Wireless communication system, wireless communication method, wireless communication device, and wireless communication program

Abstract

The present disclosure relates to a wireless communication system, a wireless communication method, a wireless communication device, and a wireless communication program. This wireless communication system is for performing wireless communication between a transmitting station equipped with a plurality of antennas and a receiving station equipped with a plurality of antennas and comprises a wireless communication unit configured so as to carry out: processing for acquiring first channel information that is channel information between transmission antennas and reception antennas; processing whereby a singular value matrix and a right singular matrix are acquired by performing singular decomposition of the first channel information; transmission signal quantity determination processing in which a transmission signal quantity is determined from the singular value matrix; and precoding matrix determination processing in which a precoding matrix is determined from the right singular matrix. The transmitting station is configured so as to carry out processing in which transmission signals are generated on the basis of the transmission signal quantity, processing in which the output destinations of the transmission signals are determined on the basis of the precoding matrix, and processing in which a radiated signal is transmitted by radiating the transmission signals to the output destinations. The receiving station is configured so as to carry out processing for receiving the radiated signal, processing in which second channel information is estimated on the basis of the precoding matrix and the first channel information, and processing in which the radiated signal is demodulated on the basis of the second channel information.

Description

[Technical Field]

[0001] The present disclosure relates to a wireless communication system, a wireless communication method, a wireless communication device, and a wireless communication program. [Background technology]

[0002] Low Earth Orbit (LEO) satellites, which orbit the Earth at an altitude of 2,000 km or less, are closer to the Earth's surface than Geostationary Earth Orbit (GEO), and are known to have various advantages when used in communication systems. For example, the distance between the satellite and the ground station is less than one-tenth of that of a conventional satellite, making it possible to significantly reduce propagation delay. Furthermore, the shorter propagation distance also reduces propagation loss, making it possible to reduce the power consumption of transmitters. This leads to the miniaturization of satellites and ground terminal stations, which is expected to reduce equipment costs.

[0003] Increasing the communication capacity of terrestrial terminals in a communication system using LEO satellites, or increasing the number of terminals accommodated, also requires a large capacity feeder link line for transmitting communication data to a base station. Non-Patent Document 1 discloses MIMO (Multiple-input Multiple-output) technology, which performs spatial multiplexing transmission using multiple antennas, as a method for increasing communication capacity. Utilizing this MIMO technology is desirable for increasing capacity. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] A. Knopp, RT Schwarz, D. Ogermann, CA Hofmann and B. Lankl, "Satellite System Design Examples for Maximum MIMO Spectral Efficiency in LOS Channels," IEEE GLOBECOM 2008 - 2008 IEEE Global Telecommunications Conference, 2008, pp. 1-6. [Non-patent document 2] Takanobu Watanabe and Kentaro Nishimori, "Evaluation of Channel Characteristics and Capacity of Asymmetric LoS-MIMO," IEICE Technical Report, vol. 121, no. 133, CQ2021-21, pp. 1-5, August 2021 [Non-patent document 3] Mitsuhiro Tategami, Daisuke Goto, Kiyohiko Itokawa, and Fumihiro Yamashita, "Variable Subarray Beamforming Method for Low-Earth-Orbit Satellite MIMO Transmission," IEICE General Conference, B-3-4, March 2022 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional MIMO wireless communication systems using LEO satellites, which are constantly moving and in line-of-sight environments, can sometimes experience high channel correlation between transmitters and receivers, resulting in issues such as reduced channel capacity and unstable communication lines.

[0006] To address the above-mentioned issues, Non-Patent Document 2 discloses a technique for performing eigenmode transmission by installing more antennas on one or both the transmitting and receiving sides than the number of signals to be transmitted. However, in eigenmode transmission, when precoding is performed on the transmitting side, multiple different signals are superimposed and radiated from the antenna. This poses the problem of generating signal peaks that have much higher power than the average power, i.e., an increase in the peak-to-average power ratio (PAPR). When such excessive signals are input to a transmission power amplifier, distortion occurs in the output signal, causing degradation of transmission quality. While it is possible to reduce distortion even for large peak signals by using devices with excellent input / output characteristics, this leads to increased power consumption.

[0007] Furthermore, Non-Patent Document 3 discloses a method of forming subarrays that maximize the channel capacity for a transmitted signal and performing in-phase combining for the desired receiving antenna with each subarray. This method forms subarrays for a single signal, thereby achieving beamforming gain from the array without increasing the PAPR. Furthermore, since it is possible to change the subarray configuration to one that reduces channel correlation based on channel information between the transmitter and receiver, it is possible to maximize the channel capacity in response to environmental changes.

[0008] However, in the above-mentioned method, in order to determine the subarray configuration and number of signals that maximize the channel capacity, the channel capacities of all subarrays and the number of signals are calculated, and then an exhaustive search is performed to find the one that maximizes the capacity. As a result, as the number of transmitting and receiving antennas increases, the number of factors for selecting the subarray configuration and the number of signals also increases, which poses a problem of an increased amount of calculation.

[0009] In order to solve the above-mentioned problems, a first object of the present disclosure is to provide a wireless communication system that can determine a subarray configuration that can obtain high channel capacity without increasing the amount of calculation in an environment in which a transmitting station and a receiving station perform MIMO transmission.

[0010] In order to solve the above-mentioned problems, a second object of the present disclosure is to provide a wireless communication method that can determine a subarray configuration that can obtain high channel capacity without increasing the amount of calculation in an environment where a transmitting station and a receiving station perform MIMO transmission.

[0011] In addition, in order to solve the above-mentioned problems, a third object of the present disclosure is to provide a wireless communication device that can determine a subarray configuration that can obtain high channel capacity without increasing the amount of calculation in an environment where a transmitting and receiving station performs MIMO transmission.

[0012] In addition, in order to solve the above-mentioned problems, a fourth object of the present disclosure is to provide a wireless communication program that can determine a subarray configuration that can obtain high channel capacity without increasing the amount of calculation in an environment where a transmitting and receiving station performs MIMO transmission. [Means for solving the problem]

[0013] A first aspect of the present disclosure is preferably a wireless communication system that performs wireless communication between a transmitting station equipped with a plurality of antennas and a receiving station equipped with a plurality of antennas, the wireless communication system including a wireless communication unit configured to perform: a process of acquiring first channel information that is channel information between the transmitting antennas and the receiving antennas; a process of acquiring a singular value matrix and a right singular matrix by singular decomposing the first channel information; a transmit signal number determination process of determining the number of transmit signals from the singular value matrix; and a precoding matrix determination process of determining a precoding matrix from the right singular matrix, wherein the transmitting station is configured to perform: a process of generating transmit signals based on the number of transmit signals; a process of determining output destinations of the transmit signals based on the precoding matrix; and a process of transmitting the transmit signals by emitting the transmit signals to the output destinations, and wherein the receiving station is configured to perform: a process of receiving the transmit signals; a process of estimating second channel information based on the precoding matrix and the first channel information; and a process of demodulating the transmit signals based on the second channel information.

[0014] A second aspect of the present disclosure is preferably a wireless communication method for performing wireless communication between a transmitting station equipped with a plurality of antennas and a receiving station equipped with a plurality of antennas, the wireless communication method including: acquiring first channel information that is channel information between the transmitting antennas and the receiving antennas; performing singular decomposition of the first channel information to acquire a singular value matrix and a right-hand singular matrix; determining the number of transmit signals from the singular value matrix; determining a precoding matrix from the right-hand singular matrix; generating transmit signals based on the number of transmit signals; determining output destinations of the transmit signals based on the precoding matrix; transmitting the transmit signals by radiating the transmit signals to the output destinations; receiving the radiated signals; estimating second channel information based on the precoding matrix and the first channel information; and demodulating the radiated signals based on the second channel information.

[0015] A third aspect of the present disclosure is preferably a wireless communication device included in a wireless communication system that performs wireless communication between a transmitting station having a plurality of antennas and a receiving station having a plurality of antennas, and is configured to perform the following processes: acquiring first channel information that is channel information between the transmitting antennas and the receiving antennas; acquiring a singular value matrix and a right singular matrix by singular decomposing the first channel information; determining the number of transmitted signals from the singular value matrix; and determining a precoding matrix from the right singular matrix.

[0016] A fourth aspect of the present disclosure is preferably a wireless communication program to be executed by a wireless communication device included in a wireless communication system that performs wireless communication between a transmitting station equipped with a plurality of antennas and a receiving station equipped with a plurality of antennas, the wireless communication program including a program for causing a computer to perform the following processes: a process of acquiring first channel information that is channel information between the transmitting antennas and the receiving antennas; a process of acquiring a right singular matrix and a singular value matrix by singular decomposing the first channel information; a process of determining the number of transmitted signals from the singular value matrix; and a process of determining a precoding matrix from the right singular matrix. [Effects of the Invention]

[0017] According to the first to fourth aspects of the present disclosure, in an environment where a transmitting / receiving station performs MIMO transmission, it is possible to determine a subarray configuration that can obtain a high channel capacity without increasing the amount of calculation. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a diagram illustrating a configuration example of a wireless communication system according to a first embodiment of the present disclosure. [Figure 2] 1 is a functional block diagram illustrating a wireless communication system according to a first embodiment of the present disclosure. [Figure 3] FIG. 2 is a diagram illustrating a hardware configuration of a transmitting station according to the first embodiment of the present disclosure. [Figure 4] 5 is a flowchart illustrating an example of operation of a transmitting station and a receiving station according to the first embodiment of the present disclosure. [Figure 5] FIG. 10 is a functional block diagram illustrating a wireless communication system according to a modified example of the first embodiment of the present disclosure. [Figure 6] FIG. 10 is a diagram illustrating a configuration example of a wireless communication system according to a second embodiment of the present disclosure. [Figure 7] FIG. 10 is a functional block diagram illustrating a wireless communication system according to a second embodiment of the present disclosure. [Figure 8] FIG. 11 is a functional block diagram illustrating a wireless communication system according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0019] Embodiment 1 FIG. 1 is a diagram illustrating a configuration example of a wireless communication system according to a first embodiment of the present disclosure. The wireless communication system 100 includes a transmitting station 2 and a receiving station 4. The transmitting station 2 has one or more transmitting antennas T x and the receiving station 4 has one or more receiving antennas R xFor example, the transmitting station 2 is a LEO satellite equipped with multiple antennas and moving within a service area, and the receiving station 4 is a satellite base station. Note that the transmitting station 2 is not limited to a LEO satellite and the receiving station 4 is not limited to a base station, and may be any transmitting / receiving station equipped with multiple antennas.

[0020] The transmitting station 2 and the receiving station 4 perform MIMO communication by radio. The receiving station 4 has a function for estimating channel information based on broadcast information from the transmitting station 2. The distance between the multiple antennas provided at each of the transmitting station 2 and the receiving station 4 is arranged so as to reduce channel correlation.

[0021] 2 is a functional block diagram showing a wireless communication system according to the first embodiment of the present disclosure. First, a normal downlink data path will be described. Data transmitted from a transmitting station 2 is first subjected to serial / parallel conversion of bit information in a serial / parallel converter 6, and input to a transmission signal generator 8. The number of parallel connections in this case is determined by the number of transmission signals obtained from a transmission signal determiner 30, which will be described later.

[0022] The transmission signal generation unit 8 modulates the input bit information, converts it into an electrical signal, and transmits it to the frequency conversion unit 10. The modulation method used here is determined for each signal by a modulation method obtained from the transmission signal determination unit 30, which will be described later.

[0023] The frequency conversion unit 10 converts the electrical signal into a radio signal of a predetermined frequency to be sent from an antenna, and transmits the signal to the transmitting antenna selection unit 12. The transmitting antenna selection unit 12 selects an antenna corresponding to each signal based on a precoding matrix input from a precoding matrix calculation unit 32 (described later), and transmits the signal with this information added to it to the phase control unit 14.

[0024] The phase control unit 14 controls the antenna directivity of each signal by controlling the phase so that each signal is combined in phase with a desired receiving antenna. The phase coefficient of each antenna is determined by referring to the elements of a precoding matrix obtained by a precoding matrix calculation unit 32 (described later).

[0025] As described above, the signal transmitted inside the transmitting station 2 is transmitted to the transmitting antenna T x from receiving antenna R x The transmitted signal is first sent to the frequency conversion unit 16 that the receiving station 4 has.

[0026] The frequency conversion unit 16 converts the radio signal into an electrical signal of a predetermined frequency and transmits it to the channel information estimation unit 18. The channel information estimation unit 18 estimates channel information from the received signal and transmits it to the received signal demodulation unit 20. Here, there are two types of channel information that can be estimated: before and after precoding.

[0027] The received signal demodulation unit 20 separates the interfering signals using the input pre-coded channel matrix, demodulates the electrical signals into bit information, and transmits the bit information to the parallel / serial conversion unit 22. The parallel / serial conversion unit 22 performs parallel / serial conversion on the bit information. This completes downlink data reception.

[0028] Next, a path for obtaining pre-precoding channel information H through feedback by transmitting a known pilot signal will be described. First, a pilot signal is transmitted from the transmitting station 2 to the receiving station 4 through the same path as the data transmission described above. The pilot signal is transmitted to the channel information estimation unit 18 via the frequency conversion unit 16. The channel information estimation unit 18 estimates pre-precoding channel information H and transmits the channel information H to the channel information transmission unit 24.

[0029] The channel information transmitter 24 transmits the channel information H to a channel information acquirer 26 included in the transmitting station 2. The channel information acquirer 26 transmits the acquired channel information H to a singular value decomposition unit 28. The singular value decomposition unit 28 performs singular value decomposition on the channel matrix held in the channel information H to calculate a singular value matrix, a right singular matrix, and a left singular matrix. The calculated matrices are then transmitted to the transmission signal determination unit 30.

[0030] The transmission signal determiner 30 determines a transmission signal based on the diagonal elements of the singular value matrix, i.e., the singular values. The transmission signal includes the number of transmission signals. The determined transmission signal is then transmitted to the precoding matrix calculator 32. The determined transmission signal is also transmitted to the transmission serial / parallel converter 6 and the transmission signal generator 8.

[0031] The transmission signal determination unit 30 may have an adaptive modulation function that adaptively determines the modulation method and error correction coding rate according to the value of the singular value.

[0032] The precoding matrix calculation unit 32 determines the output destination of each signal, i.e., the subarray configuration, based on the right singular matrix. The precoding matrix calculation unit 32 also determines the phase coefficient of each antenna based on the right singular matrix. The precoding matrix calculation unit 32 then transmits the determined information to the transmitting antenna selection unit 12 and the phase control unit 14. This feedback realizes optimization of wireless communication in this embodiment.

[0033] 3 is a diagram illustrating a hardware configuration of a transmitting station according to the first embodiment of the present disclosure. The transmitting station 2 includes a CPU 50. The CPU 50 is connected to a bus line 52. Memory devices such as a ROM 54, a RAM 56, and a storage 58 are connected to the bus line 52. A wireless communication program executed by the CPU 50 is stored in the memory device. The transmitting station 2 realizes a function specific to this embodiment by the CPU 50 executing the wireless communication program. Here, the function specific to this embodiment refers to a function of determining a precoding matrix and a transmission signal based on channel information.

[0034] A communication interface 60 is also connected to the bus line 52. The transmitting station 2 communicates with a network via the communication interface 60. An operation unit 62 and a display unit 64 are also connected to the bus line 52. The operation unit 62 and the display unit 64 function as a user interface for operating the transmitting station 2.

[0035] Although the case where the transmitting station 2 has the function specific to this embodiment has been described here, as will be described later, this function may also be provided in the control station 36. In that case, the transmitting station 2 in the description of FIG. 3 is replaced with the control station 36.

[0036] 4 is a flowchart showing an example of operation of the transmitting station and the receiving station according to the first embodiment of the present disclosure. A specific example of operation of the wireless communication system according to this embodiment will be described with reference to this flowchart.

[0037] First, in step 100, the transmitting station 2 transmits a known pilot signal to the receiving station 4. Next, in step 102, the receiving station 4 receives the pilot signal. Subsequently, in step 104, the receiving station 4 estimates channel information H based on the pilot signal. This estimation is performed by the channel information estimation unit 18. The estimated channel information H is information before precoding and is NR x ×NT x Then, in step 106, the receiving station 4 transmits the estimated channel information H to the transmitting station 2 as feedback.

[0038] Next, in step 108, the channel information acquisition unit 26 of the transmitting station 2 acquires the channel information H transmitted from the receiving station 4. Subsequently, in step 110, the singular value decomposition unit 28 of the transmitting station 2 performs singular value decomposition on the channel information H. Specifically, the singular value decomposition is expressed by the following equation.

[0039]

number

[0040] where U is NR x ×L left singular matrix, D is an L×L singular value matrix with singular values ​​on the diagonal, and V is NT x × L. In eigenmode transmission, by using this right singular matrix V as the transmission weight matrix and the left singular matrix U as the reception weight matrix, it is possible to obtain an ideally high channel capacity.

[0041] Next, in step 112, the transmission signal determination unit 30 of the transmitting station 2 determines the number of transmission signals N based on the singular values ​​of the singular value matrix D. s This determination is made after determining the correlation of the channel. s The following relational expression holds: where L is the spatial multiplexing number, which represents the maximum number of signals that can be transmitted.

[0042]

number

[0043] For example, if the channel matrix is ​​uncorrelated, L singular values ​​are obtained, so the number of transmitted signals is N s Let L be the number of transmitted signals. In addition, if the channel is perfectly correlated, only one singular value is obtained. s Let be 1.

[0044] Subsequently, in steps 114 to 122, the precoding matrix calculation unit 32 of the transmitting station 2 calculates the precoding matrix P. The precoding matrix P is calculated by the following formula: x ×L matrix, and has the subarray configuration and phase information of the present disclosure. Furthermore, the generation of the precoding matrix P is based on the transmission weights for eigenmode transmission.

[0045] When a precoding matrix P is calculated from channel information H and a signal is transmitted, the received signal is expressed by the following equation: where s is a transmission signal vector.

[0046]

number

[0047] Furthermore, the radiation signal x from the antenna is expressed by the following equation using the precoding matrix P and the transmission signal s.

[0048]

number

[0049] A specific method for calculating the precoding matrix P will be described. First, in step 114, NT x From the right singular matrix V of ×L, the number of transmitted signals N s corresponding to NT x ×N s Submatrix V of sub The elements of the right singular matrix V are complex numbers.

[0050] Next, in steps 116 to 122, the precoding matrix P is calculated. Specifically, the matrix V sub The amplitude components are compared for each row of the matrix P. Then, only the phase component of the element with the largest amplitude is extracted, and the other elements are set to 0 to obtain the precoding matrix P.

[0051] A more specific calculation procedure will be described. In step 116, 1 is substituted into the loop variable k, and a precoding matrix P is set with all elements set to 0. Next, in step 118, the matrix V sub Next, in step 120, the phase coefficient at which the amplitude component is maximized is stored in the precoding matrix P.

[0052] Next, in step 122, the matrix V sub It is checked whether steps 118 and 120 have been performed for all rows of . If they have been performed, the process proceeds to step 124. If they have not been performed, k+1 is substituted for k, and the process returns to step 118.

[0053] In addition, for the above calculation, the matrix V sub This may be implemented by applying the algorithm shown in the table below to the

[0054] [Table 1]

[0055] Next, in step 124, the transmitting station 2 generates a transmission signal s. Specifically, the serial / parallel converter 6 converts the number of transmission signals N output from the transmission signal determining unit 30 into s Then, the parallel-converted data bit string is transmitted to the transmission signal generation unit 8. The transmission signal generation unit 8 generates a transmission signal s based on the transmitted data bit string.

[0056] As described above, the radiated signal x is expressed as the inner product of the row vector of the precoding matrix P and the vector of the transmitted signal s. Therefore, the operations of steps 116 to 122 are equivalent to selecting the single element signal with the highest power from the signals radiated from each antenna during eigenmode transmission.

[0057] Also, each column vector NT of the precoding matrix P x ×1 corresponds to each signal and has information on the subarray configuration, meaning that a phase-controlled signal is emitted from the antenna corresponding to the row number of the non-zero element.

[0058] Next, in step 126, the output destination of each signal is determined, and the radiated signal x from the phase coefficient controlled antenna is transmitted. As described above, the radiated signal x from each antenna can be expressed as the inner product of the precoding matrix P and the transmission signal s. That is, transmission is performed by radiating a signal from each antenna based on the generated transmission signal s and the obtained precoding matrix P. Note that the components of the radiated signal x are complex numbers.

[0059] Specifically, first, the non-zero elements of the precoding matrix P are referenced, and the signal output destination is changed in the transmitting antenna selector 12. Then, a subarray is configured based on the information on the changed output destination. The transmission signal s is radiated by phase control based on this subarray, thereby transmitting the radiation signal x.

[0060] Next, in step 128, the receiving station 4 receives the signal. Next, in step 130, the channel information estimation unit 18 of the receiving station 4 estimates the channel information HP after precoding.

[0061] Next, in step 132, the received signal demodulation unit 20 of the receiving station 4 demodulates the signal using the channel information HP. Specifically, it calculates a receiving weight from the mixed signals using an algorithm such as ZF or MMSE. Then, it separates the signals and converts each signal into a bit string.

[0062] 5 is a functional block diagram showing a wireless communication system according to a modification of the first embodiment of the present disclosure. In the first embodiment, when the transmitting station acquires channel information, a method is used in which a pilot signal transmitted from the transmitting station 2 is fed back. However, as in this modification, the transmitting station 2 may have a channel information estimation unit 34 and estimate the channel information based on a signal from the receiving station 4. Note that, as in the first embodiment, a method of estimating channel information by transmitting a pilot signal is shown here, but the channel information may also be estimated using an uplink data signal.

[0063] Embodiment 2 6 is a diagram illustrating a configuration example of a wireless communication system according to Embodiment 2 of the present disclosure. The wireless communication system 200 of this embodiment differs from Embodiment 1 in that it includes a control station 36 in addition to a transmitting station 2 and a receiving station 4.

[0064] In the wireless communication system 100, the transmitting station acquires channel information and determines the number of transmission signals, modulation scheme, coding rate, and precoding matrix. On the other hand, in the wireless communication system 200, the control station 36 has a function of determining the above information and a control information transmitter that notifies the transmitting station of this information as control information. The transmitting station 2 controls itself using the control information acquired by the control station 36.

[0065] 7 is a functional block diagram showing a wireless communication system according to Embodiment 2 of the present disclosure. Since the path of normal downlink data is the same as in Embodiment 1, a path for processing a known pilot signal will be described here.

[0066] First, as in the first embodiment, a pilot signal is transmitted from the transmitting station 2 to the receiving station 4. The channel information estimation unit 18 receives the pilot signal, estimates channel information H before precoding, and transmits the channel information H to the singular value decomposition unit 38 included in the control station 36.

[0067] The singular value decomposition unit 38 calculates a singular value matrix, a right singular matrix, and a left singular matrix by processing similar to that of the singular value decomposition unit 28 described above, and transmits the calculated results to the transmit signal determination unit 40. The transmit signal determination unit 40 determines the number of transmit signals, the modulation scheme, and the coding rate by processing similar to that of the transmit signal determination unit 30 described above, and transmits the information to the precoding matrix calculation unit 42. The precoding matrix calculation unit 42 determines the precoding matrix P by processing similar to that of the precoding matrix calculation unit 32 described above, and transmits the information to the control information transmission unit 44. The control information transmission unit 44 compiles the number of transmit signals, the modulation scheme, and the coding rate obtained by the transmit signal determination unit 40, as well as the precoding matrix, as control information, and transmits the control information to the channel information acquisition unit 26 of the transmitting station 2.

[0068] The channel information acquisition unit 26 receives the control information and transmits it to the serial / parallel conversion unit 6, the transmission signal generation unit 8, the transmission antenna selection unit 12, and the phase control unit 14. This feedback realizes optimization of wireless communication in this embodiment.

[0069] 8 is a functional block diagram showing a wireless communication system according to a third embodiment of the present disclosure. The wireless communication system of this embodiment is similar to the second embodiment in that it includes a control station 36 in addition to a transmitting station 2 and a receiving station 4, but differs in that it uses a geometric channel information estimation unit 46 included in the control station 36 for channel information estimation.

[0070] The geometric channel information estimator 46 estimates the geometric channel information of the transmitting antenna T x and receiving antenna R x The channel information is estimated by computer using a radio wave propagation model based on the spatial conditions of propagation, such as the relative positions of the users and the weather. Radio wave propagation models that can be used include estimation formulas, ray tracing, and machine learning.

[0071] Embodiment 3 A description will be given of a wireless communication route according to embodiment 3. Since the route for normal downlink data is the same as that of embodiment 1, a route for performing channel estimation using information from the geometric channel information estimation unit 46 will be described here.

[0072] First, the geometric channel information estimation unit 46 acquires the propagation space conditions, such as the positions of the transmitting and receiving antennas and the weather, which are necessary for channel information estimation. For example, in the case of satellite feeder link MIMO, where the transmitting station is a LEO satellite and the receiving station is a ground station, orbit information, satellite antenna configuration information, and the positional relationship between the transmitting and receiving antennas can be acquired from the antenna layout of the ground station. In addition, the propagation space conditions, such as the weather, can be acquired from the nowcast information published by the Japan Meteorological Agency. Then, using a radio wave propagation model, the channel information is estimated by a computer.

[0073] The estimated channel information H is transmitted to the singular value decomposition unit 38. After this, the channel information is fed back by the same process as in embodiment 2. This feedback realizes optimization of wireless communication in this embodiment.

[0074] In the wireless communication systems according to the first to third embodiments of the present disclosure, control is performed based on analog beamforming using a transmitting antenna selector and a phase controller. However, control may be performed based on digital beamforming, in which amplitude and phase are controlled by a digital signal processing circuit.

[0075] In the wireless communication systems according to the first to third embodiments of the present disclosure, subarrays are configured by referring to the non-zero elements of the precoding matrix P and changing the output destination of signals in a transmitting antenna selection unit. However, in the above-described control method, all amplitude components except for one element in each row of the precoding matrix P are forcibly set to zero. This prevents signal combining, making it possible to form pseudo subarrays.

[0076] The above control method also enables amplitude control, so instead of extracting only the phase component as in the algorithm shown in Table 1, control can be performed by simultaneously extracting the amplitude component, or amplitude control based on the binomial distribution or Dolph-Chebyshev distribution can be performed in each subarray. [Explanation of symbols]

[0077] 2 transmitting stations 4 receiving stations 36 Control Station 100 Wireless Communication System 200 Wireless Communication System

Claims

1. A wireless communication system for performing wireless communication between a transmitting station having a plurality of antennas and a receiving station having a plurality of antennas, A process of obtaining first channel information, which is channel information between a transmitting antenna and a receiving antenna; obtaining a singular value matrix and a right singular matrix by singular decomposing the first channel information; a transmission signal number determination process for determining the number of transmission signals from the singular value matrix; a precoding matrix determination process for determining a precoding matrix from the right singular matrix; a wireless communication unit configured to perform the The transmitting station generating a transmission signal based on the number of transmission signals; A process of determining an output destination of the transmission signal based on the precoding matrix; transmitting a radiation signal by radiating the transmission signal to the output destination; is configured to perform The receiving station receiving the emitted signal; estimating second channel information based on the precoding matrix and the first channel information; demodulating the emitted signal based on the second channel information; is configured to implement Wireless communication system.

2. The process of determining the number of transmitted signals includes: The method includes a process of determining the number of transmitted signals from the singular values ​​included in the singular value matrix.

10. The wireless communication system of claim 1.

3. The precoding matrix determination process includes: extracting a column submatrix from the right singular matrix; comparing elements of amplitude components for each row of the column submatrix; A process of setting all components except for the component with the largest amplitude component to zero for each row of the column submatrix.

2. The wireless communication system of claim 1, comprising:

4. The wireless communication unit is included in the transmitting station.

10. The wireless communication system of claim 1.

5. A wireless communication system further comprising a control station, The control station the wireless communication unit, transmitting the number of transmission signals and the precoding matrix to the transmitting station; transmitting the precoding matrix to the receiving station; 10. The wireless communication system of claim 1, configured to implement:

6. A wireless communication method for performing wireless communication between a transmitting station having a plurality of antennas and a receiving station having a plurality of antennas, comprising: Obtaining first channel information, which is channel information between a transmitting antenna and a receiving antenna; singular decomposing the first channel information to obtain a singular value matrix and a right singular matrix; determining a number of transmitted signals from the singular value matrix; determining a precoding matrix from the right singular matrix; generating a transmission signal based on the number of transmission signals; determining an output destination of the transmission signal based on the precoding matrix; transmitting a radiation signal by radiating the transmission signal to the output destination; receiving the emitted signal; estimating second channel information based on the precoding matrix and the first channel information; demodulating the radiation signal based on the second channel information; A wireless communication method comprising:

7. A wireless communication device provided in a wireless communication system that performs wireless communication between a transmitting station having a plurality of antennas and a receiving station having a plurality of antennas, A process of obtaining first channel information, which is channel information between a transmitting antenna and a receiving antenna; obtaining a singular value matrix and a right singular matrix by singular decomposing the first channel information; determining the number of transmitted signals from the singular value matrix; determining a precoding matrix from the right singular matrix; 10. A wireless communication device configured to implement the

8. A wireless communication program to be executed by a wireless communication device included in a wireless communication system that performs wireless communication between a transmitting station having a plurality of antennas and a receiving station having a plurality of antennas, A process of obtaining first channel information, which is channel information between a transmitting antenna and a receiving antenna; obtaining a right singular matrix and a singular value matrix by singular decomposing the first channel information; determining the number of transmitted signals from the singular value matrix; determining a precoding matrix from the right singular matrix; A wireless communication program including a program for causing a computer to execute the above.

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