Multipath searching method and multipath searcher
View Patent ↗Embodiments of the present invention provide a multipath searching method and a multipath searcher, to improve accuracy of delay estimation, thereby improving performance of a receiver. The method includes: performing processing on received signals r i (t) and pilot sequences p i (t) to obtain upsampling signals y(τ); subtracting contribution values of a current multipath waveform to other multipath waveforms by using a raised cosine function with a peak position set to zero and according to a global maximum value of |y(τ)| 2 and a total of M sampling points {circumflex over (τ)} 1 (m) near the global maximum value, to obtain an upsampling signal y L (τ) having a minimum residual in M groups of upsampling signals y L (m) (τ); and obtaining a time delay power spectrum of the upsampling signal y L (τ) having the minimum residual.
1. A multipath searching method, comprising:
performing processing on received signals r i (t) and pilot sequences p i (t) to obtain upsampling signals y(τ);
subtracting contribution values of a current multipath waveform to other multipath waveforms by using a raised cosine function with a peak position set to zero and according to a global maximum value of |y(τ)| 2 and a total of M sampling points {circumflex over (τ)} 1 (m) near the global maximum value, to obtain an upsampling signal y L (τ) having a minimum residual in M groups of upsampling signals y L (m) (τ), wherein M is an integer greater than or equal to 1, and |y(τ)| 2 is a squared absolute value of y(τ); and
obtaining a time delay power spectrum of the upsampling signal y L (τ) having the minimum residual.
2. The method according to claim 1 , wherein the performing processing on received signals r i (t) and pilot sequences p i (t) to obtain upsampling signals y(τ) comprises:
performing correlation on the received signals r i (t) and the pilot sequences p i (t), to obtain
y
i
(
τ
)
=
∑
t
=
0
N
-
1
r
i
(
t
+
τ
)
p
i
*
(
t
)
,
wherein p i *(t) represents a complex conjugate of the pilot sequences p i (t);
performing coherent accumulation on y i (τ) on I pilot symbols to obtain
y
c
(
τ
)
=
∑
i
=
0
I
-
1
y
i
(
τ
)
,
wherein I is a positive integer; and
performing upsampling and filtering on y c (τ) to obtain y(τ).
3. The method according to claim 1 , wherein the subtracting contribution values of a current multipath waveform to other multipath waveforms by using a raised cosine function with a peak position set to zero and according to a global maximum value of |y(τ)| 2 and a total of M sampling points {circumflex over (τ)} 1 (m) near the global maximum value, to obtain an upsampling signal y L (τ) having a minimum residual in M groups of upsampling signals y L (m) (τ) comprises:
searching |y(τ)| 2 for a position {circumflex over (τ)} g of the global maximum value of |y(τ)| 2 ;
taking a total of M sampling points {circumflex over (τ)} 1 (m) at the position {circumflex over (τ)} g and near the position {circumflex over (τ)} g , obtaining the M groups of upsampling signals y L (m) (τ) through an iteration operation, and calculating residuals of the M groups of y L (m) (τ); and
comparing the M residuals to obtain the upsampling signal y L (τ) having the minimum residual in the M groups of y L (m) (τ).
4. The method according to claim 3 , wherein the taking a total of M sampling points {circumflex over (τ)} 1 (m) at the position {circumflex over (τ)} g and the near position {circumflex over (τ)} g , obtaining the M groups of upsampling signals y L (m) (τ) through an iteration operation, and calculating residuals of the M groups of y L (m) (τ) comprises:
taking M sampling points in [{circumflex over (τ)} g −Δτ, {circumflex over (τ)} g +Δτ];
performing an iteration operation on each sampling point {circumflex over (τ)} 1 (m) of the M sampling points according to formulas y l (m) (τ)=y l-1 (m) (τ)−y l-1 (m) ({circumflex over (τ)} l-1 (m) )R(τ−{circumflex over (τ)} l-1 (m) ) and
τ
^
l
(
m
)
=
arg
max
τ
y
l
(
m
)
(
τ
)
2
,
to obtain the M groups of upsampling signals y L (m) (τ), wherein R(τ) represents a raised cosine wave function with a peak position set to zero, l takes a value of 2, 3, . . . , L, and m takes a value of 1, 2, 3, . . . , M; and
calculating a residual for each group of upsampling signals y L (m) (τ) according to a formula
e
(
m
)
=
∑
τ
,
τ
≠
τ
^
l
(
m
)
y
L
(
m
)
(
τ
)
2
.
5. The method according to claim 4 , wherein the obtaining a time delay power spectrum of the upsampling signal y L (τ) having the minimum residual comprises:
performing incoherent accumulation on z j (τ)=|y L (τ)| 2 on J time slots according to
z
(
τ
)
=
∑
j
=
0
J
-
1
z
j
(
τ
)
,
wherein J is an integer greater than or equal to 1; and
performing filtering on z(τ) according to ν n (τ)=αν n-1 (τ)+(1−α)z(τ) to obtain a time delay power spectrum ν n (τ), wherein α has a value range of 0<α<1.
6. A multipath searcher, comprising:
a pre-processing module, configured to perform processing on received signals r i (t) and pilot sequences p i (t) to obtain upsampling signals y(τ);
a minimum residual obtaining module, configured to subtract contribution values of a current multipath waveform to other multipath waveforms by using a raised cosine function with a peak position set to zero and according to a global maximum value of |y(τ)| 2 and M sampling points {circumflex over (τ)} 1 (m) near the global maximum value, to obtain an upsampling signal y L (τ) having a minimum residual in M groups of upsampling signals y L (m) (τ), wherein M is an integer greater than or equal to 1, and |y(τ)| 2 is a squared absolute value of y(τ); and
a time delay power spectrum obtaining module, configured to obtain a time delay power spectrum of the upsampling signal y L (τ) having the minimum residual.
7. The multipath searcher according to claim 6 , wherein the pre-processing module comprises:
a correlator, configured to perform correlation on the received signals r i (t) and the pilot sequences p i (t), to obtain
y
i
(
τ
)
=
∑
t
=
0
N
-
1
r
i
(
t
+
τ
)
p
i
*
(
t
)
,
wherein p i *(t) represents a complex conjugate of the pilot sequences p i (t);
a coherent accumulator, configured to perform coherent accumulation on y i (τ) on I pilot symbols to obtain
y
c
(
τ
)
=
∑
i
=
0
I
-
1
y
i
(
τ
)
,
wherein I is a positive integer; and
a sampling and filtering unit, configured to perform upsampling and filtering on y c (τ) to obtain y(τ).
8. The multipath searcher according to claim 6 , wherein the minimum residual obtaining module comprises:
a maximum value searching submodule, configured to search |y(τ)| 2 for a position {circumflex over (τ)} g of the global maximum value of |y(τ)| 2 ;
an iteration submodule, configured to take a total of M sampling points {circumflex over (τ)} 1 (m) at the position {circumflex over (τ)} g and near the position {circumflex over (τ)} g , obtain the M groups of upsampling signals y L (m) (τ) through an iteration operation, and calculate residuals of the M groups of y L (m) (τ); and
a comparing submodule, configured to compare the M residuals to obtain the upsampling signal y L (τ) having the minimum residual in the M groups of y L (m) (τ).
9. The multipath searcher according to claim 8 , wherein the iteration submodule comprises:
a sampling unit, configured to take M sampling points in [{circumflex over (τ)} g −Δτ, {circumflex over (τ)} g +Δτ];
an iteration unit, configured to perform an iteration operation on each sampling point {circumflex over (τ)} l (m) of the M sampling points according to formulas y l (m) (τ)=y l-1 (m) (τ)−y l-1 (m) ({circumflex over (τ)} l-1 (m) )R(τ−{circumflex over (τ)} l-1 (m) ) and
τ
^
l
(
m
)
=
arg
max
τ
y
l
(
m
)
(
τ
)
2
,
to obtain the M groups of upsampling signals y L (m) (τ), wherein R(τ) represents a raised cosine wave function with a peak position set to zero, l takes a value of 2, 3, . . . , L, and m takes a value of 1, 2, 3, . . . , M; and
a residual calculating unit, configured to calculate a residual for each group of y L (m) (τ) according to a formula
e
(
m
)
=
∑
τ
,
τ
≠
τ
^
l
(
m
)
y
L
(
m
)
(
τ
)
2
.
10. The multipath searcher according to claim 9 , wherein the time delay power spectrum obtaining module comprises:
an incoherent accumulator, configured to perform incoherent accumulation on z j (τ)=|y(τ)| 2 on J time slots according to
z
(
τ
)
=
∑
j
=
0
J
-
1
z
j
(
τ
)
,
wherein J is an integer greater than or equal to 1; and
a filter, configured to perform filtering on z(τ) according to ν n (τ)=αΞ n-1 (τ)+(1−α)z(τ) to obtain a time delay power spectrum ν n (τ), wherein α has a value range of 0<α<1.