KR20070081381A - Apparatus and method of automatic gain control in a wireless communication system by use of orthogonal frequency division multiple access system - Google Patents

Abstract

An automatic gain control apparatus and an automatic gain control method in an orthogonal frequency division multiple access wireless communication system are provided to maintain a constant intensity of a receiving signal in a signal processing side with respect to a change of time area of a channel. An automatic gain control apparatus in an orthogonal frequency division multiple access wireless communication system includes a gain amplifier(421), an analog/digital converter(423), a time area power measuring unit(411), a digital gain controller(413), an FFT(Fast Fourier Transformer)(415), a frequency area power measuring unit(417), and a control device. The gain amplifier(421) controls an amplification gain of analog symbols. The analog/digital converter(423) converts the analog symbols into digital signals. The time area power measuring unit(411) accumulates instantaneous power of sampled signals in a time area to output average power for a predetermined time. The digital gain controller(413) controls a gain in a digital area based on outputs of the time area power measuring unit(411) and the frequency area power measuring unit(417). The FFT(415) converts the digital signal into a frequency area signal. The frequency area power measuring unit(417) estimates an average power value. The control device outputs a control signal to control a gain of the gain amplifier(421).

Description

Automatic gain control apparatus and method in wireless communication system of orthogonal frequency division multiple access method {APPARATUS AND METHOD OF AUTOMATIC GAIN CONTROL IN A WIRELESS COMMUNICATION SYSTEM BY USE OF ORTHOGONAL FREQUENCY DIVISION MULTIPLE ACCESS SYSTEM}

1 is a block diagram of a physical layer for transmission and reception in a typical OFDM system,

2 is an internal configuration diagram of a general automatic gain control (AGC) circuit,

3 is a view for explaining a mobile terminal position and signal status in an OFDMA wireless communication system to which a technique such as a smart antenna is applied;

4 is a block diagram of an automatic gain control apparatus in a wireless communication system of an orthogonal frequency division multiplexing method according to an embodiment of the present invention;

5 is a block diagram of an automatic gain control apparatus in a wireless communication system of an orthogonal frequency division multiplexing method according to another embodiment of the present invention;

6 is a frame structure diagram of an OFDMA wireless communication system according to an embodiment of the present invention;

7 is an automatic gain control flowchart in an OFDAM wireless communication system according to an embodiment of the present invention;

8 and 9 are block diagrams of an automatic gain control apparatus in an OFDMA wireless communication system according to another embodiment of the present invention;

10 is a flowchart illustrating an automatic gain control method in an OFDMA wireless communication system according to another embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for automatic gain control of a communication system. In particular, the present invention relates to an automatic gain control to maintain a constant reception signal in an orthogonal frequency division multiple access (OFDMA) wireless communication system. An apparatus and method for performing a control (AGC).

In general, a wireless communication system is a typical mobile communication system based on a voice service. Such wireless communication systems are spurring commercialization due to the development of the communication industry and the increase of user demand for Internet services. However, the wireless communication system mainly developed for the voice service has reached a limit in transmitting more data due to the depletion of data transmission bandwidth and resources. Therefore, in a modern society that requires a system capable of transmitting a large amount of data at a higher speed than voice service, it is difficult to sufficiently accommodate such a requirement with a mobile communication system using a conventional code division multiple access (CDMA) method. Have a problem.

One of the emerging methods to solve this problem is to use Orthogonal Frequency Division Multiplexing (hereinafter, referred to as "OFDM"). The OFDM technique will be described below.

The OFDM method is a method of transmitting data using multiple carriers. A serially inputted symbol string is converted in parallel, and each of them is modulated into a plurality of subcarriers having orthogonality. It is a type of multi-carrier modulation (MCM). In addition to the advantages of being robust to the frequency selective fading, the OFDM scheme has an advantage of maximizing throughput by using a link adaptation scheme.

Meanwhile, a multiple access method based on the OFDM scheme is an OFDMA scheme, and the OFDMA scheme reconfigures some subcarriers of all subcarriers into sub-channels and converts the subchannels into specific subscriber stations ( SS is assigned to a Subscriber Station. Here, the subchannel refers to a channel composed of at least one subcarrier. In the case of using the OFDMA scheme, dynamic resource allocation capable of dynamically allocating a subchannel allocated to a specific subscriber station according to a fading characteristic of a wireless channel is possible, and as the number of subscriber stations increases, That is, as the number of users increases, the 'multiuser diversity gain' increases.

FIG. 1 is a block diagram of a physical layer for transmission and reception in a general OFDM system. In FIG. 1, reference numerals 102 to 107 denote a configuration of a transmitter, and reference numerals 101 to 127 denote a configuration of a receiver. It is shown.

The input bit stream 101 to be transmitted is input to the encoder 102. The encoder 120 encodes the input bit stream 101 according to a predetermined scheme and then outputs it to the serial / parallel converter 103. The serial / parallel converter 103 converts the encoded serial bit stream into parallel data and outputs the parallel data. The serial / parallel converter 103 converts the serial bit stream into a parallel bit stream in order to perform an Inverse Fast Fourier Transform (IFFT). Accordingly, the parallel bit stream output from the serial / parallel converter 103 is input to the inverse fast Fourier transformer 104. In this case, it is assumed that the parallel bit stream is N symbols. The reason for assuming that N symbols are received is because the inverse fast Fourier transformer 104 performs inverse fast Fourier transform of the input streams in units of N.

Accordingly, the inverse fast Fourier transformer 104 converts the symbols in the frequency domain into symbols in the time domain by receiving N symbols received in parallel and transforming the symbols to be transmitted. The symbols converted into the time domain are input to the parallel / serial converter 105. The parallel / serial converter 105 converts and outputs N time-domain symbols input in parallel into a serial, sequential N bit stream. As described above, the N bit streams sequentially output are referred to as " OFDM symbols "

The OFDM symbol is input to a Cyclic Prefix Adder 106. The CP adder 106 copies a predetermined number of bits back from the last bit of the input OFDM symbol and inserts it before the first bit of the OFDM symbol. The reason for adding the cyclic prefix symbol is to remove the influence of the multipath channel. The OFDM symbol to which the CP is added is input to the digital-to-analog converter 107. The digital-analog converter 107 then converts the input digital symbols into analog symbols and sends them to the receiver.

The analog symbols transmitted as described above are input to the receiver via a predetermined channel 110 having multiple paths. Then, the configuration and operation of the receiver will be described.

The analog-to-digital converter 121 of the receiver converts the analog signal received through the channel 110 into a digital signal. As such, the signals converted into digital signals by the analog-to-digital converter 121 are input to the CP remover 122. The CP remover 122 removes cyclic prefixes, ie, cyclic prefix symbols, contaminated by the effect of multipath. The signal from which the CPs are removed in the CP remover 122 is a serial signal. Accordingly, the signal from which the CPs are removed is input to the serial / parallel converter 123 for a Fast Fourier Transform (FFT). The serial / parallel converter 123 converts the serially input symbols into N units in parallel and outputs them.

As described above, the serially converted symbols are output in parallel by N units because the inverse fast Fourier transform is performed in N units on the transmitting side. Accordingly, the fast Fourier transformer 124 receives N parallel data and converts the signals into fast Fourier transforms. That is, the fast Fourier transformer 124 converts symbols in the time domain into symbols in the frequency domain. The symbols converted into the frequency domain are input to an equalizer 125. The equalizer 125 is converted into a frequency domain and cancels and outputs the influence of the channel 110 from the input symbols. The symbols output from the equalizer 125 convert the parallel input symbols back to serial symbols in the parallel / serial converter 126 and output them. Accordingly, the unit of symbols converted in series in the parallel / serial converter 126 is N symbols. The symbols serially converted into N units are finally input to the decoder 127 and decoded. The decoder 127 decodes the input symbols and outputs an output bit stream 128.

FIG. 2 is an internal configuration diagram of a general automatic gain control (AGC) circuit. As shown in FIG. 2, the ADC for a change in the time domain of a channel is illustrated in the design of a transmitter / receiver using the OFDMA scheme as described above. The front end of the (Analog to Digital Converter) 121 should be provided with an automatic gain control loop (AGC loop) to keep the received signal strength constant. The AGC circuit includes an ADC 210, a power meter 220, an accumulator 1 230, a loop filter 240, a log map table 250, an accumulator 2 260, an AGC interface 270 and a variable gain. A circuit including an amplifier 200.

In the conventional AGC loop, as shown in FIG. 2, the power meter 220 receives a sampled signal in the time domain from the ADC 210 to accumulate instantaneous power of the sampled signal, and then, for a predetermined time, Measure the average power over. The accumulator 1 230 accumulates the average power measured by the power meter 220 for a predetermined time, and the loop filter 240 loop filters the accumulated average power. In addition, the log map table 250 compares the average power output from the loop filter 240 with a predetermined ADC input reference power value and outputs a corresponding comparison value, and the accumulator 2 260 outputs the comparison value. Accumulate continuously. The AGC interface 270 adjusts the gain of the variable gain amplifier 200 of the analog stage by using the accumulated comparison value. At this time, the AGC interface 270 converts the digital value obtained from the accumulated comparison value into a form that the variable gain amplifier 200 can receive.

In general, an OFDMA wireless communication system has a wireless communication environment in which transmission power varies according to subchannel allocation, and when a signal is received through a channel, a change in reception power in the time domain is not only a change in channel but also a transmission power. It will cover all of the differences. However, in order to recover the information contained in the signal magnitude in the frequency domain, the AGC loop must operate to compensate only for the channel change.

In this regard, in the OFDMA wireless communication system, since the average power at the transmitting end is probabilistically constant during data transmission, when the average power is calculated in the time domain at the receiving end, the difference from the reference power reflects the channel change. However, in the OFDMA scheme, since the transmission power from the transmitter is not constant on the basis of the subchannel allocation, when the receiver obtains the average power as shown in FIG. 2, a problem arises in which not only the channel change but also the difference in transmission power is reflected. This problem has an adverse effect on the process of recovering the information contained in the signal size of the frequency domain at the receiving end.

In particular, in the OFDMA scheme, information is carried on a signal amplitude in the frequency domain. In this case, the power of each subcarrier in the frequency domain is constant rather than maintaining the power input to the ADC 210 as in the conventional art. It is necessary to keep the effective bit-precision of each subcarrier constant.

On the other hand, the position and signal state of the mobile terminal in an OFDMA wireless communication system to which a technique such as a smart antenna will be described with reference to FIG.

Referring to FIG. 3, the first mobile terminal 310 is boosted in a specific frequency band by beam forming in an OFDMA wireless communication system to which a technique such as a smart antenna is applied. In order to apply this in a system using multiple frequency bands such as OFDMA, beamforming is applied so that all users can access at the beginning of the frame (the part that is broadcast to all terminals such as DL-MAP except the preamble). That is, since the same area must be decoded in order to obtain information of all terminal current frames, beamforming is not applied, and beamforming is applied to each user in an area where general data is transmitted. In this case, if the power boosting factor is not removed by the gain control by the beam forming, the signal dynamic range that the signal processor (not shown in the figure) needs to process becomes wider, which increases hardware complexity.

In this case, a pilot signal may be transmitted only to an area where data is actually transmitted with respect to an OFDM symbol to which beamforming is applied, and thus a symbol having no actual signal may exist, and a second movement existing at a null position of beamforming In some cases, the terminal 320 may not transmit a valid signal. In this case, a signal section capable of estimating a change in channel power is limited to a section in which beamforming is not applied. In this case, there is a problem that the automatic gain loop has an abnormal operation.

Accordingly, an object of the present invention is to provide a method for processing a received signal in terms of signal processing with respect to a change in the time domain of a channel in a transceiver design, when the beamforming antenna technique is applied for efficient channel use when the frequency domain is divided for each user as in the OFDMA scheme. An automatic gain control apparatus and method for maintaining a constant intensity is provided.

Another object of the present invention is to provide a gain adjusting apparatus and method for accurately reflecting a channel change in a gain adjustment in consideration of a difference in transmission power at a receiving end of an OFDAM wireless communication system.

Another object of the present invention is to provide an automatic gain control apparatus and method for adjusting automatic gain of an OFDMA system to which a beamforming antenna such as a smart antenna is applied.

Another object of the present invention is to provide an automatic gain control apparatus and method for performing power estimation in a frequency domain and a time domain at a receiving end of an OFDMA wireless communication system.

It is still another object of the present invention to provide an automatic gain control apparatus and method capable of optimizing the performance of an OFDMA receiver by compensating for a channel change in a time domain in a system in which power boosting of a specific frequency band depends on transmission power, beamforming, and the like. In providing.

Another object of the present invention includes processing for exceptional cases in which a signal for estimating channel power does not exist when a beamforming antenna technique is applied for efficient channel use when the frequency domain is divided for each user as in the OFDMA scheme. Accordingly, an object of the present invention is to provide an automatic gain control apparatus and method for maintaining a constant intensity of a received signal in terms of signal processing with respect to a change in a time domain of a channel.

It is still another object of the present invention to provide an automatic gain control apparatus and method for optimizing the performance of an OFDMA receiver by compensating for a channel change in a time domain in a system in which there may be no signal to estimate a channel state.

In an orthogonal frequency division multiplexing wireless communication system according to an embodiment of the present invention, the automatic gain control apparatus is an automatic gain control apparatus for a wireless mobile terminal in an orthogonal frequency division multiple access system. A gain amplifier, an analog-digital converter for converting the received analog symbols into a digital signal, and an average power for a predetermined time by accumulating instantaneous power of the sampled signal by receiving a sampled signal in a time domain from the analog-digital converter. A time domain power meter for outputting a digital gain, a digital gain regulator for adjusting the gain in a digital domain with the output of the time domain power meter and a frequency domain power meter, and a fast Fourier transforming the digital signal into a signal in a frequency domain With a converter, A frequency domain power meter that detects a subcarrier assigned to the user in the frequency domain and estimates an average power value, and outputs a control signal for adjusting the gain of the gain amplifier by comparing the estimated average power value with a reference power value And control means.

In an orthogonal frequency division multiplexing wireless communication system according to an embodiment of the present invention, the automatic gain control method is an automatic gain control method of a wireless mobile terminal in an orthogonal frequency division multiple access system. A process of converting the received analog symbols into a digital signal, measuring and outputting the power of the sample data of the digital signal in symbol units in the time domain, and power and frequency of the symbol units measured in the time domain. Adjusting and outputting the gain in the digital domain by the symbol unit power measured in the domain, converting the digital signal into a signal in the frequency domain, and detecting the subcarriers assigned to the user in the frequency domain to average power Estimating a value, and calculating the estimated average power value. It characterized in that it comprises the step of outputting a control signal for adjusting the gain of the gain amplifier as compared with the power values.

In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted when it is determined that the detailed description may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

An automatic gain control apparatus in a wireless communication system of an orthogonal frequency division multiplexing method according to an embodiment of the present invention is illustrated in FIG. 4. An automatic gain control apparatus according to an embodiment of the present invention will be described with reference to FIG. 4.

Referring to FIG. 4, the automatic gain control apparatus is largely divided into a digital gain loop 410 and an analog gain loop 420.

The digital gain loop 410 is composed of an ADC 423, a time domain power meter 411, a digital gain regulator 413, an FFT 415, and a frequency domain power meter 417.

The analog gain loop 420 includes an ADC 423, a loop filter 431, a log map table 431, an accumulator 427, an AGC interface 425, and a variable gain amplifier 421.

In the digital gain loop 410, the ADC 423 converts the received analog symbols into time sample data and outputs them to the time domain power meter 411. The sample data becomes an OFDM symbol with CP added thereto, and the OFDM symbol is recovered by a CP canceller (not shown).

)을 출력한다. The time domain power meter 411 receives a sampled signal in the time domain from the analog-to-digital converter and accumulates instantaneous power of the sampled signal to filter the average power for a predetermined time with the digital gain adjuster 413 and a loop filter. Output to 431, respectively. At this time, the time domain power meter 411 measures the power measured at the first symbol of the downlink frame (

)

The digital gain adjuster 413 adjusts the gain in the digital domain by the output of the time domain power meter 411 and the frequency domain power meter 417, which will be described later, and outputs the gain to the FFT 415.

The FFT 415 receives N parallel data, converts the signals into fast Fourier transforms, and outputs the signals to the frequency power meter 417. That is, the FFT 415 converts symbols in the time domain into symbols in the frequency domain.

)을 출력하고, 수신된 프레임 내의 빔 포밍이 적용되어 있는 심볼 중 현재 이동 단말에 할당된 데이터 영역에서 측정한 전력(

)을 출력한다.The frequency domain power meter 417 detects a subcarrier assigned to the user in the frequency domain, estimates an average power value, and outputs the average power value to the loop filter 431. In this case, the frequency power meter 417 measures the power measured in the last symbol to which beamforming is not applied in the received frame.

) And the power measured in the data area allocated to the current mobile terminal among the symbols to which beamforming in the received frame is applied

)

The loop filter 431 in the analog gain loop 420 receives and loop-filters the power output from the time-domain power meter 411 and the frequency-domain power meter 417, and then loop-filters the log map table 429. Output

The log map table 429 compares the average power output from the loop filter 431 with an ADC input reference power value and outputs a corresponding comparison value, and then the accumulator 427 outputs the comparison value at an arbitrary time. Accumulate while. The AGC interface 425 adjusts the gain of the variable gain amplifier 421 of the analog stage using the accumulated comparison value. At this time, the AGC interface 425 converts the digital value obtained from the accumulated comparison value into a form that the variable gain amplifier 421 receives. Control means for generating a control signal for adjusting the gain of the variable gain amplifier 421 includes a loop filter 431, a log map table 429, an accumulator 427, and an AGC interface 425 .

Preamble power estimation in the automatic gain control apparatus as shown in FIG. 4 is possible in both the time domain and the frequency domain, and in the presence of interference, it is more accurate to estimate only the subcarriers allocated to the user in the frequency domain. To provide.

In the wireless communication system of the orthogonal frequency division multiplexing method according to another embodiment of the present invention, an automatic gain control apparatus is shown in FIG. An automatic gain control apparatus according to another embodiment of the present invention will be described with reference to FIG. 5.

Referring to FIG. 5, the automatic gain control apparatus is largely divided into a digital gain loop 510 and an analog gain loop 520.

The digital gain loop 510 is composed of an ADC 523, a digital gain adjuster 513, an FFT 515, and a frequency domain power meter 517. In FIG. 5, the time-domain power meter 411 is deleted.

The analog gain loop 520 includes an ADC 523, a loop filter 531, a log map table 529, an accumulator 527, an AGC interface 525, and a variable gain amplifier 521. This is the same as in FIG.

In the digital gain loop 510, the ADC 523 converts the received analog symbols into time sample data and outputs them to the digital gain regulator 513. The sample data becomes an OFDM symbol with CP added thereto, and the OFDM symbol is recovered by a CP canceller (not shown).

The digital gain adjuster 513 adjusts the gain in the digital domain with the output of the ADC 523 and outputs it to the FFT 515.

The FFT 515 receives N parallel data, converts the signals into fast Fourier transforms, and outputs the signals to the frequency power meter 517. That is, the FFT 515 converts symbols in the time domain into symbols in the frequency domain.

)을 측정하여 출력하고, 수신된 프레임 내의 빔 포밍이 적용되어 있는 심볼 중 현재 이동 단말에 할당된 데이터 영역에서 측정한 전력(

)을 출력하고, 하향 프레임의 첫 번째 심볼에서 측정한 전력(

)을 출력한다. The frequency domain power meter 517 measures the power of the frequency domain output from the FFT 515 in units of symbols and outputs the power to the loop filter 531. In this case, the frequency domain power meter 517 measures the power measured at the last symbol to which beamforming is not applied in the received frame.

) And the power measured in the data area currently allocated to the mobile terminal among the symbols to which beamforming is applied in the received frame

) And the power measured at the first symbol of the downstream frame (

)

,

,

)을 수신하여 루프 필터링한 후, 로그 맵 테이블(529)로 출력한다.The loop filter 531 in the analog gain loop 520 may output powers output from the frequency domain power meter 517.

,

,

), Loop filtering, and outputting the result to the log map table 529.

The log map table 529 compares the average power output from the loop filter 531 with an ADC input reference power value and outputs a corresponding comparison value, and the accumulator 527 outputs the comparison value for a predetermined time. Accumulate. The AGC interface 525 adjusts the gain of the variable gain amplifier 521 of the analog stage using the accumulated comparison value. At this time, the AGC interface 525 converts the digital value obtained from the accumulated comparison value into a form that the variable gain amplifier 521 receives.

In the general automatic gain control device, the power estimation in the preamble can be directly adjusted through the variable gain amplifier 521 of the analog stage, but it takes time for the variable gain amplifier 521 to be changed, and then the signal processor 530 after the channel estimator, etc. In order to give the same gain to the input signal, the digital gain adjuster 513 is used in the present invention. The digital gain adjuster 513 can come before or after the FFT 515, which can reduce implementation complexity depending on the location of the buffer to compensate for power estimation delays according to the FFT structure. Channel gain estimation using the pilot in the frequency domain is all behind the digital gain adjuster 513. Power estimation performed in the last symbol is performed only with the pilot of the allocated area.

The input to the variable gain amplifier 521 is performed once per frame with the gain estimated at the first preamble, the gain estimated at the last symbol before beamforming, and the gain estimated at the last symbol, and the digital gain adjuster 513 performs the preamble. The preamble is applied with the gain estimated at, and the first symbol is applied with the gain estimated at the first symbol to which beamforming is applied.

6 illustrates a frame structure in an OFDMA wireless communication system according to an embodiment of the present invention. An OFDMA frame structure to which beamforming is applied will be described with reference to FIG. 6.

를 측정한다. 프리앰블에서의 전력은 상향 구간동안 채널 변화에 따라 기준 전력(Reference Power)에서

만큼 차이가 나게 된다. 여기서

는 하향 프레임의 첫 번째 심볼에서 측정한 전력을 나타낸다.Referring to FIG. 6, if G is the power controlled analog gain in the previous frame, the preamble 601

Measure The power in the preamble is changed from the reference power according to the channel change during the up period.

As much as the difference. here

Denotes the power measured at the first symbol of the downlink frame.

를 측정한다. 상기

는 프레임에서 빔 포밍이 적용되지 않은 마지막 심볼에서 측정한 전력으로 정의한다.In the last symbol 603 where beamforming is not applied, power

Measure remind

Is defined as the power measured at the last symbol without beamforming in the frame.

를 측정한다. 상기

는 프레임에서 빔 포밍이 적용되는 첫 번째 심볼에서 측정한 전력으로 정의한다.The symbol 605 with the first beamforming applied is the power

Measure remind

Is defined as the power measured in the first symbol to which beamforming is applied in a frame.

를 측정한다. 상기

는 프레임 내에 빔 포밍이 적용되어 있는 심볼 중 현재 단말에 할당된 데이터 영역에서 측정한 전력으로 정의한다.In the symbol 607 to which beamforming is applied as a pilot of the data allocation interval, power is applied.

Measure remind

Is defined as the power measured in the data area currently allocated to the UE among symbols to which beamforming is applied in a frame.

7 is a flowchart illustrating an automatic gain control method in an OFDAM wireless communication system according to an exemplary embodiment of the present invention. How the respective power estimation is applied using the frame structure of FIG. 6 will be described with reference to the flowchart of FIG. 7.

를 측정하고, 도 5의 주파수 전력 측정기(517)는 프리앰블(601)의 주파수 영역에서 전력

를 측정한다. 프리앰블(601)에서의 전력은 상향 구간동안 채널 변화에 따라 기준 전력에서

만큼 차이가 나게 된다. 이에 대해 디지털 이득 조정기(413)는 703 단계에서 상기 측정된

로 이득 제어를 수행한다. 이득 제어를 수행하면, 이후 이득 조정을 행하지 않는다고 가정할 때

만큼 채널 변화에 따른 전력 차이를 측정할 수 있다. First, assume that the power controlled analog gain in the previous frame is G. In operation 701, the time domain power meter 411 of FIG. 4 performs power in the time domain of the preamble 601.

5, the frequency power meter 517 of FIG. 5 performs power in the frequency domain of the preamble 601.

Measure The power in the preamble 601 is changed from the reference power according to the channel change during the up period.

As much as the difference. In contrast, the digital gain adjuster 413 measures the measured signal at step 703.

Gain control. When performing gain control, it is assumed that no gain adjustment is performed later.

The power difference according to the channel change can be measured.

However, when gain adjustment is performed after the gain control is performed in step 703, the frequency domain power meter 417 identifies the beam forming region in step 705. This finds the beamforming region from the subchannel allocation information from the MAP decoder (not shown in the figure).

를 측정한다. 이후, 주파수 영역 전력 측정기(417)는 709 단계에서 빔 형성이 적용되는 첫 번째 심볼(보통 빔 형성 구간을 위한 새로운 프리앰블이 올 수 있음)에서 심볼 전력

을 측정한다. 이때, 빔 형성이 적용되는 첫 번째 심볼에서 해당 주파수 영역만의 파일럿만으로 전력 추정을 할 수 있으며, 빔 형성에 따른 전력 boosting은 인접 심볼 간의 전력 변화를 무시할 때

-

로 추정 가능하다. When the beamforming region is found, the frequency domain power meter 417 determines the last symbol other than the beamforming in operation 707.

Measure Next, the frequency domain power meter 417 determines the symbol power at the first symbol to which beamforming is applied (usually a new preamble for the beamforming interval may come) in step 709.

Measure In this case, the power estimation can be performed only by the pilot of the corresponding frequency domain in the first symbol to which the beam shaping is applied.

-

It can be estimated as

만큼 다시 이득 조정을 수행한다. 그러면, 빔 형성에 의해 boosting된 구간도 빔 형성이 적용되지 않는 구간과 마찬가지의 동작점에서 동작 가능하다. 이후 상기 주파수 영역 전력 측정기(417)는 713 단계에서 하향 프레임의 마지막에서 할당된 구간의 파일럿만으로 전력 추정을 하면 AAS 구간 내에서 채널 이득 변화를

로 얻을 수 있다. 즉, 상기 주파수 영역 전력 측정기(417)는 프레임 내의 빔 포밍이 적용되어 있는 심볼 중 현재 단말에 할당된 데이터 영역에서 측정한 전력을 측정한다.Herein, in step 711, the digital gain adjuster 413 adjusts the operating area of the actual signal processing.

Perform gain adjustment again. Then, the section boosted by the beam forming can be operated at the same operating point as the section to which the beam forming is not applied. Then, the frequency domain power meter 417 calculates the channel gain change in the AAS section when power estimation is performed using only the pilot of the allocated section at the end of the downlink frame in step 713.

You can get That is, the frequency domain power meter 417 measures the power measured in the data region currently allocated to the terminal among the symbols to which beamforming is applied in the frame.

+

+

- (

-

) =

+

+

만큼 이득 조정을 수행하게 되고, 빔 형성 부분의 채널 이득은 디지털 이득 조정으로 처리해야 한다. In this case, the analog gain adjustment only compensates for the change in the channel, and the power change according to the beam formation must be processed by the digital gain adjustment of the signal processor 430 to obtain a desired signal-noise ratio even in a section where the beam formation is not applied. That is, in step 715, the variable gain amplifier 421 of the analog stage has (final power gain)-(beam shaping gain) from G adjusted in all frames last.

+

+

-(

-

) =

+

+

As long as the gain adjustment is performed, the channel gain of the beam forming portion must be processed by digital gain adjustment.

Meanwhile, an automatic gain control apparatus in an OFDMA wireless communication system according to another embodiment of the present invention will be described with reference to FIGS. 8 and 9. The automatic gain control apparatus of FIGS. 8 and 9 is characterized in that a controller is added in exceptional cases in the automatic gain control apparatus of FIGS. 4 and 5.

+

로 제어를 한다. 또한, 상기 예외적 경우 제어기(810)는 빔 형성이 적용된 영역에 실제 데이터 전송 영역이 할당되지 않을 경우에

=0(dB) ,

=0(dB)로 설정한다.In the exceptional case, it is assumed that the controller 810 receives the control channel MAP information from the MAP decoder. In the exceptional case, the controller 810 stops digital gain adjustment of the beam shaping application section when the actual data transmission area is not allocated to the beam shaping region, which is an exception.

+

To control. Also, in the exceptional case, the controller 810 may not allocate a real data transmission area to an area to which beamforming is applied.

= 0 (dB),

Set to 0 (dB).

Therefore, in the exceptional case, the controller 810 is added to solve the problem that the channel power estimation is impossible for this section because no valid reception signal exists when the mobile terminal is located in the null of the beamforming system. .

을 측정한다. 이때, 빔 형성이 적용되는 첫 번째 심볼에서 해당 주파수 영역만의 파일럿만으로 전력 추정을 할 수 있으며, 빔 형성에 따른 전력 boosting은 인접 심볼 간의 전력 변화를 무시할 때

-

로 추정 가능하다. 이때, 도 8의 자동 이득 제어 장치의 경우에는 첫 심볼에 이동 단말에 할당된 데이터 버스트가 없을 경우 파일럿이 존재하지 않은 경우가 발생하므로 이와 같이 예외적인 경우에 대해서는 예외적 경우 제어기(810)가 이후 빔 형성 적용 구간에서 해야 하는 이득 조정은 신호 처리부(820)의 이후 동작을 보장하기 위해 조정하지 않도록 제어한다.In step 709 of FIG. 7 described above, the frequency domain power meter 417 performs symbol power at the first symbol to which beamforming is applied (usually, an AAS preamble may come) in step 709.

Measure In this case, the power estimation can be performed only by the pilot of the corresponding frequency domain in the first symbol to which the beam shaping is applied.

-

It can be estimated as In this case, in the automatic gain control apparatus of FIG. 8, when there is no data burst allocated to the mobile terminal in the first symbol, a pilot does not exist. Thus, in this exceptional case, the controller 810 subsequently beams. The gain adjustment to be made in the shaping application section is controlled so as not to adjust to ensure the subsequent operation of the signal processor 820.

만큼 다시 이득 조정을 수행하면, 빔 형성에 의해 boosting된 구간도 빔 형성이 적용되지 않는 구간과 마찬가지의 동작점에서 동작 가능하다. 이후 하향 frame의 할당된 데이터 전송 영역의 파일럿만으로 전력 추정을 하면 AAS구간내에서 채널 이득 변화를

로 얻을 수 있다.To fit the operating range of the actual signal processing in the beam shaping application section

If the gain adjustment is performed again, the section boosted by the beamforming can be operated at the same operating point as the section without beamforming. Subsequently, when power estimation is performed only with the pilot of the allocated data transmission region of the downlink frame, the channel gain change is performed within the AAS period.

You can get

+

+

- (

-

) =

+

+

만큼 이득 조정을 수행 하게 되고, 빔 형성 부분의 채널 이득은 디지털 이득 조정으로 처리해야 한다. 그러나 이동 단말에 데이터 버스트(burst)가 전혀 할당되지 않는 경우에 대해서는 채널 전력을 추정할 수 없게 되며, 이때, 예외적 경우 제어기(810)는

+

만으로 아날로그 이득을 조정한다. In addition, the variable gain amplifier 421 of the analog stage is (final power gain)-(beam shaping gain) from G finally adjusted in the previous frame in step 715 =

+

+

-(

-

) =

+

+

Gain adjustment is performed as much as possible, and the channel gain of the beam forming portion must be processed by digital gain adjustment. However, channel power cannot be estimated for a case in which no data burst is allocated to the mobile terminal. In this case, the controller 810

+

Only adjust analog gain.

All channel gain estimation using the pilot in the frequency domain is performed behind the digital gain adjuster 413. Since the actual pilot may exist only in the data allocation region or throughout the region to which beamforming is applied, the number of symbols located in the second half of the downlink frame in the period where the pilot exists after obtaining the MAP information (in a signal close to the next downlink frame). Channel gain must be estimated by a pilot within the estimated channel gain).

10 is a flowchart illustrating an automatic gain control method in an OFDMA wireless communication system according to another embodiment of the present invention. An operation of the controller in exceptional cases will be described with reference to FIG. 10.

=0(dB) ,

=0(dB)로 설정한다. In the exceptional case, the controller 810 determines whether the frame information is obtained from the subchannel allocation information received from the MAP decoder (not shown) in step 1001. If the frame information is not received, in the exceptional case, the controller 810 remains in a waiting state until receiving the frame information. However, when receiving the frame information, in the exceptional case, the controller 810 determines whether real data is allocated to the beamforming region in step 1003. If real data is allocated to the beamforming region, the flow returns to step 1001. However, if no actual data is allocated to the beam forming area, the controller 810 proceeds to step 1005 in the exceptional case.

= 0 (dB),

Set to 0 (dB).

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

According to the present invention, when a transceiver is designed in an OFDMA wireless communication system to which a beamforming antenna technique is applied, the strength of a received signal may be kept constant in terms of signal processing with respect to a change in a time domain of a channel.

In addition, the present invention can adjust the automatic gain in the OFDMA wireless communication system to which the beamforming antenna technique is applied.

In addition, the present invention can optimize the performance of the OFDMA receiver by compensating for the channel change in the time domain in a system in which power boosting of a specific frequency band exists according to transmission power, beamforming, and the like.

In addition, the present invention relates to the processing of the received signal in terms of signal processing with respect to a change in the time domain of the channel, including processing for exceptional cases in which there is no signal for estimating channel power in an OFDMA wireless communication system to which the beamforming antenna technique is applied. You can keep the strength constant.

In addition, the present invention can optimize the performance of the OFDMA receiver by compensating for the channel change in the time domain in a system where there is no signal to estimate the channel state.

Claims (11)

An automatic gain control apparatus for a wireless mobile terminal in an orthogonal frequency division multiple access system, A gain amplifier for adjusting the amplification gain of the received analog symbols, An analog to digital converter for converting the received analog symbols into digital signals; A time domain power meter which receives the sampled signal in the time domain from the analog-to-digital converter and accumulates instantaneous power of the sampled signal to output an average power for a predetermined time period; A digital gain adjuster configured to output a gain in the digital domain by outputting the time domain power meter and the frequency domain power meter; A fast Fourier transformer for converting the digital signal into a signal in a frequency domain; A frequency domain power meter that detects a subcarrier assigned to the user in the frequency domain and estimates an average power value; And control means for outputting a control signal for adjusting the gain of the gain amplifier by comparing the estimated average power value with a reference power value. The method of claim 1, The time domain power meter, The power measured at the first symbol of the downstream frame with the digital gain regulator and loop filter

Automatic gain control device characterized in that for outputting. The method of claim 1, The frequency domain power meter, The power measured at the last symbol without beamforming in the received frame (

) And the power measured in the data area currently allocated to the mobile terminal among the symbols to which beamforming in the received frame is applied (

) Is a loop filter output. The method of claim 1, As a result of decoding MAP information transmitted from the system, if the actual data transmission area is not allocated to the exceptional beamforming region, the digital gain adjustment of the beamforming application section is stopped, and the analog gain adjustment is performed.

+

Automatic gain control device characterized in that it further comprises a controller in exceptional cases controlled by. The method of claim 1, The control means, A loop filter for filtering the average power value; A log map table that compares the average power value with the reference power value, calculates a digital value for operation control of the gain amplifier, and outputs a comparison value corresponding to the digital value; An accumulator for accumulating the comparison value for a predetermined time; And an interface for converting the accumulated comparison value into the control signal so as to receive the gain amplifier and outputting the control signal. In the automatic gain control method of a wireless mobile terminal in an orthogonal frequency division multiple access system, Adjusting the amplification gain of the received analog symbols; Converting the received analog symbols into digital signals; Measuring and outputting the power of the sample data of the digital signal in symbol units in the time domain; Adjusting and outputting a gain in the digital domain with power of a symbol unit measured in the time domain and power of a symbol unit measured in a frequency domain; Converting the digital signal into a signal in a frequency domain; Estimating an average power value by detecting a subcarrier assigned to a user in the frequency domain; And outputting a control signal for adjusting the gain of a gain amplifier by comparing the estimated average power value with a reference power value. The method of claim 5, The process of outputting the control signal, Filtering the average power value; Calculating a digital value for operation control of the gain amplifier by comparing the average power value with the reference power value and outputting a comparison value corresponding to the digital value; Accumulating the comparison value for a predetermined time; And converting the accumulated comparison value into the control signal so that the gain amplifier can be inputted and outputting the control signal. The method of claim 5, The process of measuring and outputting the power of the sample data of the digital signal in the symbol unit in the time domain, The power measured at the first symbol of the downstream frame with the digital gain regulator and loop filter (

Automatic gain control method characterized in that the output; The method of claim 5, Detecting a subcarrier assigned to the user in the frequency domain and estimating an average power value, The power measured at the last symbol without beamforming in the received frame (

) And the power measured in the data area currently allocated to the mobile terminal among the symbols to which beamforming in the received frame is applied (

) Is output to the loop filter. The method of claim 5, If the actual data transmission area is not allocated to the area where the beamforming applied as an exception is received by receiving the MAP information, the digital gain adjustment of the beamforming application section is stopped.

+

Automatic gain control method characterized in that it further comprises the step of controlling. The method of claim 5, Detecting a subcarrier assigned to the user in the frequency domain and estimating an average power value, Power from preamble

To measure and Measured above

Performing gain control with Identifying a beamforming region when gain adjustment is performed after the gain control; Identifying a beamforming region through the subchannel allocation information received from the MAP decoder; Once the beamforming area is identified, at the last symbol that is not beamforming

To measure and Symbol power at the first symbol to which beamforming is applied

The process of measuring remind

Process of performing gain adjustment as much as, Among the symbols to which beamforming in the frame is applied, power in the data area allocated to the current terminal

), And remind

+

+

Automatic gain control method comprising the step of adjusting the gain.

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