KR101172917B1 - Apparatus and method for cancellsating interference signal in a wireless communication system - Google Patents

Abstract

According to the present invention, channel estimation information is generated by estimating each channel of received signals in a wireless communication system, and the channel quality of the received signal and the interference signal are compared using the generated channel estimation information, and based on the comparison result. Determining whether to remove the interference signal, and if it is determined to remove the interference signal after detecting the interference signal from the received signals, and removes the detected interference signal from the received signals.

Interference signal, interference signal detector, interference cancellation unit, channel estimator

Description

Apparatus and method for eliminating interference in a wireless communication system {APPARATUS AND METHOD FOR CANCELLSATING INTERFERENCE SIGNAL IN A WIRELESS COMMUNICATION SYSTEM}

1A is a view schematically showing the structure of an interference signal removing device according to an embodiment of the present invention;

1B schematically illustrates signal power of a channel response according to an embodiment of the present invention;

2A is a view schematically showing the structure of an interference signal removing device according to another embodiment of the present invention;

2b schematically illustrates signal power of a channel response according to an embodiment of the present invention;

3 is a view schematically showing the structure of an interference signal removing device according to another embodiment of the present invention;

4 is a flowchart schematically showing a method for canceling interference in accordance with an embodiment of the present invention.

TECHNICAL FIELD The present invention relates to communication systems, and more particularly, to an apparatus and method for canceling interference signals in a wireless communication system.

A general wireless communication system includes a transmitter and a receiver, for example, a base station (BS) and a mobile station (MS), and communicate with a plurality of base stations that provide services to a plurality of terminals. It consists of a plurality of terminals. The base station manages a service area, that is, a cell, and communicates with terminals existing in the cell.

In the wireless communication system, active researches are being conducted to provide users with various quality of service (hereinafter referred to as 'QoS'). In addition, wireless communication systems require high-speed mass communication systems capable of processing and transmitting a variety of information such as video and wireless data beyond voice-oriented services. Accordingly, by improving system transmission efficiency, an appropriate channel coding method for improving system performance becomes an essential element.

However, unlike a wired channel environment, a wireless channel environment in a wireless communication system is multipath interference, shadowing, propagation attenuation, time varying noise, interference and fading, etc. Factors cause unavoidable errors and loss of information. The loss of information causes severe distortion in the actual transmission signal, thereby degrading the overall performance of the wireless communication system.

Among the factors that degrade the system performance, the interference signal is considered. In the wireless communication system, signals from base stations other than the signal of the base station, that is, the serving base station, which the terminal intends to receive served as interference signals to the terminal. As such, signals of base stations other than one serving base station selected by the terminal may act as interference with the serving base station signal, which may reduce the reception performance of the signal in the entire system. If the terminal is located in a region where cells managed by the base stations overlap or in a cell boundary region, the degradation of signal reception due to the signal interference is further increased.

In particular, a system having a frequency reuse factor of 1 for improving frequency efficiency and easily using cell planning in the wireless communication system will be described as an example. As described above, in a system having a frequency reuse coefficient of 1, all base stations have a feature of excellent frequency efficiency due to the use of the same center frequency, but this causes a performance degradation problem due to intercell interference signals. In addition, the terminals located in the cell overlap region or the cell boundary region have a problem in that the reception effect is greatly deteriorated due to the increased influence of the interference signal.

Meanwhile, in a wireless communication system, in order to improve the problems caused by the interference signal, for example, a base station transmission signal transmitted to terminals in a cell boundary region is modulated using a low modulation order such as QPSK, and a low code rate. We also use up to six iterations. However, despite the above-described method, there is a problem that signal reception performance is still deteriorated when a conventional receiver, that is, a terminal is used on a fading channel.

Therefore, there is a need for a method for improving the degradation of reception performance due to an interference signal that a receiver, that is, a terminal does not want to receive in a wireless communication system.

Accordingly, an object of the present invention is to provide an apparatus and method for removing interference signal in a wireless communication system.

Another object of the present invention is to provide an interference signal canceling apparatus and method for improving reception performance in a receiver in a wireless communication system.

The method of the present invention for achieving the above objects; A method of canceling an interference signal in a wireless communication system, the method comprising: estimating each channel of received signals to generate channel estimation information, and comparing channel quality of a signal to be received with an interference signal using the generated channel estimation information And determining whether to remove the interference signal based on a comparison result, detecting the interference signal from the received signals when determining to remove the interference signal, and detecting the detected interference signal from the received signals. It includes the process of removing.

The apparatus of the present invention for achieving the above objects; An apparatus for removing interference signals in a wireless communication system, the method comprising: estimating each channel of received signals to generate channel estimation information, and comparing the channel quality of the interference signal with the received signal using the generated channel estimation information, A channel estimator for determining whether to remove the interference signal based on a comparison result, an interference signal detector for detecting the interference signal from the received signals when the channel estimator determines to remove the interference signal, and the received signal And an interference signal removing unit for removing the detected interference signal from the plurality of signals, and a signal detection unit detecting a received signal from which the interference signal has been removed.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to distract from the gist of the present invention.

The present invention proposes an apparatus and method for performing interference signal cancellation in a wireless communication system. To this end, the receiver of the present invention receives a signal, demodulates the received signal, and estimates each channel of the demodulated received signals to generate channel estimation information. And using the generated channel estimation information, comparing the received signal with the channel quality of the interference signal to determine whether to remove the interference signal, and when removing the interference signal, after detecting the interference signal from the demodulated received signal, demodulating the demodulation signal. The interference signal is removed from the received signal.

In the present invention, the operation of the transmitter and the receiver of the wireless communication system will be described. The transmitter may be a base station and the receiver may be a terminal. Hereinafter, the present invention will be described based on the operation of a receiver that receives a signal of transmitters including an interference signal.

1A is a diagram schematically illustrating a structure of an interference signal removing device according to an embodiment of the present invention.

Referring to FIG. 1A, a structure of a receiver for receiving signals from transmitter 1 110 and transmitter 2 120 is illustrated. The receiver includes a demodulator 140, an interference signal canceller 150, a signal detector 160, and a channel estimator 170. The interference signal remover 150 includes an adder 151, a switch 153, an interference signal detector 155, and an interference remover 157. The channel estimator 170 includes a first channel estimator 171, a channel quality comparator 173, and a second channel estimator 175.

을 통해 상기 S1을 수신기로 전송하며, 상기 송신기 2(120)는 채널

를 통해 상기 S2를 수신기로 전송한다. Here, the receiver receives S1 which is a transmission signal of the transmitter 1 110 and S2 which is a transmission signal of the transmitter 2 120 through a reception antenna. At this time, the transmitter 1 (110) is a channel

The S1 is transmitted to the receiver through the transmitter, and the transmitter 2 120 is a channel.

The S2 is transmitted to the receiver through.

On the other hand, if the receiver (desired signal) that the receiver actually wants to receive (S1), the S2 received by the receiver acts as an interference signal to the receiver. Accordingly, a process of demodulating a received signal when the receiver has one interference signal source, that is, one interference signal will be described with reference to FIG. 1A.

On the other hand, the demodulator 140 demodulates the received signal, that is, S1 and S2 received through the receiving antenna, and the demodulated signal is input to the interference signal canceller 150 and the channel estimator 170. Accordingly, the first channel estimator 171 and the second channel estimator 175 estimate a channel of the demodulated signal, and the first channel estimator 171 transmits the interference signal S2 to the transmitter 2 120. Estimate the channel of. The second channel estimator 175 estimates a signal that the receiver wants to receive, that is, the channel of the transmitter 1 110 that has transmitted S1. The channel estimation information estimated by the first channel estimator 171 and the second channel estimator 175 is input to the channel quality comparator 173. The channel estimation information includes channel information for restoring a signal of each channel and channel response information for measuring channel quality of each channel.

The channel quality comparator 173 measures the channel quality of the received signals using the channel estimation information estimated by the channel estimators 171 and 175. Accordingly, the measurement of channel quality for channel quality comparison using the channel estimation information is shown in Equations 1 and 2 below.

과

는 송신기 1(110)과 송신기 2(120)의 채널 응답 정보를 사용하여 수학식 1은 채널의 놈(norm)을 계산한 수학식이며, 수학식 2는 스케일된 놈(scaled norm)을 계산하는 수학식이다. 또한 상기 수학식 2의

는 스케일링 팩터(scaling factor)를 의미한다. 상기 채널 품질 비교기(173)는 상기 채널 추정기들(171, 175)에서 추정한 채널 추정 정보를 사용하여 채널 품질 비교를 위한 채널 품질 정보를 획득한다. 상기 채널 품질 비교기(173)에서 사용하는 채널 품질 정보는 놈 또는 스케일된 놈을 사용하며, 이를 통해 신호의 수신 전력을 비교하는 것이 가능하다. 또한 채널 품질 정보는 예를 들어 캐리어 대 간섭 잡음비(CINR: Carrier to Interference Noise Ratio), 신호 대 잡음비(SNR: Signal to Noise Ratio) 등의 정보를 사용하는 것도 가능하다. 즉, 상기 채널 품질 비교기(173)는 상기 채널 추정기들(171, 175)에서 추정한 채널 추정 정보를 사용하여 수신 신호들에 대한 채널 품질을 비교한다. 따라서 상기 채널 품질 비교기(173)는 상기한 채널 응답 정보를 사용하여 신호의 수신 전력을 비교하는 것이 가능하며, 이에 상기 채널 품질 비교기(173)는 송신기 1(110)과 송신기 2(120)의 채널 품질 정보를 비교하여 간섭 제거를 위한 간섭 제거부의 동작 여부를 결정한다. 여기서 상기 채널 응답에 따른 신호 전력을 하기의 도 1b에 나타내었다. remind

and

Equation 1 is a formula for calculating a norm of a channel by using channel response information of transmitter 1 110 and transmitter 2 120, and Equation 2 is a formula for calculating a scaled norm. Expression In addition, of Equation 2

Denotes a scaling factor. The channel quality comparator 173 obtains channel quality information for channel quality comparison using the channel estimation information estimated by the channel estimators 171 and 175. The channel quality information used by the channel quality comparator 173 uses a norm or a scaled norm, and thus it is possible to compare the received power of the signals. In addition, the channel quality information may use information such as a carrier-to-interference noise ratio (CINR) and a signal-to-noise ratio (SNR). That is, the channel quality comparator 173 compares the channel quality of the received signals using the channel estimation information estimated by the channel estimators 171 and 175. Accordingly, the channel quality comparator 173 may compare the received power of the signal using the channel response information. Accordingly, the channel quality comparator 173 is a channel of the transmitter 1 110 and the transmitter 2 120. The quality information is compared to determine whether to operate the interference canceling unit for interference cancellation. The signal power according to the channel response is shown in FIG. 1B below.

1B is a diagram schematically illustrating signal power of a channel response according to an embodiment of the present invention.

Referring to FIG. 1B, the signal power according to the channel response to the transmission signal S1 and the channel response to the transmission signal S2 is shown based on a time or frequency axis. Accordingly, when the signal power of the interference signal S2 is greater than the signal power according to the channel response of the signal S1 to be received by the receiver, the channel quality comparison unit 173 controls to turn on the operation of the interference cancellation unit 150. do. However, on the contrary, when the signal power of S1 is greater than the signal power of S2, the operation of the interference canceling unit 150 is controlled to be turned off. In addition, the channel quality comparison unit 173 sets a reference value according to the signal powers of the S1 and S2 so that the difference between the signal powers of the S1 and S2 exceeds a predetermined reference value. It may be determined whether it is ON / OFF.

The channel quality comparator 173 compares channel quality between a signal to be received and interference signals using the channel estimation information to determine whether to remove the interference signal. In this case, the channel quality information, that is, the signal strength is compared using the channel estimation information, that is, the channel estimation information. Alternatively, the channel estimation information is used to determine whether to control the interference signal using channel quality information, that is, channel quality information of carrier to interference noise ratio or signal to interference ratio. In this case, as described above, the channel quality comparator 173 does not operate the interference canceller when the channel quality of S1 is superior to the channel quality of S2, and when the channel quality of S1 is worse than the channel quality of S2, the interference is performed. Control to perform the operation of the eliminator.

The interference signal detector 155 of the interference signal remover 150 receives channel estimation information from the first channel estimator 171, and detects the interference signal when the switch 153 is turned on. At this time, the signal detected by the interference signal detector 155 is to detect an interference signal for the receiver as S2, and the interference signal detector 155 detects the detected S2, that is, the interference signal by the interference signal canceller 157. Will output

The interference signal canceller 157 receives the interference signal detected from the interference signal detector 155 and receives channel estimation information from the first channel estimator 171. The interference signal canceller 157 regenerates the interference signal and outputs the interference signal to the switch 153. When the switch 153 is turned on, the adder 151 removes the interference signal S2 from the signal demodulated through the demodulator 140 through the interference signal remover 157.

The signal detector 160 receives channel estimation information from the second channel estimator 175, and detects the signal S1 from which the interference signal is removed when the switch 153 is turned on and the interference signal is removed. On the other hand, the switch 153 operates through a control signal of the channel quality comparator 173, that is, an on / off signal, and when the switch 153 is off, the signal detector 160 performs an interference signal. S1 is detected without removal.

Although FIG. 1 illustrates the case where there is one interference signal, a case where two or more interference signals are described will be described with reference to FIG. 2.

2A is a diagram schematically illustrating a structure of an interference signal removing apparatus according to another embodiment of the present invention.

Referring to FIG. 2A, a structure of a receiver that receives signals from transmitter 1 210 and transmitter 2 220 is shown. The receiver includes a demodulator 240, an interference signal canceller 250 and 260, a signal detector 270, and a channel estimator 280. The first interference signal canceller 250 includes a first adder 251, a first switch 253, a first interference signal detector 255, and a first interference canceller 257. Rejection 260 includes an Mth adder 261, an Mth switch 263, an Mth interference signal detector 265, and an Mth interference canceller 267. The channel estimator 280 includes a first channel estimator 281, a channel quality comparator 283, and a second channel estimator 285.

을 통해 상기 S1을 수신기로 전송하고, 상기 송신기 2(220)는 채널

를 통해 상기 S2를 수신기로 전송하고, 상기 송신기 M(230)은 채널

을 통해 상기 SM을 수신기로 전송한다. Here, the receiver receives S1, which is a transmission signal of the transmitter 1 210, S2, which is a transmission signal of the transmitter 2 220, and SM, which is a transmission signal of the transmitter M 230, through a reception antenna. At this time, the transmitter 1 210 is a channel

The S1 is transmitted to the receiver through the transmitter, and the transmitter 2 220 is a channel

The S2 is transmitted to the receiver through the transmitter, and the transmitter M 230 is a channel

The SM is transmitted to the receiver through.

On the other hand, if the signal actually received by the receiver is S1, the S2 and SM received by the receiver act as an interference signal to the receiver. Here, M denotes an index according to a transmission signal transmitted from a plurality of transmitters, and means a constant that can vary according to the increase or decrease of the interference signal. Accordingly, a process of demodulating a received signal when the receiver has an interference signal source, that is, M-1 will be described with reference to FIG. 1A.

On the other hand, the demodulator 240 demodulates the received signal, that is, S1, S2, SM received through the receiving antenna, the demodulated signal is the first interference signal canceller 250 and the channel estimator 280 Is entered. Accordingly, the first channel estimator 281, the M-th channel estimator 285, and the second channel estimator 287 estimate a channel of the demodulated signal, and the first channel estimator 281 determines the interference signal S2. Estimate the channel of the transmitter 2 (220) that transmits. The M-th channel estimator 285 estimates a channel of the transmitter M 230 that has transmitted the interference signal SM, and the second channel estimator 287 transmits a signal that the receiver intends to receive, that is, S1. Estimate the channel of one transmitter 1 (210). The channel estimation information estimated by the first channel estimator 281, the Mth channel estimator 285, and the second channel estimator 285 is input to the channel quality comparator 283. The channel estimation information includes channel information for restoring a signal of each channel and channel response information for measuring channel quality of each channel.

The channel quality comparator 283 measures channel quality of the received signals using the channel estimation information estimated by the channel estimators 281, 285, and 287. Accordingly, the measurement of channel quality for channel quality comparison using the channel estimation information is shown in Equations 3 and 4 below.

,

,

은 송신기 1(210), 송신기 2(220), 송신기 M(230)의 채널 응답 정보를 사용하여 수학식 3은 채널의 놈(norm)을 계산한 수학식이며, 수학식 4 는 스케일된 놈(scaled norm)을 계산하는 수학식이다. 또한 상기 수학식 4의

는 스케일링 팩터(scaling factor)를 의미한다. 상기 채널 품질 비교기(283)는 상기 채널 추정기들(281, 285, 287)에서 추정한 채널 추정 정보를 사용하여 채널 품질 비교을 위한 채널 품질 정보를 획득한다. 상기 채널 품질 비교기(283)에서 사용하는 채널 품질 정보는 놈 또는 스케일된 놈을 사용하며, 이를 통해 신호의 수신 전력을 비교하는 것이 가능하다. 또한 채널 품질 정보는 예를 들어 캐리어 대 간섭 잡음비(CINR: Carrier to Interference Noise Ratio), 신호 대 잡음비(SNR: Signal to Noise Ratio) 등의 정보를 사용하는 것도 가능하다. 즉, 상기 채널 품질 비교기(283)는 상기 채널 추정기들(281, 285, 287)에서 추정한 채널 추정 정보를 사용하여 수신 신호들에 대한 채널 품질을 비교한다. 따라서 상기 채널 품질 비교기(283)는 상기한 채널 응답 정보를 사용하여 신호의 수신 전력을 비교하는 것이 가능하며, 이에 상기 채널 품질 비교기(283)는 송신기 1(210), 송신기 2(220), 송신기 M(230)의 채널 품질 정보를 비교하여 간섭 제거를 위한 간섭 제거부의 동작 여부를 결정한다. 여기서 상기 채널 응답에 따른 신호 전력을 하기의 도 2b에 나타내었다. remind

,

,

Equation 3 is a formula for calculating a norm of a channel using channel response information of transmitter 1 210, transmitter 2 220, and transmitter M 230, and Equation 4 is scaled norm. norm) is a mathematical expression. In addition, Equation 4

Denotes a scaling factor. The channel quality comparator 283 obtains channel quality information for channel quality comparison using the channel estimation information estimated by the channel estimators 281, 285, and 287. The channel quality information used by the channel quality comparator 283 uses a norm or a scaled norm, and thus it is possible to compare the received power of the signals. In addition, the channel quality information may use information such as a carrier-to-interference noise ratio (CINR) and a signal-to-noise ratio (SNR). That is, the channel quality comparator 283 compares channel quality of the received signals using the channel estimation information estimated by the channel estimators 281, 285, and 287. Accordingly, the channel quality comparator 283 may compare the received power of the signal using the channel response information. Accordingly, the channel quality comparator 283 may be a transmitter 1 210, a transmitter 2 220, or a transmitter. The channel quality information of the M 230 is compared to determine whether to operate the interference canceller for interference cancellation. Here, signal power according to the channel response is shown in FIG. 2B.

2B schematically illustrates signal power of a channel response according to an embodiment of the present invention.

Referring to FIG. 2B, the signal power according to the channel response to the transmission signal S1, the channel response to the transmission signal S2, the channel response to the transmission signal S3, and the channel response to the transmission signal SM is shown based on time or frequency axis. It is. Accordingly, in the channel quality comparison unit 283, when any one of the interference signals, S2, S3, and SM has a signal power larger than the signal power according to the channel response of the signal S1 to be received by the receiver, the interference cancellation units The operation of the operations 250 and 270 is all turned on. Alternatively, it is possible to control to selectively turn on the operation of the interference canceller corresponding to the signal power greater than the signal power of S1. On the contrary, when the signal power of S1 is greater than the signal power of S2, S3, and SM, the operation of the interference canceling units 250 and 260 is turned off. In addition, the channel quality comparison unit 283 sets a predetermined reference value according to the signal power between the S1, S2, S3, and SM so that the difference in signal power between S1, S2, S3, and SM exceeds the predetermined reference value. It may be determined whether the interference canceling units 250 and 260 are turned on or off.

In addition, the channel quality comparator 263 has the largest received power of S2 in the section “1”, the section “2”, the section “3”, the section “4”, and the section “5”. It can be turned on. Also, in the section "1", the operation of controlling the interference canceling unit for removing the signal of S3 is turned on, and in the section "2", the operation of the interference canceling unit for removing the signal of S2 and S3 is turned on, and in the section "3". "Controls to turn on the operation of the interference canceling unit which removes the signals of S2, S3 and SM, and in section" 4 "controls to turn on the operation of the interference cancellation unit to remove the signals of S2 and S3, and section" 5 &Quot; controls to turn on the operation of the interference canceling unit that removes the signal of S3.

The channel quality comparator 283 compares channel quality between a signal to be received and interference signals using the channel estimation information to determine whether to remove the interference signal. In this case, the channel quality information, that is, the signal strength is compared using the channel estimation information, that is, the channel estimation information. Alternatively, the channel estimation information is used to determine whether to control an interference signal using channel quality information, that is, channel quality information of carrier to interference noise ratio or signal to interference ratio. In this case, the channel quality comparator 283 As described above, when the channel quality of S1 is better than the channel quality of S2, S3, SM, the interference canceller is not operated. When the channel quality of S1 is worse than the channel quality of S2, S3, SM, Control to perform the operation.

When the first interference signal detector 255 of the first interference signal canceller 250 receives channel estimation information from the first channel estimator 281, and the first switch 253 is turned on, Detect interfering signals. At this time, the signal detected by the first interference signal detector 255 is to detect an interference signal for the receiver as S2, and the first interference signal detector 255 detects the detected S2, that is, the interference signal, as the first interference. Output to signal remover 257.

The first interference signal canceller 257 receives the interference signal detected from the first interference signal detector 255 and receives channel estimation information from the first channel estimator 271. Accordingly, the first interference signal canceller 257 regenerates the interference signal S2 and outputs the interference signal S2 to the first switch 253. When the first switch 253 is ON, the first adder 257 receives the interference signal S2 from the signal demodulated by the first demodulator 240 through the first interference signal canceller 257. Remove

The M-th interference signal canceller 260 performs an operation similar to that of the first interference signal canceller 250, and the M-th interference signal canceller 260 performs an Mth operation from the M-th channel estimator 285. Receives channel estimation information, detects an SM signal, and removes the SM included in the signal received by the receiver. Since a specific operation of the M-th interference signal canceller performs an operation similar to that of the first interference signal remover 250, a detailed description thereof will be omitted.

In addition, when the interference signal increases between the first interference signal remover 250 and the M-th interference signal remover 260, an interference signal remover for removing a plurality of interference signals according to the interference signal is expanded. In addition, the interference signal cancellers may be integrated into one module.

The signal detector 270 receives the channel estimation information from the second channel estimator 287, and detects the signal S1 from which the interference signals are removed when the switches 253 and 263 are turned on to remove the interference signal. . Meanwhile, the switches 253 and 263 operate through a control signal of the channel quality comparator 283, that is, an on / off signal. When the switches 253 and 263 are off, the signal detector ( 270 detects S1 without removing the interference signal.

In FIG. 2, an operation for detecting a signal from a plurality of interference signals has been described, but an operation of detecting a signal in a receiver having a plurality of reception antennas will be described with reference to FIG. 3.

3 is a diagram schematically illustrating a structure of an interference signal removing apparatus according to another embodiment of the present invention.

Referring to FIG. 3, a structure of a receiver that receives signals from transmitter 1 310 and transmitter 2 320 is shown. The receiver includes a demodulator 330, an interference signal canceller 340, a signal detector 350, and a channel estimator 360. The interference signal canceller 340 includes a first adder 341, a second adder 343, a switch 345, an interference signal detector 347, and an interference canceller 349. The channel estimator 360 includes a first channel estimator 361, a channel quality comparator 363, and a second channel estimator 365.

Here, the receiver receives S1 which is a transmission signal of the transmitter 1 310 and S2 which is a transmission signal of the transmitter 2 320 through a reception antenna. However, as the receiver uses multiple antennas, the demodulator 330 is provided with two antennas for receiving signals from both channels.

,

를 통해 상기 S1을 수신기로 전송하며, 상기 송신기 2(320)는 채널

,

를 통해 상기 S2를 수신기로 전송한다. 한편, 상기 수신기가 실제 수신하고자 하는 신호(desired signal)가 상기 S1이라 하면, 상기 수신기에 수신되는 상기 S2는 상기 수신기에게 간섭 신호로 작용한다. 이에 상기 수신기가 간섭 신호 소스 즉, 간섭 신호가 1개인 경우 수신신호를 복조하는 과정을 상기 도 3를 참조하여 설명하기로 한다. The transmitter 1 310 is a channel

,

The S1 is transmitted to the receiver through the transmitter, and the transmitter 2 320 is a channel.

,

The S2 is transmitted to the receiver through. On the other hand, if the receiver (desired signal) that the receiver actually wants to receive (S1), the S2 received by the receiver acts as an interference signal to the receiver. Accordingly, a process of demodulating a received signal when the receiver has one interference signal source, that is, one interference signal will be described with reference to FIG. 3.

On the other hand, the demodulator 330 demodulates the received signals, that is, S1 and S2 received through at least one receiving antenna, for example, the first antenna and the second antenna, and the demodulated signal is the interference signal removing unit ( 340 and the channel estimator 360.

Here, the demodulator 330 demodulates the signals received from each antenna and inputs them to the interference signal removing unit, and the interference signal removing unit decodes the signal r1 demodulating the signal of antenna 1 and the signal r2 demodulating the signal of antenna 2. Receive.

Accordingly, the first channel estimator 361 and the second channel estimator 365 estimate a channel of the demodulated signal, and the first channel estimator 361 transmits the interference signal S2. Estimate the channel of. The second channel estimator 365 estimates a signal that the receiver wants to receive, that is, the channel of the transmitter 1 310 that transmits S1. Channel estimation information estimated by the first channel estimator 361 and the second channel estimator 365 is input to a channel quality comparator 363. The channel estimation information includes channel information for restoring a signal of each channel and channel response information for measuring channel quality of each channel.

The channel quality comparator 363 measures the channel quality of the received signals using the channel estimation information estimated by the channel estimators 361 and 365. As described above, the norm or scaled norm of the channel is calculated using the channel response information of the transmitter 1 310 and the transmitter 2 320. Thus, the channel quality comparator 363 obtains channel quality information for channel quality comparison using the channel estimation information estimated by the channel estimators 361 and 365. The channel quality information used by the channel quality comparator 363 uses a norm or a scaled norm, and thus it is possible to compare the received power of the signals. In addition, the channel quality information may use information such as carrier to interference noise ratio and signal to noise ratio, for example. That is, the channel quality comparator 363 compares the channel quality of the received signals using the channel estimation information estimated by the channel estimators 361 and 365. Accordingly, the channel quality comparator 363 may compare the received power of the signal using the channel response information. Thus, the channel quality comparator 363 is a channel of the transmitter 1 310 and the transmitter 2 320. The quality information is compared to determine whether to operate the interference canceling unit for interference cancellation.

The channel quality comparison unit 363 controls the operation of the interference canceling unit 340 to be turned on when the signal power of the interference signal S2 is greater than the signal power according to the channel response of the signal S1 to be received by the receiver. . On the contrary, when the signal power of S1 is greater than the signal power of S2, the operation of the interference canceling unit 340 is controlled to be turned off. In addition, the channel quality comparison unit 363 sets a predetermined reference value according to the signal powers of the S1 and S2 so that the difference between the signal powers of the S1 and S2 exceeds a predetermined reference value. It may be determined whether it is ON / OFF.

Although the channel quality comparator 363 has been described to control whether the interference signal is controlled using the channel response information, that is, the received signal strength among the channel estimation information, the channel quality comparator 363 is used to determine whether the interference signal is controlled using the channel quality information. You can decide. The channel quality information may be compared using, for example, information such as carrier to interference noise ratio (CINR) and signal to noise ratio (SNR). In this case, as described above, the channel quality comparator 363 does not perform the operation of the interference canceller when the channel quality of S1 is superior to the channel quality of S2, and when the channel quality of S1 is worse than the channel quality of S2, the interference is performed. Control to perform the operation of the eliminator.

The interference signal detector 347 of the interference signal remover 340 receives channel estimation information from the first channel estimator 361, and detects the interference signal when the switch 345 is turned on. At this time, the signal detected by the interference signal detector 347 is to detect an interference signal for the receiver as S2, and the interference signal detector 347 transmits the detected S2, that is, the interference signal to the interference signal canceller 349. Output

The interference signal canceller 349 receives the interference signal detected from the interference signal detector 347 and receives channel estimation information from the first channel estimator 361. Accordingly, the interference signal remover 349 regenerates the interference signal and outputs the interference signal to the switch 345. When the switch 345 is turned on, the first adder 341 and the second adder 343 are interfered from the signal demodulated by the demodulator 330 through the interference signal canceller 349. Remove it.

The signal detector 350 receives channel estimation information from the second channel estimator 365, and detects the signal S1 from which the interference signal is removed when the switch 345 is turned on and the interference signal is removed. On the other hand, the switch 153 operates through a control signal of the channel quality comparator 173, that is, an on / off signal, and when the switch 153 is off, the signal detector 160 performs an interference signal. S1 is detected without removal. Here, the signal detector 350 receives each signal received according to the application of the multiple antennas, combines them, and restores the signals.

In FIG. 3, a case of using two receiving antennas is described as an example, but a method of receiving a signal using three or four antennas may be applied.

4 is a flowchart schematically illustrating an interference cancellation method according to an exemplary embodiment of the present invention.

Referring to FIG. 4, in step 401, the receiver receives a signal from each transmitter and proceeds to step 413. The receiver may receive a signal from one or more transmitters, wherein a signal other than the signal of the transmitter to be received by the receiver serves as an interference signal for the signal to be received. Accordingly, the receiver according to the present invention performs an operation of removing the interference signal.

In step 413, the receiver demodulates the received signal and proceeds to step 415. In this case, the receiver demodulates the received signals in a demodulation scheme corresponding to the modulation scheme of the transmitters, and may include an interference signal in the demodulated signal.

In step 415, the receiver estimates the channel and proceeds to step 417. The receiver generates channel estimation information by performing channel estimation on the transmission signals of each transmitter. The channel estimation information includes channel estimation information of each channel through which the transmitter transmits a signal and channel response information for measuring channel quality of each channel.

In step 417, the receiver compares the channel estimation information and proceeds to step 419. The receiver measures channel quality for received signals using the channel estimation information generated for each channel. Therefore, since the equation for measuring the channel quality has been described above, a detailed description thereof will be omitted. Thus, the norm or scaled norm of the channel is measured, which makes it possible to compare the signal power, ie, the channel quality, according to the channel response of the received signal. As such, it is possible to compare signals using the signal power, and it is also possible to compare signals of each transmitter using channel quality information.

In step 419, the receiver determines whether to perform interference cancellation as a result of comparing the channel quality obtained using the channel estimation information. In this case, for example, when the signal of the first transmitter is a signal to be received and the signal of the second transmitter is an interference signal, the signal power obtained through the channel response of the first transmitter is the channel response of the second transmitter. When the signal power is smaller than the signal power obtained through the control, the control unit performs the operation of the interference canceller. When the signal power of the first transmitter is greater than the signal power of the second transmitter, the control unit does not perform the interference cancellation. In this case, the interference signal control operation may be continuously performed according to the user setting.

If the receiver does not remove the interference signal as a result of the determination, step 427 is performed. However, if the receiver removes the interference signal as a result of the determination, step 421 is performed. In step 421, the receiver decides to remove the interference signal, that is, the signal transmitted from the second transmitter, and when there are a plurality of transmitters transmitting the interference signal, all the transmission signals of the plurality of transmitters may be removed. have. And, if there are a large number of interference signals, it may be controlled to remove the interference signal for signals having a greater signal power than a signal to be received.

In step 421, the receiver detects the interference signal according to the interference signal removal and proceeds to step 423. The receiver detects and reproduces an interference signal from the demodulated signal of step 413 using the channel estimation information.

In step 423, the receiver removes the interference signal from the received signal and proceeds to step 425. The interference signal is removed from the demodulated signal in step 413. If the signal of the transmitter 2 is an interference signal, the signal of the transmitter 2 is removed.

In step 425, the receiver detects a signal to be received by the receiver from a signal from which interference has been removed or a received signal that has not performed interference cancellation.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiments, but is capable of various modifications within the scope of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by the equivalents of the claims.

As described above, the present invention detects an interference signal from a received signal in a wireless communication system and receives a signal after removing the interference signal according to whether the interference signal is removed. Accordingly, in the wireless communication system, it is possible to receive a signal to be received by a receiver by removing an interference signal. In addition, the reception performance of the signal is improved by removing the interference signal.

Claims (13)

In the method of canceling interference signal in a wireless communication system, Generating channel estimation information by estimating each channel of the received signals; Comparing the channel quality of the interference signal with the received signal using the generated channel estimation information, and determining whether to remove the interference signal based on a comparison result; Detecting the interference signal from the received signals when determining to remove the interference signal; Removing the detected interference signal from the received signals. The method of claim 1, The generated channel estimation information includes information for channel reconstruction and channel response information, respectively. The method of claim 1, And the channel quality of the received signal and the interference signal is measured based on one of a norm and a scaled norm of a channel calculated using corresponding channel estimation information. The method of claim 1, The process of determining whether to remove the interference signal, Determining to remove the interference signal when the power of the signal to be received is less than the power of the interference signal; And determining not to cancel the interference signal when the power of the signal to be received is greater than the power of the interference signal. The method of claim 1, The process of determining whether to remove the interference signal, When the interference signal is two or more, determining whether there is at least one interference signal having a power greater than that of the received signal among the two or more interference signals; And determining to remove the at least one interfering signal when the at least one interfering signal is present. An apparatus for removing interference signals in a wireless communication system, Channel estimation information is generated by estimating each channel with respect to the received signals, and the received channel estimation information is used to compare the channel quality of the received signal with the interference signal and determine whether to remove the interference signal based on the comparison result. A channel estimator, An interference signal detector for detecting the interference signal from the received signals when the channel estimator determines to remove the interference signal; An interference signal removal unit for removing the detected interference signal from the received signals; And a signal detector for detecting a received signal from which the interference signal has been removed. The method of claim 6, The channel estimator, A first channel estimator for estimating a channel of the interference signal; A second channel estimator for estimating a channel of the signal to be received; The channel quality information of the received signal and the interference signal is compared using the channel estimation information output from the first channel estimator and the second channel estimator, and the determination result is determined by removing the interference signal based on the comparison result. And a channel quality comparator for generating an interference signal cancellation control signal. delete The method of claim 7, wherein The channel quality comparator determines to remove the interference signal when the power of the signal to be received is less than the power of the interference signal, and removes the interference signal when the power of the signal to be received is greater than the power of the interference signal. Interfering signal canceling device, characterized in that not. The method of claim 6, The generated channel estimation information may include information for channel reconstruction and channel response information, respectively. The method of claim 6, And the channel quality of the received signal and the interference signal is measured based on one of a norm and a scaled norm of a channel calculated using corresponding channel estimation information. The method of claim 6, The interference signal removing unit, An interference signal detector for detecting the interference signal; An interference signal removal unit regenerating an interference signal using the detected interference signal and channel estimation information on the interference signal; A switch for performing one of an on / off operation under the control of the channel estimator; And an adder for removing the reproduced interference signal from the interference signal canceller according to the operation of the switch. 13. The method of claim 12, And the adder is provided corresponding to each of the plurality of receive antennas when a plurality of receive antennas are used.

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