JP6567211B2 - Transmission path estimation apparatus and transmission path estimation method - Google Patents

Description

  The present invention relates to a transmission path estimation apparatus and a transmission path estimation method for estimating transmission path characteristics.

  The main factors that cause deterioration in reception quality in wireless communication that uses a high frequency band and performs multilevel modulation transmission or narrow band transmission include phase noise, carrier frequency offset, and the like. In the conventional transmission path estimation method under the unsteady transmission path environment including such factors, the received symbol signal is demodulated using an adaptive equalizer, etc., and the transmission symbol is determined from the demodulated signal. The evaluation weight for the correction error is determined according to the signal point position of the maximum likelihood symbol, and the channel estimation value for demodulation is updated based on the determined weight. In the weighting, a weight value corresponding to a margin for phase rotation is set for each symbol determination region in the signal space diagram. That is, the weight is set to be lighter in the symbol determination region where the margin is small and the symbol erroneous determination is likely to occur due to phase rotation due to phase noise or the like. Thereby, erroneous determination can be reduced. Japanese Patent Application Laid-Open No. 2004-228688 discloses a technique for suitably compensating for phase noise included in a received signal in high-speed communication and reducing insertion of a known pattern that causes overhead into a payload.

Japanese Patent Laying-Open No. 2015-114771

  However, according to the above-described conventional technique, although effective weighting is set for phase noise accompanied by phase rotation, carrier frequency offset, and the like, no consideration is given to thermal noise. When the carrier power-to-noise ratio (CNR) is low, that is, under a transmission line in which thermal noise is dominant, conventional weighting improves phase noise compensation by erroneous symbol determination due to the influence of thermal noise. The effect will fade. For this reason, there is a problem in that the transmission path estimation accuracy is deteriorated and the reception quality may be lowered.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a transmission path estimation apparatus capable of reducing deterioration in reception quality.

In order to solve the above-described problems and achieve the object, the transmission path estimation apparatus of the present invention includes a filter unit that demodulates a received signal using a transmission path estimated value and outputs a demodulated signal, and a demodulated signal. An amplitude calculation unit that calculates an amplitude value normalized by the average received power, a symbol determination unit that determines one or more transmission symbol candidates from the demodulated signal, and one or more transmission symbol candidates that are determined by the symbol determination unit And an error calculation unit for calculating an error between each and the demodulated signal. The channel estimation apparatus uses the amplitude values and erroneous difference, the weighting generator for generating an evaluated weighting coefficients reception reliability of the demodulated signal, weighting coefficients, and updates the step size in relation to the standard channel estimation value A step size generation unit that generates a second update step size based on the first update step size. The transmission path estimation apparatus calculates an error signal based on the reference signal indicating the position of the first candidate symbol point that is the first candidate among the transmission symbol candidates determined by the symbol determination unit and the demodulated signal. A calculation unit; and a transmission path estimation value updating unit that updates the transmission path estimation value based on the received signal, the second update step size, and the error signal . The weighting generation unit generates a first weighting coefficient that evaluates the reception reliability of the demodulated signal using an amplitude value as a weighting coefficient, and uses an error as a weighting coefficient. And a second weight generation unit that generates a second weighting coefficient for evaluating the reception reliability. The step size generation unit generates the second update step size based on the first weighting coefficient, the second weighting coefficient, and the first update step size .

  The transmission path estimation apparatus according to the present invention has an effect that the degradation of reception quality can be reduced.

FIG. 3 is a block diagram showing a configuration example of a receiving apparatus according to the first embodiment; FIG. 3 is a block diagram illustrating a configuration example of a demodulation unit according to the first embodiment. FIG. 3 is a block diagram illustrating a configuration example of a filter unit of the demodulation unit according to the first embodiment. 10 is a flowchart showing an operation of channel estimation by the demodulator of the receiving apparatus according to the first embodiment. The figure which shows the example of the positional relationship with a demodulated signal and a transmission symbol candidate in the operation | movement of the transmission line estimation which the demodulation part concerning Embodiment 1 implements. The figure which shows the example in the case of implement | achieving the processing circuit of the demodulation part concerning Embodiment 1 with the control circuit which has a processor and memory The figure which shows the example in the case of implement | achieving the processing circuit of the demodulation part concerning Embodiment 1 by exclusive hardware. The figure which shows the example of the positional relationship with a demodulation signal and a transmission symbol candidate in the operation | movement of the transmission-line estimation which the demodulation part concerning Embodiment 2 implements. FIG. 4 is a block diagram illustrating a configuration example of a receiving apparatus according to the third embodiment. FIG. 6 is a block diagram illustrating a configuration example of a demodulation unit according to the third embodiment. FIG. 10 is a flowchart illustrating an operation of channel estimation performed by the demodulation unit, the decoding unit, and the transmission replica generation unit of the receiving apparatus according to the third embodiment. FIG. 6 is a block diagram showing a configuration example of a demodulation unit according to the fourth embodiment. The figure which shows the relationship between the demodulation signal memorize | stored in the memory | storage part of the demodulation part concerning Embodiment 4, and an error correction value. 10 is a flowchart showing an operation of channel estimation by the demodulator of the receiving apparatus according to the fourth embodiment. FIG. 6 is a block diagram showing a configuration example of a demodulation unit according to the fifth embodiment. The figure which shows the relationship between the demodulation signal memorize | stored in the memory | storage part of the demodulation part concerning Embodiment 5, a reference signal, and a weighting coefficient. FIG. 10 is a flowchart showing an operation of channel estimation by the demodulation unit, the decoding unit, and the transmission replica generation unit of the receiving apparatus according to the fifth embodiment;

  Hereinafter, a transmission path estimation apparatus and a transmission path estimation method according to an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a block diagram illustrating a configuration example of the receiving device 110 according to the first embodiment of the present invention. The receiving apparatus 110 includes a receiving antenna 100, an RF (Radio Frequency) unit 101, and a baseband unit 102. The RF unit 101 includes a receiving unit 103. The baseband unit 102 includes an ADC (Analog to Digital Converter) 104, a demodulation unit 105, and a decoding unit 106.

  The reception antenna 100 receives a radio frequency signal that is a transmission signal transmitted from a transmission device (not shown).

  The receiving unit 103 performs analog processing on the radio frequency signal received by the receiving antenna 100. Specifically, the receiving unit 103 outputs an analog signal obtained by converting the frequency of the radio frequency signal into a baseband frequency.

  The ADC 104 converts the analog signal output from the receiving unit 103 into a digital signal, and outputs a digital baseband signal that has been subjected to band limiting filter processing for noise removal.

  The demodulator 105 demodulates the digital baseband signal output from the ADC 104 and outputs a demodulated signal.

  Decoding section 106 performs error correction decoding on the demodulated signal output from demodulation section 105 and outputs an error correction decoded signal. The decoding unit 106 performs error correction decoding using an error correction decoding method corresponding to an encoding method implemented by a transmission device (not shown). The encoding method of the transmission apparatus is not limited, and all error correction encoding methods including convolutional code, turbo code, LDPC (Low Density Parity Check) code, Reed-Solomon code, and BCH code are applicable.

  The configuration of the demodulation unit 105 will be described in detail. In the first embodiment, the demodulation unit 105 is a transmission path estimation device. FIG. 2 is a block diagram of a configuration example of the demodulation unit 105 according to the first embodiment. The demodulation unit 105 includes a filter unit 201, an amplitude calculation unit 202, a symbol determination unit 203, an error calculation unit 204, a weight generation unit 205, a step size generation unit 206, an error signal calculation unit 207, a transmission path An estimated value updating unit 208.

  The filter unit 201 has one or more taps, and demodulates the received signal, which is the digital baseband signal output from the ADC 104 in FIG. The filter unit 201 is, for example, an adaptive equalizer or a filter that performs synchronous detection. The filter unit 201 outputs the obtained demodulated signal as an output signal 209 to the decoding unit 106. Further, the filter unit 201 outputs the obtained demodulated signal to the amplitude calculation unit 202, the symbol determination unit 203, the error calculation unit 204, the weight generation unit 205, and the error signal calculation unit 207. In the following description, the input signal 200 may be referred to as a received signal.

  The amplitude calculation unit 202 calculates an amplitude value normalized by the average received power for the demodulated signal from the filter unit 201.

  The symbol determination unit 203 determines one or more transmission symbol candidates from the demodulated signal output from the filter unit 201. The symbol determination unit 203 includes a first symbol determination unit 203-1 to an Mth symbol determination unit 203-M. Detailed operations of the first symbol determination unit 203-1 to the M-th symbol determination unit 203-M will be described later. Note that M is an integer of 2 or more.

  Error calculation section 204 calculates an error amplitude that is an error between the amplitude of each of one or more transmission symbol candidates output from symbol determination section 203 and the amplitude of the demodulated signal from filter section 201. The error calculation unit 204 includes a first error calculation unit 204-1 to an Mth error calculation unit 204-M. Detailed operations of the first error calculation unit 204-1 to the M-th error calculation unit 204-M will be described later. The error amplitude may be simply referred to as an error.

  The weight generation unit 205 generates a weighting coefficient that evaluates the reception reliability of the demodulated signal using at least one of the amplitude value calculated by the amplitude calculation unit 202 or the error amplitude calculated by the error calculation unit 204. To do. The weighting generation unit 205 includes a first weighting generation unit 205-1 and a second weighting generation unit 205-2. Specifically, the first weight generation unit 205-1 is a coefficient that evaluates the reception reliability of the demodulated signal using the calculation result of the amplitude value calculated by the amplitude calculation unit 202, and is a transmission path estimation value. A first weighting coefficient that is a weighting coefficient for updating is generated. The second weighting generation unit 205-2 is a coefficient that evaluates the reception reliability of the demodulated signal using the error amplitude calculation result calculated by the error calculation unit 204 and the demodulated signal from the filter unit 201. Therefore, a second weighting coefficient that is a weighting coefficient for updating the transmission path estimation value is generated.

  The step size generation unit 206 combines the weighting coefficient generated by the weight generation unit 205 and the first update step size, which is the update step size of the transmission channel estimation value that is defined in advance, as a transmission path estimation. A second update step size that is an update step size of the channel estimation value output to the value update unit 208 is generated. The step size generation unit 206 may use only the first weighting coefficient among the weighting coefficients generated by the weighting generation unit 205, may use only the second weighting coefficient, or may use the first weighting coefficient. All of the coefficients and the second weighting coefficient may be used. The step size generation unit 206 uses one or more weighting coefficients among the weighting coefficients generated by the weighting generation unit 205.

  The error signal calculation unit 207 is a transmission symbol candidate output from the symbol determination unit 203, a reference signal indicating the position of the first candidate symbol point that is the first candidate among the transmission symbol candidates, An error signal with respect to the demodulated signal is calculated.

  The channel estimation value update unit 208 is used by the filter unit 201 based on the input signal 200, the second update step size generated by the step size generation unit 206, and the error signal calculated by the error signal calculation unit 207. The estimated transmission path value is updated.

  The configuration of the filter unit 201 of the demodulation unit 105 will be described in detail. FIG. 3 is a block diagram of a configuration example of the filter unit 201 of the demodulation unit 105 according to the first embodiment. The filter unit 201 is configured by an FIR (Finite Impulse Response) filter. Specifically, the filter unit 201 includes shift registers 300-1 to 300-L, complex multipliers 301-0 to 301-L, and an adder 302.

  The shift registers 300-1 to 300-L constitute an L-stage shift register.

  Complex multipliers 301-0 to 301 -L are L + 1 complex multipliers that perform complex multiplication of transmission path estimation values on the outputs from the shift registers 300-1 to 300 -L and the input signal 200 input from the ADC 104. It is a container group. Although not illustrated in FIG. 3, it is assumed that the transmission path estimation value update unit 208 updates the transmission path estimation values used in the complex multipliers 301-0 to 301 -L.

  The adder 302 adds the calculation results obtained by complex multiplication by the complex multipliers 301-0 to 301-L, and outputs the result as an output signal 209, that is, a demodulated signal. Note that L is a natural number of 0 or more. When L = 0, the filter unit 201 includes only one complex multiplier.

  Next, an operation in which the receiving apparatus 110 estimates a transmission path will be described. First, in the reception device 110, when a radio frequency signal is received by the reception antenna 100, the reception unit 103 of the RF unit 101 changes the frequency of the radio frequency signal received by the reception antenna 100 from the radio frequency to the IF frequency or the base frequency. Output analog signal converted to frequency in band. The ADC 104 converts the analog signal output from the receiving unit 103 into a digital signal, and outputs a digital baseband signal subjected to a band limiting filter for noise removal. The demodulator 105 receives symbol data of a digital baseband signal from the ADC 104. The operation so far is an operation performed by a general receiving apparatus, and is not particularly limited as a configuration.

  Next, the operation of estimating the transmission path in the demodulation unit 105 will be described in detail. FIG. 4 is a flowchart illustrating an operation of channel estimation by the demodulation unit 105 of the receiving apparatus 110 according to the first embodiment. The filter unit 201 generates a demodulated signal by a product-sum operation of the transmission path estimation value and the input signal 200 (step S1). In the first case, the filter unit 201 uses the initial value of the transmission path estimation value as the transmission path estimation value. The filter unit 201 outputs the demodulated signal as an output signal 209 to the decoding unit 106. Further, the filter unit 201 outputs the demodulated signal to the amplitude calculation unit 202, the symbol determination unit 203, the error calculation unit 204, the weight generation unit 205, and the error signal calculation unit 207.

  The amplitude calculation unit 202 calculates an amplitude value normalized by the average received power at the coordinates of the demodulated signal for the demodulated signal (step S2). FIG. 5 is a diagram illustrating an example of a positional relationship between a demodulated signal and a transmission symbol candidate in the operation of channel estimation performed by the demodulator 105 according to the first embodiment. FIG. 5 shows the positional relationship on the complex (IQ) plane for the demodulated signal 400 and transmission symbol candidates to be described later. In FIG. 5, the coordinates of the demodulated signal 400 are (x, y), the average received power of the demodulated signal 400 is P, and the amplitude value of the demodulated signal 400 is | p |. The amplitude calculation unit 202 calculates the amplitude value | p | normalized by the average received power P at the coordinates of the demodulated signal 400 according to the equation (1).

  The symbol determination unit 203 determines one or more transmission symbol candidates from the demodulated signal output from the filter unit 201 (step S3). Specifically, the symbol determination unit 203 determines the transmission symbol candidate closest to the demodulated signal 400 as the first candidate according to the coordinate position of the demodulated signal 400 expressed on the IQ plane shown in FIG. Next, the transmission symbol candidate with the next closest distance is determined as the second candidate, and thereafter the same determination is performed, and the transmission symbol candidate with the Mth closest distance is determined as the Mth candidate. The first candidate transmission symbol candidate is the first candidate symbol point, the second candidate transmission symbol candidate is the second candidate symbol point, and the Mth candidate transmission symbol candidate is the Mth candidate symbol point. The symbol determination unit 203 outputs M reference signals to the error calculation unit 204 using information on the position of the transmission symbol candidate, that is, coordinate information, as a reference signal.

  The operation of the symbol determination unit 203 will be specifically described with reference to FIG. FIG. 5 shows an example when M = 3. In the symbol determination unit 203, the first symbol determination unit 203-1 determines the candidate symbol point closest to the coordinate of the demodulated signal 400 as the first candidate symbol point 401 to be the first candidate, and the first candidate symbol The coordinates of the point 401 are output to the error calculation unit 204 as a reference signal. Similarly, the second symbol determination unit 203-2 determines the candidate symbol point that is next closest to the coordinates of the demodulated signal 400 as the second candidate symbol point 402 to be the second candidate, and the second candidate symbol point 402 Are output to the error calculation unit 204 as reference signals. Further, the third symbol determination unit 203-3 determines the candidate symbol point that is next closest to the coordinates of the demodulated signal 400 as the third candidate symbol point 403 to be the third candidate, and the third candidate symbol point 403 The coordinates are output to the error calculation unit 204 as a reference signal.

  In the example illustrated in FIG. 5, the symbol determination unit 203 determines the transmission symbol candidates in order from the shortest distance from the demodulated signal 400, but is not limited thereto. For example, in the case of multilevel modulation transmission (APSK: Amplitude Phase Shift Keying, QAM: Quadrature Amplitude Modulation, etc.), the symbol determination unit 203 uses the transmission symbol candidate with the shortest distance as the first candidate symbol point, and then selects the transmission to be selected next. The symbol candidates may be selected from the transmission symbol candidates having the same amplitude as that of the first candidate symbol point, in order of increasing distance from the demodulated signal 400. This is a selection method that emphasizes noise accompanied by phase rotation because phase noise or carrier frequency offset affects only the phase direction due to phase rotation, not the amplitude direction.

  The error calculation unit 204 calculates an error amplitude between one or more transmission symbol candidates output from the symbol determination unit 203 and the demodulated signal output from the filter unit 201 (step S4). Specifically, error calculation section 204 calculates error amplitude of first candidate symbol point to Mth candidate symbol point for demodulated signal 400 from demodulated signal 400 and reference signals of first candidate symbol point to Mth candidate symbol point. To do. The error calculation unit 204 outputs the calculated M error amplitudes to the weighting generation unit 205.

The operation of the error calculation unit 204 will be specifically described with reference to FIG. FIG. 5 shows an example when M = 3. The coordinates of the demodulated signal 400 are (x, y), the coordinates of the first candidate symbol point 401 are (x ₁ , y ₁ ), the coordinates of the second candidate symbol point 402 are (x ₂ , y ₂ ), and the third candidate symbol. The coordinates of the point 403 are (x ₃ , y ₃ ), and the distance between the coordinates of the demodulated signal 400 and the coordinates of each of the first candidate symbol point 401 to the third candidate symbol point 403, that is, the error amplitude is | e ₁ | ₂ |, | e ₃ | to. The first error calculator 204-1 calculates the error amplitude | e ₁ | between the coordinates of the demodulated signal 400 and the coordinates of the first candidate symbol point 401 according to the equation (2). The second error calculation unit 204-2 calculates the error amplitude | e ₂ | between the coordinates of the demodulated signal 400 and the coordinates of the second candidate symbol point 402 according to the equation (3). Also, the third error calculation unit 204-3 calculates the error amplitude | e ₃ | between the coordinates of the demodulated signal 400 and the coordinates of the third candidate symbol point 403 according to the equation (4).

The weighting generation unit 205 generates a weighting coefficient (step S5). In the weighting generation unit 205, the first weighting generation unit 205-1 calculates a weighting coefficient from the amplitude value | p | of the demodulated signal 400 calculated by the amplitude calculation unit 202. The first weighting generation unit 205-1 sets the weighting coefficient to be larger as the reliability is higher as the amplitude value | p | of the demodulated signal 400 is larger. Also, the first weighting generation unit 205-1 sets the weighting coefficient to be smaller because the reliability is lower as the amplitude value | p | of the demodulated signal 400 is smaller. The method for determining the set value of the weighting coefficient is not particularly limited. For example, when the weighting coefficient to be generated is α ₁ , the first weight generation unit 205-1 can calculate according to the equation (5). Here, a, b, and c are parameters for adjusting the scale of the weighting coefficient.

In the weight generation unit 205, the second weight generation unit 205-2 generates a weighting coefficient from the error amplitude value | e _M | calculated by the error calculation unit 204. M is an integer of 1 or more. The second weight generation unit 205-2 includes the error amplitude value | e ₁ | of the first candidate symbol point and the error amplitude value | e of the second candidate symbol point or more, that is, the second candidate symbol point to the Mth candidate symbol point | e. _{2 A} weighting coefficient is set from the ratio of |||| _M |. The second weighting generation unit 205-2 sets a larger weighting factor on the assumption that the reliability is higher as the error amplitude value | e ₁ | is smaller and the error amplitude value | e ₂ | to | e _M | is larger. The second weighting generator 205-2, error amplitude value | e ₁ | is larger error amplitude value _{| e 2 | ~ | e M} | is higher reliability is smaller setting a small weighting factor as low. The method for determining the set value of the weighting coefficient is not particularly limited. For example, when the weighting coefficient to be generated is α ₂ , the second weight generation unit 205-2 can calculate the weighting coefficient 205-2 according to Expression (6). Here, a _{1 to} a _M , b _{1 to} b _M , β, and γ are parameters for adjusting the scale of the weighting coefficient.

The step size generation unit 206 combines the weighting coefficients α ₁ and α ₂ generated by the weight generation unit 205 to generate an update step size for updating the channel estimation value (step S6). Here, the first update step size that is the update step size of the reference channel estimation value is μ ₀ , and the second update step size that is the update step size for updating the channel estimation value is μ. The step size generation unit 206 calculates the second update step size μ according to the equation (7).

Note that the step size generation unit 206 calculates the second update step size μ by combining the weighting coefficients α ₁ and α _{2 according} to Equation (7), but is not limited to this. For example, the step size generation unit 206 may calculate the second update step size μ by applying only _{one of} the weighting coefficients α ₁ and α ₂ .

  Error signal calculation section 207 calculates an error signal from the reference signal of first candidate symbol point 401 output from first symbol determination section 203-1 and demodulated signal 400 output from filter section 201 (step). S7). Here, the reference signal vector representing the vector of the reference signal of the first candidate symbol point 401 is d, the demodulated signal vector representing the vector of the demodulated signal 400 is r, and the error signal vector representing the error signal vector is e. The error signal calculation unit 207 calculates the error signal vector e according to equation (8).

  Based on the input signal 200, the second update step size μ output from the step size generation unit 206, and the error signal vector e output from the error signal calculation unit 207, the transmission path estimated value update unit 208 The channel estimation value used in 201 is updated (step S8). Here, a case where LMS (Least Mean Squares) is applied as an update algorithm of the transmission path estimation value will be described as an example. If the transmission path estimation value vector is c, the transmission path estimation value update unit 208 updates the transmission path estimation value according to Equation (9). Here, c and r are L × 1 vectors, and * represents a complex conjugate. L is an integer of 1 or more.

  Note that the transmission path estimation value update algorithm is not limited to the LMS algorithm, and any adaptive algorithm such as RLS (Recursive Least Squares) or SMI (Sample Matrix Inversion) can be applied.

  Thereafter, the demodulation unit 105 returns to step S1 and repeatedly performs the operations from step S1 to step S8. In the second and subsequent processes, in step S <b> 1, the filter unit 201 generates a demodulated signal by performing a product-sum operation on the transmission path estimated value updated by the transmission path estimated value updating unit 208 and the input signal 200.

  Next, the hardware configuration of the transmission path estimation apparatus, that is, the demodulation unit 105 will be described. Each component of the demodulator 105 is realized by a processing circuit, for example. In the demodulator 105, a plurality of components may be configured as one processing circuit, or one component may be configured by a plurality of processing circuits.

  Further, even if the processing circuit is dedicated hardware, the CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, A control circuit including a DSP (Digital Signal Processor). Here, the memory is, for example, RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable Read Only Memory), EEPROM (registered trademark) (Electrically Erasable Programmable Read Only Memory), etc. Non-volatile or volatile semiconductor memory, magnetic disk, flexible disk, optical disk, compact disk, mini disk, DVD (Digital Versatile Disk), and the like are applicable.

  When the processing circuit is realized by a control circuit including a CPU, this control circuit is a control circuit having a configuration shown in FIG. 6, for example. FIG. 6 is a diagram illustrating an example in which the processing circuit of the demodulation unit 105 according to the first embodiment is realized by the control circuit 93. As shown in FIG. 6, the control circuit 93 includes a processor 91 that is a CPU and a memory 92. When the processing circuit is realized by the control circuit 93, the processor 91 is realized by reading and executing a program stored in the memory 92 and corresponding to each process of each component. The memory 92 is also used as a temporary memory in each process performed by the processor 91.

  When the processing circuit is realized by dedicated hardware, the processing circuit is, for example, the processing circuit illustrated in FIG. FIG. 7 is a diagram illustrating an example in which the processing circuit of the demodulation unit 105 according to the first embodiment is realized by dedicated hardware. The processing circuit 94 is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof.

  Each component constituting the demodulator 105 may be partially realized by dedicated hardware and partially realized by a control circuit including a CPU.

  As described above, according to the present embodiment, in receiving apparatus 110, demodulation section 105, which is a transmission path estimation apparatus, weights coefficients according to the amplitude value of the demodulated signal coordinates expressed on the IQ plane, Also, the update step size of the channel estimation value is generated by combining a weighting coefficient corresponding to the error amplitude between one or more transmission symbol candidates and the demodulated signal. Demodulation section 105 can improve the channel estimation accuracy by reducing the influence of noise during channel estimation by weighting according to the reliability of each received signal. Thereby, the demodulation part 105 can reduce degradation of reception quality, for example, a bit error rate, in a non-stationary transmission path environment including low CNR and phase noise or carrier frequency offset.

  Since demodulating section 105 can accurately update the transmission path estimation value using the data symbol, a transmitting apparatus that transmits a radio frequency signal to receiving apparatus 110 transmits a known signal to be inserted between data. And multi-level modulation transmission can be performed. Thereby, in the transmission device and the reception device 110, transmission efficiency, that is, throughput can be improved. In addition, since the reception sensitivity can be improved, the communication distance can be extended in communication between the transmission device and the reception device 110.

Embodiment 2. FIG.
In Embodiment 1, amplitude calculation section 202 calculates amplitude value | p | normalized by average received power at the coordinates of demodulated signal 400, and first weight generation section 205-1 performs weighting from amplitude value | p |. The coefficient α ₁ was calculated. In Embodiment 2, the amplitude calculation unit 202 calculates the amplitude value | p ₁ | normalized by the average received power at the coordinates of the first candidate symbol point, and the first weight generation unit 205-1 sets the amplitude value | p. A case where the weighting coefficient α ₁ is calculated from ₁ | will be described.

  In the second embodiment, the configuration of receiving apparatus 110, demodulation section 105, and filter section 201 is the same as that of the first embodiment shown in FIGS. In the second embodiment, the calculation method when the amplitude calculation unit 202 calculates the amplitude value is different from that in the first embodiment.

The amplitude calculation unit 202 calculates an amplitude value normalized by the average received power at the coordinates of the first candidate symbol point that is the first candidate obtained by determining the transmission symbol candidate from the demodulated signal. The operation of the amplitude calculation unit 202 will be specifically described with reference to FIG. FIG. 8 is a diagram illustrating an example of a positional relationship between a demodulated signal and a transmission symbol candidate in the operation of channel estimation performed by the demodulation unit 105 according to the second embodiment. In FIG. 8, the position of the demodulated signal 500, the position of the first candidate symbol point 501 that becomes the first candidate by symbol determination, the position of the second candidate symbol point 502 that becomes the second candidate by symbol determination, and the third candidate by symbol determination The position of the third candidate symbol point 503 is shown. In FIG. 8, the coordinates of the first candidate symbol point 501 with respect to the demodulated signal 500 are (x ₁ , y ₁ ), the average received power of the demodulated signal 500 is P, and the amplitude value of the demodulated signal 500 is | p ₁ |. The amplitude calculation unit 202 calculates the amplitude value normalized by the average received power at the coordinates of the first candidate symbol point 501 with respect to the demodulated signal 500 according to the equation (10).

  In the second embodiment, amplitude calculation section 202 may determine transmission symbol candidates from demodulated signal 500 by itself, or first candidate symbol point 501 from symbol determination section 203, which is not shown in FIG. ~ The coordinate information of the third candidate symbol point 503, that is, the reference signal may be acquired.

In the weighting generator 205, a method of the second weighting generator 205-2 generates a weighting coefficient alpha ₂ is the same as in the first embodiment. In the weighting generation unit 205, the first weighting generation unit 205-1 calculates a weighting coefficient from the amplitude value | p ₁ | of the first candidate symbol point 501 for the demodulated signal 500 calculated by the amplitude calculation unit 202. The first weight generation unit 205-1 sets a larger weighting coefficient on the assumption that the greater the amplitude value | p ₁ | In addition, first weight generation section 205-1 sets the weighting coefficient to be smaller, assuming that the smaller the amplitude value | p ₁ | of first candidate symbol point 501 for demodulated signal 500 is, the lower the reliability is. The method for determining the set value of the weighting coefficient is not particularly limited. First weighting generator 205-1, for example, the weighting factor alpha ₁ can be calculated according to the equation (11). Here, a, b, and c are parameters for adjusting the scale of the weighting coefficient.

As described above, according to the present embodiment, in receiving apparatus 110, demodulation section 105, which is a transmission path estimation apparatus, weights transmission path estimation value updates generated by first weight generation section 205-1. The coefficient α ₁ is calculated from the amplitude value normalized by the average received power at the coordinates of the first candidate symbol point. In this case, since the weighting coefficient α ₁ is constant within the symbol determination region of the received signal, the first to Mth candidate symbol points and the demodulated signal calculated by the second weighting generation unit 205-2. The weighting effect in the vicinity of the boundary between the transmission symbol candidates by the weighting coefficient α ₂ using the error amplitude is emphasized. Demodulation section 105 can improve the transmission path estimation accuracy for multi-level modulation transmission with relatively good CNR and high error occurrence frequency between transmission symbol candidates. Thereby, the demodulation part 105 can reduce degradation of reception quality, for example, a bit error rate, in the unsteady transmission path environment containing a phase noise or a carrier frequency offset.

Embodiment 3 FIG.
In Embodiments 1 and 2, the decoding unit 106 is connected to the subsequent stage of the demodulation unit 105 that is a transmission path estimation apparatus, and the decoding unit 106 performs error correction decoding. In the third embodiment, when the influence of phase noise or frequency offset is so great that a single channel demodulation cannot sufficiently eliminate a channel estimation error due to channel variations, the error correction decoded signal of the decoding unit 106 is fed back to perform demodulation processing. A method of repeating and improving the transmission path estimation accuracy will be described.

  FIG. 9 is a block diagram of a configuration example of the receiving apparatus 110a according to the third embodiment. The receiving device 110a includes a receiving antenna 100, an RF unit 101, and a baseband unit 102a. The baseband unit 102a includes an ADC 104, a demodulation unit 105a, a decoding unit 106, and a transmission replica generation unit 107. In addition, about the structure same as the receiver 110, the same code | symbol is provided and the description is abbreviate | omitted. The same applies to the following description of the configuration.

  The demodulator 105a demodulates the digital baseband signal output from the ADC 104 and outputs a demodulated signal.

  Transmission replica generation section 107 re-encodes and remodulates the error correction decoded signal output from decoding section 106 to generate a transmission replica signal. The transmission replica signal is a replica of the transmission signal when a signal related to the reception signal received by the reception device 110a is transmitted from a transmission device (not shown in FIG. 9). The transmission replica generation unit 107 outputs the generated transmission replica signal to the demodulation unit 105a. Also, the transmission replica generation unit 107 determines whether to apply weighting in the demodulation unit 105a based on the reliability of the transmission replica signal when generating the transmission replica signal, and selects the update step size in the demodulation unit 105a A weight selection signal indicating the method is generated. The transmission replica generation unit 107 sets the selection method of the update step size in the demodulation unit 105a by automatic selection or fixed depending on the reliability of the transmission replica signal. In the case of a fixed setting, the number of demodulations that can sufficiently ensure the accuracy of the transmitted replica signal is set in advance on the receiving apparatus 110a side in accordance with the transmission path assumed in the communication system including the receiving apparatus 110a and the transmitting apparatus not shown in FIG. Keep it. In the case of automatic selection setting, the transmission replica generation unit 107 sets the reliability of the transmission replica signal to the number of error correction errors detected by error correction decoding, error information, and the first candidate symbol point calculated at the time of previous demodulation. It is determined using information that can estimate the channel quality, such as the cumulative value of the error amplitude of the error or the number of error bit measurements using a known sequence. The transmission replica generation unit 107 outputs the generated weight selection signal to the demodulation unit 105a.

  The configuration of the demodulator 105a will be described in detail. In Embodiment 3, demodulation section 105a, decoding section 106, and transmission replica generation section 107 constitute a transmission path estimation apparatus. FIG. 10 is a block diagram of a configuration example of the demodulation unit 105a according to the third embodiment. The demodulation unit 105a includes a filter unit 201, an amplitude calculation unit 202, a symbol determination unit 203, an error calculation unit 204, a weight generation unit 205, a step size generation unit 206a, an error signal calculation unit 207, and a transmission path. An estimated value update unit 208 and a selection unit 210 are provided. Note that the amplitude calculation unit 202 may perform either of the processing in the first and second embodiments.

In addition to the function of the step size generation unit 206, the step size generation unit 206a outputs based on a weight selection signal 212 that instructs selection of whether the weighting coefficients α ₁ and α ₂ are reflected in the step size generation unit 206a. Select the update step size of the channel estimation value. Specifically, the step size generation unit 206a generates the second update step size μ by combining the weighting coefficients α ₁ and α ₂ calculated by the weight generation unit 205 based on the weight selection signal 212, or performs weighting. Whether to output the first update step size μ ₀ as the second update step size μ without reflecting the coefficients α ₁ and α ₂ is selected. That is, the step size generation unit 206a outputs the calculated second update step size or the first update step size μ ₀ to the transmission path estimated value update unit 208 as the second update step size μ.

  The selection unit 210 is a transmission symbol candidate output from the symbol determination unit 203 and is a reference signal of a first candidate symbol point that is a first candidate for a transmission symbol, or a transmission replica signal output from the transmission replica generation unit 107 One of 211 is selected and output to the error signal calculation unit 207.

  The error signal calculation unit 207 calculates an error signal between the signal output from the selection unit 210, that is, the reference signal or transmission replica signal 211, and the demodulated signal from the filter unit 201. The error signal calculation unit 207 may have a different input signal than in the first and second embodiments, but the error signal calculation method is the same as in the first and second embodiments.

  Next, the operation of estimating the transmission path in the demodulator 105a will be described in detail. FIG. 11 is a flowchart illustrating operations of channel estimation performed by the demodulation unit 105a, the decoding unit 106, and the transmission replica generation unit 107 of the receiving apparatus 110a according to the third embodiment. In the third embodiment, the initial transmission path estimation operation without using the transmission replica signal 211 is the same as that in the first embodiment. Therefore, the second and subsequent transmission path estimation operations will be described. The flowchart shown in FIG. 11 shows the second and subsequent transmission path estimation operations by demodulator 105a, decoder 106, and transmission replica generator 107.

  The filter unit 201 generates a demodulated signal by performing a product-sum operation on the transmission path estimated value updated by the transmission path estimated value updating unit 208 and the input signal 200 (step S11). The filter unit 201 outputs the demodulated signal as an output signal 209 to the decoding unit 106. Further, the filter unit 201 outputs the demodulated signal to the amplitude calculation unit 202, the symbol determination unit 203, the error calculation unit 204, the weight generation unit 205, and the error signal calculation unit 207.

  The decoding unit 106 performs error correction decoding on the demodulated signal output from the demodulation unit 105a to generate an error correction decoded signal (step S12). Decoding section 106 outputs the error correction decoded signal to transmission replica generation section 107.

  The transmission replica generation unit 107 generates a transmission replica signal 211 from the error correction decoded signal output from the decoding unit 106 (step S13). Transmission replica generation section 107 performs encoding processing and modulation processing on the error correction decoded signal in the same manner as a transmission device (not shown), and generates transmission replica signal 211 that is a replica of the transmission symbol. The transmission replica generation unit 107 may perform other arithmetic processing such as interleaving or scrambling. The output signal from the decoding unit 106 may be information that can be generated by the transmission replica generation unit 107 in the transmission replica generation unit 107, and may not necessarily be an error correction decoded signal, that is, a decoded bit. For example, the decoding unit 106 may output the soft decision value after error correction or the error-corrected parity bit to the transmission replica generation unit 107.

  The processing from step S14 to step S17 in the amplitude calculation unit 202, symbol determination unit 203, error calculation unit 204, and weight generation unit 205 is the same as the processing from step S2 to step S5 in the first embodiment.

The step size generation unit 206a selects an update step size to be output (step S18). Specifically, the step size generation unit 206a generates and outputs a second update step size μ by combining the weighting coefficients α ₁ and α ₂ based on the weight selection signal 212 generated by the transmission replica generation unit 107. Or whether to output the first update step size μ ₀ as the second update step size μ without reflecting the weighting coefficients α ₁ and α ₂ .

  The selection unit 210 selects the reference signal output from the first symbol determination unit 203-1 or the transmission replica signal 211 output from the transmission replica generation unit 107, and outputs the selected signal to the error signal calculation unit 207 (step S19). ). Specifically, the selection unit 210 selects the reference signal output from the first symbol determination unit 203-1 in the first demodulation process, and the transmission output from the transmission replica generation unit 107 in the second and subsequent demodulation processes. The replica signal 211 is selected. The transmission replica signal 211 from the transmission replica generation unit 107 is generated based on the previous demodulated signal.

  The error signal calculation unit 207 calculates an error signal from the reference signal or transmission replica signal 211 output from the selection unit 210 and the demodulated signal 400 output from the filter unit 201 (step S20).

  Based on the input signal 200, the second update step size μ output from the step size generation unit 206a, and the error signal vector e output from the error signal calculation unit 207, the transmission path estimation value update unit 208 is a filter unit. The channel estimation value used in 201 is updated (step S21).

  Thereafter, the demodulator 105a returns to step S11 and repeats the operations from step S11 to step S21.

  The hardware configurations of the demodulation unit 105a, the decoding unit 106, and the transmission replica generation unit 107 are realized by the processing circuit shown in FIG. 6 or FIG. 7, similarly to the demodulation unit 105 of the first embodiment. In the third embodiment, the demodulation unit 105a, the decoding unit 106, and the transmission replica generation unit 107 may be configured by one processing circuit or a plurality of processing circuits.

  As described above, according to the present embodiment, in reception apparatus 110a, transmission replica generation section 107 generates transmission replica signal 211 based on the error correction decoded signal of decoding section 106 and feeds back to demodulation section 105a. Then, the demodulation unit 105a can improve the transmission path estimation accuracy according to the repetition of the demodulation process by repeatedly performing the demodulation process. The demodulating unit 105a applies the above-described transmission path estimation processing to perform iterative demodulation processing, thereby improving the accuracy of demodulation for each time, thereby reducing the number of times of repeated demodulation processing and reducing the amount of calculation. it can. Demodulating section 105a has a greater effect of improving the transmission path estimation accuracy than in the case of the first and second embodiments in which demodulation processing is performed once. As a result, the demodulation unit 105a can reduce the degradation of reception quality, for example, the bit error rate, in an unsteady transmission path environment including worse phase noise or carrier frequency offset.

Embodiment 4 FIG.
In Embodiments 1 and 2, the demodulation unit 105 generates an error signal and a second update step size μ every time demodulation processing is performed, and the transmission path estimation value update unit 208 together with the input signal 200 performs the second update. The transmission path estimation value is updated using the step size μ and the error signal. In the fourth embodiment, the demodulation unit stores in advance the error correction value obtained from the second update step size μ and the error signal based on the demodulated signal from the filter unit 201, and the demodulated signal output from the filter unit 201 To obtain an error correction value based on the stored contents. A method in which the transmission path estimation value update unit updates the transmission path estimation value using the input signal 200 and the error correction value will be described.

  The configuration of the receiving apparatus in the fourth embodiment is such that demodulating section 105 is replaced with demodulating section 105b with respect to receiving apparatus 110 of the first embodiment shown in FIG. Although illustration is omitted, for convenience of explanation, the receiving apparatus according to the fourth embodiment is referred to as a receiving apparatus 110b.

  The configuration of the demodulation unit 105b will be described in detail. In the fourth embodiment, the demodulation unit 105b is a transmission path estimation device. FIG. 12 is a block diagram of a configuration example of the demodulator 105b according to the fourth embodiment. The demodulating unit 105b includes a filter unit 201, a storage unit 221, a converting unit 222, and a transmission path estimated value updating unit 208b.

  The storage unit 221 stores a correspondence relationship between the demodulated signal output from the filter unit 201 and an error correction value that is an error signal weighted by the second update step size μ. For example, when the demodulated signal “A0” is output from the filter unit 201 in the first and second embodiments, the error signal output from the error signal calculation unit 207 is calculated by the calculation of the symbol determination unit 203 and the error signal calculation unit 207 as an error. The signal is “A1”. Further, when demodulated signal “A0” is output from filter unit 201 in the first and second embodiments, amplitude calculation unit 202, symbol determination unit 203, error calculation unit 204, weight generation unit 205, and step size generation unit 206 The second update step size μ output from the step size generation unit 206 by the above calculation is the second update step size μ “A2”. An error correction value “A3” is obtained by weighting the error signal “A1” with the second update step size μ “A2”. Specifically, the storage unit 221 stores a correspondence relationship between the demodulated signal “A0” and the error correction value “A3”.

As described in the first embodiment, the transmission path estimated value update unit 208 adds the error signal output from the error signal calculation unit 207 to the error signal output from the step size generation unit 206 in the calculation of Expression (9). The error signal is weighted by multiplying the update step size μ by 2. In the storage unit 221, in order to omit the calculation process of the transmission path estimated value update unit 208 b, an error signal is stored in advance as an error correction value by weighting the error signal with the second update step size μ. The error correction value is the same as that of the calculation processing of the amplitude calculation unit 202, the symbol determination unit 203, the error calculation unit 204, and the weight generation unit 205 that does not directly output a signal or the like to the transmission path estimation value update unit 208 in the first embodiment. It is reflected. That is, it can be said that at least one weighting coefficient based on the reception reliability such as the amplitude value calculated by the amplitude calculation unit 202 or the error amplitude calculated by the error calculation unit 204 is used as the error correction value. In addition, it can be said that the first update step size μ ₀ necessary for obtaining the second update step size μ is also used for the error correction value. As a method of storing the error correction value in the storage unit 221, there is a method in which the user obtains an error correction value corresponding to the demodulated signal by simulation or the like and stores it in the storage unit 221 in advance. Is not to be done.

  The conversion unit 222 refers to the storage unit 221 based on the demodulated signal output from the filter unit 201, generates an error correction value corresponding to the demodulated signal, and outputs the error correction value to the transmission path estimated value update unit 208b.

  FIG. 13 is a diagram illustrating a relationship between the demodulated signal and the error correction value stored in the storage unit 221 of the demodulation unit 105b according to the fourth embodiment. For example, when the demodulated signal “A0” is output from the filter unit 201, the conversion unit 222 refers to the storage unit 221 to generate an error correction value “A3” corresponding to the demodulated signal “A0”, and transmits the transmission path. It outputs to the estimated value update part 208b. The storage unit 221 can store the relationship between the demodulated signal and the error correction value in a table format as shown in FIG.

  The channel estimation value update unit 208 b updates the channel estimation value used in the filter unit 201 based on the input signal 200 and the error correction value generated by the conversion unit 222.

  In the fourth embodiment, when an effect by the same processing as in the first and second embodiments is obtained, an amplitude calculating unit 202, a symbol determining unit 203, an error calculating unit 204, a weighting generating unit 205, a step size generating unit 206, and By replacing the processing by the error signal calculation unit 207 with the conversion process of the conversion unit 222 using the storage unit 221, the calculation process of the demodulation unit 105b is omitted.

  Next, the operation of estimating the transmission path in the demodulation unit 105b will be described in detail. FIG. 14 is a flowchart of a transmission path estimation operation performed by the demodulation unit 105b of the receiving apparatus 110b according to the fourth embodiment. The filter unit 201 generates a demodulated signal by the product-sum operation of the transmission path estimation value and the input signal 200 (step S31). In the first case, the filter unit 201 uses the initial value of the transmission path estimation value as the transmission path estimation value. The filter unit 201 outputs the demodulated signal as an output signal 209 to the decoding unit 106. Further, the filter unit 201 outputs the demodulated signal to the conversion unit 222.

  The conversion unit 222 refers to the storage unit 221 based on the demodulated signal output from the filter unit 201, and generates an error correction value corresponding to the demodulated signal (step S32). The conversion unit 222 outputs the generated error correction value to the transmission path estimated value update unit 208b.

The transmission path estimation value update unit 208b updates the transmission path estimation value used in the filter unit 201 based on the input signal 200 and the error correction value output from the conversion unit 222 (step S33). Here, a case where LMS is applied as an update algorithm of the transmission path estimation value will be described as an example. The channel estimation value vector c, r a demodulated signal vector representing the vector of the demodulated signal 400, the error correction value vector representing a vector of error correction value and e _c. The transmission path estimated value update unit 208b updates the transmission path estimated value according to Expression (12). Here, c and r are L × 1 vectors, and * represents a complex conjugate. L is an integer of 1 or more.

  Thereafter, the demodulator 105b returns to step S31 and repeats the operations from step S31 to step S33. In the second and subsequent processes, in step S31, the filter unit 201 generates a demodulated signal by performing a product-sum operation on the transmission path estimation value updated by the transmission path estimation value update unit 208b and the input signal 200.

  Note that the hardware configuration of the demodulator 105b is realized by the processing circuit shown in FIG. 6 or FIG. 7, as in the demodulator 105 of the first embodiment.

  As described above, according to the present embodiment, in receiving apparatus 110b, conversion unit 222 of demodulation unit 105b refers to storage unit 221 on the basis of the demodulated signal from filter unit 201, and determines the channel estimation value. An error signal weighted by the update step size is generated and output to the transmission path estimated value update unit 208b. Since the demodulating unit 105b has a configuration in which arithmetic processing is omitted, the amount of calculation in each component can be reduced as compared with the demodulating unit 105 of Embodiment 1, and high-speed processing is possible. As a result, the demodulating unit 105b reduces the power consumption accompanying the reduction in the amount of calculation, and shortens the delay due to the loop processing for updating the transmission path estimation value, thereby improving the follow-up performance of the transmission path estimation during high-speed mobile communication. Can be made. As a result, the demodulator 105b can reduce degradation of reception quality, for example, bit error rate, under an unsteady transmission path environment including phase noise or carrier frequency offset.

Embodiment 5 FIG.
In the third embodiment, the demodulation unit 105a generates the reference signal and the weighting coefficient every time the demodulation process is performed. In the fifth embodiment, the demodulation unit stores in advance a reference signal and a weighting coefficient based on the demodulated signal from the filter unit 201, and based on the stored content from the demodulated signal output from the filter unit 201, To get. A method in which the transmission path estimation value update unit updates the transmission path estimation value using the input signal 200, the reference signal, and the second update step size μ will be described.

  The configuration of the receiving apparatus in the fifth embodiment is obtained by replacing demodulating section 105a with demodulating section 105c with respect to receiving apparatus 110a in the third embodiment shown in FIG. Although illustration is omitted, for convenience of explanation, the receiving device of the fifth embodiment is referred to as a receiving device 110c.

  The configuration of the demodulator 105c will be described in detail. In Embodiment 5, demodulation section 105c, decoding section 106, and transmission replica generation section 107 constitute a transmission path estimation apparatus. FIG. 15 is a block diagram of a configuration example of the demodulator 105c according to the fifth embodiment. The demodulation unit 105c includes a filter unit 201, a storage unit 231, a conversion unit 232, a step size generation unit 206a, an error signal calculation unit 207, a transmission path estimation value update unit 208, and a selection unit 210. .

  The storage unit 231 stores a correspondence relationship between the demodulated signal output from the filter unit 201, the reference signal of the first candidate symbol point, and the weighting coefficient. The reference signal for the first candidate symbol point is the same as the reference signal output from first symbol determination section 203-1 in the third embodiment. The weighting coefficient is the same as the weighting coefficient output from the weight generation unit 205 in the third embodiment. For example, for the demodulated signal “A0” output from the filter unit 201 in the third embodiment, the reference signal output from the first symbol determination unit 203-1 by the determination of the first symbol determination unit 203-1 Is the reference signal “A4”, and the weighting coefficient output from the weighting generation unit 205 by the operations of the amplitude calculation unit 202, symbol determination unit 203, error calculation unit 204, and weighting generation unit 205 is the weighting coefficient “A5”. Specifically, the storage unit 231 stores a correspondence relationship between the demodulated signal “A0”, the reference signal “A4”, and the weighting coefficient “A5”. As a method for storing the reference signal and the weighting coefficient in the storage unit 231, there is a method in which the user obtains the reference signal and the weighting coefficient corresponding to the demodulated signal by simulation or the like and stores them in the storage unit 231 in advance. However, the present invention is not limited to this.

  The conversion unit 232 refers to the storage unit 231 based on the demodulated signal output from the filter unit 201, generates a reference signal and a weighting coefficient corresponding to the demodulated signal, outputs the reference signal to the selection unit 210, and outputs the weighting coefficient Is output to the step size generation unit 206a.

  FIG. 16 is a diagram illustrating a relationship between a demodulated signal, a reference signal, and a weighting coefficient stored in the storage unit 231 of the demodulation unit 105c according to the fifth embodiment. For example, when the demodulated signal “A0” is output from the filter unit 201, the conversion unit 232 refers to the storage unit 231, and obtains the reference signal “A4” and the weighting coefficient “A5” corresponding to the demodulated signal “A0”. The reference signal “A4” is generated and output to the selection unit 210, and the weighting coefficient “A5” is output to the step size generation unit 206a. The storage unit 231 can store the relationship between the demodulated signal, the reference signal, and the weighting coefficient in a table format as shown in FIG. Here, although there is one weighting coefficient such as “A5” for one demodulated signal, there may be a plurality of weighting coefficients as described above.

  In the fifth embodiment, when the effect by the same processing as in the third embodiment is obtained, the processing by the amplitude calculation unit 202, the symbol determination unit 203, the error calculation unit 204, and the weight generation unit 205 is performed using the storage unit 231. By replacing with the conversion process of the conversion unit 232, the calculation process of the demodulation unit 105c is omitted.

  Next, the operation of estimating the transmission path in the demodulation unit 105c will be described in detail. FIG. 17 is a flowchart illustrating operations of channel estimation performed by the demodulation unit 105c, the decoding unit 106, and the transmission replica generation unit 107 of the receiving apparatus 110c according to the fifth embodiment. The filter unit 201 generates a demodulated signal by the product-sum operation of the transmission path estimation value and the input signal 200 (step S41). The filter unit 201 uses the initial value of the transmission channel estimation value for the first time as the transmission channel estimation value, and uses the transmission channel estimation value updated by the transmission channel estimation value update unit 208 for the second and subsequent times. The filter unit 201 outputs the demodulated signal as an output signal 209 to the decoding unit 106. Further, the filter unit 201 outputs the demodulated signal to the conversion unit 232 and the error signal calculation unit 207.

  The processing in step S42 and step S43 in decoding section 106 and transmission replica generation section 107 is the same as the processing in step S12 and step S13 in the third embodiment.

  The conversion unit 232 refers to the storage unit 231 based on the demodulated signal output from the filter unit 201, and generates a reference signal and a weighting coefficient corresponding to the demodulated signal (step S44). The conversion unit 232 outputs the generated reference signal to the selection unit 210, and outputs the generated weighting coefficient to the step size generation unit 206a.

  The processing from step S45 to step S48 in step size generation section 206a, selection section 210, error signal calculation section 207, and transmission path estimation value update section 208 is the same as the processing from step S18 to step S21 in the third embodiment. .

  Thereafter, the demodulation unit 105c returns to step S41 and repeatedly performs the operations from step S41 to step S48.

  The hardware configurations of the demodulation unit 105c, the decoding unit 106, and the transmission replica generation unit 107 are realized by the processing circuit shown in FIG. 6 or FIG. 7, similarly to the demodulation unit 105 of the first embodiment. In the fifth embodiment, the demodulation unit 105c, the decoding unit 106, and the transmission replica generation unit 107 may be configured by one processing circuit or a plurality of processing circuits.

  As described above, according to the present embodiment, in receiving apparatus 110c, conversion unit 232 of demodulation unit 105c refers to storage unit 231 based on the demodulated signal from filter unit 201 and generates a reference signal. The weighting coefficient is generated and output to the step size generating unit 206a. Since the demodulator 105c has a configuration in which arithmetic processing is omitted, the amount of calculation in each configuration can be reduced compared to the demodulator 105a of Embodiment 3, and high-speed processing is possible. As a result, the demodulator 105c reduces the power consumption accompanying the reduction in the amount of computation, and shortens the delay due to the loop processing for updating the transmission path estimation value, thereby improving the follow-up performance of the transmission path estimation during high-speed communication. be able to. As a result, the demodulator 105c can reduce degradation of reception quality, for example, bit error rate, in an unsteady transmission path environment including phase noise or carrier frequency offset.

  The configuration described in the above embodiment shows an example of the contents of the present invention, and can be combined with another known technique, and can be combined with other configurations without departing from the gist of the present invention. It is also possible to omit or change the part.

  100 receiving antenna, 101 RF unit, 102, 102a baseband unit, 103 receiving unit, 104 ADC, 105, 105a, 105b, 105c demodulating unit, 106 decoding unit, 107 transmitting replica generating unit, 110, 110a receiving device, 201 filter , 202 amplitude calculation unit, 203, 203-1 to 203-M first symbol determination unit to Mth symbol determination unit, 204, 204-1 to 204-M first error calculation unit to Mth error Calculation unit, 205 Weight generation unit, 205-1 First weight generation unit, 205-2 Second weight generation unit, 206, 206a Step size generation unit, 207 Error signal calculation unit, 208, 208b Transmission path estimated value update Unit, 210 selection unit, 221, 231 storage unit, 222, 232 conversion unit, 300-1 to 30 -L shift register, 301-0~301-L complex multipliers, 302 an adder.

Claims (12)

A filter unit that demodulates the received signal using the channel estimation value and outputs a demodulated signal;
Based on the demodulated signal, an amplitude calculation unit that calculates an amplitude value normalized by average received power;
A symbol determination unit for determining one or more transmission symbol candidates from the demodulated signal;
An error calculation unit that calculates an error between each of the one or more transmission symbol candidates determined by the symbol determination unit and the demodulated signal;
Using the amplitude value and the erroneous difference, the weighting generator for generating an evaluated weighting coefficients reception reliability of the demodulated signal,
A step size generating unit that generates a second update step size based on the weighting coefficient and a first update step size that is an update step size of the transmission path estimated value that is a reference;
An error signal calculation unit that calculates an error signal based on a reference signal indicating a position of a first candidate symbol point that is a first candidate among transmission symbol candidates determined by the symbol determination unit, and the demodulated signal;
A channel estimation value updating unit that updates the channel estimation value based on the received signal, the second update step size, and the error signal;
Equipped with a,
The weight generation unit
A first weighting generation unit that generates a first weighting coefficient that evaluates reception reliability of the demodulated signal using the amplitude value as the weighting coefficient;
A second weighting generation unit that generates a second weighting coefficient obtained by evaluating the reception reliability of the demodulated signal using the error as the weighting coefficient;
With
The step size generation unit generates the second update step size based on the first weighting factor, the second weighting factor, and the first update step size.
A transmission path estimation apparatus. The symbol determination unit sets the transmission symbol candidate closest to the demodulated signal as the first candidate symbol point, and the second and subsequent candidates as transmission symbol candidates in the order of distance from the demodulated signal.
The transmission path estimation apparatus according to claim 1 . The symbol determination unit sets a transmission symbol candidate closest to the demodulated signal as the first candidate symbol point, and after the second candidate, the demodulated signal is selected from among transmission symbol candidates having the same amplitude as the first candidate symbol point. As a candidate for transmission symbols in the order of close distance to
The transmission path estimation apparatus according to claim 1 . The amplitude calculator calculates an amplitude value obtained by normalizing the demodulated signal with an average received power.
The transmission path estimation apparatus according to any one of claims 1 to 3 . The amplitude calculation unit calculates an amplitude value obtained by normalizing a first candidate symbol point, which is a first candidate obtained by determining a transmission symbol candidate from the demodulated signal, with average received power;
The transmission path estimation apparatus according to any one of claims 1 to 3 . A decoding unit that performs error correction decoding on the demodulated signal and outputs an error correction decoded signal;
A transmission replica generation unit that generates a transmission replica signal that is a replica of the transmission signal when the signal related to the reception signal is transmitted from the transmission side from the error correction decoded signal;
A selection unit that outputs either the reference signal or the transmission replica signal to the error signal calculation unit;
With
The error signal calculation unit calculates an error signal based on the signal selected from the selection unit and the demodulated signal,
The step size generation unit outputs the second update step size or the first update step size as the second update step size.
The transmission path estimation apparatus according to any one of claims 1 to 5 , wherein: A filter unit that demodulates the received signal using the channel estimation value and outputs a demodulated signal;
An amplitude calculating step for calculating an amplitude value normalized by an average received power based on the demodulated signal;
A symbol determination step in which a symbol determination unit determines one or more transmission symbol candidates from the demodulated signal;
An error calculating unit that calculates an error between each of the one or more transmission symbol candidates determined in the symbol determining step and the demodulated signal;
Weighting generation portion, by using the amplitude value and the erroneous difference, the weighting factor generating step of generating an evaluation and weighting coefficients reception reliability of the demodulated signal,
A step size generating unit that generates a second update step size based on the weighting coefficient and a first update step size that is an update step size of the reference channel estimation value;
The error signal calculating unit calculates an error signal based on the reference signal indicating the position of the first candidate symbol point that is the first candidate among the transmission symbol candidates determined in the symbol determining step, and the demodulated signal A signal calculating step;
A transmission path estimation value updating unit that updates the transmission path estimation value based on the received signal, the second update step size, and the error signal;
Only including,
The weighting coefficient generation step includes:
A first weighting coefficient generating step in which the weighting generation section generates a first weighting coefficient that evaluates reception reliability of the demodulated signal using the amplitude value as the weighting coefficient;
A second weighting coefficient generating step in which the weighting generation section generates a second weighting coefficient that evaluates reception reliability of the demodulated signal using the error as the weighting coefficient;
Including
In the step size generation step, the step size generation unit generates the second update step size based on the first weighting factor, the second weighting factor, and the first update step size. ,
A transmission path estimation method characterized by the above. In the symbol determination step, the symbol determination unit sets a transmission symbol candidate that is closest to the demodulated signal as the first candidate symbol point, and after the second candidate, transmission symbol candidates are determined in order of distance from the demodulated signal. To
The transmission path estimation method according to claim 7 . In the symbol determination step, the symbol determination unit sets a transmission symbol candidate closest to the demodulated signal as the first candidate symbol point, and the second and subsequent candidates transmit symbol candidates having the same amplitude as the first candidate symbol point. From among the candidates for transmission symbols in order of increasing distance from the demodulated signal,
The transmission path estimation method according to claim 7 . In the amplitude calculation step, the amplitude calculation unit calculates an amplitude value obtained by normalizing the demodulated signal with an average received power.
The transmission path estimation method according to any one of claims 7 to 9 . In the amplitude calculation step, the amplitude calculation unit calculates an amplitude value obtained by normalizing a first candidate symbol point, which is a first candidate obtained by determining a transmission symbol candidate from the demodulated signal, with an average received power.
The transmission path estimation method according to any one of claims 7 to 9 . A decoding unit that performs error correction decoding on the demodulated signal and outputs an error correction decoded signal;
A transmission replica generation unit that generates a transmission replica signal that is a replica of the transmission signal when the signal related to the reception signal is transmitted from the transmission side from the error correction decoded signal;
A selection step in which the selection unit outputs either the reference signal or the transmission replica signal to the error signal calculation unit;
Including
In the error signal calculation step, the error signal calculation unit calculates an error signal based on the signal selected in the selection step and the demodulated signal,
In the step size generation step, the step size generation unit outputs the second update step size or the first update step size as the second update step size.
The transmission path estimation method according to any one of claims 7 to 11 , wherein:

Images