WO2014141338A1 - Signal-receiving device, radio communication system, distortion compensation method, and non-temporary computer-readable medium - Google Patents

Abstract

A signal-receiving device for receiving a signal from a signal-transmitting device is provide d with a distortion reduction unit, a compensation coefficient calculation unit, and a distortion compensation unit. The distortion reduction unit generates, from a received signal including a first distortion and a second distortion, a distortion-reduced signal in which the second distortion is reduced and the first distortion is left intact. The compensation coefficient calculation unit calculates, on the basis of the distortion-reduced signal, a compensation co efficient for compensating for the first distortion of the received signal. The distortion compensation unit generates, using the compensation coefficient, a compensated signal in which the first distortion of the received signal is compensated for.

Description

Signal receiving apparatus, wireless communication system, distortion compensation method, and non-transitory computer-readable medium

The present invention relates to a signal receiving device, a wireless communication system, and a distortion compensation method.

In wireless communication, when a signal is output from the transmission side to the reception side, the signal may be distorted. In this case, it is necessary to remove this distortion on the receiving side in order to reproduce a correct signal.

Patent Documents 1 and 2 disclose a demodulator that eliminates nonlinear distortion caused by an amplifier.

11 and 12 show an embodiment of a wireless communication apparatus according to related technology to which the technologies of Patent Documents 1 and 2 are applied. A wireless communication system includes a transmitter 100 (illustrated in FIG. 11) that transmits a radio signal and a receiver 200 (illustrated in FIG. 12) that receives a radio signal from the transmitter 100.

The modulation unit 101 in the transmitter 100 outputs a transmission signal transmitted to the receiver 200. This transmission signal is output from the antenna 103 via the nonlinear device 102 such as an amplifier. Here, the transmission signal is output in a state where nonlinear distortion occurs by the nonlinear device 102.

In the receiver 200, a signal received by the antenna 201 is input. The reception linearizer 202 performs nonlinear distortion compensation on the signal received by the antenna 201 using the nonlinear distortion compensation coefficient input from the compensation coefficient control unit 212.

Then, the reception signal output from the reception linearizer 202 is input to an FIR (Finite Impulse Response) filter 203 for removing the out-of-band interference wave, thereby removing the out-of-band interference wave in the reception signal. Further, intersymbol interference is compensated for by the transversal type automatic equalizer 204 for the received signal. The automatic equalizer 204 compensates for intersymbol interference using the intersymbol interference compensation coefficient generated by the compensation coefficient generation unit 208. The receiver 200 performs intersymbol interference by the transversal type automatic equalizer 204, and then demodulates and outputs the received signal by the demodulator 205.

Also, the output signal of the automatic equalizer 204 is input to the error detection unit 206. The error detection unit 206 detects an error component of the output signal.

The intersymbol interference amount calculation unit 207 calculates the intersymbol interference amount in the received signal based on the error information of the received signal detected by the error detection unit 206. The compensation coefficient generation unit 208 generates an intersymbol interference compensation coefficient used by the automatic equalizer 204 using the intersymbol interference amount calculated by the error detection unit 206.

The non-linear distortion amount calculation unit 210 calculates a correction amount for the non-linear distortion compensation coefficient used in the reception linearizer 202 based on the error information of the received signal detected by the error detection unit 206. In other words, the non-linear distortion amount calculation unit 210 estimates the non-linear distortion amount generated by the non-linear device (here, the non-linear device 102 in the transmitter 100) from the received signal in the receiver 200, and corrects to compensate for the non-linear distortion. Calculate the amount. Further, the non-linear distortion amount calculation unit 210 reads a compensation coefficient corresponding to the power of the reception signal calculated by the power calculation unit 209 from the compensation coefficient recording unit 211. The non-linear distortion amount calculation unit 210 overwrites the previously recorded compensation coefficient as a new non-linear distortion compensation coefficient, and records it in the compensation coefficient recording unit 211 as a new non-linear distortion compensation coefficient. To do.

The power calculation unit 213 calculates the power of the signal received by the antenna 201. The compensation coefficient control unit 212 reads the nonlinear distortion compensation coefficient recorded in the compensation coefficient recording unit 211 according to the power of the signal calculated by the power calculation unit 213, and outputs it to the reception linearizer 202. As described above, the reception linearizer 202 performs nonlinear distortion compensation on the signal received by the antenna 201 using the nonlinear distortion compensation coefficient.

Japanese Patent No. 3541890 Japanese Patent No. 4019912

In the receiver configured as the receiver 200 illustrated in FIG. 12, when coherent fading, adjacent interference signals, and the like exist in the communication path, the power of the interference signal is included in the power input to the power calculation unit 213. Will be added. Therefore, the power value of the input signal to the nonlinear device 102 in the transmitter 100 is not proportional to the power value of the received signal of the receiver 200. Therefore, an appropriate compensation coefficient cannot be selected by the compensation coefficient control unit 212, and there is a problem that communication characteristics deteriorate due to inaccurate nonlinear distortion compensation (false compensation) performed by the reception linearizer 202.

In order to solve this problem, in the receiver 200 of FIG. 12, it is conceivable to change the front-rear relationship between the reception linearizer 202 and the FIR filter 203 (that is, the reception linearizer 202 is disposed at the subsequent stage of the FIR filter 203). However, if this is done, the nonlinear distortion compensation coefficient cannot be calculated accurately. The same problem occurs even when the front-rear relationship between the reception linearizer 202 and the automatic equalizer 204 is changed.

The present invention has been made to solve such problems, and an object of the present invention is to provide a signal receiving apparatus, a wireless communication system, and a distortion compensation method that accurately compensate for signal distortion.

The first aspect of the present invention includes a signal receiving device that receives a signal from a signal transmitting device. The signal receiving apparatus includes a distortion reducing unit, a compensation coefficient calculating unit, and a distortion compensating unit. The distortion reduction unit generates a distortion reduction signal in which the second distortion is reduced while leaving the first distortion among the reception signals including the first distortion and the second distortion. The compensation coefficient calculation unit calculates a compensation coefficient for compensating for the first distortion of the received signal based on the distortion reduction signal. The distortion compensator generates a compensation signal that compensates for the first distortion of the received signal using the compensation coefficient.

A second aspect of the present invention includes a distortion compensation method for a signal receiving apparatus. This distortion compensation method causes the converter to execute the following steps (a) and (b).
(A) calculating a compensation coefficient for compensating the first distortion with respect to the reception signal in which the second distortion is reduced, based on the reception signal including the first distortion and the second distortion; And (b) generating a compensation signal that compensates for the first distortion of the received signal using the compensation coefficient.

According to the present invention, it is possible to provide a signal receiving apparatus, a wireless communication system, and a distortion compensation method that accurately compensate for signal distortion.

1 is a block diagram illustrating an example of a configuration of a signal reception device according to a first exemplary embodiment; 3 is a flowchart showing an example of processing of the signal receiving apparatus according to the first exemplary embodiment; FIG. 6 is a block diagram illustrating an example of a configuration of a transmitter according to a second embodiment. FIG. 5 is a block diagram illustrating an example of a configuration of a receiver according to a second exemplary embodiment. 6 is a graph showing general nonlinear distortion characteristics generated in the nonlinear device according to the second embodiment. FIG. 6 is a block diagram illustrating an example of a configuration of a nonlinear distortion amount calculation unit according to a second embodiment. FIG. 6 is a diagram illustrating an example of an error signal vector of a reception signal according to the second exemplary embodiment. 6 is a graph showing an example of a spectrum of an input signal of a nonlinear device in a transmitter according to a second embodiment; 6 is a graph showing an example of a spectrum of a received signal in the receiver 30 according to the second exemplary embodiment. FIG. 6 is a block diagram illustrating an example of a configuration of a receiver according to a third exemplary embodiment. It is a block diagram which shows the structure of the transmitter concerning related technology. It is a block diagram which shows the structure of the receiver concerning related technology.

Embodiment 1
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an example of the signal receiving apparatus according to the first embodiment. The signal receiving device 1 receives a signal from a signal transmitting device (not shown). The signal receiving device 1 and the signal transmitting device constitute a wireless communication system. The signal reception device 1 includes a distortion reduction unit 2, a compensation coefficient calculation unit 3, and a distortion compensation unit 4.

The received signal including the first distortion and the second distortion is input to the distortion reducing unit 2. The distortion reduction unit 2 generates a distortion reduction signal in which the first distortion is left in the received signal and the second distortion is reduced.

Here, the first distortion and the second distortion are different types of distortion. For example, the first distortion may be a non-linear distortion caused by a non-linear device, and the second distortion may be a distortion generated in a communication path between the signal transmission device and the signal reception device. When the second distortion is distortion generated in the communication path between the signal transmission apparatus and the signal reception apparatus, the second distortion may be, for example, a component of an out-of-band interference wave mixed in the communication path. Alternatively, the second distortion may be an intersymbol interference component generated in the communication path, or may be an interference component from cross polarization in the communication path. Alternatively, the second distortion may include two or more of those distortions.

Further, either the first distortion or the second distortion may be distortion generated in the signal receiving apparatus 1 after the signal receiving apparatus 1 receives the signal. For example, the first distortion may be generated in the received signal by a non-linear device in the signal receiving apparatus 1 through which the received signal passes.

The distortion reducing unit 2 may reduce, for example, the second distortion of the received signal by 100% or nearly 100% (hereinafter referred to as “removal”), may reduce by approximately 50%, or may be approximately 30%. It may be reduced. In short, the distortion reduction unit 2 may perform a process in which the second distortion in the received signal is reduced to some extent.

The compensation coefficient calculation unit 3 calculates a compensation coefficient for compensating for the first distortion of the received signal based on the distortion reduction signal generated by the distortion reduction unit 2.

The distortion compensation unit 4 uses the compensation coefficient calculated by the compensation coefficient calculation unit 3 to generate a compensation signal that compensates for the first distortion of the received signal.

Note that each element of the distortion reduction unit 2, the compensation coefficient calculation unit 3, and the distortion compensation unit 4 shown in FIG. 1 as functional blocks for performing various processes is configured in terms of hardware such as a memory or other IC (Integrated Circuit). ) And the like, and in terms of software, it is realized by a program loaded in the memory. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof, and is not limited to any one.

FIG. 2 is a flowchart showing an example of processing executed by the signal receiving device 1 that has received a signal. Hereinafter, with reference to FIG. 2, processing executed by the signal receiving device 1 will be described.

The distortion reduction unit 2 generates a distortion reduction signal that reduces the second distortion while leaving the first distortion in the received signal (step S1).

The compensation coefficient calculation unit 3 calculates a compensation coefficient for compensating for the first distortion of the received signal based on the distortion reduction signal generated by the distortion reduction unit 2 (step S2).

The distortion compensation unit 4 uses the compensation coefficient calculated by the compensation coefficient calculation unit 3 to generate a compensation signal that compensates for the first distortion of the received signal (step S3). The details of the above processing are as described above.

Through the above processing, the signal receiving apparatus 1 can generate a compensation signal that compensates for the first distortion of the received signal. Then, the signal receiving apparatus 1 can accurately compensate for signal distortion.

The reason for this is as follows. The compensation coefficient calculation unit 3 is not a received signal including both the first distortion and the second distortion, but based on the compensation coefficient calculated based on the distortion reduction signal in which the second distortion is reduced. Is running. The compensation coefficient calculation unit 3 can calculate an accurate compensation coefficient for compensating for the first distortion as the amount of the second distortion included in the received signal decreases. Therefore, the compensation coefficient calculation unit 3 can calculate a more accurate compensation coefficient by using the distortion reduction signal than when the reception signal is used. Since the distortion compensator 4 compensates the first distortion of the reception signal based on a more accurate compensation coefficient, the first distortion compensation in the reception signal can be made more accurate.

In order for the signal receiving apparatus 1 to more accurately compensate for the first distortion of the received signal, the distortion reducing unit 2 only needs to reduce the second distortion in the received signal more. For example, when the distortion reduction unit 2 removes the second distortion, the distortion reduction signal becomes a signal that hardly includes the second distortion, so that the accuracy of the compensation coefficient calculated by the compensation coefficient calculation unit 3 is increased. Therefore, the distortion compensator 4 can compensate the first distortion more accurately.

The signal receiving apparatus 1 may further include a second distortion reducing unit that reduces the second distortion from the compensation signal output from the distortion compensating unit 4. Thereby, the signal receiving apparatus 1 can generate a reception signal in which the influence of the first distortion and the second distortion is reduced. Therefore, the signal receiving device 1 can execute more accurate communication.

Embodiment 2
The second embodiment of the present invention will be described below with reference to the drawings. 3 and 4 are block diagrams illustrating an example of the configuration of the transmitter and the receiver of the wireless communication system 10 according to the second embodiment.

First, a transmitter (wireless communication apparatus) according to the second embodiment will be described. The transmitter 20 wirelessly transmits a signal to the receiver side. As illustrated in FIG. 3, the transmitter 20 includes a modulation unit 21, a nonlinear device 22, and an antenna 23.

The modulation unit 21 modulates a transmission signal (main signal) to be transmitted to the receiver and outputs the modulated signal to the nonlinear device 22. The nonlinear device 22 is a device such as an amplifier, and performs some processing on the transmission signal (for example, amplification processing if the nonlinear device is an amplifier) and outputs the processed signal to the antenna 23.

Here, when the transmission signal passes through the nonlinear device 22, nonlinear distortion (first distortion) occurs in the transmission signal. That is, the non-linear device 22 corresponds to a noise source of the received signal. Therefore, the receiver side needs to compensate for the nonlinear distortion in order to accurately demodulate the signal.

The antenna 23 transmits the transmission signal acquired from the nonlinear device 22 to the receiver side by radio. Here, in the communication path in wireless communication, out-of-band interference waves (interference signals) are mixed in the transmission signal, and intersymbol interference occurs in the transmission signal. That is, in the communication path, a distortion of a type different from the nonlinear distortion caused by the nonlinear device 22 (second distortion) occurs in the received signal.

The out-of-band interference wave is an interference wave from a band other than the frequency band of the transmission signal. The out-of-band interference wave in the second embodiment indicates an interference wave from a signal in an adjacent frequency band adjacent to the frequency band of the transmission signal. However, the out-of-band interference wave may include an interference wave from a signal other than the frequency band adjacent to the frequency band of the transmission signal.

Next, a receiver according to the second embodiment will be described. The receiver 30 compensates for nonlinear distortion of the signal received from the transmitter 20 and executes demodulation processing.

As shown in FIG. 4, the receiver 30 (wireless communication apparatus) includes an antenna 31, a reception linearizer 32, an FIR filter 33, an automatic equalizer 34, a demodulator 35, an error detector 36, an intersymbol interference amount calculator 37, A compensation coefficient generation unit 38, a power calculation unit 39, a nonlinear distortion amount calculation unit 40, a compensation coefficient recording unit 41, a compensation coefficient control unit 42, an FIR filter 43, an automatic equalizer 44, and a power calculation unit 45 are provided. Hereinafter, processing performed by each unit of the receiver 30 will be described along a flow of processing executed when the receiver 30 receives a reception signal.

The antenna 31 receives a transmission signal transmitted from the transmitter 20. The antenna 31 outputs a reception signal to the reception linearizer 32. The received signal here
1: Non-linear distortion caused by the non-linear device 22 2: Out-of-band interference wave components mixed in the communication path 3: Three distortions of intersymbol interference components generated in the communication path are included. The receiver 30 removes these three distortions as follows. The definition of “removal” is as described in the first embodiment.

The reception linearizer 32 executes a nonlinear distortion compensation process for compensating the nonlinear distortion (1) generated by the nonlinear device 22 in the received signal, and outputs the received signal (compensation signal) that has been processed to the FIR filter 33. Here, the reception linearizer 32 uses the compensation coefficient output from the compensation coefficient control unit 42 to execute nonlinear distortion compensation processing. The reception linearizer 32 corresponds to the distortion compensator 4 according to the first embodiment.

The FIR filter 33 removes the out-of-band interference wave component (2) generated in the communication channel still remaining in the reception signal output from the reception linearizer 32, and outputs the reception signal to the automatic equalizer 34.

The automatic equalizer 34 (second equalizer) is a transversal type automatic equalizer, and the intersymbol interference component (3) generated in the remaining communication path in the received signal output from the FIR filter 33. ) And the received signal is output to the demodulator 35. Here, the automatic equalizer 34 performs a distortion compensation process using the compensation coefficient output from the compensation coefficient generation unit 38.

The demodulator 35 demodulates the received signal output from the automatic equalizer 34. In this way, the distortion of the received signal is compensated and the received signal is demodulated.

Next, a method for generating a compensation coefficient used in the reception linearizer 32 and the automatic equalizer 34 will be described.

The error detection unit 36 receives the reception signal output from the automatic equalizer 34. The error detector 36 detects an error component of the received signal that has been subjected to the distortion elimination processes (1) to (3), and outputs the information to the intersymbol interference amount calculator 37 and the nonlinear distortion amount calculator 40. To do.

The intersymbol interference amount calculation unit 37 calculates the intersymbol interference amount in the received signal based on the error component detected by the error detection unit 36, and outputs the information to the compensation coefficient generation unit 38.

The compensation coefficient generation unit 38 (interference compensation coefficient calculation unit) uses the intersymbol interference amount calculated by the intersymbol interference amount calculation unit 37 to generate a predetermined intersymbol interference compensation coefficient for compensating for the intersymbol interference. The information is output to the automatic equalizers 34 and 44. The automatic equalizer 34 executes distortion compensation processing using the intersymbol interference compensation coefficient.

The received signal output from the automatic equalizer 34 is input to the power calculator 39. The power calculator 39 calculates the power of the received signal and outputs the information to the nonlinear distortion calculator 40.

Here, in the received signal (input signal to the demodulator 35) output from the automatic equalizer 34, the out-of-band interference wave component (2) generated in the communication path is removed by the FIR filter 33, The intersymbol interference component (3) generated in the communication path is removed by the automatic equalizer 34. Therefore, the power of the input signal to the demodulator 35 has a value proportional to the input power to the nonlinear device 22. The power calculator 39 calculates the power of this input signal.

The non-linear distortion amount calculation unit 40 calculates the correction amount of the non-linear distortion (1) generated by the non-linear device 22 in the reception signal based on the error information of the reception signal detected by the error detection unit 36. At the same time, the nonlinear distortion amount calculation unit 40 reads a compensation coefficient corresponding to the power calculated by the power calculation unit 39 from the compensation coefficient recording unit 41. The nonlinear distortion amount calculation unit 40 overwrites the previously recorded compensation coefficient as a new nonlinear distortion compensation coefficient with the coefficient obtained by adding the calculated correction amount and the read compensation coefficient to the compensation coefficient recording unit 41. Record. In this way, the nonlinear distortion amount calculation unit 40 estimates the nonlinear distortion amount of the nonlinear device 22.

The compensation coefficient recording unit 41 records a compensation coefficient for compensating for the nonlinear distortion (1) generated by the nonlinear device 22 in the received signal. This compensation coefficient is updated by the processing of the nonlinear distortion amount calculation unit 40 described above. Further, the compensation coefficient recording unit 41 outputs the compensation coefficient to the compensation coefficient control unit 42 according to the processing of the compensation coefficient control unit 42.

The compensation coefficient control unit 42 reads the nonlinear distortion compensation coefficient from the compensation coefficient recording unit 41 according to the power calculated by the power calculation unit 45 and outputs the nonlinear distortion compensation coefficient to the reception linearizer 32. The error detection unit 36, the power calculation unit 39, the nonlinear distortion amount calculation unit 40, the compensation coefficient recording unit 41, and the compensation coefficient control unit 42 correspond to the compensation coefficient calculation unit 3 according to the first embodiment.

The FIR filter 43 removes the out-of-band interference wave component (2) from the reception signal input from the antenna 31 and outputs it to the automatic equalizer 44. The FIR filter 43 has the same function as the FIR filter 33.

The automatic equalizer 44 (first equalizer) is a transversal-type automatic equalizer, and the intersymbol interference component (in the remaining signal in the received signal output from the FIR filter 43) ( 3) is compensated, and the received signal is output to the power calculator 45. Here, the automatic equalizer 44 executes a distortion compensation process using the compensation coefficient output from the compensation coefficient generator 38. The automatic equalizer 44 has the same function as the automatic equalizer 34. The FIR filter 43 and the automatic equalizer 44 correspond to the distortion reduction unit 2 according to the first embodiment.

The power calculation unit 45 performs a signal (corresponding to the distortion reduction signal in the first embodiment) that has passed through the out-of-band interference wave removing FIR filter 43 and the automatic equalizer 44 with respect to the reception signal input from the antenna 31. Calculate power. In other words, the power calculation unit 45 removes the component (2) and the intersymbol interference component (3) of the out-of-band interference wave and includes only the nonlinear distortion (1) generated by the nonlinear device 22. The power is calculated. Therefore, the compensation coefficient control unit 42 can select and output an appropriate compensation coefficient corresponding to an appropriate power value.

In other words, the power calculator 45 does not calculate an incorrect power value due to interference of out-of-band adjacent waves or intersymbol interference. Therefore, the compensation coefficient control unit 42 does not select and output an incorrect compensation coefficient based on the incorrect power value.

Hereinafter, details of compensation processing for nonlinear distortion caused by the nonlinear device will be described.
FIG. 5 is a graph showing typical nonlinear distortion characteristics generated in a nonlinear device. The horizontal axis of the graph in FIG. 5 indicates the input power of the input signal to the nonlinear device, and the horizontal axis indicates the gain / phase value of the output signal output from the nonlinear device in accordance with the input signal.

When the input power of the input signal is small, the nonlinear device outputs an output signal having an ideal gain / phase value. However, when the input power of the input signal increases, the gain / phase value of the input signal decreases, so that the output signal of the nonlinear device has a characteristic deterioration amount (deviation from the ideal gain / phase value). Non-linear distortion amount) occurs. This characteristic deterioration amount is an amount that increases as the input power of the input signal increases. Thus, in the nonlinear device, the characteristic of nonlinear distortion changes depending on the input power.

Also in the nonlinear device 22 according to the second embodiment, characteristic degradation similar to that shown in FIG. 5 occurs. Therefore, the receiver 30 needs to estimate the input power to the nonlinear device 22 based on the power of the received signal, and to change the nonlinear distortion compensation coefficient of the nonlinear device 22 based on the estimated power.

Note that a characteristic deterioration amount (non-linear distortion amount) may be generated by increasing the input power of the input signal and increasing the gain / phase value of the input signal.

The compensation coefficient control unit 42 estimates the input power to the nonlinear device 22 based on the power calculated by the power calculation unit 45. Here, when the influence of other distortions (the component (2) of the out-of-band interference wave and the intersymbol interference component (3)) appears greatly in the power calculated by the power calculation unit 45, the compensation coefficient control unit 42 The input power to the nonlinear device 22 cannot be accurately estimated, and the nonlinear distortion compensation coefficient of the nonlinear device 22 cannot be selected correctly. In other words, when the ratio of the interference power generated by the component (2) of the out-of-band interference wave and the intersymbol interference component (3) is high in the power in the signal received by the antenna 31, the compensation coefficient control unit 42 is nonlinear. The compensation coefficient for nonlinear distortion of the device 22 cannot be selected correctly. In order to solve the problem, the receiver 30 is provided with an FIR filter 43 and an automatic equalizer 44 to execute processing for removing other distortions in the received signal.

Next, the details of the non-linear distortion compensation coefficient generation process will be described.

FIG. 6 is a block diagram showing an example of the configuration of the nonlinear distortion amount calculation unit 40. The nonlinear distortion amount calculation unit 40 includes an amplitude error detection unit 46, a phase error detection unit 47, an addition unit 48, and an address control unit 49.

The information of the error signal vector E of the received signal detected by the error detection unit 36 is output from the error detection unit 36.

FIG. 7 is a diagram showing an example of the error signal vector E of the received signal. Black dots in FIG. 7 indicate ideal signals, and white dots indicate received signals. The black dot closest to the white dot indicates an ideal received signal when there is no error.

In addition, the modulation | alteration part 21 is modulating by the modulation system of 16QAM (Quadrature | Amplitude | Modulation | modulation) here. However, also in other modulation schemes, the error detection unit 36 can similarly obtain the error signal vector E.

The amplitude error detection unit 46 detects the amplitude error vector G based on the error signal vector E input from the error detection unit 36. The amplitude error vector G corresponds to the amplitude component of the error signal vector E as shown in FIG. The amplitude error detection unit 46 outputs information on the amplitude error vector G to the addition unit 48.

The phase error detection unit 47 detects the phase error vector P based on the error signal vector E input from the error detection unit 36. This phase error vector P corresponds to the phase component of the error signal vector E as shown in FIG. The phase error detection unit 47 outputs information on the phase error vector P to the addition unit 48.

In parallel with the processing of the amplitude error detection unit 46 and the phase error detection unit 47, the address control unit 49 reads the compensation coefficient corresponding to the power calculated by the power calculation unit 39 from the compensation coefficient recording unit 41 and sends it to the addition unit 48. Process to output.

The addition unit 48 adds the error vector detected by the amplitude error detection unit 46 and the phase error detection unit 47 to the compensation coefficient input from the address control unit 49 and outputs the addition to the address control unit 49.

The address control unit 49 outputs the value input from the adding unit 48 to the compensation coefficient recording unit 41 as a new compensation coefficient. With the above operation, the nonlinear distortion amount calculation unit 40 can adaptively generate a compensation coefficient corresponding to the input power to the demodulation unit 35.

As described above, the power calculator 39 calculates the power of the input signal to the demodulator 35. This calculated power is a value proportional to the input power to the nonlinear device 22. Therefore, the non-linear distortion amount calculation unit 40 can calculate the non-linear distortion amount according to the input power to the non-linear device 22.

In addition, each element in the receiver 30 described in FIG. 4 and FIG. 6 as a functional block for performing various processes is configured by a circuit such as a memory or other IC (Integrated Circuit) in terms of hardware. In software, it is realized by a program loaded in a memory. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof, and is not limited to any one.

Next, a method in which the receiver 30 estimates input power to the nonlinear device 22 in the transmitter 20 will be described.

FIG. 8 is a graph showing an example of the spectrum of the input signal of the nonlinear device 22 in the transmitter 20. In the graph of FIG. 8, the horizontal axis represents frequency, and the vertical axis represents intensity (the same applies to FIG. 9). The spectrum of the input signal appears at the frequency ω1 to ω2.

FIG. 9 is a graph showing an example of the spectrum of the received signal in the receiver 30 when the input signal shown in FIG. 8 is input to the receiver 30. In FIG. 9, in the spectrum of the received signal of the receiver 30 corresponding to the spectrum of the input signal of the nonlinear device 22, the influence of intersymbol interference appears in the range of frequencies ω3 to ω4, and the signal strength in that range decreases. ing. Further, a spectrum of out-of-band interference waves different from the original signal transmitted by the transmitter 20 appears in the frequency ω5 to ω6.

Thus, in the received signal of the receiver 30, out-of-band interference waves and intersymbol interference occur depending on the situation in the communication path, and as a result, the power of the received signal changes as shown in FIG. There is a possibility that. If an out-of-band interference wave having the same spectrum as that of the received signal is included in addition to the original signal, the receiver 30 determines that two signals of the same level are input and determines the power value of the received signal. Will be judged more than the original. When intersymbol interference that lowers the signal strength occurs, the receiver 30 determines that the power value of the received signal is lower than the original value.

Accordingly, when interference as shown in FIG. 9 occurs in the received signal of the receiver 30, the receiver 30 encodes the out-of-band interference component (2) in the received signal by the automatic equalizer 44 using the FIR filter 43. The inter-interference component (3) is removed, and the signal corresponding to FIG. Therefore, the power calculation unit 45 can calculate power proportional to the input power to the nonlinear device 22 in the transmitter 20. The compensation coefficient control unit 42 estimates input power to the nonlinear device 22 based on this power.

In summary, the receiver 30 further includes a FIR filter 43 and an automatic equalizer 44 in front of the power calculation unit 45 in addition to the configuration of the receiver 200 according to the related technology shown in FIG. As a result, the receiver 30 can accurately estimate the input power of the nonlinear device 22 in the transmitter 20. As a result, the compensation coefficient control unit 42 can select the compensation coefficient accurately, and it is possible to realize highly accurate nonlinear distortion compensation even when interference occurs in the communication path.

Further, the received signal output via the nonlinear device 22 in the transmitter passes through the reception linearizer 32 in the receiver 30 and then passes through the FIR filter 33 and the automatic equalizer 34. Thus, since the reception linearizer 32 is mounted before the FIR filter 33 and the automatic equalizer 34, it is possible to prevent the reception linearizer 32 from performing inaccurate nonlinear distortion compensation.

In a wireless communication device, nonlinear distortion that depends on the characteristics of the nonlinear device in the analog portion of the device may occur in the signal, and desired communication characteristics may not be obtained. Therefore, the digital portion compensates for the nonlinear distortion. There is a need. The signal degradation due to nonlinear distortion is dominated by the influence of the nonlinear device in the transmission side apparatus.

As a compensation method for such nonlinear distortion, a method called a linearizer is generally used. The linearizer is a method for compensating for nonlinear distortion by giving a signal to a signal with a reverse characteristic of nonlinear distortion generated in a nonlinear device. The reception linearizer is an example of a nonlinear distortion compensation method using a linearizer, and estimates a nonlinear distortion amount of a nonlinear device in a transmission apparatus from a reception signal in the reception apparatus, generates a compensation coefficient, and compensates for the nonlinear distortion. is there.

In the configuration of the receiver 200 according to the related technology shown in FIG. 12, the received signal to the receiver 200 is directly input to the power calculation unit 213 and the power is calculated. Therefore, when interference as shown in FIG. 9 occurs on the communication path, the power calculation unit 213 calculates the power of the signal including the influence of the interference. Accordingly, since the compensation coefficient control unit 212 has selected the compensation amount corresponding to the calculated received power, it has not been possible to select an accurate compensation coefficient. For this reason, the reception linearizer 202 cannot accurately compensate for the nonlinear distortion characteristic caused by the nonlinear device.

In the receiver 30 according to the second embodiment, as shown in FIG. 4, the reception signal input to the power calculation unit 45 is provided by disposing the FIR filter 43 and the automatic equalizer 44 before the power calculation unit 45. Is restored from the one shown in FIG. 9 to the one shown in FIG. 8 (corresponding to the input signal inputted to the nonlinear device 22 in the transmitter 20). Thereby, the compensation coefficient control unit 42 can correctly estimate the input power input to the nonlinear device 22 based on the power calculated by the power calculation unit 45. In this way, the compensation coefficient control unit 42 selects a nonlinear distortion compensation amount in consideration of power such as an interference signal. For this reason, even when an interference signal or the like is present in the receiver 30, it is possible to improve the communication characteristics by performing accurate nonlinear distortion characteristic compensation (the above-described reception linearizer processing).

Furthermore, in the receiver 30 according to the second embodiment, the automatic equalizer 34 and the automatic equalizer 44 compensate for intersymbol interference using the same compensation coefficient generated by the compensation coefficient generator 38. For this reason, since it is not necessary to provide a plurality of compensation coefficient generating units in the receiver 30, the number of parts of the receiver 30 can be reduced, and the cost can be reduced.

In the receiver 30 shown in FIG. 4, a nonlinear device such as an amplifier may be provided between the antenna 31 and the reception linearizer 32. When the received signal passes through the nonlinear device, the received linearizer 32 can compensate for the nonlinear distortion even if nonlinear distortion depending on the characteristics of the nonlinear device occurs in the received signal. In this way, even when nonlinear distortion occurs due to the nonlinear device in the receiver 30 instead of the nonlinear device 22 in the transmitter 20, the nonlinear distortion can be compensated. Since this is the same as described above, it will be omitted.

The automatic equalizer 34 may be provided between the reception linearizer 32 and the FIR filter 33. Similarly, an automatic equalizer 44 may be provided before the FIR filter 43.

In the receiver 30 shown in FIG. 4, only one of the FIR filter 43 and the automatic equalizer 44 may be provided. Even in this case, distortion generated in the communication path is compensated to a certain degree in the signal input to the power calculation unit 45. The power calculation unit 45 calculates the power of the input signal. Therefore, compared to the related art, the compensation coefficient control unit 42 can more accurately estimate the input power input to the nonlinear device 22 and select the nonlinear distortion compensation amount. Therefore, communication characteristics can be improved. However, when it is desired to further improve the communication characteristics, it is desirable that the receiver 30 has both the FIR filter 43 and the automatic equalizer 44.

Embodiment 3
The third embodiment of the present invention will be described below with reference to the drawings. FIG. 10 is a block diagram illustrating an example of a configuration of a receiver according to the third embodiment. As in the second embodiment, the receiver 50 forms the wireless communication system 10 by combining the transmitter 20. The receiver 50 compensates for nonlinear distortion of the signal received from the transmitter 20 and executes demodulation processing.

In the third embodiment, the transmitter 20 and the receiver 50 perform wireless communication using cross polarization. Here, in a communication path using cross-polarization, in addition to out-of-band interference and intersymbol interference, interference from cross-polarization also occurs in the received signal. In other words, when there is another signal having a polarization characteristic different from (for example, orthogonal to) the received signal in the communication path, interference from the other signal occurs in the received signal. For example, when a received signal is wirelessly transmitted from the transmitter 20 to the receiver 50 with horizontal polarization and another signal is wirelessly transmitted from the transmitter 20 to the receiver 50 with vertical polarization, Interference occurs. The receiver 50 according to the third embodiment can perform an appropriate nonlinear distortion compensation process by removing the influence of the interference.

As shown in FIG. 10, similarly to the receiver 30, the receiver 50 (wireless communication apparatus) includes an antenna 31, a reception linearizer 32, an FIR filter 33, an automatic equalizer 34, a demodulator 35, an error detector 36, and an inter-symbol. Interference amount calculation unit 37, compensation coefficient generation unit 38, power calculation unit 39, nonlinear distortion amount calculation unit 40, compensation coefficient recording unit 41, compensation coefficient control unit 42, FIR filter 43, automatic equalizer 44, and power calculation unit 45 Is provided. The receiver 50 further includes a cross polarization interference removal unit 51, a cross polarization interference calculation unit 52, a compensation coefficient generation unit 53, and a cross polarization interference removal unit 54. Hereinafter, the points newly provided in comparison with the receiver 30 will be described.

The cross polarization interference removal unit 51 (second interference component reduction unit) is provided between the automatic equalizer 34 and the demodulation unit 35 and removes interference components from the cross polarization contained in the received signal. The reception linearizer 32, FIR filter 33, and automatic equalizer 34 compensate for nonlinear distortion (1), out-of-band interference wave component (2), and intersymbol interference component (3) caused by the nonlinear device 22 included in the received signal. However, the interference component from the cross polarization is not removed by each of these components. The cross polarization interference removing unit 51 compensates for this interference component and outputs the received signal to the demodulating unit 35. Here, the cross polarization interference removal unit 51 executes the distortion compensation process using the compensation coefficient output from the compensation coefficient generation unit 53.

The cross polarization interference calculation unit 52 calculates the cross polarization interference amount in the reception signal based on the error component detected by the error detection unit 36 and the reception signal of the cross polarization device, and uses the information as the compensation coefficient generation unit 53. Output to. The reception signal of the cross polarization device is a signal that has a relationship of cross polarization with the reception signal and causes interference with the reception signal, and is, for example, another signal transmitted orthogonally to the reception signal.

The compensation coefficient generation unit 53 (interference amount calculation unit) uses a cross polarization interference amount calculated by the cross polarization interference calculation unit 52 to use a predetermined cross polarization interference compensation coefficient ( Interference reduction coefficient) is generated, and the information is output to the cross polarization interference cancellation units 51 and 54. The cross polarization interference removal unit 51 executes distortion compensation processing using the cross polarization interference compensation coefficient.

The cross polarization interference removal unit 54 (first interference component reduction unit) is provided in the preceding stage of the FIR filter 43, and the antenna 31 uses the cross polarization interference compensation coefficient generated by the compensation coefficient generation unit 53. A distortion compensation process is performed on the received signal. The cross polarization interference removal unit 54 outputs the reception signal that has been subjected to this processing to the FIR filter 43.

Since the processing of each other part of the receiver 50 is as described in the second embodiment, the description thereof is omitted.

Note that each element of the cross polarization interference removing unit 51 to the cross polarization interference removing unit 54 can be configured by a circuit such as a memory or other IC in terms of hardware, and in the memory in terms of software. Realized by a loaded program. Therefore, it is understood by those skilled in the art that these functional blocks can be realized in various forms by hardware only, software only, or a combination thereof, and is not limited to any one. For example, the cross polarization interference removing unit 51 can be configured by an XPIC (Cross Polarization Interference Cancerer) circuit.

In the case of communication using cross polarization in wireless communication, there is a possibility that accurate nonlinear distortion characteristics cannot be compensated because the received signal power changes due to interference components from the cross polarization in the communication path.

In order to solve this problem, in the receiver 50 according to the third embodiment, the cross polarization interference removal unit 54 is disposed in the previous stage of the power calculation unit 45. Thereby, the power calculation unit 45 calculates the power of the received signal from which the cross polarization interference is removed. The compensation coefficient control unit 42 selects a compensation coefficient based on the calculated power and supplies it to the reception linearizer 32. In this manner, the receiver 30 performs nonlinear distortion compensation for compensating for nonlinear distortion caused by the nonlinear device 22 based on the received signal from which cross-polarized interference has been removed. As a result, even when cross-polarization interference occurs, accurate nonlinear distortion compensation can be realized in the receiver 30, and communication characteristics can be improved.

Further, in the receiver 50 according to the third embodiment, the cross polarization interference removal unit 51 and the cross polarization interference removal unit 54 remove the cross polarization interference using the same compensation coefficient generated by the compensation coefficient generation unit 53. is doing. For this reason, since it is not necessary to provide a plurality of cross polarization interference removal units in the receiver 50, the number of parts of the receiver 50 can be reduced, and the cost can be reduced.

The order of the FIR filter 33, the automatic equalizer 34, and the cross polarization interference removing unit 51 can be changed. For example, the cross polarization interference removal unit 51 may be provided between the FIR filter 33 and the automatic equalizer 34, or may be provided between the reception linearizer 32 and the FIR filter 33. Similarly, the context of the cross polarization interference removing unit 54, the FIR filter 43, and the automatic equalizer 44 can be changed. For example, the cross polarization interference removal unit 54 may be provided between the FIR filter 43 and the automatic equalizer 44, or may be provided between the automatic equalizer 44 and the power calculation unit 45.

In the receiver 50 shown in FIG. 10, the FIR filter 43 and the automatic equalizer 44 may not be provided. Even in this case, the compensation coefficient control unit 42 can more accurately estimate the input power input to the nonlinear device 22 and select the nonlinear distortion compensation amount as compared with the related art. Therefore, communication characteristics can be improved. However, when it is desired to further improve the communication characteristics, it is desirable that at least one of the FIR filter 43 and the automatic equalizer 44 is provided in the receiver 50 (both the FIR filter 43 and the automatic equalizer 44 are provided). If the configuration is provided, the communication characteristics can be most improved.)

One of the factors that degrade transmission characteristics in digital microwave communication devices used for communication between trunk lines and mobile phone base stations is the influence of nonlinear distortion in the analog portion (nonlinear device) in the communication device. In recent years, in order to realize large-capacity transmission with respect to digital microwave communication apparatuses, signal multi-value (256QAM, 512QAM, etc.) has been advanced. With the increase in the number of signals, the deterioration of the transmission characteristics due to the analog part in the communication apparatus cannot be ignored, and a method for compensating the transmission characteristics with higher accuracy has been studied. The devices according to the first to third embodiments solve this problem and can be applied to, for example, digital microwave communication.

Note that the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention. In other words, various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. For example, the above embodiment has described an example in which distortion in a communication channel is an out-of-band interference wave component, an intersymbol interference component, and an interference component from cross polarization. However, even when other distortion occurs in the received signal in the communication path, the receiver can accurately compensate for the nonlinear distortion caused by the nonlinear device in the same manner as in the above embodiment.

The signal receiving device can be further configured as follows. A calculation unit that calculates a compensation coefficient for compensating the first distortion for the reception signal in which the second distortion is reduced based on the reception signal including the first distortion and the second distortion; The signal receiving apparatus can be configured to include a generation unit that generates a compensation signal that compensates for the first distortion of the received signal using the compensation coefficient. Here, the calculation unit may generate a reception signal in which the second distortion is reduced as in the first embodiment, and calculate the compensation coefficient using the reception signal. Alternatively, the calculation unit calculates a compensation coefficient based on the received signal including the first distortion and the second distortion, and the received signal in which the second distortion is reduced using the compensation coefficient and a predetermined correction amount. Alternatively, a compensation coefficient for compensating for the first distortion may be calculated. This correction amount is a difference between the compensation coefficient in the received signal including the first distortion and the second distortion and the compensation coefficient in the received signal in which the second distortion is reduced.

Even if the FIR filter 43 according to the second and third embodiments is reduced to, for example, about 50% without removing the interference wave component, the above-described effects can be obtained. However, in order to execute accurate nonlinear distortion compensation processing, it is desirable to remove the interference wave component by the FIR filter 43. The same applies to the automatic equalizer 44 and the cross polarization interference removal unit 54.

The processing of the apparatus described in Embodiments 1 to 3 and the above-described note can be executed by a power supply circuit provided in a computer as one of control methods. For example, as a control program, the processing flow shown in the first embodiment may be executed by a computer that receives a signal from the signal transmission device. The same applies to other processing flows.

The program can be stored and supplied to a computer using various types of non-transitory computer readable media. Non-transitory computer readable media include various types of tangible storage media (tangible storage medium). Examples of non-transitory computer readable media are magnetic recording media (eg flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (eg magneto-optical disks), CD-ROM, CD-R, CD-R / W Semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable ROM), flash ROM, RAM (Random Access Memory)). The program may also be supplied to the computer by various types of temporary computer-readable media. Examples of transitory computer readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

This application claims priority based on Japanese Patent Application No. 2013-050400 filed on March 13, 2013, the entire disclosure of which is incorporated herein.

DESCRIPTION OF SYMBOLS 1 Signal receiver 2 Distortion reduction part 3 Compensation coefficient calculation part 4 Distortion compensation part 10 Wireless communication system 20 Transmitter 21 Modulation part 22 Non-linear device 23 Antenna 30 Receiver 31 Antenna 32 Reception linearizer 33 FIR filter 34 Automatic equalizer 35 Demodulation Unit 36 error detection unit 37 intersymbol interference amount calculation unit 38 compensation coefficient generation unit 39 power calculation unit 40 nonlinear distortion amount calculation unit 41 compensation coefficient recording unit 42 compensation coefficient control unit 43 FIR filter 44 automatic equalizer 45 power calculation unit 46 Amplitude error detection unit 47 Phase error detection unit 48 Addition unit 49 Address control unit 50 Receiver 51 Cross polarization interference removal unit 52 Cross polarization interference calculation unit 53 Compensation coefficient generation unit 54 Cross polarization interference removal unit

Claims (19)

A signal receiving device for receiving a signal from a signal transmitting device,
Distortion reducing means for generating a distortion reduction signal in which the second distortion is reduced while leaving the first distortion among the received signals including the first distortion and the second distortion;
Compensation coefficient calculating means for calculating a compensation coefficient for compensating for the first distortion of the received signal based on the distortion reduction signal;
Distortion compensation means for generating a compensation signal that compensates for the first distortion of the received signal using the compensation coefficient;
A signal receiving device. The first distortion is a non-linear distortion caused by a non-linear device, and the second distortion is a distortion generated in a communication path between the signal transmitting device and the signal receiving device.
The signal receiving device according to claim 1. The second distortion includes intersymbol interference of the received signal;
The distortion reducing means includes a first equalizer that compensates for the intersymbol interference of the received signal using a predetermined intersymbol interference compensation coefficient for compensating for the intersymbol interference.
The signal receiving device according to claim 2. The signal receiving apparatus compensates the intersymbol interference of the compensation signal using the predetermined intersymbol interference compensation coefficient; and
The signal receiving apparatus according to claim 3, further comprising: an interference compensation coefficient calculating unit that calculates the predetermined intersymbol interference compensation coefficient and outputs the calculated intersymbol interference compensation coefficient to the first equalizer and the second equalizer. The second distortion includes an interference wave from a signal in an adjacent frequency band adjacent to the frequency band of the received signal;
The distortion reducing means includes a filter that reduces a component of the interference wave from the received signal.
The signal receiving device according to any one of claims 2 to 4. The second distortion includes an interference component caused by interference from another signal having a polarization characteristic different from that of the received signal,
The distortion reduction means includes first interference component reduction means for reducing the interference component from the received signal using a predetermined interference reduction coefficient for reducing interference.
The signal receiving device according to any one of claims 2 to 5. The signal receiving device includes: a second interference component reducing unit configured to reduce the interference component of the compensation signal using the predetermined interference reduction coefficient;
The signal reception apparatus according to claim 6, further comprising: an interference amount calculation unit that calculates the predetermined interference reduction coefficient and outputs the calculated interference reduction coefficient to the first interference component reduction unit and the second interference component reduction unit. The compensation coefficient calculating means calculates a compensation coefficient according to the power of the distortion reduction signal;
The signal receiving device according to any one of claims 1 to 7. A signal transmission device for transmitting the received signal;
The signal receiving device according to any one of claims 1 to 8, which receives the received signal;
A wireless communication system comprising: A distortion compensation method for a signal reception device that receives a signal from a signal transmission device, comprising:
Based on the received signal including the first distortion and the second distortion, a compensation coefficient for compensating the first distortion with respect to the received signal in which the second distortion is reduced,
Using the compensation factor to generate a compensation signal that compensates for the first distortion of the received signal;
Distortion compensation method. In calculating the compensation coefficient,
Generating a distortion reduction signal in which the second distortion is reduced while leaving the first distortion in the received signal, and calculating the compensation coefficient based on the distortion reduction signal. Item 11. The distortion compensation method according to Item 10. The first distortion is a non-linear distortion caused by a non-linear device, and the second distortion is a distortion generated in a communication path between the signal transmitting device and the signal receiving device.
The distortion compensation method according to claim 11. The second distortion includes intersymbol interference of the received signal;
In the generation of the distortion reduction signal, the intersymbol interference of the received signal is compensated using a predetermined intersymbol interference compensation coefficient for compensating for the intersymbol interference.
The distortion compensation method according to claim 12. The distortion compensation method further includes compensating the intersymbol interference of the compensation signal using the predetermined intersymbol interference coefficient.
The distortion compensation method according to claim 13. The second distortion includes an interference wave from a signal in an adjacent frequency band adjacent to the frequency band of the received signal;
In the generation of the distortion reduction signal, the interference wave component is reduced from the received signal.
The distortion compensation method according to any one of claims 12 to 14. The second distortion includes an interference component caused by interference from another signal having a polarization characteristic different from that of the received signal,
In the generation of the distortion reduction signal, the interference component is reduced from the received signal using a predetermined interference reduction coefficient for reducing interference.
The distortion compensation method according to any one of claims 12 to 15. Further comprising reducing the interference component of the compensation signal using the predetermined interference reduction factor;
The distortion compensation method according to claim 16. In calculating the compensation coefficient, a compensation coefficient is calculated according to the power of the distortion reduction signal.
The distortion compensation method according to any one of claims 11 to 17. A non-transitory computer-readable medium storing a program to be executed by a computer that receives a signal from a signal transmission device,
Based on the received signal including the first distortion and the second distortion, a compensation coefficient for compensating the first distortion with respect to the received signal in which the second distortion is reduced,
Using the compensation coefficient to generate a compensation signal that compensates for the first distortion of the received signal;
A non-transitory computer-readable medium storing a program for causing a computer to execute the program.

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