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

Abstract

A transmission device according to the present invention comprises a phase offset derivation unit that derives a phase offset amount for each orbital angular momentum mode such that the locations of signal points will not overlap, a phase offset application unit that applies offsets of the phase offset amounts to signals associated with the orbital angular momentum modes, a mode generation unit that generates signals for the orbital angular momentum modes from the signals associated with the orbital angular momentum modes to which the offsets of the phase offset amounts were applied and multiplexes the signals generated for the orbital angular momentum modes at each of a plurality of antenna elements, and an antenna array that transmits the multiplexed signals for the orbital angular momentum modes from the plurality of antenna elements.

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, transmission of radio signals spatially multiplexed according to orbital angular momentum (OAM) modes (OAM multiplexing transmission) has been studied with the aim of improving communication capacity (see Non-Patent Document 1). In electromagnetic waves with OAM, equiphase fronts are distributed in a spiral pattern along the propagation axis of the electromagnetic waves. Hereinafter, the phase rotation number of the equiphase fronts of electromagnetic waves with orbital angular momentum is referred to as the "OAM mode." Electromagnetic waves propagating in the same direction have orthogonality for each OAM mode. Therefore, a transmitting device can spatially multiplex radio signals of each OAM mode. A receiving device separates modulated signals of different data sequences from the radio signals of each OAM mode based on the radio signals of each OAM mode.

[0003] In OAM multiplexing transmission, a uniform circular array antenna (UCA: Uniform circular array) transmits multiplexed radio signals (OAM mode signals) for each OAM mode (see Non-Patent Document 2). A Discrete Fourier Transform (DFT: Discrete Fourier transform) matrix is ​​used to generate each multiplexed OAM mode signal. An Inverse Discrete Fourier Transform (IDF: Inverse DFT) matrix is ​​used to separate each OAM mode signal.

[0004] Furthermore, a technique for reducing the peak-to-average power ratio (PAPR) of a wireless signal in a MIMO (Multiple Input Multiple Output) system has been proposed (see Non-Patent Document 3). [Prior art documents] [Non-patent literature]

[0005] [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. [Non-patent document 3] SHHan et.al., “An overview of peak-to-average power ratio reduction techniques for multicarrier transmission,” IEEE Wireless Communications, vol.12., Issue.2., pp.56-65., Apr. 2005. Summary of the Invention [Problem to be solved by the invention]

[0006] In OAM multiplexing transmission, a transmitter spatially multiplexes radio signals (modulated signals) in multiple OAM modes. If signal points of different OAM modes overlap in the signal constellation (signal point group), the peak-to-average power ratio (PAPR) of the transmitted radio signal increases. When an amplifier in the transmitter amplifies a power signal converted from a radio signal with a high peak-to-average power ratio, the backoff of the power signal input to the amplifier must be adjusted to a predetermined value or higher. Adjusting the backoff to a predetermined value or higher can result in a reduction in the power of the power signal output from the amplifier in the transmitter. Furthermore, a reduction in transmission power leads to a reduction in the signal-to-noise ratio (SNR) on the receiver side, degrading signal quality.

[0007] In addition, the technology for reducing the peak-to-average power ratio of MIMO wireless signals can also be applied to OAM multiplexed transmission. However, in order to reduce the peak-to-average power ratio while maintaining spatial orthogonality, it is necessary to perform iterative calculations, which results in a problem of a huge amount of calculations.

[0008] 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 are capable of reducing the peak-to-average power ratio of spatially multiplexed radio signals according to orbital angular momentum modes while suppressing an enormous amount of calculation. [Means for solving the problem]

[0009] One aspect of the present invention is a wireless communication method executed by a wireless communication system having a transmitting device and a receiving device, in which the transmitting device derives a phase offset amount for each orbital angular momentum mode so that signal points do not overlap with each other, applies an offset of the phase offset amount to a signal associated with each orbital angular momentum mode, generates a signal of each orbital angular momentum mode from the signal associated with each orbital angular momentum mode to which the offset of the phase offset amount has been applied, multiplexes the generated signals of each orbital angular momentum mode for each antenna element constituting a plurality of antenna elements, and transmits the multiplexed signals of each orbital angular momentum mode to a previous a plurality of antenna elements for transmitting signals from the plurality of antenna elements, wherein the receiving device receives the multiplexed signals of each of the orbital angular momentum modes, separates the signals of each of the orbital angular momentum modes from the multiplexed signals of each of the orbital angular momentum modes, generates signals associated with each of the orbital angular momentum modes from the signals of each of the orbital angular momentum modes, removes an offset of a phase offset amount derived for each of the orbital angular momentum modes from the signals associated with each of the orbital angular momentum modes so that positions of signal points do not overlap with each other, and performs predetermined received signal processing on the signals associated with each of the orbital angular momentum modes from which the offset has been removed.

[0010] One aspect of the present invention is a wireless communication system having a transmitting device and a receiving device, the transmitting device including: a phase offset derivation unit that derives a phase offset amount for each orbital angular momentum mode so that signal points do not overlap with each other; a phase offset applying unit that applies an offset of the phase offset amount to a signal associated with each orbital angular momentum mode; a mode generation unit that generates a signal of each orbital angular momentum mode from the signal associated with each orbital angular momentum mode to which the offset of the phase offset amount has been applied, and multiplexes the generated signal of each orbital angular momentum mode for each antenna element constituting a plurality of antenna elements; and a mode generation unit that multiplexes the multiplexed signal of each orbital angular momentum mode for each of the plurality of antenna elements. and an array antenna that transmits from elements, wherein the receiving device includes an array antenna that acquires the multiplexed signals of each of the orbital angular momentum modes, a mode separation unit that separates the signals of each of the orbital angular momentum modes from the multiplexed signals of each of the orbital angular momentum modes and generates signals associated with each of the orbital angular momentum modes from the signals of each of the orbital angular momentum modes, and a received signal processing unit that removes an offset of a phase offset amount derived for each of the orbital angular momentum modes so that positions of signal points do not overlap with each other from the signals associated with each of the orbital angular momentum modes and performs predetermined received signal processing on the signals associated with each of the orbital angular momentum modes from which the offset has been removed.

[0011] One aspect of the present invention is a transmitting device comprising: a phase offset derivation unit that derives a phase offset amount for each orbital angular momentum mode so that signal point positions do not overlap one another; a phase offset applying unit that applies an offset of the phase offset amount to a signal associated with each orbital angular momentum mode; a mode generating unit that generates a signal of each of the orbital angular momentum modes from the signal associated with each of the orbital angular momentum modes to which the offset of the phase offset amount has been applied, and multiplexes the generated signals of each of the orbital angular momentum modes for each antenna element constituting a plurality of antenna elements; and an array antenna that transmits the multiplexed signals of each of the orbital angular momentum modes from the plurality of antenna elements.

[0012] One aspect of the present invention is a receiving device that includes an array antenna that acquires multiplexed signals of each orbital angular momentum mode, a mode separation unit that separates each orbital angular momentum mode signal from the multiplexed signals of each orbital angular momentum mode and generates a signal associated with each orbital angular momentum mode from the signals of each orbital angular momentum mode, and a received signal processing unit that removes an offset of a phase offset amount derived for each orbital angular momentum mode from the signals associated with each orbital angular momentum mode so that signal point positions do not overlap with each other, and performs predetermined received signal processing on the signals associated with each orbital angular momentum mode from which the offset has been removed. [Effects of the Invention]

[0013] According to the present invention, it is possible to reduce the peak-to-average power ratio of a spatially multiplexed radio signal according to the orbital angular momentum mode while suppressing an enormous amount of calculation. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram illustrating an example of the configuration of a wireless communication system according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of a transmitting device according to an embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of the configuration of a receiving device according to an embodiment. [Figure 4] FIG. 10 is a diagram illustrating an example of an OAM mode in an embodiment. [Figure 5] FIG. 2 is a diagram illustrating an example of the configuration of a transmission control device according to an embodiment. [Figure 6] FIG. 1 is a diagram illustrating an example of the configuration of a phase offset derivation device according to an embodiment. [Figure 7] FIG. 10 is a diagram illustrating an example of a lookup table in the embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of deriving a phase offset amount in the embodiment. [Figure 9] FIG. 10 is a diagram illustrating a first example of offset processing in the embodiment. [Figure 10] FIG. 10 is a diagram illustrating a second example of offset processing in the embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of connections between an OAM mode generating device, an RF chain, and a UCA in an embodiment. [Figure 12] FIG. 10 is a diagram illustrating an example of offset removal processing in the embodiment. [Figure 13] 10 is a flowchart illustrating an example of a phase offset amount derivation operation in the embodiment. [Figure 14] 10 is a flowchart illustrating an example of the operation of a transmitting device in the embodiment. [Figure 15] 10 is a flowchart illustrating an example of the operation of a receiving device according to an embodiment. [Figure 16] FIG. 2 is a diagram illustrating an example of a hardware configuration of a communication device according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings. 1 is a diagram illustrating an example of the configuration of a wireless communication system 1 according to an embodiment. The wireless communication system 1 is a communication system that transmits spatially multiplexed wireless signals according to the OAM mode of electromagnetic waves. The wireless communication system 1 includes a transmitting device 100 and a receiving device 200.

[0016] Transmitting device 100 is a wireless communication device on the transmitting side. Transmitting device 100 may be a stationary wireless communication device (base station) or a mobile wireless communication device (mobile communication terminal). Transmitting device 100 transmits, from a uniform circular array antenna (UCA) of transmitting device 100, wireless signals spatially multiplexed according to the OAM mode of the electromagnetic waves. Transmitting device 100 also notifies receiving device 200 of the amount of phase offset of the signal in each OAM mode.

[0017] The receiving device 200 is a wireless communication device on the receiving side. The receiving device 200 may be a stationary wireless communication device or a mobile wireless communication device. The receiving device 200 receives the wireless signal transmitted from the transmitting device 100 with its equally spaced circular array antenna. The receiving device 200 converts the received wireless signal into a power signal. The receiving device 200 separates the modulated signals from the converted power signal for each OAM mode. The receiving device 200 generates a modulated signal associated with each OAM mode from the modulated signal of each OAM mode.

[0018] Receiving device 200 removes the offset of the phase offset amount from the modulated signal associated with each OAM mode based on the phase offset amount notified from receiving device 200. Receiving device 200 performs demodulation processing on the modulated signal of each OAM mode from which the offset has been removed.

[0019] 2 is a diagram showing an example of the configuration of a transmitting device 100 according to an embodiment. The transmitting device 100 includes a transmission control device 110 (transmission control unit), a transmission signal processing device 120 (transmission signal processing unit), a phase offset derivation device 130 (phase offset derivation unit), a phase offset notification device 140 (phase offset notification unit), a phase offset assigning device 150 (phase offset assigning unit), an OAM mode generation device 160 (mode generation unit), an RF chain (Radio frequency chain) 170 (amplification unit), and a UCA 180 (array antenna).

[0020] The transmission control device 110 determines communication parameters. The communication parameters are, for example, the number of mode multiplexings (the number of OAM modes of the multiplexed signal), the OAM mode index (for example, 0, 1, -1, 2, -2, 3, -3, 4), and the modulation multi-level number (the number of bits transmitted per symbol). The maximum value of the number of mode multiplexings is equal to the number of antenna elements. The transmission control device 110 outputs communication parameters (signals for specifying communication parameters) to the transmission signal processing device 120, the phase offset derivation device 130, and the OAM mode generation device 160.

[0021] A predetermined data sequence is input to the transmission signal processing device 120. The transmission signal processing device 120 acquires communication parameters from the transmission control device 110. The transmission signal processing device 120 generates digital signals compatible with each OAM mode based on the communication parameters. The transmission signal processing device 120 converts the digital signals compatible with each OAM mode into analog signals compatible with each OAM mode.

[0022] The transmission signal processing device 120 (converter) converts the frequency of an analog signal corresponding to each OAM mode into the frequency band of the carrier wave of the radio signal. As a result, the transmission signal processing device 120 generates a signal corresponding to each OAM mode (a signal associated with each OAM mode). The transmission signal processing device 120 outputs the signal corresponding to each OAM mode to the phase offset adding device 150.

[0023] Phase offset derivation device 130 derives the amount of phase offset of the signal in each OAM mode based on communication parameters (signals for specifying communication parameters). Phase offset derivation device 130 derives the amount of phase offset of the signal in each OAM mode based on, for example, the OAM mode and the number of multiplexed modes, so as to reduce the peak-to-average power ratio (PAPR) of the wireless signal.

[0024] Here, phase offset derivation device 130 may derive a phase offset amount for a signal in each OAM mode so as to reduce the peak-to-average power ratio of radio signals transmitted from all antenna elements of UCA 180. Phase offset derivation device 130 may derive a phase offset amount for a signal in each OAM mode so as to reduce the peak-to-average power ratio of radio signals transmitted from a specific antenna element of UCA 180.

[0025] Phase offset derivation device 130 outputs information indicating the amount of phase offset of the signal in each OAM mode to phase offset notification device 140 and phase offset applying device 150.

[0026] Phase offset notification device 140 converts the information indicating the phase offset amount input from phase offset derivation device 130 into information in a predetermined notification format. Phase offset notification device 140 notifies receiving device 200 of the information indicating the phase offset amount of the signal in each OAM mode in the predetermined notification format, for example, via a backbone line (not shown).

[0027] Phase offset adding device 150 (offset processing device) performs offset processing (addition of an offset) on signals corresponding to each OAM mode based on the phase offset amount notified by phase offset derivation device 130. Phase offset adding device 150 outputs the signals corresponding to each OAM mode to which an offset has been added to OAM mode generation device 160.

[0028] OAM mode generating device 160 acquires communication parameters from transmission control device 110. OAM mode generating device 160 acquires signals corresponding to each OAM mode to which an offset has been added from phase offset adding device 150. OAM mode generating device 160 generates signals for each OAM mode specified using the communication parameters from the signals corresponding to each OAM mode to which an offset has been added. Note that the amount of phase offset may be zero as long as the peak-to-average power ratio is reduced.

[0029] Here, OAM mode generation device 160 generates signals (OAM signals) for each OAM mode specified using communication parameters, using a discrete Fourier transform matrix for each OAM mode signal. OAM mode generation device 160 multiplexes the generated signals for each OAM mode for each antenna element of UCA 180, using a discrete Fourier transform matrix. OAM mode generation device 160 outputs the multiplexed signals for each OAM mode (multiplexed OAM signals) to RF chain 170.

[0030] The RF chain 170 (RF processing unit) includes a frequency converter, a filter, and an amplifier. The RF chain 170 performs, for example, frequency conversion, band limiting, and amplification on the multiplexed signals of each OAM mode. The RF chain 170 outputs the amplified multiplexed signals (power signals) of each OAM mode to the UCA 180.

[0031] The UCA 180 is an equally spaced circular array antenna. In an equally spaced circular array antenna, multiple (M) antenna elements are arranged in a circle at equal intervals. The UCA 180 transmits spatially multiplexed radio signals according to the OAM modes of the electromagnetic waves, based on the multiplexed signals of each OAM mode after amplification processing.

[0032] 3 is a diagram illustrating an example of the configuration of a receiving device 200 according to an embodiment. The receiving device 200 includes a UCA 210 (array antenna), an RF chain 220 (amplifier), an OAM mode separation device 230 (mode separation unit), a phase offset acquisition device 240 (phase offset acquisition unit), a received signal processing device 250, and a demodulator 260.

[0033] The UCA 210 is an equally spaced circular array antenna. In an equally spaced circular array antenna, multiple (M) antenna elements are arranged in a circle at equal intervals. The UCA 210 receives (acquires) radio signals spatially multiplexed according to the OAM modes of the electromagnetic waves from the UCA 180. The UCA 210 outputs multiplexed signals (power signals) of each OAM mode according to the received radio signals to the RF chain 220.

[0034] The RF chain 220 (RF processing unit) performs, for example, amplification and band limiting on the multiplexed signals of each OAM mode. The RF chain 220 may also perform frequency conversion on the multiplexed signals of each OAM mode. The RF chain 220 outputs the amplified multiplexed signals (power signals) of each OAM mode to the OAM mode demultiplexer 230.

[0035] OAM mode demultiplexing device 230 separates each OAM mode signal from the multiplexed signals using an inverse discrete Fourier transform matrix for each OAM mode signal. OAM mode demultiplexing device 230 generates a signal corresponding to each OAM mode from each OAM mode signal using the inverse discrete Fourier transform matrix. OAM mode demultiplexing device 230 outputs the signal corresponding to each OAM mode to received signal processing device 250.

[0036] The phase offset acquisition device 240 outputs information indicating the amount of phase offset notified by the phase offset notification device 140 in a predetermined notification format to the received signal processing device 250 .

[0037] Reception signal processing device 250 is a device that performs predetermined reception signal processing. Reception signal processing device 250 acquires information indicating the phase offset amount from phase offset acquisition device 240. Reception signal processing device 250 removes the phase offset amount from the signal corresponding to each OAM mode for each OAM mode based on the notified phase offset amount. Reception signal processing device 250 performs predetermined reception signal processing on the signal corresponding to each OAM mode from which the offset has been removed. In this way, reception signal processing device 250 generates a modulated signal corresponding to each OAM mode. Reception signal processing device 250 outputs the modulated signal corresponding to each OAM mode to demodulator 260. Demodulator 260 performs predetermined demodulation processing on the modulated signal corresponding to each OAM mode.

[0038] Next, the OAM mode will be described in detail. 4 is a diagram showing an example of OAM modes in an embodiment. The OAM mode generation device 160 applies a phase difference to the power signal input to each antenna element of the UCA 180 via the RF chain 170 using a discrete Fourier transform matrix. In this way, the OAM mode generation device 160 generates multiplexed signals for each OAM mode.

[0039] The OAM mode generating device 160 generates a signal of OAM mode "n" by imparting a phase difference between adjacent antenna elements to the signal input to each antenna element of the UCA 180 so that the phase of the signal of OAM mode "n" rotates by "n".

[0040] For example, when an OAM mode 2 signal is generated to be supplied to the eight antenna elements of UCA 180, OAM mode generator 160 applies phase differences of 0 degrees, 90 degrees, 180 degrees, 270 degrees, and 0 degrees, 90 degrees, 180 degrees, and 270 degrees to the antenna elements in clockwise order so that the phase of the OAM mode 2 signal rotates twice.

[0041] Next, the details of the transmitting device 100 will be described. 5 is a diagram showing an example of the configuration of a transmission control device 110 according to an embodiment. The transmission control device 110 includes a characteristics information acquisition unit 111, a transmission OAM mode determination unit 112, a multiplex number determination unit 113, and a transmission signal parameter determination unit 114.

[0042] The characteristic information acquisition unit 111 is a device that acquires communication characteristic information. The communication characteristic information is information that represents characteristics of communication between the transmitting device 100 and the receiving device 200. The characteristics represented by the communication characteristic information are, for example, the distance between the transmitting device 100 and the receiving device 200 (hereinafter referred to as the "transmission / reception distance"), the received signal power to interference and noise power ratio (SINR), and characteristics of interference between signals in the OAM mode.

[0043] Transmission OAM mode determination unit 112 determines the OAM mode of the signal to be transmitted (hereinafter referred to as "transmission OAM mode") based on, for example, the distance between transmitter and receiver and the ratio of received signal power to interference and noise power. Multiplex number determination unit 113 determines the number of multiplexed modes based on, for example, the distance between transmitter and receiver and the ratio of received signal power to interference and noise power.

[0044] The transmission signal parameter determination unit 114 determines transmission signal parameters such as the modulation level and coding rate based on, for example, the distance between transmitter and receiver and the ratio of received signal power to interference plus noise power. The order in which the transmission control device 110 determines the transmission OAM mode, the number of mode multiplexings, and the transmission signal parameters is arbitrary.

[0045] 6 is a diagram showing an example of the configuration of a phase offset derivation device 130 according to an embodiment. The phase offset derivation device 130 includes a parameter acquisition unit 131, a phase offset holding unit 132, an algorithm execution unit 133, and a phase offset notification unit 134.

[0046] The parameter acquisition unit 131 acquires the number of antenna elements, the number of mode multiplexing, and the OAM mode index as communication parameters from the transmission control device 110. The parameter acquisition unit 131 outputs the number of antenna elements, the number of mode multiplexing, and the OAM mode index to the phase offset holding unit 132 as communication parameters.

[0047] The phase offset holding unit 132 holds a lookup table (LUT) in advance. The phase offset holding unit 132 acquires the phase offset amount that reduces the peak to average power ratio from the lookup table based on the number of antenna elements, the number of modes multiplexed, and the OAM mode index. For example, the phase offset holding unit 132 acquires the phase offset amount that minimizes the peak to average power ratio from the lookup table for each OAM mode. The phase offset amount acquired for each OAM mode is applied to a signal corresponding to that OAM mode. The phase offset holding unit 132 outputs information indicating the phase offset amount acquired from the lookup table to the phase offset reporting unit 134.

[0048] If the lookup table does not hold information on the phase offset amount corresponding to the communication parameters acquired by the parameter acquisition unit 131, the phase offset holding unit 132 outputs the number of antenna elements, the number of mode multiplexing, and the OAM mode index to the algorithm execution unit 133. The phase offset holding unit 132 acquires, as a response, information indicating the phase offset amount that reduces the peak to average power ratio, the number of antenna elements, the number of mode multiplexing, and the OAM mode index from the algorithm execution unit 133. The phase offset holding unit 132 registers the information indicating the phase offset amount that reduces the peak to average power ratio in the lookup table in association with the combination of the number of antenna elements, the number of mode multiplexing, and the OAM mode index. This updates the lookup table.

[0049] Fig. 7 is a diagram showing an example of a lookup table in an embodiment. In Fig. 7, as an example, the lookup table holds phase offset amounts only for the combination of the number of antenna elements "8", the number of mode multiplexing "8", and the OAM mode index "[0, 1, -1, 2, -2, 3, -3, 4]".

[0050] 6, we will continue to explain the example configuration of phase offset derivation device 130. When algorithm execution unit 133 acquires the number of antenna elements, the number of mode multiplexing, and the OAM mode index from phase offset holding unit 132, algorithm execution unit 133 derives a phase offset amount that reduces the peak power to average power ratio based on the number of antenna elements, the number of mode multiplexing, and the OAM mode index.

[0051] The algorithm executing unit 133 may derive the phase offset amount each time, or the phase offset holding unit 132 may obtain the phase offset amount from a lookup table each time.

[0052] Phase offset reporting section 134 outputs the amount of phase offset that reduces the peak-to-average-power ratio to phase offset reporting device 140 and phase offset applying device 150 for each OAM mode.

[0053] Next, an example of deriving the phase offset amount will be described. 8 is a diagram illustrating an example of how to derive a phase offset amount in an embodiment. As an example, a description will be given of how to derive a phase offset amount when the number of antenna elements is 8, the number of mode multiplexing is 8, and the OAM mode index is [0, 1, -1, 2, -2, 3, -3, 4].

[0054] The algorithm execution unit 133 derives the phase difference "Δφ(l)" between adjacent antenna elements when signals compatible with each OAM mode are multiplexed according to the OAM mode. The phase difference "Δφ(l)" (degrees) is expressed as in Equation (1).

[0055] Δφ(l)=|m(l) / M×360| …(1)

[0056] Here, "m(l)" represents the OAM mode "0, 1, -1, ...". "l" represents the index of the OAM mode. In Figure 8, the phase difference between antenna elements for each OAM mode is "Δφ(l) = [0, 45, 45, 90, 90, 135, 135, 180]".

[0057] The algorithm execution unit 133 divides the phase difference "Δφ(l)" by "90" (degrees) and obtains the remainder "Δφ mod90 (l) is derived. The remainder "Δφ mod90 (l)" is expressed as equation (2).

[0058] Δφ mod90 (l)=mod(Δφ(l),90) …(2)

[0059] Here, the remainder is "Δφ mod90 (l)=[0,45,45,0,0,45,45,0]). In this way, the remainder "Δφ mod90 (l)" becomes "0" or "45".

[0060] The algorithm execution unit 133 calculates the remainder "Δφ mod90The OAM mode "m(l)" for which the remainder "Δφ(l)" is "0" is classified into the first group. mod90 The OAM mode “m(l)” for which “(l)” is “45” is classified into the second group.

[0061] First group OAM mode: m(l)∈(Δφ mod90 (l)=0)=[0,2,-2,4]

[0062] Second group OAM mode: m(l)∈(Δφ mod90 (l)=45)=[1,-1,3,-3]

[0063] The number of elements "K" in each group is 4. Algorithm execution unit 133 derives the phase offset amount for each OAM mode signal so that the phases of OAM mode signals in the same group are separated from each other. In FIG. 8, the algorithm execution unit 133 derives the phase offset amount "22.5 degrees (=90 degrees / K)" for each OAM mode signal in the first group so that the phases of OAM mode signals "[0, 2, -2, 4]" are separated from each other. Also, the algorithm execution unit 133 derives the phase offset amount "22.5 degrees (=90 degrees / K)" for each OAM mode signal in the second group so that the phases of OAM mode signals "[1, -1, 3, -3]" are separated from each other.

[0064] Here, the phase offset amounts given to the signals of each OAM mode in the same group may be "0, 22.5, 45, 67.5" in order from the lowest order mode, or "0, 22.5, 45, 67.5" in any order.

[0065] The algorithm execution unit 133 outputs, as a response, the combination of the number of antenna elements, the number of mode multiplexings, and the OAM mode index, and information indicating the derived phase offset amount, to the phase offset holding unit 132. The algorithm execution unit 133 also outputs the information indicating the derived phase offset amount to the phase offset notification unit 134.

[0066] Fig. 9 is a diagram showing a first example of offset processing in an embodiment. As a comparative example to Fig. 10, Fig. 9 shows an example of offset processing in the case where the phase offset amount of the offset given to the signal corresponding to each OAM mode is 0 degrees. For ease of explanation, the number of antenna elements in Fig. 9 is four, for example.

[0067] Signal 300 is a signal compatible with OAM mode 0. Signal 301 is a signal compatible with OAM mode 1. Multiplexed signal 400 is a multiplexed OAM mode signal. When transmission signal processing device 120 generates a signal compatible with an OAM mode using quadrature amplitude modulation (QAM), the arrangement of signal points of the generated signal is the same for every 90-degree phase difference.

[0068] With the phase difference between the antenna elements associated with signal 300 remaining at 0 degrees, signal 300 is supplied to the four antenna elements of UCA 180. In contrast, the four antenna elements transmitting the OAM mode 1 signal are given phase differences of 0 degrees, 90 degrees, 180 degrees, and 270 degrees in a clockwise direction.

[0069] Even when each phase difference is applied to the signal in this way, the constellation of OAM mode 0 is the same as the constellation of OAM mode 1. OAM mode generation device 160 combines the constellation points of OAM mode 0 and OAM mode 1 using discrete Fourier transform matrix 161. This combination doubles the amplitude at the same constellation point, thereby increasing the peak-to-average power ratio of the radio signal.

[0070] 10 is a diagram showing a second example of offset processing in the embodiment. For ease of explanation, the number of antenna elements in FIG. 10 is four, for example.

[0071] With the phase difference between the antenna elements associated with signal 300 remaining at 0 degrees, signal 300 is output to the four antenna elements of UCA 180. In contrast, a phase offset of 45 degrees is applied to the OAM mode 1 signal relative to the OAM mode 0 signal. As a result, the constellation of signal points in OAM mode 0 and the constellation of signal points in OAM mode 1 are not the same.

[0072] Furthermore, phase differences of 0 degrees, 90 degrees, 180 degrees, and 270 degrees are applied clockwise to the four antenna elements transmitting OAM mode 1 signals. OAM mode generating device 160 combines the OAM mode 0 signal points and OAM mode 1 signal points using discrete Fourier transform matrix 161 while maintaining the 45-degree phase offset (phase difference). This combination prevents the amplitude from doubling at the same signal point, thereby reducing the peak-to-average power ratio of the radio signal.

[0073] 11 is a diagram showing an example of connections between the OAM mode generation device 160, the RF chain 170, and the UCA 180 in an embodiment. In the UCA 180, M antenna elements 181 are arranged in a circle at equal intervals. In FIG. 11, as an example, the phase of the signal transmitted from antenna element 181-1 of the UCA 180 is taken as the reference (phase 0 degrees). Output ports "#1" to "#M" of the OAM mode generation device 160 are connected to input ports "#1" to "#M" of the RF chain 170.

[0074] A signal corresponding to OAM mode n (n = an integer from 0 to N) is input to OAM mode generation device 160 from phase offset addition device 150. In FIG. 11 , “N” is 1, for example. OAM mode generation device 160 outputs the multiplexed result (multiplexed OAM signal) of an OAM mode 0 signal having a phase difference “x” from a reference phase and an OAM mode 1 signal having a phase difference “y” from the reference phase from output ports “#1” to “#M” of OAM mode generation device 160 to input ports “#1” to “#M” of RF chain 170.

[0075] Here, output port "#m" in OAM mode generating device 160 outputs an OAM mode 0 signal with a phase difference of "x=((m-1) / M×360×0)" degrees from the reference phase and an OAM mode 1 signal with a phase difference of "y=((m-1) / M×360×1)" degrees from the reference phase to antenna element "#m" via RF chain 170.

[0076] RF chain 170 amplifies the multiplexed OAM mode signals (multiplexed OAM signals) output from OAM mode generation device 160. RF chain 170 outputs the amplified multiplexed signals of each OAM mode to UCA 180. UCA 180 transmits the signals output from RF chain 170 using radio waves.

[0077] Next, the details of the receiving device 200 will be described. 12 is a diagram showing an example of offset removal processing in an embodiment. Multiplexed signal 500 is a multiplexed OAM mode signal. Signal 600 is, as an example, a signal compatible with OAM mode 0 (a signal associated with OAM mode 0). Signal 601 is, as an example, a signal compatible with OAM mode 1 (a signal associated with OAM mode 1).

[0078] For the purpose of separating multiplexed signal 500 (multiplexed OAM signal), OAM mode separation device 230 determines the phase of each antenna element of UCA 210 so that it is in the opposite rotation direction (opposite phase) to the phase of each antenna element of UCA 180. In Fig. 12, OAM mode separation device 230 determines the phase of each antenna element of UCA 210 to be "[0, -90, -180, -270]" so that it is in the opposite rotation direction to the phase "[0, 90, 180, 270]" of each antenna element illustrated in Fig. 10.

[0079] OAM mode demultiplexing device 230 separates the signals of each OAM mode from multiplexed signal 500 using inverse discrete Fourier transform matrix 231. OAM mode demultiplexing device 230 generates signals corresponding to each OAM mode from the signals of each OAM mode using inverse discrete Fourier transform matrix 231. In FIG. 12 , OAM mode demultiplexing device 230 outputs signals 600 and 601 to received signal processing device 250.

[0080] The phase offset acquisition device 240 acquires information representing the amount of phase offset from the phase offset notification device 140. The received signal processing device 250 acquires information representing the amount of phase offset from the phase offset acquisition device 240.

[0081] The reception signal processing device 250 removes the phase offset of the signal corresponding to each OAM mode from the signal corresponding to each OAM mode. In FIG. 12, the reception signal processing device 250 removes the 45-degree offset from the signal corresponding to OAM mode 1. As a result, the reception signal processing device 250 generates a signal 601 from which the offset has been removed. In this manner, the reception signal processing device 250 restores the signal points using the phase offset amount acquired from the phase offset notification device 140. The reception signal processing device 250 outputs the signal corresponding to each OAM mode from which the offset has been removed to the demodulator 260. The demodulator 260 performs a predetermined demodulation process on the signal corresponding to each OAM mode output from the reception signal processing device 250.

[0082] Next, an example of the operation of the wireless communication system 1 will be described. 13 is a flowchart showing an example of a phase offset derivation operation in an embodiment. The algorithm execution unit 133 (phase offset derivation unit) derives the phase difference "Δφ(l)" between antenna elements for each OAM mode (step S101). The algorithm execution unit 133 derives the remainder "mod(Δφ(l),90)" (step S102).

[0083] The algorithm execution unit 133 classifies OAM mode signals associated with the same remainder "mod(Δφ(l),90)" into the same group (step S103). The algorithm execution unit 133 derives a phase offset amount for each OAM mode signal so that the phases of the OAM mode signals classified into the same group are separated from each other (step S104).

[0084] 14 is a flowchart showing an example of operation of the transmitting device 100 according to the embodiment. The phase offset derivation device 130 derives a phase offset amount for each OAM mode so that the positions of the signal points do not overlap each other (step S201). The phase offset applying device 150 applies an offset of the phase offset amount to a signal corresponding to each OAM mode (step S202).

[0085] OAM mode generation device 160 generates signals for each OAM mode from signals corresponding to each OAM mode to which a phase offset amount has been applied (step S203). OAM mode generation device 160 multiplexes the generated signals for each OAM mode for each antenna element 181 constituting UCA 180 (step S204). UCA 180 transmits the multiplexed signals for each OAM mode from multiple antenna elements 181 (step S205).

[0086] 15 is a flowchart showing an example of operation of receiving device 200 in an embodiment. UCA 210 acquires multiplexed signals of each OAM mode (step S301). OAM mode demultiplexing device 230 demultiplexes the signals of each OAM mode from the multiplexed signals of each OAM mode (step S302). OAM mode demultiplexing device 230 generates signals corresponding to each OAM mode from the signals of each OAM mode (step S303).

[0087] Reception signal processing device 250 removes the phase offset derived for each OAM mode from the signal corresponding to each OAM mode so that the signal points do not overlap (step S304). Reception signal processing device 250 performs predetermined reception signal processing on the signal corresponding to each OAM mode from which the offset has been removed (step S305).

[0088] As described above, in transmitting apparatus 100, phase offset derivation device 130 (phase offset derivation unit) derives a phase offset amount for each OAM mode so that the positions of signal points do not overlap. Phase offset applying device 150 (phase offset applying unit) applies an offset of the phase offset amount to a signal corresponding to each OAM mode (a signal associated with each OAM mode). OAM mode generation device 160 (mode generation unit) generates a signal for each OAM mode from the signal corresponding to each OAM mode to which an offset of the phase offset amount has been applied. OAM mode generation device 160 multiplexes the generated signals for each OAM mode for each antenna element 181 constituting UCA 180 (multiple antenna elements). UCA 180 (array antenna) transmits the multiplexed signals for each OAM mode from multiple antenna elements 181.

[0089] In receiving device 200, UCA 210 (array antenna) acquires multiplexed signals for each OAM mode. OAM mode demultiplexing device 230 (mode demultiplexing unit) demultiplexes each OAM mode signal from the multiplexed signals for each OAM mode. OAM mode demultiplexing device 230 generates a signal corresponding to each OAM mode from the signals for each OAM mode. Received signal processing device 250 (received signal processing unit) removes the phase offset amount derived for each OAM mode from the signals corresponding to each OAM mode so that the positions of the signal points do not overlap with each other. Received signal processing device 250 performs predetermined received signal processing on the signals corresponding to each OAM mode from which the offset has been removed.

[0090] As described above, by focusing on the characteristics of the precoder in wireless communication using OAM multiplexing transmission, it is possible to avoid in-phase combining, suppress the amount of calculations from becoming enormous, and reduce the peak-to-average power ratio of spatially multiplexed wireless signals according to the orbital angular momentum mode, thereby improving communication quality.

[0091] (First Modification) The phase offset acquisition device 240 of the receiving device 200 may estimate the phase offset based on the communication parameters in a manner similar to the manner in which the phase offset derivation device 130 derives the phase offset based on the communication parameters. The receiving device 200 may remove the phase offset from the signal using the estimated phase offset. In this case, the transmitting device 100 may or may not include the phase offset notification device 140.

[0092] (Second Modification) In the above embodiment, the transmission signal processing device 120 converts the frequency of the analog signal corresponding to each OAM mode into the frequency band of the carrier wave of the radio signal, and the phase offset applying device 150 applies an offset to the analog signal corresponding to each OAM mode.

[0093] In a second modification of the embodiment, phase offset adding device 150 may perform offset processing on digital signals corresponding to each OAM mode. OAM mode generating device 160 may generate digital signals for each OAM mode specified using communication parameters from the digital signals corresponding to each OAM mode to which an offset has been added. RF chain 170 may perform, for example, frequency conversion, amplification, and band limiting on the multiplexed digital signals for each OAM mode.

[0094] (Example of hardware configuration) 16 is a diagram illustrating an example of a hardware configuration of the communication device 2 according to the embodiment. The communication device 2 corresponds to a part or all of the transmitting device 100 and the receiving device 200 of the wireless communication system 1.

[0095] The communication device 2 is realized as software by a processor 21, such as a CPU (Central Processing Unit), executing a program stored in a storage device 23 having a non-volatile recording medium (non-transitory recording medium) and a memory 22. The program may be recorded on a computer-readable non-transitory recording medium. Examples of computer-readable non-transitory recording media include portable media such as flexible disks, magneto-optical disks, ROMs (Read Only Memory), and CD-ROMs (Compact Disc Read Only Memory), and storage devices such as hard disks built into computer systems. A communication unit 24 executes predetermined communication processing.

[0096] Some or all of the functional units of the communication device 2 may be analog or digital circuits, and may be realized using hardware including electronic circuits (electronic circuits or circuitry) using, for example, an LSI (Large Scale Integrated circuit), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array).

[0097] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention. [Industrial Applicability]

[0098] The present invention is applicable to wireless communication systems. [Explanation of symbols]

[0099] 1...wireless communication system, 2...communication device, 21...processor, 22...memory, 23...storage device, 24...communication unit, 100...transmitting device, 110...transmission control device, 111...characteristic information acquisition unit, 112...transmission OAM mode determination unit, 113...multiplex number determination unit, 114...transmission signal parameter determination unit, 120...transmission signal processing device, 130...phase offset derivation device, 131...parameter acquisition unit, 132...phase offset holding unit, 133...algorithm execution unit, 134...phase offset notification unit, 140...phase offset Notification device, 150...phase offset applying device, 160...OAM mode generating device, 161...discrete Fourier transform matrix, 170...RF chain, 180...UCA, 181...antenna element, 200...receiving device, 210...UCA, 220...RF chain, 230...OAM mode separating device, 231...inverse discrete Fourier transform matrix, 240...phase offset acquiring device, 250...receiving signal processing device, 260...demodulator, 300...signal, 301...signal, 400...multiplexed signal, 500...multiplexed signal, 600...signal, 601...signal

Claims

1. A wireless communication method executed by a wireless communication system having a transmitting device and a receiving device, The transmitting device classifying orbital angular momentum mode signals into groups based on phase differences between antenna elements constituting a plurality of antenna elements, and deriving a phase offset amount for each of the orbital angular momentum modes so that the phases of the orbital angular momentum mode signals classified into the same group are separated from each other and the positions of the signal points do not overlap with each other; imparting an offset of the phase offset amount to a signal associated with each orbital angular momentum mode; generating a signal of each of the orbital angular momentum modes from signals associated with the orbital angular momentum modes to which an offset of the phase offset amount has been applied, and multiplexing the generated signals of each of the orbital angular momentum modes for each of the antenna elements constituting the plurality of antenna elements; transmitting the multiplexed signals of each of the orbital angular momentum modes from the plurality of antenna elements; The receiving device receiving the multiplexed signals of each of the orbital angular momentum modes; Separating each of the orbital angular momentum modes from the multiplexed signals of each of the orbital angular momentum modes, and generating a signal associated with each of the orbital angular momentum modes from the signals of each of the orbital angular momentum modes; removing an offset of a phase offset amount derived for each orbital angular momentum mode from a signal associated with each of the orbital angular momentum modes so that signal points do not overlap with each other, and performing predetermined received signal processing on the signal associated with each of the orbital angular momentum modes from which the offset has been removed. Wireless communication method.

2. A wireless communication system having a transmitting device and a receiving device, The transmitting device a phase offset derivation unit that classifies orbital angular momentum mode signals into groups based on phase differences between antenna elements constituting a plurality of antenna elements, and derives a phase offset amount for each of the orbital angular momentum modes so that the phases of the orbital angular momentum mode signals classified into the same group are separated from each other and the positions of the signal points do not overlap each other; a phase offset applying unit that applies an offset of the phase offset amount to a signal associated with each orbital angular momentum mode; a mode generating unit that generates a signal of each of the orbital angular momentum modes from a signal associated with each of the orbital angular momentum modes to which an offset of the phase offset amount has been given, and multiplexes the generated signal of each of the orbital angular momentum modes for each of the antenna elements constituting the plurality of antenna elements; an array antenna that transmits the multiplexed signals of each of the orbital angular momentum modes from the plurality of antenna elements; The receiving device an array antenna for acquiring the multiplexed signals of each of the orbital angular momentum modes; a mode separation unit that separates each of the orbital angular momentum mode signals from the multiplexed signals of each of the orbital angular momentum mode signals and generates a signal associated with each of the orbital angular momentum mode signals from the signals of each of the orbital angular momentum mode signals; a received signal processing unit that removes an offset of a phase offset amount derived for each orbital angular momentum mode from a signal associated with each of the orbital angular momentum modes so that positions of signal points do not overlap each other, and performs predetermined received signal processing on the signal associated with each of the orbital angular momentum modes from which the offset has been removed. Wireless communication system.

3. A phase offset derivation unit that classifies orbital angular momentum mode signals into groups based on phase differences between antenna elements that constitute a plurality of antenna elements, and derives a phase offset amount for each of the orbital angular momentum modes so that the phases of the orbital angular momentum mode signals classified into the same group are separated from each other and the positions of the signal points do not overlap each other; a phase offset applying unit that applies an offset of the phase offset amount to a signal associated with each orbital angular momentum mode; a mode generating unit that generates a signal of each of the orbital angular momentum modes from a signal associated with each of the orbital angular momentum modes to which an offset of the phase offset amount has been given, and multiplexes the generated signal of each of the orbital angular momentum modes for each of the antenna elements constituting the plurality of antenna elements; an array antenna that transmits the multiplexed signals of each of the orbital angular momentum modes from the plurality of antenna elements; A transmitting device comprising:

4. The transmitting device according to claim 3 , further comprising a phase offset notifying unit that notifies the receiving device of the phase offset amount.

5. an array antenna for acquiring signals of each multiplexed orbital angular momentum mode; a mode separation unit that separates each of the orbital angular momentum mode signals from the multiplexed signals of each of the orbital angular momentum mode signals and generates a signal associated with each of the orbital angular momentum mode signals from the signals of each of the orbital angular momentum mode signals; a phase offset acquisition unit that classifies orbital angular momentum mode signals into groups based on phase differences between antenna elements that constitute a plurality of antenna elements provided in a transmitting device, and estimates a phase offset amount for each of the orbital angular momentum modes so that the phases of the orbital angular momentum mode signals classified into the same group are separated from each other and the positions of the signal points do not overlap each other; a received signal processing unit that removes an offset of the estimated phase offset amount from a signal associated with each of the orbital angular momentum modes, and performs predetermined received signal processing on the signal associated with each of the orbital angular momentum modes from which the offset has been removed; A receiving device comprising:

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