Method of detecting synchronization timing and sub-band based on adaptive threshold and receiver performing the same
A method of detecting synchronization timing and sub-band, includes: receiving an input signal corresponding to a training sequence; generating a template signal based on the input signal and a single reference signal; performing a matched filtering operation on the input signal based on the template signal; obtaining an adaptive threshold for detecting a target sub-band based on a result of the matched filtering operation; obtaining a peak tone for the target sub-band based on the result of the matched filtering operation; and determining whether the input signal corresponds to the target sub-band and a synchronization timing for the input signal based on the adaptive threshold and the peak tone.
1 . A method of detecting synchronization timing and a sub-band, the method comprising:
receiving an input signal corresponding to a training sequence;
generating a template signal based on the input signal and a reference signal, the reference signal being a single predetermined reference signal;
performing a matched filtering operation on the input signal based on the template signal;
calculating an adaptive threshold for detecting a target sub-band among a plurality of sub-bands based on a result of the matched filtering operation;
calculating a peak tone for the target sub-band based on the result of the matched filtering operation; and
determining whether the input signal corresponds to the target sub-band and a synchronization timing for the input signal based on the adaptive threshold and the peak tone.
2 . The method of claim 1 , wherein the adaptive threshold is calculated by windowing a part of the input signal and has a variable value depending on the input signal.
3 . The method of claim 2 , wherein calculating the adaptive threshold includes:
measuring noise power by performing a windowing operation around a target position of the input signal; and
obtaining the adaptive threshold based on the noise power.
4 . The method of claim 3 , wherein the noise power and the adaptive threshold are obtained based on Equation 1 and Equation 2, respectively,
Q
b
(
n
)
=
1
L
win
∑
l
=
L
shift
L
win
+
L
shift
-
1
❘
"\[LeftBracketingBar]"
a
y
,
b
(
l
)
❘
"\[RightBracketingBar]"
=
∼
E
{
❘
"\[LeftBracketingBar]"
a
y
,
b
(
n
)
❘
"\[RightBracketingBar]"
n
≠
0
}
[
Equation
1
]
T
b
(
n
)
=
❘
"\[LeftBracketingBar]"
a
y
,
b
(
0
)
❘
"\[RightBracketingBar]"
+
❘
"\[LeftBracketingBar]"
a
y
,
b
(
n
)
❘
"\[RightBracketingBar]"
n
≠
0
2
=
β
+
γ
·
Q
b
(
n
)
[
Equation
2
]
where Q b (n) denotes the noise power, T b (n) denotes the adaptive threshold, n denotes a sample index, L win denotes a window size for the windowing operation, L shift denotes a shift value for the windowing operation, |a y,b (0)| and |a y,b (n)| n≠0 denote cross-correlation function (CCF) values, and β and γ denote constant values.
5 . The method of claim 3 ,
wherein a plurality of sampling values and a plurality of sample indices associated with the plurality of sampling values are obtained by sampling the input signal, and
wherein the target position of the input signal corresponds to one of the plurality of sample indices.
6 . The method of claim 1 , wherein the peak tone is obtained based on Equation 3,
P
b
(
0
)
=
N
MF
N
B
∑
l
=
0
L
target
-
1
❘
"\[LeftBracketingBar]"
h
b
[
l
]
❘
"\[RightBracketingBar]"
2
[
Equation
3
]
where P b (0) denotes the peak tone, N MF denotes a length of filter coefficients for the matched filtering operation, N B denotes a number of valid sub-bands included in a wideband, L target denotes a window size for a windowing operation, and h b (·) denotes an impulse response of a sub-band channel.
7 . The method of claim 1 , wherein generating the template signal includes:
calling a look-up table (LUT) corresponding to the reference signal, the look-up table being a single look-up table;
obtaining a frequency bandwidth of the input signal;
obtaining a sub-band index of the input signal; and
obtaining the template signal based on the look-up table, the frequency bandwidth and the sub-band index.
8 . The method of claim 7 ,
wherein filter coefficients for the matched filtering operation correspond to complex numbers, and
wherein the look-up table includes only real numbers.
9 . The method of claim 8 , wherein the look-up table is formed in a ternary scheme such that each of the real numbers included in the look-up table correspond to one of +1, 0 and −1.
10 . The method of claim 7 , wherein obtaining the template signal includes:
calculating an index of a real number part of the template signal;
calculating an index of an imaginary number part of the template signal;
calculating a sign of the real number part of the template signal; and
calculating a sign of the imaginary number part of the template signal.
11 . The method of claim 10 , wherein the real number part of the template signal and the imaginary number part of the template signal are obtained based on Equation 4 and Equation 5, respectively,
RE
(
x
N
,
b
(
n
)
)
=
R
(
IDX
RE
(
N
Max
N
n
,
b
)
,
n
)
×
S
RE
(
N
Max
N
n
,
b
)
[
Equation
4
]
IM
(
x
N
,
b
(
n
)
)
=
R
(
IDX
IM
(
N
Max
N
n
,
b
)
,
n
)
×
S
IM
(
N
Max
N
n
,
b
)
[
Equation
5
]
where x N,b (n) denotes the template signal, n denotes a sample index, RE(·) denotes a function of obtaining the real number part, IM(·) denotes a function of obtaining the imaginary number part, R(m,n) denotes a real number included in the look-up table, IDX RE (·) denotes the index of the real number part of the template signal, IDX IM (·) denotes the index of the imaginary number part of the template signal, S RE (·) denotes the sign of the real number part of the template signal, S IM (·) denotes the sign of the imaginary number part of the template signal, N Max denotes a maximum number of sub-bands included in a wideband, N denotes a number of samples, and b denotes the sub-band index of the input signal.
12 . The method of claim 1 , wherein determining whether the input signal corresponds to the target sub-band and the synchronization timing for the input signal includes:
in response to the peak tone being greater than the adaptive threshold, detecting the target sub-band; and
in response to the peak tone being greater than the adaptive threshold, setting the synchronization timing for the input signal based on the target sub-band.
13 . The method of claim 1 , further comprising:
setting a valid range based on the result of the matched filtering operation, and
wherein calculating the adaptive threshold, calculating the peak tone, and determining whether the input signal corresponds to the target sub-band and the synchronization timing for the input signal are performed only on the valid range.
14 . The method of claim 1 ,
wherein the input signal is received through a wireless channel of a wireless communication system,
wherein the wireless channel has a frequency bandwidth of a wideband including the plurality of sub-bands, and
wherein the target sub-band is determined from among the plurality of sub-bands.
15 . The method of claim 14 ,
wherein the template signal includes:
a first template signal corresponding to a first sub-band among the plurality of sub-bands; and
a second template signal corresponding to a second sub-band different from the first sub-band among the plurality of sub-bands, and
wherein both the first template signal and the second template signal are generated based on the reference signal.
16 . The method of claim 14 , wherein, in response to the input signal corresponding to two or more sub-bands among the plurality of sub-bands, the synchronization timing for the input signal is determined based on all of the two or more sub-bands.
17 . A receiver comprising:
a template generator configured to generate a template signal based on an input signal and a reference signal, the input signal corresponding to a training sequence, the reference signal being a single predetermined reference signal;
a first calculator configured to receive the input signal, and to perform a matched filtering operation on the input signal based on the template signal; and
a second calculator configured to calculate an adaptive threshold for detecting a target sub-band among a plurality of sub-bands based on a result of the matched filtering operation, to calculate a peak tone for the target sub-band based on the result of the matched filtering operation, and to determine whether the input signal corresponds to the target sub-band and a synchronization timing for the input signal based on the adaptive threshold and the peak tone.
18 . The receiver of claim 17 , wherein the template generator includes:
a storage unit configured to store a look-up table corresponding to the reference signal, the look-up table being a single look-up table;
a sub-band selecting unit configured to obtain a sub-band index of the input signal; and
a template obtaining unit configured to obtain the template signal based on the look-up table, a frequency bandwidth of the input signal and the sub-band index.
19 . The receiver of claim 17 , wherein the second calculator includes:
a threshold calculating unit configured to calculate the adaptive threshold based on the result of the matched filtering operation;
a peak tone calculating unit configured to calculate the peak tone based on the result of the matched filtering operation; and
a detecting and setting unit configured to determine whether the input signal corresponds to the target sub-band and the synchronization timing for the input signal based on the adaptive threshold and the peak tone.
20 . A method of detecting synchronization timing and sub-band, the method comprising:
receiving an input signal corresponding to a training sequence;
generating a template signal based on the input signal and a reference signal, the reference signal being a single reference signal;
performing a matched filtering operation on the input signal based on the template signal;
setting a valid range based on a result of the matched filtering operation;
calculating an adaptive threshold for detecting a target sub-band based on the result of the matched filtering operation and the valid range;
calculating a peak tone for the target sub-band based on the result of the matched filtering operation and the valid range; and
determining whether the input signal corresponds to the target sub-band and a synchronization timing for the input signal based on the adaptive threshold and the peak tone,
wherein calculating the adaptive threshold includes:
measuring noise power by performing a windowing operation around a target position of the input signal; and
obtaining the adaptive threshold based on the noise power, and
wherein generating the template signal includes:
calling a pre-stored look-up table (LUT) corresponding to the reference signal, the look-up table being a single look-up table;
obtaining a frequency bandwidth of the input signal;
obtaining a sub-band index of the input signal; and
obtaining the template signal based on the look-up table, the frequency bandwidth and the sub-band index.