Wireless communication system, OAM mode selection method, and receiving device

Abstract

This wireless communication system comprises a transmission device that transmits an OAM multiplexing signal and a reception device that receives the OAM multiplexing signal. The reception device performs channel estimation of each OAM mode on the basis of a preamble transmitted from the transmission device, and selects, on the basis of the channel estimation result, a combination of the OAM modes for use in transmission in the transmission device so as to maximize the communication capacity.

Description

[Technical Field]

[0001] The present invention relates to parameter control of OAM multiplex transmission. [Background technology]

[0002] In recent years, spatial multiplexing transmission technology for wireless signals using OAM has been studied to improve communication capacity (for example, Non-Patent Document 1). Electromagnetic waves with OAM have equiphase planes distributed in a spiral pattern along the propagation direction, centered on the propagation axis. Electromagnetic waves with different OAM modes propagating in the same direction have orthogonal spatial phase distributions in the direction of the rotation axis. Therefore, signals can be spatially multiplexed by separating the signals of each OAM mode modulated with different signal sequences at the receiving device.

[0003] In a wireless communication system using this OAM multiplexing transmission technology, a uniform circular array (hereinafter referred to as UCA (Uniform Circular Array)) antenna, in which multiple antenna elements are arranged at equal intervals in a circle, is used to generate, combine, and transmit multiple OAM modes, thereby achieving spatially multiplexed transmission of different signal sequences (see, for example, Non-Patent Document 2). A Butler circuit (Butler matrix circuit), for example, is used to generate and separate signals for 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 millimeter-wave communications with orbital angular momentum multiplexing," Nature Commun., vol.5, p.4876, Sep. 2014. Summary of the Invention [Problem to be solved by the invention]

[0005] OAM multiplexing transmission requires that the transmitting and receiving antennas be placed on the same axis, and misalignment of the antennas significantly degrades performance. This poses a significant operational hurdle. Specifically, misalignment of the antennas results in a degradation of throughput.

[0006] The present invention has been made in view of the above points, and has an object to provide a technique that makes it possible to reduce degradation in throughput in OAM multiplex transmission. [Means for solving the problem]

[0007] According to the disclosed technology, there is provided a wireless communication system including a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, The receiving device performs channel estimation for each OAM mode based on the preamble transmitted from the transmitting device, and selects a combination of OAM modes to be used for transmission in the transmitting device based on the result of the channel estimation so as to maximize communication capacity. a wireless communication system, The receiving device performs channel estimation for only the positive OAM mode or only the negative OAM mode based on the symmetry of the channels in the positive and negative OAM modes of the same dimension, and uses the result of the performed channel estimation as the result of the channel estimation for the positive or negative OAM mode in which channel estimation was not performed. A wireless communication system is provided. [Effects of the Invention]

[0008] According to the disclosed technology, a technology is provided that makes it possible to reduce throughput degradation in OAM multiplexed transmission. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a wireless communication system according to an embodiment of the present invention. [Figure 2] 10A and 10B are diagrams illustrating phase differences given to each antenna element in each mode. [Figure 3] FIG. 2 is a functional configuration diagram of a transmitting device 100. [Figure 4] FIG. 2 is a functional configuration diagram of a receiving device 200. [Figure 5] FIG. 10 is a diagram illustrating a matrix of received power. [Figure 6] FIG. 2 is a sequence diagram illustrating the operation of the wireless communication system. [Figure 7] FIG. 10 is a configuration diagram of a modified example. [Figure 8] FIG. 2 illustrates an example of a hardware configuration of a mode selection device. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention (the present embodiment) will be described 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.

[0011] (Example of overall system configuration) An example of the overall configuration of a wireless communication system according to an embodiment of the present invention is shown in Fig. 1. As shown in Fig. 1, the wireless communication system according to this embodiment includes a transmitting device 100 and a receiving device 200.

[0012] The transmitting device 100 has an OAM mode generation function and a UCA. The receiving device 200 has an OAM mode separation function and a UCA. The transmitting device 100 multiplexes signals of one or more OAM modes and transmits them from the UCA. The receiving device 200 receives the signals multiplexed with one or more OAM modes transmitted from the transmitting device 100 using the UCA and separates each OAM mode.

[0013] In this embodiment, it is assumed that the transmitting device 100 and the receiving device 200 are stationary base stations, respectively, but this assumption is merely an example.

[0014] (OAM multiplex transmission) Here, the basic processing contents of the OAM multiplexing transmission performed by the transmitting device 100 and the receiving device 200 will be explained.

[0015] The OAM mode signal in the transmitting device 100 is generated by applying a phase difference based on a DFT transformation matrix to the signal supplied to each antenna element of the UCA. Specifically, the OAM mode n signal is generated by setting the phase difference supplied to each antenna element so that the phase rotates by n.

[0016] Figure 2 shows the phase difference applied to each antenna element in each mode when generating OAM mode signals using an eight-element UCA. For example, when generating OAM mode 2 signals using an eight-element UCA, the phase differences applied to each antenna element are 0 degrees, 90 degrees, 180 degrees, 270 degrees, 0 degrees, 90 degrees, 180 degrees, and 270 degrees clockwise. The number of multiplexed modes can be up to the same number as the number of antenna elements (for example, if the number of antenna elements is eight, eight modes: modes 0, 1, -1, 2, -2, 3, -3, and 4 can be used), but fewer modes are also possible.

[0017] To separate the OAM multiplexed signal in the receiving device 200, the phase of each antenna element of the UCA on the receiving side may be set to rotate in the opposite direction to the phase of the transmitting device 100.

[0018] (Summary of the problem and the process to solve it) As mentioned above, OAM multiplexing transmission has the problem of throughput degradation due to misalignment of the transmitting and receiving antennas.

[0019] To solve the above problem, in this embodiment, OAM mode selection and control are used to reduce throughput degradation caused by, for example, axis misalignment. Specifically, a known preamble is transmitted from transmitting device 100 for transmission and reception, and after receiving the preamble, receiving device 200 performs channel estimation based on the preamble. Based on the channel estimation result, receiving device 200 selects the OAM mode to use for transmission.

[0020] The above process allows the transmission OAM mode to be selected according to the channel state, taking into account interference caused by antenna misalignment, etc. As a result, degradation of throughput can be reduced.

[0021] The configuration and operation of the device for solving the above problems will be described in detail below.

[0022] (Device configuration example) Fig. 3 is a diagram showing an example of the functional configuration of the transmitting device 100 according to the present embodiment. As shown in Fig. 3, the transmitting device 100 includes a preamble generating unit 110, a mode multiplexing unit 120, and a UCA 130. Fig. 3 shows functional units related to preamble transmission among the components of the transmitting device 100. In addition to the components shown in Fig. 3, the transmitting device 100 may also include a function for generating and transmitting desired data.

[0023] Both the preamble generating unit 110 and the mode multiplexing unit 120 may be realized by a hardware circuit (digital circuit or analog circuit), or may be realized by causing a computer equipped with a CPU and memory to execute a program.

[0024] The preamble generation unit 110 generates, for each OAM mode, a signal sequence, such as an M sequence, that has a value ≠ 0 when autocorrelated and a value 0 when cross-correlated, as a preamble that is orthogonal between OAM modes. The preamble is an example of a known signal. The generated preamble is inserted (placed) discretely in the frequency direction, for example.

[0025] The mode multiplexing unit 120 multiplexes the preambles of each OAM mode into the corresponding OAM mode. The UCA 130 transmits the OAM wave into which the preambles are OAM-multiplexed.

[0026] 4 is a diagram showing an example of the functional configuration of the receiving device 200. The receiving device 200 includes a UCA 210, a mode separation unit 220, a channel estimation unit 230, a channel interpolation unit 240, a mode selection unit 250, and a mode notification unit 260.

[0027] The mode separation unit 220, the channel estimation unit 230, the channel interpolation unit 240, the mode selection unit 250, and the mode notification unit 260 may all be realized by a hardware circuit (a digital circuit or an analog circuit), or by causing a computer equipped with a CPU and memory to execute a program.

[0028] In receiving device 200, UCA 210 receives a signal (including a preamble). Mode separation unit 220 separates the signal into each OAM mode. Channel estimation unit 230 performs channel estimation for each OAM mode using the preamble for each OAM mode. Channel interpolation unit 240 calculates a channel estimate for a certain frequency by interpolation using channel estimates for adjacent frequencies.

[0029] Mode selection section 250 selects a combination of OAM modes to be used in transmitting device 100 based on the channel estimation results of each OAM mode, etc. Mode notification section 260 notifies transmitting device 100 of the OAM mode selected by mode selection section 250. Transmitting device 100 can perform transmission using the combination of OAM modes notified by mode notification section 260.

[0030] The channel estimation process and the mode selection process will be described in detail below. In the following description, the ^ in "^H" is intended to be the symbol written above the H.

[0031] (Channel estimation processing) First, the channel estimation process performed by the channel estimation unit 230 (and the channel interpolation unit 240) will be described.

[0032] Let the preamble vector be P(f+nΔf). Δf is the preamble insertion interval. f is the center frequency, but since the following description is in baseband, we will set f=0. n is an integer and is the value corresponding to the frequency position of the preamble. For example, if n is 1, 2, or 3, we can obtain channel estimates for each of the three frequency positions spaced apart by Δf.

[0033] If the channel matrix between the transmitting device 100 and the receiving device 200 is H(nΔf) and the noise vector is N(nΔf), the received preamble in the frequency domain is given below.

[0034] R(nΔf)=H(nΔf)P(nΔf)+N(nΔf) The channel response is obtained by calculating:

[0035] ^H(nΔf)=R(nΔf)P(nΔf) -1 The channel estimation unit 230 performs the calculation to obtain the above ^H(nΔf) for each frequency sampling (e.g., at intervals of Δf), thereby obtaining channel estimation values ​​at discrete points within the band used for communication. Note that information about the preamble (e.g., information about "time-frequency position, sequence for each OAM mode") is shared between the transmitting device 100 and the receiving device 200.

[0036] At this time, the transmitting side may thin out preambles to reduce the number of preambles inserted in the frequency direction. In this case, the channel interpolation unit 240 of the receiving device 200 performs the interpolation. For example, assume that the channel estimation unit 230 performs channel estimation at intervals of Δf, and the channel interpolation unit 240 obtains channel estimation values ​​at intervals of Δf / 2 through interpolation. In this case, the channel interpolation unit 240 performs the interpolation using the following equation:

[0037]

number

[0038] Regarding the channel estimation process, in more detail, channel estimation section 230 may perform channel estimation for each transmission OAM mode for each OAM mode (each reception OAM mode) separated by mode separation section 220. Which preamble corresponds to which transmission OAM mode can be identified by the preamble sequence.

[0039] (OAM mode selection process) Next, a process executed by mode selection section 250 to select a combination of OAM modes that maximizes communication capacity will be described.

[0040] The mode selection unit 250 uses the channel estimation value (^H) obtained by the channel estimation unit 230 to calculate the average received power using the following equation: In the following equation, N is the number of preambles inserted in the frequency direction.

[0041]

number

[0042] 6 is a flowchart of the OAM mode selection process, and the processing procedure will be described with reference to FIG.

[0043] <s101> In S101, the mode selection unit 250 obtains a power vector Pr by extracting diagonal elements from a received power matrix such as that shown in FIG.

[0044] <s102> In S102, mode selection section 250 selects the OAM mode of the maximum element among the elements of power vector Pr as OAM mode m that results in maximum received power.

[0045] <s103> In S103, mode selection unit 250 estimates the SINR for OAM mode m selected in S102, for example, from the constellation of an orthogonal preamble transmitted in advance. An example of a method for estimating the SINR will be described below. Note that the channel estimation unit 230 may also estimate (calculate) the SINR.

[0046] A preamble (for example, an M sequence) is modulated by QAM (Quadrature Amplitude Modulation) or the like and transmitted from transmitting device 100, and receiving device 200 receives the preamble. Mode selection section 250 calculates the SINR from the difference between a signal point known on the receiving side and a received signal point. For example, if a QAM-modulated transmitted signal is x(n) and a received signal is y(n), the SINR is calculated using the following formula. Note that calculating the SINR using the following formula is just an example, and the present invention is not limited to using the following formula.

[0047]

number

[0048] <S105、S106> The mode selection unit 250 adds the OAM mode m to the list of available modes and deletes the OAM mode m from the list of unused modes.

[0049] The initial value of the usage mode list is an empty vector, and the initial value of the unused mode list is a vector whose elements are all OAM modes that can be transmitted.

[0050] <S107、S108> Mode selection section 250 sets the number of selected modes i to i=1 and the number of mode decisions j to j=1.

[0051] <s109> The mode selection unit 250 selects the OAM mode that achieves the maximum received power from among the OAM modes remaining in the unused mode list.

[0052] More specifically, in S109, mode selection unit 250 sorts the received power of the OAM modes in power vector Pr remaining in the unused mode list in descending order, and selects the j-th OAM mode from the list obtained by sorting in descending order. The OAM mode selected here may also be called an additional candidate mode.

[0053] <s110> In S110, mode selection section 250 calculates the SINR of the j-th OAM mode from the top of the list, which was selected in S109.

[0054] <s111> In S111, the mode selection unit 250 calculates the SINR of each OAM mode in the current usage mode list.

[0055] <s112> The mode selection unit 250 selects a communication capacity C i For example, suppose the OAM mode candidate selected in S109 is OAM mode 1, and the OAM modes in the current usage mode list are OAM mode 2 and OAM mode 3. In this case, suppose the SINRs of OAM modes 1, 2, and 3 are calculated as SINR1, SINR2, and SINR3, respectively, in S110 and S111.

[0056] For example, by calculating the communication capacity using the Shannon base described above, the communication capacities of SINR1, 2, and 3 are calculated as "B log2(1+SINR1)", "B log2(1+SINR2)", and "B log2(1+SINR3)", respectively. In this case, the mode selection unit 2509 calculates the communication capacity C i is the sum of the communication capacities of each OAM mode, i =(B·log2(1+SINR1))+(B·log2(1+SINR2)+(B·log2(1+SINR3))).

[0057] <s113> In S113, the mode selection unit 250 selects "C i >C i-1 In other words, it is determined whether the communication capacity when the OAM mode is added will exceed the communication capacity before the OAM mode is added. If the determination result is Yes, proceed to S114, and if No, proceed to S119.

[0058] In this flow, because there is interference between OAM modes, the SINR is recalculated and the communication capacity is determined each time the OAM mode combination is updated. For example, adding an OAM mode that has significant interference with other OAM modes may reduce the overall communication capacity of the combined OAM modes.

[0059] <S114、S115> If the communication capacity after adding the OAM mode exceeds the communication capacity before adding the OAM mode, in S114, the mode selection unit 250 selects the OAM mode (m j ) to the list of available modes.

[0060] Also, in S115, the mode selection unit 250 deletes the OAM mode that was added to the usage mode list from the unused mode list.

[0061] <S116~S120> Let L be the number of all transmittable OAM modes. If i=L in S116, proceed to S117. If i=L in S116, then set i=i+1 in S118 and return to S108.

[0062] No (C i ≦C i-1 In S119, where i+j=L, mode selection section 250 determines whether i+j=L, and if Yes, proceeds to S117, and if No, sets j=j+1 in S120 and returns to S109. As a result, S110 to S113 are performed with the OAM mode with the next highest received power after the previous OAM mode selected as a candidate for addition as a new candidate mode for addition.

[0063] If all OAM modes are added to the usage mode list through the above flow, or if it is determined that adding any of the OAM modes among all the candidate modes to be added will not increase communication capacity, the algorithm ends and proceeds to S117.

[0064] In S117, the mode notification unit 260 feeds back the usage mode list to the transmitting device 100. The transmitting device 100 determines the OAM mode to be used for transmission based on the usage mode list.

[0065] (Variation) The "mode selection unit 250 and mode notification unit 260" in the receiving device 200 shown in Fig. 4 may be provided outside the receiving device 200. The "mode selection unit 250 and mode notification unit 260" provided outside may be called a mode selection device 300.

[0066] 7 shows an example of a wireless communication system in which a mode selection device 300 is provided external to a receiving device 200. The mode selection device 300 performs the mode selection and feedback processes described above by communicating with the transmitting device 100 and the receiving device 200 via a network 400. The network 400 may be a small-scale network such as a LAN or an interface line between devices, or may be a wide-area network such as the Internet, a dedicated line, or a VPN.

[0067] The mode selection unit 250 (or the mode selection unit 250 and the mode notification unit 260) provided inside the receiving device 200 may be called a mode selection device. Also, the mode selection unit 300 provided outside the receiving device 200 may be called a mode selection unit.

[0068] (Example of hardware configuration) The mode selection device described in this embodiment can be realized, for example, by causing a computer to execute a program. This computer may be a physical computer or a virtual machine on the cloud.

[0069] That is, the mode selection device can be realized by using hardware resources such as a CPU and memory built into a computer to execute a program corresponding to the processing performed by the mode selection device. The program can be recorded on a computer-readable recording medium (such as a portable memory) and stored or distributed. The program can also be provided via a network such as the Internet or email.

[0070] Fig. 8 is a diagram showing an example of the hardware configuration of the computer. The computer in Fig. 8 includes a drive device 1000, an auxiliary storage device 1002, a memory device 1003, a CPU 1004, an interface device 1005, a display device 1006, an input device 1007, an output device 1008, and the like, all of which are interconnected by a bus BS. The computer may further include a GPU.

[0071] A program for realizing processing on the computer is provided by a recording medium 1001 such as a CD-ROM or a memory card. When the recording medium 1001 storing the program is set in the drive device 1000, the program is installed from the recording medium 1001 to the auxiliary storage device 1002 via the drive device 1000. However, the program does not necessarily have to be installed from the recording medium 1001, but may be downloaded from another computer via a network. The auxiliary storage device 1002 stores the installed program as well as necessary files, data, etc.

[0072] The memory device 1003 reads and stores the program from the auxiliary storage device 1002 when an instruction to start the program is received. The CPU 1004 realizes functions related to the mode selection device in accordance with the program stored in the memory device 1003. The interface device 1005 is used as an interface for connecting to a network, etc. The display device 1006 displays a GUI (Graphical User Interface) or the like according to the program. The input device 1007 is composed of a keyboard, mouse, buttons, a touch panel, etc., and is used to input various operation instructions. The output device 1008 outputs the results of calculations.

[0073] (Summary of implementation form, effects, etc.) As described above, the technology described in this embodiment makes it possible to select a combination of transmission OAM modes according to the channel state, taking into consideration interference due to antenna axis misalignment, etc. As a result, it is possible to reduce degradation of throughput.

[0074] The following additional notes are provided regarding the above-described embodiments.

[0075] <Additional Notes> (Additional note 1) A wireless communication system comprising a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, The receiving device performs channel estimation for each OAM mode based on the preamble transmitted from the transmitting device, and selects a combination of OAM modes to be used for transmission in the transmitting device based on the result of the channel estimation so as to maximize communication capacity. Wireless communication system. (Additional note 2) The receiving device performs channel estimation for only the positive OAM mode or only the negative OAM mode based on the symmetry of the channels in the positive and negative OAM modes of the same dimension, and uses the result of the performed channel estimation as the result of the channel estimation for the positive or negative OAM mode in which channel estimation was not performed. Item 1. A wireless communication system according to claim 1. (Additional note 3) The transmitting device does not transmit a preamble for an OAM mode in which channel estimation is not performed in the receiving device. Item 3. A wireless communication system according to claim 2. (Additional note 4) The receiving device calculates a channel estimation value at a frequency at which channel estimation is not performed by interpolation from the results of channel estimation performed at frequencies adjacent to the frequency at which channel estimation is not performed. 4. A wireless communication system according to any one of claims 1 to 3. (Additional note 5) The receiving device evaluates communication capacity while updating the combination of OAM modes based on the received power in each OAM mode, and determines the combination of OAM modes that maximizes communication capacity. 5. A wireless communication system according to any one of claims 1 to 4. (Additional note 6) 1. An OAM mode selection method executed in a wireless communication system including a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, The receiving device performs channel estimation for each OAM mode based on the preamble transmitted from the transmitting device, and selects a combination of OAM modes to be used for transmission in the transmitting device based on the result of the channel estimation so as to maximize communication capacity. OAM mode selection method. (Additional note 7) A receiving device usable in a wireless communication system including a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, a channel estimation unit that performs channel estimation for each OAM mode based on the preamble transmitted from the transmitting device; a mode selection unit that selects a combination of OAM modes to be used for transmission in the transmitting device based on a result of the channel estimation so as to maximize communication capacity; A receiving device comprising: (Additional note 8) The channel estimation unit performs channel estimation for only the positive OAM mode or for only the negative OAM mode based on the symmetry of the channels in the positive and negative OAM modes of the same dimension, and uses the result of the performed channel estimation as the result of the channel estimation for the positive or negative OAM mode in which channel estimation was not performed. 8. A receiving device according to claim 7.

[0076] Although the present embodiment has been described above, the present invention is not limited to such a specific embodiment, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims. [Explanation of symbols]

[0077] 100 Transmitting device 110 Preamble generator 120 Mode multiplexing section 130 UCA 200 receiving device 210 UCA 220 Mode Separation Section 230 Channel Estimation Unit 240 channel interpolation unit 250 Mode selection section 260 Mode notification section 300 Mode Selector 400 Network 1000 Drive Device 1001 Recording media 1002 Auxiliary storage 1003 Memory device 1004 CPU 1005 Interface device 1006 Display device 1007 Input Device 1008 Output Device

Claims

1. A wireless communication system comprising a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, a wireless communication system in which the receiving device performs channel estimation for each OAM mode based on a preamble transmitted from the transmitting device, and selects a combination of OAM modes to be used for transmission in the transmitting device based on a result of the channel estimation so as to maximize communication capacity; The receiving device performs channel estimation for only the positive OAM mode or only the negative OAM mode based on the symmetry of the channels in the positive and negative OAM modes of the same dimension, and uses the result of the performed channel estimation as the result of the channel estimation for the positive or negative OAM mode in which channel estimation was not performed. Wireless communication system.

2. The transmitting device does not transmit a preamble in an OAM mode in which channel estimation is not performed in the receiving device.

10. The wireless communication system of claim 1.

3. The receiving device calculates a channel estimation value at a frequency at which channel estimation is not performed by interpolation from the results of channel estimation performed at frequencies adjacent to the frequency at which channel estimation is not performed.

3. The wireless communication system according to claim 1 or 2.

4. A wireless communication system comprising a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, a wireless communication system in which the receiving device performs channel estimation for each OAM mode based on a preamble transmitted from the transmitting device, and selects a combination of OAM modes to be used for transmission in the transmitting device based on a result of the channel estimation so as to maximize communication capacity; The receiving device evaluates communication capacity while updating the combination of OAM modes based on the received power in each OAM mode, and determines the combination of OAM modes that maximizes communication capacity. Wireless communication system.

5. 1. An OAM mode selection method executed in a wireless communication system including a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, comprising: an OAM mode selection method in which the receiving device performs channel estimation for each OAM mode based on a preamble transmitted from the transmitting device, and selects a combination of OAM modes to be used for transmission in the transmitting device based on a result of the channel estimation so as to maximize communication capacity; The receiving device performs channel estimation for only the positive OAM mode or only the negative OAM mode based on the symmetry of the channels in the positive and negative OAM modes of the same dimension, and uses the result of the performed channel estimation as the result of the channel estimation for the positive or negative OAM mode in which channel estimation was not performed. OAM mode selection method.

6. 1. An OAM mode selection method executed in a wireless communication system including a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, comprising: an OAM mode selection method in which the receiving device performs channel estimation for each OAM mode based on a preamble transmitted from the transmitting device, and selects a combination of OAM modes to be used for transmission in the transmitting device based on a result of the channel estimation so as to maximize communication capacity; The receiving device evaluates communication capacity while updating the combination of OAM modes based on the received power in each OAM mode, and determines the combination of OAM modes that maximizes communication capacity. OAM mode selection method.

7. A receiving device usable in a wireless communication system including a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, a channel estimation unit that performs channel estimation for each OAM mode based on a preamble transmitted from the transmitting device; a mode selection unit that selects a combination of OAM modes to be used for transmission in the transmitting device based on a result of the channel estimation so as to maximize communication capacity; The channel estimation unit performs channel estimation for only the positive OAM mode or for only the negative OAM mode based on the symmetry of the channels in the positive and negative OAM modes of the same dimension, and uses the result of the performed channel estimation as the result of the channel estimation for the positive or negative OAM mode in which channel estimation was not performed. Receiving device.

8. A receiving device usable in a wireless communication system including a transmitting device that transmits an OAM multiplexed signal and a receiving device that receives the OAM multiplexed signal, a channel estimation unit that performs channel estimation for each OAM mode based on a preamble transmitted from the transmitting device; a mode selection unit that selects a combination of OAM modes to be used for transmission in the transmitting device based on a result of the channel estimation so as to maximize communication capacity; The mode selection unit evaluates communication capacity while updating the combination of OAM modes based on the received power in each OAM mode, and determines the combination of OAM modes that maximizes communication capacity. Receiving device.

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