KR20210019954A - Repeater and operating method thereof - Google Patents

Abstract

According to an embodiment of the present invention, an operation method of a repeater includes the steps of: selecting some of adaptive filter coefficients among a plurality of adaptive filter coefficients of an adaptive filter used for interference cancellation, based on the size of a coefficient; generating a predicted interference signal using the selected adaptive filter coefficients; and generating an interference-canceled communication signal from a received signal using the generated predicted interference signal. According to the present invention, it is possible to minimize the amount of computation in the adaptive filter without significant degradation of interference cancellation performance.

Description

Repeater and its operation method {REPEATER AND OPERATING METHOD THEREOF}

The present invention relates to a repeater and a method of operating the same, and more particularly, to a repeater capable of selecting and using some of the adaptive filter coefficients of the adaptive filter based on the size of the coefficient, and a method of operating the same.

The present invention is a project for the development of a cell coverage extension device for high-power, high-efficiency, low-latency, dual-mode (WiBro, TD-LTE) cell coverage of the same frequency retransmission method using interference signal cancellation technology in the "TICN wireless network" of the Civil-Military Cooperation Agency It is an invention according to the result of performing ")".

In a repeater that receives RF (Radio Frequency) signals and amplifies and transmits the received RF signals, if sufficient separation distance between the donor antenna and the service antenna is not secured, part of the transmitted signal from one antenna flows into the other antenna. Receiving performance may be deteriorated or oscillation may occur due to the feedback signal.

An interference cancellation repeater, also called ICS (Interference Cancellation System) or OCR (On-Channel Repeater), can transmit by removing a feedback signal component included in a received signal using a digital signal processing technology.

An object of the present invention is to provide a repeater capable of selecting and using some of the adaptive filter coefficients of the adaptive filter based on the size of the coefficients, and a method of operating the same.

The operation method of a repeater according to an embodiment of the present invention comprises the steps of selecting some of the adaptive filter coefficients of the adaptive filter used for interference cancellation based on the size of the coefficients, and prediction using the selected adaptive filter coefficients. It may include generating an interference signal and generating an interference-cancelled communication signal from the received signal by using the generated predictive interference signal.

According to an embodiment, the adaptive filter may be a finite impulse response (FIR) filter.

According to an embodiment, in the step of selecting the partial adaptive filter coefficients based on the size of the coefficients, the partial adaptive filter coefficients among the adaptive filter coefficients may be selected based on the magnitude of the absolute value of the coefficient.

According to an embodiment, the method of operating the repeater further includes sorting the adaptive filter coefficients according to the absolute value of the coefficients, and selecting some of the adaptive filter coefficients based on the size of the coefficients, Among the sorted adaptive filter coefficients, some of the adaptive filter coefficients having a higher absolute value may be selected according to the sorted order.

According to an embodiment, the step of selecting some of the adaptive filter coefficients based on the size of the coefficient includes selecting K adaptive filter coefficients from among N adaptive filter coefficients, wherein N is a natural number of 2 or more, and the K may be a natural number smaller than N.

According to an embodiment, the ratio of N and K may be a preset value.

According to an embodiment, the ratio of N and K may be set flexibly.

According to an embodiment, the method of operating the repeater further comprises searching for a point in which an absolute difference between adjacent coefficients is greater than a reference value when the adaptive filter coefficients are arranged in the order of the absolute value of the coefficients, and the partial The selecting of the adaptive filter coefficients based on the size of the coefficient may include selecting some of the adaptive filter coefficients having an upper absolute value according to the order of the absolute value of the coefficient based on the searched point.

According to an embodiment, the ratio of N and K may be set according to Quality of Service (QoS).

The repeater according to an embodiment of the present invention selects and outputs some of the adaptive filter coefficients of the adaptive filter used for interference cancellation based on the size of the coefficient, and a predictive interference signal using the selected adaptive filter coefficients. It may include an adaptive filter for generating a and a subtractor for generating a communication signal from which interference is removed from the received signal by using the generated prediction interference signal.

According to an embodiment, the controller arranges the adaptive filter coefficients according to the magnitude of the absolute value of the coefficients, and among the arranged adaptive filter coefficients, the part having an upper absolute value size according to the order of the absolute value of the coefficients The adaptive filter coefficients of can be selected.

According to an embodiment, the controller selects K adaptive filter coefficients from among N adaptive filter coefficients, where N is a natural number equal to or greater than 2, and K may be a natural number smaller than N.

According to an embodiment, the ratio of N and K may be set flexibly.

According to an embodiment, when the adaptive filter coefficients are arranged in the order of the magnitude of the absolute values of the coefficients, the controller searches for a point where the difference between the absolute values between adjacent coefficients is greater than the reference value, and based on the retrieved points, the sorted order According to, some of the adaptive filter coefficients having an upper absolute value may be selected.

According to an embodiment, the ratio of N and K may be set according to Quality of Service (QoS).

A method and an apparatus according to an embodiment of the present invention select and use some of the adaptive filter coefficients of the adaptive filter based on the size of the coefficients, so that interference removal performance is not significantly degraded. There is an effect that can minimize the amount of computation.

In addition, the method and apparatus according to an embodiment of the present invention has an advantage in that the method according to the embodiment of the present invention can be applied while using the adaptive algorithm used in the existing adaptive filter as it is.

Brief description of each drawing is provided in order to more fully understand the drawings cited in the detailed description of the present invention.
1 is a conceptual diagram of a communication system according to an embodiment of the present invention.
FIG. 2 is a block diagram of the repeater shown in FIG. 1 according to an embodiment.
3 is a flowchart of a method of operating a repeater according to an embodiment of the present invention.
4 is a graph of transient response characteristics according to a selection ratio of adaptive filter coefficients.
5 is a graph of a fading feedback response characteristic according to a selection ratio of adaptive filter coefficients.
6 is a graph showing a relationship between a feedback gain and a normalized mean square error (NMSE) according to a selection ratio of an adaptive filter coefficient.

The technical idea of the present invention is that various changes may be made and various embodiments may be provided, and specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the technical idea of the present invention to a specific embodiment, it should be understood to include all changes, equivalents, and substitutes included in the scope of the technical idea of the present invention.

In describing the technical idea of the present invention, when it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted. In addition, numbers (eg, first, second, etc.) used in the description of the present specification are merely identification symbols for distinguishing one component from other components.

In addition, in the present specification, when one component is referred to as "connected" or "connected" to another component, the one component may be directly connected or directly connected to the other component, but specially It should be understood that as long as there is no opposing substrate, it may be connected or may be connected via another component in the middle.

In addition, terms such as "~ unit", "~ group", "~ character", and "~ module" described in the present specification mean a unit that processes at least one function or operation, which is a processor or microcomputer. Processor (Micro Processer), Micro Controller, CPU (Central Processing Unit), GPU (Graphics Processing Unit), APU (Accelerate Processor Unit), DSP (Drive Signal Processor), ASIC (Application Specific Integrated Circuit), FPGA It may be implemented in hardware or software such as (Field Programmable Gate Array), or a combination of hardware and software, and may be implemented in a form combined with a memory that stores data necessary for processing at least one function or operation. .

In addition, it is intended to clarify that the division of the constituent parts in the present specification is only divided by the main function that each constituent part is responsible for. That is, two or more constituent parts to be described below may be combined into one constituent part, or one constituent part may be divided into two or more according to more subdivided functions. In addition, each of the constituent units to be described below may additionally perform some or all of the functions of other constituent units in addition to its own main function, and some of the main functions of each constituent unit are different. It goes without saying that it may be performed exclusively by.

1 is a conceptual diagram of a communication system according to an embodiment of the present invention.

Referring to FIG. 1, a communication system 10 according to an embodiment of the present invention may include a base station 100, a wireless communication terminal 200, and a repeater 300.

The wireless communication terminal 200 may mean a device capable of performing wireless communication according to various mobile communication standards, and its shape can be variously modified.

The repeater 300 may relay communication between the base station 100 and the wireless communication terminal 200.

According to an embodiment, the repeater 300 is a 2G mobile communication network such as global system for mobile communication (GSM) or code division multiple access (CDMA), a 3G mobile communication network such as wideband code division multiple access (WCDMA) or CDMA2000, HSDPA. 3.5G mobile communication network such as (high speed downlink packet access) or high speed uplink packet access (HSUPA), 4G mobile communication network such as long term evolution (LTE) or LTE-Advanced, and 5G mobile communication network (Non-Stand Alone) Alternatively, communication signals may be relayed in a communication network composed of SA (Stand Alone)), a 6G mobile communication network, or a combination thereof.

The repeater 300 receives a communication signal (eg, a base station signal) transmitted from the base station 100 through a first antenna ANT1, and receives the received communication signal (eg, a base station signal) through a second antenna (ANT2). Through the wireless communication terminal 200 can be relayed.

Depending on the embodiment, the communication signal may be a wireless communication signal (eg, a radio frequency (RF) signal).

The first antenna ANT1 may be referred to as a donor antenna, and the second antenna ANT2 may be referred to as a service antenna or a coverage antenna, but is not limited thereto. .

Depending on the embodiment, the repeater 300 may be implemented as an Interference Cancellation System (ICS) repeater.

In FIG. 1, for convenience of explanation, the repeater 300 is shown to relay communication between one base station 100 and one wireless communication terminal 200. However, the repeater 300 includes a plurality of base stations and a plurality of radios. Communication between communication terminals can also be relayed. According to another embodiment, the repeater 300 may relay communication between the base station 100 and another repeater (not shown).

A detailed structure and operation of the repeater 300 will be described in detail with reference to FIG. 2.

FIG. 2 is a block diagram of the repeater shown in FIG. 1 according to an embodiment.

1 and 2, the repeater 300 includes a first antenna (ANT1), a second antenna (ANT2), a prefilter (310), an interference cancellation part (320), and a post filter ( It may include a postfilter, 330, and a delay 340.

In FIG. 2, for convenience of explanation, a configuration that operates in a process in which a wireless communication signal in one direction (eg, downlink) is relayed is mainly shown, but the repeater 300 has a radio in the opposite direction (eg, uplink). A configuration that operates in the process of relaying a communication signal may be additionally included.

The first antenna ANT1 is a wireless communication signal (Si[n]) transmitted from the base station 100 and a feedback signal (i.e., an interference signal) output from the second antenna ANT2 and received through a feedback channel. Alternatively, a feedback signal, Sfb[n]) may be received.

The repeater 300 may further include an analog digital converter (ADC) for converting the received wireless communication signal and the feedback signal from analog to digital.

In FIG. 2, for convenience of explanation, the ADC process is omitted and the first antenna ANT1 directly receives the digital signals Si[n] and Sfb[n], but the digital signals Si[n] ], Sfb[n]) may each represent a digitally converted RF signal transmitted from the base station 100 and an RF signal transmitted from the second antenna ANT2.

In the present specification, “digital signal” may broadly mean a digitized signal regardless of its shape, and may mean a concept including a complex baseband digital signal.

The wireless communication signal (Si[n]) and the feedback signal (Sfb[n]) are combined to generate a received signal (Sx[n]), and the generated received signal (Sx[n]) is transferred to the prefilter 310. Can be entered.

The prefilter 310 is an equivalent circuit showing the characteristics and delays of all filters until the received signal Sx[n] input through the first antenna ANT1 of the repeater 300 is transmitted to the subtractor 326 Can mean

The received signal d[n] that has passed through the prefilter 310 may be input to the interference cancellation part 320.

The interference cancellation part 320 may include a controller 322, an adaptive filter 324, and a subtractor 326.

The controller 322 may generate and output adaptive filter coefficients Wn to be used in the adaptive filter 324 by using the interference-cancelled communication signal e[n] and the delayed output signal x[n]. have.

According to an embodiment, the controller 322 uses the interference canceled communication signal e[n] and the delayed output signal x[n] to calculate optimal adaptive filter coefficients Wn for minimizing interference. You can create and print it.

According to an embodiment, the adaptive filter coefficients Wn may be formed in the form of a coefficient vector.

The controller 322 selects some of the adaptive filter coefficients from among the adaptive filter coefficients used in the adaptive filter 324 based on the size of the coefficient (eg, the magnitude of the absolute value), and only the selected adaptive filter coefficients ( 324).

According to an embodiment, the controller 322 sorts the adaptive filter coefficients according to the magnitude of the absolute value of the coefficients, and selects some of the adaptive filter coefficients having the upper absolute value according to the sorted order among the arranged adaptive filter coefficients. I can.

를 절대 값 크기에 따라 내림차순으로 정렬하면 다음의 (수식 1)과 같이 표현될 수 있다.For example, assuming that the number of taps of the adaptive filter 324 is N (the N is a natural number of 2 or more), the adaptive filter coefficient

Sorting in descending order according to the absolute value can be expressed as the following (Equation 1).

(Equation 1)

The controller 322 may divide the coefficients arranged in (Equation 1) above into two sets P and R according to the following (Equation 2).

(Equation 2)

의 절대 값이 상위의 K개(상기 K는 N보다 작은 자연수) 안에 속하면 P집합에 포함시키고, 그렇지 않으면 R집합에 포함시킬 수 있다.The controller 322 is the filter coefficient in (Equation 2) above.

If the absolute value of is in the upper K number (the K is a natural number less than N), it is included in the P set, otherwise it can be included in the R set.

The controller 322 may select K filter coefficients included in the P set from among a plurality of filter coefficients, and transfer the selected filter coefficients to the adaptive filter 324.

According to an embodiment, the ratio of N and K may be a preset value.

According to another embodiment, the ratio of N and K may be set flexibly.

According to another embodiment, when the adaptive filter coefficients are arranged in the order of absolute value as in (Equation 1), the controller 322 searches for a point where the absolute difference between adjacent coefficients is greater than the reference value, and based on the searched point. Some of the adaptive filter coefficients can be selected.

과

의 절대값 차이와 적응 필터 계수

과

의 절대값 차이는 기준값 이하였으나, 적응 필터 계수

과

의 절대값 차이는 기준값 이상인 경우에, 컨트롤러(322)는 적응 필터 계수

과

의 사이 지점을 검색하고, 검색된 지점을 기준으로 계수의 절대값 크기의 순서에 따라 상위의 절대값 크기를 가지는

,

,

은 P집합으로 구분하여 선택하고,

,

는 R집합으로 구분하여 선택에서 배제시킬 수 있다. 실시 예에 따라, 상기 기준값은, 전체 적응 필터 계수들의 인접한 계수 간의 절대값 차이의 평균값에 기초하여 설정될 수도 있다.For example, there are a total of 5 adaptive filter coefficients (N=5) and adaptive filter coefficients

and

Absolute value difference and adaptive filter coefficient of

and

The absolute value difference of is less than or equal to the reference value, but the adaptive filter coefficient

and

When the absolute value difference of is greater than or equal to the reference value, the controller 322

and

Searches for a point between and has the upper absolute value according to the order of the absolute value size of the coefficient based on the searched point.

,

,

Is selected by dividing it into P set,

,

Can be excluded from selection by separating them into R sets. According to an embodiment, the reference value may be set based on an average value of an absolute difference between adjacent coefficients of all adaptive filter coefficients.

According to another embodiment, the ratio of N and K may be set according to QoS (Quality of Service).

For example, if the criterion of interference cancellation performance allowed by QoS is relatively high, the ratio of K to N (K/N) is set relatively high, and when the standard of interference cancellation performance allowed by QoS is relatively low, The ratio of K to N (K/N) can be set relatively low.

For example, if the standard of signal delay allowed by QoS is relatively high, the ratio of K to N (K/N) is set relatively low, and if the standard of signal delay allowed by QoS is relatively low, The ratio of K to (K/N) can be set relatively high.

For example, the ratio of N and K may be set in consideration of the standard of interference cancellation performance allowed in QoS and the standard of allowed signal delay.

The adaptive filter 324 may generate a predictive interference signal y[n] using the adaptive filter coefficients Wn selected and delivered by the controller 322 and the delayed output signal x[n]. have.

According to an embodiment, the adaptive filter 324 may be implemented as a digital filter or an analog filter using an adaptive algorithm.

According to an embodiment, the adaptive filter may be implemented as a Finite Impulse Response (FIR) filter.

The subtractor 326 subtracts the predicted interference signal y[n] output from the adaptive filter 360 from the received signal d[n] that has passed through the prefilter 310, and the communication signal e[ n]) can be displayed.

According to an embodiment, the controller 322, the adaptive filter 324, and the subtractor 326 may be implemented with one processor 320. For example, the processor 320 may be implemented as a type of processor such as Application Specific Integrated Circuits (ASIC) or Field Programmable Gate Array (FPGA).

The post filter 330 may refer to an equivalent circuit showing characteristics and delays of all filters until the communication signal output from the subtracter 326 is transmitted to the second antenna ANT2.

The output signal So[n] output from the post filter 330 may be transmitted to the wireless communication terminal 200 through the second antenna ANT2.

The output signal So[n] output from the post filter 330 may be delayed through the delay 340 and output as a delayed output signal x[n]. The delayed output signal x[n] output from the delay 340 may be input to the controller 322 and the adaptive filter 324.

3 is a flowchart of a method of operating a repeater according to an embodiment of the present invention.

1 to 3, the repeater 300 may select some of the adaptive filter coefficients of the adaptive filter 324 based on the size of the coefficient (eg, absolute value size) (S310). .

According to an embodiment, the repeater 300 may select some of the adaptive filter coefficients according to a preset ratio among the plurality of adaptive filter coefficients.

According to another embodiment, the repeater 300 may select some of the adaptive filter coefficients according to a flexibly set ratio among the plurality of adaptive filter coefficients.

According to another embodiment, when the adaptive filter coefficients are arranged in the order of absolute value, the repeater 300 searches for a point where the absolute difference between adjacent coefficients is greater than the reference value, and some adaptive filter coefficients based on the searched point You can choose.

According to another embodiment, the repeater 300 may select some of the adaptive filter coefficients according to a ratio set based on quality of service (QoS) among a plurality of adaptive filter coefficients.

The repeater 300 may generate a predictive interference signal using the adaptive filter coefficients selected in step S310 (S320).

According to an embodiment, the adaptive filter 326 included in the repeater 300 may generate a prediction interference signal using only the adaptive filter coefficients selected in step S310, not all of the adaptive filter coefficients.

The repeater 300 may generate a communication signal from which interference is removed from the received signal by using the predicted interference signal generated in step S320 (S330).

According to an embodiment, the subtractor 326 included in the repeater 300 subtracts the predicted interference signal y[n] from the received signal d[n] that has passed the prefilter 310, thereby eliminating the interference. A signal e[n] can be generated.

4 is a graph of transient response characteristics according to a selection ratio of adaptive filter coefficients.

Referring to FIG. 4, the graph of FIG. 4 shows a process from the initial state of the repeater 300 to the normal operation state when the feedback signal Sfb[n] is 10 dB greater than the wireless communication signal Si[n]. Represents.

While returning from the oscillation occurring in the initial state, the NMSE decreases. In particular, when K/N is 75%, it can be seen that performance deterioration hardly occurs due to the transient response characteristics compared to when K/N is 100%. .

In addition, even when the K/N is 50% or 25%, there is some deterioration in performance due to the transient response characteristics, but it can be confirmed that the K/N ratio level that can be set is within the allowable range in the communication system.

5 is a graph of fading feedback response characteristics according to a selection ratio of adaptive filter coefficients.

Referring to FIG. 5, the graph of FIG. 5 is a graph showing response characteristics to a fading feedback signal.

In the graph of FIG. 5, the solid line represents the change in feedback gain due to fading, and it is assumed that the step size (μ) in the NLMS (Normalized Least Mean Square) algorithm is set to 0.01.

In the section where the feedback gain (FB gain) is 5dB or less, it can be seen that stable interference cancellation is achieved even when the K/N is 50%.

In addition, even when the K/N is 25%, there is a slight deterioration in performance due to the feedback gain characteristics due to fading, but it can be confirmed that the K/N ratio level can be set if it is an allowable range in the communication system.

6 is a graph showing a relationship between a feedback gain and a normalized mean square error (NMSE) according to a selection ratio of an adaptive filter coefficient.

Referring to FIG. 6, the graph of FIG. 6 shows the relationship of NMSE according to the feedback gain (FB Gain) when there is one feedback path.

NMSE can be represented by the following (Equation 3).

In (Equation 3) above, A is the amplitude of the feedback signal, R is the set of unselected adaptive filter coefficients, α is the proportional constant according to the type of adaptive algorithm, μ is the convergence constant, and N is the number of taps of the adaptive filter.

It can be seen that the NMSE is proportional to the sum of squares of unselected adaptive filter coefficients according to (Equation 3), which can also be confirmed by the graph of FIG. 6.

When K/N is set to 75%, there is little deterioration in NMSE characteristics overall compared to when K/N is 100%, and when FB Gain is less than 2dB, even if K/N is set to 25% It can be seen that the deterioration of NMSE characteristics is not significant.

Above, although the present invention has been described in detail with reference to a preferred embodiment, the present invention is not limited to the above embodiment, and various modifications and changes by those of ordinary skill in the art within the spirit and scope of the present invention This is possible.

10: communication system
100: base station
200: wireless communication terminal
300: repeater

Claims (15)

Selecting some of the adaptive filter coefficients of the adaptive filter used for interference cancellation based on the size of the coefficient;
Generating a predictive interference signal using the selected adaptive filter coefficients; And
And generating a communication signal from which interference is removed from the received signal by using the generated predictive interference signal.
The method of claim 1,
The adaptive filter,
FIR (Finite Impulse Response) filter, how the repeater operates.
The method of claim 1,
Selecting some of the adaptive filter coefficients based on the size of the coefficients,
The method of operating a repeater, wherein some of the adaptive filter coefficients are selected from among the adaptive filter coefficients based on a magnitude of an absolute value of the coefficient.
The method of claim 3,
The operation method of the repeater,
Sorting the adaptive filter coefficients according to the absolute value of the coefficients,
Selecting some of the adaptive filter coefficients based on the size of the coefficients,
The method of operating a repeater, wherein among the sorted adaptive filter coefficients, some of the adaptive filter coefficients having a higher absolute value are selected according to the sorted order.
The method of claim 4,
Selecting some of the adaptive filter coefficients based on the size of the coefficients,
Among the N adaptive filter coefficients, K adaptive filter coefficients are selected,
Wherein N is a natural number greater than or equal to 2, and K is a natural number less than N, the method of operating a repeater.
The method of claim 5,
The ratio of the N and K is a preset value, the operation method of the repeater.
The method of claim 5,
The ratio of the N and K is set flexibly, the operation method of the repeater.
The method of claim 7,
The operation method of the repeater,
When the adaptive filter coefficients are arranged in the order of the absolute value of the coefficients, the step of searching for a point in which an absolute difference between adjacent coefficients is greater than a reference value,
Selecting some of the adaptive filter coefficients based on the size of the coefficients,
The method of operating a repeater, wherein the partial adaptive filter coefficients having an upper absolute value size are selected according to the order of the absolute value size of the coefficients based on the searched point.
The method of claim 5,
The ratio of N and K is set according to QoS (Quality of Service).
A controller for selecting and outputting some of the adaptive filter coefficients of the adaptive filter used for interference cancellation based on the size of the coefficient;
An adaptive filter that generates a predictive interference signal using the selected adaptive filter coefficients; And
A repeater comprising a subtractor for generating an interference-cancelled communication signal from a received signal by using the generated predictive interference signal.
The method of claim 10,
The controller,
A repeater that sorts the adaptive filter coefficients according to the magnitude of the absolute value of the coefficient, and selects some of the adaptive filter coefficients having an upper absolute value according to the order of the magnitude of the absolute value of the coefficients among the arranged adaptive filter coefficients .
The method of claim 11,
The controller,
Among the N adaptive filter coefficients, K adaptive filter coefficients are selected,
The N is a natural number of 2 or more, and K is a natural number less than N, a repeater.
The method of claim 12,
The ratio of the N and K is set fluidly, the repeater.
The method of claim 13,
The controller,
When the adaptive filter coefficients are sorted in the order of the absolute value of the coefficients, a point where the absolute difference between adjacent coefficients is greater than the reference value is searched, and based on the searched point, having the upper absolute value size according to the sorted order. A repeater for selecting the some of the adaptive filter coefficients.
The method of claim 13,
The ratio of N and K is set according to QoS (Quality of Service).

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