KR20170085378A - Method and Apparatus for Distortion Compensation of Subcarrier in Wireless Communication System Based on Orthogonal Frequency Division Multiplexing - Google Patents

Abstract

A method for compensating distortion of a subcarrier in an OFDM-based wireless communication system and an apparatus therefor are disclosed.
A method for compensating for distortion of a subcarrier in an OFDM-based wireless communication system that extracts an amplitude and a phase of a pilot signal and calculates a distortion compensation value using the extracted amplitude and phase to compensate each of amplitude and phase of the data signal, .

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of compensating distortion of a subcarrier in an OFDM-based wireless communication system, and an apparatus therefor. 2. Description of the Related Art [

The present embodiment relates to a method of compensating distortion of a subcarrier in an OFDM-based wireless communication system and an apparatus therefor.

The contents described in this section merely provide background information on the present embodiment and do not constitute the prior art.

The OFDM scheme, which has recently been used as a method for high-speed data transmission in a wired / wireless channel, is a scheme for transmitting data using a multicarrier. The OFDM scheme performs parallel conversion of symbol streams input in series, And is a type of multi carrier modulation (MCM) that modulates and transmits data to a plurality of subcarriers having mutual orthogonality.

The use of the guard interval and the insertion of the CP (Cyclic Prefix) guard interval have been known in the OFDM scheme, thereby further reducing the adverse effect of the system on multipath and delay spread. In addition, the OFDM scheme has been rapidly developed due to various digital signal processing techniques including Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT).

The OFDM scheme maintains orthogonality among a plurality of subcarriers and transmits the data, thereby achieving optimal transmission efficiency in high-speed data transmission. In addition, it is characterized by high frequency utilization efficiency and strong characteristics against multi-path fading, thereby achieving optimal transmission efficiency in high-speed data transmission. In addition, since the frequency spectrum is superimposed, it is effective in frequency use, strong in frequency selective fading, strong in multipath fading, and has influence of Inter Symbol Interference (ISI) using a guard interval. It is possible to design the equalizer structure in hardware in a simple manner, and it is advantageous in that it is resistant to impulse noise, and thus it is being utilized in a communication system structure.

The multiple access scheme based on the OFDM scheme is an OFDMA scheme. The OFDMA scheme is a scheme in which a plurality of users, that is, a plurality of terminals divide and use subcarriers in one OFDM symbol.

Meanwhile, in a broadband wireless communication system, a transmission signal transmitted by a transmitter is distorted while passing through a wireless channel, and a receiver receives a distorted transmission signal. Also, a problem may occur such that a transmission signal is lost before being transmitted to a receiver due to a problem on a channel or the like, or a transmission signal is distorted and received until a transmission signal of the transmitter is transmitted to the receiver. Accordingly, in the broadband wireless communication system, various alternatives for improving the reception performance of the receiver have been researched and developed.

In this embodiment, in the OFDM-based wireless communication system that extracts the amplitude and phase of the pilot signal, calculates the distortion compensation value using the extracted amplitude and phase, and compensates for each of the amplitude and phase of the data signal, And a device therefor.

According to an aspect of the present invention, there is provided an apparatus for compensating for distortion of a data subcarrier channel included in an Orthogonal Frequency Division Multiplexing (OFDM) symbol, the apparatus comprising: means for obtaining an I / Q signal for a data signal from the data subcarrier channel, A first coordinate system conversion unit for extracting a first amplitude and a first phase for the data subcarrier channel based on the polar coordinates; Acquires an I / Q signal from a pilot channel included in the OFDM symbol to check a sequence of a pilot signal, and extracts an I / Q signal corresponding to a predetermined sequence value of the sequence of the pilot signal A pilot sequence verifying unit; A second coordinate system conversion unit for converting an I / Q signal corresponding to the predetermined sequence value to polar coordinates, and extracting a second amplitude and a second phase for the pilot channel based on the polar coordinates; A compensation value calculation unit for calculating a distortion compensation value based on the second amplitude and the second phase; A distortion compensator for compensating for the first amplitude and the first phase based on the distortion compensation value; And a third coordinate system conversion unit for converting the first amplitude and the first phase compensated for distortion into orthogonal coordinates and demodulating the first amplitude and the first phase.

According to another aspect of the present invention, there is provided a method of compensating for distortion of a data subcarrier channel included in an OFDM symbol, the method comprising: obtaining an I / Q signal for a data signal from the data subcarrier channel, A first coordinate system transforming step of extracting a first amplitude and a first phase of the data subcarrier channel based on the first amplitude and the first phase; Acquires an I / Q signal from a pilot channel included in the OFDM symbol to check a sequence of a pilot signal, and extracts an I / Q signal corresponding to a predetermined sequence value of the sequence of the pilot signal A pilot sequence confirmation process; A second coordinate system conversion step of converting an I / Q signal corresponding to the predetermined sequence value into polar coordinates, and extracting a second amplitude and a second phase with respect to the pilot channel based on the polar coordinates; A compensation value calculation step of calculating a distortion compensation value based on the second amplitude and the second phase; A distortion compensating step of compensating the first amplitude and the first phase based on the distortion compensation value; And a third coordinate system transforming step of transforming the distortion-compensated first amplitude and the first phase to orthogonal coordinates and demodulating the transformed signal.

As described above, according to the present embodiment, the distortion of the data signal of the subcarrier channel is compensated for each of the amplitude and the phase, thereby remarkably improving the distortion of the data signal.

It is possible to ensure high-quality OFDM communication performance by accurately compensating for the distortion of the data signal of the subcarrier channel.

1 is a block diagram schematically showing an OFDM-based wireless communication system according to the present embodiment.
2 is a block diagram schematically showing an equalizer included in a receiver according to the present embodiment.
3 is a flowchart for explaining a method of compensating distortion of a subcarrier channel in an equalizer according to the present embodiment.
4 is an exemplary diagram for explaining the operation of the equalizer according to the present embodiment.
5 is an exemplary diagram for explaining the operation of the coordinate system converting unit included in the equalizer according to the present embodiment.
6 is an exemplary diagram illustrating a data subcarrier channel and a pilot channel included in an OFDM symbol according to the present embodiment.
7 is an exemplary diagram showing a signal in which distortion is compensated in the equalizer according to the present embodiment.

Hereinafter, the present embodiment will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically showing an OFDM-based wireless communication system according to the present embodiment.

An orthogonal frequency division multiplexing (OFDM) based wireless communication system 100 according to the present embodiment includes an OFDM transmitter 110 for transmitting wideband data and an OFDM receiver 120 for receiving wideband data. The OFDM receiver 120 includes an RF communication unit 130, an ADC 140, an FFT 150, an equalizer 160 and a demodulator 170.

The OFDM transmitter 110 generates a plurality of modulated data and maps the modulated data to a subcarrier channel. The OFDM transmitter 110 sets a part of subcarrier channels as a pilot channel, and inserts a pilot signal into the pilot channel. Here, the pilot channel inserts the pilot signal into a sequence having a sequence of + (Positive), + (Positive), - (Negative), and 0 (Zero).

The OFDM transmitter 110 performs inverse fast Fourier transform (IFFT) operation on a signal included in a subcarrier channel to output sample data in a time domain and adds a CP (Cyclic Prefix) to the sample data to generate an OFDM symbol And transmits the wideband data obtained by converting the OFDM symbol generated after the generation of the analog signal to the receiver 200.

The OFDM receiver 120 receives broadband data from the OFDM transmitter 110.

The RF communication unit 130 receives the wideband data transmitted from the OFDM transmitter 110. Here, the wideband data is received in a form in which a noise component is added via a multipath channel. The RF communication unit 130 outputs the analog signal obtained by downconverting the received wideband data to an intermediate frequency (IF) band or an area near the DC to the ADC 140.

The ADC 140 samples the analog signal and converts it into a digital signal. In other words, the ADC 140 acquires the analog signal output from the RF communication unit 130 and outputs the digital-converted sample data to the FFT 150. Here, the sample data may be output to the FFT 150 via a guard interval remover (not shown) that removes a CP (Cyclic Prefix).

The FFT 150 performs an FFT (Fast Fourier Transform) operation on the sample data to generate OFDM symbols in the frequency domain.

The equalizer 160 is located between the FFR 160 and the demodulator 170 and compensates for distortion of data included in the subcarrier channel output from the output terminal of the FFT 150. [ More specifically, a pilot signal included in a pilot channel of a subcarrier channel is analyzed to compensate for distortion of data included in a data subcarrier channel interlocked with the pilot channel. The operation of compensating the distortion in the equalizer 160 will be described in detail in FIG.

The demodulator 170 demodulates the data signal in which the distortion is compensated in the equalizer 160 by a modulation scheme, for example, a Quadrature Amplitude Modulation (QAM) scheme used in the OFDM transmitter 110.

2 is a block diagram schematically showing an equalizer included in a receiver according to the present embodiment.

The equalizer 160 according to the present embodiment includes a first coordinate system converter 210, a pilot sequence checker 220, a second coordinate system converter 230, a compensation value calculator 240, a distortion compensator 250 A third coordinate system conversion unit 270, a fifth coordinate system conversion unit 280, and a monitoring unit 290. The third coordinate system conversion unit 270 includes a first coordinate system conversion unit 260,

The equalizer 160 is located between the FFR 160 and the demodulator 170 and compensates for distortion of data included in the subcarrier channel output from the output terminal of the FFT 150. [ More specifically, a pilot signal included in a pilot channel of a subcarrier channel is analyzed to compensate for distortion of data included in a data subcarrier channel interlocked with the pilot channel. Hereinafter, the components included in the equalizer 160 will be described.

The first coordinate system converter 210 acquires an I / Q signal for a data signal included in a data subcarrier channel, and converts the obtained I / Q signal into a polar coordinate system. In other words, the first coordinate system converter 210 receives the I / Q signal obtained for the data signal, and extracts the first amplitude and the first phase based on the converted polar coordinates.

The first coordinate system conversion unit 210 preferably extracts a first amplitude and a first phase by converting an I / Q signal of a data signal into a polar coordinate system by applying a CORDIC (Coordinate Rotation DIGITAL Computer) algorithm. However, Any algorithm can be applied as long as it can convert orthogonal input signals into amplitude and phase forms.

The first coordinate system converter 210 transmits the extracted first amplitude and the first phase to the distortion compensator 250 to compensate for distortion of the data.

The pilot sequence verifying unit 220 obtains an I / Q signal from a pilot channel included in the OFDM symbol to check a sequence of the pilot signal, and outputs an I signal corresponding to a predetermined sequence value of the sequence of the pilot signal, / Q extracts the signal. Here, the pilot signal sequence is inserted in the sequence of + (Positive), + (Positive), - (Negative) and 0 (Zero) in the process of inserting the pilot signal into the subcarrier channel in the OFDM transmitter 110, +, -, and 0, respectively.

The pilot sequence confirmation unit 220 extracts only the I / Q signals for the pilot signals having positive sequence values. For example, the pilot sequence check unit 220 may acquire an I / Q signal from the pilot channel and ignore it if it has a negative sequence value and a sequence value of 0, Extracts only the I / Q signal of the signal and transmits it to the second coordinate system conversion unit 230. The pilot sequence verification unit 220 can recognize that the received pilot signal is a signal having a positive sequence value after extracting the pilot signal having the sequence value of 0, and extract the pilot signal.

The second coordinate system conversion unit 230 acquires an I / Q signal of a pilot signal corresponding to a predetermined sequence value from the pilot sequence verification unit 220, and converts the I / Q signal into polar coordinates. The second coordinate system conversion unit 230 extracts the second amplitude and the second phase for the pilot channel based on the converted polar coordinates.

When the pilot signal is inserted in the OFDM transmitter 110, only the value of the I signal is input and the value of the Q signal is input as zero. However, during transmission to the OFDM receiver 120, the I and Q signals are distorted and have different values from the values inserted in the OFDM transmitter 110. [ Accordingly, the second coordinate system converter 230 obtains the pilot signal having a different value from the pilot signal inserted in the OFDM transmitter 110, and extracts the second amplitude and the second phase of the distorted pilot signal.

The second coordinate system conversion unit 230 preferably extracts the second amplitude and the second phase by converting the I / Q signal of the pilot signal corresponding to the predetermined sequence value into polar coordinates by applying the CORDIC algorithm, Any algorithm can be applied as long as it can convert orthogonal input signals into amplitude and phase forms.

The second coordinate system converter 230 transmits the extracted second amplitude and the second phase to the compensation value calculator 240 so that compensation values for the amplitude and the phase are calculated.

The compensation value calculating section 240 calculates the distortion compensation value based on the second amplitude and the second phase for the pilot channel. Here, the distortion compensation value includes the amplitude compensation value and the phase compensation value. The compensation value calculator 240 includes an amplitude compensation value determiner 242 and a phase compensation value determiner 244.

The amplitude compensation value determination unit 242 accumulates the second amplitudes and calculates a moving average value for the accumulated second amplitudes to determine the amplitude compensation value. In other words, the amplitude compensation value determiner 242 accumulates the second amplitudes for the pilot signal having the positive sequence value, calculates the average value of the accumulated second amplitudes, and outputs the determined amplitude compensation value to the distortion compensator 250). Here, the average value of the plurality of second amplitudes may be an amplitude compensation value obtained by calculating an average of a plurality of accumulated amplitudes and an average of newly input second amplitudes, but not always limited thereto, and a plurality of amplitudes And an amplitude compensation value obtained by calculating an average of the newly inputted second amplitudes.

The process of calculating the average value of the plurality of amplitudes and the amplitude compensation value obtained by calculating the average of the newly inputted second amplitudes is, for example, 1.8, which is an average value of a plurality of amplitudes of 1, 2, 3 and 2, And the average of the second amplitude 3 is calculated to be 2.4 as the amplitude compensation value. On the other hand, in the process of calculating the amplitude compensation value by calculating each of the plurality of amplitudes and the average of the newly input second amplitudes, for example, a plurality of amplitudes of 1, 2, 3 and 2 are accumulated, And a newly calculated second average amplitude of 3, 2, may be calculated as the amplitude compensation value.

The phase compensation value determiner 244 accumulates the second phase and calculates a moving average value for the accumulated second phase to determine a phase compensation value. In other words, the phase compensation value determiner 244 accumulates the second phase for the pilot signal having the positive sequence value, calculates the average value of the accumulated second phases, and outputs the determined phase compensation value to the distortion compensator 250). Here, the average value of the plurality of second phases may be a phase compensation value obtained by calculating an average of a plurality of previously accumulated phases and an average of a newly input second phase, but the present invention is not limited thereto. And a phase compensation value obtained by calculating an average of a newly input second phase.

The process of calculating the average value of the plurality of phases and the phase compensation value calculating the average of the newly input second phases may be performed by calculating the average value of the plurality of phases of 1 °, 2 °, 3 ° and 2 °, for example, 1.8 ° And 2.4 °, which is the average of the newly inputted second phase of 3 °, can be calculated as the phase compensation value. Meanwhile, the process of calculating the phase compensation value by calculating the average of the plurality of phases and the newly inputted second phase includes accumulating a plurality of phases of, for example, 1 °, 2 °, 3 ° and 2 ° , The phase compensation value may be calculated from the plurality of phases and the 2 ° which is the average of the newly inputted second phase of 3 °.

The distortion compensating unit 250 obtains a distortion compensation value including the amplitude compensation value and the phase compensation value from the compensation value calculating unit 240, and calculates a first amplitude and a second amplitude of the data signal based on the obtained distortion compensation value, Phase. The distortion compensating unit 250 includes an amplitude compensating unit 252 for compensating for the first amplitude and a phase compensating unit 254 for compensating for the first phase.

The amplitude compensating section 252 applies the amplitude compensation value to the first amplitude to compensate for the distortion of the first amplitude. The amplitude compensating unit 252 may be implemented as a mixer that mixes the amplitude compensation value and the first amplitude. The amplitude compensating unit 252 transmits the distortion-compensated first amplitude to the third coordinate system transforming unit 260.

The phase compensation unit 254 applies the phase compensation value to the first phase to compensate for the distortion of the first phase. The phase compensation unit 254 compensates for the distortion of the first phase by adding the phase compensation value to the first phase without multiplying operation. The phase compensation unit 254 transmits the distortion-compensated first phase to the third coordinate system conversion unit 260.

In FIG. 2, the distortion compensating unit 250 compensates for distortion by applying a distortion compensation value to only the first amplitude and the first phase acquired from the first coordinate system converting unit 210. However, The distortion can be compensated by applying the same distortion compensation value to the amplitude and phase of each of the plurality of data subcarrier channels.

The third coordinate system conversion unit 260 obtains the distortion-compensated first amplitude and the first amplitude from the distortion compensator 250, and converts the distortion-compensated first amplitude and the first amplitude into the Cartesian coordinates, And transmits the compensated I / Q signal to the demodulator 170.

Hereinafter, an operation of monitoring the signal distortion compensation of the equalizer 160 will be described.

The fourth coordinate system converter 270 obtains the I / Q signal for the pilot signal included in the pilot channel, and converts the obtained I / Q signal into polar coordinates. The fourth coordinate system converter 270 extracts the third amplitude and the third phase of the pilot signal based on the converted polar coordinates.

The fourth coordinate system transforming unit 270 transforms the I / Q signal of the pilot signal into polar coordinates by applying a CORDIC algorithm to extract the third amplitude and the third phase, but it is not limited thereto, Any algorithm can be applied if the signal can be converted to amplitude and phase forms.

The fourth coordinate system converter 270 transmits the extracted third amplitude and the third phase to the distortion compensator 250.

The distortion compensation unit 250 obtains a distortion compensation value including the amplitude compensation value and the phase compensation value from the compensation value calculation unit 240, and calculates a third amplitude for the pilot signal and a third amplitude for the third signal based on the obtained distortion compensation value. Phase. Here, the operation for compensating the third amplitude and the third phase is the same as the operation for compensating the first amplitude and the first phase for the data signal, so a detailed description will be omitted.

The fifth coordinate system transforming unit 280 obtains the third amplitude and the third amplitude, the distortion of which is compensated, from the distortion compensating unit 250, and transforms the first amplitude and the first amplitude of the distortion into the orthogonal coordinates, And transmits the compensated I / Q signal to the monitoring unit 290.

The monitoring unit 290 acquires the distortion compensated I / Q signal from the fifth coordinate system converter 280 and checks the bit error rate (BER) of the I / Q signal with distortion compensation, And monitors the state or accuracy of the distortion compensation of the device 160. 2, the monitoring unit 290 is provided in the demodulator 170, but the present invention is not limited thereto. The monitoring unit 290 may be included in the equalizer 160 or may be connected to the outside of the receiver 120.

3 is a flowchart for explaining a method of compensating distortion of a subcarrier channel in an equalizer according to the present embodiment.

The first coordinate system conversion unit 210 obtains the I / Q signal from the data subcarrier channel (S310). The first coordinate system conversion unit 210 converts the acquired I / Q signal into polar coordinates and extracts a first amplitude and a first phase of the data subcarrier channel (S320).

The pilot sequence verifying unit 220 obtains an I / Q signal from a pilot channel (S330). The pilot sequence verifying unit 220 confirms the sequence of the pilot signal (S340).

If it corresponds to the predetermined sequence value (S350), the pilot sequence verifying unit 220 extracts the corresponding I / Q signal (S360).

The second coordinate system conversion unit 230 converts the I / Q signal corresponding to the extracted sequence value into polar coordinates and extracts the second amplitude and the second phase for the pilot channel in step S370.

The compensation value calculation unit 240 calculates a distortion compensation value based on the second amplitude and the second phase (S380).

The distortion compensating unit 250 compensates the first amplitude and the first phase based on the distortion compensation value (S390). The third coordinate system conversion unit 260 converts the distortion-compensated first amplitude and the first phase into orthogonal coordinates and transmits them to the demodulator (S392).

4 is an exemplary diagram for explaining the operation of the equalizer according to the present embodiment.

The OFDM symbol output from the FFT 150 includes 128 subcarrier channels. Here, the 128 subcarrier channels include one DC subcarrier channel, 123 data subcarrier channels, and four pilot channels.

As shown in FIG. 4, the 17th subcarrier channel, the 50th subcarrier channel, the 78th subcarrier channel, and the 111st subcarrier channel are pilot channels, and each pilot channel is interlocked with a plurality of data subcarrier channels. For example, the seventeenth subcarrier channel interlocks with the first data subcarrier channel through the sixteenth data subcarrier channel and the eighteenth data subcarrier channel through the thirty-third data subcarrier channel.

The first coordinate system conversion unit 210 obtains the I / Q signals I _d and Q _d from the data subcarrier channels and converts the obtained I / Q signals I _d and Q _d into polar coordinates, And extracts a first amplitude and a first phase for the channel. Here, the first amplitude is calculated by the square root of the squared value of the I signal I _d and the square value of the Q signal Q _d , and the first phase is calculated by the angle that the first amplitude moves in the I axis do.

The pilot sequence verifier 220 obtains the I / Q signal I _p , Q _p from the pilot channel (seventeenth subcarrier channel). Here, the I / Q signal (I _p , Q _p ) means a signal in which distortion occurs. The pilot sequence confirmation unit 220 identifies the sequence of the pilot signal and extracts only the I / Q signals I _p and Q _p for the pilot signal having a positive sequence value.

The second coordinate system conversion unit 230 converts the I / Q signals I _p and Q _p for the pilot signal having positive sequence values into polar coordinates and outputs the second amplitude and the second phase for the pilot channel . Here, the second amplitude is calculated by the square root of the squared value of the I signal (I _p ) and the square value of the Q signal (Q _p ), and the second phase is calculated by the angle that the second amplitude moves in the I axis do.

The amplitude compensation value determination unit 242 accumulates the second amplitudes and calculates an average value of the accumulated plurality of second amplitudes to determine the amplitude compensation value. The amplitude compensation value determiner 242 transmits the determined amplitude compensation value to the amplitude compensator 252. The phase compensation value determiner 244 accumulates the second phase and calculates an average value of the accumulated plurality of second phases to determine a phase compensation value. The phase compensation value determiner 244 transmits the determined phase compensation value to the phase compensator 254.

The amplitude compensating section 252 applies the amplitude compensation value to the first amplitude to compensate for the distortion of the first amplitude. The amplitude compensating unit 252 may be implemented as a mixer that mixes the amplitude compensation value and the first amplitude. In addition, the phase compensator 254 applies the phase compensation value to the first phase to compensate for the distortion of the first phase. The phase compensation unit 254 compensates for the distortion of the first phase by adding the phase compensation value to the first phase without multiplying operation.

The third coordinate system converter 260 transmits the distortion-compensated first amplitude and the first phase to the I / Q signal (I ^d , Q ^d ) demodulator converted into the orthogonal coordinates.

5 is an exemplary diagram for explaining the operation of the coordinate system converting unit included in the equalizer according to the present embodiment.

The operation of the coordinate converter shown in FIG. 5 includes a second coordinate system for converting an I / Q signal of a pilot signal corresponding to a predetermined sequence value into a polar coordinate and extracting a second amplitude and a second phase from the pilot sequence verification unit 220, The operation of the conversion unit 230 is shown.

The distortion-free pilot signal should be located at the first point 510 on the I coordinate axis. However, the pilot signal is distorted in the process of being received by the OFDM transmitter 110 in the OFDM receiver 120, and is located at the second point 520.

In other words, when the I / Q signal of the ideal pilot signal without distortion is input, the second coordinate system converter 230 receives the I / Q signal for the (p, 0) first point 510, The amplitude p and the phase 0 should be extracted.

However, when the OFDM transmitter 110 receives the I / Q signal of the pilot signal, the second coordinate system transformer 230, which is distorted in the process of being received by the OFDM transmitter 110, (I _p , Q _p ), and converts the I / Q signals into polar coordinates to extract the amplitudes α and phase p.

6 is an exemplary diagram illustrating a data subcarrier channel and a pilot channel included in an OFDM symbol according to the present embodiment.

As shown in FIG. 6, an OFDM symbol generated in the OFDM transmitter 110 and transmitted to the OFDM receiver 120 includes 128 subcarrier channels. Here, the 128 subcarrier channels include one DC subcarrier channel, 123 data subcarrier channels, and four pilot channels. For example, the OFDM symbols group the first subcarrier channel to the 33rd subcarrier channel into a first group and allocate the pilot channel for the first group to the 17th subcarrier channel. In addition, the OFDM symbol groups the 34th subcarrier channel to the 63rd subcarrier channel into a second group, and allocates the pilot channel for the second group to the 50st subcarrier channel. Also, the OFDM symbol groups the 64th subcarrier channel to the 94th subcarrier channel into a third group, and allocates the pilot channel for the third group to the 78th subcarrier channel. In addition, the OFDM symbol groups the 95th subcarrier channel to the 127th subcarrier channel into a fourth group, and allocates the pilot channel for the fourth group to the 111st subcarrier channel.

7 is an exemplary diagram showing a signal in which distortion is compensated in the equalizer according to the present embodiment.

7A is a graph showing a signal of a subcarrier channel obtained by the equalizer 160 from the FFT 150. FIG. That is, the graph of FIG. 7A shows a signal of a subcarrier channel whose amplitude and phase are distorted.

7B is a graph showing a signal of a subcarrier channel outputted by correcting the distortion in the equalizer 160. FIG. That is, the graph of FIG. 7 (b) shows a signal of a subcarrier channel whose distortion is compensated by applying a distortion compensation value calculated based on the amplitude and phase of the pilot signal.

The foregoing description is merely illustrative of the technical idea of the present embodiment, and various modifications and changes may be made to those skilled in the art without departing from the essential characteristics of the embodiments. Therefore, the present embodiments are to be construed as illustrative rather than restrictive, and the scope of the technical idea of the present embodiment is not limited by these embodiments. The scope of protection of the present embodiment should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

100: wireless communication system 110: OFDM transmitter
120: OFDM receiver 130: RF communication unit
140: ADC 150: FFT
160: equalizer 170: equalizer
210: first coordinate system conversion unit 220: pilot sequence confirmation unit
230: second coordinate system conversion unit 240: compensation value calculation unit
242: amplitude compensation value determination unit 244: phase compensation value determination unit
250: distortion compensating unit 252: amplitude compensating unit
254: phase compensating unit 260: third coordinate system converting unit
270: fourth coordinate system conversion unit 280: fifth coordinate system conversion unit
290: Monitoring section

Claims (16)

1. An apparatus for compensating for distortion of a data subcarrier channel included in an Orthogonal Frequency Division Multiplexing (OFDM) symbol,
A first coordinate system conversion unit for obtaining an I / Q signal for a data signal from the data subcarrier channel, converting the I / Q signal to polar coordinates, and extracting a first amplitude and a first phase for the data subcarrier channel based on the polar coordinates;
Acquires an I / Q signal from a pilot channel included in the OFDM symbol to check a sequence of a pilot signal, and extracts an I / Q signal corresponding to a predetermined sequence value of the sequence of the pilot signal A pilot sequence verifying unit;
A second coordinate system conversion unit for converting an I / Q signal corresponding to the predetermined sequence value to polar coordinates, and extracting a second amplitude and a second phase for the pilot channel based on the polar coordinates;
A compensation value calculation unit for calculating a distortion compensation value based on the second amplitude and the second phase;
A distortion compensator for compensating for the first amplitude and the first phase based on the distortion compensation value; And
A third coordinate system conversion unit for converting the distortion-compensated first amplitude and first phase into orthogonal coordinates and demodulating the first amplitude and the first phase,
≪ / RTI > The method according to claim 1,
Wherein the pilot sequence verifying unit comprises:
(I) of a pilot signal having positive (+) sequence values in the sequence of the pilot signals input in the order of + (Positive), + (Positive), - (Negative) / Q signal and transmits the extracted signal to the second coordinate system conversion unit. The method according to claim 1,
Further comprising a fourth coordinate system conversion unit for obtaining an I / Q signal from the pilot channel and converting the I / Q signal to polar coordinates, and extracting a third amplitude and a third phase for the pilot channel based on the polar coordinates,
Wherein the distortion compensating unit compensates the third amplitude and the third phase based on the distortion compensation value. The method of claim 3,
And a monitoring unit for monitoring the distortion compensation of the data subcarrier channel by obtaining the third amplitude and the third phase of the distortion compensated from the distortion compensating unit. 5. The method of claim 4,
The monitoring unit,
And monitors the state or accuracy of the distortion compensation by checking a bit error rate (BER) for the third amplitude and the third phase with the distortion compensated. The method according to claim 1,
The pilot channel includes:
Wherein the distortion compensation unit compensates for the amplitude and phase of each of the plurality of data subcarrier channels by using the distortion compensation value in association with a plurality of data subcarrier channels. The method according to claim 1,
Wherein the first coordinate system converting unit and the second coordinate system converting unit convert
And converting an I / Q signal of the data signal to a polar coordinate based on a CORDIC (Coordinate Rotation DIgital Computer) algorithm. The method according to claim 1,
The compensation value calculation unit calculates,
An amplitude compensation value determination unit for accumulating the second amplitudes and calculating a moving average value for the accumulated second amplitudes to determine an amplitude compensation value; And
And a phase compensation value determination unit for accumulating the second phase and calculating a moving average value for the accumulated second phase to determine a phase compensation value,
Wherein the distortion compensation value comprises the amplitude compensation value and the phase compensation value. 9. The method of claim 8,
Wherein the distortion compensating unit comprises:
An amplitude compensation unit for applying the amplitude compensation value to the first amplitude to compensate for the distortion of the first amplitude; And
And a phase compensation unit for applying the phase compensation value to the first phase to compensate for the distortion of the first phase. 10. The method of claim 9,
Wherein the amplitude compensator comprises:
And a mixer for mixing the amplitude compensation value and the first amplitude. 10. The method of claim 9,
Wherein the phase compensator comprises:
And the phase compensation value is added to the first phase to compensate for the distortion of the first phase. A method of compensating for distortion of a data subcarrier channel included in an OFDM symbol,
A first coordinate system transforming step of obtaining an I / Q signal for a data signal from the data subcarrier channel, converting the I / Q signal to polar coordinates, and extracting a first amplitude and a first phase for the data subcarrier channel based on the polar coordinates;
Acquires an I / Q signal from a pilot channel included in the OFDM symbol to check a sequence of a pilot signal, and extracts an I / Q signal corresponding to a predetermined sequence value of the sequence of the pilot signal A pilot sequence confirmation process;
A second coordinate system conversion step of converting an I / Q signal corresponding to the predetermined sequence value into polar coordinates, and extracting a second amplitude and a second phase with respect to the pilot channel based on the polar coordinates;
A compensation value calculation step of calculating a distortion compensation value based on the second amplitude and the second phase;
A distortion compensating step of compensating the first amplitude and the first phase based on the distortion compensation value; And
A third coordinate system conversion process for converting the distortion-compensated first amplitude and the first phase into orthogonal coordinates and demodulating
And compensating for the distortion of the subcarrier channel. 13. The method of claim 12,
The compensation value calculation step may include:
Calculating an amplitude compensation value by accumulating the second amplitude and calculating a moving average value with respect to the accumulated second amplitude to determine an amplitude compensation value; And
And determining a phase compensation value by accumulating the second phase and calculating a moving average value for the accumulated second phase,
Wherein the distortion compensation value includes the amplitude compensation value and the phase compensation value. 14. The method of claim 13,
The distortion compensation process includes:
An amplitude compensation step of applying the amplitude compensation value to the first amplitude to compensate for distortion of the first amplitude; And
And compensating a distortion of the first phase by applying the phase compensation value to the first phase. 13. The method of claim 12,
Further comprising a fourth coordinate system conversion step of obtaining an I / Q signal from the pilot channel and converting the I / Q signal into polar coordinates, and extracting a third amplitude and a third phase with respect to the pilot channel based on the polar coordinates,
Wherein the distortion compensating step compensates the third amplitude and the third phase based on the distortion compensation value. 16. The method of claim 15,
And monitoring the distortion compensation of the data subcarrier channel by obtaining the third amplitude and the third phase in which the distortion is compensated in the distortion compensation process. .

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