JP2011166329A - Equalization processing device and receiving apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an equalizer achieving high equalization performance, independent of existence of a known signal. <P>SOLUTION: An equalization processing part 15a includes: a transfer function calculating part 33; a noise eliminating part 34; a delay part 35; an equalization part 31; and a reference point calculating part 32. The equalization processing part 15a performs equalization for a signal received by OFDM (Orthogonal Frequency Division Multiplexing). The transfer function calculating part 33 calculates a transfer function of a transmission line. The noise eliminating part 34 removes noise contained in the transfer function. The delay part 35 delays the transfer function after noise elimination by one symbol and outputs it. The equalization part 31 equalizes the received signal using the output of the delay part 35. The reference point calculating part (transmission signal estimator) 32 estimates a transmission signal based on the output of the equalization part 31. The transfer function calculating part 33 calculates the transfer function, based on the received signal and the estimated transmission signal by the reference point calculating part 32. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an equalization processing device and a reception device including the equalization processing device.

[About OFDM]
Orthogonal frequency division multiplexing (hereinafter, also referred to as OFDM) scheme that multiplexes a number of carriers orthogonal to each other is used in various communication systems. An OFDM signal transmitted by the OFDM method is formed from a plurality of symbols that are continuous in the time direction, as shown in FIG. Each symbol forming the OFDM signal is formed by a plurality of subcarriers (hereinafter also simply referred to as carriers) orthogonal to each other. In the transmission apparatus, each carrier is modulated by a QPSK (Quadrature Phase Shift Keying) method or the like.

[About ISDB-T and DAB]
In a type of communication system using the OFDM system, a known signal may be inserted into an OFDM signal, as in Japanese adopted standard for terrestrial digital broadcasting: ISDB-T (Integrated Services Digital Broadcasting-Terrestrial). This known signal is generally called a pilot signal and has a fixed pattern known to the receiving apparatus. In ISDB-T, a known signal is inserted into each symbol.

  On the other hand, there is a system in which a known signal is not provided for each symbol, such as DAB (Digital Audio Broadcasting) in Europe. In DAB, as shown in FIG. 12B, a plurality of symbols are grouped in units of transmission frames. FIG. 12B shows the configuration of a transmission frame in a certain transmission mode of DAB. In one transmission frame in DAB, the first symbol is a null symbol to which no data is assigned, and the second symbol is a phase reference symbol (hereinafter also referred to as PRS) in which all of the symbols are known signals. The third and subsequent symbols are symbols that contain data and do not contain a known signal. Each carrier in PRS is modulated by the QPSK system. Each symbol after PRS is modulated by a π / 4-shift DQPSK (Differential Quadrature Phase Shift Keying) method.

[About QPSK]
The PSK (Phase Shift Keying) method is a method for realizing modulation by changing the phase of a signal. In the QPSK (Quadrature Phase Shift Keying) method which is a kind of PSK method, four phases are used.

  When two pieces of information data at a discrete time k are represented by a [k] and b [k], in the QPSK system, any of the four types of phase states is applied to the information data a [k] and b [k]. QPSK signal v [k] having the above is assigned. Each of a [k] and b [k] is 1-bit data that takes 0 or 1. k is an integer. a [k], b [k], and v [k] represent the first information data, the second information data, and the QPSK signal at time k, respectively. The time at which the unit time has elapsed from time (k−1) is time k, and the time at which the unit time has elapsed from time k is time (k + 1).

The QPSK signal v [k], which is a complex signal, has four signal points (−1 / √2, 1 / √2), (1 / √2, 1 / √2),
(-1 / √2, -1 / √2), (1 / √2, -1 / √2)
It becomes either.

In the QPSK system in DAB, four phase states as shown in FIG. 13 are assigned to 2-bit information data (FIG. 13 is a diagram showing a constellation of the QPSK system). That is, the QPSK signal v [k]
v [k] = ((1-2a [k]) + j (1-2b [k])) / √2
Represented by In the present specification, j represents an imaginary unit, and √2 represents a positive square root of 2. In FIG. 13, each of the notations “00”, “10”, “11”, and “01” represents 2-bit information data, and in each of these notations, the numerical value on the left indicates the value of the upper bit. The numerical value on the right indicates the value of the lower bit.

  In this specification, when the real part and the imaginary part of an arbitrary complex signal are represented by Re and Im, respectively, the complex signal may be represented by “Re + j · Im” or (Re, Im). In a complex signal, the real part is called an in-phase component and the imaginary part is called a quadrature component. Further, as adopted in general digital modulation / demodulation considerations, the in-phase component and the quadrature component are assigned the I-axis and the Q-axis, respectively, and the complex plane is referred to as the IQ plane. The Q axis is obtained by rotating the I axis counterclockwise by 90 ° in the counterclockwise direction (phase advance direction), and the I axis and the Q axis intersect at the origin of the IQ plane. A point where a complex signal represented by “Re + j · Im” should be arranged on the IQ plane is represented as a signal point (Re, Im). Unless otherwise stated, in the following description, a signal point refers to a signal point on the IQ plane, and an origin refers to the origin of the IQ plane.

[About DQPSK]
In the DPSK (Differential Phase Shift Keying) method, information data is transmitted by a change in the phase of a transmission signal. In the π / 4-shift DQPSK (hereinafter simply referred to as DQPSK) system, which is a type of DPSK, as shown in the following equation (A1), a QPSK signal v [ k] is multiplied by the previously transmitted signal x [k-1] to obtain the signal x [k] to be transmitted this time. That is, modulation is performed by assigning information to the phase difference between the signal transmitted last time and the signal transmitted this time.
x [k] = x [k−1] · v [k] (A1)

  x [k] and x [k−1] are signals modulated by the DQPSK system, and they are called DQPSK modulated signals. x [k−1] is a DQPSK modulated signal at time (k−1), and x [k] is a DQPSK modulated signal at time k. The first DQPSK signal x [1] is set to x [1] = v [1] (that is, a QPSK signal).

The process of multiplying an arbitrary signal point on the IQ plane by the QPSK signal v [k] is equivalent to the process of rotating the position of the signal point by 315 °, 45 °, 135 ° or 225 °. Therefore, as can be seen from the equation (A1), the signal point of the DQPSK modulated signal is one of the four first signal points shown in FIG. 14A or the four second signal points shown in FIG. 14B. Thus, a state where the signal point of the DQPSK modulation signal becomes the first signal point and a state where the signal point of the DQPSK modulation signal becomes the second signal point alternately occur.
The first signal point group includes four signal points (−1 / √2, 1 / √2), (1 / √2, 1 / √2),
(-1 / √2, -1 / √2), (1 / √2, -1 / √2)
Consisting of
The second signal point group includes four signal points (1, 0), (0, 1), (-1, 0), (0, -1).
Consists of.

  When the DQPSK system is used in a communication system using an OFDM signal such as DAB, modulation by the DQPSK system is performed for each carrier. That is, for example, modulation is performed by assigning information to the phase difference between the qth carrier in the kth symbol and the qth carrier in the (k−1) th symbol (k and q are integers).

[About equalization]
If the signal transmitted from the transmitting device is represented by X and the signal received by the receiving device is represented by Y, these satisfy the relationship of the following equation (A2). Here, H is a transfer function. The transfer function H changes due to the influence of multipath, etc., and the phase rotation and amplitude increase / decrease of the transmission signal occur according to the transfer function H. In the expression (A2), the influence of noise is ignored.
Y = H · X (A2)

The transfer function depends on the frequency, and the function value changes with time due to movement of the receiving device. Therefore, when reception processing is performed using the received signal Y as it is, an erroneous signal may be demodulated or reception performance may deteriorate. Therefore, the receiving apparatus obtains a function H ′ that is an estimate of the transfer function H, and estimates the transmission signal X by the following equation (A3). Such processing is called equalization. X ′ is an estimated transmission signal, and X = X ′ when the estimation is ideally performed.
X ′ = Y / H ′ (A3)

H ′ is obtained by Expression (A4) based on the signal Y received by the receiving device and the estimated transmission signal (or known signal) X ″.
H ′ = Y / X ″ (A4)

JP 2008-118194 A JP 2008-17094 A

  As a conventional equalizer (equalization processing device), an equalizer that calculates a transfer function using a known signal (pilot signal) included in a signal and performs equalization in the frequency domain using the transfer function Is known (see, for example, Patent Document 1). In such an equalizer, high equalization performance can be realized by performing equalization in the frequency domain. However, this equalizer is an equalizer that assumes that a known signal is included in each symbol, such as ISDB-T, and when there is a symbol that does not include a known signal, such as DAB. , Not available.

  As another equalizer, an adaptive equalizer that performs equalization using a transversal filter or the like in the time domain is known (see, for example, Patent Document 2). According to such an application equalizer, equalization can be realized even when a known signal is not included in each symbol. However, since a transversal filter that functions in the time domain is used, compared with a method of performing equalization in the frequency domain, the required amount of computation increases and the equalization performance may be insufficient.

  Therefore, an object of the present invention is to provide an equalization processing device and a reception device that can realize equalization with high equalization performance without depending on the presence or absence of a known signal.

  A first equalization processing apparatus according to the present invention derives a transfer function of the transmission path in an equalization processing apparatus that generates an equalized signal by performing equalization of a received signal received via the transmission path. A transfer function deriving unit, a delay unit for delaying and outputting an equalization function based on the transfer function, and generating the equalized signal by equalizing the received signal using the output of the delay unit, etc. And a transmission signal estimation unit that estimates a transmission signal corresponding to the reception signal based on the equalization signal from the equalization unit, and the transfer function derivation unit includes the reception signal and the transmission The transfer function is derived based on the estimated transmission signal by the signal estimation unit.

  A second equalization processing apparatus according to the present invention derives a transfer function of the transmission path in an equalization processing apparatus that generates an equalized signal by equalizing a received signal received via the transmission path. A transfer function deriving unit, a first equalization unit that generates the equalized signal by equalizing the received signal using an equalization function based on the transfer function, and the first equalization unit A delay unit that delays and outputs the equalization function, a second equalization unit that tentatively equalizes the received signal based on the output of the delay unit, and an output of the second equalization unit A transmission signal estimation unit that estimates a transmission signal corresponding to the reception signal based on the transmission function, and the transfer function derivation unit calculates the transfer function based on the reception signal and the transmission signal estimated by the transmission signal estimation unit. It is derived.

  A third equalization processing apparatus according to the present invention derives a transfer function of the transmission path in an equalization processing apparatus that generates an equalized signal by equalizing a received signal received via the transmission path. A transfer function deriving unit; a delay unit that delays and outputs an equalization function based on the transfer function; and the received signal using an equalization function before delay by the delay unit or an equalization function after delay And a transmission signal estimation unit that estimates a transmission signal corresponding to the received signal based on the equalization result of the equalization unit, and executes the second process after the first process The equalization unit generates the equalized signal, and in the first process, the equalization unit temporarily equalizes the received signal using the delayed equalization function. By generating a provisional equalization signal and providing the provisional equalization signal to the transmission signal estimation unit. The transfer function deriving unit derives the transfer function using the estimated transmission signal generated by the transmission signal estimating unit and the received signal, and in the second process, the transfer derived in the first process is performed. The equalization unit is caused to equalize the received signal by giving the equalization function based on a function to the equalization unit without passing through the delay unit, thereby generating the equalization signal. To do.

  According to the first, second, or third equalization processing device, the received signal can be equalized without depending on the presence or absence of a known signal. In addition, since equalization can be performed in the frequency domain, high equalization performance can be realized.

  Further, for example, in the first, second, or third equalization processing device, the noise of the transfer function output from the transfer function deriving unit is reduced, and the transfer function after the noise reduction is changed to the function for equalization. It is preferable to further provide a noise reduction unit generated as follows.

  Also, for example, in the first, second, or third equalization processing device, when the transfer function deriving unit is a signal obtained by receiving a predetermined known signal, The transfer function may be derived based on the received signal and the known signal, and in other cases, the transfer function may be derived based on the received signal and the estimated transmission signal.

  As a result, a more accurate transfer function can be derived as compared with the case where no known signal is used.

  Further, for example, in the first, second, or third equalization processing apparatus, the received signal may be an OFDM signal transmitted using OFDM, and the delay unit is connected to the noise reduction unit. The output transfer function after noise reduction may be output after being delayed by one symbol.

  A receiving apparatus according to the present invention includes any of the above equalization processing apparatuses.

  According to the present invention, it is possible to provide an equalization processing device and a reception device that can realize equalization with high equalization performance without depending on the presence or absence of a known signal.

  The significance or effect of the present invention will become more apparent from the following description of embodiments. However, the following embodiment is merely one embodiment of the present invention, and the meaning of the term of the present invention or each constituent element is not limited to that described in the following embodiment. .

1 is a configuration diagram of a communication system according to an embodiment of the present invention. It is a schematic block diagram of the receiver which concerns on embodiment of this invention. It is a figure which shows the structure of the OFDM signal output from the FFT part of FIG. It is an internal block diagram of the equalization process part which concerns on 1st Example of this invention. It is an internal block diagram of the noise removal part which concerns on 1st Example of this invention. FIG. 5A shows the state of time-series power data calculated by the power calculation unit in FIG. 5 and the power of the transfer function in the time domain output from the comparison and extraction unit in FIG. 5 to the FFT unit. It is a figure (b) showing a situation. It is an internal block diagram of the equalization process part which concerns on 2nd Example of this invention. It is an internal block diagram of the equalization process part which concerns on 3rd Example of this invention. It is an internal block diagram of the equalization process part which concerns on 4th Example of this invention. It is an internal block diagram of the equalization process part which concerns on 5th Example of this invention. It is an internal block diagram of the equalization process part which concerns on 6th Example of this invention. FIG. 4A is a diagram showing a symbol string in an OFDM signal according to the prior art, and FIG. It is a figure which shows the constellation of a QPSK system according to a prior art. It is a figure which concerns on a prior art and shows the constellation of a DQPSK system.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In each of the drawings to be referred to, the same part is denoted by the same reference numeral, and redundant description regarding the same part is omitted in principle. The matters described above in the description of the background art also apply to this embodiment as long as there is no contradiction. If the items described above in the background art description column and the items described in the present embodiment contradict each other, the items described in the present embodiment take precedence.

  FIG. 1 shows a configuration diagram of a communication system according to an embodiment of the present invention. The communication system in FIG. 1 includes a transmission device 1 and a reception device 2. FIG. 2 shows a schematic block diagram of the receiving device 2. The receiving device 2 is, for example, a digital broadcast receiving device that receives a digital broadcast.

  In the communication system of FIG. 1, an OFDM (Orthogonal Frequency Division Multiplexing) system is adopted as a transmission system. The OFDM scheme is a scheme in which Q subcarriers (as described above, subcarriers are also simply referred to as carriers) are multiplexed within one channel band. Q is an integer of 2 or more. The frequencies of the Q carriers are different from each other, and the Q carriers are orthogonal to each other in accordance with the OFDM scheme.

  In the transmission device 1, for each carrier, the carrier is modulated in accordance with the baseband signal to be transmitted, and the signal obtained by the modulation is subjected to an inverse fast Fourier transform (IFFT) to thereby generate an OFDM signal. Is generated. A radio signal based on the generated OFDM signal is transmitted from the transmission device 1 to the reception device 2. The baseband signal includes a video signal and an audio signal to be transmitted, and is a source of the first information data a and the second information data b. In the present embodiment, it is assumed that the QPSK method or the DQPSK method is used as the modulation method as necessary.

  The receiving device 2 includes a receiving antenna 11, an RF unit 12, a synchronization processing unit 13, an FFT unit 14, an equalization processing unit 15 that can also be referred to as an equalizer or an equalization processing device, a soft decision unit 16, A decryption processing unit 17.

  The reception antenna 11 receives the radio signal from the transmission device 1. The RF unit 12 extracts only a signal in a desired frequency band from the received signal of the receiving antenna 11, converts the frequency of the extracted signal into a baseband frequency, performs Hilbert transform on the extracted signal, and converts these signals The subsequent extraction signal is output to the synchronization processing unit 13.

  The output signal of the RF unit 12 is an OFDM signal formed from a plurality of symbols continuous in the time direction. The synchronization processing unit 13 performs synchronization processing for extracting a signal for each symbol from the output signal of the RF unit 12 and performs necessary frequency correction and the like, and outputs the processed OFDM signal to the FFT unit 14.

  The FFT unit 14 converts the OFDM signal in the time domain output from the synchronization processing unit 13 into a signal in the frequency domain using a fast Fourier transform (FFT). The OFDM signal in the frequency domain obtained by this conversion is output from the FFT unit 14 to the equalization processing unit 15.

  The equalization processing unit 15 performs equalization processing for removing distortion included in the OFDM signal from the FFT unit 14, and outputs the equalized OFDM signal. This distortion is distortion caused by multipath or the like generated on the transmission path. In the present embodiment, the transmission path refers to a transmission path between the transmission device 1 and the reception device 2.

  The soft decision unit 16 performs soft decision on the information data of each carrier in each symbol based on the output signal of the equalization processing unit 15 which is an OFDM signal after equalization processing, and determines a soft decision value representing the result of the soft decision. The data is output to the decryption processing unit 17. The decoding processing unit 17 performs Viterbi decoding based on the soft decision value from the soft decision unit 16, so that the values of the first information data a and the second information data b used for modulation are “0”. Alternatively, it is finally determined whether it is “1”.

  The information data a and b are, for example, MPEG (Moving Picture Experts Group) encoded data obtained by encoding a video signal or an audio signal. The MPEG encoded data restored by the decoding processing unit 17 is sent to an MPEG decoder (not shown), decoded, sent to a display device or a speaker (both not shown), and displayed as video or output as audio. Is done. The receiving device 2 can also include an MPEG decoder, a display device, and a speaker.

  In addition, before the Viterbi decoding by the decoding processing unit 17, a deinterleaving processing unit (not shown) may perform a deinterleaving process. Alternatively, the deinterleave processing unit may be provided before the soft decision unit 16. Further, the output of the decoding processing unit 17 may be given to a Reed-Solomon decoding unit (not shown) to decode the Reed-Solomon code.

  As shown in FIG. 3, the OFDM signal output from the FFT unit 14 is composed of signals that are two-dimensionally arranged in the frequency direction and the time direction (hereinafter, each two-dimensionally arranged signal is referred to as a carrier signal). This is called an OFDM symbol sequence. The frequency direction and the time direction are also called a carrier direction and a symbol direction, respectively.

  A symbol number (time number) corresponding to the time direction is represented by a variable k, and a carrier number corresponding to the frequency direction is represented by a variable q. k is an integer of 1 or more, and q is an integer of 1 or more and Q or less. Q is the total number of carriers forming the OFDM signal. As described above, the Q carriers forming the OFDM signal have different frequencies and the Q carriers are orthogonal to each other. It is assumed that the frequency of the corresponding carrier increases as q increases. k represents a discrete time considering the symbol length of the OFDM signal as a unit. The time corresponding to the symbol length of the OFDM signal is defined as a unit time, and the time when the unit time has elapsed from time k is time (k + 1). A position in the OFDM symbol string is called a carrier position, and a carrier position at symbol number k and carrier number q is represented by a symbol [k, q]. This symbol may also be used as a symbol representing the carrier itself. That is, the carrier of the carrier number q in the symbol number k may be expressed as carrier [k, q].

  Furthermore, the carrier signal arranged at the carrier position [k, q] is represented by y [k, q]. The carrier signal y [k, q] is obtained by extracting the signal from the carrier of the carrier number q in the symbol number k from the OFDM signal output from the FFT unit 14. Therefore, each symbol forming the OFDM symbol string is composed of Q carrier signals. That is, for example, in the OFDM symbol string, the symbol at time k is composed of Q carrier signals y [k, 1] to y [k, Q].

  The transmission apparatus 1 generates a QPSK signal by modulating each carrier with two pieces of information data in each symbol. The QPSK signal at symbol number k and carrier number q is represented by v [k, q], and information data a and b at symbol number k and carrier number q are represented by a [k, q] and b [k, q]. To express. Each of a [k, q] and b [k, q] is 1-bit digital data that takes 0 or 1. a [k, q] corresponds to the upper bits and b [k, q] corresponds to the lower bits.

Similar to the QPSK signal v [k] described above, the signal point of the complex signal QPSK signal v [k, q] has four signal points (−1 / √2, 1 / √2) and (1 / √2). , 1 / √2),
(-1 / √2, -1 / √2), (1 / √2, -1 / √2)
It becomes either.

As shown in FIG.
v [k, q] = ((1-2a [k, q]) + j (1-2b [k, q])) / √2
The QPSK signal v [k, q] is generated so that As described above, in the present specification, j represents an imaginary unit, and √2 represents a positive square root of 2.

  The transmission apparatus 1 can send the QPSK signal v [k, q] to the reception apparatus 1 as it is as the transmission signal x [k, q]. In this case, v [k, q] = x [k, q].

  Alternatively, a transmission signal x [k, q] according to the DQPSK method can be transmitted to the receiving device 1. When using the DQPSK system, the transmission apparatus 1 can perform modulation using the DQPSK system for each carrier. In this case, x [k, q] = x [k−1, q] · v [k, q].

  The equalization processing unit 15 performs equalization processing for each symbol and for each carrier. The carrier signal y [k, q] is also referred to as a received signal y [k, q]. A signal obtained by performing equalization processing on the reception signal, that is, the reception signal after equalization processing is called an equalization signal, and the equalization signal of the reception signal y [k, q] is particularly x ′ [k, q]. Represented by Equalized signals (x ′ [1,1] to [1, Q], x ′ [2,1] to [2, Q],...) Derived for each symbol and for each carrier are equalized. The soft decision in the soft decision unit 16 is executed based on the equalized signal output from the unit 15 to the soft decision unit 16.

  The equalization processing unit 15 has a characteristic function, and the configuration and operation examples of the equalization processing unit 15 will be described below as first to sixth examples. The matters described above in the present embodiment are applied to the following examples. As long as there is no contradiction, the matters described in one embodiment can be applied to other embodiments.

<< First Example >>
A first embodiment will be described. The first embodiment assumes a case where no known signal is inserted in the OFDM signal (however, it may be inserted). The known signal is a signal having a fixed pattern known to the received signal 2 and is generally called a pilot signal. FIG. 4 is an internal block diagram of the equalization processing unit 15a according to the first embodiment. In the first embodiment, the equalization processing unit 15a is used as the equalization processing unit 15 in FIG. The equalization process part 15a is provided with each site | part referred with the codes | symbols 31-35. The OFDM signal output from the FFT unit 14 is input to the equalization unit 31 and the transfer function calculation unit 33.

  The equalization unit 31 generates and outputs an equalized signal for each carrier by equalizing the carrier signal output from the FFT unit 14 using the transfer function output from the delay unit 35. The reference point calculation unit 32 has a function as a transmission signal estimation unit, and estimates and outputs a transmission signal for each carrier based on the equalized signal output from the equalization unit 31. The transfer function calculator 33 calculates and outputs a transfer function for each carrier based on the carrier signal output from the FFT unit 14 and the estimated transmission signal output from the reference point calculator 32. The noise removing unit 34 removes noise included in the transfer function output from the transfer function calculating unit 33, and outputs the transfer function after the noise removal. The delay unit 35 delays the transfer function after noise removal output from the noise removal unit 34 by a unit time (ie, one symbol), and outputs the transfer function having the delay to the equalization unit 31.

  Hereinafter, the process of generating the equalized signal x ′ [k, q] from y [k, q] will be specifically described with attention paid to the received signal y [k, q] for a certain carrier. The symbol number k is regarded as the current symbol, the symbol number (k−1) is regarded as the previous symbol, and the symbol number (k + 1) is regarded as the next symbol (also in other embodiments described later). The same). For convenience, a section in which the equalized signal x ′ [k, q] is generated from the received signal y [k, q] is called a current symbol section, and the equalized signal x ′ [k] is received from the received signal y [k−1, q]. −1, q] is referred to as a previous symbol period, and an interval for generating the equalized signal x ′ [k + 1, q] from the received signal y [k + 1, q] is referred to as a next symbol period (other symbols described later). The same applies to the examples).

In the current symbol period, the transfer function output from the transfer function calculation unit 33 is represented by h ₀ [k, q], the transfer function output from the noise reduction unit 34 is represented by h ₁ [k, q], The transfer function output from the delay unit 35 is represented by h ₁ [k−1, q]. In previous symbol interval, the received signal y [k-1, q] transmitted by the transfer function calculating unit 33 using the function _{h 0 [k-1, q} ] is determined, transmitted by the noise removal unit 34 functions h ₀ [k The transfer function h ₁ [k-1, q] is obtained by removing the noise of −1, q]. The transfer function h ₁ [k−1, q] is output from the delay unit 35 in the current symbol period. The following description is an explanation of the operation in the current symbol period unless otherwise specified.

The equalization unit 31 equalizes the received signal y [k, q] using the transfer function h ₁ [k−1, q] output from the delay unit 35 to equalize the signal x ′ [k, q ] Is generated and output. For example, the equalized signal x ′ [k, q] can be obtained by the following equation (B1).
x ′ [k, q] = y [k, q] / h ₁ [k−1, q] (B1)

Alternatively, using the _{h 1 [k-1, q} ] is the complex conjugate of ^{_{h 1 * [k-1,}} q] , and may be obtained x '[k, q] by the following formula (B2) . Thereby, the execution of division is avoided, and it becomes possible to reduce the required calculation amount and to reduce the size of the hardware. Further alternatively, x ′ [k, q] may be obtained by the following formula (B3). If Expression (B3) is used, it is possible to remove the influence of amplitude fluctuation of the received signal. | H ₁ [k−1, q] | represents the magnitude (amplitude) of h ₁ [k−1, q] expressed as a complex signal.
x ′ [k, q] = y [k, q] · h ₁ ^* [k−1, q] (B2)
x ′ [k, q] = y [k, q] · | h ₁ [k−1, q] | / h ₁ [k−1, q]
... (B3)

The reference point calculation unit 32 estimates the transmission signal x [k, q] corresponding to the reception signal y [k, q] based on the equalization signal x ′ [k, q] from the equalization unit 31. A signal obtained by estimating the transmission signal x [k, q] in the reference point calculation unit 32 is represented by x _E [k, q]. If the estimate is ideal, x _E [k, q] = x [k, q]. The reference point calculation unit 32 can specify a transmission signal closest to the equalized signal x ′ [k, q] on the constellation, and can estimate the specified transmission signal as x _E [k, q].

For example, when each carrier is modulated by the QPSK system in the transmission apparatus 1, the signal point of the transmission signal x [k, q] is “(1 / √2, 1 / √2)”, “(−1 / √2, 1 / √2) ”,“ (−1 / √2, −1 / √2) ”and“ (1 / √2, −1 / √2) ”. Therefore, when each carrier is modulated by the QPSK method, for example, if the signal point of the equalized signal x ′ [k, q] is (0.3,0.8), “x _E [k, q ] = (1 + j) / √2 ”, and if the signal point of the equalized signal x ′ [k, q] is (−0.3,0.8),“ x _E [k, q] = ( -1 + j) / √2 ".

Or, for example, when each carrier is modulated by the DQPSK method in the transmission apparatus 1, the signal point of the transmission signal x [k, q] is one of the first signal points shown in FIG. This is one of the second signal points shown in FIG. Therefore, when each carrier is modulated by the DQPSK method, when the signal point of the transmission signal x [k, q] is any of the first signal points, for example, the equalization signal x ′ [k, q] If the signal point is (0.3, 0.8), “x _E [k, q] = (1 + j) / √2”. Similarly, when the signal point of the transmission signal x [k, q] is any of the second signal points, for example, the signal point of the equalized signal x ′ [k, q] is (0.3, 0. If 8), “x _E [k, q] = 0 + j” is set.

The transfer function calculation unit 33, based on the received signal y [k, q] and the estimated transmission signal x _E [k, q], transmits the transfer function h ₀ [k, q] of the transmission line when transmitting the carrier [k, q]. ] Is calculated. Specifically, for example, according to _{"h 0 [k, q]} = y [k, q] / x E [k, q]", it can be calculated h ₀ [k, q]. Alternatively, h ₀ [k, q] may be calculated according to “h ₀ [k, q] = y [k, q] · x _E ^* [k, q]”. x _E ^* [k, q] is a complex conjugate number of x _E [k, q].

  The noise removing unit 34 removes noise included in the transfer function obtained by the transfer function calculating unit 33. Note that the noise removal executed by the noise removing unit 34 (and a noise removing unit in other embodiments described later) means the removal of all or part of the noise, and the noise removal is paraphrased as noise reduction. You can also.

  Any method including a known method (for example, a method described in Japanese Patent Application Laid-Open No. 2008-118194) can be used as a method for removing noise in the transfer function. FIG. 5 shows an internal block diagram of a noise removing unit 34 a that can be used as the noise removing unit 34.

The noise removing unit 34a includes each part referred to by reference numerals 41 to 44. The noise removing unit 34a removes the transfer function noise for each symbol. Transfer functions h ₀ [k, 1] to h ₀ [k, Q] for one symbol calculated by the transfer function calculation unit 33 are input to the IFFT unit 41. The IFFT unit 41 converts the input transfer functions h ₀ [k, 1] to h ₀ [k, Q] on the frequency domain into transfer functions on the time domain by inverse fast Fourier transform. By this conversion, T transfer functions h ₀ ′ [k, t] arranged in a time series, which are transfer functions in the time domain, are obtained and output from the IFFT unit 41 (T = Q).

The power calculation unit 42 calculates the power of each of the T transfer functions h ₀ ′ [k, t] in the time domain expressed as a complex signal. Of the T transfer functions h ₀ ′ [k, t], the i-th transfer function is represented by h ₀ ′ [k, t _i ], and for the transfer function h ₀ ′ [k, t _i ]. The power calculated in this way is represented by P [k, t _i ] (i is an integer). The comparison extraction unit 43 compares the calculated powers P [k, t ₁ ] to P [k, t _T ] with a predetermined threshold value P _TH (P _TH > 0), and the power becomes larger than the threshold value P _TH. The components are extracted from the output values h ₀ ′ [k, t ₁ ] to h ₀ ′ [k, t _T ] of the IFFT unit 41 and output to the FFT unit 44 as they are. On the other hand, components whose power is equal to or less than the threshold value P _TH are regarded as noise components, and the output value of the IFFT unit 41 is corrected to zero before being output to the FFT unit 44. The output value of the comparison extraction unit 43 corresponding to the output value h ₀ ′ [k, t _i ] of the IFFT unit 41 is represented by h ₀ ″ [k, t _i ]. Then
If “h ₀ ′ [k, t _i ]> P _TH ”, “h ₀ ” [k, t _i ] = h ₀ ′ [k, t _i ] ”is set, and“ h ₀ ′ [k, t _i ] ”is set. ] ≦ P _TH ”,“ h ₀ ”[k, t _i ] = 0”.

Therefore, for example, among the powers P [k, t ₁ ] to P [k, t _T ], the powers P [k, t _A ] and P [k, t _B corresponding to the symbols 311 to 313 in FIG. ] And P [k, t _C ] are larger than the threshold value P _TH , h ₀ ′ [k, t _A ], h ₀ ′ [k, t _B ] and h ₀ output from the IFFT unit 41. '[K, t _C ] remains as h ₀ ″ [k, t _A ], h ₀ ″ [k, t _B ] and h ₀ ″ [k, t _C ] as they are from the comparison extraction unit 43 to the FFT unit 44. (T _A , t _B and t _C are different natural numbers equal to or less than T). On the other hand, of the output values h ₀ ′ [k, t ₁ ] to h ₀ ′ [k, t _T ] of the IFFT unit 41, h ₀ ′ [k, t _A ], h ₀ ′ [k, t _B ] Since zero is substituted for values other than h ₀ ′ [k, t _C ], the output values h ₀ ″ [k, t ₁ ] to h ₀ ″ [k, t _T ] of the comparison and extraction unit 43. Among these, values other than h ₀ ″ [k, t _A ], h ₀ ″ [k, t _B ] and h ₀ ″ [k, t _C ] are zero. FIG. 6B shows the power state of the transfer function in the time domain output from the comparison and extraction unit 43 to the FFT unit 44. The threshold value P _TH can be determined based on the maximum value among the powers P [k, t ₁ ] to P [k, t _T ]. For example, a value obtained by subtracting a positive constant value from the maximum value may be set as the threshold value P _TH .

The FFT unit 44 converts the transfer functions h ₀ ″ [k, t ₁ ] to h ₀ ″ [k, t _T ] on the time domain output from the comparison and extraction unit 43 into the frequency domain using fast Fourier transform. The above transfer functions are converted into h ₁ [k, 1] to h ₁ [k, Q]. The transfer function obtained by the FFT unit 44 is output from the noise removing unit 34a as a transfer function after noise removal.

The delay unit 35 in FIG. 4 delays the transfer function h ₁ [k, q] output from the noise removal unit 34 (or 34a) by a unit time (that is, one symbol) and outputs the result. Therefore, the transfer function h ₁ [k, q] output from the noise removing unit 34 (or 34a) in the current symbol interval is output from the delay unit 35 to the equalizing unit 31 in the next symbol interval, and is received signal y [k + 1]. , Q].

According to the equalization processing unit according to the first embodiment, good equalization is possible even when a known signal is not included in each symbol. Compared to an adaptive equalizer that performs equalization using a transversal filter or the like in the time domain, the required amount of computation is reduced, reducing hardware size, reducing power consumption, and shortening computation time. In addition, high equalization performance can be realized by performing equalization in the frequency domain. Furthermore, in the first embodiment, the received signal (y [k, q]) of the current symbol is equalized using the transfer function (h ₁ [k-1, q]) obtained with the previous symbol. The equalized signal can be output immediately.

  Note that the transfer function information calculated by the equalization processing unit 15a may be provided to the soft decision unit 16 (FIG. 2) (the same applies to other examples described later). Thereby, the code correction capability in the decoding processing unit 17 can also be improved.

<< Second Example >>
A second embodiment will be described. The second embodiment assumes a case where a known signal is inserted into an OFDM signal. FIG. 7 is an internal block diagram of the equalization processing unit 15b according to the second embodiment. In the second embodiment, the equalization processing unit 15b is used as the equalization processing unit 15 in FIG. The equalization processing unit 15b includes each part referred to by reference numerals 31 to 36. The OFDM signal output from the FFT unit 14 is input to the equalization unit 31 and the transfer function calculation unit 33. The configurations and operations of the equalization unit 31, the reference point calculation unit 32, the transfer function calculation unit 33, the noise removal unit 34, and the delay unit 35 provided in the equalization processing unit 15b are basically the same as those in the first embodiment. The same applies to the second embodiment, as long as there is no contradiction. Only the differences from the first embodiment will be described below.

The transfer function calculation unit 33 in the equalization processing unit 15b receives the received signal y [k, q] when the received signal y [k, q] is a known signal (that is, when the transmitted signal x [k, q] is a known signal). Based on the known signal r [k, q] corresponding to the signal y [k, q] and the received signal y [k, q], the transfer function h ₀ [k, q]. Specifically, for example, when the received signal y [k, q] is a received signal of a known signal, “h ₀ [k, q] = y [k, q] / r [k, q]” or , in accordance with the _{"h 0 [k, q]} = y [k, q] · r * [k, q]", it is possible to calculate the h ₀ [k, q]. r ^* [k, q] is the complex conjugate number of r [k, q].

  The operation of the transfer function calculator 33 when the received signal y [k, q] is not a received signal of a known signal (that is, when the transmitted signal x [k, q] is not a known signal) is the same as that of the first embodiment. It is the same.

The switching unit 36 alternatively outputs the known signal r [k, q] or the estimated transmission signal x _E [k, q] from the reference point calculation unit 32 to the transfer function calculation unit 33. Specifically, when the received signal y [k, q] is a received signal of a known signal, the known signal r [k, q] is output to the transfer function calculating unit 33 and the received signal y [k, q] is output. Is not a received signal of a known signal, the estimated transmission signal x _E [k, q] from the reference point calculation unit 32 is output to the transfer function calculation unit 33.

  The values of the in-phase component and the quadrature component of the known signal are given in advance to the equalization processing unit 15b, and the reception signal y [k, q] is received by the equalization processing unit 15b from the values of k and q. An agreement is made in advance between the transmission device 1 and the reception device 2 so that it can be determined whether or not the signal is a signal (the same applies to other embodiments described later).

  The symbol and carrier to which the known signal is assigned are arbitrary. Known signals may be allocated at regular intervals in the time direction and / or the frequency direction, and a scattered pilot signal as a known signal may be included in the OFDM signal as in ISDB-T. Further, as in DAB, a known signal may be assigned to all carriers only to a certain symbol, while no known signal may be assigned to other symbols. In the latter case (DAB), the transfer function of each carrier can be obtained more accurately. The above description of the known signal also applies to other embodiments described below that use the known signal.

  According to the second embodiment, the same effect as that of the first embodiment can be obtained. Furthermore, in the second embodiment, when a known signal is received, the transfer function is calculated using the known signal. Therefore, a more accurate transfer function can be estimated as compared with the case where the known signal is not used. .

<< Third Example >>
A third embodiment will be described. The third embodiment assumes a case where no known signal is inserted in the OFDM signal (however, it may be inserted). FIG. 8 is an internal block diagram of the equalization processing unit 15c according to the third embodiment. In the third embodiment, the equalization processing unit 15c is used as the equalization processing unit 15 in FIG. The equalization processing unit 15c includes each part referred to by reference numerals 61 to 66. The OFDM signal output from the FFT unit 14 is input to the provisional equalization unit 61, the transfer function calculation unit 63, and the main equalization unit 66.

  The provisional equalization unit 61 generates and outputs a provisional equalization signal for each carrier by provisionally equalizing the carrier signal output from the FFT unit 14 using the transfer function output from the delay unit 65. To do. The reference point calculation unit 62 has a function as a transmission signal estimation unit, and estimates and outputs a transmission signal for each carrier based on the provisional equalization signal output from the provisional equalization unit 61. The transfer function calculator 63 calculates and outputs a transfer function for each carrier based on the carrier signal output from the FFT unit 14 and the estimated transmission signal output from the reference point calculator 62. The noise removing unit 64 removes noise included in the transfer function output from the transfer function calculating unit 63 and outputs the transfer function after the noise removal. The delay unit 65 delays the transfer function after noise removal output from the noise removal unit 64 by a unit time (ie, one symbol), and outputs the transfer function having the delay to the provisional equalization unit 61. . The equalization unit 66 generates and outputs an equalized signal for each carrier by equalizing the carrier signal output from the FFT unit 14 using the transfer function output from the noise removing unit 64. The equalization signal generated by the main equalization unit 66 is output to the soft decision unit 16 as a final equalization signal.

  Hereinafter, the process of generating the equalized signal x ′ [k, q] from y [k, q] will be specifically described with attention paid to the received signal y [k, q] for a certain carrier.

In the current symbol interval, the transfer function output from the transfer function calculation unit 63 is represented by h ₀ [k, q], the transfer function output from the noise reduction unit 64 is represented by h ₁ [k, q], The transfer function output from the delay unit 65 is represented by h ₁ [k−1, q]. In previous symbol interval, the received signal y [k-1, q] transmitted by the transfer function calculating unit 63 using the function _{h 0 [k-1, q} ] is determined, transmitted by the noise removal unit 64 functions h ₀ [k The transfer function h ₁ [k-1, q] is obtained by removing the noise of −1, q]. The transfer function h ₁ [k−1, q] is output from the delay unit 65 in the current symbol period. The following description is an explanation of the operation in the current symbol period unless otherwise specified.

The provisional equalization unit 61 equalizes the reception signal y [k, q] using the transfer function h ₁ [k−1, q] output from the delay unit 65 to thereby obtain a provisional equalization signal x ″ [ k, q] are generated and output. For example, x ″ [k, q] can be obtained according to the following formula (C1), (C2), or (C3).
x ″ [k, q] = y [k, q] / h ₁ [k−1, q] (C1)
x ″ [k, q] = y [k, q] · h ₁ ^* [k−1, q] (C2)
x ″ [k, q] = y [k, q] · | h ₁ [k−1, q] | / h ₁ [k−1, q]
... (C3)

Based on the provisional equalization signal x ″ [k, q] from the provisional equalization unit 61, the reference point calculation unit 62 determines the transmission signal x [k, q] corresponding to the reception signal y [k, q]. presume. A signal obtained by estimating the transmission signal x [k, q] in the reference point calculation unit 62 is represented by x _E [k, q]. If the estimate is ideal, x _E [k, q] = x [k, q]. Provisional equalized signal x '' method for calculating a [k, q] in based x _E [k, q] is equalized signal x by the reference point calculator 32 of FIG. 4 '[k, q] in based x _E [ This is the same as the method for calculating k, q].

The transfer function calculation unit 63 is based on the received signal y [k, q] and the estimated transmission signal x _E [k, q] from the reference point calculation unit 62 in the same manner as the transfer function calculation unit 33 in FIG. Then, the transfer function h ₀ [k, q] of the transmission path during the transmission of the carrier [k, q] is calculated.

The noise removing unit 64 removes noise of the transfer function h ₀ [k, q] output from the transfer function calculating unit 63 to generate a transfer function h ₁ [k, q] after noise removal. The method for generating h ₁ [k, q] from h ₀ [k, q] is the same as that in the first embodiment.

The delay unit 65 delays the transfer function h ₁ [k, q] output from the noise removal unit 64 by a unit time (ie, one symbol) and outputs the result. Accordingly, the transfer function h ₁ [k, q] output from the noise removing unit 64 in the current symbol interval is output from the delay unit 65 to the provisional equalizing unit 61 in the next symbol interval and is received signal y [k + 1, q]. It is used for provisional equalization.

The equalization unit 66 equalizes the received signal y [k, q] using the transfer function h ₁ [k, q] output from the noise removal unit 64 to equalize the signal x ′ [k, q ] Is generated and output. For example, the equalization unit 66 can obtain x ′ [k, q] according to the following formula (C4), (C5), or (C6). ^{_{Here, h 1 * [k, q}} ] is the complex conjugate of _{h 1 [k, q],} | h 1 [k, q] | is h _1, which is represented as a complex signal [k, q] of It represents the magnitude (amplitude).
x ′ [k, q] = y [k, q] / h ₁ [k, q] (C4)
x ′ [k, q] = y [k, q] · h ₁ ^* [k, q] (C5)
x ′ [k, q] = y [k, q] · | h ₁ [k, q] | / h ₁ [k, q] (C6)

According to the third embodiment, the same effect as that of the first embodiment can be obtained. Further, in the first or second embodiment, the received signal (y [k, q]) of the current symbol is equalized using the transfer function (h ₁ [k-1, q]) obtained with the previous symbol. On the other hand, in the third embodiment, based on the transfer function (h ₁ [k−1, q]) obtained with the previous symbol, the current symbol is subjected to provisional equalization or the like. A transfer function (h ₁ [k, q]) is obtained, and final equalization is performed thereby. For this reason, it becomes possible to estimate a transfer function more accurately than in the first or second embodiment.

The following transfer function update process may be performed by the equalization processing unit 15c. In the transfer function update process, the transfer function h ₁ [k, q] once calculated by the noise removing unit 64 as described above is exceptionally given to the provisional equalizing unit 61 without passing through the delay unit 65, After using the transfer function h ₁ [k, q] instead of h ₁ [k−1, q], the provisional equalization unit 61, the reference point calculation unit 62, the transfer function calculation unit 63, and the noise removal unit 64 Then, x ″ [k, q], x _E [k, q], h ₀ [k, q] and h ₁ [k, q] are calculated again.

By executing the transfer function update process once, the transfer function h ₁ [k, q] output from the noise removing unit 64 is updated once. Equalization is performed by equalizing the received signal y [k, q] in the equalization unit 66 using the latest transfer function h ₁ [k, q] obtained by executing one transfer function update process. The signal x ′ [k, q] may be generated, or the present equalization unit 66 using the latest transfer function h ₁ [k, q] obtained by repeatedly executing the transfer function update process a plurality of times. The equalized signal x ′ [k, q] may be generated by equalizing the received signal y [k, q]. By using such a transfer function update process, the transfer function can be estimated more accurately.

<< 4th Example >>
A fourth embodiment will be described. The fourth embodiment assumes a case where a known signal is inserted into an OFDM signal. FIG. 9 is an internal block diagram of the equalization processing unit 15d according to the fourth embodiment. In the fourth embodiment, the equalization processing unit 15d is used as the equalization processing unit 15 in FIG. The equalization processing unit 15d includes portions that are referred to by reference numerals 61 to 67. The OFDM signal output from the FFT unit 14 is input to the provisional equalization unit 61, the transfer function calculation unit 63, and the main equalization unit 66. The configuration and operation of the provisional equalization unit 61, the reference point calculation unit 62, the transfer function calculation unit 63, the noise removal unit 64, the delay unit 65, and the main equalization unit 66 provided in the equalization processing unit 15d are basically the same. Similar to those in the third embodiment, the description of the third embodiment is applied to the fourth embodiment as long as there is no contradiction. Only the differences from the third embodiment will be described below.

The transfer function calculation unit 63 in the equalization processing unit 15d receives the received signal y [k, q] when the received signal y [k, q] is a known signal (that is, when the transmitted signal x [k, q] is a known signal). Based on the known signal r [k, q] corresponding to the signal y [k, q] and the received signal y [k, q], the transfer function h is obtained in the same manner as the transfer function calculator 33 of the second embodiment. ₀ [k, q] is calculated. On the other hand, the operation of the transfer function calculation unit 63 when the received signal y [k, q] is not a known signal (that is, when the transmitted signal x [k, q] is not a known signal) is the third embodiment. Same as example.

The switching unit 67 alternatively outputs the known signal r [k, q] or the estimated transmission signal x _E [k, q] from the reference point calculation unit 62 to the transfer function calculation unit 63. Specifically, when the received signal y [k, q] is a received signal of a known signal, the known signal r [k, q] is output to the transfer function calculating unit 63, and the received signal y [k, q] is output. Is not a received signal of a known signal, the estimated transmission signal x _E [k, q] from the reference point calculation unit 62 is output to the transfer function calculation unit 63.

  According to the fourth embodiment, the same effects as those of the first and third embodiments (see FIGS. 4 and 8) can be obtained, and the same effects as those of the second embodiment (see FIG. 7) can be obtained. You can also.

<< 5th Example >>
A fifth embodiment will be described. In the equalization processing unit 15c of FIG. 8, the equalization unit that performs equalization is divided into two, and these two equalization units (the provisional equalization unit 61 and the main equalization unit 66) are integrated into one. In addition, an equalization processing unit equivalent to that of the third embodiment may be formed by switching a transfer function input to one equalization unit. A configuration example of an equalization processing unit to which such integration is applied will be described in a fifth embodiment. The fifth embodiment assumes a case where no known signal is inserted in the OFDM signal (however, it may be inserted).

  FIG. 10 is an internal block diagram of the equalization processing unit 15e according to the fifth embodiment. In the fifth embodiment, the equalization processing unit 15e is used as the equalization processing unit 15 in FIG. The equalization processing unit 15e includes each part referred to by reference numerals 81 to 86. The OFDM signal output from the FFT unit 14 is input to the equalization unit 81 and the transfer function calculation unit 83.

  When the transfer function from the delay unit 85 is input to the equalization unit 81, the equalization unit 81 functions as the provisional equalization unit 61 in FIG. 8 and is output from the delay unit 85 for each carrier. A provisional equalization signal is generated and outputted by provisionally equalizing the carrier signal output from the FFT unit 14 using the transfer function. On the other hand, when the transfer function from the noise removal unit 84 is input to the equalization unit 81 without passing through the delay unit 85, the equalization unit 81 functions as the main equalization unit 66 in FIG. The equalization signal is generated and output by equalizing the carrier signal output from the FFT unit 14 using the transfer function output from the noise removing unit 84. This equalized signal is output to the soft decision unit 16 as a final equalized signal.

  The reference point calculation unit 82 has a function as a transmission signal estimation unit, and estimates and outputs a transmission signal for each carrier based on the provisional equalization signal output from the equalization unit 81. The transfer function calculator 83 calculates and outputs a transfer function for each carrier based on the carrier signal output from the FFT unit 14 and the estimated transmission signal output from the reference point calculator 82. The noise removing unit 84 removes noise included in the transfer function output from the transfer function calculating unit 83 and outputs a transfer function after the noise removal. The delay unit 85 delays the transfer function after noise removal output from the noise removal unit 84 by a unit time (ie, one symbol), and outputs the transfer function having the delay to the switching unit 86. The switching unit 86 alternatively outputs the transfer function output from the noise reduction unit 84 or the transfer function output from the delay unit 85 to the equalization unit 81.

  Hereinafter, the process of generating the equalized signal x ′ [k, q] from y [k, q] will be specifically described with attention paid to the received signal y [k, q] for a certain carrier.

In the current symbol interval, the transfer function output from the transfer function calculation unit 83 is represented by h ₀ [k, q], the transfer function output from the noise reduction unit 84 is represented by h ₁ [k, q], The transfer function output from the delay unit 85 is represented by h ₁ [k−1, q]. In previous symbol interval, the received signal y [k-1, q] is the transfer function _{h 0 [k-1, q} ] by the transfer function calculating unit 83 by using the obtained and transmitted by the noise removal unit 84 functions h ₀ [k The transfer function h ₁ [k-1, q] is obtained by removing the noise of −1, q]. This transfer function h ₁ [k−1, q] is output from the delay unit 85 in the current symbol period. The following description is an explanation of the operation in the current symbol period unless otherwise specified.

  The process of generating the equalized signal x ′ [k, q] from the received signal y [k, q] is roughly divided into a first process and a second process, and the second process is executed after the first process. Thus, x ′ [k, q] is obtained. A control unit that controls the equalization unit 81, the reference point calculation unit 82, the transfer function calculation unit 83, the noise removal unit 84, the delay unit 85, and the switching unit 86 so that the second processing is executed after the first processing ( (Not shown) can be considered to be inherent in the equalization processing unit 15e.

In the first process, the transfer function h ₁ [k−1, q] from the delay unit 85 is given to the equalization unit 81 via the switching unit 86, and the equalization unit 81, the reference point calculation unit 82, and the transfer function calculation. The unit 83 and the noise removal unit 84 perform the same operations as the provisional equalization unit 61, the reference point calculation unit 62, the transfer function calculation unit 63, and the noise removal unit 64 of FIG. 8, respectively, so that x ″ [k, q]. , X _E [k, q], h ₀ [k, q] and h ₁ [k, q] are obtained. That is, in the first process,
Based on the transfer function h ₁ [k−1, q] from the delay unit 85 and the received signal y [k, q] from the FFT unit 14, the equalizing unit 81 is similar to the provisional equalizing unit 61 in FIG. Calculate and output a provisional equalization signal x ″ [k, q],
Based on the provisional equalization signal x ″ [k, q] from the equalization unit 81, the reference point calculation unit 82 calculates the estimated transmission signal x _E [k, q] in the same manner as the reference point calculation unit 62 in FIG. Calculate and output
Based on the received signal y [k, q] and the estimated transmission signal x _E [k, q] from the reference point calculation unit 82, the transfer function calculation unit 83 performs the transfer function h in the same manner as the transfer function calculation unit 63 in FIG. ₀ [k, q] is calculated and output,
The transfer function h ₀ [k, q] of the noise reduction unit 84 from the transfer function calculating unit 83 based on the calculated transfer functions h ₁ after the noise reduction in the same manner as the noise reduction unit 64 of FIG. 8 [k, q] And output.

In the second process, the switching unit 86 receives the transfer function h ₁ [k, q] obtained in the first process directly to the equalization unit 81 without passing through the delay unit 85, so that it is received by the equalization unit 81. The signal y [k, q] is equalized by the transfer function h ₁ [k, q], thereby obtaining the final equalized signal x ′ [k, q]. The method of generating x ′ [k, q] based on y [k, q] and h ₁ [k, q] is the same as that of the main equalization unit 66 in FIG. The final equalized signal x ′ [k, q] generated by the equalizing unit 86 is output to the soft decision unit 16.

  According to the fifth embodiment, the same effect as that of the third embodiment (see FIG. 8) can be obtained. Further, the number of equalization units can be reduced in comparison with the third embodiment.

Note that the transfer function update processing described in the third embodiment may be performed by the equalization processing unit 15e. In the transfer function updating process according to the fifth embodiment, the transfer function h ₁ [k, q] once calculated by the noise removing unit 84 as described above is directly given to the equalizing unit 81, and the transfer function h _{1 is obtained.} After using [k, q] instead of h ₁ [k-1, q] from the delay unit 85, the equalization unit 81, the reference point calculation unit 82, the transfer function calculation unit 83, and the noise removal unit 84 Then, x ″ [k, q], x _E [k, q], h ₀ [k, q] and h ₁ [k, q] are calculated again.

By executing the transfer function update process once, the transfer function h ₁ [k, q] output from the noise removing unit 84 is updated once. The equalization unit 81 performs final equalization of the received signal y [k, q] using the latest transfer function h ₁ [k, q] obtained by executing the transfer function update process once. Thus, the equalized signal x ′ [k, q] may be generated, or the latest transfer function h ₁ [k, q] obtained by repeatedly executing the transfer function update process a plurality of times is used. The equalization unit 81 may perform final equalization of the received signal y [k, q], thereby generating the equalized signal x ′ [k, q]. By using such a transfer function update process, it becomes possible to estimate the transfer function more accurately.

<< Sixth Example >>
A sixth embodiment will be described. In the equalization processing unit 15d of FIG. 9, the equalization unit that performs equalization is divided into two, and these two equalization units (the provisional equalization unit 61 and the main equalization unit 66) are integrated into one. In addition, an equalization processing unit equivalent to that of the fourth embodiment may be formed by switching a transfer function input to one equalization unit. A configuration example of an equalization processing unit to which such integration is applied will be described in a sixth embodiment. The sixth embodiment assumes a case where a known signal is inserted into an OFDM signal.

  FIG. 11 is an internal block diagram of the equalization processing unit 15f according to the sixth embodiment. In the sixth embodiment, the equalization processing unit 15f is used as the equalization processing unit 15 in FIG. The equalization processing unit 15f includes each part referred to by reference numerals 81 to 87. The OFDM signal output from the FFT unit 14 is input to the equalization unit 81 and the transfer function calculation unit 83. The configurations and operations of the equalization unit 81, the reference point calculation unit 82, the transfer function calculation unit 83, the noise removal unit 84, the delay unit 85, and the switching unit 86 provided in the equalization processing unit 15f are basically the fifth embodiment. Similar to those in the example, the description of the fifth embodiment applies to the sixth embodiment as long as there is no contradiction. Only the differences from the fifth embodiment will be described below.

The transfer function calculation unit 83 in the equalization processing unit 15f receives the received signal y [k, q] when the received signal y [k, q] is a known signal (that is, when the transmitted signal x [k, q] is a known signal). Based on the signal y [k, q] and the known signal r [k, q] corresponding to the received signal y [k, q], the same method as the transfer function calculation unit 33 (see FIG. 7) of the second embodiment is used. Thus, the transfer function h ₀ [k, q] is calculated. On the other hand, the operation of the transfer function calculating unit 83 when the received signal y [k, q] is not a known signal (that is, when the transmitted signal x [k, q] is not a known signal) is the fifth embodiment. Same as example.

The switching unit 87 alternatively outputs the known signal r [k, q] or the estimated transmission signal x _E [k, q] from the reference point calculation unit 82 to the transfer function calculation unit 83. Specifically, when the received signal y [k, q] is a received signal of a known signal, the known signal r [k, q] is output to the transfer function calculating unit 83, and the received signal y [k, q] is output. Is not a received signal of a known signal, the estimated transmission signal x _E [k, q] from the reference point calculation unit 82 is output to the transfer function calculation unit 83.

  According to the sixth embodiment, the same effect as that of the fourth embodiment (see FIG. 9) can be obtained. Further, the number of equalization units can be reduced in comparison with the fourth embodiment.

<< Deformation, etc. >>
The specific numerical values shown in the above description are merely examples, and as a matter of course, they can be changed to various numerical values. As modifications or annotations of the above-described embodiment, notes 1 to 5 are described below. The contents described in each comment can be arbitrarily combined as long as there is no contradiction.

[Note 1]
Although the transmission device 1 has exemplified that the modulation by the QPSK method or the DQPSK method is performed on each carrier, the modulation and demodulation methods employed in the transmission device 1 and the reception device 2 are other than the QPSK method or the DQPSK method. There may be.

[Note 2]
In the above description, it is assumed that the OFDM method is adopted as the transmission method between the transmission device 1 and the reception device 2 and an OFDM signal is transmitted from the transmission device 1 to the reception device 2. The signal transmitted to may be other than the OFDM signal.

[Note 3]
The decoding processing unit 17 in FIG. 2 can also decode information data using a decoding method based on a soft decision value (for example, turbo decoding) other than Viterbi decoding. Further, the hard decision decoding may be performed by the decoding processing unit 17 based on the output signal of the equalization processing unit 15 without using the soft decision unit 16.

[Note 4]
The receiving apparatus according to the present invention can be realized by hardware or a combination of hardware and software.

[Note 5]
The receiving device according to the present invention can be mounted on various communication devices (or electronic devices including communication devices). For example, the receiving apparatus according to the present invention can be mounted on a mobile phone or a broadcast receiver (particularly, for example, an in-vehicle broadcast receiver). The transmission path between the transmission device 1 and the reception device 2 may be wired. That is, a signal may be transmitted from the transmission device 1 to the reception device 2 using a wiring (not shown) that connects the transmission device 1 and the reception device 2.

DESCRIPTION OF SYMBOLS 1 Transmission apparatus 2 Reception apparatus 15, 15a-15f Equalization process part 31, 81 Equalization part 32, 62, 82 Reference point calculation part 33, 63, 83 Transfer function calculation part 34, 64, 84 Noise removal part 35, 65 , 85 Delay unit 36, 67, 86, 87 Switching unit 61 Temporary equalization unit 66 This equalization unit

Claims (6)

In an equalization processing apparatus for generating an equalized signal by performing equalization of a received signal received via a transmission path,
A transfer function deriving unit for deriving a transfer function of the transmission path;
A delay unit that delays and outputs an equalization function based on the transfer function;
An equalization unit that generates the equalized signal by equalizing the received signal using the output of the delay unit;
A transmission signal estimation unit that estimates a transmission signal corresponding to the reception signal based on the equalization signal from the equalization unit,
The equalization processing apparatus, wherein the transfer function deriving unit derives the transfer function based on the received signal and an estimated transmission signal by the transmission signal estimating unit. In an equalization processing apparatus for generating an equalized signal by performing equalization of a received signal received via a transmission path,
A transfer function deriving unit for deriving a transfer function of the transmission path;
A first equalization unit that generates the equalized signal by equalizing the received signal using an equalization function based on the transfer function;
A delay unit that delays and outputs the equalization function given to the first equalization unit;
A second equalization unit that tentatively equalizes the received signal based on the output of the delay unit;
A transmission signal estimation unit that estimates a transmission signal corresponding to the reception signal based on the output of the second equalization unit,
The equalization processing apparatus, wherein the transfer function deriving unit derives the transfer function based on the received signal and an estimated transmission signal by the transmission signal estimating unit. In an equalization processing apparatus for generating an equalized signal by performing equalization of a received signal received via a transmission path,
A transfer function deriving unit for deriving a transfer function of the transmission path;
A delay unit that delays and outputs an equalization function based on the transfer function;
An equalization unit for equalizing the received signal using an equalization function before delay by the delay unit or an equalization function after delay;
A transmission signal estimation unit that estimates a transmission signal corresponding to the reception signal based on an equalization result of the equalization unit,
The equalization unit generates the equalized signal by executing the second process after the first process,
In the first process,
The equalization unit generates a provisional equalization signal by provisionally equalizing the received signal using the delayed equalization function, and provides the provisional equalization signal to the transmission signal estimation unit By using the estimated transmission signal generated by the transmission signal estimating unit and the received signal, the transfer function deriving unit derives the transfer function,
In the second process,
The equalization unit equalizes the received signal by giving the equalization function based on the transfer function derived in the first process to the equalization unit without passing through the delay unit, thereby An equalization processing apparatus for generating an equalization signal. The noise reduction part which reduces the noise of the said transfer function output from the said transfer function derivation | leading-out part, and produces | generates the transfer function after noise reduction as the said function for equalization is characterized by the above-mentioned. Item 4. The equalization processing apparatus according to any one of Items 3 to 4. The transfer function derivation unit includes:
When the received signal is a signal obtained by receiving a predetermined known signal, the transfer function is derived based on the received signal and the known signal,
5. In other cases, the equalization processing apparatus according to claim 1, wherein the transfer function is derived based on the received signal and the estimated transmission signal. A receiving apparatus comprising the equalization processing apparatus according to claim 1.

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