Apparatus and method for canceling interference in relay station in a communication system
A method and apparatus for canceling interference between a transmission signal and a received signal in a full-duplex RS in a communication system are provided, in which an RF/IF signal received from a first node through an antenna is converted to a baseband received signal, demodulated and decoded, a baseband transmission signal is generated by encoding and decoding the decoded data, a baseband interference estimate is calculated using the baseband received signal and the baseband transmission signal, a baseband interference is eliminated from the baseband received signal according to the baseband interference estimate, the baseband transmission signal is converted to an RF/IF transmission signal for a second node, an RF/IF interference estimate is calculated by converting amplitude of the RF/IF transmission signal and delaying it, and an RF/IF interference is eliminated from the RF/IF received signal according to the RF/IF interference estimate.
1. A method for canceling interference between a transmission signal and a received signal in a full-duplex relay station (RS) in a communication system, comprising:
converting a radio frequency/intermediate frequency (RF/IF) signal received from a first node through an antenna to a baseband received signal;
demodulating and decoding the baseband received signal;
generating a baseband transmission signal by encoding and modulating the demodulated and decoded data;
calculating a baseband interference estimate using the baseband received signal and the baseband transmission signal;
eliminating a baseband interference from the baseband received signal using the baseband interference estimate;
converting the baseband transmission signal to an RF/IF transmission signal to be transmitted to a second node;
calculating an RF/IF interference estimate by converting amplitude of the RF/IF transmission signal and delaying the RF/IF transmission signal with the converted amplitude by a predetermined time period; and
eliminating an RF/IF interference from the RF/IF received signal according to the RF/IF interference estimate.
2. The method of claim 1 , wherein the RF/IF interference estimate calculation comprises determining the RF/IF interference estimate according to the RF/IF transmission signal and a control value based on the baseband interference.
3. The method of claim 1 , wherein the baseband interference estimate calculation comprises calculating the baseband interference estimate by averaging interference channel estimates calculated for one of a time period and a frequency in which an interference channel is constant.
4. The method of claim 1 , wherein the baseband interference estimate calculation comprises calculating the baseband interference estimate by averaging interferences in a current frame k and N frames previous to the current frame k according to the following equation,
H
^
1
(
k
)
=
1
N
+
1
∑
w
=
0
N
y
(
k
-
w
)
x
H
(
k
-
w
)
x
(
k
-
w
)
2
,
where Ĥ I (k) is the baseband interference estimate, y(k) is the baseband received signal, x(k) is the baseband transmission signal, and w is a frame index.
5. The method of claim 1 , wherein the baseband interference estimate calculation comprises calculating the baseband interference estimate by averaging interferences in a current frame k, N/2 frames previous to the current frame k, and N/2 frames following the current frame k according to the following equation,
H
^
1
(
k
)
=
1
N
+
1
∑
w
=
-
N
/
2
N
/
2
y
(
k
-
w
)
x
H
(
k
-
w
)
x
(
k
-
w
)
2
,
where Ĥ I (k) is the baseband interference estimate, y(k) is the baseband received signal, x(k) is the baseband transmission signal, and w is a frame index.
6. The method of claim 1 , further comprising:
obtaining an orthogonal frequency division multiplexing (OFDM) pilot signal by fast Fourier transform (FFT)-processing the baseband received signal;
detecting channel characteristics of each subcarrier using the OFDM pilot signal; and
detecting time-domain channel characteristics by performing inverse discrete Fourier transform (IDFT)-processing on the channel characteristics of each subcarrier, for use in calculating the baseband interference estimate and the RF/IF interference estimate.
7. An apparatus for canceling interference between a transmission signal and a received signal in a full-duplex relay station (RS) in a communication system, comprising:
a receiver for receiving a radio frequency/intermediate frequency (RF/IF) signal from a first node through an antenna;
a first converter for converting the received RF/IF signal to a baseband received signal;
a reception module for demodulating and decoding the baseband received signal;
a transmission module for generating a baseband transmission signal by encoding and modulating the demodulated and decoded data;
a baseband interference controller for calculating a baseband interference estimate using the baseband received signal and the baseband transmission signal;
a second converter for eliminating a baseband interference from the baseband received signal according to the baseband interference estimate and converting the baseband transmission signal to an RF/IF transmission signal to be transmitted to a second node; and
an RF/IF interference controller for calculating an RF/IF interference estimate by converting amplitude of the RF/IF transmission signal and delaying the RF/IF transmission signal with the converted amplitude by a predetermined time period,
wherein the receiver eliminates an RF/IF interference from the RF/IF received signal according to the RF/IF interference estimate.
8. The apparatus of claim 7 , wherein the RF/IF interference controller determines the RF/IF interference estimate according to the RF/IF transmission signal and a control value based on the baseband interference.
9. The apparatus of claim 7 , wherein the baseband interference controller calculates the baseband interference estimate by averaging interference channel estimates calculated for one of a time period and a frequency in which an interference channel is constant.
10. The apparatus of claim 7 , wherein the baseband interference controller calculates the baseband interference estimate by averaging interferences in a current frame k and N frames previous to the current frame k according to the following equation,
H
^
1
(
k
)
=
1
N
+
1
∑
w
=
0
N
y
(
k
-
w
)
x
H
(
k
-
w
)
x
(
k
-
w
)
2
,
where Ĥ I (k) is the baseband interference estimate, y(k) is the baseband received signal, x(k) is the baseband transmission signal, and w is a frame index.
11. The apparatus of claim 7 , wherein the baseband interference controller calculates the baseband interference estimate by averaging interferences in a current frame k, N/2 frames previous to the current frame k, and N/2 frames following the current frame k according to the following equation,
H
^
1
(
k
)
=
1
N
+
1
∑
w
=
-
N
/
2
N
/
2
y
(
k
-
w
)
x
H
(
k
-
w
)
x
(
k
-
w
)
2
,
where Ĥ I (k) is the baseband interference estimate, y(k) is the baseband received signal, x(k) is the baseband transmission signal, and w is a frame index.
12. The apparatus of claim 7 , wherein the reception module obtains an orthogonal frequency division multiplexing (OFDM) pilot signal by fast Fourier transform (FFT)-processing the baseband received signal, detects channel characteristics of each subcarrier using the OFDM pilot signal, and detects time-domain channel characteristics by performing inverse discrete Fourier transform (IDFT) on the channel characteristics of each subcarrier, for use in calculating the baseband interference estimate and the RF/IF interference estimate.
13. A method for canceling interference between a transmission signal and a received signal in a full-duplex relay station (RS) in a communication system, comprising:
converting a radio frequency/intermediate frequency (RF/IF) received signal to a baseband received signal;
demodulating and decoding the baseband received signal;
generating a baseband transmission signal by encoding and modulating the demodulated and decoded baseband received signal;
calculating a baseband interference estimate;
subtracting the baseband interference estimate from the baseband received signal;
converting the baseband transmission signal to an RF/IF transmission signal;
calculating an RF/IF interference estimate; and
subtracting the RF/IF interference estimate from the RF/IF received signal.
14. The method of claim 13 , wherein the RF/IF interference estimate calculation comprises determining the RF/IF interference estimate according to the RF/IF transmission signal and a control value based on the baseband interference.
15. The method of claim 13 , wherein the baseband interference estimate calculation comprises calculating the baseband interference estimate by averaging interference channel estimates calculated for one of a time period and a frequency in which an interference channel is constant.
16. The method of claim 13 , wherein the baseband interference estimate calculation comprises calculating the baseband interference estimate by averaging interferences in a current frame k and N frames previous to the current frame k according to the following equation,
H
^
1
(
k
)
=
1
N
+
1
∑
w
=
0
N
y
(
k
-
w
)
x
H
(
k
-
w
)
x
(
k
-
w
)
2
,
where Ĥ I (k) is the baseband interference estimate, y(k) is the baseband received signal, x(k) is the baseband transmission signal, and w is a frame index.
17. The method of claim 13 , wherein the baseband interference estimate calculation comprises calculating the baseband interference estimate by averaging interferences in a current frame k, N/2 frames previous to the current frame k, and N/2 frames following the current frame k according to the following equation,
H
^
1
(
k
)
=
1
N
+
1
∑
w
=
-
N
/
2
N
/
2
y
(
k
-
w
)
x
H
(
k
-
w
)
x
(
k
-
w
)
2
,
where Ĥ I (k) is the baseband interference estimate, y(k) is the baseband received signal, x(k) is the baseband transmission signal, and w is a frame index.
18. The method of claim 13 , further comprising:
obtaining an orthogonal frequency division multiplexing (OFDM) pilot signal by fast Fourier transform (FFT)-processing the baseband received signal;
detecting channel characteristics of each subcarrier using the OFDM pilot signal; and
detecting time-domain channel characteristics by performing inverse discrete Fourier transform (IDFT)-processing on the channel characteristics of each subcarrier, for use in calculating the baseband interference estimate and the RF/IF interference estimate.