JP2006203835A - Digital ssb turbo transceiver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transmitter of a digital SSB modulation system capable of performing modulation, using only a single carrier wave and a receiver, capable of receiving signals by realizing a half bandwidth of digital modulated signal, when shaping a spectrum of wireless communication. <P>SOLUTION: The present invention comprises a digital SSB turbo transmitter which uses a pulse shaping filter 1 for performing a band limitation and a pulse shaping filter 2 for realizing Hilbert transformation of the impulse response of the pulse shaping filter 1 to modulate an in-phase component and the quadrature component of an error-correcting encoded digital modulation signal into a single upper or lower side band; and a digital SSB turbo receiver which uses a matched filter 1 of the pulse shaping filter 1 and a matched filter 2 of the pulse-shaping filter 2, to demodulate the in-phase component and the quadrature component of the modulation signal from a reception signal of the upper- or the lower-side band and eliminates inter-code interferences that occurs in matched filter outputs, by repeatedly operating a turbo equalizer and an error-correcting decoder. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a digital SSB turbo transceiver.

In wireless communications, transmission schemes for effectively using limited frequency resources are being actively studied. In particular, digital SSB modulation schemes that transmit digital modulation signals by single sideband (SSB) modulation are attracting attention. Digital modulation signals include modulation signals such as BPSK, QPSK, and 8PSK that are multilevel PSK modulation, and modulation signals such as 16QAM, 64QAM, and 256QAM that are multilevel QAM modulation. In particular, QPSK and 16QAM are often used.

An SSB-QPSK system, which is a kind of digital SSB modulation system that can perform SSB modulation of a QPSK signal and narrow the bandwidth compared to the conventional QPSK, has been proposed (for example, see Non-Patent Document 1 or 2). In patent document 1, the SSB-QPSK system which transmits QPSK with two carrier waves is proposed. In this method, when the bandwidth is f _s , the in-phase component (I component) and the quadrature component (Q component) of the QPSK signal having a double bandwidth are respectively transmitted to the upper sideband (USB) and the lower sideband ( after modulation to LSB), the USB ^- f _s / 2, LSB to by synthesized frequency shifted by _f s / 2, in a manner that half of a conventional QPSK the occupied bandwidth overlapping the USB and LSB is there.

However, in this method, when the I and Q components are pulse-shaped by the band limiting filter, a bandwidth half of QPSK cannot be realized completely, and a frequency oscillator for generating two carrier waves is required. There was a problem.

Therefore, the present inventors invented a digital SSB modulation method capable of (i) completely realizing half the bandwidth of a digital modulation signal and (ii) modulating with only one carrier wave. In the present invention, a digital SSB modulation system is realized by using a band shaping filter and a pulse shaping filter that realizes an impulse response obtained by converting the impulse response of the filter into a Hilbert transform. In addition, in this system, intersymbol interference occurs in principle, so an error correction code such as a convolutional code or a turbo code is added to the transmitter, and the receiver performs repeated error correction decoding and adaptive equalization. The intersymbol interference is removed by equalization.
S. A. Mutababa, “A novel scheme for transmitting QPSK as a single-sideband signal” IEEE GLOBECOM 98, vol. 1, pp. 592-597, 1998. Oichiro Genichiro et al., “New Modulation Method for Frequency Utilization Efficiency”, IEICE Technical Report RCS2003-184, pp. 189-194, November 2003.

The conventional method has the following disadvantages.
1. If the I and Q components are pulse-shaped by a band-limiting filter, it is not possible to realize a bandwidth that is half that of a digitally modulated signal.
2. Multiple frequency oscillators are required to generate two carriers.
Considering the above points, there is no digital SSB modulation method that can completely realize the half bandwidth of the digital modulation signal at the time of pulse shaping, and can modulate only with one carrier wave.

  The present invention has been made in view of the above problems, and can realize a digital SSB modulation type transmitter capable of completely realizing a half bandwidth of a digital modulation signal at the time of pulse shaping, and further capable of modulation with only one carrier wave. And it aims at providing the receiver which can receive the signal transmitted with the transmitter.

An in-phase component and a quadrature component of an error-correction-coded digital modulation signal using the pulse shaping filter 1 that performs band limitation of the present invention and a pulse shaping filter 2 that realizes an impulse response that is a Hilbert transform of the impulse response. Using a digital SSB turbo transmitter that modulates the signal into a single sideband of the upper sideband or the lower sideband, the matched filter 1 of the pulse shaping filter 1, and the matched filter 2 of the pulse shaping filter 2. Demodulate the in-phase component and quadrature component of the digital modulation signal from the received signal in the upper sideband or the lower sideband, and repeatedly operate the turbo equalizer and error correction decoder for intersymbol interference generated at the matched filter output And the digital SSB turbo receiver to be eliminated by the digital SSB turbo transmitter of the present invention. At half the bandwidth of the digital modulation signal can achieve the same transmission rate, the above object is achieved by removing the demodulation and intersymbol interference of the digital SSB modulation signal by the digital SSB turbo receiver.

  The digital SSB turbo transmitter includes a CRC encoder, an error correction encoder, an interleaver, a multiplexer, a serial / parallel converter, a signal mapper, and the pulse shaper. By comprising the filter 1, the pulse shaping filter 2, the transmitter subtractor, the transmitter adder, and the quadrature modulator, or the CRC encoder Input, CRC encoding is performed to output a bit sequence obtained by adding a CRC code to the information bit sequence, and the error correction encoder inputs the bit sequence, performs error correction encoding, and performs encoding. The interleaver inputs the coded bit sequence and outputs the interleaved bit sequence. The multiplexer inputs a known pilot signal sequence between the transceiver and the interleaved bit sequence, and multiplexes and outputs the respective sequences, and the serial-parallel converter includes the interleaver. The converted bit sequence or the pilot sequence is input and parallel-converted into two sequences for the in-phase component and the quadrature component, and the bit sequence is output. The signal mapper converts the parallel-converted bit sequence into a signal Mapping to a point and outputting a digital modulation signal, and the pulse shaping filter 1 inputs the digital modulation signal, convolves a band-limiting pulse waveform, and outputs a digital modulation signal after pulse shaping, The pulse shaping filter 2 inputs the digital modulation signal and inputs the power. The pulse waveform obtained by Hilbert transforming the band limiting pulse waveform of the S shaping filter 1 is convolved to output a digital modulated signal after pulse shaping, and the transmitter subtractor converts the in-phase component of the digital modulated signal to the pulse The quadrature component of the digital modulation signal is input to the pulse shaping filter 2 from the pulse-modulated digital modulation signal that is input to and output from the shaping filter 1, and the digital modulation signal that is output after the pulse shaping is subtracted from the digital modulation signal The in-phase component of the SSB modulation signal is output, and the transmitter adder inputs the in-phase component of the digital modulation signal to the pulse shaping filter 2 and outputs the digital modulation signal to the output digital modulation signal after the pulse shaping. Input the quadrature component of the signal to the pulse shaping filter 1 and output the pulse shaping The digital modulation signal is added to output the quadrature component of the digital SSB modulation signal, and the quadrature modulator inputs the in-phase component and quadrature component of the digital SSB modulation signal, performs quadrature modulation using the carrier wave, By generating a digital SSB modulated transmission signal, or the pulse shaping filter 1 uses a pulse waveform obtained by multiplying a band limiting pulse waveform by a window function as the pulse waveform, and the pulse shaping filter 2 By using a pulse waveform obtained by multiplying the pulse waveform obtained by Hilbert transform of the band limiting pulse waveform with a window function as the pulse waveform, or the digital SSB turbo receiver includes an orthogonal demodulator, a low-pass filter ( LPF), the matched filter 1, the matched filter 2, a receiver adder, and a receiver subtracter A channel estimator, a turbo estimator, a deinterleaver, an interleaver, the error correction decoder, an iterative controller, and a CRC decoder, or The quadrature demodulator receives a digital SSB modulated received signal, performs quadrature demodulation using a carrier wave, and outputs an in-phase component and a quadrature component of the received signal. A component is input, and only the in-phase component or the quadrature component of the baseband received signal is extracted and output. The matched filter 1 receives the baseband received signal, and outputs a band limiting pulse of the pulse shaping filter 1 A pulse waveform that matches the waveform is convoluted to output a matched baseband received signal, and the matched filter 2 includes the baseband A reception signal is input, a pulse waveform that matches the pulse waveform of the pulse shaping filter 2 is convolved, and a matched baseband reception signal is output. The receiver adder is configured to output the baseband reception signal. Are input to the matched filter 1 and output to the matched baseband received signal, and the quadrature component of the baseband received signal is input to the matched filter 2 and output. The signals are added to output the in-phase component of the digitally modulated received signal, and the receiver subtractor inputs the quadrature component of the baseband received signal to the matched filter 1 and outputs the matched base signal The in-phase component of the baseband received signal from the band received signal is input to the matched filter 2 and output from the matched baseband received signal. And the quadrature component of the digital modulation reception signal is output, and the channel estimator inputs the quadrature component and the in-phase component of the digital modulation reception signal, estimates the channel impulse response between the transceiver, The turbo equalizer outputs a quadrature component and an in-phase component of the digital modulation reception signal, and uses an interleaved feedback detection signal, the channel estimation value, and the number of repetitions. The deinterleaver inputs the detection signal, deinterleaves and outputs the detection signal, and the error correction decoder outputs the detection signal after deinterleaving. A signal is input, error correction decoding is performed to output a received bit sequence and the feedback detection signal, and the CRC decoder And a CRC decoding to detect a determination error in the packet, and when an error detection result and a determination error are not detected, a received bit is output, and the interleaver A feedback detection signal is input, interleaved, and output. The repetition controller inputs the error detection result, and when a determination error is detected, the repetition count is input to the turbo equalizer. By outputting and operating in the order of the interleaver, the turbo equalizer, and the error correction decoder, and performing a control to repeat equalization processing and decoding processing, or the turbo equalizer is turbo equalization A subtractor for a device, a linear filter, a soft output detector, an intersymbol interference (ISI) replica generator, and a tap coefficient generator; The Rica generator receives the interleaved feedback detection signal and the channel estimation value, and generates and outputs a replica of the intersymbol interference component (ISI replica) of the digital modulation reception signal. The subtractor The ISI replica is subtracted from the digitally modulated received signal, and the tap coefficient generator uses the repetition count and the channel estimation value to suppress intersymbol interference or intersymbol interference removal residual, noise Tap coefficients for the linear filter based on the least square method for whitening are generated, and the linear filter receives the digital modulation reception signal after subtraction of the ISI replica, and linearly uses the tap coefficients. And the soft output detector receives the combined signal and outputs the detected signal. Or the channel estimator generates a received signal replica by inputting a digital modulation signal generated by using the pilot signal sequence or the feedback detection signal to a transversal filter, and generating the received signal replica Estimating the channel impulse response as the tap coefficient of the transversal filter using the least square method so that the absolute value square value of the difference from the digital modulation reception signal is minimized, or error correction 6. The digital SSB turbo receiver according to claim 5, wherein the encoded digital modulation signal is transmitted by a conventional digital modulation transmitter, and an upper sideband component is used for the received signal of the digital modulation signal. 6. The digital SSB turbo reception according to claim 5, wherein the detection is performed and the lower sideband component is used. This is achieved more effectively by improving the transmission characteristics in the frequency selective fading channel by detecting them by a machine and optimally combining the detection results.

The present invention has the following effects.
According to the digital SSB turbo transmitter / receiver according to the first aspect of the present invention, the digital SSB modulation capable of completely realizing a half bandwidth of the digital modulation signal at the time of pulse shaping by the band limiting filter and further capable of modulating with only one carrier wave. The scheme can be realized, and the intersymbol interference that occurs in principle in this scheme can be eliminated by repeatedly operating the error correction decoder and the turbo equalizer.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Digital modulation signals include modulation signals such as BPSK, QPSK, and 8PSK that are multilevel PSK modulation, and modulation signals such as 16QAM, 64QAM, and 256QAM that are multilevel QAM modulation. In the following, they are generically called digital modulation signals.

  First, the best mode for carrying out the first, second, third and fourth aspects of the digital SSB turbo transceiver will be described. Figure 1 shows the basic configuration of the digital SSB turbo transmitter. As shown in FIG. 1, a digital SSB turbo transmitter according to the present invention includes a CRC encoder 2, an error correction encoder 3, an interleaver 4, a multiplexer 5, a serial / parallel converter 7, a signal It comprises a mapping device 8, a pulse shaping filter 19, a pulse shaping filter 2 10, a transmitter subtractor 11, a transmitter adder 12, and a quadrature modulator 13.

  The digital SSB turbo transmitter performs CRC encoding 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 multiplexer 5 time-multiplexes a pilot signal sequence and an interleaved bit sequence that are known between the transceivers. The output sequence is converted by the serial / parallel converter 7 into two sequences for the in-phase component and the quadrature component. The signal mapper 8 maps the parallel-converted bit sequence to signal points and generates a digital modulation signal. The in-phase component and the quadrature component of the digital modulation signal are converted into an upper sideband signal or a lower sideband signal by the pulse shaping filter 19 and the pulse shaping filter 210. In the following, only the case of the upper sideband will be described.

ｄ_ｎ＝ｂ_Ｉ，ｎ＋ｊｂ_Ｑ，ｎ （２）
となる．次に，パルス整形フィルタ１のインパルス応答をｇ（ｔ），パルス整形フィルタ２の

エ変換は，

リエ変換は

となり，パルス整形フィルタ１ ９と，パルス整形フィルタ２ １０と，送信機用減算器１１と，送信機用加算器１２とからディジタルＳＳＢ変調信号が生成される．Phase component b _I of the digital modulated signal in the n _{symbols, n,} the quadrature component b _Q, and _n, the complex symbols to d _n, the digital modulation signal m of the symbol period T (t) =

d _n = b _{I, n} + jb _{Q, n} (2)
It becomes. Next, the impulse response of the pulse shaping filter 1 is g (t), and the pulse shaping filter 2

D conversion is

Rie conversion

A digital SSB modulation signal is generated from the pulse shaping filter 19, the pulse shaping filter 2 10, the transmitter subtractor 11, and the transmitter adder 12.

搬送波に変調されて，ＲＦ信号として送信される．

Modulated to carrier wave and transmitted as RF signal.

数窓，ハニング窓，ハミング窓，矩形窓等の様々なものが考えられる．指数関数窓を用いる場合には，打ち切りシンボル数をＬとすると，窓関数は

となる．

Various windows such as several windows, Hanning windows, Hamming windows, and rectangular windows can be considered. When using an exponential function window, if the number of censored symbols is L, the window function is

It becomes.

  From the above, according to the best mode for carrying out the present invention, the digital SSB is completely half bandwidth of the digital modulation signal even at the time of pulse shaping by the pulse shaping filter and the pulse shaping filter which is the Hilbert transform. It is possible to realize a digital SSB turbo transmitter that can realize a modulation signal and can only modulate with one carrier wave. In addition, by multiplying the pulse waveform of the pulse shaping filter by the window function, the convolution with a small number of symbols is completed, and the amount of computation and the amount of intersymbol interference observed at the receiver can be reduced.

  Next, the best mode for carrying out the first, fifth, sixth, seventh and eighth aspects of the digital SSB turbo transceiver will be described.

  Figure 2 shows the basic configuration of the digital SSB turbo receiver. As shown in FIG. 2, the digital SSB turbo receiver according to the present invention includes a quadrature demodulator 16, an LPF 17, a matched filter 118, a matched filter 2 19, a receiver adder 20, and a receiver subtractor. 21, a channel estimator 22, a turbo equalizer 24, a deinterleaver 25, an interleaver 26, an error correction decoder 27, an iterative controller 28, and a CRC decoder 29.

となる．パルス整形フィルタ１及びパルス整形フィルタ２の複素整合フィルタのインパルス応答は

をインパルス応答に持つ整合フィルタ２ １９と，受信機用加算器２０と，受信機用減算器２１とによって実現される．このとき，サンプリング時刻ｔ＝ｋＴにおける複素整合フィル

となる．ここで，ｉ_ｋは符号間干渉であり，ｕ_ｋは雑音の整合フィルタ出力である．さらに，

となり，数式（１６），数式（１７）から本発明である受信機により整合フィルタ出力であるディジタル変調受信信号の直交成分と同相成分からｄ_ｋが取り出せることがわかる．ただし，数式（１３）よりチャネル・インパルス応答ｈ（ｔ）が時間的に広がっていない場合にも符号間干渉が発生するため，これを除去または抑圧する必要がある．The quadrature demodulator 16 in the digital SSB turbo receiver performs quadrature demodulation using a carrier wave on the digital SSB modulated received signal, and extracts the in-phase component and the quadrature component of the received signal. The in-phase and quadrature components of the received signal are input to the LPF 17 for baseband reception.

It becomes. The impulse response of the complex matched filter of the pulse shaping filter 1 and the pulse shaping filter 2 is

Is realized by a matched filter 219 having an impulse response, a receiver adder 20, and a receiver subtractor 21. At this time, the complex matched fill at the sampling time t = kT

It becomes. Here, i _k is the intersymbol interference, and u _k is the noise matched filter output. further,

From Equations (16) and (17), it can be seen that d _k can be extracted from the quadrature component and the in-phase component of the digitally modulated received signal as the matched filter output by the receiver of the present invention. However, since the intersymbol interference occurs even when the channel impulse response h (t) does not spread in time from the equation (13), it is necessary to remove or suppress this.

  The channel estimator 22 estimates the channel impulse response between the transmitter and the receiver using the quadrature component and the in-phase component of the digital modulation reception signal. Details of the channel estimator 22 will be described later. The turbo equalizer 24 removes the intersymbol interference from the quadrature component and the in-phase component of the input digital modulation reception signal using the channel estimation value, the interleaved feedback detection signal and the number of repetitions, and outputs the detection signal. Do it.

  Figure 3 shows the configuration of the turbo equalizer in the digital SSB receiver according to the present invention. The turbo equalizer 24 includes a turbo equalizer subtracter 31, a linear filter 32, a tap coefficient generator 33, a soft output detector 34, and an ISI replica generator 35.

  First, the ISI replica generator 35 generates a replica of the ISI component of the digital modulation reception signal using the feedback detection signal and the channel estimation value fed back from the error correction decoder. When the log likelihood ratio is used as the feedback detection signal, the expected value of each digital modulation signal is calculated using the log likelihood ratio and is used as a replica of the digital modulation signal. When a bit sequence in which the received bits are error-corrected coded is used as the feedback detection signal, the bit sequence is serial-to-parallel converted, mapped to a digital modulation signal, and used as a replica of the digital modulation signal. The generated ISI replica is subtracted from the digital modulation reception signal by the turbo equalizer subtractor 31 to remove the ISI component.

Furthermore, the output is input to a linear filter, where the ISI component removal residual is suppressed and noise whitening is performed. When error correction decoding has not yet been performed, ISI replica generation cannot be performed, so suppression of ISI components and whitening of noise are performed by a linear filter. The tap coefficient for the linear filter is generated by the tap coefficient generator 33. The tap coefficient is generated based on the least square method using the number of iterations, the channel estimation value, and the noise power estimation value. The method for deriving the weighting factor is described in detail in Non-Patent Document 3 and Non-Patent Document 4. In Non-Patent Document 3, intersymbol interference occurs in a frequency selective fading environment, and its removal is studied.
D. Reynolds et al., “Low Complexity Turbo-Equalization for Diversity Channels”, Signal Processing, Elsevier Science Publishers, 81 (5) pp. 199 989-995, 2001. H. Fujii et al., “Turbo received with SC / simplified-MMSE (S-MMSE) type equalizer for MIMO channel signal transmission, IEEE VTC 2003, Fall. 1, pp. 632-636, Oct. 2003.

  In contrast, in the present invention, as described above, the intersymbol interference that occurs because the in-phase and quadrature components of the digital modulation signal multiplexed in the upper sideband cannot be completely separated at the matched filter output. That is, in the present invention, it is necessary to remove and suppress both intersymbol interference caused by multipath delay and intersymbol interference due to separation imperfection. Based on Equation (13), the amount of intersymbol interference generated from the convolution integration of the impulse response of the complex shaping filter, the channel impulse response, and the impulse response of the complex matched filter is calculated, and the intersymbol interference is suppressed. Or, tap coefficients that suppress the residual after ISI removal are used. Since the noise component also correlates, the correlation function is calculated from the noise and the impulse response of the matched filter based on Eq. (14), and noise whitening is also realized with a linear filter.

  The removal residual of the ISI component depends on the accuracy of the feedback detection signal and decreases by repeating error correction decoding and turbo equalization. However, estimating the removal residual at each iteration increases the amount of calculation. The tap coefficient generator 33 uses a method in which a removal residual is determined in advance for each iteration described in Non-Patent Document 4.

  The synthesized signal, which is a linear filter, is converted to a detection signal by a soft output detector and output. The detection signal is deinterleaved by the deinterleaver 25, and then error correction decoded by the error correction decoder 27 to output a received bit sequence and a feedback detection signal. There are two types of error correction decoders: soft input soft output decoding that outputs log likelihood ratios as feedback detection signals, and soft input hard output decoding that uses a bit sequence in which received bits are error correction encoded as feedback detection signals. Conceivable.

  With respect to the received bits, a determination error in the packet is detected by CRC decoding in the CRC decoder 29, and an error detection result is output. However, if no decision error is detected, the received bit is output and the reception process ends. The iterative controller 28 inputs an error detection result, and when a determination error is detected, outputs the number of repetitions to the turbo equalizer, the interleaver 26, the turbo equalizer 24, the deinterleaver 25, the error The correction decoder 27 is operated in the order to control the equalization process and the decoding process. Whether the determination error is no longer detected, or if the received signal replica generated using the feedback detection signal and the channel estimation value is subtracted from the received signal and the error amount exceeds the threshold value, the iteration is terminated. Alternatively, the process is repeated up to a predetermined number of repetitions. When a determination error is detected by the CRC decoder, the interleaver 26 interleaves and outputs a feedback detection signal.

  From the above, according to the best mode for carrying out the present invention, a complex matched filter is realized by using the matched filter 1 of the pulse shaping filter 1 and the matched filter 2 of the pulse shaping filter 2. The in-phase and quadrature components of the digital modulation signal can be demodulated from the received signal of the upper sideband or lower sideband digital SSB modulation system. In addition, the intersymbol interference generated in the matched filter output can be removed by repeatedly operating the turbo equalizer and the error correction decoder, and the ISI component removal residual is suppressed and the noise is whitened by the linear filter. Is possible.

  The best mode for carrying out the ninth aspect of the digital SSB turbo transceiver will be described.

  The channel estimator 22 receives the digitally modulated received signal of the pilot signal and estimates the channel impulse response between the transmitter and receiver using a transversal filter. The channel impulse response is estimated as the weighting factor of the transversal filter. First, a pilot signal is input to the transversal filter to generate a replica of the digitally modulated received signal. At that time, the weight coefficient is set to 0 at first. Then, the weight coefficient is updated using the sequential least square method so that the absolute value square value of the difference between the generated replica and the digitally modulated received signal of the pilot signal is minimized, and the final updated value is estimated. Let's say. The RLS algorithm is used as a sequential least square method. However, since the autocorrelation inverse matrix update is a known signal, it can be omitted by calculating and saving in advance. Furthermore, in the data signal section, the digital modulation signal generated from the feedback detection signal is used as a transversal filter. Similarly, the channel impulse response can be estimated by the least squares method. In the data signal section, channel estimation is performed based on the estimated value in the pilot signal section. Therefore, in addition to the RLS algorithm, an LMS algorithm with a slow convergence speed can be used.

  From the above, according to the best mode for carrying out the present invention, a channel impulse response is estimated by a transversal filter in a pilot signal interval, and a digital modulation signal generated from a feedback detection signal in a data signal interval By performing channel estimation using, the processing interval can be extended and the estimation accuracy can be improved. Channel estimation is performed by sequential least squares methods such as RLS algorithm and LMS algorithm, and the amount of calculation can be relatively suppressed, and it can follow even if the propagation path fluctuates in time.

  The best mode for carrying out the tenth aspect of the digital SSB turbo transceiver will be described.

  The digital SSB turbo receiver according to the present invention is an upper side as described above with respect to a digital modulation reception signal received by transmitting a digital modulation signal subjected to error correction coding with a conventional digital modulation transmitter. The waveband component is extracted by the matched filter 1 and the matched filter 2, and the detection signal 1 is calculated by removing intersymbol interference by a turbo equalizer. Next, in the digital SSB turbo receiver of FIG. 2, the receiver adder 20 and the receiver subtractor 21 are replaced, and the lower sideband components are extracted by the matched filter 1 and the matched filter 2, and the turbo etc. The detection signal 2 is calculated by removing the intersymbol interference by the encoder. The detection signal 1 and the detection signal 2 are optimally combined according to the communication quality of the upper sideband component and the lower sideband component, and error correction decoding is performed after interleaving. If a decision error is detected, turbo equalization and error correction decoding are repeated to further eliminate intersymbol interference.

  From the above, according to the best mode for carrying out the present invention, in the frequency selective fading channel, when the power of the upper sideband component and the lower sideband component of the received signal is significantly reduced, the upper sideband By applying a digital SSB turbo receiver that detects only in the lower band or the lower sideband, the transmission characteristics can be improved by extracting and combining the detected signals from the upper and lower sidebands.

  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 digital SSB turbo transmitter by this invention. It is a figure which shows the basic composition of the digital SSB turbo receiver by this invention. It is a figure which shows the structure of the turbo equalizer in the digital SSB turbo receiver by this invention.

Explanation of symbols

1: transmission bit input terminal, 2: CRC encoder, 3: error correction encoder, 4: interleaver, 5: multiplexer, 6: pilot signal input terminal, 7: serial / parallel converter, 8: signal mapper, 9: Pulse shaping filter 1, 10: Pulse shaping filter 2, 11: Transmitter subtractor, 12: Transmitter adder, 13: Quadrature modulator, 14: Transmission signal output terminal, 15: Reception signal input terminal, 16: Quadrature demodulator, 17: LPF, 18: matched filter 1, 19: matched filter 2, 20: receiver adder, 21: receiver subtractor, 22: channel estimator, 23: pilot signal input terminal , 24: turbo equalizer, 25: deinterleaver, 26: interleaver, 27: error correction decoder, 28: repetition controller, 29: CRC decoder, 30: output received bit Terminal, 31: turbo equalization dexterity subtractor, 32: linear filter, 33: tap coefficient generator 34: soft output detector, 35: ISI replica generator

Claims (10)

Using the pulse shaping filter 1 that limits the band and the pulse shaping filter 2 that realizes the impulse response that is the Hilbert transform of the impulse response, the in-phase component and the quadrature component of the error-modulated coded digital modulation signal are used as the upper wave. A digital SSB turbo transmitter that modulates a single sideband (SSB) of a band or lower sideband;
Using the matched filter 1 of the pulse shaping filter 1 and the matched filter 2 of the pulse shaping filter 2, the in-phase component and the quadrature component of the digital modulation signal from the received signal in the upper sideband or the lower sideband. And a digital SSB turbo receiver that removes the intersymbol interference generated in the matched filter output by repeatedly operating the turbo equalizer and the error correction decoder,
The digital SSB turbo transmitter can realize the same transmission rate with a half bandwidth of a normal digital modulation signal, and the digital SSB turbo receiver can demodulate the digital SSB modulation signal and eliminate intersymbol interference. A digital SSB turbo transceiver.   The digital SSB turbo transmitter includes a cyclic redundancy check (CRC) encoder, an error correction encoder, an interleaver, a multiplexer, a serial / parallel converter, a signal mapper, the pulse shaping filter 1, The digital SSB turbo transceiver according to claim 1, comprising the pulse shaping filter 2, a transmitter subtractor, a transmitter adder, and a quadrature modulator. 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;
The interleaver inputs the encoded bit sequence and outputs an interleaved bit sequence;
The multiplexer inputs a known pilot signal sequence between the transmitter and the receiver and the interleaved bit sequence, and multiplexes and outputs the respective sequences in time,
The serial / parallel converter inputs the interleaved bit sequence or the pilot sequence, performs parallel conversion into two sequences for in-phase component and quadrature component, and outputs a bit sequence,
The signal mapper maps the parallel-converted bit sequence to a signal point and outputs a digital modulation signal;
The pulse shaping filter 1 receives the digital modulation signal, convolves a band-limiting pulse waveform, and outputs a digital modulation signal after pulse shaping,
The pulse shaping filter 2 receives the digital modulation signal, convolves a pulse waveform obtained by Hilbert transforming the band limiting pulse waveform of the pulse shaping filter 1, and outputs a digital modulation signal after pulse shaping,
The transmitter subtractor inputs the in-phase component of the digital modulation signal to the pulse shaping filter 1 and inputs the quadrature component of the digital modulation signal to the pulse shaping filter 2 from the output digital modulation signal after the pulse shaping. And subtracting the output digital modulated signal after the pulse shaping so as to output the in-phase component of the digital SSB modulated signal,
The transmitter adder inputs the in-phase component of the digital modulation signal to the pulse shaping filter 2 and inputs the quadrature component of the digital modulation signal to the pulse shaping filter 1 to the output digital modulation signal after the pulse shaping. And adding the output digital modulation signal after the pulse shaping so as to output a quadrature component of the digital SSB modulation signal,
3. The digital SSB turbo transceiver according to claim 2, wherein the quadrature modulator receives an in-phase component and a quadrature component of the digital SSB modulation signal, performs quadrature modulation using a carrier wave, and generates a digital SSB modulated transmission signal. .   The pulse shaping filter 1 uses a pulse waveform obtained by multiplying a band limiting pulse waveform by a window function as the pulse waveform, and the pulse shaping filter 2 uses a pulse obtained by Hilbert transforming the band limiting pulse waveform as the pulse waveform. The digital SSB turbo transceiver according to claim 2, wherein a pulse waveform obtained by multiplying the waveform by a window function is used.   The digital SSB turbo receiver includes an orthogonal demodulator, a low-pass filter (LPF), the matched filter 1, the matched filter 2, a receiver adder, a receiver subtractor, and a channel estimation. 2. The digital SSB turbo transceiver according to claim 1, comprising: a detector, a turbo equalizer, a deinterleaver, an interleaver, the error correction decoder, an iterative controller, and a CRC decoder. . The quadrature demodulator receives a digital SSB modulated received signal, performs quadrature demodulation using a carrier wave, and outputs an in-phase component and a quadrature component of the received signal;
The LPF inputs in-phase components or quadrature components of the received signal, extracts only the in-phase components or quadrature components of the baseband received signal, and outputs them.
The matched filter 1 receives the baseband received signal, convolves a pulse waveform that matches the band-limiting pulse waveform of the pulse shaping filter 1, and outputs a matched baseband received signal;
The matched filter 2 receives the baseband received signal, convolves a pulse waveform that matches the pulse waveform of the pulse shaping filter 2, and outputs a matched baseband received signal;
The receiver adder inputs an in-phase component of the baseband received signal to the matched filter 1 and outputs an orthogonal component of the baseband received signal to the matched baseband received signal. The matched baseband received signal that has been input and output is added, and the in-phase component of the digitally modulated received signal is output.
The subtractor for the receiver inputs the quadrature component of the baseband received signal to the matched filter 1 and outputs the in-phase component of the baseband received signal from the matched baseband received signal that has been output. Subtract the matched baseband received signal that was input and output, and output the quadrature component of the digitally modulated received signal,
The channel estimator inputs a quadrature component and an in-phase component of the digital modulation reception signal, estimates a channel impulse response between the transceivers, and outputs a channel estimation value.
The turbo equalizer receives the quadrature component and the in-phase component of the digital modulation reception signal, removes intersymbol interference using the interleaved feedback detection signal, the channel estimation value and the number of repetitions, and outputs a detection signal Like
The deinterleaver inputs the detection signal, deinterleaves it, and outputs it.
The error correction decoder inputs the detection signal after deinterleaver, performs error correction decoding, and outputs a received bit sequence and the feedback detection signal,
The CRC decoder receives the received bit, performs CRC decoding, detects a determination error in the packet, and outputs an error detection result and a received bit when no determination error is detected. ,
The interleaver inputs the feedback detection signal, interleaves it, and outputs it,
The repetition controller inputs the error detection result, and when a determination error is detected, outputs the number of repetitions to the turbo equalizer, the interleaver, the turbo equalizer, and the error correction. 6. The digital SSB turbo transceiver according to claim 5, wherein the digital SSB turbo transceiver is operated in the order of the decoder, and performs control to repeat equalization processing and decoding processing.   6. The turbo equalizer includes a turbo equalizer subtracter, a linear filter, a soft output detector, an intersymbol interference (ISI) replica generator, and a tap coefficient generator. Digital SSB turbo transceiver. The ISI replica generator receives the interleaved feedback detection signal and the channel estimation value, and generates and outputs a replica of an intersymbol interference component (ISI replica) of the digital modulation reception signal,
The subtractor subtracts the ISI replica from the digitally modulated received signal, and the tap coefficient generator uses the repetition count and the channel estimation value to calculate an intersymbol interference or an intersymbol interference cancellation residual. Generating tap coefficients for the linear filter based on the least square method for suppressing and whitening noise;
The linear filter receives the digital modulation reception signal after the ISI replica subtraction, performs linear synthesis using the tap coefficient, and outputs a synthesis signal;
The turbo equalizer according to claim 7, wherein the soft output detector receives the combined signal and generates the detection signal.   The channel estimator inputs a digital modulation signal generated using the pilot signal sequence or the feedback detection signal to a transversal filter to generate a reception signal replica, and generates a reception signal replica and the digital modulation reception signal. 6. The digital SSB turbo transceiver according to claim 5, wherein the channel impulse response is estimated as a tap coefficient of the transversal filter using a least square method so that an absolute value square value of the difference is minimized.   6. The digital SSB turbo reception according to claim 5, wherein an error correction coded digital modulation signal is transmitted by a conventional digital modulation transmitter, and an upper sideband component is used for the received signal of the digital modulation signal. And detecting with the digital SSB turbo receiver according to claim 5 using the lower sideband component, and optimally combining the detection results to obtain the transmission characteristics in the frequency selective fading channel. The digital SSB turbo transceiver according to claim 1 to be improved.

Images