Method for reducing self-interference signal in communications system, and apparatus
Embodiments of the present invention provide a method for reducing a self-interference signal in a communications system, and an apparatus. The method includes: sending a sounding signal and a first communication signal; receiving an input signal; separating a near-field reflection signal corresponding to the sounding signal from an echo signal of the input signal; determining, based on the near-field reflection signal, a near-field reflection channel parameter; determining, based on the near-field reflection channel parameter, a reconstructed near-field reflected self-interference signal; and subtracting the reconstructed near-field reflected self-interference signal from a received second communication signal. The present invention can effectively recognize and reconstruct a near-field reflection signal, thereby reducing a near-field reflected self-interference signal in self-interference.
1. A wireless full duplex communications apparatus, wherein the apparatus comprises:
a transmitter, configured to send a sounding signal and a first communication signal through at least one antenna wherein a timeslot used for sending the sounding signal is different from a timeslot used for sending the first communication signal, and the sounding signal is a large time-bandwidth product signal;
a receiver, configured to receive an input signal through at least one antenna, wherein the input signal comprises a second communication signal sent by another apparatus and an echo signal that corresponds to the sounding signal and the first communication signal; and
a processor, configured to separate a near-field reflection signal corresponding to the sounding signal from the echo signal, wherein
the processor is further configured to determine, based on the near-field reflection signal, a near-field reflection channel parameter; and
the processor is further configured to determine, based on the near-field reflection channel parameter, a reconstructed near-field reflected self-interference signal, and subtract the reconstructed near-field reflected self-interference signal from the second communication signal.
2. The apparatus according to claim 1 , wherein the processor is specifically configured to determine the reconstructed near-field reflected self-interference signal according to the near-field reflection channel parameter and the first communication signal, and subtract the reconstructed near-field reflected self-interference signal from the second communication signal.
3. The apparatus according to claim 1 , wherein the apparatus further comprises:
a coupler, configured to sample a signal to be sent, to obtain a self-interference radio frequency reference signal, wherein
the processor is specifically configured to determine the reconstructed near-field reflected self-interference signal according to the near-field reflection channel parameter and the self-interference radio frequency reference signal, and subtract the reconstructed near-field reflected self-interference signal from the second communication signal.
4. The apparatus according to claim 1 , wherein the transmitter is specifically configured to send the sounding signal by using a bandwidth greater than a bandwidth used for sending the first communication signal; and
the processor is specifically configured to perform matched filtering on the near-field reflection signal, to obtain a filtered near-field reflection signal, and determine the near-field reflection channel parameter according to the filtered near-field reflection signal.
5. The apparatus according to claim 1 , wherein the transmitter is specifically configured to send the sounding signal by using a bandwidth greater than or equal to a bandwidth used for sending the first communication signal; and
the processor is specifically configured to determine, by using a super-resolution delay algorithm, the near-field reflection channel parameter corresponding to the near-field reflection signal.
6. The apparatus according to claim 5 , wherein
the processor is specifically configured to determine the near-field reflection channel parameter by using the following formulas:
h
^
(
k
)
=
(
B
+
diag
{
w
(
k
)
}
)
-
1
b
,
and
w
(
k
)
=
[
1
+
κ
-
h
^
(
k
-
1
)
max
h
^
(
k
-
1
)
]
ow
(
k
-
1
)
,
wherein ĥ represents the near-field reflection channel parameter, the superscript k of ĥ (k) identifies a result of the k th iteration, B=A H A, A represents a sounding signal matrix, b=A H r, r represents the near-field reflection signal, w (k) represents a weighting vector of the k th iteration, an initial value of the weighting vector is w (0) =α1 M×1 ,1 M×1 , represents an M×1-dimension column vector whose elements are all 1, M represents a multi-path delay distribution range of a near-field reflection channel, an operator “∘” represents that elements corresponding to two vectors are multiplied, and κ, k, and α are preset positive integers used for adjusting a convergence property.
7. The apparatus according to claim 6 , wherein when B is a conjugate matrix,
the processor is specifically configured to perform calculation through iteration from m=1 to m=M by using the following formula, to obtain (B+diag {w (k) }) −1 :
B
m
-
1
=
D
m
-
1
-
w
m
(
k
)
1
+
w
m
(
k
)
d
m
-
1
,
m
m
d
m
-
1
,
m
d
m
-
1
,
m
H
,
m
=
1
,
2
,
…
,
M
wherein B m =B m-1 +w m (k) e m e m H , D m-1 =B m-1 −1 =[d m-1,1 , d m-1,2 , . . . , d m-1,M ], and especially, B 0 =B, B M −1 =(B+diag {w (k) }) −1 , is the m th column vector of a matrix D m-1 , d m-1,mm is an element in the m th row and m th column of the matrix D m-1 , and e i represents an M×1-dimension column vector in which the i th -column elements are 1 and the other elements are all 0.
8. A method for canceling a self-interference signal in a communications system, wherein the method is executed by an apparatus supporting wireless full duplex, and the method comprises:
sending a sounding signal and a first communication signal, wherein a timeslot used for sending the sounding signal is different from a timeslot used for sending the first communication signal, and the sounding signal is a large time-bandwidth product signal;
receiving an input signal, wherein the input signal comprises a second communication signal sent by another apparatus and an echo signal that corresponds to the sounding signal and the first communication signal;
separating a near-field reflection signal corresponding to the sounding signal from the echo signal;
determining, based on the near-field reflection signal, a near-field reflection channel parameter;
determining, based on the near-field reflection channel parameter, a reconstructed near-field reflected self-interference signal; and
subtracting the reconstructed near-field reflected self-interference signal from the second communication signal, wherein the second communication signal is sent by another apparatus.
9. The method according to claim 8 , wherein the determining, based on the near-field reflection channel parameter, a reconstructed near-field reflected self-interference signal comprises:
determining the reconstructed near-field reflected self-interference signal according to the near-field reflection channel parameter and the first communication signal.
10. The method according to claim 8 , wherein the method further comprises:
sampling a signal to be sent, to obtain a self-interference radio frequency reference signal, wherein
the determining, based on the near-field reflection channel parameter, a reconstructed near-field reflected self-interference signal comprises:
determining the reconstructed near-field reflected self-interference signal according to the near-field reflection channel parameter and the self-interference radio frequency reference signal.
11. The method according to claim 8 , wherein the sending a sounding signal comprises:
sending the sounding signal in a transmit timeslot in a sounding timeslot.
12. The method according to claim 11 , wherein the sending a sounding signal comprises:
stopping sending the sounding signal in an idle timeslot in the sounding timeslot, wherein the idle timeslot comprises a first silent timeslot and a second silent timeslot; and
sending the first communication signal in a data transmission timeslot.
13. The method according to claim 12 , wherein duration of the first silent timeslot is a maximum multi-path delay of the near-field reflection channel, and
a value of the second silent timeslot enables a delay of an echo component to exceed a sum of the duration of the first silent timeslot and duration of the second silent timeslot, and a power of the echo multi-path component is less than a preset threshold.