Wireless communication system, communication method, and receiving device

Abstract

A wireless communication system comprising a transmission device provided with a transmission UCA and a reception device provided with a reception UCA, wherein the reception device receives, by the reception UCA, an OAM multiplexed signal transmitted from the transmission device and a MIMO multiplexed signal transmitted from a transmission terminal.

Description

[Technical Field]

[0001] The present invention relates to a technique for spatially multiplexing and transmitting wireless signals using the orbital angular momentum (OAM) of electromagnetic waves. [Background technology]

[0002] In recent years, in order to improve transmission capacity, spatial multiplexing transmission technology for wireless signals using OAM has been studied (for example, Non-Patent Document 1). Electromagnetic waves with OAM have equiphase planes distributed in a spiral shape 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, so signals can be multiplexed and transmitted 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 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.

[0004] Furthermore, as a form of PtMP (Point-to-Multipoint) transmission in future wireless communications, a technology has been proposed that simultaneously accommodates a main line (backbone line) that performs large-capacity communications, such as an FPU (Field Pickup Unit) or an IAB (Integrated access and backhaul), and a best-effort secondary line (terminal line). For example, Non-Patent Document 3 considers a method for eliminating interference between users by performing MIMO equalization processing on all users at the receiving station in order to realize PtMP transmission using general MIMO technology.

[0005] Furthermore, Non-Patent Document 4 proposes resource control for downstream transmission of the PtMP transmission, but does not mention upstream transmission. [Prior art documents] [Non-patent literature]

[0006] [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. [Non-patent document 3] Shengchu Wang, et. al., "Multiuser Detection in massive spatial modulation MIMO with low-resolution ADCs," IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 14, NO. 4, APRIL 2015 [Non-patent document 4] T. Kageyama, et.al., "A PtMP downlink transmission using OAM multiplexing with prioritized resource-control," IEICE Communications Express, vol.11, no.9, pp.577-582, June 2022. Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, a transmitter using UCA and a Butler circuit enables high-capacity communications, but in the future, multi-directional support is desired. However, conventional wireless transmission technologies use MIMO technology to achieve PtMP transmission, which poses a problem of the heavy computational load of MIMO equalization as the number of users or spatial streams increases.

[0008] 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 the computational load in PtMP transmission. [Means for solving the problem]

[0009] According to the disclosed technology, there is provided a wireless communication system including a transmitting device having a transmitting UCA and a receiving device having a receiving UCA, The receiving device receives the OAM multiplexed signal transmitted from the transmitting device and the MIMO multiplexed signal transmitted from the transmitting terminal by the receiving UCA. a wireless communication system, The receiving device performing MIMO equalization reception on a signal on a second line between the transmitting terminal and the receiving device using only an OAM mode that is not used on a first line between the transmitting device and the receiving device; For the signal on the first line, OAM reception is performed using the OAM mode used on the first line. A wireless communication system is provided. [Effects of the Invention]

[0010] The disclosed technology provides a technology that makes it possible to reduce the computational load in PtMP transmission. [Brief explanation of the drawings]

[0011] [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 transmitting terminal 300. [Figure 5] FIG. 2 is a functional configuration diagram of a receiving device 200. [Figure 6] FIG. 2 is a sequence diagram illustrating the operation of the wireless communication system. [Figure 7] FIG. 1 is a diagram illustrating a specific example of communication in a wireless communication system. [Figure 8] FIG. 10 is a configuration diagram of a modified example. [Figure 9] FIG. 2 is a diagram illustrating an example of a hardware configuration of an allocation mode determination device. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[0013] (Example of overall system configuration) An example of the overall configuration of a wireless communication system according to the present embodiment is shown in Fig. 1. As shown in Fig. 1, the wireless communication system according to the present embodiment includes a transmitting device 100, a receiving device 200, and a transmitting terminal 300. Although one transmitting terminal 300 is shown in Fig. 1, there may be a plurality of transmitting terminals 300.

[0014] The transmitting device 100 has an OAM mode generation function and a UCA (which may also be called a transmitting UCA). The receiving device 200 has an OAM mode separation function and a UCA (which may also be called a receiving UCA). The transmitting device 100 multiplexes signals of one or more OAM modes and transmits them from the UCA, and the receiving device 200 receives the signals transmitted from the transmitting device 100, in which one or more OAM modes are multiplexed, using the UCA, and separates each OAM mode.

[0015] In this embodiment, it is assumed that the transmitting device 100 and the receiving device 200 are stationary base stations, respectively, but this is just an example.

[0016] The transmitting terminal 300 is, for example, a mobile terminal such as a smartphone. The transmitting terminal 300 has one or more antennas and is capable of performing multi-user MIMO multiplexing communication. The transmitting terminal 300 may also have a UCA.

[0017] Note that "transmission" by the transmitting device 100 means transmitting desired data, and in communication for control, the transmitting device 100 may perform reception. "Reception" by the receiving device 200 means receiving desired data, and in communication for control, the receiving device 200 may perform transmission. "Transmission" by the transmitting terminal 300 means transmitting desired data, and in communication for control, the transmitting terminal 300 may perform reception.

[0018] (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.

[0019] 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 n times (n × 360 degrees).

[0020] Figure 2 shows the phase difference applied to each antenna element in each mode when generating an OAM mode signal using an eight-element UCA. For example, when generating an OAM mode n=2 signal using an eight-element UCA, a phase difference of 360n / m=90 degrees clockwise is set for each antenna element (0 degrees, 90 degrees, 180 degrees, 270 degrees, 0 degrees, 90 degrees, 180 degrees, 270 degrees) so that the phase rotates twice.

[0021] Note that a signal with the phase rotation direction reversed to that of an OAM mode n signal is called OAM mode -n. For example, the phase rotation direction of a positive OAM mode signal is clockwise, and the phase rotation direction of a negative OAM mode signal is counterclockwise.

[0022] Spatial multiplexing wireless communication can be performed by generating different signal sequences as signals in different OAM modes and transmitting the generated signals simultaneously. On the transmitting side, signals to be transmitted in each OAM mode can be generated and combined in advance and the combined signal for each OAM mode can be transmitted using a single UCA, or multiple UCAs can be used to transmit signals for each OAM mode using different UCAs for each OAM mode.

[0023] In order to separate the OAM multiplexed signal in the receiving device 200, the phase of each antenna element of the UCA in the receiving device 200 may be set to be opposite to the phase of the antenna element in the transmitting device 100.

[0024] However, if interference occurs between OAM modes due to an axis misalignment between the transmitting antenna and the receiving antenna, it becomes necessary to separate the OAM mode signals mixed due to interference by digital signal processing such as channel equalization processing and successive interference cancellation processing. Note that interference between OAM modes means, for example, that a signal transmitted from transmitting device 100 in OAM mode 1 is output by receiving device 200 as a signal in OAM mode 2.

[0025] In the wireless communication system of this embodiment, communication between transmitting device 100 and receiving device 200 is defined as backhaul communication, and communication between transmitting terminal 300 and receiving device 200 is defined as access communication. Furthermore, the line between transmitting device 100 and receiving device 200 is called a backhaul line, and the line between transmitting terminal 300 and receiving device 200 is called an access line. The backhaul line may also be called a trunk line. Note that the names "backhaul" and "access" are merely examples.

[0026] (Summary of the problem and the process to solve it) As mentioned above, the conventional technology has a problem in that the computational load required to realize PtMP transmission is large.

[0027] In order to solve the above problems, in this embodiment, a feature of OAM is that there is no interference from the backhaul line to the access line, and by partially suppressing only the interference from the access line to the backhaul line, the amount of equalization calculation processing required to remove inter-mode interference on the backhaul line is reduced compared to the processing amount required for conventional MIMO processing, while ensuring the communication capacity of the backhaul line.

[0028] Furthermore, as will be described later, the communication capacity of the transmitting terminal 300 can be maximized by selecting a mode based on a feedback value of the received SINR (Signal to Interference and Noise power Ratio).

[0029] The configuration and operation of the device for solving the above problems will be described in detail below.

[0030] (Device configuration example) 3 is a diagram showing an example of a functional configuration of the transmitting apparatus 100 according to the present embodiment. As shown in FIG. 3, the transmitting apparatus 100 includes a data generating unit 110, a modulating unit 120, a mode multiplexing unit 130, a mode assigning unit 140, an SINR calculating unit 160, and a UCA 150.

[0031] The data generation unit 110, the modulation unit 120, the mode multiplexing unit 130, the mode allocation unit 140, and the SINR calculation unit 160 may all be realized by a hardware circuit (a digital circuit or an analog circuit), or by causing a computer having a CPU and a memory to execute a program. The SINR calculation unit 160 may also be provided outside the transmitting device 100.

[0032] The data generator 110 generates a bit string of transmission data. The modulator 120 modulates the transmission data using a modulation method such as QAM (Quadrature Amplitude Modulation). The mode assigner 140 instructs the mode multiplexer 130 on the OAM mode in which the transmitter 100 will transmit, based on feedback from the receiver 200. The mode multiplexer 130 converts the modulated signal into an OAM wave using the OAM mode instructed by the mode assigner 140. The UCA 150 transmits the OAM wave.

[0033] The SINR calculation unit 160 has a function of receiving a preamble for each OAM mode transmitted from the receiving device 200 , calculating the reception SINR for each OAM mode, and feeding back the calculated reception SINR to the receiving device 200 .

[0034] 4 is a diagram showing an example of the functional configuration of transmitting terminal 300. Transmitting terminal 300 includes a data generating unit 310, a modulating unit 320, a precoding unit 330, an SINR calculating unit 350, and an antenna 340. Data generating unit 310, modulating unit 320, precoding unit 330, and SINR calculating unit 350 may all be realized by a hardware circuit (a digital circuit or an analog circuit), or may be realized by causing a computer equipped with a CPU and memory to execute a program.

[0035] The data generation unit 310 generates a bit string of transmission data. The modulation unit 320 modulates the transmission data. The precoding unit 330 weights the modulated signal generated by the modulation unit 320. The weighting by the precoding unit 330 may also be expressed as precoding. The antenna 340 is composed of one or more antennas, and transmits a weighted signal (MIMO multiplexed signal).

[0036] The SINR calculation unit 350 has a function of receiving a preamble for each OAM mode transmitted from the receiving device 200 , calculating the reception SINR for each OAM mode, and feeding back the calculated reception SINR to the receiving device 200 .

[0037] 5 is a diagram showing an example of the functional configuration of receiving apparatus 200. Receiving apparatus 200 includes UCA 210, mode separation section 220, MIMO equalization section 230, interference replica generation section 240, interference subtraction section 250, demodulation section 260, allocation mode calculation section 270, feedback section 280, and preamble transmission section 290. Preamble transmission section 290 may be provided outside receiving apparatus 200.

[0038] The mode separation unit 220, the MIMO equalization unit 230, the interference replica generation unit 240, the interference subtraction unit 250, the demodulation unit 260, the allocation mode calculation unit 270, the feedback unit 280, and the preamble transmission unit 290 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.

[0039] The mode separation unit 220 separates the signal received by the UCA 210 into each OAM mode. The MIMO equalization unit 230 performs MIMO equalization only on the OAM mode corresponding to the signal from the transmitting terminal 300. The interference replica generation unit 240 generates a replica of the interference signal to be applied to the signal from the transmitting device 100, from the MIMO equalized signal. The interference subtraction unit 250 subtracts the interference replica from the signal from the transmitting device 100. The demodulation unit 260 demodulates the signal from which interference has been subtracted by the interference subtraction unit 250 into bit data.

[0040] The reception process for performing MIMO equalization may be called MIMO equalization reception, and the reception process for separating each OMA mode may be called OAM reception.

[0041] (Example of operation) Next, a specific example of operation in the wireless communication system according to this embodiment will be described.

[0042] In this wireless communication system, backhaul communication and access communication are spatially multiplexed at the same time and frequency. Interference occurs between backhaul communication and access communication, which must be eliminated. Specifically, interference does not occur between OAM modes used in backhaul communication, and interference does not occur from the OAM mode used in backhaul communication to the OAM mode used in the access line. However, interference does occur from the OAM mode used in the access line to the OAM mode used in backhaul communication. Generally, interference is suppressed by MIMO equalization processing, but the amount of calculation increases as the number of OAM modes used by transmitting device 100 and the number of transmitting terminals transmitting over the access line increase.

[0043] In this embodiment, the orthogonality of OAM waves is utilized, MIMO equalization is performed only within access communication, and interference subtraction processing is applied, thereby reducing the amount of calculation required for interference suppression (interference reduction).

[0044] A specific processing procedure will be described with reference to Fig. 6. Fig. 6 is a sequence diagram showing an example of the operation of the wireless communication system according to this embodiment.

[0045] <s101> In S101, preamble transmission unit 290 in receiving device 200 transmits a preamble for each OAM mode. The preambles for each OAM mode are orthogonal to each other between the OAM modes. An orthogonal sequence such as an M sequence is used as the preamble. The preamble may also be called a known signal.

[0046] SINR calculation section 160 of transmitting device 100 receives the preamble of each OAM mode transmitted from receiving device 200. SINR calculation section 350 of transmitting terminal 300 also receives the preamble of each OAM mode transmitted from receiving device 200.

[0047] <S102、S103> In S102, SINR calculation unit 160 of transmitting device 100 calculates the SINR of each OAM mode from the received preamble. Similarly, in S103, SINR calculation unit 350 of transmitting terminal 300 calculates the SINR of each OAM mode from the received preamble.

[0048] The SINR calculation unit 160 / SINR calculation unit 350 calculates the SINR from the difference between a signal point known on the receiving side (device 100 / transmitting terminal 300) and a received signal point. For example, if the transmitted signal subjected to QAM modulation is x(n) and the received signal is y(n), the SINR can be calculated as follows:

[0049]

number

[0050] <s106> In S106, the allocation mode determination unit 270 in the receiving device 200 determines the OAM mode to be used by the transmitting device 100 and the OAM mode to be used by the transmitting terminal 300 based on the SINR received from the transmitting device 100 and the SINR received from the transmitting terminal 300.

[0051] For example, allocation mode determination unit 270 allocates to transmitting terminal 300 one or more OAM modes that maximize the SINR of transmitting terminal 300 while ensuring a required transmission rate in backhaul communication, and allocates other OAM modes to transmitting device 100. The method for performing such allocation is not limited to a specific method, but allocation can be performed, for example, by the following method.

[0052] Here, the received SINR for mode n is n From this, communication capacity C n C n =B·log2(1+SINR n The allocation mode determination unit 270 calculates the threshold C th Determine the combination of usage modes that exceeds the communication capacity threshold C th is a predetermined threshold value. Regarding the communication capacity, for example, when mode 1 and mode 2 are used in combination, the communication capacity is "C1+C2".

[0053] A specific example will be described. Assume that a total of OAM modes, modes 0 to ±4, are prepared. Assume that allocation mode determination unit 270 determines that combination 1: modes 0, 1, 2, 3, -3, 4 and combination 2: modes 1, -1, 2, -2, 3, -3, 4, exceed the threshold, respectively, in the backhaul line. In this case, the modes that transmitting terminal 300 can use are "modes -1, -2, -4" for combination 1, which are not used in combination 1, and "modes 0, -4" for combination 2, which are not used in combination 2.

[0054] Hereinafter, combination 1 will be defined as "backhaul line: modes 0, 1, 2, 3, -3, 4, access line: modes -1, -2, -4", and combination 2 will be defined as "backhaul line: modes 1, -1, 2, -2, 3, -3, 4, access line: modes 0, -4".

[0055] The allocation mode determination unit 270 selects the combination from combination 1 and combination 2 that maximizes the received SINR of the transmitting terminal 300, and allocates to the transmitting terminal 300 the OAM mode of the access line included in the selected combination.

[0056] For example, for modes -1, -2, and -4 of the access line of combination 1, the received SINR is -1 , received SINR -2 , received SINR -4 For modes 0 and -4 of the access line in combination 2, the respective received SINRs are as received SINR0, received SINR -4 Let's say.

[0057] At this time, the allocation mode determination unit 270 selects a combination including a mode that maximizes the reception SINR of the transmitting terminal 300. For example, if the transmitting terminal 300 maximizes the reception SINR in mode 1, combination 1 is used. Also, if the transmitting terminal 300 can use multiple modes, and up to three modes are available, the "reception SINR" is selected. -1 +Received SINR -2 +Received SINR -4 " and "Received SINR0 + Received SINR -4 " Select the larger combination.

[0058] If there are multiple transmitting terminals, at least one OAM mode is assigned to each transmitting terminal. For example, if there are two transmitting terminals, there are six allocation patterns in combination 1, and two allocation patterns in combination 2. In this case, allocation mode determination unit 270 calculates the frequency utilization efficiency (bit / s / Hz) from the received SINR of each transmitting terminal according to the following formula, and assigns the OAM modes so that the sum is maximized.

[0059] C i n =log2(1+SINR n ) Here, n is the index of the mode, and i is the index of the transmitting terminal. i C i n The allocation is performed using the allocation pattern that maximizes Σ i represents the summation for the transmitting terminal.

[0060] <S107、S108> Feedback section 280 of receiving device 200 notifies each of transmitting terminal 300 and transmitting device 100 of the usage modes according to the combination of usage modes determined in S106. For example, if combination 1 is determined as the allocation mode in S106, feedback section 280 notifies transmitting device 100 of "modes 0, 1, 2, 3, -3, 4" and notifies transmitting terminal 300 of any one or more or all of "modes -1, -2, -4".

[0061] Regarding the mode notification to transmitting terminal 300, if there is one transmitting terminal 300, for example, the mode with the largest SINR from "modes -1, -2, -4" may be notified to that transmitting terminal 300.

[0062] Also, for example, if there are three transmitting terminals 300, each transmitting terminal 300 may be notified of one of "mode-1, -2, -4."

[0063] <S109,S110> In S109, the mode allocation unit 140 of the transmitting device 100 allocates the mode notified by the feedback unit 280 of the receiving device 100 to the mode multiplexing unit 130. In S110, the transmitting device 100 multiplexes the transmission data in the mode allocated to the mode multiplexing unit 130, and transmits the transmission data from the UCA 150 as an OAM wave.

[0064] <S111、S112> The transmitting terminal 300 transmits weighted (precoded) MIMO transmission signals using any antenna arrangement (not limited to UCA). The weights at this time are determined by multiplying the channel and OAM separation vector (or OAM separation matrix) for the mode notified to the transmitting terminal 300 by the feedback unit 280, and using the Hermitian transpose matrix for this as the pseudo channel. Specifically, this is as follows. In the following explanation, the ^ in "^H" is intended to be the symbol written above the H.

[0065] In S111, the precoding unit 330 of the transmitting terminal 300 calculates a precoder corresponding to the mode notified by the feedback unit 280 of the receiving device 100. The precoding unit 330 uses, for example, an MRC (Maximum ratio combining) matrix as the precoder. An example of deriving the precoder will be described below.

[0066] Here, an example will be described in which transmitting terminal 300 uses one mode notified by feedback section 280. Note that transmitting terminal 300 can also use multiple modes notified by feedback section 280.

[0067] Let H be the channel matrix between transmitting terminal 300 and receiving device 200. Here, H is a complex matrix of the number of antennas of transmitting terminal 300 × the number of antennas of receiving device 200. Regarding the number of antennas of receiving device 200, for example, if receiving device 200 is equipped with the UCA shown in FIG. 2, the number of antennas of receiving device 200 is eight.

[0068] Let D be the OAM separating vector for the OAM signal for the mode notified to transmitting terminal 300. D is a matrix of 1× the number of antennas in receiving apparatus 200, and is a matrix that generates the OAM mode assigned to transmitting terminal 300. Precoding section 330 of transmitting terminal 300 estimates a channel matrix using the preamble for the mode notified to transmitting terminal 300, which is transmitted from preamble transmitting section 290 of receiving apparatus 200. If the estimated channel matrix is ​​^H, precoding section 330 of transmitting terminal 300 calculates precoder W using the following equation. H represents the Hermitian transpose.

[0069] W=(^HD) H In S111, the transmitting terminal 300 performs precoding on the modulated transmission data using the precoder, and in S112, transmits the precoded signal from the antenna 340.

[0070] <s113> In S113, receiving device 200 performs receiving processing. In explaining the receiving processing, a specific example of communication will be explained with reference to Fig. 7. Fig. 7 is a diagram showing an example of a case where backhaul communication and access communication are performed using OAM modes 0 to ±4. Here, the number of transmitting terminals 300 is two, and the two transmitting terminals 300 are transmitting terminal 300_1 and transmitting terminal 300_2.

[0071] In the example of Fig. 7, as a result of mode allocation, the transmitting device 100 transmits data using modes 0, 1, -1, -2, and -3, the transmitting terminal 300_1 transmits data using mode 2, and the transmitting terminal 300_2 transmits data using mode 3. On the transmitting device 100 side in Fig. 7, the modes enclosed in parentheses indicate that they are not in use.

[0072] In the receiving device 200, the mode separation unit 220 separates the signals into each OAM mode, and then classifies the separated signals into a signal of the transmitting device 100 and signals of two transmitting terminals 300. Since the transmitting device 100 and the receiving device 200 are installed opposite each other, interference between modes does not occur for the signal transmitted from the transmitting device 100 due to the characteristics of OAM. Furthermore, interference from the mode of the transmitting device 100 to the modes of the transmitting terminals 300_1 and 300_2 does not occur. On the other hand, interference from the modes of the transmitting terminals 300_1 and 300_2 to the mode of the transmitting device 100, interference from the transmitting terminal 300_1 to the transmitting terminal 300_2, and interference from the transmitting terminal 300_2 to the transmitting terminal 300_1 do occur. Below, a process for suppressing this interference will be described. It is assumed that the following process for "transmitting terminal 300" is executed for each transmitting terminal.

[0073] In the receiving device 200, the mode separation unit 220 extracts only the signal of the mode of the transmitting terminal 300 and provides it to the MIMO equalization unit 230. The MIMO equalization unit 230 performs interference suppression by MIMO equalization processing. For example, MMSE (Minimum Mean Square Error) is used for the MIMO equalization. As a result, interference between the transmitting terminal 300_1 and the transmitting terminal 300_2 is suppressed.

[0074] Next, interference replica generation unit 240 uses the signal of transmitting terminal 300 that has been MIMO equalized to generate a replica of the interference signal that the signal in the mode of transmitting terminal 300 causes to the signal in the mode of transmitting apparatus 100. The method of generating the replica is not limited to a specific method, but the replica can be generated by the following method, for example.

[0075] If the received signal from transmitting terminal 300 is d, the precoder of transmitting terminal 300 is W, the channel estimation value between transmitting terminal 300 and receiving device 200 is ^H, and the OAM mode separation vector is D, the replica of the interference signal that transmitting terminal 300 applies to the backhaul line is calculated using the following equation.

[0076] y=D^HWd The replica generated by the interference replica generation unit 240 is passed to the interference subtraction unit 250. The interference subtraction unit 250 subtracts the replica from the signal of the transmitting device 100, thereby suppressing interference from the mode of the transmitting terminal 300 to the mode of the transmitting device 100.

[0077] By the above processing, the amount of calculation required for equalization processing can be reduced compared to when MIMO equalization is performed between all modes.

[0078] (Variation) 5 may be provided outside the receiving device 200. The externally provided "allocation mode determination unit 270 and feedback unit 280" may be referred to as an allocation mode determination device 400.

[0079] 8 shows an example of a wireless communication system in which an allocation mode determination device 400 is provided outside the receiving device 200. The allocation mode determination device 400 performs the mode allocation and feedback processing described above by communicating with the transmitting device 100, the receiving device 200, and the transmitting terminal 300 via a network 500. The network 500 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.

[0080] The allocation mode determination unit 270 (or the allocation mode determination and feedback unit 280) provided inside the receiving device 200 may be called an allocation mode determination device. Also, the allocation mode determination device 400 provided outside the receiving device 200 may be called an allocation mode determination unit.

[0081] (Example of hardware configuration) The allocation mode determination 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 a cloud.

[0082] That is, the allocation mode determination device can be realized by executing a program corresponding to the processing performed by the allocation mode determination device using hardware resources such as a CPU and memory built into a computer. 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.

[0083] Fig. 9 is a diagram showing an example of the hardware configuration of the computer. The computer in Fig. 9 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.

[0084] 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.

[0085] 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 allocation mode determination 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.

[0086] (Summary of implementation form, effects, etc.) As described above, in this embodiment, by utilizing the feature of OAM that there is no interference from the backhaul line to the access line, and by partially suppressing interference from the access line to the backhaul line and interference within the access line, it is possible to ensure the communication capacity of the backhaul line while reducing the amount of equalization calculation processing required to remove inter-mode interference in the backhaul line compared to the processing amount in conventional MIMO processing.In addition, since mode selection is performed based on a feedback value of the received SINR, it is possible to maximize the communication capacity of the transmitting terminal 300.

[0087] The following additional notes are provided regarding the above-described embodiments.

[0088] <Additional Notes> (Additional note 1) A wireless communication system comprising a transmitting device having a transmitting UCA and a receiving device having a receiving UCA, The receiving device receives the OAM multiplexed signal transmitted from the transmitting device and the MIMO multiplexed signal transmitted from the transmitting terminal by the receiving UCA. Wireless communication system. (Additional note 2) and an allocation mode determination unit that allocates OAM modes to a first line between the transmitting device and the receiving device and a second line between the transmitting terminal and the receiving device so that there is no overlap between the first line and the second line. Item 1. A wireless communication system according to claim 1. (Additional note 3) The allocation mode determination unit Based on the reception SINR at the transmitting device and the reception SINR at the transmitting terminal, an OAM mode is assigned so as to maximize the reception SINR at the transmitting terminal while ensuring the communication capacity of the first line. Item 3. A wireless communication system according to claim 2. (Additional note 4) The receiving device performing MIMO equalization reception on the signal of the second line using only an OAM mode that is not used on the first line; For the signal on the first line, OAM reception is performed using the OAM mode used on the first line. 4. The wireless communication system according to claim 2 or 3. (Additional note 5) The receiving device an interference replica generation unit that generates an interference replica from the second line to the first line using a channel estimation value in the second line; an interference subtraction unit that subtracts the interference replica from the received signal of the first line; 5. The wireless communication system according to claim 2, further comprising: (Additional note 6) A communication method performed in a wireless communication system including a transmitting device having a transmitting UCA and a receiving device having a receiving UCA, The receiving device receives the OAM multiplexed signal transmitted from the transmitting device and the MIMO multiplexed signal transmitted from the transmitting terminal by the receiving UCA. Communication method. (Additional note 7) A receiving device usable in a wireless communication system including a transmitting device having a transmitting UCA and a receiving device having a receiving UCA, The receiving UCA receives the OAM multiplexed signal transmitted from the transmitting device and the MIMO multiplexed signal transmitted from the transmitting terminal. Receiving device. (Additional note 8) and an allocation mode determination unit that allocates OAM modes to a first line between the transmitting device and the receiving device and a second line between the transmitting terminal and the receiving device so that there is no overlap between the first line and the second line. 8. A receiving device according to claim 7.

[0089] 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]

[0090] 100 Transmitting device 110 Data Generation Unit 120 Modulation section 130 Mode multiplexing section 140 Mode allocation section 150 UCA 160 SINR calculation section 200 receiving device 210 UCA 220 Mode Separation Section 230 MIMO equalization section 240 Interference replica generation unit 250 Interference subtraction unit 260 Demodulation Unit 270 Allocation Mode Calculation Unit 280 Feedback Section 290 Preamble transmitter 300 Sending Terminal 310 Data Generation Unit 320 Modulation section 330 Precoding Unit 340 Antenna 350 SINR calculation section 400 Allocation mode determination device 500 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 including a transmitting device having a transmitting UCA and a receiving device having a receiving UCA, the receiving device is a wireless communication system that receives an OAM multiplexed signal transmitted from the transmitting device and a MIMO multiplexed signal transmitted from a transmitting terminal by the receiving UCA, The receiving device performing MIMO equalization reception on a signal on a second line between the transmitting terminal and the receiving device using only an OAM mode that is not used on a first line between the transmitting device and the receiving device; The OAM reception is performed for the signal on the first line using the OAM mode used on the first line. Wireless communication system.

2. an allocation mode determination unit that allocates an OAM mode to each of the first line and the second line so that there is no overlap between the first line and the second line; 10. The wireless communication system of claim 1.

3. The allocation mode determination unit Based on the reception SINR at the transmitting device and the reception SINR at the transmitting terminal, an OAM mode is assigned so as to maximize the reception SINR at the transmitting terminal while ensuring the communication capacity of the first line.

3. The wireless communication system according to claim 2.

4. The receiving device an interference replica generation unit that generates an interference replica from the second line to the first line using a channel estimate in the second line; an interference subtraction unit that subtracts the interference replica from the received signal of the first line; 4. The wireless communication system according to claim 2, comprising:

5. A communication method performed in a wireless communication system including a transmitting device having a transmitting UCA and a receiving device having a receiving UCA, a communication method in which the receiving device receives an OAM multiplexed signal transmitted from the transmitting device and a MIMO multiplexed signal transmitted from a transmitting terminal by the receiving UCA, The receiving device performing MIMO equalization reception on a signal on a second line between the transmitting terminal and the receiving device using only an OAM mode that is not used on a first line between the transmitting device and the receiving device; The OAM reception is performed for the signal on the first line using the OAM mode used on the first line. Communication method.

6. A receiving device usable in a wireless communication system including a transmitting device having a transmitting UCA and a receiving device having a receiving UCA, a receiving device that receives an OAM multiplexed signal transmitted from the transmitting device and a MIMO multiplexed signal transmitted from a transmitting terminal by the receiving UCA, performing MIMO equalization reception on a signal on a second line between the transmitting terminal and the receiving device using only an OAM mode that is not used on a first line between the transmitting device and the receiving device; The OAM reception is performed for the signal on the first line using the OAM mode used on the first line. Receiving device.

7. an allocation mode determination unit that allocates an OAM mode to each of the first line and the second line so that there is no overlap between the first line and the second line; 7. The receiving device according to claim 6.

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