Wireless communication method, wireless communication system, transmitting device, and receiving device

Abstract

This transmission device comprises an antenna, a phase offset application unit, an OAM mode generation unit, a radio processing unit, an estimation unit, and a phase offset amount calculation unit. The antenna transmits OAM multiplex signals from a plurality of antenna elements arranged in a circle. The phase offset application unit applies phase offset amounts to signals to be transmitted using respective OAM modes. The OAM mode generation unit generates, from signals to which the phase offset amounts have been applied, signals that are of the respective OAM modes and are to be transmitted from the antenna elements, and multiplexes the resulting signals for the respective antenna elements. The radio processing unit converts the multiplexed signals for the respective antenna elements into radio signals, and transmits the resulting signals from the corresponding antenna elements. The estimation unit estimates the characteristics of the radio processing unit on the basis of the multiplexed radio signals. The phase offset amount calculation unit calculates the phase offset amounts in accordance with the characteristics of the radio processing unit.

Description

[Technical field]

[0001] The present invention relates to a wireless communication method, a wireless communication system, a transmitting device, and a receiving device. [Background technology]

[0002] In recent years, in order to improve communication capacity, spatial multiplexing transmission technology of wireless signals using orbital angular momentum (OAM) has been studied (see, for example, Non-Patent Document 1). Electromagnetic waves with OAM have equiphase surfaces distributed in a spiral shape along the propagation direction centered on the propagation axis. Electromagnetic waves with different OAM modes and propagating in the same direction have spatial phase distributions that are orthogonal in the direction of the rotation axis. Therefore, it is possible to spatially multiplex the signals by separating the signals of each OAM mode modulated with different signal sequences at the receiving device.

[0003] This OAM multiplexed transmission can be realized by generating, multiplexing, and transmitting multiple OAM modes using a uniform circular array (UCA) in which multiple antenna elements are arranged in a circle at equal intervals (see, for example, Non-Patent Document 2). For example, a discrete Fourier transform (DFT) matrix and an inverse discrete Fourier transform (IDFT) matrix are used to generate and separate the signals of the multiple OAM modes. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] J. Wang et. al., "Terabit free-space data transmission employing orbital angular momentum multiplexing," Nature Photonics, vol.6, pp.488-496, July 2012. [Non-Patent Document 2] Y. Yan, et. al., "High-capacity millimetre-wave communications with orbital angular momentum multiplexing," Nature Communications, vol.5, DOI: 10.1038 / ncomms5876, Sept. 2014. Summary of the Invention [Problem to be solved by the invention]

[0005] Generally, RF (Radio Frequency) elements such as transmitting amplifiers and mixers have variations in input limit (P1dB: output power at 1dB gain compression) and gain characteristics due to manufacturing errors. In particular, in MIMO multiplexing transmission such as OAM multiplexing transmission, RF elements with different characteristics may be used for each antenna in a system having multiple RF systems. In such cases, the transmission power is generally limited to match the element with the lowest P1dB, which leads to a reduction in the transmission power.

[0006] In view of the above circumstances, an object of the present invention is to provide a wireless communication method, a wireless communication system, a transmitting device, and a receiving device that can improve the transmission power in OAM multiplexing transmission. [Means for solving the problem]

[0007] A wireless communication method according to one aspect of the present invention includes a phase offset applying step in which a transmitting device having an antenna for transmitting an OAM (Orbital Angular Momentum) multiplexed signal by a plurality of antenna elements arranged in a circle applies a phase offset amount to a signal transmitted in each OAM mode; an OAM mode generating step in which the transmitting device generates a signal of each OAM mode to be transmitted by each of the antenna elements from the signal to which the phase offset amount has been applied, and generates a multiplexed signal by multiplexing the generated signals of each OAM mode for each of the antenna elements; a wireless transmitting step in which the transmitting device converts the multiplexed signal for each of the antenna elements into a wireless multiplexed signal by a wireless processing unit, and transmits the wireless multiplexed signal from the corresponding antenna element; and a receiving step in which a receiving device receives the wireless multiplexed signal transmitted from each of the plurality of antenna elements in the wireless transmitting step, and converts a frequency of the received multiplexed signal. The method includes a separation step of separating the multiplexed signal frequency-converted in the receiving step into signals of each OAM mode, a received signal processing step in which the receiving device removes the phase offset amount added in the phase offset adding step from the signals of the OAM mode separated in the separation step, an estimation step in which the transmitting device estimates characteristics of the radio processing unit based on the radio multiplexed signal converted in the radio transmitting step, or an estimation step in which the receiving device estimates characteristics of the radio processing unit based on the multiplexed signal frequency-converted in the receiving step, and a calculation step in which the transmitting device calculates a phase offset amount to be added to the signals transmitted in each OAM mode in the phase offset adding step in accordance with the characteristics of the radio processing unit estimated in the estimation step.

[0008] A wireless communication system according to one aspect of the present invention includes a transmitting device and a receiving device, the transmitting device including an antenna for transmitting an OAM (Orbital Angular Momentum) multiplexed signal by a plurality of antenna elements arranged in a circle, a phase offset applying unit for applying a phase offset amount to a signal transmitted by each OAM mode, an OAM mode generating unit for generating a signal of each OAM mode to be transmitted by each of the antenna elements from the signal to which the phase offset amount has been applied and for generating a multiplexed signal by multiplexing the generated signals of each OAM mode for each of the antenna elements, a wireless processing unit for converting the multiplexed signal for each of the antenna elements into a wireless multiplexed signal and transmitting the wireless multiplexed signal from the corresponding antenna element, and a phase offset calculation unit for calculating a phase offset amount to be applied by the phase offset applying unit to the signal transmitted by each OAM mode in accordance with a characteristic of the wireless processing unit. and a phase offset calculation unit, wherein the receiving device comprises a receiving unit that receives the wireless multiplexed signal transmitted from each of the plurality of antenna elements and converts a frequency of the received multiplexed signal, an OAM mode separation unit that separates the multiplexed signal frequency-converted by the receiving unit into signals of each OAM mode, and a received signal processing unit that removes the phase offset amount assigned by the phase offset assigning unit from the signals of the OAM mode separated by the OAM mode separation unit, and the wireless communication system comprises an estimation unit that estimates characteristics of the wireless processing unit based on the wireless multiplexed signal converted by the wireless processing unit, or estimates characteristics of the wireless processing unit based on the multiplexed signal frequency-converted in the receiving unit.

[0009] A transmitting device according to one embodiment of the present invention includes an antenna that transmits an OAM (Orbital Angular Momentum) multiplexed signal using a plurality of antenna elements arranged in a circle; a phase offset assigning unit that assigns a phase offset to the signal transmitted in each OAM mode; an OAM mode generating unit that generates a signal for each OAM mode to be transmitted by each of the antenna elements from the signal to which the phase offset has been assigned, and generates a multiplexed signal by multiplexing the generated signals for each OAM mode for each of the antenna elements; a wireless processing unit that converts the multiplexed signal for each of the antenna elements into a wireless multiplexed signal and transmits the wireless multiplexed signal from the corresponding antenna element; an estimation unit that estimates characteristics of the wireless processing unit based on the wireless multiplexed signal converted by the wireless processing unit; and a phase offset calculation unit that calculates a phase offset to be assigned to the signal transmitted in each OAM mode by the phase offset assigning unit in accordance with the characteristics of the wireless processing unit estimated by the estimation unit.

[0010] A receiving device of one embodiment of the present invention includes a receiving unit that receives a multiplexed signal in which signals of each OAM mode are multiplexed, the multiplexed signal being transmitted from each of a plurality of antenna elements arranged in a circle having an antenna of a transmitting device that transmits an OAM (Orbital Angular Momentum) multiplexed signal, and converts the frequency of the multiplexed signal; an OAM mode separation unit that separates the multiplexed signal frequency-converted by the receiving unit into signals of each OAM mode; a received signal processing unit that removes a phase offset amount imparted by the transmitting device from the OAM mode signal separated by the OAM mode separation unit; an estimation unit that estimates characteristics of a frequency conversion unit that converted the multiplexed signal into the multiplexed signal of a radio frequency in the transmitting device based on the multiplexed signal frequency-converted by the receiving unit; and a notification unit that notifies the transmitting device of the characteristics estimated by the estimation unit. Effect of the Invention

[0011] According to the present invention, it is possible to improve the transmission power in OAM multiplexing transmission. [Brief description of the drawings]

[0012] [Figure 1] FIG. 13 is a diagram illustrating an example of phase settings of a UCA for generating an OAM mode signal. [Diagram 2] 1 is a configuration diagram of a wireless communication system according to an embodiment of the present invention. [Diagram 3] FIG. 2 is a diagram illustrating an example of the configuration of a transmitting device in the embodiment. [Figure 4] 11 is a diagram illustrating an example of a connection configuration from an OAM mode generating device of a transmitting device to a UCA in the embodiment. FIG. [Diagram 5] 2 is a diagram illustrating an example of a functional configuration of a transmission control device in the embodiment. FIG. [Figure 6] FIG. 2 is a diagram illustrating an example of a functional configuration of a phase offset calculation device in the embodiment. [Figure 7] FIG. 2 is a diagram illustrating an example of a functional configuration of an estimation device in the embodiment. [Figure 8] FIG. 2 is a diagram illustrating an example of the configuration of a receiving device in the embodiment. [Figure 9] FIG. 2 is a diagram illustrating an example of a functional configuration of an estimation device in the embodiment. [Figure 10] FIG. 4 is a sequence diagram showing the processing of the wireless communication system in the embodiment. [Figure 11] FIG. 13 is a diagram showing an example of a received constellation that has been subjected to nonlinear distortion in the embodiment. [Figure 12] FIG. 4 is a flow diagram showing an algorithm for estimating nonlinear distortion in the embodiment. [Figure 13] FIG. 4 is a flowchart showing the processing of a transmitting device in the embodiment. [Figure 14] FIG. 2 is a diagram illustrating the hardware configuration of a transmitting device and a receiving device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the embodiment to which the present invention is applied is not limited to the following embodiment. This embodiment relates to a technology for spatially multiplexing transmission of wireless signals using Orbital Angular Momentum (OAM) of electromagnetic waves.

[0014] In this embodiment, the transmission power is improved by utilizing the difference in the PAPR (Peak-to-average power ratio) of the transmission signal from each antenna element in OAM multiplexing transmission. Therefore, the transmitting device of this embodiment assigns a signal with a low PAPR to an antenna element with a low P1dB. This reduces the input margin and improves the transmission power.

[0015] FIG. 1 is a diagram showing an example of phase settings of a UCA for generating signals in OAM modes. FIGS. 1(a) to 1(e) respectively show phase settings of signals transmitted from each UCA for a transmitting device to generate signals in OAM modes 0 to 4. OAM modes are also simply referred to as modes. Circles arranged on the circumference of a dotted line indicate each antenna element of a UCA. In the diagram, an example is shown in which the number of antenna elements M is 8.

[0016] The transmitting device generates an OAM mode signal by giving a phase difference according to a DFT transformation matrix to the signal supplied to each antenna element of the UCA. The phase difference given to the signal transmitted from the antenna element is shown near each circle representing an antenna element. Specifically, the phase difference given to each antenna element is set so that the phase of the OAM mode n signal rotates n times. The top antenna element on the circle is the first. For example, as shown in FIG. 1(c), when transmitting an OAM mode 2 signal using an 8-element UCA, the phase differences given to the first to eighth antenna elements are 0 degrees, 90 degrees, 180 degrees, 270 degrees, 0 degrees, 90 degrees, 180 degrees, and 270 degrees clockwise. Also, an OAM mode-2 signal is generated by giving a phase difference to each antenna element in the opposite direction to OAM mode 2. The number of multiplex modes can be up to the same number as the number of antenna elements, but it may be less than the number of antenna elements.

[0017] In order for the receiving device to separate the received OAM multiplexed signal, the phase of each antenna element of the UCA of the receiving device is set to rotate in the opposite direction to the phase of the transmitting device.

[0018] Fig. 2 is a configuration diagram of a wireless communication system 1 in an embodiment of the present invention. As shown in Fig. 2, the wireless communication system 1 includes a wireless transmission device 11 and a wireless transmission device 12. The wireless transmission device 11 and the wireless transmission device 12 are installed opposite each other. In this embodiment, it is assumed that the wireless transmission devices 11 and 12 are stationary base stations. However, this assumption is merely an example. In other words, one or both of the wireless transmission devices 11 and 12 may be mobile.

[0019] The wireless transmission device 11 and the wireless transmission device 12 each have a transmitting device 100 and a receiving device 300. The transmitting device 100 and the receiving device 300 are wireless communication devices that perform wireless communication. The transmitting device 100 has a function of transmitting an OAM multiplexed signal. The transmitting device 100 includes an OAM mode generating device and a UCA. The transmitting device 100 transmits an OAM multiplexed signal in which one or more different OAM mode signals are multiplexed from the UCA. The receiving device 300 has a function of receiving the OAM multiplexed signal. The receiving device 300 includes an OAM mode separating device and a UCA. The receiving device 300 receives an OAM multiplexed signal in which one or more OAM mode signals are multiplexed and transmitted from the opposing transmitting device 100, and separates each OAM mode signal from the received OAM multiplexed signal.

[0020] Next, an example of the device configuration of the transmitting device 100 and the receiving device 300 will be described. First, the transmitting device 100 will be described. Fig. 3 is a diagram showing an example of the configuration of the transmitting device 100. As shown in Fig. 3, the transmitting device 100 has a transmission control device 110, a signal processing device 120, a phase offset calculation device 130, a phase offset notification device 140, a phase offset giving device 150, an OAM mode generation device 160, an RF (Radio Frequency) chain 180, a UCA 190, an estimated information acquisition device 210, and an estimation device 220.

[0021] The transmission control device 110 specifies parameter values ​​such as the number of mode multiplexing, transmission OAM mode, modulation multi-level number, and symbol rate of the OAM multiplexed signal to be transmitted. The number of mode multiplexing is 1 or more. The modulation method of the OAM multiplexed signal is determined by the values ​​of these parameters. The transmission control device 110 notifies the signal processing device 120, phase offset calculation device 130, and OAM mode generation device 160 of the specified parameter values.

[0022] The signal processing device 120 generates a digital signal to be transmitted on a carrier wave based on the input data and the parameter values ​​notified by the transmission control device 110. The signal processing device 120 converts the generated digital signal into an analog signal, and converts the frequency of the analog signal into the frequency band of the carrier wave. The signal processing device 120 inputs the frequency-converted signal to the phase offset adding device 150.

[0023] Phase offset calculation device 130 calculates the phase offset amount for each OAM mode based on the transmission OAM mode and the number of mode multiplexing notified from transmission control device 110 and information on the nonlinear distortion amount of each antenna element estimated by receiving device 300 or estimation device 220. The phase offset amount of an OAM mode is the phase offset amount to be given to a signal transmitted in that OAM mode. Phase offset calculation device 130 calculates the phase offset for each OAM mode so as to assign a signal with a low PAPR to an antenna element with a high nonlinear distortion. Phase offset calculation device 130 inputs information on the calculated phase offset amount for each OAM mode to phase offset notification device 140 and phase offset granting device 150.

[0024] Phase offset notification device 140 receives information on the phase offset amount of each OAM mode from phase offset calculation device 130. Phase offset notification device 140 generates phase offset information indicating the input phase offset amount of each OAM mode. Phase offset notification device 140 converts the generated phase offset information into an appropriate form for notifying receiving device 300, and then notifies receiving device 300, for example, via a backbone line. Receiving device 300 may restore the signal point of the received signal using the phase offset information received from phase offset notification device 140, or receiving device 300 may estimate and compensate the phase offset amount. In the latter case, transmitting device 100 may or may not have phase offset notification device 140.

[0025] The phase offset adding device 150 inputs information on the phase offset amount of each OAM mode from the phase offset calculation device 130. The phase offset adding device 150 adds the phase offset amount of the OAM mode used for transmitting the signal input from the signal processing device 120 to the signal. For example, when a signal in mode 2 is transmitted by an eight-element UCA as shown in FIG. 1(b), by adding a phase offset amount of 90 degrees, the phase differences given to the first to eighth antenna elements are 90 degrees, 180 degrees, 270 degrees, 0 degrees, 90 degrees, 180 degrees, 270 degrees, and 0 degrees clockwise. The phase offset adding device 150 inputs the signal to which the phase offset amount of the OAM mode used for transmission has been added to the OAM mode generation device 160.

[0026] OAM mode generating device 160 is an analog circuit or a digital signal processing device that applies a DFT transformation matrix. OAM mode generating device 160 applies a DFT transformation matrix to the signal input from phase offset adding device 150, thereby generating a signal in a transmission OAM mode specified by transmission control device 110. OAM mode generating device 160 multiplexes the generated signals in one or more OAM modes and inputs the multiplexed signals to preamble adding device 170.

[0027] The preamble assigning device 170 assigns an orthogonal preamble to an OAM multiplexed signal transmitted from each antenna element and inputs the signal to the RF chain 180. The RF chain 180 inputs the OAM multiplexed signal to which the orthogonal preamble has been assigned from the preamble assigning device 170. The RF chain 180 frequency-converts and amplifies the OAM multiplexed signal, and then inputs the signal to the UCA 190. The UCA 190 is an antenna in which M antenna elements are arranged in a circle. The UCA 190 transmits and receives the OAM multiplexed signal. Hereinafter, a signal transmitted or transmitted by an antenna element of the UCA 190 will be referred to as an antenna element signal.

[0028] The estimated information acquisition device 210 acquires information on the amount of nonlinear distortion of each antenna element of the UCA 190 from the receiving device 300. The amount of nonlinear distortion indicates the magnitude of P1 dB. The amount of nonlinear distortion in the signal of the antenna element of the UCA 190 is described as the amount of nonlinear distortion of the antenna element. The estimated information acquisition device 210 notifies the phase offset calculation device 130 of the acquired information on the amount of nonlinear distortion of each antenna element. The notified information may indicate the antenna element with the smallest amount of nonlinear distortion.

[0029] The estimation device 220 receives the output from the RF chain 180 and estimates the amount of nonlinear distortion of each antenna element based on the orthogonal preamble components of the received signal. The estimation device 220 notifies the phase offset calculation device 130 of the acquired information on the amount of nonlinear distortion of each antenna element. The notified information may represent the antenna element with the smallest amount of nonlinear distortion.

[0030] 4 is a diagram showing an example of a connection configuration from OAM mode generating device 160 to UCA 190 in transmitting device 100. UCA 190 is an antenna in which M antenna elements 191 are arranged on a circle. The M antenna elements 191 are respectively referred to as antenna elements 191-1 to 191-M.

[0031] OAM mode generation device 160 has output ports #1 to #M. OAM mode generation device 160 applies a DFT transformation matrix according to the mode to each signal transmitted in modes 0 to N, and generates a transmission signal to be transmitted from each of antenna elements 191-1 to 191-M. The DFT transformation matrix is ​​an OAM mode generation matrix for generating a signal in a transmission OAM mode. For each antenna element 191-m (m is an integer between 1 and M), OAM mode generation device 160 multiplexes the signals of each mode to be transmitted from antenna element 191-m, and outputs the multiplexed signal #m from output port #m.

[0032] Preamble adding device 170 has preamble adding units 171-1 to 171-M. Preamble adding unit 171-m inputs signal #m output from output port #m of OAM mode generating device 160. Preamble adding unit 171-m inserts a preamble into signal #m. Preamble adding unit 171-m outputs signal #m with the preamble inserted.

[0033] The RF chain 180 has RF chains #1 to #M. RF elements such as a transmission amplifier and a mixer are used in each of the RF chains #1 to #M. The RF chain #m inputs a signal #m from the preamble adding unit 171-m of the preamble adding device 170. The RF chain #m converts the frequency of the signal #m to a radio frequency using the RF element, amplifies the signal, and outputs the signal to the antenna element 191-m, which is the m-th antenna element 191. The UCA 190 transmits the signals #1 to #M input from the RF chain 180 as radio waves from the antenna elements 191-1 to 191-M, respectively.

[0034] As an example, a process will be described when signals to be transmitted in mode 0 and mode 1 are input to the OAM mode generating device 160. In this example, antenna element 191-1 of UCA 190 is the reference (phase 0 degrees). The OAM mode generating device 160 multiplexes two signals having the following phases and outputs the combined signal to output port #m corresponding to input port #m of RF chain 180.

[0035] Antenna element #m[((m-1) / M×360×0) degrees, (m-1) / M×360×1 degrees)]

[0036] Antenna element #m[x,y] means that of the signals multiplexed and output from output port #m corresponding to antenna element 191-m, a phase of x degrees is given to the mode 0 signal and a phase of y degrees is given to the mode 1 signal.

[0037] 5 is a diagram showing an example of a functional configuration of the transmission control device 110. The transmission control device 110 includes a communication performance acquisition unit 111, a transmission OAM mode determination unit 112, a multiplex number determination unit 113, and a transmission signal parameter determination unit 114.

[0038] The communication performance acquisition unit 111 is a device that acquires communication characteristic information. The communication characteristic information indicates characteristics of the communication between the transmitting device 100 and the receiving device 300. The characteristics indicated by the communication characteristic information include, for example, a transmission / reception distance, a received signal power to interference noise power ratio (SINR), inter-mode interference, etc. The transmission / reception distance is the distance between the transmitting device 100 and the receiving device 300.

[0039] The transmission OAM mode determination unit 112 determines the OAM mode to be used for transmission based on the communication characteristic information. The multiplex number determination unit 113 determines, for example, the mode multiplex number and the modulation multi-level number based on the communication characteristic information. The transmission signal parameter determination unit 114 determines the value of a transmission signal parameter such as a coding rate based on the communication characteristic information. The transmission OAM mode determination unit 112, the multiplex number determination unit 113, and the transmission signal parameter determination unit 114 use, for example, the distance between the transmitter and the receiver and the reception SINR as the communication characteristic information. Information on the values ​​of the transmission signal parameters such as the determined OAM mode, the mode multiplex number, the modulation multi-level number, and the coding rate are input to the signal processing device 120, the phase offset calculation device 130, and the OAM mode generation device 160.

[0040] In FIG. 5, as an example, the processing is performed in the order of communication performance acquisition section 111, transmission OAM mode determination section 112, and multiplex number determination section 113, but the order may be changed.

[0041] 6 is a diagram showing an example of a functional configuration of phase offset calculation device 130. Phase offset calculation device 130 has communication parameter acquisition section 131, PAPR information holding section 132, and phase offset determination section 133.

[0042] The communication parameter acquisition unit 131 acquires information on parameters such as the modulation multi-level number, the mode multiplexing number, and the transmission OAM mode notified from the transmission control device 110, and notifies the phase offset determination unit 133 of the information on these parameters.

[0043] The PAPR information storage unit 132 stores PAPR characteristic information. The PAPR characteristic information is calculated based on parameter values ​​such as the modulation level, the mode multiplexing level, and the OAM mode. The PAPR characteristic information indicates the correspondence between the phase offset amount given to the signal of each OAM mode to be multiplexed and the PAPR characteristic of each antenna element 191. The PAPR characteristic is calculated in advance using simulation or theoretical calculation. The PAPR information storage unit 132 may calculate the PAPR characteristic each time. In this embodiment, the PAPR information storage unit 132 stores a lookup table (LUT) for each modulation method as the PAPR information. The modulation method indicates the modulation level, the mode multiplexing level, and the OAM mode to be mode multiplexed. The lookup table indicates the relationship between the identification of an antenna element and the phase offset amount of each OAM mode when the PAPR of the antenna element is the lowest.

[0044] For example, in QAM (Quadrature Amplitude Modulation), when the phase offset is 90 degrees, the position of the constellation is the same before and after the phase offset is applied. Therefore, a phase offset smaller than 90 degrees is used. On the other hand, the phase offset that can be applied varies depending on the number of antenna elements M. That is, any value less than 90 degrees is used as the phase offset that can be applied. Therefore, although the combination of phase offsets is limited by the memory capacity of the lookup table, it is generally possible to implement any number of combinations. For each modulation method, the PAPR of each antenna element is calculated for all combinations when an applicable phase offset is applied to each multiplexed OAM mode. Then, for each modulation method, the combination of phase offsets of each OAM mode with the lowest PAPR of each antenna element is selected and set in the lookup table.

[0045] The phase offset determination unit 133 selects the antenna element 191 having the largest estimated value of the amount of nonlinear distortion based on the information of the amount of nonlinear distortion of each antenna element 191 notified from the estimation information acquisition device 210 or the estimation device 220. Furthermore, the phase offset determination unit 133 refers to the PAPR information holding unit 132 to obtain the relationship between the amount of phase offset of each OAM mode for the current modulation method and the PAPR of each antenna element 191. The phase offset determination unit 133 determines the phase offset of each OAM mode so as to assign a signal with a PAPR lower than a predetermined value to the selected antenna element 191. The PAPR lower than a predetermined value is, for example, the lowest PAPR.

[0046] 7 is a diagram showing an example of a functional configuration of the estimation device 220. The estimation device 220 includes a transmitting antenna output acquisition unit 221, a constellation extraction unit 222, an EVM (Error Vector Magnitude) calculation unit 223, and an EVM comparison unit 224.

[0047] The transmitting antenna output acquisition unit 221 extracts a frame corresponding to a preamble from the signal input to each antenna element 191. Note that the preamble is modulated by a high-order multi-level modulation such as 16QAM. The constellation extraction unit 222 classifies the signal points based on the voltage of the preamble included in the frame extracted by the transmitting antenna output acquisition unit 221. The EVM calculation unit 223 calculates the EVM of the signal points for each antenna element 191. The EVM comparison unit 224 compares the EVM of each signal point, and regards the difference as the amount of nonlinear distortion. The EVM comparison unit 224 compares the amount of nonlinear distortion of each antenna element, and notifies the phase offset calculation device 130 of the antenna element 191 with the largest amount of nonlinear distortion as the antenna element 191 with the lowest P1dB.

[0048] Next, a description will be given of the receiving device 300. Fig. 8 is a diagram showing an example of a functional configuration of the receiving device 300. The receiving device 300 includes a UCA 310, an RF chain 320, an estimation device 330, an estimation result notification device 340, an OAM mode separation device 350, a received signal processing device 360, a demodulator 370, and a phase offset acquisition device 380.

[0049] The UCA 310 receives radio waves transmitted from the transmitting device 100, and inputs the received radio wave signal to the RF chain 320. The RF chain 320 performs frequency conversion and amplification of the signal input from the UCA 310, and inputs the signal to the OAM mode separation device 350 via the estimation device 330.

[0050] The estimation device 330 separates the orthogonal preambles inserted for each antenna element 191, and estimates the amount of nonlinear distortion of the signal transmitted by each antenna element 191. For example, the estimation device 330 performs the estimation using the QAM-modulated orthogonal preambles. The estimation device 330 inputs the signal input from the RF chain 320 to the OAM mode separation device 350 as is.

[0051] The estimation result notifying device 340 outputs information on the amount of nonlinear distortion of the signal transmitted by each antenna element 191 estimated by the estimation device 330 to the transmitting device 100 via wireless or a backbone line. The information on the amount of nonlinear distortion may represent the antenna element 191 with the smallest amount of nonlinear distortion.

[0052] The OAM mode separation device 350 is an analog circuit or a digital signal processing device that applies an IDFT transformation matrix. The OAM mode separation device 350 separates the signal input from the estimation device 330 into signals transmitted in each OAM mode, and inputs the separated signals to the reception signal processing device 360.

[0053] The reception signal processing device 360 ​​receives the signal transmitted in each OAM mode from the OAM mode separation device 350. The reception signal processing device 360 ​​also receives information on the phase offset amount of each OAM mode from the phase offset acquisition device 380. The reception signal processing device 360 ​​removes the phase offset of the phase offset amount of the OAM mode from the signal transmitted in each OAM mode. The reception signal processing device 360 ​​outputs the signal in each OAM mode from which the phase offset has been removed to the demodulator 370. The demodulator 370 demodulates the signal input from the reception signal processing device 360.

[0054] Phase offset acquisition device 380 receives phase offset information notified from phase offset notification device 140 of transmission device 100. The phase offset information indicates the phase offset amount of each OAM mode. Phase offset acquisition device 380 notifies reception signal processing device 360 ​​of information on the phase offset amount of each OAM mode indicated by the phase offset information.

[0055] 9 shows an example of the configuration of the estimation device 330. The estimation device 330 includes a preamble acquisition unit 331, a constellation extraction unit 332, an EVM calculation unit 333, and an EVM comparison unit 334.

[0056] The preamble acquisition unit 331 receives the OAM multiplexed signal received by each antenna element of the UCA 310 and frequency-converted and amplified by the RF chain 320. The preamble acquisition unit 331 extracts a portion corresponding to a preamble from the OAM multiplexed signal received by each antenna element of the UCA 310.

[0057] The constellation extraction unit 332 identifies the antenna element 191 of the UCA 190 used for transmission, based on the preamble included in the portion acquired by the preamble acquisition unit 331. Furthermore, the constellation extraction unit 332 classifies the signal points based on the voltage of the preamble.

[0058] The EVM calculation unit 333 calculates the EVM of the signal point for each antenna element 191. The EVM comparison unit 334 compares the EVM of each signal point for each antenna element 191, and regards the difference as the amount of nonlinear distortion. The EVM comparison unit 334 compares the amount of nonlinear distortion of each antenna element 191, and notifies the transmitting device 100 via the estimation result notification device 340 of the antenna element 191 having the largest amount of nonlinear distortion as the antenna element 191 having the lowest P1dB.

[0059] Next, a description will be given of the processing of the wireless communication system 1. In the wireless communication system 1, there are processing that uses feedback of the amount of nonlinear distortion from the receiving device 300, which the transmitting device 100 faces, and processing that does not use the feedback. First, a description will be given of the processing that uses feedback from the receiving device 300.

[0060] 10 is a sequence diagram showing the processing of the transmitting device 100 of the wireless transmission device 11 and the receiving device 300 of the wireless transmission device 12 in the wireless communication system 1. The transmission control device 110 of the transmitting device 100 determines the parameter values ​​such as the mode multiplexing number, the transmission OAM mode, the modulation multi-level number, and the symbol rate. The signal processing device 120 generates a signal to be transmitted in each transmission OAM mode according to the determined parameter values. The phase offset determination unit 133 of the phase offset calculation device 130 determines the phase offset amount of each transmission OAM mode as an initial value to be 0, that is, no phase offset (step S11). The phase offset adding device 150 outputs the signal input from the signal processing device 120 to the OAM mode generating device 160 as it is.

[0061] OAM mode generation device 160 converts signals to be transmitted in each transmission OAM mode into OAM mode signals to be output from M antenna elements 191. OAM mode generation device 160 multiplexes the signals in each OAM mode for each antenna element 191 to generate signals #1 to #M to be transmitted from antenna elements 191-1 to 191-M, respectively. Preamble addition device 170 adds preambles to signals #1 to #M. Here, OAM mode generation device 160 may insert a preamble after performing OAM multiplexing by digital processing, or may insert a preamble obtained by multiplying an inverse matrix of a matrix used for OAM multiplexing before OAM multiplexing.

[0062] Let M be the number of antennas, L be the number of modes, a = [a_0, a_1, ..., a_M-1] be the M independent preamble sequences, and D be the DFT transformation matrix. The preamble b inserted into the signal of each OAM mode is b = D -1 It is expressed as a = [b_0, b_1, ..., b_L-1]. For a, a high-order modulation method of 16QAM or higher is used.

[0063] RF chains #1 to #M of RF chain 180 respectively frequency-convert and amplify signals #1 to #M to which preambles have been added. UCA 190 transmits signals #1 to #M from antenna elements 191-1 to 191-M, respectively (step S12).

[0064] The UCA 310 of the receiving device 300 receives the OAM multiplexed signal transmitted by the transmitting device 100. The RF chain 320 performs down-conversion and amplification of the signals #1 to #M received by each of the M antenna elements of the UCA 310. The estimation device 330 estimates the amount of nonlinear distortion of each antenna element 191 using the preamble set in the signals #1 to #M (step S13). The estimation result notification device 340 notifies the transmitting device 100 of nonlinear distortion information indicating the estimation result in step S13 (step S14). The estimation information acquisition device 210 of the transmitting device 100 acquires the nonlinear distortion information notified from the receiving device 300.

[0065] The estimation information acquisition device 210 of the transmitting device 100 inputs the nonlinear distortion information to the phase offset calculation device 130. The phase offset determination unit 133 determines the modulation method based on the parameter values ​​such as the mode multiplexing number, the transmission OAM mode, the modulation multi-level number, and the symbol rate acquired by the communication parameter acquisition unit 131. The phase offset determination unit 133 specifies a lookup table stored in the PAPR information holding unit 132 corresponding to the modulation method. The phase offset determination unit 133 acquires information on the antenna element 191 having the smallest nonlinear distortion based on the nonlinear distortion information. The phase offset determination unit 133 reads out the phase offset amount of each OAM mode set in correspondence with the antenna element 191 having the smallest nonlinear distortion from the specified lookup table (step S15). The phase offset determination unit 133 outputs the read information on the phase offset amount of each OAM mode to the phase offset granting device 150.

[0066] The phase offset adding device 150 adds a phase offset amount of the OAM mode used for transmitting the signal to the signal input from the signal processing device 120. The OAM mode generating device 160 converts each signal to which a phase offset amount according to the OAM mode used for transmission is added, into a signal of the OAM mode to be output from each of the M antenna elements 191. The OAM mode generating device 160 multiplexes the signal of each OAM mode for each antenna element 191 to generate signals #1 to #M to be transmitted from each of the antenna elements 191-1 to 191-M. The preamble adding device 170, the RF chain 180, and the UAC 190 of the transmitting device 100 perform the same process as in step S12 to transmit the OAM multiplexed signal (step S16). The UCA 310 of the receiving device 300 receives the OAM multiplexed signal transmitted from the transmitting device 100.

[0067] In parallel with step S16, phase offset notification device 140 of transmitting device 100 notifies receiving device 300 of phase offset information indicating the phase offset amount added to the signal of each OAM mode (step S17). Phase offset acquisition device 380 of receiving device 300 outputs the phase offset information received from transmitting device 100 to received signal processing device 360.

[0068] The reception signal processing device 360 ​​of the receiving device 300 receives the signals transmitted in each OAM mode from the OAM mode separation device 350. The reception signal processing device 360 ​​also acquires the phase offset amount of each OMA mode from the phase offset information. The reception signal processing device 360 ​​removes from each input signal the offset of the phase offset amount of the OAM mode used to transmit that signal (step S18). The demodulator 370 demodulates the signal from which the phase offset has been removed (step S19). In parallel with step S19, the receiving device 300 may repeat the processes from step S13.

[0069] The wireless communication system 1 may perform the processes of steps S12 to S18 only once at the time of initial connection, or may repeat the processes multiple times at appropriate timing in order to respond to changes in propagation conditions.

[0070] Next, the detailed process of the estimation device 330 in step S13 of Fig. 10 will be described. Fig. 11 shows an example of a constellation of a 16QAM signal subjected to nonlinear distortion. As shown in Fig. 11, the nonlinear distortion caused by the RF chain 180 has a large effect on the outer signal points P1 to P4, which have a high voltage. Therefore, the estimation device 330 compares the average EVM of the outer signal points P1 to P4 with the average EVM of the inner signal points Q1 to Q4, and determines the difference as the amount of nonlinear distortion. A large amount of nonlinear distortion indicates a low P1dB. In other words, the amount of nonlinear distortion indicates the relative magnitude of P1dB. The average EVM is the mean square error normalized by the average power of the signal. The signal points P1 to P4 are collectively referred to as signal points P, and the signal points Q1 to Q4 are collectively referred to as signal points Q.

[0071] FIG. 12 is a flowchart showing an algorithm for estimating the amount of non-linear distortion in the estimation device 330. The preamble acquisition unit 331 of the non-linear distortion estimation device 330 inputs the OAM multiplexed signal received by each antenna element of the UCA 310 from the RF chain 320, and extracts a frame corresponding to the preamble b. The constellation extraction unit 332 identifies the antenna element 191 that transmitted the signal from which the preamble was obtained, based on the preamble b of the extracted frame. The constellation extraction unit 332 normalizes the constellation of the preamble b for each antenna element 191, and classifies it into an outer signal point P and an inner signal point Q based on the voltage of the signal points of the normalized preamble b (step S31).

[0072] Let the n-th (n is an integer greater than or equal to 1) complex received signal be z[n]=x[n]+jy[n]. j represents a complex number. As shown in FIG. 11, the constellation extraction unit 332 sets the signal point n where |x[n]|>A and |y[n]|>A as the outer signal point P. The signal point P is classified into signal points P1, P2, P3, and P4 according to the combination of the signs of x[n] and y[n]. Also, as shown in FIG. 12, the constellation extraction unit 332 sets the signal point n where |x[n]|<A and |y[n]|<A as the inner signal point Q. The signal point Q is also classified into signal points Q1, Q2, Q3, and Q4 according to the combination of the signs of x[n] and y[n].

[0073] The EVM calculation unit 333 of the estimation device 330 obtains the average EVM of the outer signal point P and the average EVM of the inner signal point Q for each antenna element 191 (step S32). The EVM calculation unit 333 calculates, for example, the average error from the reference of each signal point as the average EVM, based on the original signal point shared in advance between the transmission device 100 and the reception device 300 using the preamble of the OAM multiplexed signal. The reference is different for each classification of the signal points P1, P2, P3, P4, Q1, Q2, Q3, and Q4.

[0074] The EVM comparison unit 334 compares the average EVM of the outer signal point P with the average EVM of the inner signal point Q, and determines the difference between them as the amount of nonlinear distortion (step S33). The EVM comparison unit 334 outputs nonlinear distortion information indicating the amount of nonlinear distortion for each antenna element 191, or nonlinear distortion information indicating the antenna element 191 with the largest amount of nonlinear distortion, to the estimation result notification device 340. The estimation result notification device 340 notifies the transmitting device 100 of the nonlinear distortion information input from the EVM comparison unit 334 via radio or a backbone line (step S14 in FIG. 10).

[0075] Next, a process in a case where feedback from the receiving device 300 of the wireless communication system 1 is not used will be described. Fig. 13 is a flow chart showing a process of the transmitting device 100 of the wireless transmission device 11. In the process shown in Fig. 13, the transmitting device 100 branches signals #1 to #M which are output from the RF chains #1 to #M to the UCA 190, and outputs them to the estimating device 220. The estimating device 220 estimates the magnitude of P1 dB based on the branched signals #1 to #M. The phase offset calculating device 130 refers to a lookup table (LUT) in the PAPR information holding unit 132 based on the estimation result, and determines the amount of phase offset.

[0076] The transmission control device 110 of the transmitting device 100 determines parameter values ​​such as the number of mode multiplexing, the transmission OAM mode, the modulation multi-level number, the symbol rate, etc. (step S51). The signal processing device 120 generates signals to be transmitted in each transmission OAM mode according to the determined parameter values ​​(step S52).

[0077] Phase offset determination section 133 of phase offset calculation device 130 determines the amount of phase offset for each transmission OAM mode (step S53). When phase offset calculation device 130 has not received phase offset information, it may initially determine the amount of phase offset for each transmission OAM mode to be 0, that is, no phase offset. Phase offset granting device 150 grants a phase offset amount corresponding to the OAM mode used to transmit the signal input from signal processing device 120 to the signal, and outputs the signal to OAM mode generation device 160 (step S54).

[0078] The OAM mode generating device 160 converts each signal input from the phase offset adding device 150 into an OAM mode signal to be output from each of the M antenna elements 191. The OAM mode generating device 160 multiplexes the signals of each OAM mode for each antenna element 191 to generate signals #1 to #M (step S55). The preamble adding device 170 adds a preamble to the signals #1 to #M in the same manner as the process of step S12 in FIG. 10 (step S56). The RF chain 180 frequency-converts and amplifies the signals #1 to #M to which the preamble has been added (step S57). The UCA 190 transmits the signals #1 to #M from the antenna elements 191-1 to 191-M, respectively (step S58).

[0079] The estimation device 220 performs the same process as that of the estimation device 330 shown in FIG. 12 (step S59). However, in step S31, the transmission antenna output acquisition unit 221 extracts frames corresponding to preambles from the signals #1 to #M input by the preamble adding units 171-1 to 171-M to the antenna elements 191-1 to 191-M. The constellation extraction unit 222 classifies signal points for each antenna element 191 by the same process as that of the constellation extraction unit 332 based on the voltage of the preamble included in the frame extracted by the transmission antenna output acquisition unit 221. The EVM calculation unit 223 performs the same process as that of the EVM calculation unit 333 in step S32, and calculates the average EVM of the signal points P and Q for each antenna element 191. The EVM comparison unit 224 performs the same process as that of the EVM comparison unit 334 in step S33, and calculates the amount of nonlinear distortion for each antenna element 191. The EVM comparator 224 compares the amount of nonlinear distortion of each antenna element 191, and notifies the phase offset calculation device 130 of the antenna element 191 with the largest amount of nonlinear distortion as the antenna element 191 with the lowest P1dB.

[0080] Transmitting apparatus 100 repeats the process from step S52. In step S53, phase offset determination section 133 of phase offset calculation apparatus 130 determines the phase offset by the same process as in step S15 of FIG.

[0081] 14 is a device configuration diagram showing an example of the hardware configuration of the transmitting device 100 and the receiving device 300. The transmitting device 100 and the receiving device 300 each include a processor 71, a storage unit 72, a communication interface 73, and a user interface 74.

[0082] The processor 71 is a central processing unit that performs calculations and control. The processor 71 is, for example, a CPU. The processor 71 reads out and executes a program from the storage unit 72. Some of the functions of the transmitting device 100 and the receiving device 300 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The storage unit 72 further has a work area for the processor 71 to execute various programs. The communication interface 73 is connected to other devices so as to be able to communicate with them. The user interface 74 is an input device such as a keyboard, a pointing device (mouse, tablet, etc.), a button, or a touch panel, or a display device such as a display. Human operations are input through the user interface 74.

[0083] According to the above-described embodiment, the wireless communication system includes a transmitting device and a receiving device. The transmitting device includes an antenna, a phase offset applying unit, an OAM mode generating unit, a radio processing unit, and a phase offset amount calculation unit. For example, the antenna corresponds to the UCA 190 of the embodiment, the phase offset applying unit corresponds to the phase offset applying device 150 of the embodiment, the OAM mode generating unit corresponds to the OAM mode generating device 160 of the embodiment, the radio processing unit corresponds to the RF chain 180 of the embodiment, and the phase offset amount calculation unit corresponds to the phase offset calculation device 130 of the embodiment. The antenna transmits an OAM multiplexed signal by a plurality of antenna elements arranged in a circle. The phase offset applying unit applies a phase offset amount to a signal to be transmitted by each OAM mode. The OAM mode generating unit generates a signal of each OAM mode to be transmitted by each antenna element from the signal to which the phase offset amount is applied, and generates a multiplexed signal by multiplexing the generated signals of each OAM mode for each antenna element. The radio processing unit converts the multiplexed signal for each antenna element into a radio multiplexed signal, and transmits the radio multiplexed signal from the corresponding antenna element. The phase offset calculation unit calculates the amount of phase offset to be applied to a signal transmitted in each OAM mode by the phase offset application unit in accordance with the characteristics of the radio processing unit.

[0084] The receiving device includes a receiving unit, an OAM mode separation unit, and a receiving signal processing unit. For example, the receiving unit corresponds to the UCA 310 and the RF chain 320 of the embodiment, the OAM mode separation unit corresponds to the OAM mode separation device 350 of the embodiment, and the receiving signal processing unit corresponds to the receiving signal processing device 360 ​​of the embodiment. The receiving unit receives a wireless multiplexed signal transmitted from each of a plurality of antenna elements of an antenna of the transmitting device, and converts the frequency of the received multiplexed signal. The OAM mode separation unit separates the multiplexed signal frequency-converted by the receiving unit into signals of each OAM mode. The receiving signal processing unit removes the phase offset amount provided by the phase offset providing unit of the transmitting device from the OAM mode signal separated by the OAM mode separation unit.

[0085] The wireless communication system further includes an estimation unit. The estimation unit corresponds to, for example, the estimation device 220 and the estimation device 330 of the embodiments. The estimation unit estimates characteristics of the wireless processing unit based on a wireless multiplexed signal converted by the wireless processing unit, or estimates characteristics of the wireless processing unit based on a multiplexed signal frequency-converted in the receiving unit.

[0086] The transmitting device may further include a preamble adding unit that adds a preamble to the multiplexed signal for each antenna element. The estimation unit estimates the characteristics of the radio processing unit based on the preamble added to the multiplexed signal.

[0087] The estimation unit may estimate the nonlinear distortion for each antenna element based on the difference between the mean square error of a high-voltage signal point and the mean square error of a low-voltage signal point in a constellation of the multiplexed signal.

[0088] The radio processing unit may have radio elements corresponding to the plurality of antenna elements, respectively. The radio elements correspond to, for example, RF chains #1 to #8 in the embodiment. The radio elements perform processing for converting a multiplexed signal transmitted from the corresponding antenna element into a radio signal. The estimation unit estimates the characteristics of the radio elements corresponding to the respective antenna elements as the characteristics of the radio processing unit. The phase offset amount calculation unit has an information holding unit and a phase offset determination unit. The information holding unit holds a lookup table indicating the phase offset amount to be applied to the signal of each OAM mode. The phase offset determination unit selects one of the antenna elements based on the characteristics of the radio element corresponding to each antenna element, and reads out the phase offset amount to be applied to the signal of each OAM mode from the lookup table corresponding to the selected antenna element. The characteristic of the radio element is, for example, output power at 1 dB gain compression.

[0089] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and designs that do not deviate from the gist of the present invention are also included. [Explanation of symbols]

[0090] 1. Wireless communication systems 11 Radio transmission equipment 12 Radio transmission equipment 71 Processor 72 Memory section 73 Communication Interface 74 User Interface 100 Transmitting device 110 Transmission control device 111 Communication performance acquisition section 112 Transmission OAM mode determination unit 113 Multiplex number determination unit 114 Transmission signal parameter determination unit 120 Signal Processing Device 130 Phase offset calculation device 131 Communication parameter acquisition unit 132 PAPR information holding unit 133 Phase offset determination unit 140 Phase offset notification device 150 Phase offset adding device 160 OAM mode generator 170 Preamble Applicator 180 RF Chain 190 UCA 191-1~191-M Antenna elements 210 Estimated information acquisition device 220 Estimation device 221 Transmitting antenna output acquisition unit 222 Constellation Extraction Unit 223 EVM calculation section 224 EVM comparison section 300 Receiving device 310 UCA 320 RF Chain 330 Estimation device 331 Preamble Acquisition Unit 332 Constellation Extraction Unit 333 EVM calculation section 334 EVM comparison section 340 Estimation result notification device 350 OAM mode separator 360 Receiving signal processing device 370 Demodulator 380 Phase offset acquisition device

Claims

1. a phase offset imparting step of imparting a phase offset amount to a signal transmitted in each OAM mode by a transmitting device having an antenna for transmitting an OAM (Orbital Angular Momentum) multiplexed signal by a plurality of antenna elements arranged in a circle; an OAM mode generation step in which the transmitting device generates a signal of each OAM mode to be transmitted by each of the antenna elements from the signal to which the phase offset amount has been added, and generates a multiplexed signal by multiplexing the generated signals of each OAM mode for each of the antenna elements; a wireless transmission step in which the transmitting device converts the multiplexed signals for each of the antenna elements into wireless multiplexed signals by a wireless processing unit, and transmits the wireless multiplexed signals from the corresponding antenna elements; a receiving step of receiving the wireless multiplexed signal transmitted from each of the plurality of antenna elements in the wireless transmitting step and converting a frequency of the received multiplexed signal by a receiving device; a separation step of separating the multiplexed signal frequency-converted in the receiving step into signals of each OAM mode; a received signal processing step in which the receiving device removes the phase offset amount applied in the phase offset applying step from the OAM mode signal separated in the separating step; an estimation step in which the transmitting device estimates characteristics of the radio processing unit based on the radio multiplexed signal converted in the radio transmitting step, or the receiving device estimates characteristics of the radio processing unit based on the multiplexed signal whose frequency has been converted in the receiving step; a calculation step of calculating, by the transmitting device, a phase offset amount to be applied to a signal to be transmitted in each OAM mode in the phase offset applying step, according to the characteristic of the radio processing unit estimated in the estimation step; A wireless communication method comprising:

2. A wireless communication system having a transmitting device and a receiving device, The transmitting device an antenna for transmitting an OAM (Orbital Angular Momentum) multiplexed signal by using a plurality of antenna elements arranged in a circle; a phase offset adding unit that adds a phase offset amount to a signal transmitted in each OAM mode; an OAM mode generating unit that generates a signal of each OAM mode to be transmitted by each of the antenna elements from the signal to which the phase offset amount has been added, and generates a multiplexed signal by multiplexing the generated signals of each OAM mode for each of the antenna elements; a wireless processing unit that converts the multiplexed signals for each of the antenna elements into wireless multiplexed signals and transmits the wireless multiplexed signals from the corresponding antenna elements; a phase offset amount calculation unit that calculates a phase offset amount to be assigned to a signal transmitted by the phase offset assigning unit in each OAM mode in accordance with a characteristic of the wireless processing unit, The receiving device includes: a receiving unit that receives the wireless multiplexed signal transmitted from each of the plurality of antenna elements and converts a frequency of the received multiplexed signal; an OAM mode separation unit that separates the multiplexed signal frequency-converted by the receiving unit into signals of each OAM mode; a reception signal processing unit that removes the phase offset amount that is applied by the phase offset application unit from the OAM mode signal separated by the OAM mode separation unit, The wireless communication system includes: an estimation unit that estimates a characteristic of the wireless processing unit based on the wireless multiplexed signal converted by the wireless processing unit, or that estimates a characteristic of the wireless processing unit based on the multiplexed signal frequency-converted in the receiving unit; Wireless communication system.

3. The transmitting device further includes a preamble adding unit that adds a preamble to the multiplexed signal for each of the antenna elements, The estimation unit estimates a characteristic of the radio processing unit based on the preamble added to the multiplexed signal.

3. The wireless communication system according to claim 2.

4. the estimation unit estimates nonlinear distortion for each of the antenna elements based on a difference between a mean square error of a high-voltage signal point and a mean square error of a low-voltage signal point in a constellation of the multiplexed signal.

3. The wireless communication system according to claim 2.

5. the radio processing unit has radio elements corresponding to the plurality of antenna elements, The wireless elements perform processing for converting the multiplexed signals to be transmitted from the corresponding antenna elements into wireless signals; the estimation unit estimates characteristics of the radio elements corresponding to the respective antenna elements as characteristics of the radio processing unit; The phase offset calculation unit an information storage unit that stores a lookup table indicating a phase offset amount to be applied to a signal in each OAM mode; a phase offset determination unit that selects one of the antenna elements based on the characteristics of the radio elements corresponding to each of the antenna elements, and reads out a phase offset amount to be applied to a signal of each OAM mode from the lookup table corresponding to the selected antenna element.

3. The wireless communication system according to claim 2.

6. The characteristic is output power at 1 dB gain compression.

3. The wireless communication system according to claim 2.

7. an antenna for transmitting an OAM (Orbital Angular Momentum) multiplexed signal by using a plurality of antenna elements arranged in a circle; a phase offset adding unit that adds a phase offset amount to a signal transmitted in each OAM mode; an OAM mode generating unit that generates a signal of each OAM mode to be transmitted by each of the antenna elements from the signal to which the phase offset amount has been added, and generates a multiplexed signal by multiplexing the generated signals of each OAM mode for each of the antenna elements; a wireless processing unit that converts the multiplexed signals for each of the antenna elements into wireless multiplexed signals and transmits the wireless multiplexed signals from the corresponding antenna elements; an estimation unit that estimates a characteristic of the wireless processing unit based on the wireless multiplexed signal converted by the wireless processing unit; a phase offset amount calculation unit that calculates a phase offset amount to be assigned to a signal transmitted in each OAM mode by the phase offset assigning unit in accordance with the characteristic of the wireless processing unit estimated by the estimation unit; A transmitting device comprising:

8. a receiver that receives a multiplexed signal in which signals of each OAM mode are multiplexed, the multiplexed signal being transmitted from each of a plurality of antenna elements arranged in a circle in an antenna of a transmitting device that transmits an OAM (Orbital Angular Momentum) multiplexed signal, and converts the frequency of the multiplexed signal; an OAM mode separation unit that separates the multiplexed signal frequency-converted by the receiving unit into signals of each OAM mode; a reception signal processing unit that removes a phase offset amount applied by the transmission device from the OAM mode signal separated by the OAM mode separation unit; an estimation unit that estimates characteristics of a frequency conversion unit that converted the multiplexed signal into the multiplexed signal of a radio frequency in the transmission device, based on the multiplexed signal frequency-converted by the reception unit; a notification unit that notifies the transmission device of the characteristic estimated by the estimation unit; A receiving device comprising:

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