WO2012067424A2 - Apparatus and method for transceiving data - Google Patents

Abstract

A data transmitting apparatus generates a plurality of pilot signals to be used in channel estimation in a data receiving apparatus, performs symbol mapping of a plurality of input data signals and a plurality of pilot signals to generate a plurality of data symbols and a plurality of pilot symbols, converts input symbols of a frequency domain including the plurality of data symbols and the plurality of pilot symbols, into real signals of a time domain and performs angle modulation of the real signals. The data transmitting apparatus controls the sizes of sine signals for the angle-modulated real signals by a variable gain in accordance with a control signal, and transmits the real signals.

Description

Data transmitting and receiving device and method

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for transmitting and receiving data, and more particularly, to a peak-to-average power ratio in a communication system for transmitting data using an orthogonal frequency division multiplexing (OFDM) scheme. An apparatus and method for transmitting and receiving data for controlling a PAPR).

Orthogonal Frequency Division Multiplexing (OFDM), which can be implemented through a simple equalizer, has strong characteristics of multipath fading, and thus can be implemented in a wireless local area network (WLAN), a wireless metropolitan area network (WMAN). ), And are being used in various wireless communication systems such as digital audio broadcast (DAB) and digital video broadcast (DVB).

However, because OFDM uses multiple carriers, in-phase signals are combined to generate a high average peak-to-average power ratio (PAPR) of up to 12dB, and due to high PAPR, the power amplifier of the OFDM transmitter The operating point of the amplifier is located in the nonlinear region, which causes nonlinear distortion of the signal. Therefore, in an OFDM system, the power amplifier is backed off to reduce the effect of PAPR. If the power amplifier is not backed off sufficiently, the frequency spectrum of the system is widened and distortion due to inter-frequency modulation occurs. As a result, system performance is degraded. Therefore, it is essential to lower the PAPR for power efficiency and miniaturization of the OFDM transmitter.

By combining a phase modulation (PM) or frequency modulation (FM) scheme with an OFDM scheme having a high PAPR of up to 12 dB, the PAPR can be reduced to 0 dB.

The combination of the OFDM and PM and FM schemes reduces the reception performance in a channel with multiple paths. The FM scheme has a wider required frequency band and the degradation of the reception performance is more severe than that of the PM scheme. There is this.

In addition, in the case of visible light wireless communication using VLC, it is effective to reduce the PAPR to 0 dB. However, in the case of non-infrared light communication, the PAPR needs to be increased for reception performance. Thus, uniform PAPR control degrades system performance.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a data transmission / reception apparatus and method capable of lowering PAPR in a system for transmitting data using an OFDM scheme and ensuring stable reception performance in a multipath channel.

According to an embodiment of the present invention, an apparatus for transmitting data is provided. The data transmission apparatus includes a pilot generator, a symbol mapping unit, a real signal converter, an angular modulator, a PAPR control and power normalizer, and a signal transmitter. The pilot generator generates at least one pilot signal to be used for channel estimation in the data receiving apparatus. The symbol mapping unit generates a plurality of data symbols and at least one pilot symbol by symbol mapping a plurality of data signals and the at least one pilot signal. The real signal converter converts an input symbol in a frequency domain including the plurality of data symbols and the at least one pilot symbol into a real signal in a time domain. An angular modulator angulates the real signal. The PAPR control and power normalization unit adjusts the magnitude of the sine component of the angularly modulated real signal according to the first gain and varies the first gain according to the input signal. The signal transmitter converts the adjusted real signal into a radio frequency signal for transmission.

The apparatus for transmitting data further includes a symbol arranging unit, wherein the symbol arranging unit sets pilot symbols corresponding to each of a plurality of data symbol groups each including at least one data symbol, and one data symbol of each data symbol group; Two symbols are generated using the pilot symbols and arranged in each data symbol group and output to the real signal converter.

The symbol arranging unit may generate one of the two symbols by adding the one data symbol and the pilot symbol, and generate the other one of the two symbols by subtracting the one data symbol and the pilot symbol. have.

The angular modulator may include a phase controller for controlling the magnitude of the real signal in accordance with a second gain, and a modulator for angularly modulating the real signal into a cosine signal and a sine signal.

The real signal converting unit includes: a normalizing unit for normalizing the input symbol so that the average power of the input symbol is 1, an inverse fast Fourier transform unit for inverse fast Fourier transform on a plurality of input signals, and the input symbol and the input symbol And an input signal processor configured to input a conjugate complex symbol obtained by conjugate complex conversion to the inverse fast Fourier transform unit.

The PAPR control and power normalization unit is a PAPR controller for controlling the magnitude of the sine component of the angularly modulated real signal according to the first gain, and multiplies a cosine component of the real signal by a set value for normalization to obtain a baseband I signal. A first multiplier to generate and a second multiplier to generate a baseband Q signal by multiplying the set value by a sine component of the real signal whose magnitude is controlled in accordance with the first gain, wherein the first gain is 1 In this case, PAPR can be zero.

According to another embodiment of the present invention, an apparatus for receiving data is provided. The data receiving apparatus includes a power compensator, an angular demodulator, a normalized and real signal inverse transform unit, a pilot extractor, a channel estimator, a channel equalizer, and a symbol demapping unit. The power compensator compensates for the size of the baseband signal corresponding to the received data corresponding to the size adjusted by the data transmission apparatus for the PAPR control. The angular demodulator angulates the baseband signal with the magnitude compensated. The normalized and real-signal inverse transform unit converts each demodulated signal into a plurality of parallel symbols in the frequency domain in the time domain through a fast Fourier transform. The pilot extractor extracts pilot symbols and data symbols from the parallel symbols. The channel estimator estimates a channel using the pilot symbol. The channel equalizer compensates for the channel using the estimated channel. The symbol demapping unit performs symbol demapping on the data symbols to generate a plurality of data signals to restore data.

The demodulation unit may include a phase estimator for calculating a phase estimate value of the baseband signal, and a phase compensator for compensating a phase of the baseband signal from the phase estimate value.

The phase estimator may calculate an average value of the phase of the baseband signal and calculate the phase estimate value by using an inverse tangent of the average value.

The phase estimator may calculate the phase estimation value by using an inverse tangent after filtering the baseband signal.

The pilot extractor may obtain location information of two symbols generated by using a pilot symbol in the data transmission apparatus from the parallel symbol, and extract a pilot symbol and a data symbol using two symbols corresponding to the location information. .

The power compensator may include two multipliers for compensating the magnitudes of the I and Q signals of the baseband signal, and a PAPR controller for dividing and outputting the Q-compensated Q signal by gain, wherein the gain may be varied. have.

The real-signal inverse transform unit includes a fast Fourier transform unit for generating a parallel symbol by performing fast Fourier transform on a plurality of input signals, a serial-parallel converter for converting the demodulated baseband signal from a serial signal to a parallel signal, and The signal processing unit may output a portion of the parallel symbol to the demapping unit.

According to another embodiment of the present invention, a method for transmitting data by a data transmission device is provided. The data transmission method may include generating a plurality of pilot signals to be used for channel estimation in a data receiving apparatus, generating a plurality of data symbols and a plurality of pilot symbols by symbol mapping a plurality of input signals and the plurality of pilot signals; Converting an input symbol in a frequency domain including the plurality of data symbols and the plurality of pilot symbols into a real signal in a time domain in a frequency domain, angularly modulating the real signal, and a angular modulated signal according to a gain And controlling the magnitude of the sine signal for the signal, and converting the angulated real signal into a radio frequency signal.

The generating may include setting a pilot symbol corresponding to each of a plurality of data symbol groups each including at least one data symbol, and using two data symbols and one pilot symbol of each data symbol group. And generating the two symbols in each data symbol group.

The controlling may include varying the gain according to an input control signal.

According to another embodiment of the present invention, a method for receiving data by a data receiving apparatus is provided. A data receiving method includes compensating a magnitude of a baseband signal corresponding to received data, angularly demodulating the baseband signal, and performing a plurality of parallel symbols in a frequency domain in a time domain through fast Fourier transforming the demodulated signal. Converting to P, extracting pilot symbols and data symbols from the parallel symbol, compensating the estimated channel using the pilot symbols, and recovering the received data by symbol demapping the data symbols. Include.

The demodulating may include estimating the phase of the baseband signal and compensating for the phase of the baseband signal using a phase estimation value.

The extracting may include obtaining location information of two symbols generated using a pilot symbol in a data transmission apparatus, and extracting pilot symbols and data symbols using two symbols corresponding to the location information. can do.

According to an embodiment of the present invention, by modulating and transmitting data by combining the OFDM scheme with the PM scheme, the PAPR can be lowered to 0 dB, and the PAPR can be changed according to a reception environment, thereby improving reception performance. Therefore, a service considering both PAPR and reception performance may be enabled without changing a transmitter specification in a multipath channel. For example, in the case of visible light wireless communication using lighting, the control may prevent flicker by controlling the PAPR to 0 dB, and in the case of communication using wireless light rather than infrared light, the PAPR may be increased to improve reception performance.

1 is a diagram illustrating an OFDM transmitter according to an embodiment of the present invention.

2 is a flowchart illustrating a signal transmission method of an OFDM transmission apparatus according to an embodiment of the present invention.

3 is a diagram illustrating an example of a pilot generation unit illustrated in FIG. 1.

4 is a diagram illustrating an example of a method for generating a pilot signal.

FIG. 5 is a diagram illustrating an example of a symbol mapped by a symbol mapping unit of FIG. 1.

FIG. 6 is a diagram illustrating an example of a symbol normalized by the symbol mapping unit of FIG. 1.

FIG. 7 is a diagram illustrating an example of a data symbol grouping method performed by the pilot arrangement unit illustrated in FIG. 1.

FIG. 8 is a diagram illustrating an example of a method of arranging data symbols and pilot symbols performed by the pilot arranging unit shown in FIG. 1.

9 is a diagram illustrating a real signal converter shown in FIG. 1.

FIG. 10 is a view illustrating an angular modulator shown in FIG. 1.

11 is a diagram illustrating a phase magnitude distribution of an input signal of each modulator.

12 is a diagram illustrating a phase magnitude distribution of an output signal of each modulator.

FIG. 13 is a diagram illustrating a PCPN shown in FIG. 1.

14 is a diagram illustrating an OFDM receiver according to an embodiment of the present invention.

15 is a flowchart illustrating a data receiving method of an OFDM receiver according to an embodiment of the present invention.

16 is a diagram illustrating an example of a reception signal processor illustrated in FIG. 14.

17 is a diagram illustrating a power compensator shown in FIG. 14.

18 is a diagram illustrating an angle demodulator shown in FIG. 10.

19 and 20 are diagrams illustrating a phase estimator illustrated in FIG. 18, respectively.

FIG. 21 is a diagram illustrating the phase compensator illustrated in FIG. 18.

FIG. 22 is a diagram illustrating a real signal converter shown in FIG. 14.

FIG. 23 is a diagram illustrating a pilot extraction method of the pilot extraction unit illustrated in FIG. 14.

24 is a diagram illustrating a channel estimator illustrated in FIG. 14.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification and claims, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise.

An apparatus and method for transmitting and receiving data according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an OFDM transmitter according to an embodiment of the present invention, and FIG. 2 is a flowchart illustrating a signal transmission method of an OFDM transmitter according to an embodiment of the present invention.

Referring to FIG. 1, the OFDM transmitter 100 may include a serial to parallel converter (SPC) 110, a pilot generator 120, a symbol mapper 130, and a pilot arrangement. The unit 140, real signal converter 150, angle modulation unit 160, peak to average power ratio (PAPR) control and power normalization unit , PCPN) and a signal transmitter 180.

2, when a plurality of serial data signals corresponding to bit data are input, the SPC 110 converts the plurality of serial data signals into a plurality of parallel data signals (S201).

The pilot generator 120 generates at least one pilot signal to be used for channel estimation and channel equalization in the OFDM receiver (S203).

The symbol mapping unit 130 performs symbol mapping on a plurality of parallel data signals and at least one pilot signal through digital modulation such as binary phase shift keying (BPSK), quadrature amplitude modulation (QAM), 16-QAM, 64-QAM, and the like. In operation S205, a plurality of data symbols and at least one pilot symbol are generated.

The pilot arranging unit 140 arranges at least one pilot symbol and a plurality of data symbols to facilitate channel estimation (S207).

The real signal converting unit 150 performs an Inverse Fast Fourier Transform (IFFT) on at least one pilot symbol and a plurality of data symbols, and converts the real signal into a real signal in the time domain in step S209. The NRSC 130 converts the real signal in the time domain into a serial signal (S211).

The angular modulator 160 angularly modulates the real signal to adjust the magnitude of the real signal (S213). Phase modulation (PM) can be used as the angular modulation method.

The PCPN 170 controls the PAPR by adjusting the magnitude of the sine component of the angularly modulated real signal according to the gain (S215) and normalizes the power (S217).

Next, the signal transmitter 180 multiplies the real component of the power normalized signal by A, multiplies the imaginary component of the power normalized signal by B, and then adds the two components to convert the power normalized signal into a radio frequency signal (S219). . In this case, A may be cos (2πf _c t) or sin (2πf _c t), and B may be cos (2πf _c t) or sin (2πf _c t), which may be different from A. f _c is the radio frequency. In FIG. 1, A is cos (2πf _c t) and B is sin (2πf _c t). Alternatively, the signal transmitter 180 may multiply -B by an imaginary component of the power normalized signal.

The signal transmitter 160 transmits a radio frequency signal (S221). The radio frequency signal transmitted from the OFDM transmitter 100 may be defined as an OFDM signal.

Next, the OFDM transmitter 100 will be described in detail with reference to FIGS. 3 to 9.

3 is a diagram illustrating an example of a pilot generation unit illustrated in FIG. 1, and FIG. 4 is a diagram illustrating an example of a method of generating a pilot signal.

The pilot generator 120 may use a Pseudo Random Noise (PN) code, which may reproduce noise while having similar noise characteristics to that of a random sequence, to generate a pilot signal. In this case, the pilot generation unit 120 may include a PN code generator 121 consisting of shift registers 1211, 1213, 1215, an operator 1217, and a bit processing unit 123, as shown in FIG. 3. have. Alternatively, the pilot generator 120 may be used to generate a pilot signal by receiving the PN code generated from the PN code generator.

Shift registers 1211, 1213, and 1215 shift the input signal. The operator 127 performs an exclusive OR (XOR) operation on the two input signals. That is, the operator 127 outputs 0 when the bits of the two input signals are the same, and outputs 1 when the bits of the two input signals are different.

The bit processor 123 selects a pilot signal from the PN code.

For example, assuming that the initial values R1, R2, R3 of the shift registers 121, 123, 125 are (1, 1, 1), the repetition period is 7 (= 2 ^m -1), and PN As for the PN code output from the code generator 121, "1 1 1 0 1 0 0" is output. Where m is the number of shift registers. If the number of pilot signals is 5, 5 bits, i.e., "1 1 1 0 1", are selected from the 7-bit PN code "1 1 1 0 1 0 0", and "1 1 1 0 1" is respectively used as a pilot signal. Set it.

The bit processor 123 may generate a plurality of PN codes for base station division by shifting the PN codes by one bit (phase offset) for base station division. For example, when the PN code is "1 1 1 0 1 0 0", seven PN codes may be generated as shown in FIG. 4, and each pilot is selected by a bit corresponding to the number of pilots in each PN code. Is set to the signal.

5 is a diagram illustrating an example of a symbol mapped by the symbol mapping unit of FIG. 1, and FIG. 6 is a diagram illustrating an example of symbols normalized by the symbol mapping unit of FIG. 1.

The symbol mapping unit 130 maps a plurality of parallel data signals and at least one pilot signal to data symbols and pilot symbols representing positions in constellations according to modulation schemes such as BPSK, QAM, 16-QAM, and 64-QAM. In addition, the mapped data symbols and pilot symbols may be the same as FIG. 5. That is, the mapped symbols are complex signals.

In addition, the symbol mapping unit 130 normalizes data symbols and pilot symbols. In order to normalize the data symbols and the pilot symbols, the symbol mapping unit 130 obtains an average value by taking an absolute value on the input symbol, squares it, obtains a square root of the obtained average value, and divides the input symbol by the square root to obtain an average power. Data symbols and pilot symbols can be normalized to be one. For example, when the symbol mapped by the symbol mapping unit 130 is the same as FIG. 5, the average value is 10 (=

) To the input symbol

By multiplying the input symbols can be normalized, the normalized symbol can be shown as shown in FIG.

FIG. 7 is a diagram illustrating an example of a data symbol grouping method performed by the pilot arranging unit illustrated in FIG. 1, and FIG. 8 is a diagram illustrating a method of arranging data symbols and pilot symbols performed by the pilot arranging unit illustrated in FIG. 1. An example is shown.

The pilot symbol is used for channel equalization of data symbols, and the pilot placement unit 240 determines a group of data symbols to be channel equalized using each pilot symbol. The number of data symbol groups corresponds to the number of file symbols.

When the number of pilot symbols is five, the pilot arranging unit 140 groups the plurality of data symbols into five data symbol groups. For example, as shown in FIG. 7, the pilot placement unit 140 may select the first three data symbols as a group of data symbols to be channel equalized using the first pilot symbol, and use the second pilot symbol. The next seven data symbols can be selected as the group of data symbols to be channel equalized. The pilot placement unit 140 may select the last 15 data symbols as a group of data symbols to be channel equalized using the fifth pilot symbol.

Next, the pilot placement unit 140 selects one data symbol from each data symbol group, and adds and subtracts the pilot symbol and the selected data symbol corresponding to each data symbol group to generate two new data symbols. For example, if the pilot symbol is symbol 1 and the selected data symbol is 3 + j * 5, the pilot symbol plus the data symbol is 4 + j * 5 and the pilot symbol minus the data symbol is 2-j * 5. Can be. Alternatively, the pilot symbol may be added to or subtracted from the selected data symbol. In this case, the data symbol added with the pilot symbol is 4 + j * 5, and the pilot symbol and the subtracted data symbol are 2 + j * 5.

As such, when two new data symbols are generated, the pilot placement unit 140 respectively generates two new data symbols for normalization.

Divide by, and place the two data symbols generated in any position of each group. For example, the pilot placement unit 240 may arrange two new data symbols at arbitrary positions as shown in FIG. 8. In this way, each data symbol group is increased by one data symbol.

9 is a diagram illustrating a real signal converter shown in FIG. 1.

Referring to FIG. 9, the real signal converter 150 includes an input signal processor 151, an IFFT unit 153, a parallel to serial converter (PSC) 155, and a multiplier 157. do.

The input signal processor 151 converts the input data symbols and the pilot symbols into the real signals in the time domain in the frequency domain, and converts the input data symbols and pilot symbols into the input signals X (0), of the IFFT unit 153. X (1),... , X (N-1), X (N), X (N + 1),... , X (2N-1)]. Here, N (exponential power of 2) represents the number of symbols, and when the number of symbols is N, the size of the IFFT may be 2N.

That is, the input signal processor 151 inputs the input signals X (0), X (1),... Of the IFFT unit 153. , X (N-1), X (N), X (N + 1),... , X (2N-1)] using N data symbols and input signals [X (N), X (N + 1),... Of the IFFT unit 153. , X (2N-1)] is used by conjugate conjugated N data symbols. The 0th data symbol is 0, so that the data symbols inputted to the input signals X (0) and (X (N)] become 0. That is, the input signals X (1), ..., X (N- 1)], N data symbols are used, and with the input signals [X (N + 1), ..., X (2N-1)], data symbols of the input signals [X (2N-k)] are conjugate-conjugated. Where k is N + 1, N + 2, ..., 2N-1.

Input signal to IFFT unit 153 [(X (0), X (1), ..., X (N-1), X (N), X (N + 1), ..., X (2N-1)] Is input, the IFFT unit 153 inputs the input signal [(X (0), X (1), ..., X (N-1), X (N), X (N + 1), ..., X (2N). -1)], where the data symbols and pilot symbols, i.e., the input symbols, are real-time signals [(X '(0), X' (1), ..., X '(N-1) in the frequency domain in the frequency domain. ), X '(N), X' (N + 1), ..., X '(2N-1)].

The PSC 155 converts a real time signal in a time domain from a parallel signal to a serial signal.

The multiplier 157 is applied to the real signal in series

Normalize by multiplying

FIG. 10 is a diagram illustrating an angular modulator illustrated in FIG. 1, FIG. 11 is a diagram illustrating a phase magnitude distribution of an input signal of each modulator, and FIG. 12 is a diagram illustrating a phase magnitude distribution of an output signal of each modulator.

Referring to FIG. 10, each modulator 160 includes a phase controller 161 and a modulator 163.

The phase controller 161 receives a normalized real signal from the real signal converter 150 as an input signal IN. The phase controller 161 varies the gain G1 to adjust the magnitude of the input signal IN so that the magnitude of the input signal IN is in the range of −π / 2 to π / 2. Where π is the circumference.

For example, when the phase magnitude of the input signal IN of the phase controller 161 is equal to that of FIG. 11, the phase controller 161 may be configured such that the magnitude of the input signal IN is in the range of −π / 2 to π / 2. The input signal IN may be multiplied by a gain of 0.4 to adjust the size of the input signal IN. Then, as illustrated in FIG. 12, the phase magnitude of the input signal IN may be in the range of −π / 2 to π / 2.

The modulator 163 angulates the real signal adjusted by the phase controller 161 into a cosine signal and a sine signal [cos (IN), sin (IN)].

FIG. 13 is a diagram illustrating a PCPN shown in FIG. 1.

Referring to FIG. 13, the PCPN 170 includes a PAPR controller 171 and multipliers 173 and 175. The multipliers 173 and 175 can operate as a power normalizer for power normalization.

The cosine signal cos (IN), which is an output signal of the modulator 163, is represented as a (t) in FIG. 13 for convenience.

The cosine signal [a (t)], which is the output signal of the modulator 163, is input to the multiplier 173 without passing through the PAPR controller 171, and the sine signal [sin (IN)] that is the output signal of the modulator 163 is It is input to the PAPR controller 171.

The PAPR controller 171 controls the gain G2 according to the input control signal, and adjusts the magnitude of the sine signal sin (IN) input according to the gain G2. In this case, the control signal may include a gain value to be controlled.

That is, the PAPR controller 171 controls the PAPR by adjusting only the magnitude of the sine component of the angularly modulated real signal. The sine signal b (t) adjusted by the PAPR controller 171 is input to the multiplier 175.

In general, the PAPR in one OFDM symbol is represented by Equation (1). The guard period is inserted into the time-domain serial signal output from the real signal converter 150, and the guard period and the signal corresponding to one data symbol (or pilot symbol) are combined to be called an OFDM symbol.

[Equation 1]

Here, E {.} Represents an expected value, and T represents a period of one OFDM symbol.

In this case, the PAPR (dB) according to the embodiment of the present invention may be expressed as Equation 2 and Equation 2.

[Equation 2]

[Equation 3]

In Equation 3, Gain represents the gain G2 of the PAPR controller 171, and when the gain becomes 1, the PAPR becomes 0 dB.

In particular, as can be seen from Equation 3, the PAPR varies depending on the gain. That is, since the control of the gain G2 is possible in the PAPR controller 171 using the control signal according to the reception environment, the control of the PAPR may be possible accordingly.

For example, the gain G1 of the phase controller 161 shown in FIG. 10 is 0.4, the size of the IFFT is 2048, and for 16QAM modulation, the PAPR is the gain G2 of the PAPR controller 171 as shown in Table 1 below. ) May vary.

TABLE 1

The cosine signal a (t) and the scaled sine signal b (t) are multiplied by the value of C for power normalization. C is the same as Equation 4.

[Equation 4]

That is, the multiplier 173 multiplies the cosine signal a (t) by C to power normalization, and the multiplier 175 multiplies the sine signal b (t) by C to power normalize.

If the power normalized cosine signal is called a baseband I signal and the power normalized sine signal is called a baseband Q signal, cos (2πf _c t) and sin (2πf _c t) are applied to the baseband I signal and the baseband Q signal, respectively. Multiply by and add to convert to a radio frequency signal.

14 is a diagram illustrating an OFDM receiver according to an embodiment of the present invention, and FIG. 15 is a flowchart illustrating a data receiving method of an OFDM receiver according to an embodiment of the present invention.

Referring to FIG. 14, the OFDM receiver 200 includes a received signal processor 210, a power compensator 220, an angle demodulation unit 230, and a real signal de-converter ( 240, a pilot extractor 250, a channel estimator 260, a channel equalizer 270, a symbol demapping unit 280, and a PSC 290. The OFDM receiver 200 performs the reverse operation of the OFDM transmitter 100.

Referring to FIG. 15, when the reception signal processing unit 210 receives an OFDM signal as received data, the reception signal processor 210 multiplies the real component of the OFDM signal by A 'and multiplies the imaginary component of the power normalized signal by B', and then converts the signal through analog-to-digital conversion. A bandband analog signal is converted into a plurality of baseband digital signals (S1502). Here, A 'and B' may be the same as A and B of the OFDM receiver 100, and B 'may be -B. A 'may be cos (2πf _c t) or sin (2πf _c t), and B' may be cos (2πf _c t) or sin (2πf _c t), which may be different from A '. f _c is the radio frequency.

The power compensator 220 compensates for the size adjusted by the PAPR controller 171 with respect to the plurality of baseband digital signals (S1504).

Each demodulator 230 demodulates a plurality of baseband digital signals whose magnitude is compensated by the power compensator 220 (S1506).

The real signal inverse transform unit 240 converts each demodulated signal from a serial signal into a parallel signal (S1508) and performs a fast Fourier transform (FFT) on the converted parallel signal, thereby converting the frequency domain from the parallel signal in the time domain. Convert to a parallel symbol (S1510).

The pilot extractor 250 extracts the pilot symbols from the parallel symbols in the frequency domain (S1512).

The channel estimator 260 estimates a channel using the extracted pilot symbols (S1514).

The channel equalizer 270 compensates for the distortion due to the channel by using the channel estimated from the data symbols of each data symbol group (S1516).

The symbol demapping unit 280 performs symbol demapping through digital demodulation such as BPSK, QAM, 16-QAM, 64-QAM, etc. in parallel data symbols in a frequency domain in which distortion by a channel is compensated by the channel equalizer 270. In operation S1518, a plurality of parallel data signals are generated.

The PSC 290 converts the plurality of parallel data signals output from the symbol demapping unit 280 into a plurality of serial data signals and outputs the converted serial data signals (S1520), thereby restoring the OFDM signals to the data signals.

Next, the OFDM receiver 200 will be described in detail with reference to FIGS. 16 to 22.

16 is a diagram illustrating an example of a reception signal processor illustrated in FIG. 14.

Referring to FIG. 16, the reception signal processor 210 includes a multiplier 211 and 213, a low pass filter (LPF) 215 and 217, and an analog to digital converter (ADC) 219. It includes.

The multiplier 211 multiplies the received OFDM signal by A ', converts it to a cosine signal or a sine signal, and outputs the result to the LPF 215. In FIG. 16, A ′ is shown as cos (2πf _c t). In this case, the signal output from the multiplier 211 may be a cosine signal.

The multiplier 213 multiplies the received OFDM signal by B ', converts it to a cosine signal or a sine signal, and outputs the result to the LPF 217. In FIG. 16, B ′ is illustrated as sin (2πf _c t), and the signal output from the multiplier 211 may be a sine signal.

Here, A 'may be cos (2πf _c t) or sin (2πf _c t), and B' may be cos (2πf _c t) or sin (2πf _c t), which may be different from A '. The LPFs 215 and 217 respectively filter cosine signals and sinusoidal signals input from the multipliers 211 and 213, and pass only signals of a desired band in the input signal.

The ADC 219 converts the cosine signal and the sine signal passing through the LPFs 215 and 217 into a digital baseband I signal and a digital baseband Q signal through analog to digital conversion, and then the digital baseband I signal and the digital baseband. Outputs the Q signal.

On the other hand, in the OFDM transmitter 100, when the signal multiplied by the baseband Q signal [cos (2πf _c t) or sin (2πf _c t)] is multiplied by a negative sign, the ADC 219 outputs the digital basis. You can multiply the band Q signal by the minus sign.

17 is a diagram illustrating a power compensator shown in FIG. 14.

Referring to FIG. 17, the power compensator 220 includes multipliers 221 and 223 and a PAPR controller 225.

The multiplier 221 multiplies the digital baseband I signal output from the reception signal processor 210 by D to compensate and output power to the baseband I signal.

The multiplier 223 multiplies the digital baseband Q signal output from the reception signal processor 210 by D to compensate for power, and outputs the power to the PAPR controller 225.

Here, D may be represented as in Equation 5.

[Equation 5]

Here, T means a period of the OFDM symbol.

Denotes an estimate of the cosine signal (a (t) in FIG. 13) in the OFDM transmitter 100,

Denotes an estimate of a sine signal (sin (IN (t)) in FIG. 13) in the OFDM transmitter 100. FIG. Gain also represents the gain G1 of the phase controller 161 of FIG.

And

Since the IFFT signal is a random signal cannot be accurately obtained. Therefore, the error can be reduced by averaging over and over again, and the estimate according to the gain G1 of the phase controller 161 of FIG. 10 of the OFDM transmitter 100 may be as shown in Table 2.

TABLE 2

PAPR controller 225 divides the power-compensated signal by multiplier 221 by the gain G3 of PAPR controller 223 and outputs a baseband Q signal. It is equal to the gain G2 of the PAPR controller 171 of the gain G3 of the PAPR controller 225. For example, if the gain G1 of the phase controller 141 of FIG. 10 is 0.4 and the gain G3 of the PAPR controller 225 is 2, D is 1.179. Dividing the baseband Q signal by 1.179 multiplied by 2 produces a power compensated baseband Q signal.

FIG. 18 is a diagram illustrating an angular demodulator shown in FIG. 10, FIGS. 19 and 20 are diagrams illustrating a phase estimator illustrated in FIG. 18, and FIG. 21 is a diagram illustrating a phase compensator illustrated in FIG. 18.

Referring to FIG. 18, the angle demodulator 230 includes a phase estimator 231 and a phase compensator 233.

The phase estimator 231 performs phase estimation to compensate for the phase distortion.

Referring to FIG. 19, the phase estimator 231 includes an average calculator 2311 and a phase calculator 2313.

The average calculator 2311 calculates an average of the input baseband signals (

) For example, if the size of the IFFT is N, the baseband signal inputted by N phases divided by N and then averaged (

) Can be calculated.

The phase calculator 2313 has an average (

Using the inverse tangent of

Calculate

Is the average (

Average the imaginary components of

Can be calculated from the inverse tangent of the division by the real component of

[Equation 6]

As such, the phase estimate (

) Is the average of the baseband signals (

It can be obtained using), but it can also be obtained in other ways.

Referring to FIG. 20, the phase estimator 231 ′ may include an LPF 2311 ′ and a phase calculator 2313 ′.

The LPF 2311 'filters the input baseband signal so that the low band signal (

)

The phase calculator 2313 ′ may generate a low band signal such as (7).

Using the inverse tangent of

) Can be calculated.

[Equation 7]

Again, referring to FIG. 18, the phase compensator 233 determines the phase estimate value (

To compensate for the distorted phase.

Referring to FIG. 21, the phase compensator 233 includes a phase calculator 2331, a controller 2333, an adder 2335, and a controller 2337.

The phase calculator 2331 is configured to input the phase of the input baseband signal (

) And the phase (

Using the inverse tangent of

)

The controller 2333 is a phase estimate value from the phase estimator 231 or 231 '.

), And multiplies by -1 to output it.

The adder 2335 is a phase estimate (

) And the output value of the controller 2333 are added.

That is, the controller 2333 and the adder 2335 may calculate the phase estimate value of the phase calculator 2331.

From the phase estimator 231 or 231 '

Subtract).

The controller 2237 is a phase estimate value of the phase calculator 2331 (

From the phase estimator 231 or 231 '

By dividing) by the gain G4, the distortion-compensated phase P is output. Here, the gain G4 may be equal to the gain G1 of the phase controller 161.

FIG. 22 is a diagram illustrating a real signal converter shown in FIG. 14.

Referring to FIG. 22, the real signal converter 240 includes a multiplier 241, an SPC 243, an FFT unit 245, and a signal processor 247.

The multiplier 241 is applied to the real signal P output from each demodulator 230.

After multiplying by and normalizing, output to SPC 243.

The SPC 243 converts the signal normalized by the multiplier 241 from the serial signal to the parallel signal and outputs the normalized signal to the FFT unit 245.

The parallel signals converted by the SPC 253 are input signals P (0), P (1),... Of the FFT unit 245. , P (N-1), P (N), P (N + 1),... , P (2N-1)], the FFT unit 245 receives the input signals P (0), P (1),... , P (N-1), P (N), P (N + 1),... , P (2N-1)] is FFTed. Then, the input signals P (0), P (1),... , P (N-1), P (N), P (N + 1),... , P (2N-1)] in the frequency domain in the frequency domain data symbols [X (0), X (1),... , X (N-1), X (N), X (N + 1),... , X (2N-1)].

The signal processor 247 performs data symbols [(X (0), X (1), ..., X (N-1), X (N), X (N + 1), ..., X (2N-) in the frequency domain. 1)] and outputs a signal in the frequency domain [(X (0), X (1), ..., X (N-1)] to the symbol demapping unit 260. At this time, the signal processing unit 247 outputs data. The symbols [(X (0), X (1), ..., X (N-1)) may be output as it is to the pilot extractor 250. The signal processor 247 may output data symbols [X (in the frequency domain). N + 1),..., X (2N-1)] may be complex conjugated and then relocated to the pilot extractor 250 by relocating the data symbol at the position of X (2N-k). Here, k is N + 1, N + 2, ..., 2N-1 For example, in the case of a symbol [X (2N-1)] in the frequency domain after FFT, the signal processing unit 247 is a frequency. The symbol X (2N-1) of the region can be rearranged at the position of X (1) after complex conjugate conversion.

FIG. 23 is a diagram illustrating a pilot extraction method of the pilot extraction unit illustrated in FIG. 14.

Referring to FIG. 23, the pilot extractor 250 adds, from a plurality of data symbols input in parallel, the position information of a symbol added and subtracted from a pilot symbol and data symbol set by the OFDM transmitter 100 for each data symbol group. Acquire (S2310).

The pilot extractor 250 extracts two symbols from each data symbol group from the location information for each data symbol group (S2320).

The pilot extractor 250 extracts a pilot symbol and one data symbol selected by the OFDM transmitter 100 using the extracted two symbols (S2330).

When the OFDM transmission apparatus 100 generates two new symbols by adding and subtracting a pilot symbol and a selected data symbol, the two acquired symbols are pilot symbols. If the difference between the symbol plus two symbols and the symbol minus two symbols is obtained, the data symbol selected by the OFDM transmitter 100 is obtained. For example, when the pilot symbol is 1 and the data symbol selected by the OFDM transmitter 100 is 3 + j * 5, the symbol added with the pilot symbol and the data symbol is

And the pilot symbol minus the data symbol is

Assume that two symbols have been received. here,

Is used for normalization. Add two symbols

Divided by 1 to subtract 2 symbols

Dividing by gives 3 + j * 5.

When the OFDM transmitter 100 adds and subtracts the selected data symbol and the pilot symbol to generate two new symbols, the two symbols add up to become the selected data symbol. The difference between the symbol plus two symbols and the symbol minus two symbols is a pilot symbol. For example, if the selected data symbol is 3 + j * 5 and the pilot symbol is 1, the symbol in which the pilot symbol is added to the selected data symbol is

The symbol after subtracting the pilot symbol from the selected data symbol is

Assume that two symbols have been received. Add two symbols

Divide by 3 + j * 5 and subtract 2 symbols

Dividing by gives 1.

The pilot extractor 250 arranges the extracted pilot symbol and the data symbol at a position located in the OFDM transmitter 100 (S2340).

24 is a diagram illustrating a channel estimator illustrated in FIG. 14.

Referring to FIG. 24, the channel estimator 260 includes a multiplier 261, an LPF 263, and a divider 265.

The multiplier 261 multiplies the PN code generated by the OFDM transmitter 100 by the pilot symbol extracted by the pilot extractor 250 and outputs the multiplied PN code to the LPF 263.

The LPF 263 filters the pilot symbols multiplied by the PN code to remove noise.

The divider 265 estimates a channel by dividing the data symbols of each data symbol group by the pilot symbols of the corresponding data symbol group. For example, when each data symbol group and the pilot symbol of each data symbol group are as shown in FIG. 7, each of the three data symbols of the first data symbol group is divided into the first pilot symbol, and the seven of the second data symbol group Each of the data symbols is divided by a second pilot symbol.

Channel distortion is compensated by performing channel equalization using the channel estimated by the channel equalizer 270, and the symbol demapping unit 280 corresponds to the symbol mapping unit 120 of the OFDM transmitter 100. In the constellation diagram according to the demodulation method, each data symbol is de-mapped into a plurality of parallel data signals, and the plurality of parallel data signals are output to the PSC 280. The PSC 280 then recovers the data by converting the plurality of parallel data signals into a plurality of serial data signals.

The embodiments of the present invention described above are not only implemented through the apparatus and the method, but may also be implemented through a program for realizing a function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded. Implementation may be easily implemented by those skilled in the art from the description of the above-described embodiments.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (20)

1. In the device sending the data,

   A pilot generator for generating at least one pilot signal for channel estimation in a data receiving apparatus;

   A symbol mapping unit configured to symbol-map a plurality of data signals and the at least one pilot signal to generate a plurality of data symbols and at least one pilot symbol;

   A real signal converter for converting an input symbol in a frequency domain including the plurality of data symbols and the at least one pilot symbol into a real signal in a time domain;

   An angular modulator for angularly modulating the real signal;

   A PAPR control and power normalization unit for adjusting the magnitude of a sine component of the angularly modulated real signal according to a first gain, and varying the first gain according to an input signal, and

   A signal transmitter for converting the real signal is adjusted to a radio frequency signal for transmission

   Data transmission device comprising a.
2. In claim 1,

   A pilot symbol is set to correspond to each of a plurality of data symbol groups each including at least one data symbol, and after generating two symbols using one data symbol and a pilot symbol of each data symbol group, the respective data A symbol arranging unit arranged in a symbol group and output to the real signal converting unit

   Data transmission device further comprising.
3.  In claim 2,

   The symbol placement unit adds the one data symbol and the pilot symbol to generate one of the two symbols, and subtracts the one data symbol and the pilot symbol to generate another symbol of the two symbols. Transmitting device.
4. In claim 1,

   The angle modulator,

   A phase controller for controlling the magnitude of the real signal in accordance with a second gain, and

   And a modulator for angularly modulating the real signal into a cosine signal and a sine signal.
5. In claim 1,

   The real signal converter,

   A normalizer for normalizing the input symbol so that the average power of the input symbol is 1,

   An inverse fast Fourier transform unit for inverse fast Fourier transform on a plurality of input signals, and

   An input signal processor for inputting the input symbol and the conjugate complex symbol obtained by conjugate complex-conversion the input symbol to the inverse fast Fourier transform unit

   Data transmission device comprising a.
6. In claim 5,

   The input signal processor,

   When the number of symbols of the input symbol is N, N data symbols are positioned at positions 0 to N-1 th input signals, and the plurality of conjugated complex symbols are positioned at positions N to (2N-1) th input signals. Let's say

   Position the complex conjugate symbol of the (2N-k) th input signal at the position of the (N + 1) th to (2N-1) input signal,

   Wherein N is a positive number and k is a value from N + 1 to 2N-1.
7. In claim 1,

   The PAPR control and power normalization unit,

   A PAPR controller for controlling the magnitude of the sinusoidal component of the angularly modulated real signal according to the first gain;

   A first multiplier for generating a baseband I signal by multiplying a cosine component of the real signal by a set value for normalization, and

   A second multiplier for generating a baseband Q signal by multiplying a sine component of the real signal whose magnitude is controlled according to the first gain by the set value,

   And a PAPR of 0 when the first gain is 1.
8. On the device receiving the data,

   A power compensator for compensating the baseband signal corresponding to the received data in response to the size adjusted by the data transmitting apparatus for PAPR control;

   An angular demodulator for angularly demodulating the magnitude compensated baseband signal;

   A normalization and real signal inverse transform unit for converting the angular demodulated signal into a plurality of parallel symbols in the frequency domain in the time domain through a fast Fourier transform;

   A pilot extractor for extracting pilot symbols and data symbols from the parallel symbols;

   A channel estimator for estimating a channel using the pilot symbols,

   A channel equalizer for compensating the channel using the estimated channel, and

   A symbol demapping unit for reconstructing data by generating a plurality of data signals by symbol demapping the data symbols.

   Data receiving apparatus comprising a.
9. In claim 8,

   The demodulation unit,

   A phase estimator for calculating a phase estimation value of the baseband signal, and

   And a phase compensator for compensating the phase of the baseband signal from the phase estimate value.
10. In claim 9,

    And the phase estimating unit obtains an average value of phases of the baseband signal and calculates the phase estimation value using an inverse tangent of the average value.
11. In claim 9,

    And the phase estimating unit calculates the phase estimation value by using an inverse tangent after filtering the baseband signal.
12. In claim 9,

    The pilot extractor obtains location information of two symbols generated by using a pilot symbol in the data transmission apparatus from the parallel symbol, and receives data for extracting a pilot symbol and a data symbol using two symbols corresponding to the location information. Device.
13. In claim 8,

    The power compensator,

    Two multipliers for compensating the magnitudes of the I and Q signals of the baseband signal, respectively;

    A PAPR controller for dividing and outputting the magnitude-compensated Q signal by a gain,

    And the gain is variable.
14. In claim 8,

    The real signal inverse transform unit,

    A fast Fourier transform unit for generating the parallel symbols by performing fast Fourier transform on a plurality of input signals;

    A serial-to-parallel converter for converting the demodulated baseband signal from a serial signal to a parallel signal, and

    And a signal processor for outputting a part of the parallel symbol to the demapping unit.
15. In a method in which a data transmitting apparatus transmits data,

    Generating a plurality of pilot signals to be used for channel estimation in the data receiving apparatus;

    Symbol mapping a plurality of input signals and the plurality of pilot signals to generate a plurality of data symbols and a plurality of pilot symbols;

    Converting an input symbol in a frequency domain including the plurality of data symbols and the plurality of pilot symbols into a real signal in a time domain in a frequency domain;

    Angularly modulating the real signal;

    Controlling the magnitude of the sinusoidal signal for the angularly modulated real signal in accordance with the gain, and

    Converting the angularly modulated real signal into a radio frequency signal and transmitting the radio frequency signal

    Data transmission method comprising a.
16. The method of claim 15,

    The generating step,

    Setting a pilot symbol corresponding to each of a plurality of data symbol groups each including at least one data symbol,

    Generating two symbols using one data symbol and a pilot symbol of each data symbol group, and

    Placing the two symbols in each data symbol group.
17. The method of claim 15,

    The controlling step,

    And varying the gain in accordance with an input control signal.
18. In the method for the data receiving device to receive data,

    Compensating for the magnitude of the baseband signal corresponding to the received data;

    Demodulating the baseband signal;

    Converting the angularly demodulated signal into a plurality of parallel symbols in the frequency domain in the time domain through a fast Fourier transform,

    Extracting pilot symbols and data symbols from the parallel symbols;

    Compensating for the estimated channel using the pilot symbol, and

    Symbol demapping the data symbols to recover the received data

    Data receiving method comprising a.
19. The method of claim 18,

    The demodulation step is,

    Estimating the phase of the baseband signal, and

    Compensating for the phase of the baseband signal using a phase estimate value.
20. The method of claim 18,

    The extracting step,

    Acquiring position information of two symbols generated by using a pilot symbol in a data transmission apparatus, and

    And extracting pilot symbols and data symbols using two symbols corresponding to the location information.

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