JP2006229915A - Pulse shaping multicarrier transmitter/receiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter and receiver of a pulse shaping multicarrier system. <P>SOLUTION: The transmitter and receiver is constituted of a pulse shaping multicarrier transmitter which generates a multicarrier signal shaped by the pulse waveform from an error correction coded modulation signal using an IFFT unit and a pulse waveform multiplier which weights output of the IFFT unit by the pulse waveform and a pulse shaping multicarrier receiver which realizes a matching filter by the pulse waveform to a receiving signal, outputs receiving signals of each subcarrier and removes inter symbol interference generated in output of the receiving signals by repeatedly operating a turbo equalizer, an error correction decoder and a channel estimation unit using the pulse waveform multiplier and an FFT unit, pulse shaping multicarrier transmission in which an amount of calculation is sharply reduced is realized using the IFFT unit and the FFT unit of the pulse shaping multicarrier transmitter/receiver and the inter symbol interference generated in the receiving signal is removed by the pulse shaping multicarrier receiver. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pulse-shaped multicarrier transceiver.

In wireless communications, the orthogonal frequency division multiplexing (OFDM) system is attracting attention as a technique to reduce the delay caused by multipaths that occur in the wireless channel. In OFDM, orthogonal multicarrier transmission can be performed with a very small amount of computation by using inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT), and by introducing a guard interval, Interference is prevented from occurring. Therefore, high-speed transmission with high reliability can be realized even in the frequency selective fading environment where multipath delay is observed.

Since the spectrum of OFDM is configured by shaping the spectrum of each subcarrier modulation signal with a sinc function and overlaying it, it is difficult to keep the side lobe low. Therefore, deep carrier holes cannot be generated even if specific subcarriers are removed. Also, since unnecessary out-of-band leakage power increases, it is necessary to prepare a sufficiently large guard band so as not to affect other systems.

Non-Patent Document 1 proposes a multi-carrier transmission system that performs spectrum shaping with a Gaussian pulse waveform as a multi-carrier system with better frequency utilization efficiency. In this method, the frequency utilization efficiency is improved by arranging each subcarrier so that the spectrum shaped by the Gaussian pulse waveform overlaps.

However, in this method, when spectrum shaping is performed with a Gaussian pulse waveform in the transmitter, it is necessary to perform convolution integration with the Gaussian pulse on the modulated signal sequence in each subcarrier, and then multiply the carrier. Number of times is required. The amount of calculation is much larger than that of OFDM, which can replace carrier multiplication by IFFT, so there is a problem that the realization by hardware is poor. There is a similar problem in the receiver.

In the conventional Gaussian multicarrier system, intersymbol interference occurs between subcarriers with overlapping spectra, and an equalizer that eliminates this is essential. In order to operate this equalizer, it is necessary to estimate the impulse response of the channel between the transceiver. However, Non-Patent Document 1 does not show a specific channel estimation method. Since channel estimation is also affected by intersymbol interference, degradation of estimation accuracy becomes a problem.
Nomura, Suzuki, Suyama, Fukawa, “Gaussian multicarrier modulation / demodulation method for power line communication” IEICE Technical Report CS 2004-92, October, 2004.

Not only the conventional Gaussian pulse waveform but also the multi-carrier method that performs spectrum shaping with a general pulse waveform has the following drawbacks.
1. A large number of multiplications are required for convolution integration and carrier multiplication of the pulse waveform.
2. If the pulse-shaped subcarriers are not orthogonal, the channel estimation is affected by intersymbol interference, which degrades the estimation accuracy and, as a result, the equalizer's interference cancellation performance.
Considering the above points, there is no pulse-shaping multicarrier scheme that can suppress the computational complexity very much and compensate for the degradation of channel estimation due to intersymbol interference.

  The present invention has been made in view of such problems. In a multicarrier transmission system that performs spectrum shaping using a pulse waveform, the amount of calculation is extremely reduced, and the accuracy of channel estimation deteriorated due to intersymbol interference. The purpose of this study is to provide a pulse-shaping multicarrier transmitter and receiver that can improve the frequency.

Pulse shaping multicarrier for generating a multicarrier signal spectrum-shaped with a pulse waveform from an error correction coded modulation signal using the IFFT device of the present invention and a pulse waveform multiplier for weighting the output with a pulse waveform Using the transmitter, the pulse waveform multiplier, and the FFT unit, a matched filter based on the pulse waveform for the received signal is realized, the received signal of each subcarrier is output, and the intersymbol interference generated at the output is A pulse shaping multi-carrier receiver that removes a turbo equalizer, an error correction decoder, and a channel estimator by repeatedly operating, the IFFT unit of the pulse shaping multi-carrier transmitter, and the pulse By using the FFT unit of the shaped multicarrier receiver, the pulse shaping multi It can be realized Yaria transmission, by removing the inter-symbol interference occurring in the received signal by the pulse shaping multicarrier receiver, above object is achieved by enabling a good channel estimation and signal detection.

  The above-mentioned object of the present invention is that the pulse shaping multicarrier transmitter includes a cyclic redundancy check (CRC) encoder, an error correction encoder, an interleaver, a serial / parallel converter, and N (N is a positive number). (Integer) signal point mapper, multiplexer, IFFT unit, parallel-serial converter, (2M-1) (M is a positive integer) delay unit, and 2M pulse waveform multiplication Or an adder, or the CRC encoder inputs an information bit sequence to be transmitted, performs CRC encoding, and outputs a bit sequence obtained by adding a CRC code to the information bit sequence The error correction encoder receives the bit sequence, performs error correction encoding, and outputs an encoded bit sequence, and the interleaver performs the encoding. A bit sequence is input and an interleaved bit sequence is output, and the serial / parallel converter is configured to input the interleaved bit sequence and output a bit sequence parallel-converted into N sequences. And the signal point mapper maps the parallel-converted bit sequence in each subcarrier to a signal point and outputs a modulated signal. The multiplexer is known between the modulated signal and the transceiver. The pilot signal is input, and each signal is time-multiplexed and output. The IFFT unit converts the modulated signal or the pilot signal into a time-domain multicarrier signal by performing inverse fast Fourier transform. The parallel / serial converter is configured to output the multi-carrier signal output in parallel. The signal is converted to serial and output, and the delay unit outputs a multicarrier signal obtained by delaying the serially converted multicarrier signal by a period of Fourier transform, and the pulse waveform multiplier The delayed multicarrier signal is multiplied by a pulse waveform and output, and the adder synthesizes the outputs of 2M pulse waveform multipliers and outputs a pulse shaped multicarrier signal. Alternatively, in the pulse shaping multi-carrier transmitter, when the pulse waveform is a real symmetric pulse waveform, 2M pulse waveform multipliers are connected to the M pulse waveform multipliers, a sign inverter, a delay unit, Or the pulse shaping multi-carrier receiver has (2M-1) delay units and 2M pulse waveform multipliers. , Adder, serial / parallel converter, FFT unit, channel estimator, turbo equalizer, deinterleaver, error correction decoder, CRC decoder, and iterative control , A repetitive switch, and an interleaver. The turbo equalizer includes a subtractor, N signal detectors, a parallel-serial converter, a signal point mapper, an interference replica generator, Or the delay unit outputs a reception signal obtained by delaying the reception signal by a Fourier transform period, and the pulse waveform multiplier applies a pulse to the delayed reception signal. The waveform is multiplied to output a received signal after spectrum shaping by a pulse waveform, and the adder is an output of the 2M pulse waveform multipliers. The received signal after spectrum shaping is synthesized and the received signal for FFT is output. The serial / parallel converter converts the received signal for FFT into parallel output and the FFT unit The FFT received signal converted in parallel is fast Fourier transformed to be converted into a frequency-domain subcarrier received signal, and the channel estimator inputs the subcarrier received signal and the pilot signal, The impulse response and frequency response of the channel between the transmitter and the receiver are estimated by the least square method, and a channel estimation value is output. The subtracter in the turbo equalizer generates the subcarrier received signal and interference replica generation. Interference cancellation generated by subtracting the interference replica from the subcarrier received signal. The sub-carrier received signal after the interference cancellation is input to the signal detector in the turbo equalizer, and a signal using the channel estimation value in each sub-carrier is output. Detection and outputting a soft decision value, and the parallel-serial converter in the turbo equalizer serially converts and outputs the soft decision value in each subcarrier, and outputs the deinterleaver. The soft decision value converted into serial is input, deinterleaved and output, and the error correction decoder receives the soft decision value after deinterleaving, receives the error correction decoding and receives it The CRC decoder outputs a bit sequence and the feedback soft decision value, and the CRC decoder receives the received bit and performs CRC decoding to detect a decision error in the packet. If a decision error is detected, the error detection result is output. If no decision error is detected,. An error detection result and a received bit are output, and the repetition controller inputs the error detection result. When a determination error is detected, the repetition controller is turned on and the feedback soft decision value is set to the interleaver. The channel estimator, the turbo equalizer, and the error correction decoder are repeatedly operated, and the interleaver inputs the feedback soft decision value and performs interleaving. The signal point mapper in the turbo equalizer receives the feedback soft decision value after interleaving, generates and outputs an expected value of the modulated signal, and outputs the interference replica. The generator generates and outputs an interference replica using the expected value of the modulated signal and the channel estimation value, or the channel estimator For the remaining subcarrier received signal, channel estimation is performed by the least square method using the expected value of the pilot signal or the modulated signal, and the impulse response of the channel is estimated, or the pulse-shaped multicarrier This is achieved more effectively by adopting a honeycomb arrangement of pulse shaping subcarriers in the transmitter and the pulse shaping multicarrier receiver.

The present invention has the following effects.
According to the pulse shaping multicarrier transmitter / receiver according to the first aspect of the present invention, by using IFFT and FFT, multicarrier transmission spectrum-shaped by a pulse waveform can be realized with a very small amount of calculation. The accuracy of channel estimation degraded by interference can be improved.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Possible pulse waveforms include Gaussian pulses, rectangular pulses, triangular pulses, roll-off pulses, and root roll-off pulses. The pulse waveform is a pulse with a variable pulse width, a pulse with a very short pulse width and a very wide spectrum in the frequency domain, a pulse with a very long pulse width and a very narrow spectrum in the frequency domain. Etc. can be considered. However, the scope of application of the present invention is not limited to those pulses.

  First, the best mode for carrying out the first, second, and third aspects of the pulse shaping multicarrier transceiver will be described. Figure 1 shows the basic configuration of a pulse-shaping multicarrier transmitter. As shown in FIG. 1, a transmitter according to the present invention includes a CRC encoder 2, an error correction encoder 3, an interleaver 4, a serial / parallel converter 5, a signal point mapper 6, and a multiplexer 8. And an IFFT unit 9, a parallel / serial converter 10, a delay unit 11, a pulse waveform multiplier 12, and an adder 13.

  The pulse shaping multi-carrier transmitter performs CRC coding on the information bit sequence input from the transmission bit input terminal using the CRC encoder 2 and outputs a bit sequence obtained by adding a CRC code to the information bit sequence. . The error correction encoder 3 performs error correction encoding on the bit sequence and outputs the encoded bit sequence. Next, the interleaver 4 interleaves the encoded bit sequence and outputs it. The interleaved bit sequence is divided into subcarriers by the serial / parallel converter 5 and converted into N sequences. The bit sequence in each subcarrier is mapped to signal points by a signal point mapper 6 and output as a modulated signal. The multiplexer 8 time-multiplexes a known pilot signal sequence and modulated signal sequence between the transceivers. The IFFT unit 9 performs inverse fast Fourier transform on the modulated signal or pilot signal to convert it into a multi-carrier signal in the time domain and outputs it. The parallel / serial converter 10 converts the multicarrier signal output in parallel from the IFFT unit 9 into serial data. After that, spectrum shaping is performed with a pulse waveform using (2M-1) delay units 11 and 2M pulse waveform multipliers 12. In the conventional method, the modulated signal sequence is convolved with the pulse waveform for each subcarrier in the frequency domain, and then the carrier is multiplied to generate a spectrum-shaped multicarrier signal.

However, in the present invention, the IFFT unit 9 first multiplies the carrier, and then, in the time domain, uses (2M-1) delay units 11 and 2M pulse waveform multipliers 12 to perform time multicarrier after IFFT. By multiplying the signal by the pulse waveform and adding it by the adder 13, a multicarrier signal in which a plurality of modulation signals overlap is realized. This is based on the fact that convolution integration in the frequency domain is equivalent to multiplication in the time domain. The delay unit 11 delays the serially converted multicarrier signal by the Fourier transform period T _s .

となる．ここで，Ｎはサブキャリア数（偶数）であり，Δｆはサブキャリア間隔で

に基づいて各サブキャリアで変調信号とパルス波形の畳み込み積分を行い，そして，数式（１）に基づいてキャリア乗算を行っている．If the modulation signal in the i-th symbol and the n-th subcarrier is d _n (i) and the symbol period is T _s , the transmission signal s (t) is

It becomes. Here, N is the number of subcarriers (even number), and Δf is the subcarrier interval.

Based on, the convolution integration of the modulated signal and the pulse waveform is performed on each subcarrier, and carrier multiplication is performed based on Equation (1).

と書き換え，さらに，サンプリング周期Δｔ＝Ｔ_ｓ／Ｎで離散化したｓｉ（ｋΔｔ）は

となることから，ｓ_ｉ．ｋはｄ_ｎ（ｉ）をＮポイントのＩＦＦＴ器９でフーリエ変換することで生成で

離散化された送信信号ｓ_ｋ＝ｓ（ｋΔｔ）は

となり，２Ｍ個のＩＦＦＴ器の出力を２Ｍ個のパルス波形ｇ（ｔ）で重み付けして合成することで，送信信号を生成できる．この処理は（２Ｍ−１）個の遅延器１１と２Ｍ個のパルス波形乗算器１２と加算器１３で実現される．In the present invention, the transmission signal s (t) is

Furthermore, si (kΔt) discretized at the sampling period Δt = T _s / N is

S _{i. k} is generated by Fourier transforming d _n (i) with an N-point IFFT unit 9.

The discretized transmission signal s _k = s (kΔt) is

Thus, a transmission signal can be generated by weighting and combining the outputs of 2M IFFT units with 2M pulse waveforms g (t). This processing is realized by (2M−1) delay units 11, 2M pulse waveform multipliers 12 and adders 13.

  From the above, according to the best mode for carrying out the present invention, carrier multiplication is performed using an IFFT device, and convolution integration performed on each subcarrier is replaced with pulse waveform multiplication after IFFT. The amount of computation can be greatly reduced.

となる．^＊を複素共役とすると，上記の数式は変調信号ｄ_ｎ（ｉ）が実数である場合には

となる．すなわち，ｔ＜０におけるｇ（ｔ）とｓ_ｉ，ｋの乗算は，ｓ_ｉ，ｋの性質とｇ（ｔ）が原点に対して対

符号反転器で実現できる．また，変調信号ｄ_ｎ（ｉ）が複素数である場合には，ｓ_{ｉ，−ｋ′}ｇ（−ｋ′Δｔ）が

行うＭ個のパルス波形乗算器と時間をシフトする遅延器と符号反転器を用いることで，２Ｍ個のパルス波形乗算器を置き換えることができる．The best mode for carrying out the fourth aspect of the pulse shaping multicarrier transceiver will be described. When g (t) is a real symmetric pulse waveform, g (t) = g (−t) holds. Considering that this property is applied to s _{i, k} g (kΔt−iT _s ) of Equation (7), when k = iN + k ′

It becomes. ^Assuming that ^* is a complex conjugate, the above formula is obtained when the modulation signal d _n (i) is a real number.

It becomes. That is, the multiplication of g (t) and s _{i, k} at t <0 is the same as the property of s _{i, k} and g (t) with respect to the origin.

This can be realized with a sign inverter. When the modulation signal d _n (i) is a complex number, s _{i, −k ′} g (−k′Δt) is

By using M pulse waveform multipliers to be performed, a time shifter delay unit, and a sign inverter, 2M pulse waveform multipliers can be replaced.

  From the above, according to the best mode for carrying out the present invention, the number of multiplications of the time domain multicarrier signal, which is the output of the IFFT device, and the pulse waveform can be reduced due to the symmetry of the pulse waveform.

  Next, the best mode for carrying out the first, fifth and sixth aspects of the pulse shaping multicarrier transceiver will be described.

  Figure 2 shows the basic configuration of the pulse-shaping multicarrier receiver. As shown in FIG. 2, the receiver according to the present invention includes (2M−1) delay units 16, 2M pulse waveform multipliers 17, an adder 18, a serial / parallel converter 19, and , FFT unit 20, channel estimator 22, turbo equalizer 23, deinterleaver 29, error correction decoder 30, CRC decoder 31, repetition controller 32, repetition switch 33, and interleaver 34. It consists of Further, the turbo equalizer 23 includes a subtractor 24, N signal detectors 25, a parallel / serial converter 26, a signal point mapper 28, and an interference replica generator 27.

となる．従来手法では，ｒ（ｔ）にキャリアを乗算し，各サブキャリアにおいてパルス波形を畳み込みため，第ｎサブキャリアにおける整合フィルタ出力ｙ_ｎ（ｔ）は

となる．本発明では，ｙ_ｎ（ｔ）をｇ（ｔ）のパルス幅を考慮して

となり，さらに，ｔ＝ｉＴ_ｓとし，フーリエ変換を離散フーリエ変換に置き換えると，ｙ_ｎ（ｔ）は

Ｎの周期関数であることを用いた．本発明では，（２Ｍ−１）個の遅延器１６と２Ｍ個パルス波形乗算器１７と加算器１８を用いて数式（１９）の大括弧内の計算を行い，その後，ＦＦＴ器２０によりキャリアを乗算することで，各サブキャリアにおける整合フィルタ出力であるサブキャリア受信信号ｙ_ｎ，ｉを計算する．First, the pulse shaping multicarrier receiver uses the delay unit 16, the pulse waveform multiplier 17, the adder 18, and the FFT unit 20 to realize a matched filter based on the pulse waveform for the received signal, and to match each subcarrier. Generate a received signal that is a filter output. When r (t) is a received signal, r (t) is obtained by using the impulse response h (t) and noise n (t) of the channel.

It becomes. In the conventional method, r (t) is multiplied by the carrier, and the pulse waveform is convolved in each subcarrier, so that the matched filter output y _n (t) in the nth subcarrier is

It becomes. In the present invention, y _n (t) is considered in consideration of the pulse width of g (t).

Furthermore, when t = iT _s and the Fourier transform is replaced with a discrete Fourier transform, y _n (t) is

The periodic function of N was used. In the present invention, the calculation in the square brackets of the equation (19) is performed using (2M−1) delay units 16, 2M pulse waveform multipliers 17, and adder 18, and then the carrier is detected by FFT unit 20. By multiplying, the subcarrier received signal yn _{, i} which is the matched filter output in each subcarrier is calculated.

Next, the receiver uses the channel estimator 22 to remove the modulation of the subcarrier received signals y _{n, i} using the pilot signal d _n (i), thereby obtaining the channel frequency response H _n . presume. Further, to estimate the impulse response by the least square method using H _n in each sub-carrier. A specific estimation method is shown in Non-Patent Document 2. The estimated impulse response includes the effect of the time difference of the matched filter caused by multipath delay. Since this component can be calculated in advance for each delay time, the exact impulse response can be estimated by dividing the estimated value by this component. The channel estimator 22 outputs the estimated impulse response as a channel estimation value.
K. Fukawa et al., "OFDM channel estimation with RLS algorithm forward differential pilot schemes in mobile radio transmission", IEICE Trans. on Communi. , Vol. E86-B, no. 1, pp. 266-274, Jan. 2003.

The turbo equalizer 23 detects the transmission signal d _n (i) from the subcarrier reception signal using the channel estimation value. In the pulse-shaping multicarrier transmission method, the intercarrier interference occurs in the received subcarrier signal because the spectrum of each subcarrier overlaps. Furthermore, in multipath transmission lines, intersymbol interference occurs due to delayed waves, so it is necessary to detect the signal by removing this intersymbol interference. In the present invention, the interference replica generator 27 and the subtracter 24 remove intersymbol interference. If error correction decoding has never been performed, the interference replica generator 27 generates an interference replica using only the channel estimation value and the pilot signal, and the subtracter 24 subtracts the replica from the subcarrier received signal. . The signal detector 25 performs synchronous detection using the channel estimation value and outputs a soft decision value. If error correction decoding has already been performed, the interference replica generator 27 generates an interference replica using the expected value of the modulation signal of the pilot signal and transmission data, and all the modulation signals including the data are related. Intersymbol interference is removed. The soft decision value output from the signal detector 25 is serially converted by the parallel / serial converter 26 and then deinterleaved by the deinterleaver 29. Thereafter, the deinterleaved soft decision value is subjected to error correction decoding by maximum a posteriori probability (MAP) decoding in the error correction decoder 30, and a received bit sequence and a feedback soft decision value are calculated. The received bit sequence is CRC-decoded by the CRC decoder 31 to detect a determination error in the packet. The CRC decoder 31 outputs an error detection result when a determination error is detected, and outputs an error detection result and a received bit when a determination error is not detected. Further, the iterative controller 32 controls the iterative process based on the error detection result, thereby controlling the iterative process for operating the channel estimator 22, the turbo equalizer 23, and the error correction decoder 30 again. When a determination error is detected, the feedback soft decision value is input to the interleaver 34, interleaved, and then input to the signal point mapper 28. The signal point mapper 28 generates an expected value of the modulation signal from the feedback soft decision value after interleaving. The expected value of the modulation signal is used for interference replica generation in the interference replica generator 27 as described above. Interference cancellation, channel estimation, signal detection, and error correction decoding are performed again, and good signal detection can be performed by repeating these processes.

  From the above, according to the best mode for carrying out the present invention, carrier multiplication is performed using an FFT unit in a pulse shaping multicarrier receiver, and the convolution integral of the pulse waveform performed on each subcarrier is FFT. By substituting the previous pulse waveform multiplication, the amount of calculation can be greatly reduced. In addition, by repeating interference estimation, signal detection, and error correction decoding in the channel estimation, turbo equalizer, the intersymbol interference generated in the received signal can be removed, and good signal detection can be performed.

The best mode for carrying out the seventh aspect of the pulse shaping multicarrier transceiver will be described. In the channel estimator 22, when the subcarrier received signal y _{n, i} is demodulated using the pilot signal d _n (i) and the frequency response of the channel is estimated, the subcarrier received signal has intersymbol interference. As a result, the estimation accuracy deteriorates. Therefore, in the present invention, intersymbol interference from pilot signals other than the nth subcarrier is removed by generating a replica with the interference replica generator 27 and subtracting it from the subcarrier received signal. Similarly, interference cancellation is performed for other subcarriers. Then, channel estimation is performed again using the subcarrier received signal after removal. Furthermore, the estimated channel estimation value is removed. By repeating this series of processing, the accuracy of channel estimation is improved.

  Also, the accuracy of channel estimation can be improved by performing inter-symbol interference removal and channel estimation repeatedly using the expected value of the modulation signal generated by the signal point mapper 28 in the data interval.

  From the above, according to the best mode for carrying out the present invention, it is possible to compensate for the degradation of channel estimation accuracy caused by intersymbol interference, and with the improvement of channel estimation accuracy, the ability to remove intersymbol interference. The signal can be improved and good signal detection can be performed.

The best mode for carrying out the eighth invention related to the pulse shaping multi-carrier transceiver will be described. Pulse shaping multicarrier Δf interval pulse shaping sub-carriers in frequency direction in the transmitter, but are arranged at T _s intervals in the time direction (square arrangement), for example, in a direction only odd-numbered sub-carrier time T _s / The honeycomb arrangement can be realized by shifting by two, or by shifting all subcarriers of odd-numbered symbols by Δf / 2 in the frequency direction. When the honeycomb arrangement is used, the distance between the subcarriers that have undergone pulse shaping increases, so the amount of intersymbol interference can be reduced.

First, the configuration of a pulse-shaped multicarrier transceiver that shifts only odd-numbered subcarriers in the time direction by T _s / 2 is described. Since the odd-numbered subcarriers are shifted in time, the transmitter cannot perform Fourier transform with the same IFFT unit. Therefore, the transmitter generates a time-domain multicarrier signal using an even-numbered subcarrier IFFT unit and an odd-numbered subcarrier IFFT unit, and 2M pulse waveform multipliers for each of them. And (2M-1) delay devices are used to multiply the pulse waveform, and only the multicarrier signal multiplied by the pulse waveform of the odd-numbered subcarrier is delayed by T _s / 2 by the delay device, and the even component Can be realized by combining all of the odd components with an adder. That is, it is composed of two IFFT units, 4M pulse waveform multipliers, (4M-2) delay units, and one T _s / 2 delay unit, and other configurations are the same as those in FIG. . The receiver processes only the even-numbered subcarriers with the same configuration as the square arrangement, and for the odd-numbered subcarriers, the received signal is delayed by T _s / 2 with a delay device, and is different from the even-numbered (2M -1) Generate a subcarrier reception signal using 1 delay unit, 2M pulse waveform multiplier, adder, serial / parallel converter, and FFT unit. That is, it is composed of one T _s / 2 delay device, (4M−2) delay devices, 4M pulse waveform multipliers, and two FFT devices, and the other configuration is the same as FIG. .

Next, the configuration of a pulse-shaped multicarrier transceiver that shifts all subcarriers of odd-numbered symbols by Δf / 2 in the frequency direction is described. Since only the odd-numbered symbols are shifted in frequency by Δf / 2, the transmitter ^applies e ^jπk to the time-domain multicarrier signal that is the output of the parallel-serial converter 10 in FIG. Multiply. However, ^ejπk is 1 when k is an even number, and -1 when k is an odd number. Therefore, it can be realized only by reversing the sign of the multicarrier signal in the time domain. That is, it can be realized by inserting one sign inverter after the parallel-serial converter 10 in FIG. The receiver can be realized by inserting a sign inverter in front of the serial / parallel converter 19 in FIG. 2 and inverting the sign for odd-numbered samples of odd-numbered symbols.

  From the above, according to the best mode for carrying out the present invention, even in a pulse shaping multi-carrier transmitter / receiver in which pulse shaped subcarriers are arranged in a honeycomb structure, by using an IFFT device and an FFT device, the amount of calculation is increased. Can be greatly reduced.

  The present invention is not limited to the best mode for carrying out the invention, and various other configurations can be adopted without departing from the gist of the invention.

It is a figure which shows the basic composition of the pulse shaping multicarrier transmitter by this invention. It is a figure which shows the basic composition of the pulse shaping multicarrier receiver by this invention.

Explanation of symbols

1: transmission bit input terminal, 2: CRC encoder, 3: error correction encoder, 4: interleaver, 5: serial / parallel converter, 6: signal point mapper, 7: pilot signal input terminal, 8: multiplexer 9: IFFT unit, 10: parallel / serial converter, 11: delay unit, 12: pulse waveform multiplier, 13: adder, 14: baseband transmission signal output terminal, 15: baseband reception signal input terminal, 16: Delay unit, 17: Pulse waveform multiplier, 18: Adder, 19: Serial / parallel converter, 20: FFT unit, 21: Pilot signal input terminal, 22: Channel estimator, 23: Turbo equalizer, 24: Subtractor, 25: signal detector, 26: parallel-serial converter, 27: interference replica generator, 28: signal point mapper, 29: deinterleaver, 3 : Error correction decoder, 31: CRC decoder 32: repetitive controller, 33: repeatedly switch, 34: Interleaver, 35: reception bit output terminal

Claims (8)

  A pulse for generating a multi-carrier signal spectrum-shaped with a pulse waveform from an error-correction-coded modulated signal using an inverse fast Fourier transform (IFFT) unit and a pulse waveform multiplier that weights the output with a pulse waveform. Using the shaped multicarrier transmitter, the pulse waveform multiplier, and the fast Fourier transform (FFT) unit, a matched filter based on the pulse waveform for the received signal is realized, and the received signal of each subcarrier is output, and the output And a pulse shaping multicarrier receiver that eliminates intersymbol interference generated in the signal by repeatedly operating a turbo equalizer, an error correction decoder, and a channel estimator. By using the IFFT device of the above and the FFT device of the pulse shaping multicarrier receiver. It is possible to realize pulse-shaping multicarrier transmission with a significant reduction in noise and to perform good channel estimation and signal detection by eliminating intersymbol interference generated in the received signal by the pulse-shaping multicarrier receiver. Pulse shaping multi-carrier transceiver.   The pulse shaping multi-carrier transmitter includes a cyclic redundancy check (CRC) encoder, an error correction encoder, an interleaver, a serial / parallel converter, N (N is a positive integer) signal point mapper, , Multiplexer, IFFT unit, parallel-serial converter, (2M-1) (M is a positive integer) delay units, 2M pulse waveform multipliers, and adders. The pulse-shaping multicarrier transceiver according to claim 1.   The CRC encoder inputs an information bit sequence to be transmitted, performs CRC encoding, and outputs a bit sequence obtained by adding a CRC code to the information bit sequence, and the error correction encoder inputs the bit sequence. Then, error correction coding is performed to output a coded bit sequence, and the interleaver receives the coded bit sequence, outputs an interleaved bit sequence, and outputs the serial bit sequence. A parallel converter is configured to input the interleaved bit sequence and output a bit sequence parallel-converted into N sequences, and the signal point mapper includes the parallel-converted bit in each subcarrier A sequence is mapped to a signal point and a modulated signal is output. The multiplexer includes the modulated signal and a transceiver A known pilot signal is input and the signals are time-multiplexed and output, and the IFFT unit converts the modulated signal or the pilot signal into a time-domain multi-carrier signal by inverse fast Fourier transform. The parallel-serial converter converts the multi-carrier signal output in parallel into serial data and outputs the serial signal, and the delay unit outputs the multi-carrier signal converted into serial data. A multi-carrier signal delayed by a period of Fourier transform is output, the pulse waveform multiplier multiplies the delayed multi-carrier signal by a pulse waveform, and the adder 3. The outputs of the 2M pulse waveform multipliers are combined to output a pulse shaped multicarrier signal. Of pulse shaping the multi-carrier transceiver.   3. The pulse shaping multicarrier transmitter according to claim 2, wherein when the pulse waveform is a real symmetric pulse waveform, 2M pulse waveform multipliers are replaced with M pulse waveform multipliers, a sign inverter, and a delay unit. The pulse shaping multicarrier transceiver according to claim 1 to be replaced.   The pulse shaping multicarrier receiver includes (2M-1) delay units, 2M pulse waveform multipliers, an adder, a serial / parallel converter, the FFT unit, and the channel estimator. , The turbo equalizer, a deinterleaver, the error correction decoder, a CRC decoder, a repetition controller, a repetition switch, and an interleaver. The turbo equalizer includes a subtractor, 2. The pulse shaping multicarrier transceiver according to claim 1, comprising N signal detectors, a parallel / serial converter, a signal point mapper, and an interference replica generator.   The delay unit outputs a reception signal obtained by delaying the reception signal by a Fourier transform period, and the pulse waveform multiplier multiplies the delayed reception signal by a pulse waveform to obtain a spectrum based on the pulse waveform. The shaped received signal is output, and the adder synthesizes the received signal after the spectrum shaping by the pulse waveform which is the output of the 2M pulse waveform multipliers, and outputs the FFT received signal. The serial-to-parallel converter converts the FFT reception signal into parallel signals and outputs them, and the FFT unit performs fast Fourier transform on the parallel-converted FFT reception signals to obtain a frequency domain sub-signal. The channel estimator receives the subcarrier received signal and the pilot signal, and converts them into carrier received signals. The channel impulse response and the frequency response between the transmitter and the receiver are estimated by the least square method, and a channel estimation value is output. The subtracter in the turbo equalizer includes the subcarrier received signal, an interference replica, The signal detector in the turbo equalizer is configured to input an interference replica generated by a generator and output a subcarrier reception signal after interference cancellation obtained by subtracting the interference replica from the subcarrier reception signal. Receives the subcarrier received signal after the interference cancellation, performs signal detection using the channel estimation value in each subcarrier, outputs a soft decision value, and outputs the parallel decision signal in the turbo equalizer. The serial converter converts the soft decision value in each subcarrier to serial and outputs it, and the deinterleaver serially The converted soft decision value is input, deinterleaved, and output, and the error correction decoder inputs the soft decision value after deinterleaving, performs error correction decoding, and receives the received bit sequence and the A soft feedback decision value is output, and the CRC decoder receives the received bit and performs CRC decoding to detect a decision error in the packet. If a decision error is detected, an error detection is performed. When the result is output and no judgment error is detected, the error detection result and the received bit are output. The repeat controller inputs the error detection result and the judgment error is detected. Is an iterative control for turning on the iterative switch and inputting the feedback soft decision value to the interleaver to operate the channel estimator, the turbo equalizer, and the error correction decoder again. The interleaver inputs, interleaves and outputs the feedback soft decision value, and the signal point mapper in the turbo equalizer outputs the feedback soft decision value after interleaving. 6. The interference replica generator generates and outputs an interference replica using an expected value of the modulation signal and a channel estimation value, wherein the expected value of the modulation signal is generated and output. Pulse shaping multi-carrier transceiver. The channel estimator estimates the impulse response of the channel by performing channel estimation on the subcarrier received signal after the interference cancellation by using a least square method using an expected value of a pilot signal or the modulated signal. 5. The pulse-shaping multi-carrier transceiver according to 5. The pulse-shaped multi-carrier transmission / reception according to claim 1, wherein a pulse-shaping subcarrier is arranged in a honeycomb in the pulse-shaping multi-carrier transmitter according to claim 2 and the pulse-shaping multi-carrier receiver according to claim 5. Machine.

Images