WO2018088620A1 - Method for compensating for distortion of subcarrier by using single-tap equalizer in ofdm system and apparatus therefor - Google Patents

Abstract

Disclosed are a method for compensating for distortion of a subcarrier in an OFDM-based wireless communication system and an apparatus therefor. The present invention relates to a method for compensating for distortion of a subcarrier in an OFDM-based wireless communication system and an apparatus therefor, the method comprising: extracting the amplitude and the phase of a pilot signal; and calculating a distortion compensation value by using the extracted amplitude and phase, so as to compensate for each of the amplitude and the phase of a data signal.

Description

Distortion Compensation Method for Subcarriers Using Single Tap Equalizer in ODF System and Apparatus Therefor

The present embodiment relates to a distortion compensation method for a subcarrier using a single tap equalizer in an OFDM system, and an apparatus therefor.

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

Recently, the OFDM method, which is used as a useful method for high-speed data transmission in a wired / wireless channel, is a method of transmitting data using a multicarrier, and converts each of them in parallel by serially converting symbol strings. It is a type of multi-carrier modulation (MCM) that modulates and transmits a plurality of subcarriers having mutual orthogonality.

The OFDM scheme further reduces the negative effects of multipath and delay spread systems with the use of guard intervals and the insertion of cyclic prefix (CP) guard intervals. In addition, the OFDM method is rapidly developing due to various digital signal processing technologies including a Fast Fourier Transform (FFT) and an Inverse Fast Fourier Transform (IFFT).

The OFDM scheme is characterized by obtaining optimal transmission efficiency in high-speed data transmission by maintaining orthogonality between a plurality of subcarriers. In addition, the frequency usage efficiency is good and the characteristics of the multi-path fading (Multi-Path Fading) has the characteristics that can be obtained the optimum transmission efficiency when high-speed data transmission. In addition, because the frequency spectrum is superimposed, the use of frequency is efficient, and there is a strong advantage in frequency selective fading and multipath fading. In addition, because the frequency spectrum is superimposed, it is possible to reduce the influence of inter-symbol interference (ISI) by using the protection interval, and it is possible to simply design the equalizer structure in terms of hardware and impulse characteristics. It has the advantage of being strong against noise.

The multiple access scheme based on the OFDM scheme is the OFDMA scheme. The OFDMA method divides and uses subcarriers in one OFDM symbol by a plurality of users, that is, a plurality of terminals.

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 the distorted transmission signal. In addition, due to a problem on a channel until the transmission signal of the transmitter is transmitted to the receiver, the transmission signal may be lost before being transmitted to the receiver, or the transmission signal may be distorted and received. Accordingly, in the broadband wireless communication system, various alternatives have been researched and developed to improve the reception performance of the receiver.

The present embodiment extracts a received pilot signal included in at least one data subcarrier channel and calculates a distortion compensation value for each data subcarrier channel by using a distortion vector value calculated by comparing a preset transmission pilot signal and a received pilot signal. It is a main object of the present invention to provide a distortion compensation method for a subcarrier using a single tap equalizer that calculates and applies a distortion compensation value to a data signal, and a device therefor.

According to an aspect of the present embodiment, a device for compensating for distortion of a data subcarrier channel included in an orthogonal frequency division multiplexing (OFDM) symbol, the pilot signal extracting a received pilot signal from each of at least one data subcarrier channel Extraction unit; A channel estimator for estimating a channel by calculating a distortion vector value of at least one received pilot signal using a preset transmission pilot value; A compensation value calculator configured to calculate a distortion compensation value for each of at least one data subcarrier channel using the distortion vector value; A compensation value processor for transmitting the distortion compensation value to each of the at least one data subcarrier channel; And a distortion compensator for compensating for the distortion of the data signal for each of the at least one data subcarrier channel based on the distortion compensation value.

According to another aspect of the present embodiment, a method for compensating for distortion of a data subcarrier channel included in an orthogonal frequency division multiplexing (OFDM) symbol includes extracting a received pilot signal from each of at least one data subcarrier channel. Pilot signal extraction process; A channel estimating step of estimating a channel by calculating a distortion vector value of at least one received pilot signal using a preset transmission pilot value; Calculating a distortion compensation value for each of at least one data subcarrier channel using the distortion vector value; A compensation value processing step of transmitting the distortion compensation value to each of the at least one data subcarrier channel; And a distortion compensation process of compensating for distortion of the data signal for each of the at least one data subcarrier channel based on the distortion compensation value.

As described above, according to the present embodiment, the distortion of the data signal can be greatly improved.

In addition, it is possible to accurately compensate for the distortion of the data signal of the subcarrier channel by using the distortion compensation device, it is possible to ensure the high quality OFDM communication performance.

In addition, the distortion compensating apparatus compensates for the distortion by using the pilot signals for all the subcarrier channels, thereby effectively compensating for the distortion of the data signal of the subcarrier channel.

In addition, the distortion compensator has an effect of minimizing the amount of computation for compensating for the distortion.

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

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

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

4 and 5 are exemplary views schematically showing an operation of compensating for distortion of a subcarrier channel according to the present embodiment.

FIG. 6 is a graph illustrating an operation of compensating for distortion in an equalizer based on sixteen subcarrier channels according to the present embodiment.

7 is an exemplary diagram for schematically describing an operation of an equalizer for compensating for distortion of a subcarrier channel according to the present embodiment.

8 illustrates an example of an equalizer for compensating for distortion of a subcarrier channel according to the present embodiment.

9 is an exemplary view illustrating a pilot signal for compensating for distortion of a subcarrier channel according to the present embodiment.

10 is an exemplary view illustrating a signal in which distortion is compensated for in an 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 illustrating an OFDM based wireless communication system according to the present embodiment.

The orthogonal frequency division multiplexing (OFDM) based wireless communication system 100 according to the present embodiment includes an OFDM transmitter 110 for transmitting broadband data and an OFDM receiver 120 for receiving broadband 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 modulation data and maps them to a subcarrier channel. The OFDM transmitter 110 sets some of the subcarrier channels as pilot channels and inserts pilot signals into the pilot channels. Here, the pilot signal does not include actual data, and means a signal inserted for channel estimation, synchronization, information acquisition, distortion compensation, and the like.

The OFDM transmitter 110 performs IFFT (Inverse Fast Fourier Transform) operation on the signal included in the subcarrier channel to output sample data in the time domain, and adds a guard period (CP) to the sample data to add an OFDM symbol (Symbol). And then transmit the wideband data obtained by converting the generated OFDM symbol into an analog signal to the OFDM receiver 120.

The OFDM transmitter 110 transmits a data signal including a transmission pilot signal on at least one data subcarrier channel. Here, the transmission pilot signal may be a signal having the same value, but is not necessarily limited thereto.

OFDM receiver 120 receives wideband data from OFDM transmitter 110.

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

The ADC 140 samples an analog signal and converts it into a digital signal. In other words, the ADC 140 obtains the analog signal output from the RF communication unit 130 and outputs the digitally 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 guard period (CP).

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

The equalizer 160 is positioned between the FFT 150 and the demodulator 170 and performs an operation of compensating for distortion of data included in a subcarrier channel output from an output terminal of the FFT 150.

The equalizer 160 according to the present embodiment extracts a received pilot signal included in at least one data subcarrier channel. The equalizer 160 calculates a distortion vector value by comparing a preset transmission pilot signal and a reception pilot signal, and calculates a distortion compensation value for each data subcarrier channel using the calculated distortion vector value.

The equalizer 160 generates the distortion-compensated data signal by applying the calculated distortion compensation value to the data signal and transmits the data signal to the demodulator 179. Compensation for the distortion in the equalizer 160 will be described in detail with reference to FIG. 2.

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

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

The equalizer 160 according to the present embodiment includes a pilot signal extractor 210, a channel estimator 220, a compensation value calculator 230, a compensation value processor 240, and a distortion compensator 250. . Here, the equalizer 160 may be an equalizer included in the OFDM receiver 120, but is not limited thereto. The equalizer 160 may be provided inside or outside the OFDM receiver 120 to compensate for signal distortion included in the data signal. It may be implemented as a compensation device.

The pilot signal extractor 210 extracts a received pilot signal from the data subcarrier channel. In other words, the pilot signal extractor 210 obtains an I / Q signal from a pilot channel included in an OFDM symbol and extracts a received pilot signal corresponding to a predetermined sequence. Here, the received pilot signal refers to a signal received by the OFDM transmitter 110 a transmission pilot signal inserted into the subcarrier channel. The received pilot signals are received in the order in which the transmit pilot signals are inserted, and each received pilot signal includes an I / Q signal. The received pilot signal is distorted in the process of being received from the OFDM transmitter 110. That is, the received pilot signal contains a distortion signal.

The pilot signal extractor 210 may extract k received pilot signals (1 ≦ k ≦ m, k is a natural number and m is the number of subcarrier channels) for at least one data subcarrier channel. When there is a received pilot signal in all data subcarrier channels, a peak of a signal occurs. Therefore, k (1 ≤ k ≤ m, k is a natural number and m is the number of subcarrier channels) of at least one data subcarrier channel. Extract the received received pilot signal. For example, the pilot signal extractor 210 may extract a transmitted pilot signal transmitted in 14 times for 128 data subcarrier channels as a received pilot signal.

The channel estimator 220 estimates a distortion state of the data subcarrier channel based on the received pilot signal.

The channel estimator 220 calculates a distortion vector value for the received pilot signal using a preset transmission pilot value, and estimates a distortion state of the data subcarrier channel based on the distortion vector value. In more detail, the channel estimator 220 calculates a distortion vector value of the received pilot signal by comparing the transmission pilot value of the transmission pilot signal transmitted from the OFDM transmitter 110 and the reception pilot value of the reception pilot signal. Here, the transmission pilot signals of each of the at least one data subcarrier channel may have the same value, but are not necessarily limited thereto, and are pilot signals combined with values such as + (Positive),-(Negative), and 0 (Zero). Can be. For example, the transmission pilot signal of each data subcarrier channel has the same transmission pilot value as a '1' value, and the channel estimator 220 has a value of the transmission pilot signal and the reception pilot signal having a value of '1'. The distortion vector value can be calculated by comparing the two values. On the other hand, the transmission pilot signal of each data subcarrier channel is a distortion vector by comparing the transmission pilot value having a value of '1', '-1', '1' ..., '-1' and the received pilot signal The value can be calculated.

The channel estimator 220 calculates a distortion vector value using k received pilot signals (1 ≦ k ≦ m, where k is a natural number and m is the number of subcarrier channels) extracted for at least one data subcarrier channel. One is not necessarily limited thereto. For example, the channel estimator 220 may calculate a distortion vector value using 14 received pilot signals for 128 data subcarrier channels.

The channel estimator 220 may calculate an average of the distortion values of each of the k received pilot signals for the at least one data subcarrier channel and calculate the average of the distortion vector values.

The compensation value calculator 230 calculates a distortion compensation value for compensating for signal distortion of the data signal for each data subcarrier channel by using the distortion vector value. Here, the compensation value calculator 230 may calculate the distortion compensation value by calculating an inverse value of the distortion vector value, but is not necessarily limited thereto.

The compensation value calculator 230 sets a processing time for calculating the distortion compensation value. In other words, the compensation value calculator 230 sets a processing time to less than a channel varying time of at least one data subcarrier channel.

The compensation value calculator 230 calculates a distortion compensation value for each data subcarrier channel, and each distortion compensation value may include a first compensation value for the I signal and a second compensation value for the Q signal.

The compensation value processor 240 transmits the distortion compensation value to each data subcarrier channel. The compensation value processor 240 transmits the distortion compensation value to each of at least one data subcarrier channel.

The compensation value processor 240 may separately transmit the first compensation value and the second compensation value included in the distortion compensation value, but the present invention is not limited thereto. The compensation value processor 240 may transmit the first compensation value and the second compensation value to each data subcarrier channel. The distortion compensation value may be transmitted.

The distortion compensator 250 compensates the signal distortion of the data signal for each data subcarrier channel based on the distortion compensation value received from the compensation value processor 240.

The distortion compensator 250 receives the first data signal including the distortion signal from the OFDM transmitter 110, and applies the distortion compensation value to the first data signal to generate a second data signal having the distortion signal compensated.

The distortion compensator 250 may generate the second data signal by applying the first compensation value and the second compensation value included in the distortion compensation value to each of the I / Q signals included in the first data signal. For example, the distortion compensator 250 generates the I signal of the second data signal by applying the first compensation value to the I signal of the first data signal and applying the second compensation value to the Q signal of the first data signal. do. In addition, the distortion compensator 250 generates a Q signal of the second data signal by applying a second compensation value to the I signal of the first data signal and applying the first compensation value to the Q signal of the first data signal.

The distortion compensator 250 transmits the second data signal to the demodulator 170 so that the second data signal is demodulated.

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

The equalizer 160 extracts a received pilot signal for each data subcarrier channel (S310). The equalizer 160 obtains an I / Q signal from a pilot channel included in an OFDM symbol and extracts a received pilot signal corresponding to a predetermined sequence. Here, the received pilot signal refers to a signal received by the OFDM transmitter 110 a transmission pilot signal inserted into the subcarrier channel.

The equalizer 160 extracts k received pilot signals (1 ≦ k ≦ m, k is a natural number and m is the number of subcarrier channels) for at least one data subcarrier channel.

The equalizer 160 estimates the distortion state of the channel by calculating a distortion vector value for the received pilot signal (S320). The equalizer 160 calculates a distortion vector value for the received pilot signal using a preset transmission pilot value, and estimates the distortion state of the data subcarrier channel based on the distortion vector value. In other words, the equalizer 160 calculates a distortion vector value of the received pilot signal by comparing the transmission pilot value of the transmission pilot signal transmitted from the OFDM transmitter 110 and the reception pilot value of the reception pilot signal. Here, the transmission pilot signals of each of the at least one data subcarrier channel may have the same transmission pilot value, but are not necessarily limited thereto. For example, the transmission pilot signal of each of the at least one data subcarrier channel may be a pilot signal combined with a value such as positive (positive), negative (eg), zero (zero), or the like.

The equalizer 160 calculates a distortion compensation value for each data subcarrier channel using the distortion vector value (S330). The equalizer 160 calculates a distortion compensation value for compensating for signal distortion of the data signal for each data subcarrier channel using the distortion vector value. Here, the equalizer 160 may calculate the distortion compensation value by calculating an inverse value of the distortion vector value.

The equalizer 160 compensates for the distortion of the data signal by applying a distortion compensation value to the data signal for each data subcarrier channel (S340). The equalizer 160 receives the first data signal including the distortion signal from the OFDM transmitter 110, and applies a distortion compensation value to the first data signal to generate a second data signal with the distortion signal compensated.

4 is an exemplary view schematically showing an operation of compensating for distortion of a subcarrier channel according to the present embodiment.

Hereinafter, an operation for compensating for distortion of a subcarrier channel in the OFDM-based wireless communication system 100 will be described with reference to FIG. 4.

In the OFDM-based wireless communication system 100, an OFDM signal is influenced by a frequency selective filter, and a bandwidth of a subcarrier is designed to be smaller than a coherence bandwidth of a data subcarrier channel. Here, the equalizer 160 included in the wireless communication system 100 calculates frequency flat fading of each subcarrier channel represented by one complex multiplication, and equalization of the distorted signal is performed. Each subcarrier channel is processed using the same single tap.

The wireless communication system 100 according to the present embodiment performs OFDM equalization in the frequency domain. As shown in FIG. 4, an Inverse Fast Fourier Transform (IFFT) transform is performed through the OFDM transmitter 110 from the subcarrier vector X in the frequency domain to the data signal x in the time domain (x = IFFT). (X)).

In the process of transmitting the data signal x from the OFDM transmitter 110 to the OFDM receiver 120, an impulse response vector h of the data subcarrier channel, that is, a distortion signal is added. Accordingly, the OFDM receiver 120 receives a data signal y in which the data signal x and the distortion signal h are convolutiond (*) (y = x * h).

The OFDM receiver 120 converts the data signal y to a fast fourier transform (FFT) to generate a first data signal (Y). Here, the first data signal Y is Y = FFT (y) = XH, and H = FFT (h). The first data signal Y is generated by applying Element Wise-Multiplication (·).

The equalizer 160 included in the OFDM receiver 120 extracts a pilot signal from the first data signal Y, calculates a distortion signal H using the pilot signal, and estimates the distortion of the subcarrier channel.

The equalizer 160 compensates the distortion of each subcarrier channel by applying the inverse of the distortion signal H to the first data (Y). In other words, the equalizer 160 processes Z = Y / H = X · H / H to generate a second data signal Z whose distortion is compensated for. Here, the second data signal Z may be generated by applying Elements Wise-Division (/).

5 is an exemplary view schematically showing an operation of compensating for distortion of a subcarrier channel according to the present embodiment.

FIG. 5A illustrates transmission data X _n for each of at least one subcarrier channel. The transmission data X _n is IFFT transformed by the OFDM transmitter 110, and an impulse response vector h _n of the data subcarrier channel is added in the process of being transmitted to the OFDM receiver 120. Thus, OFDM receiver 120 receives the data signal (x _n) and a distortion signal (h _n), the convolution (*) data signal (y _n) (y = x * h).

FIG. 5B illustrates the first data signal Y obtained by FFT transforming the data signal x received from the OFDM transmitter 110 in the OFDM receiver 110. The first data signal Y _n includes a pilot signal P _n and a general data signal D _n .

FIG. 5C illustrates a pilot signal P _n extracted from the first data signal Y _n and a distortion signal H _n extracted using the pilot signal P _n . FIG. 5D illustrates a distortion compensation value / H _n calculated by performing inverse processing, that is, Elements Wise-Division (/) processing on the extracted distortion signal H _n . FIG. 5E illustrates second data X ′ _n compensated for distortion by applying a distortion compensation value / H _n to the first data signal Y. Referring to FIG.

FIG. 6 is a graph illustrating an operation of compensating for distortion in an equalizer based on sixteen subcarrier channels according to the present embodiment.

6A, 6B, and 6C are graphs for explaining an operation of calculating a distortion vector and a distortion compensation value using a received pilot signal including a transmission pilot signal and a distortion signal, and FIG. (D), (e) and (f) show graphs for explaining an operation of outputting a data signal with distortion compensation by applying a distortion compensation value to the input real data signal.

FIG. 6A illustrates a pilot signal having a size of 1 transmitted by being included in each of all data subcarrier channels (16 channels) in the OFDM transmitter 110.

6B illustrates a pilot signal including the distortion signal received by the equalizer 160. Here, the equalizer 160 extracts the distortion vector H from the received pilot signal.

FIG. 6C illustrates a distortion compensation value / H calculated using the distortion vector H extracted by the equalizer 160. Here, the equalizer 160 preferably calculates the distortion compensation value / H by calculating the inverse of the distortion vector H, but is not necessarily limited thereto.

FIG. 6D illustrates a data signal transmitted by being included in each data subcarrier channel (16 channels) in the OFDM transmitter 110.

6E illustrates a data signal including the distortion signal received by the equalizer 160. FIG. 6F illustrates a data signal in which distortion is compensated by applying the distortion compensation value / H shown in FIG. 6C to the received data signal.

Although FIG. 6 describes that distortion is compensated for by 16 subcarrier channel-based equalizers, the present invention is not limited thereto and may be applied to 2 ⁿ channel-based equalizers.

7 is an exemplary diagram for schematically describing an operation of an equalizer for compensating for distortion of a subcarrier channel according to the present embodiment.

As shown in FIG. 7, the equalizer 110 extracts a received pilot signal from a first data signal received through 128 subcarrier channels. Here, the received pilot signal is a vector in which a distortion signal is included in a transmission pilot signal having a size of 1, and includes [h ₀ ', h ₁ ', ..., h ₁₂₇ '] and the like. Here, the reception pilot signal is shown as extracted from each of 128 subcarrier channels, but is not necessarily limited thereto. The received pilot signal may be a reception pilot signal extracted from some channels of the 128 subcarrier channels.

The equalizer 110 extracts the distortion vector H from the received pilot signal and calculates a distortion compensation value H ⁻¹ using the distortion vector H. Here, the equalizer 110 may calculate the distortion vector H by receiving the received pilot signal M times (2 ≦ M, M is a natural number) in order to minimize an error (error) of the distortion vector H. For example, the equalizer 110 may calculate a distortion vector H using an average value of the movement of a window whose size is set to M, and the distortion vector H is [h ₀ , h _1. , ..., h ₁₂₇ ], and the like.

The equalizer 110 calculates the distortion compensation value H ⁻¹ by processing the calculated distortion vector H in inverse. The distortion compensation value H ^-1 may include [r ₀ , r ₁ ,..., R ₁₂₇ ]. The equalizer 110 calculates a distortion compensation value H ⁻¹ including a first compensation value and a second compensation value for compensating the I / Q signal of the data signal.

The equalizer 110 compensates for the distortion by applying the distortion compensation value H ⁻¹ to the data signal y _n including the distortion signal. The equalizer 110 applies the first compensation value to the I signal of the data signal y _n including the distortion signal, and applies the second compensation value to the Q signal to generate the I signal of the data signal with distortion compensation. do. In addition, the equalizer 110 applies the second compensation value to the I signal of the data signal y _n including the distortion signal, and applies the first compensation value to the Q signal, thereby applying the Q signal of the data signal whose distortion is compensated. Create

8 illustrates an example of an equalizer for compensating for distortion of a subcarrier channel according to the present embodiment.

Hereinafter, the operation of the equalizer 110 will be described with reference to FIG. 8, and some descriptions overlapping with those described in FIG. 2 or 7 may be omitted.

The equalizer 160 calculates a distortion vector based on the received pilot signal. The distortion vector may be calculated as r _n = (a _n , b _n ) = a _n + jb _n = h _n '.

② If the distortion vector is converted to polar coordinates, h _n '= (hi _n , hq _n ) = hi _n + jhq _n = M _n (hi _n M _n ^-1 + jhq _n M _n ^-1 ).

③ The equalizer 160 calculates the distortion compensation value using the distortion vector. The distortion compensation value is r _n '= (h _n ') ^-1 = M _n ^-1 (hi _n M _n ^-1 + jhq _n M _n ^{- 1} ), M _n ^-1 means 1 / (square root of I _n ² + Q _n ² ).

④ The equalizer 160 compensates the distortion of the data signal by applying the distortion compensation value r _n ′ to the data signal y _n . Distortion compensated data (z _n ) is z _n = y _n r _n '= (I _n , Q _n ) (a _n ', b _n ') = (I _n a _n' -Q _n b _n ', I _n b _n ' + Q _n a _n ') Can be displayed. As shown in FIG. 8, the equalizer 110 applies the first compensation value 830 to the I signal 810 of the data signal y _n including the distortion signal, and the data signal including the distortion signal. The second compensation value 840 is applied to the Q signal 820 of (y _n ), and the difference between two values to which each compensation value is applied is calculated to obtain the I 'signal 850 of the data signal whose distortion is compensated. Create

Also, the equalizer 110 is a second compensation value data signal (y _n) comprises applying (840), and a distortion signal to the I signal 810 of the data signal (y _n) comprising a distortion signal Q The first compensation value 830 is applied to the signal 820, and the sum of two values to which the respective compensation values are applied is calculated to generate the Q ′ signal 860 of the data signal whose distortion is compensated.

9 is an exemplary view illustrating a pilot signal for compensating for distortion of a subcarrier channel according to the present embodiment.

The pilot signal transmitted by the OFDM transmitter 110 according to the present embodiment is used when a time domain of one OFDM symbol is allocated among 255 OFDM symbols.

For example, as illustrated in FIG. 9, the OFDM transmitter 110 divides pilot signals for 128 subcarrier channels in a second time domain in each of 14 OFDM symbols. Here, the time domain including the pilot signal may be different for each OFDM symbol.

When the OFDM transmitter 110 includes all pilot signals for 128 subcarrier channels in one OFDM symbol and transmits the signals, peaks of the signal are generated and distortion occurs. Therefore, the pilot signal of the 128 subcarrier channels is determined. Transmit by dividing by the number of (eg, 14).

The equalizer 160 according to the present embodiment extracts the distortion vector H of the channel based on the pilot signal received through the subcarrier channel, and equalizes the data signal based on the distortion vector H. Here, the distortion vector H may include phase information and magnitude information of a signal carried in each subcarrier channel.

10 is an exemplary view illustrating a signal in which distortion is compensated for in an equalizer according to the present embodiment.

10A is a graph illustrating a signal of a subcarrier channel obtained by the equalizer 160 from the FFT 150. In other words, the graph of FIG.

10B is a graph illustrating a signal of a subcarrier channel output by correcting distortion in the equalizer 160. That is, the graph of FIG. 10B 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 above description is merely illustrative of the technical idea of the present embodiment, and those skilled in the art to which the present embodiment belongs may make various modifications and changes without departing from the essential characteristics of the present embodiment. Therefore, the present embodiments are not intended to limit the technical idea of the present embodiment but to describe the present invention, 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 interpreted by the following claims, and all technical ideas within the scope equivalent thereto should be construed as being included in the scope of the present embodiment.

<Description of the code>

110: OFDM transmitter 120: OFDM receiver

130: RF communication unit 140: ADC

150: FFT 160: equalizer

170: demodulator

210: pilot signal extractor 220: channel estimator

230: compensation value calculator 240: compensation value processor

250: distortion compensation unit

CROSS-REFERENCE TO RELATED APPLICATION

This patent application claims priority pursuant to United States Patent Law Section 119 (a) (35 USC § 119 (a)) of Patent Application No. 10-2016-0149028, filed with Korea on November 09, 2016. All content is incorporated by reference in this patent application. In addition, this patent application claims priority to countries other than the United States for the same reasons, all of which are incorporated herein by reference.

Claims (16)

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 which obtains an I / Q signal for a data signal from the data subcarrier channel and converts it into polar coordinates, and extracts a first amplitude and a first phase for the data subcarrier channel based on the polar coordinates; Acquiring an I / Q signal from a pilot channel included in the OFDM symbol to check a sequence of the pilot signal, and extracting an I / Q signal corresponding to a predetermined sequence value from the sequence of the pilot signal. A pilot sequence checking unit; A second coordinate system converter for converting an I / Q signal corresponding to the predetermined sequence value into polar coordinates and extracting a second amplitude and a second phase for the pilot channel based on the polar coordinates; A compensation value calculator configured to calculate a distortion compensation value based on the second amplitude and the second phase; A distortion compensator configured to compensate the first amplitude and the first phase based on the distortion compensation value; And A third coordinate system conversion unit configured to demodulate the first amplitude and the first phase, the distortion of which is compensated for, by the Cartesian coordinates; Equalizer comprising a. The method of claim 1, The pilot sequence confirmation unit, Identifies a sequence of the pilot signal input in the order of + (Positive), + (Positive),-(Negative), and 0 (Zero), and I of the pilot signal having a positive sequence value among the pilot sequences. Equalizer, characterized in that for extracting the / Q signal and transmits to the second coordinate system conversion unit. The method of claim 1, A fourth coordinate system conversion unit for obtaining an I / Q signal from the pilot channel, converting the polarity into polar coordinates, and extracting a third amplitude and a third phase for the pilot channel based on the polar coordinates; And the distortion compensator compensates for the third amplitude and the third phase based on the distortion compensation value. The method of claim 3, wherein And a monitoring unit configured to monitor the distortion compensation of the data subcarrier channel by obtaining a third amplitude and a third phase in which the distortion is compensated from the distortion compensator. The method of claim 4, wherein The monitoring unit, And checking a bit error rate (BER) for the third amplitude and the third phase, in which the distortion is compensated, to monitor the state or accuracy of the distortion compensation. The method of claim 1, The pilot channel, And a plurality of data subcarrier channels, wherein the distortion compensator compensates for amplitude and phase for each of the plurality of data subcarrier channels using the distortion compensation value. The method of claim 1, The first coordinate system conversion unit and the second coordinate system conversion unit, Equalizer, characterized in that for converting the I / Q signal of the data signal to the polar coordinates based on a Coordinate Rotation DIgital Computer (CORDIC) algorithm. The method of claim 1, The compensation value calculator, An amplitude compensation value determiner configured to accumulate the second amplitude and calculate an moving average value with respect to the accumulated second amplitude to determine an amplitude compensation value; And A phase compensation value determiner configured to accumulate the second phase, calculate a moving average value for the accumulated second phase, and determine a phase compensation value; The distortion compensation value comprises the amplitude compensation value and the phase compensation value. The method of claim 8, The distortion compensator, An amplitude compensator configured to compensate for the distortion of the first amplitude by applying the amplitude compensation value to the first amplitude; And And a phase compensator configured to compensate the distortion of the first phase by applying the phase compensation value to the first phase. The method of claim 9, The amplitude compensation unit, And a mixer (Mixer) mixing the amplitude compensation value and the first amplitude. The method of claim 9, The phase compensator, An equalizer to compensate for the distortion of the first phase by adding the phase compensation value to the first phase. A method for compensating for distortion of a data subcarrier channel included in an OFDM symbol, A first coordinate system conversion process of obtaining an I / Q signal for a data signal from the data subcarrier channel and converting the signal to polar coordinates and extracting a first amplitude and a first phase for the data subcarrier channel based on the polar coordinates; Acquiring an I / Q signal from a pilot channel included in the OFDM symbol to check a sequence of the pilot signal, and extracting an I / Q signal corresponding to a predetermined sequence value from the sequence of the pilot signal. Pilot sequence checking; A second coordinate system conversion process of converting an I / Q signal corresponding to the predetermined sequence value into polar coordinates and extracting a second amplitude and a second phase for the pilot channel based on the polar coordinates; Calculating a compensation value based on the second amplitude and the second phase; A distortion compensation process of compensating the first amplitude and the first phase based on the distortion compensation value; And A third coordinate system transformation process of converting the first amplitude and the first phase, the distortion of which is compensated for, to a rectangular coordinate, to demodulate Compensating for the distortion of the subcarrier channel comprising a. The method of claim 12, The compensation value calculation process, An amplitude compensation value determining step of accumulating the second amplitude and calculating a moving average value for the accumulated second amplitude to determine an amplitude compensation value; And Accumulating the second phase, calculating a moving average value with respect to the accumulated second phase, and determining a phase compensation value; And the distortion compensation value comprises the amplitude compensation value and the phase compensation value. The method of claim 13, The distortion compensation process, An amplitude compensation process of compensating for distortion of the first amplitude by applying the amplitude compensation value to the first amplitude; And And applying a phase compensation value to the first phase to compensate for the distortion of the first phase. The method of claim 12, A fourth coordinate system conversion process of acquiring an I / Q signal from the pilot channel and converting the signal to polar coordinates and extracting a third amplitude and a third phase for the pilot channel based on the polar coordinates, And the distortion compensating step compensates for the third amplitude and the third phase based on the distortion compensation value. The method of claim 15, And monitoring the distortion compensation of the data subcarrier channel by acquiring the third amplitude and the third phase whose distortion is compensated for in the distortion compensation process. .

Images