KR20190058183A - Automatic gain control apparatus, method and terminal including the same in internet of things - Google Patents

Abstract

Disclosed are an apparatus and a method for automatic gain control of IoT, and a terminal including the apparatus for automatic gain control. According to the present invention, the terminal comprises: a front-end module for adjusting a reception signal using a gain and converting the reception signal into a baseband signal which is a digital signal; an average reception power measurement unit for estimating average power for the baseband signal in a frequency domain; and an automatic gain control unit for determining the gain using the estimated average power and outputting the gain to the front-end module.

Description

TECHNICAL FIELD [0001] The present invention relates to an automatic gain control apparatus and method for an object Internet, and a terminal including the automatic gain control apparatus and method.

The present invention relates to an apparatus and method for automatic gain control of the Internet of objects, and a terminal including the same.

There is a wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM) transmission, which provides wide area Internet of Things (IoT) services at low power and cost. For example, NB-IoT (Narrow Band IoT) is a wireless communication system for IOT. The NB-IoT is a system for operating a signal for providing the object Internet service using one or more of the resource blocks (RB) in the frequency band used in the existing LTE (Long-Term Evolution) system.

Automatic gain control (AGC) is one of the essential technologies for implementing IoT terminals that cover a wide area with low power and low cost. The automatic gain control is a technique for causing the intensity of a digital signal to fall within a desired range in the process of converting an analog signal input to the terminal into a digital signal. If AGC technology is not operated properly and a too large digital signal is input, a clipping phenomenon occurs, resulting in overload quantization noise and information loss. If too small a digital signal is input, a granular quantization error occurs and information loss occurs. It is necessary to develop an AGC algorithm that operates efficiently at low power while reducing the quantization error.

On the other hand, in order to perform efficient AGC, average power measurement of the received signal is required. Although the determination of the interval for measuring the average power varies according to the wireless communication system, an important requirement for the interval determination must meet the long-term fading condition. If the AGC is performed using the average power measured in the short-term fading condition, an artificial change due to the AGC occurs. This artificial change affects the result of the channel estimation on the received signal, which causes degradation of the received demodulation performance. Therefore, it is important to set the average power measurement interval to meet the long term fading condition.

An object of the present invention is to provide an automatic gain control apparatus and method for reducing a quantization error at a low power and a low cost in an object Internet.

Another object to be solved by the present invention is to provide an automatic gain control apparatus and method using an average power measurement conforming to a long-term fading condition on the object Internet.

According to an embodiment of the present invention, a terminal for processing a received signal on the object Internet is provided. The terminal includes a front-end module that adjusts the received signal using a gain and converts the received signal into a baseband signal as a digital signal, an average received power measurement unit that estimates an average power of the baseband signal in a frequency domain, And an automatic gain controller for determining the gain using the average power and outputting the gain to the front end module.

The automatic gain control unit may calculate a new gain using a first value that is a value obtained by dividing a current gain among the gains by the average power.

The automatic gain control unit may calculate a second value that is a value obtained by dividing the first value by a predetermined margin, and the second value may be the new gain.

The gain and the average power may be dB scales and the automatic gain control unit may calculate the new gain using a first value that is a value obtained by subtracting the average power of the dB scale from the current one of the gains .

The automatic gain control unit may calculate a second value by subtracting a margin of a predetermined dB scale from the first value, and the second value may be the new gain.

The average received power measurement unit may estimate the average power through an Infinite Impulse Response filter.

The average reception power measurer may estimate the average power using the baseband signal corresponding to a narrowband primary synchronization signal among the reception signals.

The average reception power measurer may estimate the average power using the baseband signal corresponding to a narrowband reference signal among the reception signals.

The period in which the average received power measurement unit measures the average power and transmits the measured average power to the automatic gain control unit may satisfy a long-term fading condition.

According to another embodiment of the present invention, there is provided an automatic gain control apparatus for adjusting a gain, which is a factor for adjusting a level of a signal input from an object Internet to an analog-to-digital converter. The automatic gain control device includes an average received power measurement unit for estimating an average power of an output signal of the analog-to-digital converter in a frequency domain, and a gain calculation unit for calculating a new gain using the current gain and the average power And may include an automatic gain control section.

The automatic gain control unit may calculate the new gain using a first value that is a value obtained by dividing the current gain by the average power.

The automatic gain control unit may calculate the second value by dividing the first value by a preset margin and convert the second value to a dB scale, and the second value of the dB scale may be the new gain have.

The gain and the average power may be dB scales and the automatic gain control unit may calculate the new gain using a first value that is a value obtained by subtracting the average power of the dB scale from the gain of the dB scale.

The automatic gain control unit may calculate a second value by subtracting a margin of a predetermined dB scale from the first value, and the second value may be the new gain.

According to another embodiment of the present invention, a method is provided for a terminal to perform automatic gain control in an Internet of things. The method includes the steps of generating a first signal by applying a current gain to a received signal, converting the first signal to a digital signal, estimating an average power in a frequency domain using the digital signal, Calculating the new gain using the current gain and the average power, and applying the new gain to the received signal.

The calculating step may include calculating a first value that is a value obtained by dividing the current gain by the average power, and calculating the new gain using the first value.

The calculating step may further include calculating a second value that is a value obtained by dividing the first value by a predetermined margin.

Wherein the current gain and the average power may be a dB scale and the calculating step includes calculating a first value that is a value obtained by subtracting the average power of the dB scale from the current dB scale gain, And calculating the new gain using the new gain.

The calculating may further include calculating a second value, which is a value obtained by subtracting a margin of a predetermined dB scale from the first value, and the second value may be the new gain.

The estimating step may include estimating the average power through an Infinite Impulse Response filter.

According to an embodiment of the present invention, the average received power can be measured such that the automatic gain control device meets long-term fading conditions.

According to the embodiment of the present invention, the automatic gain control device obtains a gain through a simple mathematical operation on the average received power measured without estimating a separate reference power, thereby achieving a low power and low cost automatic gain control Can be performed.

1 is a block diagram illustrating a terminal of the Internet of objects according to an embodiment of the present invention.
2 is a diagram illustrating an NB-IoT downlink frame structure according to an embodiment of the present invention.
3 is a block diagram illustrating an automatic gain controller according to a first embodiment of the present invention.
4 is a block diagram illustrating an automatic gain control unit 220b according to a second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, a terminal is referred to as a mobile terminal (MT), a mobile station (MS), an advanced mobile station (AMS), a high reliability mobile station ), A subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE) AMS, HR-MS, SS, PSS, AT, UE, and the like.

Also, a base station (BS) is an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B, eNodeB), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) BS, ABS, Node B, eNodeB, AP, RAS, BTS, MMR-BS, RS, and so on) , HR-RS, and the like.

Hereinafter, an apparatus and method for controlling automatic gain control in the Internet according to an embodiment of the present invention and a terminal including the same will be described with reference to the drawings. Hereinafter, the AGC based on the NB-IoT system will be described for convenience of explanation, but it can be applied to other systems.

In an Internet system, an automatic gain control (AGC) device requires the following requirements. The automatic gain control device needs to measure the received power using the signal received from the antenna and measure the received power of the reference signal received from the antenna. The automatic gain control device needs to adjust the analog gain of the received signal and needs to determine the gain of the AGC that can achieve low power. And the average received power used in automatic gain control (AGC) devices needs to be measured under long-term fading conditions.

1 is a block diagram illustrating a terminal 1000 of the Internet according to an embodiment of the present invention.

As shown in FIG. 1, a terminal 1000 according to an embodiment of the present invention includes a front end module 100 and an automatic gain control device 200.

The front-end module 100 includes a mixer 110, a variable gain amplifier (VGA) 120, and an analog-to-digital converter (ADC)

The mixer 110 multiplies a signal received from the antenna by a carrier frequency signal to convert the signal into a downlink signal. The variable gain amplifier 120 adjusts the signal level by multiplying the signal output from the mixer 110 by a gain. The analog-to-digital converter 130 converts the analog output signal of the variable gain amplifier 120 into a digital signal. Here, the signal output from the analog-to-digital converter 130 is a baseband digital signal.

The automatic gain control apparatus 200 includes an average received power measurement unit 210 and an automatic gain control unit 220.

The average reception power measurer 210 estimates NRSSI (Narrowband Received Signal Strength Indicator), which is the average reception power in the frequency domain, using the baseband digital signal output from the analog-to-digital converter 130. Such an NRSSI will be referred to as a 'Baseband (BB) NRSS' hereinafter. The estimated BB NRSSI is output to the automatic gain control unit 220. The average received power measurement unit 210 may be a component of a demodulator.

The automatic gain control unit 220 calculates a gain of the variable gain amplifier 120 (hereinafter referred to as 'VGA gain') using the BB NRSSI input from the average received power measurement unit 210, To a variable gain amplifier (120). The variable gain amplifier 120 adjusts the signal level using the VGA gain received from the automatic gain control unit 220, thereby finally performing automatic gain control. The manner in which the automatic gain control unit 220 calculates the VGA gain will be described in detail below. The automatic gain control unit 220 may be one component of the L1 control (L1 Control).

On the other hand, the automatic gain control unit 220 can calculate the VGA gain repeatedly for each period for estimating the average received power described below.

Hereinafter, a method for estimating the BB NRSSI using the reception signal input from the front end module 100 will be described in detail.

2 is a diagram illustrating an NB-IoT downlink frame structure according to an embodiment of the present invention.

As shown in Fig. 2, the length of one frame is 10 ms, and one frame includes 10 subframes. One subframe constitutes 14 Orthogonal Frequency Division Multiplexing (OFDM) symbols, and one subframe includes 2 slots. A primary synchronization signal NPSS (Narrowband Primary Synchronization Signal) is allocated and transmitted for each sixth subframe of each frame. The NPSS signal occupies one anchor resource block and uses 11 subcarriers among one resource block (RB) composed of a total of 12 subcarriers. And the NPSS signal is carried on the last 11 symbols among the 14 OFDM symbols. The NB-IoT downlink frame structure is described in the NB-IoT standard, which will be apparent to those skilled in the art and will not be described in further detail.

The average received power measurement unit 210 according to the embodiment of the present invention can estimate the BB NRSSI according to two modes according to the embodiment of the present invention. Two modes are anchor RB (anchor resource block) mode and non-anchor RB (non-anchor resource block) mode. The anchor RB mode represents a case where an average received power is estimated by a resource element (RE) in which a NPSS signal as a synchronization signal is transmitted, and a non-anchor RB mode represents a resource element (RE) And only the data and control signals are transmitted).

First, a method for estimating the BB NRSSI in the anchor mode will be described below.

)는 아래의 수학식 1과 같이 표현된다. As described above, the NPSS signal is transmitted every fourth to 14th OFDM symbols of the sixth subframe of each frame. In the NB-IoT standard, the last 12th subcarrier is not used. The average received power measurement unit 210 estimates the NRSSI using resource elements (REs) corresponding to the remaining NPSSs except for the last 12th subcarrier. The received signal at the RE position of the NPSS (i.e., the resource element corresponding to the remaining NPSS except for the last 12th subcarrier)

) Is expressed by the following equation (1).

는 서브캐리어 지수를 나타내고, i는 NPSS 서브프레임 내 사용가능한 OFDM 심볼 지수를 나타내며,

은 슬롯 지수를 나타낸다. 그리고, H는 해당 RE(즉, NPSS의 자원요소)의 주파수응답을 나타내고, X는 해당 서브캐리어에 실려 전송되는 NPSS 신호를 나타내며, N은 해당 RE의 잡음을 나타낸다. 수학식 1의 수신신호에 대한 순시 전력을 아래의 수학식 2와 같이 표현된다. In Equation (1)

Denotes the subcarrier index, i denotes the usable OFDM symbol index in the NPSS subframe,

Represents the slot index. H denotes the frequency response of the RE (that is, the resource element of the NPSS), X denotes the NPSS signal transmitted on the corresponding subcarrier, and N denotes the noise of the corresponding RE. The instantaneous power of the received signal of Equation (1) is expressed as Equation (2) below.

The average received power measurement unit 210 may perform Infinite Impulse Response (IIR) filtering on the instantaneous power of Equation (2) as shown in Equation (3) to obtain BB NRSSI.

는 이전까지의 IIR 필터링된 BB NRSSI를 나타내고, G(0.5<G<1)는 감쇠 계수(decay factor)를 나타낸다. In Equation (3)

Represents the previous IIR filtered BB NRSSI, and G (0.5 <G <1) represents the decay factor.

Next, a method for estimating the BB NRSSI in the non-anchor mode by the average received power measuring unit 210 will be described.

)와 순시 전력(

)은 아래의 수학식 4와 같다. In the non-anchor mode, the average reception power measurer 210 estimates BB NRSSI using resource elements (REs) of the NRS in a subframe in which a narrowband reference signal (NRS) is transmitted. The received signal at the RE position of the NRS (

) And instantaneous power (

) Is expressed by Equation (4) below.

The average reception power measurer 210 can perform Infinite Impulse Response (IIR) filtering on the instantaneous power of Equation (4) as shown in Equation (5) to obtain BB NRSSI.

는 이전까지의 IIR 필터링된 BB NRSSI를 나타내고, G'(0.5<G<1)는 감쇠 계수(decay factor)를 나타낸다.In Equation (3)

Represents the previous IIR filtered BB NRSSI, and G '(0.5 <G <1) represents the decay factor.

Meanwhile, in the anchor resource block mode, the average received power measurer 210 can estimate the BB NRSSI using both the NPSS method and the NRS method described above. The period in which the estimated BB NRSSI is transmitted to the automatic gain control unit 220 as shown in Equations (3) and (5) can be set within a range satisfying a long-term fading condition. As an example, this period may be from 10 ms to 100 ms.

Hereinafter, a method of performing AGC using the BB NRSSI received from the average reception power measurer 220 by the automatic gain controller 220 according to the embodiment of the present invention will be described. The automatic gain control unit 220 may perform AGC based on a decimal scale or based on a dB scale.

First, a method in which the automatic gain controller 220 performs AGC based on a decimal scale will be described in detail with reference to FIG.

3 is a block diagram showing an automatic gain control unit 220a according to the first embodiment of the present invention.

3, the automatic gain controller 220a according to the first embodiment of the present invention includes a first division operator 221, a second division operator 222, and a log operator 223.

The first division operator 221 divides the current gain (Curie GG) by the BN NRSSI (P) input from the average received power measurement unit 220.

The second division operator 222 divides the margin M by the output CurG / P of the first division operator 221 and outputs CurG / (P * M).

)을 적용하여 최종적으로 새로운 Gain(NewG_dB)을 출력한다. The log operator 223 multiplies the input CurG / (P * M) by the log value (

) To finally output a new gain (NewG_dB).

In this way, the automatic gain control unit 220a can calculate the VGA gain through a simple mathematical operator, which can be derived through the mathematical approach described below.

Referring to Equation 1 and Equation 4, the frequency-domain analog signal Ya and the RF (Radio Frequency) NRSSI (Q) at the input terminal of the variable gain amplifier 120 shown in FIG. It is expressed as.

The analog signal given by Equation (6) is mapped on a one-to-one basis with a resource element (RE) used for obtaining the BB NRSSI.

Simplifying Equation (1) and Equation (4), the received signal Yd and BB NRSSI used to estimate the BB NRSSI are expressed as Equation (7) below.

In Equation (7), CurG denotes a gain value of a current decimal scale applied to the automatic gain amplifier 120. [

On the other hand, a new gain Gain (that is, a gain to be applied to the automatic gain amplifier 120) calculated and output by the automatic gain controller 200a is set to 1 by setting the output signal of the automatic gain amplifier 120 to 1 It is set to normalize. Therefore, the new gain NewG is set as shown in Equation (8) below.

In Equation (7), M is a margin to prevent clipping of the instantaneous signal higher than the average power. That is, M is a margin for reflecting the value of PARR (Peak to Average Power Ratio).

If NewG_dB or NewG [dB] of the new gain (NewG) and the dB scale (NewG_dB or NewG [dB]) is substituted into Equation (7) instead of Q of Equation

The automatic gain controller 220a according to the first embodiment of the present invention calculates a new gain NewG_dB by applying Equation (9) and outputs it to the variable gain amplifier 120. [ When the calculation of Equation (9) is blocked by an operator, the automatic gain control unit 220a includes the operator as shown in FIG.

The automatic gain control unit 220a according to the first embodiment of the present invention receives the BB NRSSI value from the average received power measurement unit 210 every predetermined period. The automatic gain control unit 220a previously stores the current gain CurG and the margin M applied before receiving the BB NRSSI value. Here, the margin is preset by the user. The automatic gain control unit 220a uses the first division operator 221 to divide the current gain CurG into BB NRSSI and divides it by the second division operator 222 again into a margin M. The output value of the second division operator 222 is a new gain NewG of decimal scal. The automatic gain control unit 220a converts the new gain NewM of DayMale scale into the dB scale using the log operator 223 and finally outputs it to the variable gain amplifier 120. [ On the other hand, the new gain (NewG) of the decimal scale is stored or updated as the current gain (CurG).

Next, a method of performing automatic gain control (AGC) based on a decimal scale will be described in detail with reference to FIG.

4 is a block diagram illustrating an automatic gain control unit 220b according to a second embodiment of the present invention.

4, the automatic gain control unit 220b includes a log operator 224, a first subtraction operator 225, and a second subtraction operator 226 according to the second embodiment of the present invention. Since the division operator in FIG. 3 is replaced with a subtraction operator in dB scale, FIG. 4 includes a subtraction operator.

)을 적용하여 출력한다. 도 4에서 로그 연산자(224)의 출력 값을 P_dB로 나타내었다. The log operator 224 converts the BB NRSSI input from the average received power measurement unit 220 into a log value (

). In FIG. 4, the output value of the log operator 224 is represented by P_dB.

The first subtracting operator 225 subtracts the output value of the log operator 224 from the gain (CurG_dB) of the current dB scale.

The second subtracting operator 226 subtracts (CurG_dB - P_dB) - M_dB by subtracting the output (CurG_dB - P_dB) of the first subtracting operator 221 from the margin M_dB. The output value of the second subtraction operator 226 is a new VGA gain (NewG_dB).

As described above, the automatic gain controller 220b according to the second embodiment of the present invention can calculate the VGA gain through a simple mathematical operator, which can be derived through the mathematical approach described below.

From Equations (6) and (7), the RF NRSSI of the dB scale can obtain Equation (10) below.

In Equation (10), P_dB represents the BB NRSSI of the dB scale, and CurG_dB represents the current gain of the dB scale. Expressed as Equation (11) below.

And the expression of the dB scale for the margin (M) is expressed as Equation (12) below.

Using the above equations (11) and (12), a gain (NewG_dB) of a new dB scale to be applied to the variable gain amplifier 120 is expressed by Equation (13) below.

The automatic gain control unit 220b according to the second embodiment of the present invention calculates a new gain NewG_dB by applying Equation (12) and outputs it to the variable gain amplifier 120. [ When the calculation of Equation (13) is blocked by an operator, the automatic gain control unit 220b includes an operator as shown in FIG.

The automatic gain control unit 220b according to the second embodiment of the present invention receives the BB NRSSI value from the average received power measurement unit 210 at predetermined intervals. The automatic gain control unit 220b previously stores the current gain (CurG_dB) of the applied dB scale and the margin (M_dB) of the dB scale before receiving the BB NRSSI value. Here, the margin of the dB scale is preset by the user. The automatic gain control unit 220b uses the log operator 224 to convert the BB NRSSI value to a dB scale. The automatic gain control unit 220b subtracts the BB NRSSI (P_dB) of the dB scale from the current gain (CurG_dB) of the dB scale using the first subtraction operator 225 and subtracts the second subtraction operator 226 from this value And subtract the margin (M_dB) of the dB scale again. The output value of this second subtracting operator 226 is a dB scale (decimal new gain NewG_dB) applied to the variable gain amplifier 120. On the other hand, the new gain NewG_dB of the dB scale is the current gain of the dB scale (CurG_dB ). &Lt; / RTI &gt;

As described above, the automatic gain control apparatus according to the embodiment of the present invention can measure the average received power to meet the long-term fading condition. In addition, the automatic gain control apparatus according to the embodiment of the present invention can acquire a gain through a simple mathematical operator on the average received power measured without a separate reference power estimation. Accordingly, the automatic gain control apparatus according to the embodiment of the present invention can perform automatic gain control with low power.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (20)

A terminal for processing a received signal on an object Internet,
A front-end module that adjusts the received signal using a gain and converts the received signal into a baseband signal that is a digital signal,
An average received power measurement unit for estimating an average power for the baseband signal in a frequency domain, and
And an automatic gain controller for determining the gain using the average power and outputting the gain to the front-end module. The method according to claim 1,
Wherein the automatic gain control unit calculates a new gain using a first value that is a value obtained by dividing a current gain among the gains by the average power. 3. The method of claim 2,
Wherein the automatic gain control unit calculates a second value that is a value obtained by dividing the first value by a predetermined margin,
And the second value is the new gain. The method according to claim 1,
Wherein the gain and the average power are dB scales,
Wherein the automatic gain controller calculates the new gain using a first value that is a value obtained by subtracting an average power of the dB scale from a current one of the gains of the gain. 5. The method of claim 4,
Wherein the automatic gain control unit calculates a second value by subtracting a margin of a predetermined dB scale from the first value,
And the second value is the new gain. The method according to claim 1,
Wherein the average received power measurement unit estimates the average power through an infinite impulse response filter. The method according to claim 1,
Wherein the average reception power measurer estimates the average power using the baseband signal corresponding to a narrowband primary synchronization signal among the reception signals. The method according to claim 1,
Wherein the average reception power measurer estimates the average power using the baseband signal corresponding to a narrowband reference signal among the reception signals. The method according to claim 1,
Wherein the average reception power measurement unit measures the average power and transmits the measured average power to the automatic gain control unit satisfies a long-term fading condition. An automatic gain control apparatus for controlling a gain, which is a factor for adjusting a level of a signal input from an object Internet to an analog digital converter,
An average reception power measuring unit for estimating an average power of the output signal of the analog-to-digital converter in the frequency domain, and
And an automatic gain controller for calculating a new gain using the current gain among the gains and the average power. 11. The method of claim 10,
Wherein the automatic gain control unit calculates the new gain using a first value that is a value obtained by dividing the current gain by the average power. 12. The method of claim 11,
Wherein the automatic gain control unit calculates a second value by dividing the first value by a predetermined margin and converts the second value to a dB scale,
And the second value of the dB scale is the new gain. 11. The method of claim 10,
Wherein the gain and the average power are dB scales,
Wherein the automatic gain control unit calculates the new gain using a first value that is a value obtained by subtracting the average power of the dB scale from the gain of the dB scale. 14. The method of claim 13,
Wherein the automatic gain control unit calculates a second value by subtracting a margin of a predetermined dB scale from the first value,
And the second value is the new gain. A method for automatic gain control of a terminal in an Internet of objects,
Generating a first signal by applying a current gain to the received signal,
Converting the first signal to a digital signal,
Estimating an average power in a frequency domain using the digital signal;
Calculating a new gain using the current gain and the average power, and
And applying the new gain to the received signal. 16. The method of claim 15,
Wherein the calculating step comprises:
Calculating a first value that is a value obtained by dividing the current gain by the average power, and
And calculating the new gain using the first value. 17. The method of claim 16,
Wherein the calculating step further includes calculating a second value which is a value obtained by dividing the first value by a predetermined margin,
And wherein the second value is the new gain. 16. The method of claim 15,
Wherein the current gain and the average power are dB scales,
Wherein the calculating step comprises:
Calculating a first value that is a value obtained by subtracting the average power of the dB scale from the current dB scale gain, and
And calculating the new gain using the first value. 19. The method of claim 18,
Wherein the step of calculating further comprises calculating a second value which is a value obtained by subtracting a margin of a predetermined dB scale from the first value,
And wherein the second value is the new gain. 16. The method of claim 15,
Wherein the estimating comprises estimating the average power via an Infinite Impulse Response filter.

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