KR20010084582A - Apparatus and method for controlling a signal gain in transmitter - Google Patents

Abstract

PURPOSE: An auto gain control apparatus of a signal transmission apparatus through a middle transmission medium and a method thereof are provided, which can output a signal with a predetermined output power level by adjusting a gain control level automatically according to a power level of an input signal when transmitting the signal through the middle transmission medium. CONSTITUTION: In a wireless communication apparatus, a signal is provided to a remote controlled module from a mother body through a middle transmission medium, and the remote controlled module transmits the received signal to the external with a predetermined output power level. The mother body comprises the first path(214) having the first power detector(219) detecting a power level of an input signal from the external, and the second path(213) comprising the first gain control part(216) amplifying/attenuating the input signal according to the first gain control signal and controlling a gain of the input signal to output it toward the middle transmission medium. The mother body also comprises the first unit outputting the first gain control signal in correspondence to an output value of the fist power detector.

Description

APPARATUS AND METHOD FOR CONTROLLING A SIGNAL GAIN IN TRANSMITTER

The present invention relates to a wireless communication system such as cellular, PCS, IMT-2000, and more particularly, in consideration of a path loss of a medium when transmitting a signal from one module to another module through a predetermined intermediate transmission medium. And apparatus and method for automatically adjusting and setting the signal gain.

An optical relay system or a microwave relay system in a wireless communication system such as cellular, PCS, or IMT-2000 includes a RIU (hereinafter referred to as a parent) and an mRS (hereinafter referred to as a remote module) that interfaces with a base station. The parent and remote modules are connected to a predetermined intermediate transmission medium (fiber optics for optical relay systems, and microwaves for microwave relay systems), and the parent relays signals between the base station and the remote modules via the intermediate transmission medium. That is, the parent provides a signal from the base station to the remote module through the intermediate transmission medium, and receives the signal from the remote module provided through the intermediate transmission medium and provides the signal to the base station. The remote module receives the signal of the base station provided from the intermediate transmission medium and provides the antenna with a predetermined power, and provides the signal received through the antenna to the intermediate transmission medium.

On the other hand, in the conventional relay system, the level of the base station signal provided to the mother varies depending on the state of the base station, and the signal level provided to the remote module also varies depending on the intermediate transmission medium (the occurrence of path loss) or the signal level from the mother. Do. However, since the output power of the signal to be transmitted through the antenna in the remote module is set in advance, the parent needs to adjust the gain of the signal according to the signal level from the base station and output the signal at a predetermined level. It is necessary to adjust the signal gain according to the signal level from the medium and provide it to the antenna. To this end, in the related art, an operator uses a device such as a spectrum analyzer to measure signal levels provided to the parent and remote modules, and accordingly, a method of manually adjusting signal gains of the parent and remote modules is used. However, in such a conventional method, the operator must carry a device such as a spectrum analyzer directly to measure the signal level, and in the case of an inexperienced person, the process of measuring the signal level and adjusting the gain adjustment level according to the signal level is performed correctly. The problem is that you can't.

In addition, in the conventional method, there is a problem in that, when a path loss is changed or a level of an input signal is changed by a factor between the parent and the remote module, it cannot be compensated properly.

SUMMARY OF THE INVENTION The present invention has been made to solve this problem, and an object of the present invention is to output a signal at a preset output power level by automatically adjusting a gain adjustment level according to the power level of an input signal when transmitting a signal through an intermediate transmission medium. It is to provide a device that can.

Another object of the present invention is to provide a method for automatically outputting a signal at a predetermined output power level by automatically adjusting a gain control level according to a power level of an input signal when transmitting a signal through an intermediate transmission medium.

In order to achieve this object, the present invention provides a remote module with a signal input to the mother module through an intermediate transmission medium (optical fiber), and the remote module is provided to an apparatus for transmitting the received signal to the outside at a predetermined output power level. A mother system comprising: a first path having a first power detector for detecting a level of a signal provided from the outside; A second path including a first gain adjusting unit configured to amplify or attenuate the input signal according to the first gain control signal, and output the first signal, and adjust the gain of the input signal from the outside and output the signal to the intermediate transmission medium; And a first means for outputting a first gain control signal corresponding to an output value of the first power detector in consideration of the path loss of the signal generated when providing the input signal to the remote module via the intermediate transmission medium: A third path having a second gain adjuster for amplifying or attenuating the signal transmitted through the intermediate transmission medium according to a second gain control signal, and a high output amplifier for amplifying the output signal of the second gain adjuster; A fourth path for detecting a power level of a signal output through the third path; And second means for outputting a second gain control signal for outputting a predetermined power level in accordance with the signal level from the intermediate transmission medium and the signal level from the fourth path through communication with the mother.

The present invention also provides a signal from the mother to the remote module through the intermediate transmission medium, the remote module transmits the received signal to the outside at a predetermined power level, the automatic setting mode is started. If the parent is in communication with a remote module, detecting a path loss amount of the signal by the intermediate transmission medium; The mother amplifying or attenuating an external signal with a predetermined gain according to a path loss amount and a power level of an input signal provided to the mother and providing the intermediate signal to an intermediate transmission medium; The remote module includes controlling the gain of the signal transmitted from the intermediate medium such that the output level of the final output signal is equal to or less than the preset value, and then controlling the gain of the signal such that the power level of the final output signal is the preset value. .

The present invention also provides a signal from a mother to a plurality of remote modules through an intermediate transmission medium, wherein the remote module transmits the received signal to the outside at a predetermined power level. The parent may directly or indirectly detect a maximum path loss amount of a signal by the intermediate transmission medium through communication with remote modules; The mother amplifying or attenuating the external signal with a predetermined gain according to the maximum path loss amount and the power level of the signal provided to the mother and providing the intermediate signal to the intermediate transmission medium; The remote module includes controlling the gain of the signal such that the power level of the final output signal is a preset value after controlling the gain of the signal from the intermediate medium such that the power level of the final output signal is equal to or less than a preset value.

The present invention also provides a remote module with a signal from a parent via an intermediate transmission medium, and the remote module transmits the received signal to the outside at a predetermined power level. When the automatic setting mode is started, The mother amplifies or attenuates an external signal with a predetermined gain according to the maximum path loss amount of the signal by the predetermined intermediate transmission medium and the power level of the signal provided to the mother, and provides the intermediate transmission medium to the intermediate transmission medium; The remote module controls the gain of the signal from the intermediate medium so that the signal provided from the parent according to the maximum path loss value is smaller than the power level of the preset final output signal, and then the signal so that the power level of the final output signal becomes the preset value. Controlling the gain.

1 is a schematic diagram illustrating an optical repeater in a signal transmission apparatus via an intermediate transmission medium according to the present invention;

FIG. 2 is a schematic block diagram of a matrix constituted in the apparatus of FIG. 1; FIG.

3 is a schematic block diagram of a remote module configured in the apparatus of FIG. 1;

4 is a view showing a process of an automatic gain control method of a signal transmission apparatus through an intermediate transmission medium according to the present invention;

5 is a view showing another embodiment of an automatic gain control method of an apparatus for transmitting a signal through an intermediate transmission medium according to the present invention.

<Description of the symbols for the main parts of the drawings>

1: repeater 2: mother

3,, 4,5,6: optical fiber 7,8,9: remote module

21: transmitting circuit 22: receiving circuit

23: all-optical module 24: WDM coupler

25 optical fiber 26 photoelectric module

31: transmitting circuit 32: receiving circuit

33: WDM Coupler 34: Photoelectric Module

35: all-optical module

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Although the following description has been given as an example of an optical repeater, it is possible for those skilled in the art to apply the present invention to any system in which two modules transmit and receive signals through an intermediate transmission medium. It will be easy to see.

1 is a schematic diagram of an optical relay system, as shown, a base station 2 is connected to a base station 1, and the base station 2 is connected to a remote module 7 through an optical fiber 3, 4, 5, 6. 8,9). In FIG. 1, a plurality of optical fibers 4, 5, 6, are branched from one optical fiber 3, but, as necessary, between the parent 2 and the remote module 7, 8, 9, respectively. 1: 1 connection to the optical fibers (4, 5, 6) can also be.

In this configuration, the parent 2 provides the signals provided from the base station 1 to the remote modules 7, 8, 9 via the optical fibers 3, 4, 5, 6, and the optical fibers 3, 4, 5, 6) Receives and receives the received signal from the remote module (7, 8, 9) provided through the base station (1).

Fig. 2 shows a detailed block diagram of the above-described parent 2, and in the present invention, since it is related to providing the transmission input signals of the base station provided through the parent 2 to the remote modules 7, 8 and 9, Only the transmission circuit 21 in (2) is shown specifically, and the reception circuit 22 which receives the reception signal from the remote module 7, 8, 9 is not shown in detail. It can be easily understood by those skilled in the art that the receiving circuit 22 can be configured in the same manner as in the prior art.

As shown, the signal provided from the base station 1 is provided to the directional coupler 211, which forwards the signal from the base station 1 to the primary path 213 and the secondary path 214, respectively. . Here, it will be readily apparent to those skilled in the art that a power divider may be used instead of a directional coupler.

Main path 213 is comprised of amplifiers 215 and 218, gain controller 216 and filter 217, and the order of combining these amplifiers 215 and 218, gain controller 216 and filter 217 may be altered, or as needed. Accordingly, amplifiers 215 and 218 may be added or removed. The gain controller 216 is connected to the processor 220 and is configured to adjust and output the gain of the input signal according to the control from the processor 220.

The gain-adjusted signal in the main path 213 is converted into an optical signal through the all-optical module 23 and provided to the WDM coupler 24, which provides this signal to the optical fiber 25. In the all-optical module 23, a separate device for measuring the output level of the optical signal is configured, and the optical signal output level information measured from the device is provided to the processor 220.

The auxiliary path 214 is configured with a power detector 219, which detects and provides an output voltage corresponding to the power level of the input signal provided from the base station 1 to the processor 220. The power detector 219 may simply be configured to measure the input signal power level vs. the output voltage using a log amplifier or determine the maximum signal loss versus the input signal level using an AGC loop.

On the other hand, the signals from the remote modules 7, 8, 9 provided through the optical fiber 25 are provided to the photoelectric module 26 through the WDM coupler 24, and converted into electrical signals in the photoelectric module 26. The signals of the remote modules 7, 8, 9 are provided to the base station 1 and the processor 221. Here, the signals of the remote modules 7, 8, and 9 are classified into two types. One is a signal received at the antennas of the remote modules 7, 8, 9, which is provided to the base station 1 via the photovoltaic module 26, the receiving circuit 22 of the parent 2, and the other As described later, a signal provided from a processor of the remote modules 7, 8, and 9 (this signal is a modem signal, such as input level information of an optical signal received by the remote modules 7, 8, 9, as described later). This signal is provided to the processor 220 through the photovoltaic module 26 and the modem 221.

The processor 220 is provided with the voltage information from the power detector 219 and the optical signal input level information signal from the remote modules 7, 8, 9 as described above, and the processor 220 uses this information. The gain controller 216 controls the gain. The process of the processor 220 controlling the gain of the gain controller 216 will be described in detail later. In addition, the processor 220 is connected to the all-optical module 23 and the photoelectric module 26 through the modem 221 as described above, and communicates with the processors configured in the remote modules 7, 8, 9. This is possible.

3 shows a block diagram showing the configuration of remote modules 7, 8, 9. In the present invention, since the signal provided through the mother 2 is transmitted to the antenna, only the transmission circuit 31 in the remote modules 7, 8, and 9 is illustrated in detail, and the signal is transmitted to the mother 2. The receiver circuit 32 is not shown in detail. It will be apparent to those skilled in the art that the receiving circuit 32 can be configured in the same manner as in the prior art.

As shown, the optical fiber 25 is connected to the photoelectric module 34 and the all-optical module 35 through the WDM coupler 33, and the amplifiers 311 and 313 constituting the main path 36 are provided in the photoelectric module 34. And are connected in series with the filter 312, the gain controller 314, the high power amplifier 315, and the cavity filter 316. Thus, the signal from the photovoltaic module 34 is amplified and filtered by the amplifiers 311, 313 and the filter 312, and finally amplified through the high output amplifier 315, and unnecessary components through the cavitation filter 316. This is filtered and then provided to the directional coupler 320.

The directional coupler 320 is connected to the antenna and auxiliary path 37 such that the final signal filtered by the cavitation filter 316 is provided to the antenna while being provided to the power detector 317. The power detector 317 detects and provides power to the processor 318 provided to the antenna, i.e., the final transmission output signal of the cavitation filter 316, and the processor 318 is connected to the power value of the power detector 317. Accordingly, the driving (gain adjustment) of the gain controller 314 is controlled. When the output power detector is built in the high output amplifier 315, the processor 318 uses the port of the high output amplifier 315, that is, the port for monitoring the output of the high output amplifier 315. May be configured to control the drive of gain controller 314 by monitoring the output of &lt; RTI ID = 0.0 &gt;

On the other hand, a separate device for measuring the input power level of the optical signal is configured in the photoelectric module 34, and the optical signal input power level information measured from the device is transmitted to the processor 318 through the modem 319. Is provided. The processor 318 is connected to the photovoltaic module 34 and the all-optical module 35 through a modem 319 and communicates with the processor 220 in the parent 2 through these.

The signal received through the antenna is provided to the matrix 2 via the receiving circuit 32, the all-optical module 35, the WDM coupler 33 and the optical fiber 25.

The process of adjusting the signal level in the optical repeater configured as described above will be described in detail with reference to FIG.

The optical repeater of the present invention may be switched from the off state to the on state, or the user may perform a signal level adjustment process by setting the initial automatic setting mode (400). First, when the optical repeater is turned on, the parent 2 provides the signals of the base station 1 to the remote modules 7, 8, 9 while the processor 220 uses the polling signal to transmit the remote module ( Confirmation of the remote modules 7, 8, 9 and status information in the remote modules 7, 8, 9 while sequentially communicating with the processors 318 in the 7,8, 9 (photoelectric module in the remote module) Information of the optical signal input power level detected at 34) is obtained (401). At this time, since the optical repeater is turned on, the processors 220 and 318 in the parent 2 and the remote modules 7, 8, and 9 may communicate with each other, as described below. 9) Always obtain the status information inside. Therefore, when the user sets the initial automatic setting mode, the process of obtaining the status information in the remote modules 7, 8, and 9 by using the polling signal may be omitted.

After the processor 220 obtains the status information of the remote module 7, 8, 9 as a polling signal, the parent 2 and the remote module 7, 8, 9 perform a process of adjusting the level of the input signal. However, this process is slightly different depending on the connection state between the parent (2) and the remote module (7, 8, 9). That is, the one-to-one connection between the parent 2 and the remote modules 7, 8, and 9 is connected to one parent 2 and one remote module 7, 8, and 9 through one optical fiber, As shown in FIG. 1, there may be a one-to-many connection in which a plurality of remote modules 7, 8, and 9 are connected to one parent 2, and in the process of controlling the power level of the input signal according to this connection method. There is a slight difference.

The case where the parent 2 and the remote modules 7, 8, and 9 are connected one-to-one is as follows.

When connected one-to-one, the processor 220 in the parent 2 is provided with the output power level of the optical signal via the all-optical module 23. In addition, since the optical signal input power level information detected by the photoelectric module 34 is provided from the processor 318 in the remote module 7, 8, 9, the processor 220 transmits the light transmitted through the all-optical module 23. The output level of the signal and the optical signal input level provided to the remote modules 7, 8, 9 can be known. Therefore, the processor 220 can detect the loss (optical transmission loss) that occurs when a signal is provided to the remote modules 7, 8, and 9 through the optical fiber 25, and the RF signal corresponding to the optical transmission loss amount The amount of loss can be calculated. RF loss refers to the amount of loss of the signal along with the loss of light when the electrical signal is transmitted / transformed and / or converted. Since the RF loss amount corresponds to the light loss amount, the RF loss amount corresponding to the light loss amount can be easily obtained. For example, the RF loss amount according to the light loss amount can be detected by making a table and setting the RF loss amount in advance.

At this time, since the processor 220 is provided with power level information of the input signal detected by the power detector 219, that is, power level information of the input signal provided from the base station 1 (step 402), the processor 220 is RF Considering the path loss amount and the signal level from the base station 1, the gain of the gain controller 216 is controlled so that the RF signal provided to the all-optical module 23 is at a predetermined power level. (Step 403).

On the other hand, when the high output amplifier 315 in the remote module 7, 8, 9 has a predetermined gain from an initial state and amplifies the gain of an input signal of a predetermined level or more, problems such as abnormality occurs in the high output amplifier 315. May occur. To prevent this, the processor 200 in the parent 2 controls the processor 318 to cause the processor 318 to keep the high output amplifier 315 off. At this time, the high output amplifier 315 amplifies the input signal at a predetermined ratio, so that the power level of the signal output from the high output amplifier 315 is lower than the predetermined (desired) power level. It is necessary to control so that the level of the provided signal is below a predetermined power level. Thus, the processor 220 controls the gain controller 314 to adjust the gain of the input signal to amplify the input signal while the high output amplifier 315 is on, so that the output power level is still high. Below the set power level, for example, 10-20dB below the required level. Subsequently, the processor 318 turns on the high power amplifier 315 under the control of the processor 220. As a result, the high power amplifier 315 amplifies the power level of the input signal. It will be below the set level.

Thereafter, the processor 318 measures the power level of the output signal provided from the power detector 317, and adjusts the gain of the gain controller 314 according to this power level so that the high output amplifier 315 of the predetermined power level is adjusted. Control to output a signal (step 404).

Next, the case in which the parent 2 and the remote module 7, 8, 9 are connected in a one-to-many manner is as follows.

In this case, by performing steps 400-1 and 401-2 as shown in FIG. 5, the processor 220 transmits the parent 2 through polling signals with the processors 318 in the remote modules 7, 8, and 9. RF path losses can be detected based on the optical loss between the &lt; RTI ID = 0.0 &gt;) and &lt; / RTI &gt; Thereafter, the processor 220 controls the gain of the gain controller 216 corresponding to the input signal power level 402-2 and the RF path loss amount from the base station 1 through the power detector 219, in this case The RF path loss amount corresponds to the number of remote modules 7, 8 and 9, and adjusts the gain of the gain controller 216 based on the maximum RF path loss value among these RF path loss amounts. That is, the input power level of the RF signal provided to the all-optical module 23 of the parent 2 corresponds to the maximum RF path loss value that may occur in the process of transmitting signals to the plurality of remote modules 7, 8, and 9. (403-1)

Next, the processor 220 in the parent 2 controls the processor 318 in each of the remote modules 7, 8, 9 to cause the processor 318 to keep the high output amplifier 315 off, Even if the amplified signal is amplified while the high output amplifier 315 is on, the gain of the gain controller 314 is maintained such that its output level is equal to or less than a preset power level (for example, about 10-20 dB below the required level). To control. Thereafter, the processor 220 controls the processor 318 to turn on the high output amplifier 315, so that the high output amplifier 315 amplifies the power level of the input signal, but the output level is below the preset power level. Will be. Thereafter, the processor 318 measures the power level of the signal provided from the power detector 317, and adjusts the gain of the gain controller 314 according to the measured power level so that the high power amplifier 314 is set to the power level. Control to output the following signals (step 404-2).

After performing the above steps 404, 404-2, the processors 318 in the remote modules 7, 8, 9 detect the output power level of the high output amplifier 315 by the power detector 317, and thus the high output amplifier ( 315 controls the gain of gain controller 314 to always output a signal of a predetermined power level.

Meanwhile, in the above description, the case in which the device capable of detecting the input power level of the optical signal is configured in the optical modules 7, 8, and 9 is described as an example. That is, the processor 220 in the mother 2 can detect the amount of light loss generated when the optical signal is provided to the remote modules 7, 8, 9, and thus the power of the signal output from the mother 2. The level and output power level of the high power amplifier 315 in the remote modules 7, 8, 9 could be set. However, when the device capable of detecting the input power level of the optical signal is not configured in the optical modules 23 and 34, a problem arises in that the above-described embodiment cannot be performed. In such a case, the present invention can be carried out as follows.

Even when the processor 220 in the parent 2 does not detect the optical path loss amount as described above, since the minimum link loss amount and the maximum link loss amount are set at the time of installation of the system, this information can be used. That is, the mother 2 regards the amount of optical loss with the remote modules 7, 8, and 9 as a preset maximum link loss and sets the level of the signal output from the mother 2 correspondingly. However, when the optical loss amount is regarded as the maximum link loss amount, the power level (output power level of the photoelectric conversion module) of the signal provided to the remote module 7, 8, 9 may be excessively high. The high power amplifier 315 in 8, 9 may be overloaded. To prevent this, the remote modules 7, 8 and 9 set the gain of the path to the minimum (i.e., calculate the signal power level provided to the remote modules 7, 8 and 9 when the minimum link loss occurs). The high output amplifier 315 controls the gain of the gain controller 314 to output a signal of a preset level. At this time, the maximum power level of the input signal provided to the remote modules 7, 8, and 9 becomes the level when the minimum link loss occurs, that is, the maximum signal power level, so that the gain of the remote module is adjusted based on this. . The gain controller 314 sets the level of the output signal provided to the high output amplifier 315 low, so that the level of the signal output by the high output amplifier 315 is lower than the target level. By doing so, it is possible to prevent abnormality in the high output amplifier 315 as a high level signal is provided to the high output amplifier 315.

Thereafter, the processor 318 in the remote module 7,8,0 adjusts the gain of the gain controller 314 according to the power level detection information from the power detector 317 so that the high output amplifier 315 of the target power level is adjusted. Control to output a signal.

As described in the above description, the parent in the present invention measures the power level of the input signal provided from the base station while detecting the path loss by measuring the power level of the signal provided to the remote module using the level of the optical signal, In consideration of this path loss, the level of the signal input to the all-optical conversion module is adjusted, and the remote module appropriately adjusts the level of the signal provided from the parent according to the power level of the final target output signal. The device does not need to adjust gains in the parent and remote modules.

In the above-described embodiment, the case of the direct transmission method in which the input signal is not internally transformed to the first and second orders has been described. However, the present invention may be applied to the case of converting the first signal to the first and second order. Those of ordinary skill will readily know.

In addition, in the above-described embodiment, the optical repeater has been described as an example. However, the present invention is applied to all apparatuses having an intermediate transmission medium and thus adjusting the level of the input signal in consideration of the loss of the link and determining the final output level. It will be readily appreciated that it can be applied.

As described above, in the present invention, in a device for transmitting a signal from a mother to a remote module through an intermediate transmission medium, the gain of the mother amplifying the input signal is automatically set according to the path loss generated by the transmission medium and the level of the input signal. The remote module has the effect of automatically adjusting the gain of the entire signal path according to the signal power level from the transmission medium and the power level of the final output signal.

Claims (5)

In the wireless communication device for providing a signal from the parent to the remote module via an intermediate transmission medium, the remote module transmits the signal received from the parent to the outside at a predetermined output power level, The matrix, A first path having a first power detector for detecting a power level of an input signal provided from the outside; A second path including a first gain control unit configured to amplify / attenuate the input signal according to a first gain control signal, and output the amplified signal from the outside to the intermediate transmission medium; A first means for outputting the first gain control signal in response to an output value of the first power detector in consideration of a path loss of a signal generated when providing the input signal to the remote module via the intermediate transmission medium; And: The remote module, A third path having a second gain control unit for amplifying / attenuating and outputting an input signal transmitted through the intermediate transmission medium according to a second gain control signal, and a third output path having a high output amplifier for amplifying the output signal of the second gain control unit; ; A fourth path for detecting a power level of a signal output through the third path; Second means for outputting said second gain control signal in accordance with a signal level from said intermediate transmission medium and a signal level from said fourth path through communication with said mother; Automatic gain control device of the signal transmission apparatus via the intermediate transmission medium comprising a. The method of claim 1, The first and second means are automatic processors of the signal transmission device via the intermediate transmission medium consisting of a processor. The method according to claim 1 or 2, Automatic gain control device of the signal transmission device through the intermediate transmission medium, characterized in that the intermediate transmission medium is an optical fiber. In the method of driving a wireless communication system for providing a signal from the mother to one or more remote modules through an intermediate transmission medium, the remote module transmits the received signal to the outside at a predetermined power level, When the auto setting mode is started, The parent detecting a maximum path loss amount of a signal by the intermediate transmission medium through communication with the remote modules; The mother amplifying / attenuating the external signal with a predetermined gain according to the maximum path loss amount and the power level of the signal provided to the mother and providing the intermediate signal to the intermediate transmission medium; The remote module controls the gain of the signal such that the power level of the final output signal is a preset value after controlling the gain of the signal transmitted from the intermediate medium such that the power level of the final output signal is less than or equal to a preset value. An automatic gain control method of a signal transmission apparatus via an intermediate transmission medium having a step. In the method of driving a wireless communication system for providing a signal from the mother to the remote module via an intermediate transmission medium, the remote module transmits the received signal to the outside at a predetermined power level, When the auto setting mode is started, The parent amplifying / attenuating the external signal with a predetermined gain according to a preset maximum path loss amount of the signal by the intermediate transmission medium and the power level of the signal provided to the mother and providing the intermediate transmission medium to the intermediate transmission medium; The remote module controls the gain of the signal from the intermediate medium so that the signal provided from the parent according to the maximum path loss value is smaller than the power level of a preset final output signal, and then the power level of the final output signal is set to a predetermined level. And controlling the gain of the signal to be a set value.