007
doc.: IEEE 802.22-07/0033r0
Orthogonal Interference Detection for Sensing
IEEE P802.22 Wireless RANs
Date: 2007-01-13
Authors:
Name
Company
Address
Phone
email
Linjun Lv
Huawei Technologies
Shenzhen, China
0086-755-28973119
[email protected]
Soo-Young Chang
Huawei Technologies
Davis, CA, U.S.
1-916 278 6568
[email protected]
Zhou Wu
Huawei Technologies
Shenzhen, China
86-755-28979499
[email protected]
Jun Rong
Huawei Technologies
Shenzhen, China
86-755-28979499
[email protected]
Mingwei Jie
Huawei Technologies
Shenzhen, China
86-755-28972660
[email protected]
Jianwei Zhang
Huawei Technologies
Shanghai, China
86-21-68644808
[email protected]
Lai Qian
Huawei Technologies
Shenzhen, China
86-755-28973118
[email protected]
Jianhuan Wen
Huawei Technologies
Shenzhen, China
86-755-28973121
[email protected]
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>
Submission
Slide 1
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Orthogonal Interference Detection
Incumbent signal selection
interruption can be achieved.
Submission
Slide 2
without
service
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Introduction (1/2)
channel
Hk,i
Transmitter of
WRAN system
•
interference
Ik,i
noise
nk,i
OFDM
signal
Xk,i
Receiver of
WRAN system
If interference (or an incumbent user signal) exists in the frequency
domain of the received signals,
Yk ,i＝X k ,i H k ,i＋I k ,i＋n k ,i
•
Otherwise,
Yk ,i＝X k ,i H k ,i＋n k ,i
Xk,i is the symbol transmitted at time i for the kth subcarrier;
Hk,i is the channel response at time i for the kth subcarrier;
Yk,i is the received symbol at time i for the kth subcarrier;
Ik,i is the interference signal at time i for the kth subcarrier.
Submission
Slide 3
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Introduction (2/2)
• Assume in coherence time and coherence bandwidth, Hk,i is
constant.
• Assume (Qk,i, Qk,i+1) is orthogonal to transmitted data (Xk,i, Xk,i+1).
• A group of received data (Yk,i, Yk,i+1 ) are correlated with orthogonal
signal (Qk,i, Qk,i+1) .
If interference exists:
Yk ,i Qk ,i＋Yk ,i＋1Q k ,i＋1＝I k ,i Qk ,i＋I k ,i＋1Q k ,i＋1＋n k ,i Q k ,i＋n k ,i＋1Q k ,i＋1
else:
Yk ,i Q k ,i＋Yk ,i＋1Q k ,i＋1＝n k ,i Qk ,i＋n k ,i＋1Q k ,i＋1
• Determine whether interference exists using energy detection:
2
If Yk ,i Q k ,i  Yk ,i 1Q k ,i 1  T(X k ,i , X k ,i＋1 ) , interference exists,
otherwise, interference does not exist.
T (Xk,i, Xk,i+1): interference detection threshold
Submission
Slide 4
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Orthogonal Interference Detection for Multiple
Symbols
• Use multi groups of received data to increase reliability of the detection.
• Using data of N different time slots to form N-1 groups of signal
vectors,
N 1
when

i 1
Yk ,i Q k ,i  Yk ,i 1Q k ,i 1
2
T(X k ,i , X k ,i＋1 )
1
N 1
, interference exists.
• Using data of N different sub-carriers to form N-1 groups of signal
vectors,
N 1
when

k 1
Yk ,i Q k ,i  Yk 1,i Q k 1,i
T(X k ,i , X k 1,i )
N 1
Submission
2
1
, interference exists.
Slide 5
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Orthogonal Interference Detection Using Pilots
• The location of a pilot is known a priori.
• When Xk,i of a pilot is always “1” , the equation for the judgement is
N 1
 Yk ,i  Yk ,i1
2
 T(1,1)
i 1
N 1
• When Xk,i of a pilot is alternatingly “1” or “-1” ,the equation for the
judgement is
N 1
 Yk ,i＋Yk ,i1
i 1
N 1
Submission
2
 T(1,1)
Slide 6
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Orthogonal Interference Detection Using Traffic Data
• Traffic data are richer than pilots
for interference detection.
• Received symbols Yk,i are
buffered.
• Coding and modulation are
performed to get Xk,i .
– If correct in decoding ,then
detect interference based on the
algorithm mentioned in the
previous slide.
– If erroneous in decoding ,then
calculate PER (Packet Error
Rate) :
If PER>threshold, BS will
schedule quiet periods.
Submission
Slide 7
received
signal
OFDM
demodulation
decoding
coding
Interference
detection
modulation
Interference Detection at receiver
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Simulation (1/5)
Orthogonal Detection INR=30dB
detction probability
1
0.8
0.6
0.4
0.2
0
-300
-200
-100
0
100
200
subcarrier number
Accumulative Orthogonal Detection INR=30dB
-200
-100
300
detction probability
1
0.8
0.6
0.4
0.2
0
-300
0
100
subcarrier number
200
300
Detection probabilities under INR=30dB of the algorithm.
The upper figure illustrates the detection with one group of symbols while the bottom
one illustrates the detection with average of 8 groups of symbols.
Submission
Slide 8
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Simulation (2/5)
Orthogonal Detection INR=20dB
detction probability
1
0.8
0.6
0.4
0.2
0
-300
-200
-100
0
100
200
subcarrier number
Accumulative Orthogonal Detection INR=20dB
-200
-100
300
detction probability
1
0.8
0.6
0.4
0.2
0
-300
0
100
subcarrier number
200
300
Detection probabilities under INR=20dB of the algorithm.
The upper figure illustrates the detection with one group of symbols while the bottom
one illustrates the detection with average of 8 groups of symbols.
Submission
Slide 9
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Simulation (3/5)
Orthogonal Detection INR=0dB
detction probability
0.2
0.15
0.1
0.05
0
-300
-200
200
100
0
subcarrier number
Accumulative Orthogonal Detection INR=0dB
300
200
300
-100
detction probability
0.2
0.15
0.1
0.05
0
-300
-200
-100
100
0
subcarrier number
Detection probabilities under INR=0dB of the algorithm.
The upper figure illustrates the detection with one group of symbols while the bottom
one illustrates the detection with average of 8 groups of symbols.
Submission
Slide 10
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Simulation (4/5)
Detection probabilities under SNR=10dB of the algorithm.
The left and right figures illustrate the detection with one group of 24×2546 samples from two different
DTV signal files, WAS_311_36_06052000_ref and WAS_311_48_06052000_ref respectively.
Submission
Slide 11
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Simulation (5/5)
• More simulation results by different DTV signal files are in
the doc document.
Submission
Slide 12
Soo-Young Chang, Huawei Technologies
January 2007
doc.: IEEE 802.22-07/0033r0
Conclusions
• Interference detection can be done without channel
estimation.
• Interference detection can be done without service
interruption.
• Multiple groups of received data can be used to
increase detection reliability.
• Interference detection can be done using traffic data
by performing decoding and demodulation at the
receiver.
Submission
Slide 13
Soo-Young Chang, Huawei Technologies