KR100902609B1 - Method for Searching Feedforward/Feedback Signal and Dividing Feedback Cancellation Window And Interference Cancellation Repeater Using the Same - Google Patents

Abstract

The present invention relates to a feedback elimination window splitting method considering both a feed forward and a feedback signal, and more particularly to an oscillation elimination repeater using the same. The present invention relates to a method of searching for a feed forward and feedback signal, and a method of splitting a feedback cancellation window and an oscillation cancellation relay using the same.

The feed forward and feedback signal search and feedback cancellation window partitioning method according to the present invention for achieving the above object, the feedback signal and the feed forward signal through the link antenna of the oscillation removal repeater to remove the feedback signal using the feedback cancellation window Receiving a wireless signal comprising a; Detecting the feedforward signal; And removing the feedback signal by resetting the feedback elimination window so that the detected feedforward signal is not included in the feedback elimination window.

Oscillation elimination repeater, interference elimination repeater, feedback signal, feedforward signal, window splitting, oscillation detection

Description

Feedforward and Feedback Signal Searching and Feedback Cancellation Window Segmentation Method and Oscillation Elimination Repeater Using It {Method for Searching Feedforward / Feedback Signal and Dividing Feedback Cancellation Window And Interference Cancellation Repeater Using the Same}

The present invention relates to a feedback elimination window splitting method considering both a feed forward and a feedback signal, and more particularly to an oscillation elimination repeater using the same. The present invention relates to a method of searching for a feed forward and feedback signal, and a method of splitting a feedback cancellation window and an oscillation cancellation relay using the same.

Since the introduction of the cellular system using the AMPS method, domestic mobile communication has been rapidly developed while commercializing the world's first mobile communication service using the CDMA method. In particular, IMT-2000 system, the next generation mobile communication, is expected to increase its market by providing multimedia services such as high-speed and high-definition video services in the current voice service and low-speed data service. However, in IMT-2000, using a higher frequency band than the current cellular band or PCS band, the cell radius that a base station can serve is reduced. In addition, even in a downtown area, even if a base station is installed based on a narrow cell radius, a radio wave shadow area due to a radio interference such as a building exists. In order to solve this problem, it is more economical to use a relatively low cost repeater than to install a lot of expensive base station equipment.

Repeaters can be classified into optical repeaters, microwave terrestrial repeaters, variable frequency repeaters using frequency conversion, and variable frequency repeaters (general RF repeaters).

An optical repeater converts an RF signal of a base station into an optical signal and transmits it to an optical line that is already buried, and then converts the optical signal into an RF signal in the repeater. However, the optical repeater can be installed wherever the optical line can be pulled in, but the disadvantage is that the optical line rental cost is high and the service can be provided only where the optical line is inserted.

A microwave terrestrial repeater is a method of transmitting a base station signal after converting it into a radio wave of a high frequency in a donor unit (hereinafter referred to as "DU"). Microwave terrestrial repeater has the advantage of easy installation, but has the disadvantage that it must be installed in a location where it is affected by weather conditions and secured line of sight.

The variable repeater repeats the transmission signal after converting it to one of the licensed frequencies which are not currently used. Unlike conventional repeaters, which rely only on the characteristics of RF signals, variable repeaters are used by modifying the characteristics of base stations that are currently in use, and are easy to install, simple to implement, and free from oscillation. There is a disadvantage in that it is necessary to operate at half the frequency utilization efficiency. In particular, when only four carriers (FA) can be used per carrier, such as WCDMA, only two carriers can be serviced, so the use is practically limited.

On the other hand, since the variable frequency repeater uses the same frequency between the transmission and reception, unlike the variable repeater is the most common type of RF relay that can be easily implemented. However, there is a disadvantage that the oscillation may occur due to the amplified signal fed back from the repeater. Therefore, in the current unmodified repeater, as a method for suppressing the oscillation of the relay signal, the distance between the transmitting and receiving antennas of the unmodified repeater is separated far enough to secure the isolation between the antennas and the output within the range without oscillation. Restrictive method is used. However, in an environment in which the transmit / receive antennas cannot be sufficiently separated by a desired distance, or in an environment requiring high gain, many problems occur in the use of the variable frequency repeater.

To solve this problem, an Interference Cancellation System (ICS) is used to detect and remove feedback signals that cause oscillation.

Figure 1 schematically shows the configuration of the oscillation removing repeater according to the prior art.

In the following description of the present specification including FIG. 1, the description will be made based on the forward link, but it will be apparent to those skilled in the art that the same applies to the reverse link.

Remove the oscillation of the prior art as illustrated in the first repeater transmission signal [r _in (t)] and the time-varying multi-path feedback signal input through the fading channel, a feedback channel from the base station (11) [f _intra (t Receiving antenna 12 (hereinafter referred to as a 'link antenna'), and an A / D converter 13 for converting a signal received at the link antenna 12 into a digital signal [r ' _in (n)]. , The digital signal processor 14 for removing the feedback signal f _intra (t) among the radio signals received by the link antenna 12, and converts the signal from which the feedback signal is removed to an analog signal r _o (n). The D / A converter 15, the amplifier 16 for amplifying and outputting the analog signal converted by the D / A converter 15 by a predetermined system gain G, and the received signal from the base station Includes a transmit antenna 17 (hereinafter referred to as a 'service antenna') for transmitting to the base station It is done by

The digital signal processor 14 is a feedback signal searcher (R _FB ) 19 for estimating the time delay, amplitude, and phase of the feedback signal using a correlation of the received wireless input signal, and time-varying time. -varying) It consists of a feedback signal cancellation filter 18 that adaptively estimates and removes the feedback signal to remove the feedback signal that causes the oscillation, and the hardware of the feedback signal removal filter that can be implemented is limited. The delay time of the 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 according to the distance of the removable feedback signal is shown in Table 1. Because feedback signal levels rarely cause oscillations due to path loss, the size of the feedback cancellation window can be considered as such. And it is designed.

Delay time Use One 1.67 3.33 4 6 8 Chip 3.84 6.4 12.8 15.38 23.04 30.72 Distance (Km) Round-trip 0.3 0.5 One 1.2 1.8 2.4 One-way 0.15 0.25 0.5 0.6 0.9 1.2

2 illustrates a method of setting / operating a feedback cancellation window in a conventional oscillation cancellation relay. In general, the feedback signal up to X _tot (usec) can be removed based on the repeater's own equipment delay time, but the feedback signal received after X _tot (usec) cannot be removed. do. For example, according to Table 1, when X _tot is designed as 8usec, only feedback signals up to about 2.4 km can be eliminated. In general, the feedback signal detection connects the unit _steps of the X _step size in a sequential or parallel manner to search the entire rejection window. That is, the total window size X _tot that can be removed may be expressed as the sum of M unit (where M is a natural number) unit windows (X _step ), and the unit window is referred to as a bank.

On the other hand, the oscillation elimination repeater is a kind of RF repeater, a phenomenon may occur that exchanges signals with other RF repeaters around. In particular, according to Korea's mobile communication network configuration, there are many environments in which distances between installed repeaters are close. As such, when a feedback loop is formed by transmitting and receiving signals between repeaters when the distance between the repeaters is short, since the delay time of the repeater itself is included in the feedback path, the feedback signal between the repeaters is formed outside the feedback removal window area (X _tot ). May occur.

3 illustrates a case where a feedback loop between repeaters is formed when the oscillation elimination repeater is used. When the oscillation elimination repeater is operated, for example, in cascade, the repeater at the front end is called a donor unit (DU), and the repeater at the rear end is called 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 feedback signal between the repeaters [f _inter (t)] is never generated because the path loss of the signal level at which the signal is re-input from the RU to the DU is small. It cannot be ignored. In addition, even in consideration of the front / rear ratio of the antenna, a feedback loop is formed between repeaters in an environment where the influence of path loss with distance is relatively small, and the feedback signal between repeaters is a feedback signal of the repeater itself described with reference to FIG. 2. It may be located outside the feedback removal window area to remove the oscillation.

In general, however, considering that the size of the feedback cancellation window is limited to increase its size due to the limitation of the hardware resources of the repeater, the present inventors can increase the size of the repeater itself without increasing the size of the conventional feedback cancellation window. Korean Patent Application No. 2007-007790 filed an oscillation elimination repeater and method including an automatic feedback elimination window splitting function capable of eliminating oscillation caused by a feedback signal between repeaters as well as a feedback signal.

Figure 4a schematically shows the configuration of the oscillation elimination repeater described in the Korean Patent Application No. 2007-007790. Referring to FIG. 4A, the oscillation cancellation repeater described in Korean Patent Application No. 2007-007790 includes a feedback signal search / split / remove unit 40. The feedback signal search / segmentation / removal unit 40 is a feedback signal searcher 43 for searching for a feedback signal by moving a feedback removal window in a wireless signal including a feedback signal of the repeater itself and a feedback signal between the repeaters. The received rejection window splitter / setter 42 divides the feedback _canceler window X _tot based on a feedback signal and the received feedback _canceler window split by the feedback _canceler window splitter / setter 42. The feedback signal removing filter 41 removes the feedback signal from the wireless signal.

4B is a diagram illustrating an operation of the prior art feedback signal searcher 43. Referring to this, the feedback signal searcher 43 sequentially returns a feedback removal window X _tot , which is a range for calculating a correlation. * X _{tot is} moved, and the feedback signal is searched in the unit window (X _step ) within each feedback removing window (X _tot ). The window dividing unit 21 may include three, three, and two, respectively, for a predetermined number of divided banks having a feedback removing window having a predetermined number of unit windows (for example, if the feedback removing window is 8usec and the unit window is 1usec). Into three division banks including two unit windows. Therefore, according to the above-described prior art, it is possible to detect the feedback signal at a maximum of N times or more of the size X _tot of the existing feedback removing window only by the sequential window searching function without adding the search hardware resource.

According to the above-described oscillation canceling repeaters, the feedback signal of the repeater itself or the feedback signal between the repeaters can be efficiently removed, but also for a signal that is not the feedback signal of the repeater itself or the feedback signal between the repeaters. There is a problem that all correlation signals are regarded as feedback signals and removed.

That is, in the reception antenna of the oscillation elimination repeater, not only the feedback signal of the repeater itself or the feedback signal between the repeaters as shown in FIG. 3 or FIG. 4A is received, but also a delay signal or another repeater inputted through another path from the base station ( This is affected by signals from the oscillation elimination repeater, as well as from optical repeaters, microwave repeaters, and the like. The multipath signal of the base station or the same source signal is input through the other repeater to the receiving antenna of the oscillation elimination repeater, regardless of the repeater's own gain, but the external input signal showing the self-correlation of the received signal Forward signal).

FIG. 5A illustrates an example of a signal input through another repeater as an external input signal independent of the gain of the repeater itself receiving the radio signal. Referring to FIG. 5A, the radio signal input to RU1 is inputted to RU1 via RU2, which is an input signal 51 from DU and RU1's own feedback signal 52, as well as another repeater that receives an input signal from DU. The input signal 53 is also included. The problems caused by this feedforward signal can be summarized into two main categories.

First, as illustrated in FIG. 5B, if the feedforward signal 53 coming through a repeater other than the self feedback signal 52 is included in the feedback cancellation window 54, the feedback signal may be separated from the feedback signal. . However, the feedforward signal 53 is a signal that improves the reception SNR when combined with the multipath signal of the reception terminal, which does not need to be removed because it does not cause self-oscillation. In addition, in most feedback signal cancellation algorithms, when the feedforward signal is located in the feedback cancellation adaptive filter window, the filter coefficient convergence operation is not performed correctly, which causes the performance of the repeater output signal to be degraded.

Second, when the feedforward signal is present, auto-correlation is obtained. As shown in FIG. 5C, the original feedback signal (refer to reference numerals 521, 522, and 523) is shown for convenience of description. Although shown, this may include both the repeater itself feedback signal and the inter-repeater feedback signal), as well as the image components (Figs. 521 ', 521 ", 522', 522", 523 ', 523 "by the feedforward signal 53. Since these signals are image components, they do not need to be removed, but the autocorrelation of the received signal cannot distinguish the feedback signal from the feedforward image signal. In the case of removing the feedback signal by using, a split window is also assigned to the feedforward image signal. The unknown signals 521 ′ and 521 ″ are signals that are automatically removed when only the related feedback signal 521 is removed. Therefore, a separate window resource may not be allocated. Since the allocated window size (X _tot ) is small compared to the window size (N * X _tot ), if unnecessary window hardware (or software) resources are allocated to the feedforward image signal, the feedback signal must be removed due to resource constraints. This may cause the oscillation to occur because the feed forward image signal may have a larger power than other feedback signals, depending on the environment. In addition to the signal (53) of the feed forward incoming through the multipath signal of the base station signal Affects work.

The present invention has been made to solve the problems of the prior art as described above, by eliminating only the feedback signal except the feed forward signal and the feed forward image signal in the oscillation elimination repeater feed forward that prevents degradation of the quality of the received signal And a method for searching for a feedback signal, a method for splitting a feedback cancellation window, and an oscillation cancellation relay using the same.

According to a first aspect of the present invention, a feed forward and feedback signal search and feedback cancellation window splitting method includes a feedback signal through a link antenna of an oscillation cancellation repeater that removes a feedback signal using a feedback cancellation window. And receiving a wireless signal comprising a feedforward signal; Detecting the feedforward signal; And removing the feedback signal by resetting the feedback elimination window so that the detected feedforward signal is not included in the feedback elimination window.

Here, the feedback signal may include a self feedback signal of the repeater and a feedback signal between the repeaters.

The detecting of the feedforward signal may include setting an output or a gain of the repeater to zero; And moving searching and measuring a magnetic correlation of a wireless input signal received through the link antenna.

In addition, resetting the feedback cancellation window to remove the feedback signal may be performed by delaying an output signal of the repeater so that the feedback removal window appears after a detected time of the detected feedforward signal.

The resetting of the feedback cancellation window to remove the feedback signal may be performed by manually dividing the feedback removal window into a predetermined number so that the detected feedforward signal is not included in the feedback removal window.

The resetting of the feedback cancellation window to remove the feedback signal may include delaying an output of the repeater for more than a time when a signal input to the link antenna is detected when the output of the repeater is removed; Searching for a feedback signal by moving the feedback cancellation window; Dividing the feedback cancellation window based on the found feedback signal; And restoring the delay of the repeater to its original state.

The searching of the feedback signal may include searching the feedback signal by sequentially moving the feedback removing window.

The dividing of the feedback elimination window may include dividing and setting the feedback elimination window in a continuous or discontinuous manner using a division bank composed of any number of unit windows.

The detecting of the feedforward signal may include: a first step of setting an output or a gain of the repeater to zero; Moving searching and measuring an autocorrelation of a wireless input signal received through the link antenna; Applying a further system delay of the repeater; And a fifth step of additionally applying a system delay by repeatedly measuring the autocorrelation and repeating the third and fourth steps until no feedforward signal is detected.

In the detecting of the feedforward signal, the fifth step may be repeated until a maximum value of a predetermined system delay is reached.

The detecting of the feedforward signal may include: restoring the additional system delay to a state before the maximum value when the additional system delay caused by the feedforward signal becomes greater than or equal to the maximum value; And verifying whether the input signal is an oscillation signal while applying the restored system delay.

In the splitting of the feedback cancellation window, the window bank resource may not be allocated to the feedforward image signal.

The dividing the feedback cancellation window may include: a sixth step of setting a minimum gain of the repeater; A seventh step of searching for and measuring the correlation of the signal [R _FB (n)] after removing the feedback of the repeater; An eighth step of allocating the division banks so that one of the division banks of the feedback cancellation window is located at a position where the largest correlation value among the measured correlations exists; A ninth step of repeating the third step after allocating the valid banks by re-measuring the correlation [R _FB (n)] after removing the divided banks and allocating valid banks until the correlation values are all below a predetermined level. ; And a tenth step of repeating the seventh to ninth 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 predetermined level P _ref .

The method may further include determining whether a residual correlation value equal to or greater than the oscillation start level of the repeater exists when the divided bank resource to be allocated in the eighth step is exhausted and relocation of the divided bank is not possible. If there is no correlation value higher than the start level, the gain of the repeater is increased by unit gain, and the steps 7 and 9 are repeated, and if there is a correlation value higher than the oscillation start level of the repeater, it is stored. The feedback gain before oscillation may be indicated by using window partitioning information as a window arrangement, and the feedback signal may be removed by applying the window partitioning information.

Further, when the divided bank resource to be allocated in the eighth step is exhausted and the largest correlation value among the correlations remeasured in the ninth step is larger than the correlation value to which the divided bank is allocated in the eighth step, The divided bank allocated in the eighth step may be rearranged at a position where the largest correlation value exists among the correlations measured in the ninth step.

Meanwhile, dividing the feedback cancellation window may include: an eleventh step of setting a minimum gain of the repeater; A twelfth step of moving search / measurement of coefficient power by the feedback cancellation adaptive filter of the repeater; A thirteenth step of allocating a division bank so that 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; A fourteenth step of repeating the thirteenth step after allocating / applying the divided banks, dividing / allocating the valid banks until all are below a predetermined level after re-measurement of adaptive filter coefficient power after removing feedback; And a fifteenth step of repeating the twelfth to fourteenth steps by increasing the gain of the repeater by a unit gain until the repeater gain is equal to or less than a predetermined level P _ref .

The method may further include determining whether there is a residual count power value equal to or greater than the oscillation start level of the repeater when the division bank resource to be allocated in the thirteenth step is exhausted and the division bank is not relocated. If there is no count power value higher than the oscillation start level, the gain of the repeater is increased by unit gain, and the steps 12 and 14 are repeated, and if there is a count power value higher than the oscillation start level of the repeater, it is stored. It is also possible to indicate the repeater gain immediately before the oscillation level by using the window division information in the feedback removal window arrangement before the oscillation, and to remove the feedback signal by applying the window division information.

In addition, the feedback removal window search and division may be performed in real time, or may be performed at the initial installation of a repeater or upon user's request.

In addition, the feedback elimination window search and division may be performed separately in the forward direction and the reverse direction, or may be performed only in the forward direction or the reverse direction, and the partition information may be set to be the same in the reverse direction or the forward direction, respectively.

In addition, the oscillation canceling repeater according to the second aspect of the present invention for achieving the above object is to remove a feedback signal by using a feedback cancellation window, a link for receiving a radio signal including a feedback signal and a feedforward signal antenna; A feedforward signal searcher for searching for a feedforward signal among wireless signals received by the link antenna; And a system delay unit for adding a system delay of the oscillation elimination repeater such that the detected feedforward signal is not included in the feedback elimination window.

The oscillation removing repeater may further include: a feedback signal searcher searching for a feedback signal among wireless signals received by the link antenna; A feedback elimination window dividing unit for dividing and setting a feedback elimination window so that no window is allocated to the feed forward signal or the image signal of the feed forward signal based on the found feed forward signal and the feedback signal; And a feedback signal cancellation filter for removing a feedback signal from the received wireless signal based on the feedback cancellation window divided by the feedback cancellation window.

According to the present invention, the oscillation elimination repeater separates the feedforward signal and the feedback signal to remove only the feedback signal except the feedforward signal, thereby preventing deterioration of the quality of the received signal.

In addition, according to the present invention there is an effect that can remove only the feedback signal excluding the feedforward signal while using the existing configuration of the conventional oscillation elimination repeater without the need to add another configuration.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. For convenience, the feedforward signal searching / processing method and the feedback signal searching / processing method considering the feedforward image signal will be described separately. In the following description, only the forward direction will be described. However, it should be noted that the reverse direction may be the same as the forward direction or may be applied separately from the forward direction. In addition, although the embodiments to be described below may be performed in real time, it is also noted that it may be performed on-demand at the initial installation of the repeater or at the request of a user.

1. Feed Forward Signal Sequential Search and Feed Forward Signal Processing Method

This section describes embodiments of a feedforward signal search and a method of not allocating a window to the feedforward signal.

The signal received by the link antenna of the oscillation elimination repeater through the multipath fading of the base station among the feedforward signals generally comes in time before the feedback signal of the oscillation elimination repeater. Therefore, since the signal is formed before the feedback cancellation window, the correlation does not appear in the feedback cancellation window so that it does not affect the operation of the oscillation elimination repeater (in this case, a feedforward image signal may be generated, which will be described later). ). However, as shown in FIG. 5A, the feedforward signal 53 inputted through another repeater may be located directly within the feedback cancellation window of the oscillator. As shown in FIG. 5B, according to the conventional oscillation elimination repeater technology, the algorithm operates in a direction to remove the feedforward signal, but since the oscillation elimination algorithm is designed assuming the feedback signal elimination, the filter coefficient is input at the feedforward signal input. Problems arise that do not converge correctly. This can greatly degrade the quality of the repeater output signal. In addition, the feedforward signal is a multipath signal that can increase the received SNR from the terminal's point of view, and is not an object of removal because the feedforward signal is not an oscillation cause signal whose magnitude increases with the repeater gain. Therefore, in the oscillation eliminator, it is necessary to reset the feedback elimination window so that the feedforward signal is not eliminated.

The first embodiment describes a method of delaying the output signal of the repeater so that the oscillation elimination repeater is not influenced by the feedforward signal, and the second and third embodiments describe another method. The feedforward signal searching / processing methods of the second and third embodiments have problems in special cases, but may be included in the claims of the present invention because they have simple advantages in implementation. The fourth embodiment is the main idea of the present invention in a manner complementing the first embodiment.

<First Embodiment>

FIG. 6 is a diagram schematically illustrating a feedforward signal processing method in an oscillation cancellation repeater according to a first exemplary embodiment of the present invention. As described above, in the oscillation elimination repeater, it is necessary to reset the feedback elimination window so that the feed forward signal is not removed, and if the output signal of the repeater is delayed so that the feedback elimination window appears after the detected time is detected, The forward signal is not eliminated.

Since the repeater self feedback signal or the feedback signal between the repeaters is related to the repeater transmission signal, delaying the transmission output signal of the repeater also delays the feedback signal with the feedback cancellation window. Therefore, as shown in FIG. 6, if the output signal of the repeater is delayed until the feedforward signal 53 appears in front of the feedback cancellation window 61 of the repeater, the feedforward signal 53 is located in front of the feedback cancellation window. can do.

As a method of detecting the feedforward signal, it is sufficient to remove the repeater output and detect the correlation of the signal input to the link antenna, since the feedback signal does not exist if the output signal of the repeater disappears. There are many ways to remove the repeater output, such as switching off the repeater amplifier to zero the gain of the repeater, or zeroing the digital signal output to the D / A converter input. In addition, the method of detecting the feedforward signal may be performed by any other method, of course.

Second Embodiment

 FIG. 7 is a view schematically illustrating a feedforward signal processing method in an oscillation elimination repeater according to a second exemplary embodiment of the present invention.

Unlike the first embodiment described above, the second embodiment shown in FIG. 7 includes detecting a feedforward signal; Storing a feedforward signal location; And dividing / setting the feedback removal window by avoiding the stored feedforward signal position during the division of the feedback removal window so that the feedforward signal is not removed. The division / setting of the feedback elimination window may include a manual division scheme as well as an automatic division scheme according to the prior art.

The manner of detecting the feedforward signal 53 is the same as that described above in the first embodiment. In addition, in the feedback elimination window dividing / setting step, the feedback elimination window is divided into two or more banks 71 and 72 so that the detected feedforward signal 53 as shown in FIG. 7 does not lie within the feedback elimination window of the repeater itself. Only 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. However, the problem may be solved by applying a system delay so that the position of the two signals does not overlap.

Third Embodiment

8 is a diagram schematically illustrating a feedforward signal processing method in an oscillation cancellation repeater according to a third exemplary embodiment of the present invention.

The present embodiment includes the steps of delaying the output signal of the repeater by a predetermined time (S81); Performing the automatic feedback removal window splitting function as in the above-described prior art (S82); And restoring the set repeater delay to its original state (S83).

In the step S81 most significant feed-forward signal it is one to two degrees of another repeater coarse signal because it is a predetermined time (T _c) the time (where T _c is input to the link antenna of the repeater when removing the output of the repeater When the signal is detected may have a magnitude greater than the time detected, but there is a time that can be delayed to the maximum due to the limit of the delay application of the repeater), and the window is automatically divided after the repeater is applied. In the same manner as in the first embodiment with reference to FIG. 6, only the repeater itself feedback signal and the feedback signal between the repeaters except the feedforward signal can be eliminated. However, if the repeater itself delay is set to the same for all repeaters, the feedforward signal received from the other repeater also receives the delayed signal to the maximum, so as in step S83, the repeater self delay set to the maximum is reset as in step S83. It won't work unless you repair it.

In step S82, the feedback removing window is moved to remove both the repeater itself feedback signal and the feedback signal between the repeaters, and the feedback signal is searched and the feedback removing window is divided based on the found feedback signal. The search of the feedback signal is performed by sequentially moving the feedback cancellation window and searching for the feedback signal in units of unit windows within the feedback cancellation window, and the feedback removal window division includes a division bank composed of any number of unit windows. And the same method as previously described.

Even in the case of the above scheme, there is still a problem when the position of the feedforward signal overlaps with the position of the feedback signal.

Fourth Embodiment

9 illustrates a feedforward signal processing method in an oscillation cancellation repeater according to a fourth preferred embodiment of the present invention.

The feedforward signal processing method in the oscillation elimination repeater according to the present embodiment includes: setting a repeater output or a gain to 0 (S91); Measuring an autocorrelation of the repeater wireless input signal (S93); Applying a system delay of the repeater (S95); Re-measuring the autocorrelation to repeat steps S94 and S95 until no feedforward signal is detected, further applying a system delay; And setting the maximum value of the system delay so that no delay above the maximum value is set (S96, S97).

First, in step S91, without further delaying the output signal of the repeater, the search for the feedback signal is started during the time interval of 0 to N * T _{TOT with} the repeater output or gain set to 0 (S92). Step S91 may use a method of zeroing the repeater gain by using a method of switching off the repeater amplifier as described above, or a method of zeroing the digital signal output serving as the D / A converter input, but is not limited thereto. Any method can be used as long as the feedback signal is not introduced to create an environment where only the influence of the feedforward signal on the repeater wireless input can be measured. In this state, since there is no feedback signal, the presence or absence of a feedforward signal can be detected by measuring the autocorrelation coefficient R _FF (n) of the input signal.

Subsequently, it is determined whether the feedforward signal is present by comparing whether the correlation value of the input terminal measured in step S93 becomes a predetermined level (TH _FF ) (S94), and when it is determined that the feedforward signal is input, an additional delay of the repeater ( T _d ) is applied (S95). After the repeater additional delay is applied, the final repeater delay set values are determined by repeatedly detecting the presence of the feedforward signal by re-measurement of autocorrelation (S94, S95, S99).

In the process of adding the relay delay value, a protection procedure may be provided so as not to exceed the maximum values T _{d and max} of the system delay set in step S96. The reason for setting the maximum value (T _{d , max} ) of the system additional delay that can be applied is that the repeater system delay may affect the reverse softer combining performance of the base station. If the repeater system delay is applied larger than the base station combining length, the softer handover performance may be degraded, thereby limiting the maximum delay value. If the repeater system delay exceeds the maximum delay value, the additional delay value should be returned to a value between 0 and T _{d , max} (S97). After the return, there is a problem because the influence of the remaining feedforward signal remains. In this case, an additional function is required to store the position of the feedforward signal so that the window is not divided at the position when the feedback signal removing window is divided in the future. Here, referring back to the feedback signal position search information, which is a later procedure, an exceptional problem may be solved by setting a return delay value between 0 and T _{d and max} so that the remaining feedforward signals do not overlap.

In addition to measuring the correlation of the input terminal of the repeater may include the step of detecting whether the repeater radio input signal is the oscillation level from the beginning (S98). If the repeater radio input signal is already oscillated, the following signal search procedure is meaningless, so set-up and switch off the amplifier to prevent oscillation propagation to secure network stability. Detection of the oscillation level is possible by measuring the autocorrelation [R _FB (n)] of the input signal, typically TH _oscillation > TH _FF .

Delaying the output signal of the repeater by detecting the feedforward signal through the correlation value in the proposed method eliminates the feedforward signal directly located in the feedback cancellation window. Can be.

2. Effect of Feedforward Image Signal

Through 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 is present, the influence of the feedforward signal outside the window may be transformed into an image of the feedforward signal and appear inside the window.

5C is an example illustrating how the feedforward image due to correlation with the feedback signal has an effect when the feedforward signal exists outside the feedback cancellation window. In the above example, a condition in which one feedforward signal is generated by a distance d from the original source signal is illustrated as an example. The feedforward signal may be a multipath of the original base station source signal, or may be a case where the feedforward signal is positioned in front of the window by applying the repeater delay (see 53 in FIG. 6). In addition, the example illustrated in FIG. 5C is a case where three feedback signals are present. When the correlation between the repeater input signals is obtained under the above conditions, as shown in FIG. 5C, the image components (reference numerals 521 ', 521', in addition to the original feedback signals (521, 522, 523) by the feedforward signal 53 are shown. 521 ", 522 ', 522", 523', and 523 "are displayed. Since the feedforward image signals are automatically removed when only the relevant feedback signal is removed, a separate window resource may not be allocated.

In case of automatic window search / split, if the allocated window hardware (or software) resource is allocated to the feedforward image signal because the allocated window size (X _tot ) is smaller than the window size (N * X _tot ) to search, As a result, the feedback signal, which must be removed, may not be removed, which may cause oscillation. Therefore, the processing of the feedforward image signal is very important and the following procedure describes the algorithm that considers it.

3. Sequential Search for Feedback Signal and Window Segmentation Considering Feedforward Image Signal

This section describes an embodiment of a feedback signal sequential search and automatic window segmentation method considering the feedforward image signal.

Fifth Embodiment

FIG. 10 illustrates a process of automatically dividing a feedback cancellation window in an oscillation cancellation repeater according to a fifth exemplary embodiment of the present invention considering the feedforward signal processing as described above. Since the procedure before step S99 of Fig. 10 has already been described above, the automatic search procedure after step S99 will be described in this embodiment.

The automatic feedback removal window splitting procedure may include: setting the repeater gain to a minimum after turning on the output or gain of the repeater (S99); Measuring the correlation R _FB (n) of the signal after removing feedback from the repeater (S100); Determining a resource validity of whether a divided bank of the feedback cancellation window can be allocated to a position where a largest correlation value exists among measured correlations (S101); Re-measurement of the correlation R _FB (n) of the signal after the feedback removing after the division bank repartitioning is applied (S102); Step (S103) of dividing / allocating an effective bank and repeating steps S101 and S102 until the correlation value is below a predetermined level in the search range (S103); Increasing the gain of the repeater by a unit gain (S104); And repeating steps S100 to S104 under the condition that the repeater gain is equal to or lower than a predetermined level P _ref , and setting the window bank and returning to the user Atten before the procedure (S106). . In addition, when the split bank resource is exhausted in step S101 and bank relocation is impossible, verifying whether at least one of the correlation values becomes the oscillation level (S108) and applying the effective division setting before oscillation when the oscillation is detected (S109). can do.

In the step S100, the feedback signal is present, strictly speaking, in the absence of the feedback signal, the delay of the output signal of the repeater so that the feedback removal window is in a position that does not remove the feedforward signal, the self of the signal after the feedback removal Note that the correlation R _FB (n) is measured. In this case, the correlation is a correlation value in a situation in which a feedback signal removal operation is performed by sequentially removing the feedback removal window bank division.

In step S101, it is determined whether the window bank resource remains. If it is determined that the divided banks can be rearranged, in step S102, one of the divided banks of the feedback removing window is allocated to a position where the correlation value measured in the search window is the largest to remove the corresponding signal, and then the correlation is measured again. .

As already described above in FIG. 5C, the feedforward image signal is located on both sides of the associated feedback signal. The average power of the correlation value for the feedforward image signal is always less than 6 dB of the average level of the associated feedback signal, and a condition that is 6 dB apart occurs when the original received signal and the feedforward signal are the same. Therefore, when one bank is allocated to the position where the correlation value R _FB (n) is the largest after feedback removal as in step S102, the window bank is allocated to the position of the feedback signal having the largest power. The feedforward image signal is automatically removed. That is, the effective banks may be sequentially allocated in the order of the signal power only of the feedback signal through the repetition procedure of steps S101 and S102, and resources may be prevented from being allocated to the feedforward image signal.

Meanwhile, in the above-described example, it is determined whether the window bank resource remains in step S101, and it is described that the partition bank is relocated only when the window bank resource remains. However, the window bank resource passes through steps S104 and S105. Even if is not left, if the largest correlation value among the re-measured correlations is larger than the correlation value allocated to the divided banks in the previous step, the step S101 is omitted and the re-measurement of the divided banks allocated in the previous step is performed. It is also possible to relocate to the position where the largest correlation value exists.

The process is repeated until the condition that all correlation values are removed and remain below a certain level (steps S101 to S103). In the present embodiment, the constant level is an example of a TH _{G- 20 dB} condition (ie, a condition in which the feedback signal is removed by 20 dB below the repeater gain after the feedback cancellation) where the EVM (Error Vector Magnitue) is 10% or less. However, it will be apparent to those skilled in the art that the threshold value may be operated to meet each mobile communication standard. For reference, in the case of WCDMA system, the EVM specification is 12.5% and in this case, the condition is limited to TH _{G -18 dB} . If a correlation value that is equal to or greater than a corresponding threshold value among the re-measured correlation values exists in the search position, the remaining bank resources are repeatedly allocated to the position where the largest correlation value among the re-measured correlation values exists.

In addition, when the re-measured correlation values are all lower than a constant level (TH _{G- 20 dB} ), the gain of the repeater itself is increased by unit gain (step S104), and the repeater output is given a predetermined output [ The division bank relocation process is repeated until the output power> min {P _ref , P _shutdown }] (step S105). By increasing the repeater gain and repeating the procedure, the search probability can be increased and the overall operation stability can be secured. This is because the feedback signal to be searched becomes larger as the repeater gain increases.

On the other hand, if it is determined in step S101 that the divided bank resources of the feedback removal window are exhausted and the relocation of the divided banks is not possible, there is a correlation value greater than the oscillation start level (TH _oscillation ) that may generate oscillation among the remaining correlation values. It is judged whether or not (step S108). When there is no correlation value above the oscillation start level (TH _oscillation ), since the possibility of oscillation is small, when the gain of the repeater itself continues to the predetermined output [Output> min {P _ref , P _shutdown }] through step S104. Repeat the split bank relocation process. If a correlation value equal to or higher than the oscillation start level (TH _oscillation ) is detected, the repeater gain of the oscillation level is indicated by using the window partitioning information in the feedback elimination window arrangement before the oscillation stored, and the corresponding window partitioning information is applied. The process ends (steps S109 and S110).

In step S105, when the gain of the repeater itself exceeds a predetermined output [output power> min {P _ref , P _shutdown }], the feedback removal window is divided and set by the arrangement of the window bank last set, and the search for the feedback signal is terminated. (Steps S106 and S107).

According to this embodiment, it is possible to prevent the shortage of window resources that may be generated by the image component of the feedback signal due to the presence of the feedforward signal, and it is possible to efficiently use the resources.

Sixth Embodiment

Fig. 11 shows an automatic splitting procedure in the oscillation eliminating repeater according to the sixth preferred embodiment of the present invention.

Since this embodiment is almost the same as in the above-described fifth embodiment, the following description will focus on the differences.

In this embodiment, the step of measuring the convergence coefficient power P _Coeff (n) by the moving search of the additional feedback cancellation adaptive filter of the repeater (S100 '), the largest value of the measured filter coefficient power P _Coeff (n) is present Allocating the divided banks such that one of the divided banks of the feedback cancellation window is located at a position (S102 '); After allocating / applying the divided banks, the third step is repeated by re-measuring the convergence coefficient power P _Coeff (n) of the feedback _elimination adaptive filter and dividing / allocating the effective banks until all of these values are below a certain level. Performing steps S103 ', S101, S102'; And repeating steps S100 ', S101, S102', S103 ', and S104 by increasing the gain of the repeater by a unit gain until the gain of the repeater is equal to or less than a predetermined level P _ref (S105). It is made, including.

In the fifth embodiment, the feedback signal automatic movement search is performed by using the correlation of the signal after the feedback cancellation. However, in the present embodiment, the movement search procedure by the feedback cancellation adaptive filter is replaced. After convergence of most adaptive filters including feedback cancellation adaptive filters of LMS (Least Mean Square) series, the filter coefficient is a complex value reflecting the feedback signal size in the feedback signal position, and a coefficient is generated at the feedforward image signal position. I never do that. That is, in the above procedure, since the feedforward image signal, which is inevitably derived when mathematically calculating the autocorrelation value, is not generated, there is no need to sequentially allocate a bank for processing the feedforward image signal.

However, the above procedure requires that an adaptive filter for mobile search is added separately from the original feedback cancellation adaptive filter, thereby increasing the complexity of hardware (or software) in the implementation. The feedback signal position search is based on the power of the adaptive filter complex coefficient, and the description thereof is omitted since it is the same as the procedure of the fifth embodiment.

12 is a view schematically showing the configuration of the oscillation removing repeater according to an embodiment of the present invention.

12, the oscillation cancellation repeater according to an exemplary embodiment of the present invention includes a feedback signal search / splitter / rejector 400 and a feedforward signal search / system delay unit 406. The elements are the same as in the conventional case, and each component can also be appropriately adopted to perform the respective methods described in the above-described embodiments, and the detailed description thereof is omitted for convenience.

The feedforward signal search / system delay unit 406 feeds using, for example, the correlation of the radio input signal received via the link antenna 12 after setting the system gain of the repeater to zero. A feedforward signal finder [R _FF (n)] 404 for searching for a forward signal, and a system delay unit 405 for adding the repeater delay as described above according to the time delay of the searched feedforward signal. Is done.

The feedback signal search / splitter / rejector 400 searches for a feedback signal using a correlation value shift search method or an adaptive filter shift search method, the searched feedforward signal, and the feedback signal. Based on the feedback forwarding window partitioner 402 for dividing and setting a feedback cancellation window so that a window is not assigned to the feedforward signal or the image signal of the feedforward signal, and feedback divided by the feedback removal window. And a feedback signal cancellation filter 401 that removes a feedback signal from the received wireless signal based on the cancellation window.

Each component of the feedforward signal search / system delay unit 406 and the feedback signal search / split / rejection unit 400 is for performing each function described in connection with each of the above-described embodiments. It can be easily implemented by software or a combination of hardware and software.

Although preferred embodiments of the present invention have been described in detail above, this is only for explaining the embodiments of the present invention, and it is obvious that various modifications can be made by those skilled in the art. After all, the scope of the present invention will be defined by the claims that follow.

Figure 1 schematically shows the configuration of the oscillation elimination repeater according to the bell technology.

2 illustrates a method of setting / operating a feedback cancellation window in a conventional oscillation cancellation relay.

3 illustrates a case where a feedback loop between repeaters is formed when the oscillation elimination repeater is used.

Figure 4a schematically shows the configuration of the oscillation elimination repeater described in Korean Patent Application No. 2007-007790, Figure 4b is a view showing the operation of the feedback signal searcher of the prior art.

5A and 5B show an example of a signal input through another repeater as an external input signal independent of the gain of the repeater itself receiving the radio signal. FIG. 5C is a diagram schematically illustrating a feedforward image signal generated as a result of measuring a correlation of an input signal when a feedforward signal is present.

FIG. 6 is a diagram schematically illustrating a feedforward signal processing method in an oscillation cancellation repeater according to a first exemplary embodiment of the present invention.

FIG. 7 is a view schematically illustrating a feedforward signal processing method in an oscillation elimination repeater according to a second exemplary embodiment of the present invention.

8 is a diagram schematically illustrating a feedforward signal processing method in an oscillation cancellation repeater according to a third exemplary embodiment of the present invention.

9 illustrates a feedforward signal processing method in the oscillation cancellation repeater according to the fourth preferred embodiment of the present invention.

10 illustrates a feedforward signal processing method in an oscillation elimination repeater according to a fifth exemplary embodiment of the present invention.

11 illustrates a feedforward signal processing method in an oscillation elimination repeater according to a sixth preferred embodiment of the present invention.

12 is a view schematically showing the configuration of the oscillation removing repeater according to an embodiment of the present invention.

Claims (23)

Receiving a radio signal including a feedback signal and a feedforward signal through a link antenna of an oscillation cancellation repeater that removes the feedback signal using the feedback cancellation window; Detecting the feedforward signal; And Resetting the feedback removal window to remove the feedback signal such that the detected feedforward signal is not included in the feedback removal window, and removing and feeding back the feedback signal in the oscillation removal repeater. How to split a window. The method of claim 1, The feedback signal includes a feedback signal between the repeater and its own feedback signal between the repeater and the feed forward and feedback signal search and feedback cancellation window splitting method in the oscillator. The method of claim 1, The detecting of the feedforward signal may include: Setting the output or gain of the repeater to zero; And Moving search and measuring auto-correlation of a wireless input signal received through the link antenna; and a feed forward and feedback signal search and feedback cancellation window segmentation method in an oscillation cancellation repeater. The method of claim 1, Resetting the feedback cancellation window to remove the feedback signal, And delaying the output signal of the repeater such that the feedback cancellation window appears after a detected time of the detected feedforward signal. The method of claim 1, Resetting the feedback cancellation window to remove the feedback signal, And dividing the feedback elimination window by a predetermined number so that the detected feedback signal is not included in the feedback elimination window. The method of claim 1, Resetting the feedback cancellation window to remove the feedback signal, Delaying the output of the repeater for more than a time when a signal input to the link antenna is detected when the output of the repeater is removed; Searching for a feedback signal by moving the feedback cancellation window; Dividing the feedback cancellation window based on the found feedback signal; And And recovering the feedforward and feedback signals and the feedback removal window in the oscillation cancellation repeater. The method of claim 6, The searching of the feedback signal may include searching the feedback signal by sequentially moving the feedback elimination window, and searching for a feed forward and feedback signal in the oscillation eliminating repeater. The method of claim 6, The dividing of the feedback elimination window may include dividing and setting the feedback elimination window in a continuous or discontinuous manner using a division bank including any number of unit windows. Method for splitting forward and feedback signal search and feedback cancellation windows. The method of claim 1, The detecting of the feedforward signal may include: A first step of setting the output or gain of the repeater to zero; Moving searching and measuring an autocorrelation of a wireless input signal received through the link antenna; Applying a further system delay of the repeater; And And re-measuring the autocorrelation to repeat the third and fourth steps until no feedforward signal is detected, further comprising a fifth step of applying a system delay further. Method for splitting forward and feedback signal search and feedback cancellation windows. The method of claim 9, The detecting of the feedforward signal may include: And repeating the fifth step until the maximum value of a predetermined system delay is reached. The method of claim 10, The detecting of the feedforward signal may include: Restoring the additional system delay to a state before the maximum value when the additional system delay caused by the feedforward signal becomes greater than or equal to the maximum value; And And a verification step of checking whether an input signal is an oscillation signal in a state in which the recovered system delay is applied. The method of claim 9, Splitting the feedback elimination window, A method of searching for feed forward and feedback signals and removing feedback from the oscillation elimination repeater, wherein the window bank resource is not allocated to the feed forward image signal. The method of claim 12, Splitting the feedback elimination window, A sixth step of setting the gain of the repeater to a minimum; A seventh step of searching for and measuring the correlation of the signal [R _FB (n)] after removing the feedback of the repeater; An eighth step of allocating the division banks so that one of the division banks of the feedback cancellation window is located at a position where the largest correlation value among the measured correlations exists; A ninth step of repeatedly performing the eighth step by allocating a valid bank until all correlation values are below a predetermined level after re-measuring the correlation [R _FB (n)] after the window division bank allocation. step; And And a tenth step of repeating the seventh to ninth steps by increasing the gain of the repeater by a unit gain until the gain of the repeater is equal to or less than a predetermined level (P _ref ). How to split feedforward and feedback signals in Windows and remove feedback. The method of claim 13, If the divided bank resources to be allocated in the eighth step are exhausted and relocation of the divided banks is not possible, determining whether there is a residual correlation value equal to or greater than the oscillation start level of the repeater; If there is no correlation value above the oscillation start level of the repeater, the gain of the repeater is increased by the unit gain to repeat the seventh and ninth steps, If there is a correlation value equal to or higher than the oscillation start level of the repeater, the gain of the repeater immediately before the oscillation level is indicated by using the window partition information in the feedback elimination window arrangement before the oscillation, and the feedback signal is applied by applying the window partition information. Method for searching for feed forward and feedback signals and removing feedback from the oscillation elimination repeater, characterized in that for removing. The method of claim 13, When the divided bank resource to be allocated in the eighth step is exhausted and the largest correlation value among the correlations remeasured in the ninth step is larger than the correlation value to which the divided bank is allocated in the eighth step, the eighth step is performed. And relocating the divided bank allocated in the step to a position where the largest correlation value among the correlations measured in the ninth step exists. The method of claim 12, Splitting the feedback elimination window, An eleventh step of setting a minimum gain of the repeater; A twelfth step of moving search / measurement of coefficient power by the feedback cancellation adaptive filter of the repeater; A thirteenth step of allocating the division banks so that 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; A fourteenth step of repeating the thirteenth step after allocating / applying the divided banks, dividing / allocating the valid banks until all are below a predetermined level after re-measurement of adaptive filter coefficient power after removing feedback; And And a fifteenth step of repeating the twelfth to fourteenth 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 predetermined level (P _ref ). How to split feedforward and feedback signals in Windows and remove feedback. The method of claim 16, If the divided bank resources to be allocated in the thirteenth step are exhausted and relocation of the divided banks is not possible, determining whether there is a residual count power value equal to or greater than the oscillation start level of the repeater; If there is no coefficient power value greater than the oscillation start level of the repeater, the steps 12 and 14 are repeated by increasing the gain of the repeater by unit gain, and the coefficient power value greater than the oscillation start level of the repeater is present. In the case of the feedback elimination window before oscillation stored, the gain of the repeater immediately before the oscillation level is indicated using the window segmentation information, and the feedback signal is removed by applying the corresponding window segmentation information. And splitting the feedback signal search and feedback cancellation window. The method according to claim 13 or 16, The method of searching for feed forward and feedback signals and performing a feedback cancellation window splitting in the oscillation removing repeater, wherein the feedback cancellation window searching and splitting is performed in real time. The method according to claim 13 or 16, The feed forward and feedback signal search and feedback removal window segmentation method of the oscillation removal repeater, characterized in that the search and partitioning of the feedback cancellation window is performed at the initial installation or at the user's request. The method according to claim 13 or 16, The feed forward and feedback signal search and feedback cancellation window partitioning method of the oscillation cancellation repeater, characterized in that the forward and reverse separately performing the feedback cancellation window search and splitting. The method according to claim 13 or 16, The feed forward and feedback signal searching and feedback removing window splitting method of the oscillation removing repeater, characterized in that the searching and splitting of the feedback removing window is performed in the forward or reverse direction only and the splitting information is set to the same in the reverse or forward direction. In the oscillation elimination repeater which removes a feedback signal using a feedback elimination window, A link antenna for receiving a radio signal comprising a feedback signal and a feedforward signal; A feedforward signal searcher for searching for a feedforward signal among wireless signals received by the link antenna; And And a system delay unit for adding a system delay of the oscillation elimination repeater such that the detected feedforward signal is not included in the feedback elimination window. The method of claim 22, A feedback signal searcher searching for a feedback signal among wireless signals received by the link antenna; A feedback elimination window dividing unit for dividing and setting a feedback elimination window so that no window is allocated to the feed forward signal or the image signal of the feed forward signal based on the found feed forward signal and the feedback signal; And And a feedback signal cancellation filter for removing a feedback signal from the received wireless signal based on the feedback cancellation window divided by the feedback cancellation window.

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