wireless communication system

Abstract

To provide a wireless communication system that can eliminate interference waves that go around from the transmitting antenna of its own station to the receiving antenna of its own station with high accuracy.SOLUTION: In a wireless communication system, a transmitting device includes a PA replica generation unit 5c that generates a replica signal of a PA from a portion of an output signal from a PA 54, and a receiving device includes a subtractor 59 that subtracts a replica signal of an interference wave from a received signal from a receiving antenna 58, and an interference replica generation unit 5d that generates the replica signal of the interference wave so as to minimize a residual component included in the signal subtracted by the subtractor 59 with the replica signal of the PA as a reference signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wireless communication system for performing wireless communication, and more particularly to a wireless communication system capable of highly accurately removing interference waves that have leaked from a transmitting antenna of the own station to a receiving antenna of the own station. [Background technology]

[0002] [Prior Art] Currently, the need for wireless communication, such as fifth generation communication, wireless LAN (Local Area Network), and private wireless systems, is increasing, and wireless frequencies are becoming scarce. Therefore, developments are underway to improve utilization efficiency in the spatial and frequency domains.

[0003] In wireless communication, two-way communication between a base station and a terminal station is the norm, but to prevent the station's own transmission signal from looping around and interfering with the received signal, time-division communication methods that avoid interference on the time axis and frequency-division communication methods that avoid interference on the frequency axis are commonly used.

[0004] However, as mentioned above, there is a growing demand for full-duplex wireless communication in order to improve frequency utilization efficiency. Full-duplex wireless communication is a wireless communication method in which two-way communication is performed using the same frequency.

[0005] However, unlike time division or frequency division communications, full-duplex wireless communications are subject to interference from the signal transmitted by the local station. As a result, two wireless signals arrive at the receiving antenna, with the originally desired received signal (hereafter referred to as the "desired signal") being mixed with an interference signal (hereafter referred to as the "interference signal") that has leaked from the local station's transmitting antenna.

[0006] This interference wave acts as a disturbance to the desired wave and significantly degrades the reception characteristics of the desired wave. For this reason, full-duplex wireless communication uses an interference canceller to remove the mixed-in interference wave. An interference canceller is a technology that generates a replica of an interference wave inside a receiver, subtracts the interference wave replica from a received signal that contains a mixture of a desired wave and an interference wave, and extracts only the desired wave.

[0007] [Conventional wireless communication system: Figure 2] A conventional full-duplex wireless communication system having an interference cancellation function will be described with reference to Fig. 2. Fig. 2 is a block diagram showing the configuration of the conventional wireless communication system. As shown in FIG. 2, a conventional wireless communication system includes, as a transmitting device, a modulated signal generating unit 11, a DAC (D / A converter) 12, a PA (power amplifier) ​​13, and a transmitting antenna 14, and, as a receiving device, a receiving antenna 16, a subtractor 17, an LNA (Low Noise Amplifier) ​​18, an ADC (A / D converter) 19, an interference replica generating unit 1a, a DAC (D / A converter) 1b, and a desired wave demodulating unit 1c. The path along which the interference wave travels from the transmitting antenna 14 to the receiving antenna 16 is referred to as a propagation path 15 .

[0008] In a conventional wireless communication system, as shown in FIG. 2, a modulated signal generator 11 generates a modulated signal (x U0 ) to generate the modulated signal (x U0 ) is converted from a digital signal to an analog signal by the DAC 12, and the amplitude is amplified by g times by the power amplifier (PA) 13. Normally, g>1, but for ease of explanation, the amplitude amplification is assumed to be g=1. Then, the amplified modulated signal (x U0 ) is transmitted as a radio signal from a transmitting antenna 14.

[0009] Here, while typical radios often include a frequency converter that converts the frequency of a modulated signal into a radio frequency band signal, recent advances in digital technology have made it possible to generate a radio frequency band signal directly from the DAC 12. Since the presence or absence of a frequency converter is not directly related to the present invention, the following description will omit frequency conversion.

[0010] A signal transmitted from a transmitting antenna 14 travels through a propagation path 15 and reaches a receiving antenna 16 as an interference wave (x U ) arrives as interference waves (x U ) is subjected to linear amplitude and phase distortion (h) due to the propagation path 15, and is expressed as Equation (1) below in [Equation 1].

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[0011] In addition, the receiving antenna 16 receives the desired signal (x D ) also reaches desired wave(x D ) and interference wave (x U The received signal containing the mixed components is input to the + terminal of the subtractor 17. Furthermore, an interference wave replica signal is input to the minus terminal of the subtractor 17. The interference wave replica signal is expressed by the following [Equation 2].

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[0012] The subtractor 17 subtracts the desired signal (x D ) and interference wave (x U ) mixed signal (x D +x U ) and subtract the interference replica signal from it, and the subtraction result x D +ε, where ε is the residual signal and the interference signal (x U ) from which the interference replica signal is subtracted.

[0013] The output of the subtractor 17 is power-amplified by the LNA 18 and converted from an analog signal to a digital signal by the ADC 19 . The output signal of the ADC 19 is input to the interference replica generator 1a, and the other input of the interference replica generator 1a receives the modulated signal (x U0 ) is entered.

[0014] The interference replica generator 1a generates a modulated signal (x U0 ) is used as a known reference signal, and the interference replica signal is subtracted from the received signal to obtain x D +ε is input, and the residual component ε is minimized to generate an interference wave replica signal, and the generated interference wave replica signal is written in Equation (2) of [Equation 3] below.

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[0015] The interference wave (x U ) and the interference wave replica signal of Equation (2), the channel characteristic estimate is obtained from the channel characteristic h. The channel characteristic estimate is shown in the following [Equation 4].

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[0016] This estimation method includes a method in which a known signal is inserted into the modulated signal and the transmission path characteristic h is estimated based on the received known signal, and a method in which the residual signal ε is calculated sequentially so as to be small. The interference wave replica signal is input to DAC 1 b, where it is converted from a digital signal to an analog signal, and input to the − terminal of subtractor 17 .

[0017] In the interference canceller described above, it is desirable that the residual signal ε be 0. If ε=0, the desired signal (x D ) is completely extracted. D ) is input to a desired wave demodulation unit 1c, which demodulates the desired wave from the other station to realize communication. In this way, in a full-duplex wireless communication device equipped with an interference cancellation function, the local transmission signal (x U ) to cancel the desired signal (x D) to realize two-way communication without causing degradation of reception characteristics due to interference waves.

[0018] [Power amplifier input / output amplitude characteristics: Figure 3] The input / output amplitude characteristics of a conventional power amplifier will be described with reference to Fig. 3. Fig. 3 is an explanatory diagram showing the input / output amplitude characteristics of a power amplifier. In the wireless communication system of FIG. 2, the PA 13 has a function of amplifying the power of a modulated transmission signal, but an actual power amplifier cannot maintain linearity and results in nonlinear conversion.

[0019] The horizontal axis of Figure 3 represents the amplitude of the input signal, and the vertical axis represents the amplitude of the output signal. This characteristic is called the AM-AM characteristic. The solid line in Figure 3 shows that the output amplitude is linearly multiplied by g relative to the input amplitude, but actual power amplifiers can only output a finite amount of power, and as the dotted line shows, as the input signal increases, the amplification factor g decreases, saturating at a certain output power. In this way, the AM-AM characteristics of an actual power amplifier are nonlinear functions.

[0020] [Frequency characteristics of nonlinear distortion signal: Figure 4] The frequency characteristics of a conventional nonlinear distortion signal will be described with reference to Fig. 4. Fig. 4 is an explanatory diagram showing the frequency characteristics of a nonlinear distortion signal. The nonlinear distortion described above causes a spread in the frequency domain compared to a linear signal, as shown in the example of Figure 4. This is because the nonlinear distortion generates multiple new high-order distortion components, and the high-order distortion components have a wide frequency band, resulting in the spread shown in Figure 4. Details of these high-order distortion components will be described later.

[0021] [Canceled residual signal: Figure 5] Next, the cancellation residual signal will be described with reference to Fig. 5. Fig. 5 is an explanatory diagram showing the state of the cancellation residual signal in the frequency domain. FIG. 5 is a diagram showing, in the frequency domain, a cancellation residual signal ε when cancellation processing is performed by the canceller shown in FIG. 2 in a state where such nonlinear distortion occurs.

[0022] If all signals operate in a linear region and the cancellation operation is ideal, the cancellation residual signal will also have a small value (here, -100 dB) over a wide frequency range. However, if nonlinear distortion occurs, the interference replica signal generated from the linear signal does not contain the nonlinear distortion components, and cancellation residuals due to the nonlinear distortion components remain.

[0023] [Related Technology] Related prior art includes Japanese Patent Application Publication No. 2011-055125, "Signal compensation device, signal compensation method, signal compensation program, computer-readable recording medium, and communication device" (Patent Document 1), and Japanese Patent Application Publication No. 11-088230, "Interference canceller" (Patent Document 2).

[0024] Patent Document 1 shows that a replica signal of an OB signal is input into a nonlinear compensation model that shows the input / output characteristics of a TWTA, in which the input / output characteristics of an output signal relative to an input signal include a linear region and a nonlinear region, to generate a compensated replica signal. Patent Document 2 discloses an interference canceller that cancels a replica signal from an input signal. [Prior art documents] [Patent documents]

[0025] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-055125 [Patent Document 2] Japanese Patent Application Publication No. 11-088230 Summary of the Invention [Problem to be solved by the invention]

[0026] As described above, when nonlinear distortion occurs due to the PA 13, the nonlinear distortion component remains as a cancellation residual, which poses a problem in that highly accurate cancellation processing cannot be achieved.

[0027] Patent Documents 1 and 2 do not describe a configuration that can accurately remove interference waves that have leaked from the transmitting antenna of the local station to the receiving antenna of the local station even if nonlinear distortion occurs in a power amplifier (PA) in transmission processing.

[0028] The present invention has been made in view of the above circumstances, and has as its object to provide a wireless communication system capable of highly accurately removing interference waves that have leaked from the transmitting antenna of the own station to the receiving antenna of the own station. [Means for solving the problem]

[0029] The present invention, which solves the problems of the above-described conventional example, is a wireless communication system comprising a transmitting device and a receiving device, wherein the transmitting device comprises a modulated signal generating section which generates a modulated signal, a power amplifier which power-amplifies the modulated signal for transmission, a transmitting antenna which sends out the power-amplified signal for transmission, and a power amplifier replica generating section which generates a power amplifier replica signal from a part of an output signal from the power amplifier, and the receiving device comprises a receiving antenna for reception, a subtractor which subtracts an interference wave replica signal from a received signal from the receiving antenna, and an interference replica generating section which uses the power amplifier replica signal generated by the power amplifier as a reference signal and generates the interference wave replica signal so that a residual component included in the signal subtracted by the subtractor is minimized. a desired wave demodulation unit that demodulates the signal subtracted by the subtractor; Equipped with The power amplifier replica generator estimates a nonlinear distortion signal included in the output signal from the power amplifier to generate a replica signal of the power amplifier, and the interference replica generator estimates the propagation path characteristics of the loop interference from the transmitting antenna to the receiving antenna and generates a replica signal of the interference wave by multiplying the reference signal by the estimated value of the propagation path characteristics. It is characterized by:

[0030] The present invention provides A wireless communication system comprising a transmitting device and a receiving device, wherein the transmitting device comprises a modulated signal generating unit that generates a modulated signal, a power amplifier that power-amplifies the modulated signal for transmission, a transmitting antenna that sends out the power-amplified signal for transmission, and a power amplifier replica generating unit that generates a power amplifier replica signal from a part of an output signal from the power amplifier; the receiving device comprises a receiving antenna for reception, a subtractor that subtracts an interference wave replica signal from a received signal from the receiving antenna, an interference replica generating unit that uses the power amplifier replica signal generated by the power amplifier as a reference signal and multiplies the reference signal by an estimated value of the transmission path characteristics of loop interference from the transmitting antenna to the receiving antenna to generate the interference wave replica signal, and at that time generates the interference wave replica signal so that a residual component included in the signal subtracted by the subtractor is minimized, and a desired wave demodulating unit that demodulates the signal subtracted by the subtractor; The transmitter includes a coupler that separates a part of an output signal from a power amplifier, and a power amplifier replica coefficient calculation unit that calculates model coefficients of a model that imitates the power amplifier based on the output signal from the coupler and a modulated signal. Yes The power amplifier replica generator uses the coefficients based on the modulated signal. Power amplifier The present invention is characterized by generating a replica signal of the above.

[0031] The present invention is characterized in that, in the above-mentioned wireless communication system, a first delay adjustment unit is provided in the preceding stage of the power amplifier to delay the modulated signal in order to adjust the timing of input of the received signal and the replica signal of the interference wave in the subtractor.

[0032] The present invention is characterized in that, in the above-mentioned wireless communication system, a second delay adjustment unit is provided that delays the input of the modulated signal in order to adjust the input timing of the modulated signal in the power amplifier replica coefficient calculation unit and the output signal from the coupler.

[0033] The present invention is characterized in that in the wireless communication system, the power amplifier replica coefficient calculation unit calculates model coefficients of a model that imitates the power amplifier by comparing a linear signal of the modulated signal with a nonlinear signal of the output signal from the coupler. [Effects of the Invention]

[0034] According to the present invention, there is provided a wireless communication system including a transmitting device and a receiving device, wherein the transmitting device includes a modulated signal generating unit that generates a modulated signal, a power amplifier that power-amplifies the modulated signal for transmission, a transmitting antenna that sends out the power-amplified signal for transmission, and a power amplifier replica generating unit that generates a power amplifier replica signal from a part of an output signal from the power amplifier, and the receiving device includes a receiving antenna for reception, a subtractor that subtracts an interference wave replica signal from a received signal from the receiving antenna, and an interference replica generating unit that uses the power amplifier replica signal generated by the power amplifier as a reference signal and generates the interference wave replica signal so that a residual component included in the signal subtracted by the subtractor is minimized. a desired wave demodulation unit that demodulates the signal subtracted by the subtractor; Equipped with The power amplifier replica generator estimates a nonlinear distortion signal included in the output signal from the power amplifier to generate a replica signal of the power amplifier, and the interference replica generator estimates the propagation path characteristics of the loop interference from the transmitting antenna to the receiving antenna and generates a replica signal of the interference wave by multiplying the reference signal by the estimated value of the propagation path characteristics. Since it is a wireless communication system, it has the effect of being able to remove with high precision any interference waves that have leaked from the transmitting antenna of the own station to the receiving antenna of the own station. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a configuration block diagram of the present system. [Figure 2] FIG. 1 is a block diagram illustrating a configuration of a conventional wireless communication system. [Figure 3] FIG. 2 is an explanatory diagram showing input / output amplitude characteristics of a power amplifier. [Figure 4] FIG. 2 is an explanatory diagram showing frequency characteristics of a nonlinear distortion signal. [Figure 5] FIG. 10 is an explanatory diagram showing the state of a cancellation residual signal in the frequency domain. DETAILED DESCRIPTION OF THE INVENTION

[0036] An embodiment of the present invention will be described with reference to the drawings. [Outline of the embodiment] A wireless communication system (the present system) according to an embodiment of the present invention comprises a transmitting device and a receiving device, wherein the transmitting device comprises a modulated signal generating unit that generates a modulated signal, a power amplifier that power-amplifies the modulated signal for transmission, a transmitting antenna that sends out the power-amplified signal for transmission, and a power amplifier replica generating unit that generates a power amplifier replica signal from a portion of the output signal from the power amplifier, and the receiving device comprises a receiving antenna for reception, a subtractor that subtracts an interference wave replica signal from the signal received from the receiving antenna, and an interference replica generating unit that uses the power amplifier replica signal generated by the power amplifier as a reference signal and generates an interference wave replica signal so that the residual component included in the signal subtracted by the subtractor is minimized.As a result, the wireless communication system can accurately remove interference waves that have slipped from the transmitting antenna of the local station to the receiving antenna of the local station.

[0037] [System configuration: Figure 1] The configuration of this system will be described with reference to Figure 1. Figure 1 is a block diagram of the configuration of this system. As shown in FIG. 1, this system includes, as a transmitting device, a modulated signal generating unit 51, a delay adjusting unit (first delay adjusting unit) 52, a DAC (D / A converter) 53, a PA (power amplifier) ​​54, a coupler 55, a transmitting antenna 56, a PA replica generating unit 5c, an ADC (A / D converter) 5g, a PA replica coefficient calculating unit 5h, and a delay adjusting unit (second delay adjusting unit) 5i, and as a receiving device, a receiving antenna 58, a subtractor 59, an LNA (Low Noise Amplifier) ​​5a, an ADC (A / D converter) 5b, an interference replica generating unit 5d, a DAC (D / A converter) 5e, and a desired wave demodulating unit 5f.

[0038] In the following explanation, we will first explain the series of processes for generating a nonlinear interference replica signal and canceling the interference wave, then explain the issues and solutions for timing adjustment related to PA replica generation, and finally explain the PA replica generation method.

[0039] [Parts of this system] Each part of this system will now be described in detail. [Modulation signal generation unit 51] The modulation signal generator 51 generates a modulation signal (x U0 ) to generate the modulated signal (x U0 ) is output to the delay adjustment unit 52 and the PA replica generation unit 5c. [Delay adjustment unit 52] The delay adjustment unit 52 performs time delay processing on the modulated signal and outputs the result to the DAC 53. Details of this delay adjustment processing will be described later.

[0040] [DAC53] The DAC 53 receives the output of the delay adjustment unit 52 and converts it from a digital signal to an analog signal. [PA54] The PA54 converts the modulated signal (x U0 ) and amplify the signal. As mentioned above, nonlinear distortion occurs in the PA54 in real power amplifiers, and this nonlinear distortion function is defined as f(x U0 )

[0041] [Coupler 55] The coupler 55 couples the radio signal f(x U0 ) is input and output to the transmitting antenna 56, and a portion of the power of the input signal is output to the C terminal. Since the power output to the C terminal is minute, the coupler has little transmission loss.

[0042] [Transmitting antenna 56] A transmitting antenna 56 transmits the output from the coupler 55 . The signal sent from the transmitting antenna 56 passes through the propagation path 57 and reaches the receiving antenna 58 of the own station as an interference wave (x U ) arrives as interference waves (x U ) is subjected to linear amplitude and phase distortion (h) due to the propagation path 57, and is expressed as the following mathematical expression (3) of [Mathematical Expression 5].

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[0043] [Receiving antenna 58] The receiving antenna 58 receives the desired signal (x) from the other station in the same manner as the receiving antenna 16 in FIG. D ) also arrives, and the desired wave (x D ) and interference wave (x U ) is input and output to the + terminal of the subtractor 59. [Subtractor 59] The subtractor 59 inputs the desired signal (x D ) and interference wave (x U ) is input to the received signal, and the interference wave replica signal is input to the - terminal. The output of the subtractor 59 is the desired signal (x D) and the cancellation residual signal ε. The cancellation residual signal ε is obtained by subtracting the interference replica signal from the desired signal.

[0044] [LNA5a] The LNA 5 a amplifies the power of the output from the subtractor 59 . Here, if excessive signal power is input to the LNA 5a, signal degradation due to nonlinear distortion occurs, and in the worst case, it may lead to a malfunction. Therefore, by providing a subtractor 59 that operates in the linear region in the stage preceding the LNA 5a, the interference wave is removed before input to the LNA 5a, and the nonlinear distortion of the LNA 5a is significantly improved. [ADC5b] The ADC 5b converts the output from the LNA 5a from an analog signal to a digital signal, and outputs the digital signal to the interference replica generator 5d and the desired wave demodulator 5f.

[0045] [Interference replica generation unit 5d] The interference replica generator 5d receives the output signal from the ADC 5b and the modulated signal from the PA replica generator 5c that simulates the nonlinear distortion in the PA 54, generates an interference replica signal based on the modulated signal, and outputs the generated interference replica signal to the DAC 5e. The generation of the interference replica signal will be described in detail later. [DAC5e] The DAC 5e converts the interference replica signal output from the interference replica generating unit 5d from a digital signal into an analog signal and outputs the analog signal to the negative terminal of the subtractor.

[0046] [ADC5g] The ADC 5g receives a portion of the power of the transmission signal from the coupler 55, converts it from an analog signal to a digital signal, and outputs it to the PA replica coefficient calculation unit 5h, which detects nonlinear distortion of the PA 54 from this portion of the power. [Delay adjustment unit 5i] The delay adjustment unit 5i delays the modulated signal output from the modulated signal generation unit 51 and outputs the delayed modulated signal to the PA replica coefficient calculation unit 5h at the same timing as the modulated signal is input from the ADC 5g to the PA replica coefficient calculation unit 5h.

[0047] [PA replica coefficient calculation section 5h] The PA replica coefficient calculation unit 5h calculates the delayed modulated signal (x U0 ) and the radio signal f(x U0 ) and outputs the coefficient w (model coefficient of the model simulating PA 54) for generating a PA replica signal (a replica signal of the modulated signal simulating nonlinear distortion in PA 54) to PA replica generating unit 5c.

[0048] [PA replica generation unit 5c] The PA replica generator 5c receives the modulated signal (x U0 ), a coefficient w for forming a modulated signal (PA replica signal) that simulates (is simulating) nonlinear distortion in the PA 54 is input from the PA replica coefficient calculation unit 5h, and the modulated signal (x U0 ) using the coefficient w to generate a modulated signal that simulates nonlinear distortion, and outputs the signal to the interference replica generator 5d.

[0049] [How PA replica signals and interference replica signals are generated in this system] The generation of the PA replica signal and the interference replica signal in this system will be specifically described below. The PA replica generating unit 5c generates a modulated signal that simulates the nonlinear distortion of the PA 54. The modulated signal that simulates this nonlinear distortion is shown in [Equation 6].

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[0050] A feature of this system is that it generates a modulated signal that simulates the nonlinear distortion of this PA54 while adjusting the timing, and details of this will be described later. The interference replica generator 5d uses the nonlinear distortion modulation signal as a known reference signal and subtracts the interference replica signal from the received signal to generate x D +ε is input and the residual component ε is minimized to generate the interference wave replica signal shown in [Equation 7].

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[0051] The interference replica generator 5d calculates an estimated value h"^" of the channel characteristics shown in Equation (4). As explained in FIG. 2, various methods are possible for this estimation, but any method is acceptable in the present invention.

[0052] In this way, to calculate the interference wave replica signal of equation (4), it is necessary to calculate an estimated function of the nonlinear distortion characteristics and an estimated value of the transmission path characteristics. In this system, the PA replica generator 5c estimates the nonlinear distortion signal (the value of the function on the right side of equation (4)), and the interference replica generator 5d estimates the propagation path characteristics of the loop (the estimated value of the transmission path characteristics on the right side of equation (4)). By estimating the two parameters to be estimated independently in two stages in this way, it is expected that the estimation accuracy will be improved and the estimation will converge faster.

[0053] The interference wave replica signal shown on the right side of equation (4) is input to DAC5e, converted from a digital signal to an analog signal, and the interference wave (x U ) is input to the minus terminal of the subtractor 59 as a signal for removing the

[0054] As explained above, in the interference canceller of this system, even if nonlinear distortion occurs in the PA 54, the interference wave (x U ) can be cancelled with high accuracy. Interference wave (x U ) is cancelled out and the desired signal (x D ) is input to the desired wave demodulation unit 5f, and the desired wave (x D ) to achieve good communication.

[0055] [PA replica generation timing adjustment] Next, timing adjustment for PA replica generation will be described. The timing adjustment in this system is performed in two stages using a delay adjustment section (first delay adjustment section) 52 and a delay adjustment section (second delay adjustment section) 5i.

[0056] As mentioned above, the PA replica generator 5c has the function of generating a modulated signal that simulates the nonlinear distortion of the PA 54. However, in order to cancel the interference wave, it is necessary to match the input timing of the + terminal and the - terminal of the subtractor 59.

[0057] The output signal of PA 54 passes through coupler 55, transmitting antenna 56, propagation path 57, and receiving antenna 58 to reach the + terminal of subtractor 59, but the propagation time is mainly due to propagation delays in the cable and space, and is extremely short at around a few nanoseconds.

[0058] On the other hand, to generate an interference wave replica, the signal passes through PA replica generator 5c, interference replica generator 5d, and DAC 5e and reaches the minus terminal of subtractor 59. These processes are realized by digital signal processing, which requires a delay of several tens to several hundreds of nanoseconds.

[0059] Therefore, it is possible to adjust the timing by inserting an analog delay device into the output of PA54, but it is extremely difficult to delay the analog signal by tens to hundreds of nanoseconds. Even if a delay could be achieved, problems such as a decrease in power consumption would arise, making this an unrealistic solution.

[0060] Therefore, this system provides a delay adjustment unit 52 to achieve timing adjustment in the digital signal domain, which makes it easy to adjust the delay in units of sampling clock periods. Furthermore, delay adjustments of less than the sampling clock period can be performed by filter interpolation of the sampling sequence.

[0061] The delay adjustment unit 52 adjusts the delay time so that the time from the output of the modulated signal generation unit 51 to the delay adjustment unit 52, DAC 53, PA 54, coupler 55, transmitting antenna 56, propagation path 57, receiving antenna 58, and the + terminal of the subtractor 59 matches the time from the output of the modulated signal generation unit 51 to the PA replica generation unit 5c, interference replica generation unit 5d, DAC 5e, and the - terminal of the subtractor 59.

[0062] [PA replica generation method] Finally, the PA replica generation method will be explained. The PA replica signal (nonlinear distortion signal: the value of the function on the right side of Equation (4)) is generated by the PA replica coefficient calculation unit 5h and the PA replica generation unit 5c. At this time, in order to estimate the characteristics of the PA 54, the output signal from the C terminal of the coupler 55 is input to the ADC 5g and converted into a digital signal.

[0063] The nonlinear distortion signal f(x U0 ) is input to the PA replica coefficient calculation unit 5h. The other input of the PA replica coefficient calculation unit 5h is the modulated signal (x U0 ) is input as a signal shown in [Equation 8] via the delay adjustment unit 5i.

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[0064] The PA replica coefficient calculation unit 5h calculates the coefficients of a nonlinear model of the PA. The Hammerstein model is often used as a PA nonlinear model. The Hammerstein model is shown in Equation (5) of [Mathematical Expression 9].

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[0065] Here, n is the odd nth order, N is the maximum order, m is the sampling time, M is the number of filter taps, and Wn,m is the nth order, mth tap coefficient. As shown in Equation (5), nonlinear distortion occurs when the modulated signal (xU0 ) can be expressed as a linear sum of odd-numbered n-th order signals. For example, an example where N=7th order and the number of taps M=1 is given in Equation (6) of [Equation 10].

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[0066] The purpose of the PA replica coefficient calculation unit 5h is to calculate the coefficients Wn,m in formula (5) and W1 to W7 in formula (6). When the nonlinear characteristics of the PA 54 follow the Hammerstein model, if an appropriate coefficient Wn,m can be calculated, it becomes possible to faithfully reproduce the characteristics of the PA.

[0067] Furthermore, the Hammerstein model shown in Equation (5) of [Mathematical Formula 9] is known as a memoryless nonlinear model, i.e., a model in which past signals do not affect current signals, and is suitable for power amplifier models of relatively narrowband signals. On the other hand, the memory effect nonlinear model is a model in which past signals have characteristics similar to those of a memory element and affect current signals, and is suitable for power amplifier models of wideband signals. Since the present invention does not depend on the model of the power amplifier used, either a memoryless nonlinear model or a memory effect nonlinear model may be used.

[0068] The PA replica coefficient calculation unit 5h calculates the linear signal (x U0 ) and nonlinear signal f(x U0 ) to calculate the coefficient Wn,m, but in this case, f(x U0 ) is (x U0 ) passes through the delay adjustment unit 52, the DAC 53, the PA 54, the coupler 55, and the ADC 5g to reach the PA replica coefficient calculation unit 5h, so that (x U0 ) and f(x U0 ) there is a time difference. To solve this problem of time difference, the present invention employs a method of separating coefficient calculation from PA replica generation.

[0069] First, to calculate the coefficients, f(xU0 ) and (x U0 The time difference between the two is adjusted by the delay adjusting unit 5i. In order to match the timing of these signals, the delay adjustment unit 5i adjusts the timing using the same method as the delay adjustment unit 52, and outputs the delayed signal shown in [Equation 8].

[0070] The PA replica coefficient calculation unit 5h substitutes the delayed signal into Equation (7) of [Equation 11] to obtain a nonlinear distortion signal (the value of the function on the right side of Equation (4)) and f(x U0 ) to minimize the error. U0 ) is replaced with the delayed signal in [Equation 8].

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[0071] The PA replica coefficient calculation unit 5h calculates equation (7) during the internal signal processing process, but the calculation result is time-delayed in the delay adjustment unit 5i, so the timing does not match that of the interference wave in the subtractor 59, and therefore the calculation result of equation (7) cannot be used as the interference wave replica.

[0072] Therefore, the coefficients Wn,m of each order calculated by the PA replica coefficient calculation unit 5h are input to the PA replica generation unit 5c. The PA replica generator 5c performs the calculation shown in Equation (5) to generate the nonlinear distortion modulation signal shown in Equation (6). The coefficient Wn,m in Equation (5) is a coefficient calculated by the PA replica coefficient calculator 5h.

[0073] In this way, the coefficient Wn,m calculated for the time-delayed signal shown in [Equation 8] is applied to the non-delayed signal (x U0), it becomes possible to match the timing of the interference wave and the interference wave replica, making it possible to cancel the interference wave with high precision.

[0074] Here, the coefficient Wn,m used is calculated based on a time-delayed signal, but if the characteristics of PA54 change slowly over time due to temperature changes or aging, a delay of the coefficient of about several tens of nanoseconds will not degrade the estimation accuracy.

[0075] As described above, this system can accurately estimate the PA replica signal and accurately cancel the interference signal by performing appropriate timing adjustments, even in a full-duplex wireless communication environment using signals with nonlinear distortion.

[0076] [Effects of the embodiment] According to this system, the transmitting device comprises a modulated signal generating unit 51 that generates a modulated signal, a PA 54 that power amplifies the modulated signal for transmission, a transmitting antenna 56 that sends out the power-amplified signal for transmission, and a PA replica generating unit 5c that generates a PA replica signal from a portion of the output signal from the PA 54, and the receiving device comprises a receiving antenna 58 for reception, a subtractor 59 that subtracts an interference wave replica signal from the signal received from the receiving antenna 58, and an interference replica generating unit 5d that uses the PA replica signal as a reference signal to generate an interference wave replica signal so that the residual component included in the signal subtracted by the subtractor 59 is minimized.Therefore, it is possible to achieve the effect of highly accurately removing interference waves that have sneaked from the transmitting antenna of the local station to the receiving antenna of the local station. [Industrial Applicability]

[0077] The present invention is suitable for a wireless communication system capable of highly accurately removing interference waves that have leaked from a transmitting antenna of a station to a receiving antenna of the station. [Explanation of symbols]

[0078] DESCRIPTION OF SYMBOLS 1a, 5d...Interference replica generation unit, 1b, 5e...DAC (D / A converter), 1c, 5f...Desired wave demodulation unit, 5c...PA replica generation unit, 5g...ADC (A / D converter), 5h...PA replica coefficient calculation unit, 5i...Delay adjustment unit (second delay adjustment unit), 11, 51...Modulation signal generation unit, 12, 53...DAC (D / A converter), 13, 54...PA (power amplifier), 14, 56...Transmitting antenna, 15, 57...Propagation path, 16, 58...Receiving antenna, 17, 59...Subtractor, 18, 5a...LNA (low noise amplifier), 19, 5b...ADC (A / D converter), 52...Delay adjustment unit (first delay adjustment unit), 55...Coupler

Claims

1. A wireless communication system including a transmitting device and a receiving device, the transmitting device comprises a modulated signal generating unit that generates a modulated signal, a power amplifier that power-amplifies the modulated signal for transmission, a transmitting antenna that sends out the power-amplified signal for transmission, and a power amplifier replica generating unit that generates a replica signal of the power amplifier from a part of an output signal from the power amplifier; The receiving device includes a receiving antenna for reception, a subtractor that subtracts a replica signal of an interference wave from a received signal from the receiving antenna, an interference replica generation unit that uses a power amplifier replica signal generated by the power amplifier as a reference signal to generate the replica signal of the interference wave so that a residual component included in the signal subtracted by the subtractor is minimized, and a desired wave demodulation unit that demodulates the signal subtracted by the subtractor, the power amplifier replica generation unit estimates a nonlinear distortion signal included in the output signal from the power amplifier to generate a replica signal of the power amplifier; the interference replica generation unit estimates a transmission path characteristic of a loop from the transmitting antenna to the receiving antenna, and generates a replica signal of the interference wave by multiplying the reference signal by the estimated value of the transmission path characteristic.

2. A wireless communication system comprising a transmitting device and a receiving device, the transmitting device comprises a modulated signal generating unit that generates a modulated signal, a power amplifier that power-amplifies the modulated signal for transmission, a transmitting antenna that sends out the power-amplified signal for transmission, and a power amplifier replica generating unit that generates a replica signal of the power amplifier from a part of an output signal from the power amplifier; The receiving device includes a receiving antenna for reception, a subtractor that subtracts a replica signal of an interference wave from a received signal from the receiving antenna, an interference replica generation unit that uses the replica signal of the power amplifier generated by the power amplifier as a reference signal and multiplies the reference signal by an estimated value of a propagation path characteristic of feedback from the transmitting antenna to the receiving antenna to generate the replica signal of the interference wave, and at that time generates the replica signal of the interference wave so that a residual component included in the signal subtracted by the subtractor is minimized, and a desired wave demodulation unit that demodulates the signal subtracted by the subtractor, the transmitting device includes a coupler that separates a part of an output signal from the power amplifier, and a power amplifier replica coefficient calculation unit that calculates a model coefficient of a model that imitates the power amplifier based on the output signal from the coupler and the modulated signal, The wireless communication system is characterized in that the power amplifier replica generation unit generates a replica signal of the power amplifier based on the modulated signal and using the coefficient.

3. 3. The wireless communication system according to claim 1, further comprising a first delay adjustment unit for delaying the modulated signal in a stage preceding the power amplifier in order to adjust the timing of input of the received signal and the replica signal of the interference wave in the subtractor.

4. 3. The wireless communication system according to claim 2, further comprising a second delay adjustment unit that delays the input of the modulated signal in order to adjust the input timing of the modulated signal in the power amplifier replica coefficient calculation unit and the output signal from the coupler.

5. 5. The wireless communication system according to claim 2, wherein the power amplifier replica coefficient calculation unit calculates model coefficients of a model that imitates the power amplifier by comparing a linear signal of the modulated signal with a nonlinear signal of the output signal from the coupler.

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