KR101417036B1 - Apparatus and method automatic gain control for up-signal in a wireless communication system by use of orthogonal frequency division multiple access system - Google Patents

Abstract

The present invention relates to an automatic gain control apparatus for an uplink signal in a wireless communication system using a time division scheme in which a signal transmission time and a signal reception time exist, An RF (Radio Frequency) signal separator for receiving a signal output from the first and second attenuators and repeatedly measuring an intensity value of the up signal by a predetermined number of times, And a controller for setting the attenuation values of the first and second attenuators to be maximized and repeating the intensity value of the received uplink signal for a predetermined number of times during the signal reception time And generates intensity values for the received uplink signal by measuring the uplink signal, And a control unit for controlling the setting of the attenuation values based on a result of the comparison between the calculated average value and a target value preset in the first and second attenuation units, When the calculated average value is smaller than a value obtained by subtracting the maximum settable range G dBm of the first and second attenuation units from the target value -A dBm of the first and second attenuation units, Sets the respective attenuation values to 0 and sets the calculated average value to a value obtained by subtracting the maximum settable range G dBm of the first and second attenuators from the target value -A dBm of the first and second attenuators The controller compares the difference between the calculated average value and the target value -A dBm with -2G / 3, and when the difference is smaller than -2G / 3, 2G / 3 and the above car Set to a plus value, and the attenuation value of the second attenuation section, characterized in that set -G / 3.

Automatic gain control, up signal, time division

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an apparatus and method for controlling an automatic gain of an uplink signal in an orthogonal frequency division multiple access (OFDMA) wireless communication system,

The present invention relates to a wireless communication system using a time division scheme, and more particularly, to a relay station, in order to maintain a constant signal strength in order to transmit an uplink signal received from a mobile station to a base station without degrading quality, An automatic gain control apparatus and method in an orthogonal frequency division multiple access (OFDM) wireless communication system for determining a received uplink signal strength at a relay station before transmitting the determined uplink signal strength to an upper base station and controlling an uplink signal strength according to the determined result .

2. Description of the Related Art [0002] With the recent demand for high-speed data transmission and mobility in recent mobile communication systems, various mobile communication systems have been developed and their performance is continuously improving. For example, a second generation communication system represented by a GSM (Globular System for Mobile Telecommunication) is still used in many countries, and a dramatic development of the IMT-2000 called 3G, which is represented by CDMA, It stands out. Recently, HSDPA with high-speed data transmission enhanced and Mobile WiMAX based on IEEE802.16e are leading the mobile communication market. In addition, a next generation mobile communication system capable of providing more transmission capacity is being studied and is being prepared for standardization.

The next-generation mobile communication system IMT-Advanced, which is called 4G, uses 2-8 GHz bandwidth, enables high-speed data transmission over 20 Mbps while on the move, adopts MIMO technology based on IPv6, adopts OFDMA or multi-carrier CDMA method is expected to be used.

Since the 4G system uses the frequency band of 2 to 8 GHz, the propagation loss in the air is larger than other services operating at a relatively low frequency, and it is very difficult to secure the visible distance in a complicated urban environment due to the high directivity of the 4G signal . An easy way to solve these problems is to increase the strength of the signal transmitted from the base station and the terminal station. This causes a load of the high output amplifier (HPA) of the base station to become too large. In addition, The life of the battery is shortened sharply.

Another big problem is that the use of terminals with high transmission power will harm the human body. Considering these conditions, it is considered that the cell radius of the next generation mobile communication system will be smaller than now.

However, reduction of the cell radius causes new problems. For example, a large number of base stations must be installed in a small area, and a backbone network must be expanded to provide seamless connection between a large number of base stations. Therefore, practical problems for implementing next generation wireless communication systems require cost reduction, reduction of base station size, and centralization of complex control circuits.

From this point of view, the radio-over-fiber (RoF) system has many benefits. In such a system, the MODEM card and the associated electrical circuits are placed in the central base station, and the RF signals are transmitted through the optical fibers using subcarriers. Therefore, each relay station is composed of only a photoelectric converter, an electric light converter, an electric signal amplifier, an antenna, and the like. These small relay stations can be installed on the electric pole and reduce the installation cost. In addition, all complex control functions can be centralized to base stations, simplifying the operation and management of relay stations. The RoF system can be used as a repeater to increase the cell radius and eliminate shaded areas without increasing antenna power.

FIG. 1 schematically shows an automatic gain control apparatus in a RoF system using a conventional time division method. Referring to FIG. 1, a transmission signal received at an antenna of an optical relay station 140 is transmitted through an optical line Transmits the signal to the base station 120 and the upper layer base station 100 and analyzes the received signal inputted from the TDD modem unit 104 of the upper layer base station 1000 to determine the strength of the uplink signal and then transmits the TDD switch adjustment information and the signal strength information To the optical relay station 140 through the optical base station 120 to control the intensity of the uplink signal by controlling the low noise amplifying unit 136 of the optical relay station 140.

FIG. 2 illustrates a transmission frame transmitted / received in a RoF system using a conventional time division scheme. In FIG. 2, a transmission transition gap (TTG) interval is set as a guard interval before an upstream signal interval. And transmits the signal gain information to the optical relay station 140 to adjust the strength of the uplink signal.

The transmission of the signal gain value of the received signal using the TTG depends on the distance between the optical relay station 140 and the terminal station and the round trip time according to the distance between the optical base station 120 and the optical relay station. The TDD modem unit 104 of the upper base station 100 determines the signal strength and transmits the signal strength to the optical relay station 140. In this case, Also, conventionally, when the initial value of the received upstream signal is smaller than the thermal noise of the optical transceiver module, there is a problem that the strength of the upstream signal can not be determined.

An object of the present invention is to maintain a constant signal strength in order to transmit an uplink signal received by a relay station to a mobile station in a wireless communication system using a time division scheme to a base station without degrading quality, The present invention relates to an apparatus and method for automatic gain control in an orthogonal frequency division multiple access (OFDM) wireless communication system for determining a signal strength of an upstream signal before it is transmitted to an upstream base station and controlling the strength of an upstream signal according to the determination result.

According to one aspect of the present invention, there is provided an automatic gain control apparatus for an upstream signal in an orthogonal frequency division multiple access (OFDM) wireless communication system using a time division scheme in which a signal transmission time and a signal reception time exist A first attenuator and second attenuators for controlling the attenuation of the upstream signal received during the signal reception time; and a second attenuator and second attenuator for inputting signals output from the first and second attenuators from an RF (Radio Frequency) A detector for repeatedly measuring the intensity value of the up signal at a predetermined number of times and converting the intensity value of the repeated upward signal into a digital value; and a controller for setting the attenuation values of the first and second attenuators to be maximized, And a controller for repeatedly measuring the intensity value of the uplink signal received at a predetermined number of times during the signal reception time, And calculating a mean value using at least one remaining value obtained by removing a maximum value and a minimum value among intensity values of the received uplink signal and outputting the calculated average value and the average value to the first and second attenuators in advance And a control unit for controlling the setting of the attenuation values based on the comparison result between the set target values, wherein the control unit calculates the average value of the first and second attenuation units, And the second settling range G dBm of the first and second attenuation units, and the second settable range G dBm of the second attenuation units, the calculated average value is set to the target value -A dBm Compares a difference between the calculated average value and the target value -A dBm with -2G / 3, when the difference is equal to or larger than a value obtained by subtracting a maximum settable range G dBm of the first and second attenuators from the calculated average value, If the difference is smaller than -2G / 3, the attenuation value of the first attenuation portion is set to -2G / 3 plus the difference, and the attenuation value of the second attenuation portion is set to -G / 3 .

According to another aspect of the present invention, there is provided a method for controlling automatic gain control of an uplink signal in an orthogonal frequency division multiple access (OFDM) wireless communication system using a time division scheme in which signal transmission time and signal reception time exist Setting the attenuation values of the first and second attenuators to be maximized and repeatedly measuring intensity values of the uplink signal received at a predetermined number of times during the signal reception time, Calculating a mean value using at least one remainder value obtained by removing a maximum value and a minimum value among intensity values of the received uplink signal; And controlling the setting of the attenuation values based on a comparison result between preset target values Wherein the step of controlling the setting of the attenuation values comprises the step of calculating the maximum settable range G dBm of the first and second attenuation units at the target value -A dBm of the first and second attenuation units, And setting each of the attenuation values to 0 if the first attenuation value is less than the first attenuation value and the second attenuation value is less than the second attenuation value, Comparing the difference between the calculated average value and the target value -A dBm to -2G / 3 when the difference is greater than or equal to a value obtained by subtracting the maximum settable range G dBm of -2G / 3; And setting the attenuation value of the first attenuation unit to -2G / 3 plus the difference, and setting the attenuation value of the second attenuation unit to -G / 3.

As described above, according to the present invention, not only can the signal strength be adjusted using only the uplink signal and the downlink signal interval without infringing the protection time interval of the transmission frame, and also the uplink and downlink Frame, and when the initial value of the received upstream signal is smaller than the thermal noise of the optical T / R module, the AGC is implemented by determining the strength of the upstream signal itself. Thus, the RF transmission signal suitable for the optical T / There is an effect of preventing deterioration of signal quality through optical transmission in advance.

In addition, the present invention proposes an algorithm that can adjust the signal gain by dividing the control period according to the intensity of the transmission signal, so that it is easy to implement the input signal of various strengths.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It will be appreciated that those skilled in the art will readily observe that certain changes in form and detail may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims. To those of ordinary skill in the art.

The present invention relates to a TDD (Time Division Duplexing) wireless communication system, which includes a base station and a remote station connected to the base station through an optical fiber link to transmit / receive signals to and from a plurality of mobile terminals, The TDD frame at the time of transmission is assumed to be composed of a down link, a transmission time gap (TTG), an uplink, and a receive time gap (RTG).

In the present invention, in order to control automatic gain control of a receiving end of a relay station in a RoF (Radio over Fiber) relay system, the relay station itself Thereby performing gain control.

3 is a block diagram of a receiving end of a relay station that performs Automatic Gain Control (AGC) in an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention. 3, a relay station according to the present invention includes an antenna for receiving an uplink signal, a circulator 328 for separating the received uplink signal from a downlink signal, a switch SW for outputting the uplink signal, (Low Noise Amplifiers) 324, 330, and 316 for low-noise amplifying the received uplink signal including a transmission line for transmitting the received uplink signal to a base station, The first and second attenuators 318 and 322 receive the amplified upstream signal and control the attenuation of the signal. The first and second attenuators 318 and 322 and the low-noise amplifiers 324 and 330, And outputs an uplink signal obtained by filtering attenuation and noise to an optical module (E / O) 310 and outputting it to a Detector (hereinafter referred to as 'DET' Signal separation unit 315, and the RF signal separation unit 315 6) 612 for converting the measured voltage value into a digital value, and an A / D converter (see FIG. 6) 612 for converting the measured voltage value into a digital value. (FGPA) for performing control of the first and second attenuators 318 and 322 on the basis of the upstream signal value converted into the digital value output from the detector 312, Gate Array, 314).

The detailed block diagram of the AGC for performing the AGC function in the orthogonal frequency division multiple access (OFDM) wireless communication system according to the preferred embodiment of the present invention will be described in more detail with reference to FIG.

6 is a detailed block diagram of AGC for automatic gain control in a relay station of an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention. Referring to FIG. 6, the AGC of the present invention includes a peak detector 610, an A / D converter 612, an FPGA 614, and first and second attenuators. 6 is a detailed block diagram of an AGC implemented in a receiving end of the RS in order to perform automatic gain control according to an embodiment of the present invention. In FIG. 6, FIG. 7 is a block diagram illustrating an AGC integrated circuit according to an embodiment of the present invention. Referring to FIG. 7, there is shown an AGC integrated circuit in the relay station of an orthogonal frequency division multiple access (Resistor-Transistor-Logic) is designed using a resistor and a transistor of an integrated circuit, and the present invention is not limited thereto, and the present invention is not limited thereto. It is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

4 is a diagram illustrating a time structure of upstream and downstream signal transmission frames in a signal transmission in an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention. Referring to FIG. 4, in a wireless communication system using the TDD scheme of the present invention, during a downlink signal transmission received from a base station, that is, during transmission time intervals 410 and 414 without infringing a guard time interval, And controls the signal strength by receiving an uplink signal during transmission of the uplink signal received from the mobile terminal, that is, during the reception time 412, 416. In the present invention, by using the characteristics of the TDD scheme, the uplink and downlink frames up to several times of the TTG (Transmission Transition Gap) or RTG (Receive Transmission Gap) (420) and sets the values of Att1 and 2 of the first and second attenuators during the downlink frame with TDD_CTRL_DL = 1 to control the gain for the received signal (418).

Hereinafter, an automatic gain control method in an orthogonal frequency division multiple access (OFDM) wireless communication system according to a preferred embodiment of the present invention will be described with reference to FIG. 5 of the components of the relay station of the present invention.

5 is a flowchart illustrating automatic gain control in an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention.

First, in step 510, when the attenuation value of the first and second attenuation parts (hereinafter referred to as " Att ") is set, Reg_Att is set to the maximum value. This is to protect the amplification unit against the case where the intensity of the upstream signal received from the antenna is large.

Since the signal transmission time interval and the signal reception time interval exist according to the TDD scheme applied to the present invention, if the condition of TDD_CTRL_UL = 1 is satisfied, In step 514, it is determined that the current signal is in the reception state, and the uplink signal value during the uplink frame measured by the detector 312 (see FIG. 3) is read out by repeating the predetermined number of times, that is, 8 times. In order to increase the accuracy of detection of the strength of the uplink signal received in the signal reception time interval, the signal strength is detected many times during the uplink frame and the average value of the detected signal strength is determined as the signal strength value.

In step 518, the maximum and minimum values of the upward signal values read out in step 514 are repeatedly removed (step 516), and the remaining six values are adopted as valid values to calculate an average value of the six values (step 518) .

The average value calculated in step 518 is compared with the conditions of the control area, i.e., the first and second attenuators 318 and 322, so as to converge to the target value -A dBm. In order to facilitate the control, If the calculated average value is greater than -A dBm to -2 dBm, that is, if the calculated average value is larger than -A-2 dBm, it is set as a lock-in interval (step 522). This is to not interfere with the locked-in state by not calibrating values less than -2 dBm above -A dBm.

Meanwhile, when the maximum range that can be controlled by the amplifying unit and the attenuating unit of the relay station receiving end is set to G, it can be calculated by applying the gain of the amplifying unit to G-Att1-Att2. If the average value is less than -AG dBm (step 532), it is determined that the gain of the transmission line, that is, the amplification part and the attenuation part, Since the strength can not be attained, deterioration of the signal quality may occur. Therefore, the values of Reg_Att 1 and Reg_Att 2 of the first and second attenuation units are set to 0 (step 534). This is because the loss of the first and second attenuation units So that the size of the transmission signal is maximized. If the average value is not less than -AG dBm in step 532, the difference with the target value -A dBm is compared with -2G / 3 (step 536). If the average value is less than -AG dBm, the Att value of the first attenuator is decreased -2 G / 3 and -A dBm, and the Att value of the second attenuation unit is set to -G / 3 (step 538). In step 536, the target value -A dBm Is compared with -2G / 3, and in step 540, the Att value of the first attenuation section is set to 0 and the Att value of the second attenuation section is set to be the subtraction of -2G / 3 from the difference value ( 540 process).

If the condition of TDD_CTRL_UL = 1 is not satisfied in step 512, it is determined in step 524 that the current signal is in a transmission state. In step 524, each Att value of the first and second attenuation units is read, In step 528, each Reg value is initialized to prepare for the measurement of the next uplink signal strength.

8A, when a chip select (CS) signal is activated in a structure in which a chip for performing the AGC function of the present invention is activated as shown in FIG. 6, the uplink frame FIG. 2 is a diagram schematically showing a process of reading an upward signal value by repeating 8 times.

FIG. 8B is a diagram illustrating an example in which the upper part of the first and second attenuation parts is read through the process of comparing the average value of the upward signal calculated by reading the upward signal value eight times repeatedly during the uplink frame measured by the detection part, (Steps 522, 534, 538, and 540, see FIG.

9 is a graph of input / output measurement results in an AGC in an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention. As shown in FIG. 9, when the automatic gain control scheme according to the present invention is applied, it is shown that the intensity of a received signal is controlled without deteriorating the quality of input / output transmission signals having various signal intensities.

As described above, the operation of the scheduling method and apparatus in the cellular system using the wireline RS according to the embodiment of the present invention can be performed. While the present invention has been described with respect to the specific embodiments, And can be practiced without departing from the scope of the present invention. Accordingly, the scope of the present invention should not be limited by the illustrated embodiments, but should be determined by equivalents of the claims and the claims.

1 is a block diagram schematically showing an apparatus for performing automatic gain control in a RoF system using a conventional time division scheme

2 is a diagram illustrating a structure of a transmission frame transmitted / received in a RoF system using a conventional time division scheme

3 is a block diagram of a receiving end of a relay station that performs automatic gain control in an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating a time structure of uplink and downlink signal transmission frames in signal transmission in an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention.

5 is a flowchart illustrating automatic gain control in an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention.

6 is a detailed block diagram of an AGC in an automatic gain control in a relay station of an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention.

FIG. 7 is a block diagram illustrating an automatic gain control in a relay station of an orthogonal frequency division multiple access (OFDM) wireless communication system according to an exemplary embodiment of the present invention. Referring to FIG. 7, the AGC integrated circuit includes a resistance and a transistor, )

FIG. 8A is a diagram illustrating a structure in which a chip for performing the AGC function of the present invention is designed. When a chip select (CS) signal is activated, the uplink signal value is repeated eight times during the uplink frame measured by the detector, Drawings outlining the process of shipment

8B is a view schematically showing a process of setting values of Att of the first and second attenuation units by comparing and setting the average value of the upstream signals and the set range of the measured values,

9 is a graph showing input / output measurement results in an AGC in an orthogonal frequency division multiple access (OFDM) wireless communication system according to an embodiment of the present invention.

Claims (12)

An automatic gain control apparatus for an uplink signal in a radio communication system of an orthogonal frequency division multiple access scheme using a time division scheme in which a signal transmission time and a signal reception time exist, A first attenuator and second attenuators for controlling attenuation of an upstream signal received during the signal reception time, And a controller for receiving a signal output from the first and second attenuators from an RF (Radio Frequency) signal separator to repeatedly measure an intensity value of an up signal at a predetermined number of times, To-be- And generating intensity values for the received uplink signal by repeatedly measuring intensity values of the uplink signals received in a predetermined number of times during the signal reception time, Calculating a mean value by using at least one residual value obtained by removing a maximum value and a minimum value among the intensity values of the received upstream signal and outputting a comparison result between the calculated average value and a preset target value at the first and second attenuation units And a controller for controlling the setting of the attenuation values, Wherein, When the calculated average value is smaller than a value obtained by subtracting the maximum settable range G dBm of the first and second attenuators from the target value -A dBm of the first and second attenuators, Respectively, When the calculated average value is greater than or equal to the target value -A dBm of the first and second attenuation portions minus the maximum settable range G dBm of the first and second attenuation portions, -A dBm is compared with -2G / 3, and as a result of the comparison, if the difference is smaller than -2G / 3, the attenuation value of the first attenuation portion is set to a value obtained by adding the difference to -2G / 3 And the attenuation value of the second attenuator is set to -G / 3. The apparatus of claim 1, wherein the attenuation value of the second attenuator is -G / 3. The method according to claim 1, Further comprising a low noise amplifying unit for performing low noise amplification on the received uplink signal during the signal reception time. The apparatus according to claim 1, A peak detector for measuring an intensity value of the uplink signal, And an analog / digital switching unit for converting the repeated measured uplink signal strength value into a digital value. The apparatus according to claim 1, wherein the first attenuation portion is located at a front end of the first attenuation portion and the second attenuation portion is set to be larger than the second attenuation portion, (Automatic gain control apparatus for uplink signal in a multiple access wireless communication system). The apparatus of claim 3, wherein the peak detector comprises: And generating an intensity value for the received uplink signal by repeatedly measuring the intensity value of the received uplink signal by a predetermined number of times during the signal reception time and calculating an average of the generated intensity values, (Automatic gain control apparatus for uplink signal in a multiple access wireless communication system). A method for automatic gain control of an uplink signal in a wireless communication system using an orthogonal frequency division multiple access scheme using a time division scheme in which a signal transmission time and a signal reception time exist, Setting the attenuation values of the first and second attenuators to be maximized; Generating strength values for the received uplink signal by repeatedly measuring strength values of the uplink signals received in a predetermined number of times during the signal reception time; Calculating an average value using at least one residual value from which the maximum and minimum values of the received uplink signal are removed, And controlling the setting of the attenuation values based on a comparison result between the calculated average value and a preset target value in the first and second attenuation units, The step of controlling the setting of the attenuation values comprises: When the calculated average value is smaller than a value obtained by subtracting the maximum settable range G dBm of the first and second attenuators from the target value -A dBm of the first and second attenuators, And a step of, When the calculated average value is greater than or equal to the target value -A dBm of the first and second attenuation portions minus the maximum settable range G dBm of the first and second attenuation portions, Comparing the difference between -A dBm and -2G / 3, If the difference is less than -2G / 3, the attenuation value of the first attenuation unit is set to -2G / 3 plus the difference, and the attenuation value of the second attenuation unit is set to -G / 3 The method comprising the steps of: determining a gain of the uplink signal based on the gain of the uplink signal in the orthogonal frequency division multiple access (OFDMA) wireless communication system. delete 7. The method of claim 6, wherein the step of controlling the setting of the attenuation values comprises: When the calculated average value is greater than a value obtained by subtracting 2 from the target value -A dBm of the first and second attenuators, a lock-in interval is set during the signal reception time, Wherein the correction is not performed in the orthogonal frequency division multiple access (OFDM) wireless communication system. delete The method according to claim 6, Setting the attenuation value of the first attenuation unit to 0 and setting the attenuation value of the second attenuation unit minus -2G / 3 from the difference when the difference is equal to or higher than -2G / 3 Wherein the uplink signal is transmitted to a mobile station in a radio communication system of an orthogonal frequency division multiple access scheme. The method according to claim 6, Further comprising the steps of: reading the attenuation values of the first and second attenuation units during the signal transmission time, setting each of the attenuation values read to a maximum value, and performing initialization of the attenuation values Wherein the uplink signal is transmitted to a mobile station in a radio communication system of an orthogonal frequency division multiple access system. The method according to claim 6, Wherein it is determined whether the current time is one of the signal transmission time and the signal reception time according to whether or not the condition of TDD_CTRL_UL = 1 is satisfied, which is set in advance, in the radio communication system of the orthogonal frequency division multiple access A method for automatic gain control of a signal.

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