JP4939653B2 - Interference cancellation repeater and method using feedforward / feedback signal search and feedback cancellation window splitting - Google Patents

Description

  The present invention relates to a feedback cancellation window division method considering both a feedforward signal and a feedback signal, and an interference cancellation repeater using the method, and more particularly, a feedback signal other than a feedforward signal in the interference cancellation repeater. The present invention relates to a feedforward / feedback signal search and feedback cancellation window division method, and an interference cancellation repeater using the same, which can prevent deterioration of the quality of a source signal by removing only the signal.

  Domestic mobile communication has been rapidly developed while commercializing mobile communication services using CDMA (Code Division Multiple Access) for the first time since the introduction of cellular systems using AMPS (Advanced Mobile Phone System). I have done it. In particular, the IMT (International Mobile Telecommunications) -2000 system as next-generation mobile communication will increase its market by providing multimedia services such as high-speed and high-quality video services from current voice services and low-speed data services. It is a prospect to do. However, in IMT-2000, the radius of a cell that can be served by one base station is reduced by using a frequency band higher than the current cellular band or PCS band. In urban areas, even if base stations are installed with a narrow cell radius as a unit, there are radio wave shadow areas due to propagation obstructions such as buildings. In order to solve such a problem, it is economical to use a relatively inexpensive repeater rather than installing many expensive base station apparatuses.

  The repeater is roughly classified into an optical repeater, a microwave ground repeater, a variable wave repeater using frequency conversion, and an invariant wave repeater (general RF repeater) according to the relay method.

  The optical repeater is a system in which an RF signal of a base station is converted into an optical signal, transmitted through an already-embedded optical line, and then converted into an RF signal by a repeater and transmitted. However, the optical repeater can be installed anywhere where the optical line can be drawn in, but the cost of lending the optical line is high, and service is possible only where the optical line is drawn in. There is a drawback of being.

  The microwave terrestrial repeater is a system in which a signal from a base station is converted into high frequency radio waves by a donor unit (hereinafter referred to as “DU”) and then transmitted. The microwave ground repeater has the advantage of being easy to install, but has the disadvantage that it must be installed at a position where visible rays are secured, as well as being greatly affected by the weather conditions.

  The wave repeater is a system that relays a transmission signal after converting it to any one of permitted frequencies that are not currently used. Unlike existing repeaters that depend only on the characteristics of the RF signal, the wave repeater uses a modified version of the characteristics of the base station currently in use, is easy to implement and easy to implement, Although there is no oscillation phenomenon, there is a disadvantage that a frequency conversion device is further required and it can only be operated with a frequency utilization efficiency of 1/2. In particular, when only four carriers (FA) are used per operator as in WCDMA (Wideband CDMA), only a maximum of two carriers can be serviced, so the use is practically limited.

  On the other hand, a non-variable wave repeater is a general form of RF repeater system that can be most easily realized because it uses the same frequency during transmission and reception, unlike a variable wave repeater. However, there is a drawback that the signal amplified by the repeater is fed back and oscillation is likely to occur. Therefore, in the present invariant wave repeater, the distance between the transmitting and receiving antennas of the invariant wave repeater is separated as shown in FIG. A method of ensuring (isolation) and a method of limiting the output within a range where oscillation does not occur are used. However, in an environment where the transmitting and receiving antennas cannot be sufficiently separated by a desired distance, or in an environment where a high gain (G) of an amplifier (AMP) is required, many problems occur in the use of the invariant wave repeater.

  In order to solve such a problem, an interference cancellation system (ICS) that detects and removes a feedback signal that causes oscillation is used.

  FIG. 2 is a schematic diagram illustrating a configuration of an interference cancellation repeater according to the related art.

  In the following description of the present invention, the forward link will be described as a reference. However, it is obvious to those skilled in the art that the present invention can be similarly applied to the reverse link.

As shown in FIG. 2, the interference cancellation repeater according to the conventional technique includes a feedback signal f that is input via a transmission signal r _in (t) from the base station 11 and a feedback channel as a time-varying multipath fading channel. a receiving antenna 12 that receives _intra (t) (hereinafter referred to as “link antenna”), an A / D converter 13 that converts a signal received from the link antenna 12 into a digital signal r ′ _in (n), A digital signal processing unit 14 for removing the feedback signal f _intra (t) from the RF signal received as the link antenna 12, and D / for converting the signal from which the feedback signal has been removed to an analog signal r ₀ (n) A converter 15 and the analog signal converted by D / A converter 15 are amplified by a predetermined system gain G. An amplifier 16 for power transmission antenna 17 for transmitting a signal received from the base station to the subscriber or other repeaters (hereinafter, referred to as "service antenna") comprising a.

The digital signal processing unit 14 includes a feedback signal detection unit 19 that estimates a time delay, an amplitude, and a phase of the feedback signal using a correlation of the received radio input signal, and a time-varying feedback. And a feedback signal removal filter 18 for adaptively estimating and removing the signal to remove a feedback signal that causes oscillation. Since the feasible feedback signal removal filter hardware is limited, the delay time of the removable feedback signal, that is, the distance of the feedback signal is limited. For example, in the case of a WCDMA system, the size of the feedback cancellation window depending on the distance of the removable feedback signal is the same as the time (μsec) in Table 1. Generally, when passing through a path of 2 to 3 km or more, the feedback signal level hardly oscillates due to path loss. Therefore, the size of the feedback cancellation window is designed in consideration of such matters.

FIG. 3 illustrates a scheme for setting / operating a feedback cancellation window in a conventional interference cancellation repeater. In general, a feedback signal up to X _tot (μsec) on the basis of the device delay time of the repeater itself is included in the range of the feedback removal window and can be removed, but feedback received after X _tot (μsec). Signal removal is not possible. For example, according to Table 1, when X _tot is designed to be 8 μsec, only a feedback signal up to about 2.4 km can be removed. The detection of the feedback signal is performed by connecting the unit windows of the X _step size in a sequential manner or a parallel manner and searching for the entire removal window. That is, the removable total window size X _tot can be expressed by the sum of M (where M is a natural number) unit windows X _step as shown in Equation 1. Hereinafter, the unit window is referred to as a bank.
[Formula 1]
X _tot = M · X _step

On the other hand, the interference cancellation repeater is a kind of RF repeater, and a phenomenon may occur where signals are exchanged with other RF repeaters in the vicinity. In particular, according to the structure of the mobile communication network in Korea, there are many environments where the distance between installed repeaters is short. When the distance between the repeaters is short as described above, when a feedback loop is formed by signal transmission / reception between repeaters, the delay time of the repeater itself is included in the feedback path, so that the feedback removal window region X _tot is outside. A phenomenon in which a feedback signal between repeaters is formed may occur.

FIG. 4 illustrates a case where a feedback signal between repeaters is formed when using an interference cancellation repeater. When the interference cancellation repeater is operated in, for example, a connection type (Cascade), the former repeater is referred to as a donor unit (DU), and the latter repeater is referred to as a remote unit (RU). If the distance d _DR between the DU and the RU is relatively smaller than the distance d _BD between the base station and the DU, the path loss of the signal level at which the signal is re-input from the RU to the DU is small. f _inter (t) can never be ignored. Also, even if the front / rear ratio of the antenna is taken into consideration, a feedback signal between repeaters is formed in an environment where the influence of path loss due to distance is relatively small, and the feedback signal between repeaters is related to FIG. It may be located outside the feedback cancellation window area for canceling the feedback signal of the repeater itself described above and cause oscillation.

  As shown in FIG. 5, even in the case of not being connected, a feedback signal between intermediate devices similar to that described in FIG. 4 can be formed under environmental conditions where a large number of interference cancellation repeaters are located at a short distance in the vicinity.

  Therefore, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to remove only a feedback signal other than a feedforward signal and a feedforward image signal by an interference cancellation repeater. Therefore, it is an object of the present invention to provide a feedforward and feedback signal search method, a feedback cancellation window division method, and an interference cancellation repeater using these methods, which can prevent deterioration of the quality of a received signal.

The features of the present invention for achieving the above object can be summarized as follows. According to an aspect of the present invention, a feedback signal is searched from an RF (Radio Frequency) signal received via a receiving antenna and including the feedback signal itself and a feedback signal between repeaters by moving a feedback cancellation window. A window setting unit for dividing a feedback removal window (X _tot ) based on the searched feedback signal; and a feedback signal is removed from the received RF signal based on the feedback removal window divided by the window setting unit. A repeater for removing interference caused by a feed signal is provided.

According to another aspect of the present invention, a feed signal is searched and searched for from an RF signal received via a receiving antenna and including its own feedback signal and a feedback signal between repeaters by moving a feedback cancellation window. A window setting step for dividing a feedback removal window (X _tot ) based on the feedback signal, and a feedback signal is detected and removed from the received RF signal based on the feedback removal window divided in the window setting step. A method for canceling interference due to a feedback signal at a repeater.

  According to another aspect of the present invention, receiving an RF signal including a feedback signal and a feedforward signal via a link antenna of an interference cancellation repeater that removes the feedback signal using a feedback cancellation window; Detecting a forward signal and removing the feedback signal by resetting the feedback cancellation window such that the detected feedforward signal is not included in the feedback cancellation window. Provide a method.

  According to another aspect of the present invention, a link antenna that receives an RF signal including a feedback signal and feedforward, and a feedforward signal searcher that searches for a feedforward signal among RF signals received via the link antenna. And a system delay unit for adding a system delay of the interference cancellation repeater so that the detected feedforward signal is not included in the feedback cancellation window. An interference canceling repeater is provided.

  According to the present invention, the interference cancellation repeater separates the feedforward signal and the feedback signal and removes only the feedback signal other than the feedforward signal, thereby preventing the quality of the received signal from being deteriorated. is there.

  Further, according to the present invention, it is possible to remove only the feedback signal other than the feedforward signal while using the existing configuration of the conventional interference cancellation repeater as it is without adding another configuration. There is an effect.

It is a figure which shows schematically the structure of the conventional radio repeater. It is a figure which shows schematically the structure of the conventional interference cancellation repeater which detects / removes the feedback signal which causes an oscillation. It is a figure which shows the system which sets / operates a feedback cancellation window with the conventional interference cancellation repeater. It is a figure which shows an example when the feedback signal between the conventional interference cancellation repeaters is formed. It is a figure which shows the other example at the time of the feedback signal between the conventional interference cancellation repeaters being formed. It is a figure which shows the structure of the interference removal repeater which concerns on one Example of this invention. It is a figure for demonstrating operation | movement of the feedback signal search part of FIG. It is a figure which shows an example in which the feedback removal window was divided | segmented. 4 is a flowchart illustrating an operation process of an interference cancellation repeater including a feedback cancellation window division function according to an embodiment of the present invention. It is a figure for demonstrating an example of the signal input via another repeater as an external input signal unrelated to the gain of the repeater itself which receives RF signal. It is a figure for demonstrating the relationship between the signals of FIG. It is a figure which shows roughly the feedforward image signal produced | generated as a result of measuring the correlation of an input signal when a feedforward signal exists. FIG. 5 is a diagram schematically illustrating a feedforward signal processing method in an interference cancellation repeater according to a preferred embodiment of the present invention. It is a figure which shows roughly the feedforward signal processing method in the interference cancellation repeater which concerns on another suitable Example of this invention. 6 is a flowchart for explaining a feedforward signal processing method in an interference cancellation repeater according to another preferred embodiment of the present invention. 6 is a flowchart for explaining a feedforward signal processing method in an interference cancellation repeater according to another preferred embodiment of the present invention. 6 is a flowchart for explaining a feedforward signal processing method in an interference cancellation repeater according to another preferred embodiment of the present invention. 6 is a flowchart for explaining a feedforward signal processing method in an interference cancellation repeater according to another preferred embodiment of the present invention. It is a figure which shows schematically the structure in the interference cancellation repeater which concerns on one preferable Example of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, only the forward direction will be described, but it should be noted that the reverse direction can be applied in the same manner as the forward direction or can be applied separately from the forward direction. is there. It should also be noted that although the following embodiments may be performed in real time, they may be performed on-demand at the initial installation of the repeater or upon user request.

  FIG. 6 is a diagram illustrating the configuration of the interference cancellation repeater according to the embodiment of the present invention.

  The interference cancellation repeater (hereinafter referred to as “repeater”) according to the embodiment of the present invention includes a reception antenna 12, an A / D converter 13, a feedback signal removal unit 48, a window setting unit 40, and a D / A converter 15. , Including an amplification unit 16 and a transmission antenna 17. The feedback signal removal unit 48 includes a feedback signal removal filter 46 and a feedback signal detection unit 47, and the window setting unit 40 includes a window division unit 41 and a feedback signal search unit 42.

  The repeater is configured to support bi-directional links, i.e., forward and reverse links. The forward link is for receiving a signal from the base station via the receiving antenna 12 and for transmitting the base station signal to a shaded area where the base station signal does not reach via the transmitting antenna 17. Is for receiving a signal provided from the terminal via the transmission antenna 17 and transmitting it to the base station via the reception antenna 12.

  Hereinafter, the description will be made based on the forward link, and the reverse link may be considered to be the reverse of the forward link.

The reception antenna 12 is an antenna that receives the source reception signal r _in (t) from the base station, and generally, the source reception signal r _in (t) includes signals of a large number of base stations. In addition, the receiving antenna 12 according to the embodiment of the present invention includes the feedback signal f _intra (t) received from the transmitting antenna 17 of the repeater via the radio channel and the radio channel from the transmitting antennas of other neighboring repeaters. The _inter- repeater feedback signal f _inter (t) received via is also received. That is, the total input signal r ′ _in (t) received via the receiving antenna 12 is the source received signal r _in (t), the feedback signal f _intra (t) itself, and the feedback signal f _inter (t) between the repeaters. Is the sum of Here, the total input signal is an analog signal.

The A / D converter 13 converts the total input signal r ′ _in (t) as an analog signal received via the receiving antenna 12 into a digital signal, and converts the digital signal generated at this time to r ′ _in ( n). Here, n is a chip index.

The feedback signal removal unit 48 includes a feedback signal removal filter 46 and a feedback signal detection unit 47, and removes the feedback signal from the total input signal r ′ _in (n) _in the unit window stage.

The feedback signal detector 47 calculates the degree of correlation using the correlation between the total input signal r ′ _in (n) and the signal from which the previously generated feedback is removed in the unit window X _step. Estimating the time delay, amplitude and phase of the feedback signal which changes based on the degree of correlation. The range in which the degree of correlation is calculated is the size of the feedback removal window, and the feedback signal detection unit according to the embodiment of the present invention detects a feedback signal for the feedback window determined by the window setting unit.

The feedback signal removal filter 46 generates an anti-phase signal of the feedback signal using the time delay, amplitude and phase estimated by the feedback signal detection unit 47, and applies the generated anti-phase signal to the total input signal. Remove the feedback signal from the input signal. That is, the subtracter 20 is used to subtract the feedback signal detected from the feedback signal removal filter 46 from the total input signal r ′ _in (n) to generate the output signal r _out (n) from which the feedback signal has been removed. .

  The window setting unit 40 includes a window dividing unit 41 and a feedback signal searching unit 42, and grasps the characteristics of the feedback signal to divide and set the feedback removal window.

The feedback signal search unit 42 searches for a window of about N * X _tot size by sequentially adding unit window search functions. FIG. 7 is a diagram illustrating the operation of the feedback signal search unit 42.

Referring to FIG. 7, the feedback removal window X _tot that is the range for calculating the correlation degree is sequentially moved, and the feedback signal is searched in the unit window X _step in the feedback removal window X _tot of Equation 1. That is, the feedback removal window X _tot is sequentially moved to (N * X _tot ), and the feedback signal is searched in the unit window X _step within each feedback removal window. As a result, the feedback signal can be detected N times or more from the existing window only by the sequential window search function without adding a search hardware resource. Here, the feedback removal window X _tot is the size of the feedback removal window defined by hardware resource constraints.

The window dividing unit 41 divides the entire feedback removal window X _tot so that a feedback removal window is assigned to a feedback signal region exceeding a certain boundary value among the feedback signals searched by the feedback signal search unit 42. Further, each divided window is divided into unit windows X _step . The entire window X _tot is divided as shown in Equation 2.
[Formula 2]

However, a _k is a natural number and is a value indicating whether the k-th divided window is composed of several unit windows,
Satisfied.

FIG. 8 shows an example in which the feedback removal window is divided. Referring to FIG. 8, among the feedback signals searched by the feedback signal search unit 42, feedback signal regions exceeding a certain boundary value form three groups. Each divided window is divided into unit windows X _step .

That is, the K value obtained by dividing the feedback removal window is set to 3. Further, a ₁ , a ₂ , and a ₃ are set to ₃ , ₃ , and ₂ , respectively.

The interference cancellation repeater according to the embodiment of the present invention includes a window setting unit 40 and searches for a feedback signal from a region (N * X _tot ) that is N times the size X _tot of the feedback cancellation window. Then, the size X _tot of the entire feedback removal window is divided according to the searched feedback signal. Accordingly, the feedback signal can be effectively removed by setting the feedback removal window in a portion where the influence of the feedback signal is large. In particular, it is possible to effectively remove feedback signals between interference cancellation repeaters that occur outside the region of the feedback cancellation window.

The D / A converter 15 converts the signal r _out (n) from which the feedback signal has been removed by the feedback signal removal unit 48 into r _out (t) in the form of an analog signal. The amplifying unit 16 amplifies the analog output signal r _out (t) converted by the D / A converter 15 by a gain G. At this time, the signal amplified by the amplifying unit 16 can be expressed as G · r _out (t). The transmission antenna 17 is an antenna that transmits the signal G · r _out (t) amplified by the amplification unit 16 to another terminal.

  FIG. 9 is a flowchart illustrating an operation process of an interference cancellation repeater including a feedback cancellation window division function according to an embodiment of the present invention.

First, the total input signal r ′ _int (t) is received from the receiving antenna 12 (S11), and the total input signal r ′ _int (t) is converted into a digital signal (S12). Here, the total input signal r ′ _int (t) is the sum of the source received signal r _in (t), the feedback signal f _intra (t) itself, and the feedback signal f _inter (t) between the repeaters.

  Thereafter, after the window setting stage (P1), the feedback signal is searched for in the window setting stage (S13), and the feedback removal window is divided (S14).

In the feedback signal search step (S13), unit window search functions are sequentially added to search for a window of N * X _tot size, and a feedback signal in the range of N * X _tot is detected. In the feedback removal window division step S14, the entire feedback removal window X _tot is divided so that the feedback removal window is assigned to a feedback signal region exceeding a certain boundary value among the feedback signals searched in the feedback signal search step (S13). . Further, each divided window is divided into unit windows X _step .

  Then, based on the divided windows, a feedback signal is detected from each unit window (S15), and the detected feedback signal is removed (S16).

  The output signal from which the feedback signal has been removed is converted into an analog signal (S17), and the analog output signal is amplified (S18). The amplified signal is transmitted to another terminal (S19).

  The case where the interference cancellation repeater always performs the window setting stage (P1) has been described above. However, in general, the position of the feedback signal is not a parameter whose value is often changed according to time, but is largely determined according to the surrounding installation environment. That is, the position of the feedback removal window is a semi-static parameter that does not need to be updated frequently. Therefore, the window setting floor (P1) may be performed only once when the device power is applied, or may be performed at regular intervals.

In this way, the feedback signal search unit 42 sequentially moves the feedback removal window X _tot as a range for calculating the degree of correlation to N * X _tot, and outputs the feedback signal at the unit window X _step stage within each feedback removal window X _tot . Explore. The window dividing unit 41 divides the feedback removal window into a predetermined number of divided banks composed of a predetermined number of unit windows (for example, when the feedback removal window is 8 μsec and the unit window is 1 μsec, three, three, and two unit windows, respectively) 3), the feed signal can be detected in a section that is at least N times the size of the existing feedback removal window X _{tot using} only the sequential window search function without adding additional search hardware resources. can do.

  In addition to this, a problem that appears when considering feedforward input to the receiving antenna of the interference cancellation repeater via a multipath or another repeater, and a solution to the problem will be described below. A signal that can efficiently remove the feedback signal of the repeater itself or the feedback signal between the repeaters, but also has a correlation degree with respect to the feedback signal of the repeater itself or the signal that is not the feedback signal between the repeaters. May be regarded as a feedback signal and removed. That is, the receiving antenna of the interference cancellation repeater does not receive only the feedback signal of the repeater itself or the feedback signal between repeaters shown in FIG. 3 or FIG. 7, but via the other route from the base station. It can be influenced by incoming delay signals or signals from other repeaters (which can include not only interference cancellation repeaters, but also optical repeaters, microwave repeaters, etc.). The signal obtained by the method in which the multipath signal of the base station or the same source signal is input to the receiving antenna of the interference cancellation repeater via another repeater is not related to the gain of the repeater itself, It becomes an external input signal (hereinafter referred to as a feedforward signal) in which a correlation value appears.

  FIG. 10 shows an example of a signal input via another repeater as an external input signal that is not related to the gain of the repeater itself that receives the RF signal. Referring to FIG. 10, the RF signal input to RU1 is transmitted not only through the input signal 51 from DU and the feedback signal 52 of RU1 itself, but also through RU2, which is another repeater that has received the input signal from DU. It also includes a signal 53 input to RU1. Problems caused by such a feedforward signal can be roughly classified into two.

  First, as shown in FIG. 11, if a feedforward signal 53 input via another repeater is included in the feedback cancellation window 54 instead of the feedback signal 52 itself, it is not distinguished from the feedback signal. It may be removed. However, the feedforward signal 53 is a signal that improves the received SNR when combined with the multipath signal of the receiving terminal. This does not cause self-oscillation and does not need to be removed. In addition, in most feedback signal removal algorithms, when the feedforward signal is located within the feedback removal adaptive filter window, the filter coefficient convergence operation is not performed accurately, which causes a reduction in the performance of the repeater output signal.

Second, when the auto-correlation is obtained in the presence of a feedforward signal, the original feedback signal (represented by reference numerals 521, 522, and 523, as shown in FIG. 12, For convenience of explanation, only three are shown, but this may include all of the feedback signal of the repeater itself and the feedback signal between the repeaters), as well as an image component (drawing reference numeral 521) by the feedforward signal 53. ”, 521 ″, 521 ″, 522 ′, 522 ″, 523 ′, and 523 ″ (hereinafter referred to as“ feedforward image signal ”). Since these signals are image components, there is no need to remove them. However, if the autocorrelation degree of the received signal is used, the feedback signal and the feedforward image signal cannot be distinguished. When removing the signal, a split window is also assigned to the feedforward image signal. However, for example, the feedforward image signals 521 ′ and 521 ″ are signals that are automatically removed when the related feedback signal 521 is removed, and therefore it is not necessary to allocate a separate window resource. In the case of division, since the allocated window size X _tot is smaller than the window size N * X _tot to be searched, if unnecessary window hardware (or software) resources are allocated to the feedforward image signal, the resource constraint causes In some cases, the feedback signal that must be removed cannot be removed, causing oscillation, which may cause the feedforward image signal to have more power than other feedback signals in some circumstances. This is because also. Influence of such feedforward image signals is not only the signal 53 of the feedforward input through the other repeaters, exerted equally to multipath signals of the base station signal.

[Mode of Invention]
Hereinafter, a feedforward signal sequential search and feedforward signal processing method according to an embodiment of the present invention will be described in detail.

  In this section, embodiments of a method for searching for a feedforward signal and a method for not assigning a window to a feedforward signal will be described.

  Of the feedforward signals, a signal received via the link antenna of the interference cancellation repeater via multipath fading of the base station is generally received earlier in time than the feedback signal of the interference cancellation repeater. Therefore, since the signal is formed before the feedback cancellation window, the correlation does not appear in the feedback cancellation window, and thus does not affect the operation of the interference cancellation repeater (however, in this case, the feedforward image signal is generated). This will be described later). However, the feedforward signal 53 obtained by inputting the base station signal via another repeater as shown in FIG. 10 has a long delay time and is located directly in the feedback cancellation window of the interference cancellation repeater. May be. As shown in FIG. 11, according to the technique of the interference cancellation repeater by the method that does not consider the feedforward signal by other repeaters, the algorithm operates in a direction to remove the feedforward signal. Since the algorithm is designed on the assumption that the feedback signal is removed, a problem arises in that the filter coefficients do not converge accurately when the feedforward signal is input. As a result, the quality of the repeater output signal may be greatly degraded. In addition, the feedforward signal is a multipath signal that can increase the reception SNR from the standpoint of a terminal, and is not an oscillation cause signal that increases in magnitude according to the gain of the repeater. Therefore, in the interference cancellation repeater, it is necessary to reset the feedback cancellation window so that the feedforward signal is not canceled.

  For convenience, a description will be given separately for a feedforward signal search / processing method and a feedback signal search / processing method considering a feedforward image signal.

<First Method of Feedforward Signal Processing>
FIG. 13 is a diagram schematically illustrating a feedforward signal processing method in an interference cancellation repeater according to a preferred embodiment of the present invention. As described above, in the interference cancellation repeater, it is necessary to reset the feedback cancellation window so that the feedforward signal is not canceled, so that the feedforward signal is detected and the feedback cancellation window appears after the detected time. When the output signal of the repeater is delayed, the feedforward signal is not removed.

  Since the feedback signal of the repeater itself or the feedback signal between the repeaters is related to the transmission signal of the repeater, when the transmission output signal of the repeater is delayed, the feedback signal is also delayed with the feedback cancellation window. Therefore, as shown in FIG. 13, when the output signal of the repeater is delayed until the feedforward signal 53 appears in front of the feedback removal window 61 of the repeater, the feedforward signal 53 is positioned in front of the feedback removal window. Can be.

  As a method of detecting the feedforward signal, it is sufficient to detect the correlation of the signal input to the link antenna by removing the output of the repeater, but the reason is that the output signal of the repeater is lost. This is because there is no feedback signal. There are many methods for removing the output of the repeater, such as a method of setting the repeater gain to 0 by switching off the amplifier of the repeater, a method of setting the digital signal output as the input of the D / A converter to 0, etc. There can be a realization method. In addition to this, the feed forward signal may be detected by any other method.

<Second method of feedforward signal processing>
FIG. 14 is a diagram schematically illustrating a feedforward signal processing method in an interference cancellation repeater according to another preferred embodiment of the present invention.

  Unlike the first method described above, the second method shown in FIG. 14 is stored when the feedforward signal is detected, the position of the feedforward signal is stored, and the feedback removal window is divided. By avoiding the position of the feedforward signal and dividing / setting the feedback removal window, the feedforward signal is not removed. The division / setting of the feedback removal window is performed not only by the automatic division method but also by the manual division method.

  The method for detecting the feedforward signal 53 is the same as the description method in the first method. In addition, in the feedback cancellation window dividing / setting step, as shown in FIG. 14, two or more feedback cancellation windows are arranged so that the detected feedforward signal 53 is not placed in the feedback cancellation window of the repeater itself. By dividing the bank into 71 and 72, only the feedback signal 52 can be removed.

  However, the above method has a problem that it is difficult to apply when the position of the feedforward signal overlaps with the position of the feedback signal, but this problem is reduced by delaying the system so that the positions of the two signals do not overlap. This can be solved by applying a voltage.

<Third method of feedforward signal processing>
FIG. 15 is a diagram schematically illustrating a feedforward signal processing method in an interference cancellation repeater according to another preferred embodiment of the present invention.

  In the present embodiment, the step of delaying the output signal of the repeater by a certain time (S81), the step of performing the automatic feedback removal window dividing function as described above (S82), and the delay of the set repeater (S83).

In step S81, most of the meaningful feedforward signals are signals that have passed through about 1 to 2 other repeaters, and therefore the corresponding time is set to a certain time T _C (where T _C is the output of the repeater). When the signal is removed, it can have a time longer than the time when the signal input to the link antenna of the repeater is detected, but the maximum delay time due to the delay application limit of the repeater. When the automatic window splitting function is performed after delay application of the repeater and the repeater is set, the feedback of the repeater itself excluding the feedforward signal is performed in the same manner as the first method related to FIG. Only the feedback signal between the signal and the repeater can be removed. However, if the delay of the repeater itself is set to be the same for all repeaters, the feedforward signal received from the other repeater is also received as the signal delayed to the maximum, so in step S83. As described above, it is not effective unless the delay of the repeater set to the maximum previously is restored.

  In the step S82, the feedback signal is searched by moving the feedback cancellation window so that the feedback signal of the repeater itself and the feedback signal between the repeaters can all be removed, and the feedback signal is searched based on the searched feedback signal. Split the feedback removal window. Here, the search for the feedback signal is performed by sequentially moving the feedback cancellation window and searching for the feedback signal in the unit window stage within the feedback cancellation window. The feedback cancellation window is divided from any number of unit windows. It is the same as the method described above, which is performed to include the divided banks.

  However, even in the case of the above method, there is still a problem when the position of the feedforward signal overlaps the position of the feedback signal.

<Fourth method of feedforward signal processing>
FIG. 16 shows a feedforward signal processing method in an interference cancellation repeater according to another preferred embodiment of the present invention.

The feedforward signal processing method in the interference cancellation repeater according to the present embodiment includes the step of setting the output or gain of the repeater to 0 (S91), and the autocorrelation degree R _FF (n) of the repeater radio input signal. A step of measuring (S93), a step of applying a system delay of the repeater (S95), and a step of repeating the steps S94 and S95 until the auto-correlation is remeasured and no feedforward signal is detected. And a step (S96, S97) of setting a maximum value of the system delay and preventing the delay from being set beyond the maximum value.

First, in step S91, a search for a feedback signal is started during a time interval of 0 to N * T _tot with the output or gain of the repeater set to 0 without further delaying the output signal of the repeater (S92). . In step S91, the repeater gain is set to zero using the method of switching off the repeater amplifier as described above, and the digital signal output to be input to the D / A converter is set to zero. However, the present invention is not limited to this. Any method may be used as long as an environment can be created in which only the influence of the feedforward signal on the repeater radio input can be measured without the feedback signal flowing. In the above state, since there is no feedback signal, the presence or absence of a feedforward signal can be detected by measuring the autocorrelation degree R _FF (n) of the input signal.

Thereafter, it is determined whether or not the feedforward signal is present by comparing whether or not the correlation value at the input end measured in step S93 becomes a certain level TH _FF (S94), and it is determined that the feedforward signal is input. If so, an additional delay _Td of the repeater is applied (S95). After applying the additional delay of the repeater, the final delay setting value of the repeater is determined by repeatedly detecting the presence or absence of the feedforward signal by re-measurement of the autocorrelation degree (S94, S95, S99).

In the process of adding the delay value of the repeater, a protection procedure can be provided so that the maximum system delay value _{Td, max} set as in step S96 is not exceeded. The reason why the maximum value T _{d, max} of the system additional delay that can be applied is set is that the delay of the repeater system can affect the reverse soft combining performance of the base station. When the system delay of the repeater is applied larger than the combining length of the base station, the maximum delay value is limited because the softer handover performance can be lowered. If the system delay of the repeater exceeds the maximum delay value, the additional delay value must be returned to a value of 0 to _{Td, max} (S97). After returning, there is a problem because the influence of the residual feedforward signal remains. In this case, when the position of the feedforward signal is stored and the backward feedback signal removal window is divided, an additional function is required to prevent the window from being divided at the corresponding position. Here, with reference to the position search information of the feedback signal, which is a subsequent procedure, if a step of selecting a return delay value from 0 to _{Td, max} so as not to overlap the residual feedforward signal is provided, an exception is made. Problem can be solved.

In addition to measuring the degree of correlation of the input end of the repeater, the method may include detecting whether the wireless input signal of the repeater is initially at an oscillation level (S98). If the radio input signal of the repeater is already in an oscillating state, the following signal search procedure is meaningless, so the setting is terminated and the amplifier is switched off so that oscillation is not propagated to ensure the stability of the network. The oscillation level is detected by measuring the autocorrelation degree R _FF (n) of the input signal, and generally satisfies TH _oscillation > TH _FF .

  In the proposed method, when the feedforward signal is detected using the correlation value and the output signal of the repeater is delayed, the feedforward signal located directly in the feedback cancellation window is removed. A feedback signal search / division procedure can proceed.

  Hereinafter, the influence of the feedforward image signal will be considered.

  By the above process, it is possible to prevent the correlation value due to the feedforward signal from appearing in the feedback cancellation window. However, when the feedback signal exists, the influence of the feedforward signal outside the window may be transformed into the image form of the feedforward signal and appear inside the window.

  FIG. 12 shows an example of how the feedforward image due to the correlation with the Fordback signal affects when the feedforward signal exists outside the feedback cancellation window. In the above example, the condition that one feedforward signal is generated at a distance d from the source signal is shown as an example. The feedforward signal may be a multiple path of the source signal of the base station, or may be a case where the feedforward signal is positioned in front of the window by applying the delay of the repeater (53 in FIG. 13). reference). The example shown in FIG. 12 is a case where there are three feedback signals. When the degree of correlation of the repeater input signal is obtained under the above conditions, as shown in FIG. 12, in addition to the original feedback signals (drawing symbols 521, 522, and 523), an image component (drawing symbol 521) by the feedforward signal 53 is obtained. '521 ", 522', 522", 523 ', 523 "). The feedforward image signal is a signal that is automatically removed if the associated feedback signal is removed, so no additional window resources are allocated. May be.

In the case of automatic window search / division, since the allocated window size X _tot is smaller than the window size N * X _tot to be searched, if unnecessary window hardware (or software) resources are allocated to the feedforward image signal In some cases, a feedback signal that must be removed cannot be removed due to resource constraints, which may cause oscillation. Therefore, the processing for the feedforward image signal is very important, and an algorithm that takes this into consideration will be described in the following procedure.

  Hereinafter, the feedback signal sequential search and the window automatic division considering the feedforward image signal will be considered.

  In this section, an embodiment of a feedback signal sequential search and automatic window division method considering a feedforward image signal will be described.

<Fifth Method of Feedforward Signal Processing>
FIG. 17 shows a feedback cancellation window automatic dividing procedure in the interference cancellation repeater according to another preferred embodiment of the present invention considering the above-described feedforward signal processing. Since the procedure before step S99 in FIG. 17 has already been described above, the automatic search procedure after step S99 will be described in this embodiment.

The feedback cancellation window automatic splitting procedure includes setting the repeater gain to a minimum after turning on the output or gain of the repeater (S99), and removing the feedback of the repeater, and then correlating the signal R A step of moving and measuring _FB (n) (S00), and determining the resource effectiveness as to whether the divided bank of the feedback removal window can be assigned to the position where the largest correlation value exists among the measured correlation values. Step (S101), Step of re-measuring the correlation R _FB (n) of the signal after feedback removal after applying division back subdivision (S102), and all the correlation values within the search range (∀: all) dividing (assigning) an effective bank until a certain level or less is reached and repeating the steps S101 and S102 (S103); A step (S104) the gain of the repeater is increased by a unit gain, in the condition the gain of the repeater is below a certain level _{P ref,} and the step of repeating steps S100 to S104 (S105), the window bank Dividing and setting back to the user Atten before the procedure (S106). Further, when the divided bank resources are exhausted in step S101 and the bank cannot be rearranged, a step of verifying whether one of the correlation values (あ る: one) is at the oscillation level (S108), and oscillation A step of applying an effective division setting before oscillation at the time of detection (S109) may be included.

In the step S100, in the situation where the feedback signal exists, strictly speaking, in the situation where the feedback signal is delayed and the output signal of the repeater is delayed so that the feedback removal window is at a position where the feedforward signal is not removed. Then, the autocorrelation degree R _FB (n) of the signal after feedback removal is measured. In this case, the correlation degree is a correlation value in a situation where a feedback signal removal operation is performed by feedback removal window bank division assigned sequentially.

  In step S101, it is determined whether window bank resources remain. If it is determined that the rearrangement of the divided banks is possible, in step S102, one of the divided banks of the feedback removal window is assigned to the position where the correlation value measured in the search window is the largest, and the corresponding signal is assigned. After removal, the correlation is remeasured.

As described above with reference to FIG. 12, the feedforward image signal is located on both sides of the associated feedback signal. The average power of the correlation value with respect to the feedforward image signal is always 6 dB or less of the associated feedback signal average level, and the 6 dB difference condition occurs when the source reception signal and the feedforward signal are the same. Therefore, when one bank is assigned to the position where the correlation value R _FB (n) after feedback removal is the largest as in step S102, the window bank is assigned to the position of the feedback signal having the largest power. As a result, the feedforward image signal linked to the corresponding feedback signal is automatically removed. That is, valid banks can be sequentially assigned to only the feedback signal in the order of the signal power size through the iterative procedure of steps S101 and S102. It is possible to prevent resources from being allocated to the feedforward image signal.

  On the other hand, in the above-described example, it is determined whether or not the window bank resource remains in step S101, and it has been described that the division bank rearrangement step is performed only when the window bank resource remains, but steps S104 and S105 are performed. After passing through step S101, if the largest correlation value among the re-measured correlation values is larger than the correlation value to which the divided bank is allocated in the previous step, even if no window bank resource remains, step S101 is omitted, and the previous step It is also possible to rearrange the divided banks allocated in (1) at a position where the largest correlation value exists among the remeasured correlation values.

The process is repeated until all (∀: all) correlation values remaining after removal are below a certain level (steps S101 to S103). In this embodiment, the constant level is a TH _{G-20 dB} condition in which an EVM (Error Vector Magnitude) is 10% or less (that is, after feedback removal, the feedback signal is less than 20 dB from the repeater gain). However, it is obvious to those skilled in the art that the threshold value can be limited so as to meet each mobile communication standard. For reference, in the case of a WCDMA system, the EVM standard is 12.5%. In this case, the condition may be limited to TH _{G-18 dB} . Residual bank resources are continuously allocated to the position where the largest correlation value exists among the remeasured correlation values.

If all the re-measured correlation values are less than a certain level TH _{G-20 dB} , the gain of the repeater itself is increased by a unit gain (Gain-step) (step S104), and the output of the repeater is increased. The divided bank rearrangement process is repeated until a predetermined output [output power> min {P _ref , P _shutdown }] is reached (step S105). The search probability can be increased through the procedure of repeatedly measuring the gain of the repeater and the overall operation stability can be ensured. This is because the feedback signal to be searched increases as the repeater gain increases.

On the other hand, if it is determined that the division bank resources in the feedback removal window usable in step S101 are exhausted and the rearrangement of the division banks is impossible, it is possible to generate oscillation among the remaining correlation values. It is determined whether or not there is one correlation value (あ る: one) that is equal to or higher than the oscillation start level TH _oscillation (step S108). If there is no correlation value equal to or higher than the oscillation start level TH _oscillation , the possibility of oscillation is small, and the gain of the repeater itself continues to be a predetermined output [Output> min {P _ref , P _shutdown ] through step 104. ], The divided bank rearrangement process is repeated. If a correlation value equal to or higher than the oscillation start level TH _oscillation is detected, the gain of the repeater immediately before the oscillation level is indicated using the window division information based on the stored pre-oscillation feedback removal window arrangement. After the window division information is applied, the installation process ends (steps S109 and S110).

If the gain of the repeater itself exceeds a predetermined output [output power> min {P _ref , P _shutdown }] in step S105, the feedback cancellation window is divided and set based on the arrangement of the last set window bank, The search for the feedback signal is terminated (steps S106 and S107).

  According to the present embodiment, it is possible to prevent a shortage of window resources that may occur due to the image component of the feedback signal due to the presence of the feedforward signal, and it is possible to efficiently use resources.

<Sixth Method of Feedforward Signal Processing>
FIG. 18 shows an automatic division procedure in the interference cancellation repeater according to another preferred embodiment of the present invention.

  In the present embodiment, since it is substantially the same as the case of the fifth method described above, the difference will be mainly described below.

In this embodiment, the step of measuring the convergence coefficient power P _Coeff (n) according to the movement search of the additional feedback removal adaptive filter of the _repeater (S100 ′), of the measured filter coefficient power P _Coeff (n) Assigning a partition bank so that any one of the partition banks of the feedback cancellation window is located at a position where the largest value exists (S102 ′); after allocation / application of the partition bank, a convergence coefficient of the feedback cancellation adaptive filter After re-measuring the power P _Coeff (n), dividing and assigning valid banks until all of these values are below a certain level and repeating the third step (S103 ′, S101, S102 ′), and until said repeater gain is below a certain level P _ref, increasing the gain of the repeater by a unit gain It is not the step S100 in ', S101, S102', comprising the step (S105) repeating the S103 'and S104.

  In the fifth method, the feedback signal automatic movement search is performed using the correlation degree of the signal after the feedback removal. However, in this embodiment, the movement search procedure using the feedback removal adaptive filter is used instead. After convergence of most adaptive filters including a feedback removal adaptive filter of LMS (Least Mean Square) sequence, the filter coefficient becomes a complex value reflecting the magnitude of the feedback signal at the position of the feedback signal, and feedforward No coefficient is generated at the position of the image signal. That is, in the case of the above procedure, when the autocorrelation value is calculated, a feedforward image signal that can only be mathematically derived is not generated, so that there is no need to sequentially assign banks for feedforward image signal processing.

  However, since an adaptive filter for mobile search must be added separately from the original feedback removal adaptive filter for the above procedure, the hardware (or software) complexity increases in implementation. The search for the position of the feedback signal is based on the power of the adaptive filter complex coefficient, and since the rest is the same as the procedure of the fifth method, its description is omitted.

  FIG. 19 is a diagram schematically showing a configuration of an interference cancellation repeater according to a preferred embodiment of the present invention.

  Referring to FIG. 19, an interference cancellation repeater according to a preferred embodiment of the present invention includes a feedback signal search / division / removal unit 400 and a feedforward signal search / system delay unit 406, and the remaining components. Is the same as the conventional case, and each component can be appropriately employed to perform each method described in each of the above-described embodiments, and therefore, detailed description thereof is omitted for convenience.

The feedforward signal search / system delay unit 406 searches for a feedforward signal using the correlation degree of the radio input signal received through the link antenna 12 after setting the system gain of the repeater to 0, for example. A forward signal searcher R _FF (n) 404 and a system delay unit 405 for adding the above-described repeater delay according to the time delay of the searched feedforward signal.

  The feedback signal search / division / removal unit 400 includes a feedback signal searcher 403 that searches for a feedback signal using a correlation value shift search method or an adaptive filter shift search method, and the searched feedforward signal and feedback signal. A feedback removal window dividing unit 402 for dividing and setting a feedback removal window so that a window is not assigned to the feedforward signal or the image signal of the feedforward signal, and the feedback removal divided by the feedback removal window And a feedback signal removal filter 401 for removing a feedback signal from the received RF signal based on the window.

  The components of the feedforward signal search / system delay unit 406 and the feedback signal search / division removal unit 400 are for performing the functions described in connection with the above-described embodiments, Hardware, software, or a combination thereof.

  The preferred embodiments of the present invention have been described in detail above, but these are only for explaining the embodiments of the present invention, and various modifications can be made by those skilled in the art. Ultimately, the scope of the present invention should be defined by the appended claims.

Claims (17)

In a repeater that removes interference due to feedback signals,
By moving the feedback cancellation window, the feedback signal is searched from the RF signal received via the receiving antenna and including the feedback signal itself and the feedback signal between the repeaters, and feedback cancellation is performed based on the searched feedback signal. A window setting section for dividing the window (X _tot );
A feedback signal removing unit that removes a feedback signal from the received RF signal based on the feedback removal window divided by the window setting unit ;
Including
The window setting unit
A feedback signal search unit that receives the received RF signal, sequentially moves a feedback removal window (X _tot ), and searches for a feedback signal;
Of the searched feedback signals, a feedback cancellation window is assigned to a feedback signal region exceeding a certain boundary value, a divided feedback cancellation window is set, and the divided feedback cancellation window is set as a unit window (X _step ). And a window dividing unit to be divided into
The feedback signal search unit includes:
The feedback cancellation window (X _tot ) is sequentially moved, and a feedback signal is searched in a unit window (X _step ) within the feedback cancellation window (X _tot ) ,
The feedback removal window (X _tot ) is a sum of M (where M is a natural number) unit windows (X _step ),
The window dividing unit includes:
The feedback removal window (X _tot )
(Where a _k is a natural number and is a value indicating whether the k-th divided window is composed of several unit windows,
Satisfied. )
The feedback signal removal unit includes:
A time delay of a feedback signal using a degree of correlation between the received RF signal and a signal from which feedback generated previously is removed at a position of a unit window (X _step ) divided by the window divider ; A feedback signal detector for estimating amplitude and phase;
A feedback signal removal filter that generates an anti-phase signal of the feedback signal estimated by the feedback signal detector and removes the feedback signal from the received RF signal using the generated anti-phase signal;
Including
A link antenna that receives an RF signal including a feedback signal and feedforward;
A feedforward signal searcher for searching for a feedforward signal among the RF signals received via the link antenna;
A system delay unit for adding a system delay of the repeater so that the detected feedforward signal is not included in the feedback cancellation window ;
A repeater comprising: Characterized in that it further comprises an amplifier for amplifying only gain feedback signal is preset signal has been removed by the feedback signal removing filter, repeater of claim 1. A feedback signal searcher for searching for a feed signal among RF signals received via the link antenna;
A feedback removal window dividing unit for dividing and setting a feedback removal window based on the searched feedforward signal and the feedback signal so that no window is assigned to the feedforward signal or the image signal of the feedforward signal; ,
A feedback signal cancellation filter for removing a feedback signal from the received RF signal based on a feedback cancellation window divided by the feedback cancellation window;
And further comprising a repeater according to claim 1 or 2. In a method of removing interference due to a feedback signal in a repeater,
By moving the feedback cancellation window, it is received via the receiving antenna, and searches the feedback signal from the RF signal including a feedback signal between itself feedback signal and the repeater, feedback based on the search feedback signal A window setting stage for dividing the removal window (X _tot );
Detecting and removing a feedback signal from the received RF signal based on the feedback cancellation window divided in the window setting step ;
Only including,
The window setting step includes:
A feedback signal search step of receiving the received RF signal and sequentially moving a feedback cancellation window (X _tot ) to search for a feedback signal;
Of the searched feedback signals, a feedback cancellation window is assigned to a feedback signal region exceeding a certain boundary value, a divided feedback cancellation window is set, and the divided feedback cancellation window is set as a unit window (X _step ). A window splitting stage ,
The feedback signal search step includes
The feedback cancellation window (X _tot ) is sequentially moved, and a feedback signal is searched in a unit window (X _step ) within the feedback cancellation window (X _tot ) ,
The feedback removal window (X _tot ) is a sum of M (where M is a natural number) unit windows (X _step ),
The window dividing step includes:
The feedback removal window (X _tot )
(Where a _k is a natural number and is a value indicating whether the k-th divided window is composed of several unit windows,
Satisfied. )
Detecting and removing the feedback signal comprises:
A time delay of a feedback signal using a degree of correlation between the received RF signal and a signal from which a previously generated feedback is removed at a position of a unit window (X _step ) divided in the window division step ; A feedback signal detection stage to estimate amplitude and phase;
Generating a reverse phase signal of the feedback signal estimated in the feedback signal detection step, and using the generated reverse phase signal, removing a feedback signal from the received RF signal; and
Including
Receiving an RF signal including a feedback signal and a feedforward signal via a link antenna of an interference cancellation repeater that removes the feedback signal using a feedback cancellation window;
Detecting the feedforward signal;
Removing the feedback signal by resetting the feedback removal window such that the detected feedforward signal is not included in the feedback removal window;
An interference canceling method comprising: The interference cancellation method of claim 4 , further comprising amplifying the signal from which the feedback signal is removed by the feedback signal cancellation filter by a preset gain. The method of claim 4 , wherein the feedback signal includes a feedback signal of the repeater itself and a feedback signal between the repeaters. Detecting the feedforward signal comprises:
Setting the output or gain of the repeater to zero;
Mobile search and measurement of the autocorrelation of the RF signal received via the link antenna;
The interference cancellation method according to claim 4 , further comprising: Resetting the feedback cancellation window to remove the feedback signal comprises:
The interference cancellation method according to claim 4 , wherein the interference cancellation method is performed by delaying an output signal of the repeater so that the feedback cancellation window appears after a detection time of the detected feedforward signal. Resetting the feedback cancellation window to remove the feedback signal comprises:
The interference cancellation method according to claim 4 , wherein the feedback cancellation window is manually divided into a certain number so that the detected feedforward signal is not included in the feedback cancellation window. Resetting the feedback cancellation window to remove the feedback signal comprises:
When removing the output of the repeater, delaying the output of the repeater for a time longer than the time when a signal input to the link antenna is detected;
Moving the feedback cancellation window to search for a feedback signal;
Dividing the feedback cancellation window based on the searched feedback signal;
Restoring the repeater delay to its original state;
The interference cancellation method according to claim 4 , further comprising: Detecting the feedforward signal comprises:
A first step of setting the output or gain of the repeater to zero;
A second step of measuring and measuring the autocorrelation of the radio input signal received via the link antenna;
Applying a third system delay of the repeater;
A fourth step of re-measuring the autocorrelation and repeating the second and third steps until no feedforward signal is detected to further apply a system delay;
The interference cancellation method according to claim 4 , further comprising: The method of claim 11 , wherein the dividing the feedback cancellation window does not allocate a window bank resource to the feedforward image signal. Dividing the feedback removal window comprises:
A fifth step of setting the gain of the repeater to a minimum;
A sixth stage of mobile search and measurement of the correlation degree [R _FB (n)] of the signal after feedback removal of the repeater;
A seventh step of allocating divided banks so that any one of the divided banks of the feedback removal window is located at a position where the largest correlation value exists among the measured correlation values;
After the window division bank assignment, the correlation degree [R _FB (n)] after removing the feedback is measured again, and then the seventh step is repeated by assigning valid banks until the correlation values are all below a certain level. The eighth stage,
A ninth step of repeating the sixth to eighth steps by increasing the gain of the repeater by a unit gain until the gain of the repeater becomes equal to or less than a certain level (P _ref );
The interference cancellation method according to claim 12 , further comprising: Dividing the feedback removal window comprises:
A tenth step of setting the gain of the repeater to a minimum;
An eleventh step of mobile search / measurement of feedback filter adaptive filter coefficient power of the repeater;
A twelfth step of allocating the division banks so that any one of the division banks of the feedback cancellation window is located at a position where the largest value of the measured adaptive filter coefficient powers exists;
After the division bank assignment / application, after the adaptive filter coefficient power after feedback removal is remeasured, the effective bank is divided / assigned until all are below a certain level, and the step 12 is repeated. A fourteenth stage of repeating the first to thirteenth stages by increasing the gain of the repeater by a unity gain until the gain of the repeater falls below a certain level (P _ref );
The interference cancellation method according to claim 12 , further comprising: The interference cancellation method according to claim 13 or 14 , characterized in that the search and division of the feedback cancellation window are performed at an initial installation time or at the request of a user. The interference cancellation method according to claim 13 or 14 , wherein the search and division of the feedback cancellation window are separately performed in the forward direction and the backward direction. The interference cancellation according to claim 13 or 14 , wherein search and division of the feedback cancellation window are performed only in the forward direction or the backward direction, and the information of the division is set to be the same in the backward direction or the forward direction, respectively. Method.