Patent Publication Number: US-2010118922-A1

Title: Wireless repeater apparatus for canceling interference signal

Description:
TECHNICAL FIELD 
     The present invention relates to a wireless repeater apparatus for canceling an interference signal, a method for the wireless repeater apparatus, and a computer-readable recording medium storing a program for realizing the method; and, more particularly, to a micro integrated wireless repeater apparatus for canceling an interference signal by using a digital interference canceller and an analog interference canceller (e.g., an RF interference canceller) in an organic manner, a method for the wireless repeater apparatus, and a computer-readable recording medium storing a program for realizing the method. 
     BACKGROUND ART 
     In general, a wireless repeater apparatus used in a mobile communication system is installed in a transmission section in order to service a high-quality signal to a mobile communication terminal located in a shadow area. Since transmit/receive (TX/RX) antennas of the wireless repeater apparatus are installed adjacent to each other, some of signals transmitted through the TX antenna are inversely received through the RX antenna, which greatly affects the quality of a signal to be repeated. 
     Therefore, a variety of technologies have been developed to cancel an interference signal received inversely as above. Examples of such technologies will be described with reference to  FIGS. 1 and 2 . 
       FIG. 1  is a block diagram of a conventional wireless repeater apparatus using a general analog interference canceller. 
     Referring to  FIG. 1 , a conventional wireless repeater apparatus using a general analog interference canceller includes: a donor antenna  100  for receiving a forward repetition signal (i.e., a signal to be repeated in a forward direction) from a base station; a donor band-pass filter  101  for band-pass filtering the forward repetition signal received through the donor antenna  100 ; an RF interference cancellation signal generator  105  for generating an interference cancellation signal using a forward repetition signal divided by a divider  104 ; a synthesizer (i.e., an interference signal canceller)  102  for removing an interference signal from a forward repetition signal received from the donor band-pass filter  101  by using the interference cancellation signal generated by the RF interference cancellation signal generator  105 ; a repetition amplifier  103  for amplifying a forward repetition signal received from the synthesizer  102 ; the divider  104  for dividing the amplified forward repetition signal received from the repetition amplifier  103  and transmitting the divided signals to the RF interference cancellation signal generator  105  and a service band-pass filter  106 ; the service band-pass filter  106  for filtering a forward repetition signal received from the divider  104 ; and a service antenna  107  for transmitting a forward repetition signal received from the service band-pass filter  106  to a mobile communication terminal located in a service coverage area. 
     Herein, not only a forward repetition signal (i.e., a repetition target signal) but also an interference signal, which is a feedback of a portion of a signal transmitted through the service antenna  107 , are included in a signal received through the donor antenna  100 . Thus, in order to cancel the interference signal, the RF interference cancellation signal generator  105  generates an interference cancellation signal by using a forward repetition signal received from the divider  104 , and transmits the generated interference cancellation signal to the synthesizer  102 . Then, the synthesizer  102  removes an interference signal from a forward repetition signal received from the donor band-pass filter  101  by using the interference cancellation signal received from the RF interference cancellation signal generator  105 . 
     When a feedback interference signal has a short delay time, the above-described conventional method can cancel an interference signal. However, when the feedback interference signal has a very long delay time, the hardware implementation complexity becomes very high, thus making it impossible to implement the above-described conventional method. 
     In order to solve the above-described problem of the conventional analog interference cancellation method, digital signal processing technologies have been developed to propose a digital interference cancellation method capable of canceling a feedback interference signal more accurately. 
       FIG. 2  is a block diagram of a conventional wireless repeater apparatus using a general digital interference canceller. 
     Referring to  FIG. 2 , a conventional wireless repeater apparatus using a general digital interference canceller includes: a donor antenna  200  for receiving a forward repetition signal (i.e., a signal to be repeated in a forward direction) from a base station; a donor band-pass filter  201  for band-pass filtering the forward repetition signal received through the donor antenna  200 ; a down-converter  202  for converting a forward repetition signal received from the donor band-pass filter  201  into a baseband signal; a digital converter  203  for converting a forward repetition signal received from the down-converter  202  into a digital signal; a digital interference canceller  204  for removing an interference signal from a forward repetition signal received from the digital converter  203 ; an analog converter  205  for converting a forward repetition signal received from the digital interference canceller  204  into an analog signal; an up-converter  206  for converting a forward repetition signal received from the analog converter  205  into an RF signal; a service band-pass filter  207  for band-pass filtering a forward repetition signal received from the up-converter  206 ; and a service antenna  208  for transmitting a forward repetition signal received from the service band-pass filter  207  to a mobile communication terminal located in a service coverage area. 
     Herein, not only a forward repetition signal (i.e., a repetition target signal) but also an interference signal, which is a feedback of a portion of a signal transmitted through the service antenna  208 , are included in a signal received through the donor antenna  200 . Thus, in order to cancel the interference signal, the digital converter  203  converts a forward repetition signal (i.e., a repetition target signal containing an interference signal) down-converted by the down-converter  202  into a digital signal, and transmits the digital signal to the digital interference canceller  204 . Then, the digital interference canceller  204  detects a feedback signal and cancels an interference signal contained in a forward repetition signal to achieve a gain. 
     The above-described conventional digital interference cancellation method can cancel an interference signal regardless of the delay time of a fed-back interference. However, when an interference signal is very strong, the conventional digital interference cancellation method degrades in interference cancellation performance and thus has a limitation in the interference cancellation performance. 
     As the demand for a mobile wireless Internet increases, the number of shadow areas increases and thus the number of installation places for wireless repeater apparatuses increases. Therefore, micro miniaturization of the wireless repeater apparatus is strongly required. Since the micro wireless repeater apparatus has a very small distance between a donor antenna and a service antenna, a direct feedback signal becomes very strong. Therefore, the conventional digital interference canceller fails to process a strong interference signal, thus making it impossible to achieve a large interference cancellation gain. 
     DISCLOSURE 
     Technical Problem 
     An embodiment of the present invention is directed to providing a micro integrated wireless repeater apparatus for canceling an interference signal by using a digital interference canceller and an analog interference canceller (e.g., an RF interference canceller) in an organic manner, a method for the wireless repeater apparatus, and a computer-readable recording medium storing a program for realizing the method. 
     Another embodiment of the present invention is directed to providing a micro integrated wireless repeater apparatus for canceling an interference signal, which can increase the stability of signal repetition and enhance the signal quality by removing a feedback signal component from a repetition target signal by using a digital interference canceller and an analog interference canceller (e.g., an RF interference canceller) in an organic manner, a method for the wireless repeater apparatus, and a computer-readable recording medium storing a program for realizing the method. 
     A further embodiment of the present invention is directed to providing a micro integrated wireless repeater apparatus for canceling an interference signal where a donor antenna must be physically close to a service antenna, which can achieve a large interference cancellation gain, increase the stability of signal repetition and enhance the signal quality by getting a digital interference canceller to remove a residual interference signal component after getting an analog interference canceller (e.g., an RF interference canceller) to remove an interference signal component, which has a short time delay and a high interference level (i.e., a strong signal interference) in an RF domain, according to a control signal received from the digital interference canceller, a method for the wireless repeater apparatus, and a computer-readable recording medium storing a program. for realizing the method. 
     Other objects and advantages of the present invention can be understood by the following description, and become apparent with reference to the embodiments of the present invention. Also, it is obvious to those skilled in the art of the present invention that the objects and advantages of the present invention can be realized by the means as claimed and combinations thereof. 
     Technical Solution 
     In accordance with an aspect of the present invention, there is provided a micro integrated wireless repeater apparatus for canceling an interference signal, including: a receiving means for receiving a repetition signal; an analog interference cancellation means for generating an interference cancellation signal according to a control signal and removing an interference signal from the repetition signal received from the receiving means; a digital interference cancellation means for canceling a residual interference signal remaining in a repetition signal obtained by canceling an interference signal component by the analog interference cancellation means; a control means for controlling the analog interference cancellation means by transmitting the control signal to the analog interference cancellation means according to control information received from the digital interference cancellation means; and a transmitting means for transmitting a repetition signal obtained by canceling a residual interference signal component by the digital interference cancellation means. 
     Advantageous Effects 
     In accordance with the present invention as described above, a micro integrated wireless repeater apparatus for canceling an interference signal, in which a donor antenna must be physically close to a service antenna, can increase the stability of signal repetition and enhance the signal quality by removing a feedback signal component from a repetition target signal by using a digital interference canceller and an analog interference canceller (e.g., an RF interference canceller) in an organic manner. 
     Also, a micro integrated wireless repeater apparatus for canceling an interference signal, in which a donor antenna must be physically close to a service antenna, can achieve a large interference cancellation gain, increase the stability of signal repetition and enhance the signal quality by getting a digital interference canceller to remove a residual interference signal component after getting an analog interference canceller (e.g., an RF interference canceller) to remove an interference signal component which has a short time delay and a high interference level (i.e., a strong signal interference) in an RF domain, according to a control signal received from the digital interference canceller. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a conventional wireless repeater apparatus using a general analog interference canceller. 
         FIG. 2  is a block diagram of a conventional wireless repeater apparatus using a general digital interference canceller. 
         FIG. 3  is a block diagram of a micro integrated wireless repeater apparatus for canceling an interference signal in accordance with an embodiment of the present invention. 
         FIG. 4  is a block diagram of a digital interference canceling unit of  FIG. 3  in accordance with an embodiment of the present invention. 
         FIG. 5  is a block diagram of an RF interference cancellation signal generator of  FIG. 3  in accordance with an embodiment of the present invention. 
         FIG. 6  is a flow diagram illustrating a wireless repeating method for canceling an interference signal in accordance with an embodiment of the present invention. 
     
    
    
     BEST MODE FOR THE INVENTION 
     The advantages, features and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter. Therefore, those skilled in the field of this art of the present invention can embody the technological concept and scope of the invention easily. In addition, if it is considered that a detailed description on a related art may obscure the points of the present invention, the detailed description will not be provided herein. Hereinafter, the preferred embodiments of the present invention will be described in detail hereinafter with reference to the attached drawings. 
       FIG. 3  is a block diagram of a micro integrated wireless repeater apparatus for canceling an interference signal in accordance with an embodiment of the present invention. 
     Since operations and constructions for a forward repetition signal are similar to operations and constructions for a reverse repetition signal, only the operations and constructions of the forward repetition signal will be described and a description of the operations and constructions of the reverse repetition signal will be omitted for conciseness. 
     Referring to  FIG. 3 , a micro integrated wireless repeater apparatus for canceling an interference signal in accordance with the present invention includes: a receiving terminal  310  for receiving a forward repetition signal (i.e., a signal to be repeated in a forward direction); an analog interference canceller (i.e., an RF interference canceller)  320  for generating an interference cancellation signal according to a control signal received from an RF controller  340  and removing an interference signal from a forward repetition signal received from the receiving terminal  310 ; a digital interference canceller  330  for canceling a residual interference signal remaining in a forward repetition signal obtained by canceling an interference signal component by the analog interference canceller  320 ; the RF controller  340  for controlling the analog interference canceller  320  according to control information received from the digital interference canceller  330 ; and a transmitting terminal  350  for transmitting a forward repetition signal obtained by canceling a residual interference signal component by the digital interference canceller  330 . 
     As described above, the analog interference canceller  320  primarily cancels an interference signal component, which has a short time delay (e.g., 300 ns or less) and a high interference level (e.g., an interference level about 20 dB higher than a primary signal to be repeated when the repeater apparatus has the maximum gain) in an RF domain, according to a control signal received from the digital interference canceller  330  through the RF controller  340 , and then the digital interference canceller  330  detects a feedback signal and secondarily cancels a residual interference signal component contained in a forward repetition signal. 
     In detail, the receiving terminal  310  includes a donor antenna  311  and a donor band-pass filter  312 . The analog interference canceller  320  includes a divider  321 , an RF interference cancellation signal generator  322 , and a synthesizer  323 . The digital interference canceller  330  includes a down-converter  331 , a digital converter  332 , a digital interference canceling unit  333 , an analog converter  334 , and an up-converter  335 . The transmitting terminal  350  includes a service band-pass filter  351  and a service antenna  352 . 
     Based on the above-described components, an overall description will now be given of the detailed connection and operation of the micro integrated wireless repeater apparatus for canceling an interference signal in accordance with the present invention. 
     The micro integrated wireless repeater apparatus for canceling an interference signal in accordance with the present invention includes: a donor antenna  311  for receiving a forward repetition signal (i.e., a signal to be repeated in a forward direction) from a base station; a donor band-pass filter  312  for band-pass filtering the forward repetition signal received through the donor antenna  311 ; an RF interference cancellation signal generator  322  for generating an interference cancellation signal using a forward repetition signal received from the divider  321 ; a synthesizer (i.e., an interference signal canceller)  323  for removing an interference signal from a forward repetition signal received from the donor band-pass filter  312  by using the interference cancellation signal received from the RF interference cancellation signal generator  322 ; a down-converter  331  for converting a forward repetition signal received from the synthesizer  323  into a baseband signal; a digital converter  332  for converting a forward repetition signal received from the down-converter  331  into a digital signal; a digital interference canceling unit  333  for removing a residual interference signal from a forward repetition signal received from the digital converter  332 ; the RF controller  340  for controlling the RF interference cancellation signal generator  322  according to control information received from the digital interference canceling unit  333 ; an analog converter  334  for converting a forward repetition signal received from the digital interference canceling unit  333  into an analog signal; an up-converter  335  for converting a forward repetition signal received from the analog converter  334  into an RF signal; the divider  321  for dividing a forward repetition signal up-converted by the up-converter  335  and transmitting the divided signals to the RF interference cancellation signal generator  322  and the service band-pass filter  351 ; the service band-pass filter  351  for band-pass filtering a forward repetition signal received from the divider  321 ; and the service antenna  352  for transmitting a forward repetition signal received from the service band-pass filter  351  to a mobile communication terminal located in a service coverage area. 
     Herein, the RF controller  340  receives the control information for controlling the RF interference cancellation signal generator  322  from the digital interference canceling unit  333 , which will be described later with reference to  FIG. 4 . One of the forward repetition signals divided by the divider  321  is transmitted to the RF interference cancellation signal generator  322  and is used to generate the RF interference cancellation signal, while the other of the divided forward repetition signals is transmitted to the service band-pass filter  351  and is repeated. 
       FIG. 4  is a block diagram of the digital interference canceling unit  333  of  FIG. 3  in accordance with an embodiment of the present invention. 
     Referring to  FIG. 4 , the digital interference canceling unit  333  of the present invention includes: an automatic gain controller  405  for automatically controlling the gain (i.e., the output signal size) of a forward repetition signal to be repeated; a feedback signal detector  402  for detecting the phase, size (amplitude), time delay of a residual feedback signal contained in the forward repetition signal from a baseband digital forward repetition signal received from the automatic gain controller  405  and a baseband digital forward repetition signal received from the digital converter  332 , and updating the phase, size (amplitude) and time delay of the feedback signal; an inverse feedback signal synthesizer  403  for generating an inverse feedback signal to be used to cancel the residual feedback signal contained in the forward repetition signal by using the baseband digital forward repetition signal received from the automatic gain controller  405  and the phase, size (amplitude) and time delay of the feedback signal received from the feedback signal detector  402 ; a feedback signal canceller  404  for canceling the residual feedback signal contained in the digital forward repetition signal received from the digital converter  332  by using the inverse feedback signal received from the inverse feedback signal synthesizer  403 , and transmitting the resulting signal to the automatic gain controller  405 ; an synchronization acquirer  400  for acquiring a synchronization with the base station (or a communication terminal in a service coverage area) by using the digital forward repetition signal received from the digital converter  332 ; and a controller  401  for canceling the residual feedback signal contained in the forward repetition signal by using base station information and a synchronization signal received from the synchronization acquirer  400 , controlling the respective components to transmit the forward repetition signal, and transmitting control information to the RF controller  340  according to update information received from the feedback signal detector  402 . 
     Herein, the synchronization acquirer  400  is essential to, for example, a TDD wireless repeater apparatus and is used to extract a synchronization signal necessary for accurately controlling a signal flow in a forward direction (from base station to mobile communication terminal) or in a reverse direction (from mobile communication terminal to base station). This synchronization signal extraction (or acquisition) process is performed to detect a signal (i.e., a preamble) located at the start of a downlink from the base station to the mobile communication terminal. The preamble is configured to efficiently extract a synchronization signal in a TDD scheme, and base station information such as an ID of the base station and segment information can be additionally acquired in an acquisition process for the synchronization signal. In this way, the synchronization acquirer  400  acquires the synchronization signal, detects the base station information, and transmits the information to the controller  401 . Then, the controller  401  controls a TDD-based wireless repeating operation by using the base station information and the synchronization signal received from the synchronization acquirer  400 . 
     Herein, when the synchronization acquirer  400  acquires a synchronization signal stably for more than a predetermined time period (e.g., more than about 3 seconds that is a time period that can be regarded as the same signal strength over a plurality of frames) under the condition of more than a predetermined signal size (e.g., more than about 1/10 of an average input signal size), it applies the synchronization signal to the controller  401 . On the other hand, when synchronization is not acquired, no synchronization signal is applied to the controller  401  so that all of the operations of the wireless repeater apparatus are stopped until the synchronization is acquired. Although not illustrated in the drawings, the synchronization acquirer  400  controls the downlink in consideration of a signal processing time period spent in the respective components  401  to  405  and a time period spent in the filters and other components. 
     The feedback signal detector  402  may estimate a feedback signal component by using the base station ID acquired by the synchronization acquirer  400 . That is, since the base station ID is constructed using a pseudo noise (PN) code, the phase, size (amplitude) and time delay of the feedback signal may be estimated by calculating the correlation between the base station ID and the forward repetition signal. Therefore, the feedback signal detector  402  detects the phase, size (amplitude) and time delay of the residual feedback signal contained in the forward repetition signal by calculating the correlation between the base station ID received from the controller  401  and the forward repetition signal received from the automatic gain controller  405  and the digital converter  332 , and transmits the detected information to the inverse feedback signal synthesizer  403 . 
     The automatic gain controller  405  determines a gain value by using the size of the forward repetition signal received from the feedback signal canceller  404 , a gain control value according to the current state, a target gain value, and a predetermined target output size value received from the controller  401 , and uses the determined gain value to automatically control the gain (i.e., the output signal size) of the forward repetition signal obtained by canceling the feedback signal by the feedback signal canceller  404 . For example, the automatic gain control is performed as follows: When the output value is greater than the predetermined target output size value, the automatic gain controller  405  limits the output size in order not to increase the gain any more. On the other hand, when the output value is smaller than the predetermined target output size value, the automatic gain controller  405  increases the gain by a predetermined unit time (e.g., 3 dB/1 second) until the size of the signal received from the feedback signal canceller  404  reaches the target gain value. 
     The feedback signal canceller  404  removes a feedback signal from the forward repetition signal received from the digital converter  332  by using the inverse feedback signal received from the inverse feedback signal synthesizer  403 , and transmits the resulting signal to the automatic gain controller  405 . 
     That is, the feedback signal canceller  404  cancels the residual feedback signal contained in the forward repetition signal by synthesizing the forward repetition signal received from the digital converter  332  and the inverse feedback signal received from the inverse feedback signal synthesizer  403 , and then transmits the resulting forward repetition signal to the automatic gain controller  405 . 
     Using the baseband forward repetition signal received from the automatic gain controller  405  and the phase, size (amplitude) and time delay of the feedback signal received from the feedback signal detector  402 , the inverse feedback signal synthesizer  403  controls the phase, size (amplitude) and time delay of the signal used for canceling the feedback signal contained in the forward repetition signal, thereby generating the inverse feedback signal. 
     Using the synchronization signal received from the synchronization acquirer  400 , the controller  401  detects the timing of the downlink to control a signal flow from the base station to the mobile communication terminal. Also, using the base station information received from the synchronization acquirer  400 , the controller  401  transmits a code (e.g., the base station ID) necessary for detection of the feedback signal to the feedback signal detector  402 . Then, the feedback signal detector  402  updates the phase, size (amplitude) and time delay of the feedback signal and then transmits the corresponding update control information to the controller  401 . Then, the controller  401  transmits control information such as the updated phase, size (amplitude) and time delay to the RF controller  340  so that the RF controller  340  can control the update elements of the RF interference cancellation signal generator  322 . According to the synchronization acquisition results of the synchronization acquirer  400  with respect to the synchronization from the base station to the mobile communication terminal, the controller  401  controls the operations of the automatic gain controller  405 , the feedback signal detector  402 , the inverse feedback signal synthesizer  403 , and the feedback signal canceller  404 . If a transmission signal is contained in a reception signal, that is, if the synchronization signal and the base station information are acquired by the synchronization acquirer  400 , the controller  402  normally operates the automatic gain controller  405 , the feedback signal detector  402 , the inverse feedback signal synthesizer  403 , and the feedback signal canceller  404 . In this case, the target output size value is preset to a predetermined value and is transmitted to the automatic gain controller  405 . On the other hand, if a transmission signal is not contained in a reception signal, that is, if the synchronization signal is not acquired by the synchronization acquirer  400 , the controller  401  stops the operations of the automatic gain controller  405 , the feedback signal detector  402 , the inverse feedback signal synthesizer  403 , and the feedback signal canceller  404 . 
     Meanwhile, the digital interference canceling unit  333  further includes an automatic delay controller  406  for preventing a mutual interference between the feedback signal and a multi-path signal. That is, in order for the feedback signal to be able to be generated when a multi-path signal is not received, the automatic delay controller  406  is connected to the automatic gain controller  405  to control the generation delay of the feedback signal so that the feedback signal can be cancelled under the condition that the multi-path signal and the feedback signal do not overlap each other. To this end, the wireless repeater apparatus beforehand detects the position of a multi-path component, that is, the time when the multi--path signal is generated. 
       FIG. 5  is a block diagram of the RF interference cancellation signal generator  322  of  FIG. 3  in accordance with an embodiment of the present invention. 
     Referring to  FIG. 5 , the RF interference cancellation signal generator  322  of the present invention includes: an attenuator  500  for attenuating, according to a control signal received from the RF controller  340 , the level (i.e., strength) of the forward repetition signal containing the feedback interference signal received from the divider  321 ; a time delayer  501  for controlling (or compensating) the time delay for a forward repetition signal received from the attenuator  500  according to a control signal received from the RF controller  340 ; and a phase shifter  502  for shifting the phase of a forward repetition signal received from the time delayer  501  according to a control signal received from the RF controller  340 . 
     Herein, the phase-shifted forward repetition signal of the phase shifter  502  is transmitted to the synthesizer  323  in order to cancel an interference signal. 
     Then, the synthesizer  323  synthesizes the interference cancellation signal received from the RF interference cancellation signal generator  322  and the forward repetition signal received from the donor band-pass filter  312 , to remove an interference signal from the forward repetition signal containing the feedback interference received from the donor band-pass filter  312 . 
     At this point, an interference component having a short time delay is cancelled by the analog interference canceller (RF interference canceller)  320 , but the residual interference signal having a long time delay is not cancelled as yet. Thus, the residual interference signal is cancelled by the digital interference canceller  330 . 
       FIG. 6  is a flow diagram illustrating a wireless repeating method for canceling an interference signal in accordance with an embodiment of the present invention. In the wireless repeating method, a forward repetition signal is repeated, and then a feedback signal remaining in a subsequent forward repetition signal is cancelled by using the resulting feedback signal. 
     For example, in the case of a downlink in a TDD wireless repeating scheme, a signal received from the interference canceller  320 / 330  through a path from the donor antenna  311  to the donor band-pass filter  312  may contain both of a repetition signal that is transmitted from a base station for repeating an actual service and a feedback signal that is a feedback of a signal transmitted through the service antenna  352 , or main contain only a feedback signal containing a random noise. A base station transmission signal is represented as a multi-path signal due to a wireless channel environment, and the case where there is only a feedback signal in a signal received in the wireless repeater apparatus corresponds to the case where the base station does not transmits a transmission signal to the mobile communication terminal. This is similarly applied to an uplink from the mobile communication terminal to the base station, and thus a description will be given of only the downlink case for conciseness. 
     Since a specific embodiment and the operation according to the specific embodiment are the same as described above, a description will be given of only the essential points of the wireless repeating method for removing an interference signal according to the present invention. 
     Referring to  FIG. 6 , in operation S 601 , the receiving terminal  310  receives a forward repetition signal that is a signal to be repeated in a forward direction. 
     In operation S 602 , the analog interference canceller (the RF interference canceller)  320  generates an interference cancellation signal according to a control signal received from the RF controller  340 , and cancels an interference signal from the forward repetition signal. 
     In operation S 603 , the digital interference canceller  330  cancels a residual interference signal remaining in a forward repetition signal obtained by canceling an interference signal component by the analog interference canceller  320 . 
     In operation S 604 , the RF controller  340  controls the analog interference canceller (the RF interference canceller)  320  according to control information received from the digital interference canceller  330 . 
     In operation S 605 , the transmitting terminal  350  transmits a forward repetition signal obtained by canceling a residual interference signal component by the digital interference canceller  330 . 
     Although the analog interference cancellation operation S 602 , the digital interference cancellation operation S 603 , and the control operation S 604  have been described as being performed in the above order, they may be performed in any other order because they are circulative operations. 
     The methods for canceling an interference signal in accordance with the embodiments of the present invention can be realized as a program and stored in a computer-readable recording medium, such as CD-ROM, RAM, ROM, floppy disk, hard disk and magneto-optical disk. Since the process can be easily implemented by those skilled in the art of the present invention, further description will not be provided herein. 
     While the present invention has been described with respect to the specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.