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

Abstract

The present disclosure pertains to a wireless communication system, a wireless communication method, a wireless communication device, and a wireless communication program. In the wireless communication system, a transmission station and a reception station perform wireless communication. The transmission station is configured to execute: a process for acquiring placement area information, which is information about an area in which reception stations are placed; a process for performing, on the plurality of reception stations belonging to the area and on the basis of the placement area information, simple channel estimation by using plane-wave approximation; a process for calculating the beamforming weights on the basis of the result of the simple channel estimation; and a process for performing signal transmission on the basis of the weights.

Description

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

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

[0002] In recent years, in wireless communication using a non-terrestrial network (NTN), many use cases of wireless communication are assumed. For example, Non-Patent Document 1 discloses use cases such as direct accommodation of terrestrial mobile terminals, mobile backhaul, or accommodation of IoT terminals.

[0003] As a result, wireless communication using NTN tends to have an increased transmission capacity compared to existing satellite communication services. Therefore, in wireless communication using NTN, an increase in the capacity of the feeder link is required.

[0004] To increase the capacity of the feeder link, an ultra-wideband massive MIMO (multiple-input and multiple-output) system has been proposed. For example, Non-Patent Document 2 discloses a technique for forming an ultra-wideband massive MIMO system by arranging a plurality of antennas on an aerial platform and a large number of small antennas at a ground gateway station.

[0005] In the above-described technique, when the aerial platform is a mobile station such as a low-earth orbit satellite, beamforming on the mobile station side is required. In particular, when performing beamforming for the purpose of high-capacity communication, CSI (Channel State Information) between transmission and reception is required.

[0006] 3GPP TR 38.821, Solutions for NR to Support Non-Terrestrial Networks (NTN) (Release 16), V16.1.0, May. 2021. Tatsukami et al., "Proposal of Hierarchical Base Station Configuration in Ultra-Wideband Massive MIMO System", IEICE Transactions on Communications, B-3-5, Mar. 2023.

[0007] However, the aforementioned technology had a problem in that, in environments where mobile stations were moving at high speeds, it was difficult for a ground gateway station to estimate the CSI between numerous transmitting and receiving antennas and to provide accurate CSI feedback.

[0008] The primary objective of this disclosure is to provide a wireless communication system that can achieve high capacity feeder links without requiring accurate CSI feedback to the transmitting station, in order to solve the aforementioned problems.

[0009] Furthermore, a second objective of this disclosure is to provide a wireless communication method that can achieve high capacity feeder links without requiring accurate CSI feedback to the transmitting station.

[0010] Furthermore, a third objective of this disclosure is to provide a wireless communication device that can achieve high capacity feeder links without requiring accurate CSI feedback to the transmitting station.

[0011] Furthermore, a fourth objective of this disclosure is to provide a wireless communication program that can achieve high capacity feeder links without requiring accurate CSI feedback to the transmitting station.

[0012] A first aspect of this disclosure is a wireless communication system in which a transmitting station and a receiving station perform wireless communication, wherein the transmitting station is preferably configured to perform the following: a process of acquiring location area information, which is information about the area in which the receiving station is located; a process of performing a simplified channel estimation by plane wave approximation for a plurality of receiving stations belonging to the area based on the location area information; a process of calculating beamforming weights based on the results of the simplified channel estimation; and a process of transmitting a signal based on the weights.

[0013] Furthermore, a second aspect of this disclosure is preferably a wireless communication method implemented by a wireless communication system in which a transmitting station and a receiving station communicate wirelessly, comprising: acquiring location area information which is information about the area in which the receiving station is located; performing a simplified channel estimation by plane wave approximation for a plurality of receiving stations belonging to the area based on the location area information; calculating beamforming weights based on the results of the simplified channel estimation; and transmitting a signal based on the weights.

[0014] Furthermore, a third aspect of this disclosure is preferably a wireless communication device that performs wireless communication with a receiving station, and is configured to perform the following: a process of acquiring location area information, which is information about the area where the receiving station is located; a process of performing a simplified channel estimation by plane wave approximation for a plurality of receiving stations belonging to the area based on the location area information; a process of calculating beamforming weights based on the results of the simplified channel estimation; and a process of transmitting a signal based on the weights.

[0015] Furthermore, a fourth aspect of this disclosure is preferably a wireless communication program to be implemented by a wireless communication device having a processor and memory and performing wireless communication with a receiving station, the program being stored in memory and computer-readable, and which includes a program to cause the processor to perform the following: a process of acquiring location area information, which is information of the area where the receiving station is located; a process of performing a simplified channel estimation by plane wave approximation for a plurality of receiving stations belonging to the area based on the location area information; a process of calculating beamforming weights based on the results of the simplified channel estimation; and a process of transmitting a signal based on the weights.

[0016] According to the first to fourth aspects of this disclosure, it is possible to increase the capacity of the feeder link without requiring accurate CSI feedback to the transmitting station.

[0017] This figure shows an overview of the wireless communication system according to Embodiment 1 of the present disclosure. This figure shows an example configuration of the wireless communication system according to Embodiment 1 of the present disclosure. This figure shows an example configuration of the transmitting station according to Embodiment 1 of the present disclosure. This figure shows an example configuration of the receiving station according to Embodiment 1 of the present disclosure. This figure shows the hardware configuration of the receiving station according to Embodiment 1 of the present disclosure. This flowchart shows the processing performed by the wireless communication system according to Embodiment 1 of the present disclosure. This figure shows the acquisition of placement area information according to Embodiment 1 of the present disclosure. This figure shows the method for acquiring placement area information according to Embodiment 1 of the present disclosure. This figure shows a simplified channel estimation according to Embodiment 1 of the present disclosure. This figure shows the environment of a simulation example according to Embodiment 1 of the present disclosure. This is a graph showing the results of the first simulation according to Embodiment 1 of the present disclosure. This is a graph showing the results of the second simulation according to Embodiment 1 of the present disclosure.

[0018] Each embodiment will be described with reference to the drawings. The same or corresponding components will be denoted by the same reference numerals, and repetition of the description may be omitted.

[0019] Embodiment 1 Figure 1 is a diagram showing an overview of a wireless communication system according to Embodiment 1 of the present disclosure. The wireless communication system according to Embodiment 1 of the present disclosure includes a transmitting station 2. The transmitting station 2 is a mobile station such as a low Earth orbit satellite.

[0020] Transmitting station 2 communicates wirelessly with receiving station 4. Receiving station 4 is a ground base station equipped with a small antenna.

[0021] Figure 2 shows an example configuration of a wireless communication system according to Embodiment 1 of the present disclosure. The wireless communication system 100 includes a transmitting station 2. The transmitting station 2 has transmitting antennas 21a to 21m. That is, the transmitting station 2 has m transmitting antennas, where m is any natural number.

[0022] Transmitting station 2 communicates wirelessly with receiving station 4 via transmitting antennas 21a to 21m. Receiving station 4 communicates wirelessly with transmitting station 2 via receiving antennas 41a to 41n. In other words, receiving station 4 has n receiving antennas, where n is any natural number. Hereafter, receiving antennas 41a to 41n will be referred to as the antenna section 41.

[0023] Figure 3 shows an example configuration of a transmitting station according to Embodiment 1 of the present disclosure. The transmitting station 2 has an area acquisition unit 22. The area acquisition unit 22 acquires location area information, which is information about the area where the receiving station 4 is located.

[0024] The area acquisition unit 22 transmits the acquired location area information to the simplified channel estimation unit 23. The simplified channel estimation unit 23 performs a simplified channel estimation based on the received location area information. Specifically, the simplified channel estimation unit 23 performs a simplified channel estimation using plane wave approximation for multiple receiving stations 4 belonging to the area. More specifically, the simplified channel estimation unit 23 performs a simplified channel estimation by assuming that the arriving wave is transmitted from the area where the multiple receiving stations 4 are located and performing a plane wave approximation. A more specific method of simplified channel estimation will be described later.

[0025] The simplified channel estimation unit 23 transmits the results of the simplified channel estimation to the weight calculation unit 24. The weight calculation unit 24 calculates the beamforming weights based on the received results of the simplified channel estimation. These weights are calculated to maximize the orthogonality of the beamforming. The weight calculation unit 24 transmits the calculated weights to the signal transmission unit 28.

[0026] The transmitting station 2 also has a transmitting signal generation unit 26. The transmitting signal generation unit 26 generates signals for wireless communication. The transmitting signal generation unit 26 generates signals for wireless communication by, for example, performing S / P conversion, error correction, or modulation.

[0027] The transmission signal generation unit 26 transmits the generated signal to the signal transmission unit 28. The signal transmission unit 28 sets the parameters for beamforming the signal received from the transmission signal generation unit 26 based on the weights received from the weight calculation unit 24.

[0028] Furthermore, the signal transmission unit 28 transmits the received signal to the appropriate transmitting antennas 21a to 21m based on the settings. The transmitting antennas 21a to 21m then transmit the received signal to the receiving antennas 41a to 41n, thereby performing signal transmission using beamforming as set by the signal transmission unit 28.

[0029] Figure 4 shows an example of the configuration of a receiving station according to Embodiment 1 of the present disclosure. The receiving station 4 has receiving antennas 41a to 41n. The receiving antennas 41a to 41n receive a signal from the transmitting station 2. This signal is a spatially multiplexed signal.

[0030] The receiving antenna 41a transmits the received signal to the signal transmitting / receiving unit 46a. The signal transmitting / receiving unit 46a transmits the received signal to the receiving unit 47a. This transmission may be performed, for example, by wireless communication or by optical fiber communication. Optical fiber communication is, for example, RoF (Radio over Fiber).

[0031] Similarly, the receiving antenna 41b transmits the received signal to the signal transmitting / receiving unit 46b. Similarly, the signal transmitting / receiving unit 46b transmits the received signal to the receiving unit 47b. The same applies to the receiving antennas 41c to 41n and the signal transmitting / receiving units 46c to 46n.

[0032] The receiving units 47a to 47n transmit the received signals to the MIMO demodulation unit 49. The MIMO demodulation unit 49 performs channel estimation, MIMO equalization, and synthesis to separate the spatially multiplexed signals. If the transmission of signals from the signal transmitting / receiving units 46a to 46n to the receiving units 47a to 47n is performed using optical fiber communication, this transmission involves conversion from optical signals to electrical signals.

[0033] Figure 5 shows the hardware configuration of a receiving station according to Embodiment 1 of this disclosure. Each function of the receiving station 4 may be partially or entirely configured by hardware such as a PLD (Programmable Logic Device) or FPGA (Field Programmable Gate Array), or it may be configured as a program executed by a processor such as a CPU.

[0034] For example, the receiving station 4 can be implemented using a computer and a program, and the program can be recorded on a storage medium or provided via a network.

[0035] As shown in FIG. 5, the receiving station 4 includes an input unit 400, an output unit 401, a communication unit 402, a CPU 403, a memory 404, and an HDD 405 connected via a bus 406, and has functions as a computer. Further, the receiving station 4 is capable of inputting and outputting data to and from a computer-readable storage medium 407.

[0036] The input unit 400 is, for example, a keyboard and a mouse. The output unit 401 is, for example, a display device such as a display.

[0037] The communication unit 402 is, for example, a communication interface that communicates with a wireless device to be controlled.

[0038] The CPU 403 controls each unit constituting the receiving station 4 and performs predetermined processing and the like. The memory 404 and the HDD 405 store data and the like.

[0039] The storage medium 407 is capable of storing a program and the like for causing the receiving station 4 to execute its functions. Note that the architecture constituting the receiving station 4 is not limited to the example shown in FIG. 5.

[0040] FIG. 6 is a flowchart showing the processing performed by the wireless communication system according to Embodiment 1 of the present disclosure. Here, the processing performed by the transmitting station 2 and the receiving station 4 is shown in a flowchart.

[0041] First, in step 100, the transmitting station 2 acquires location area information. Specifically, the area acquisition unit 22 acquires location area information, which is information on the area where the receiving station 4 is located.

[0042] Next, in step 102, the transmitting station 2 performs simple channel estimation. Specifically, the simple channel estimation unit 23 estimates a simple channel H ｓｉｍｐｌｅ based on the received location area information.

[0043] Next, in step 104, the transmitting station 2 calculates the weight for beamforming. Specifically, the weight calculation unit 24 calculates a beamforming weight P based on the result of the received simple channel estimation.

[0044] Next, in step 106, the transmitting station 2 generates and transmits a signal. Specifically, first, the transmission signal generation unit 26 generates a signal for performing wireless communication. Also, the signal transmission unit 28 makes settings for beamforming the received signal based on the received weight. Further, the transmission antennas 21a to 21m transmit the received signal to the reception antennas 41a to 41n, so that the signal transmission unit 28 performs signal transmission by beamforming as set.

[0045] If the signal generated by the transmission signal generation unit 26 in this step is defined as the transmission signal s, the transmission signal by beamforming is represented as Ps.

[0046] Next, in step 108, the receiving station 4 receives a signal. Specifically, the reception antennas 41a to 41n receive a signal from the transmitting station 2. The received signal received in this step is represented by Equation 1 using the actual channel H.

[0047]

[0048] Next, in step 110, the receiving station 4 performs channel estimation. Specifically, the MIMO demodulation unit 49 estimates the channel HP including the weight P of beamforming.

[0049] Next, in step 112, the receiving station 4 calculates the weight W for signal separation. Specifically, the MIMO demodulation unit 49 calculates the weight W for signal separation based on the channel HP.

[0050] Next, in step 114, the receiving station 4 performs signal separation and ends the process. Specifically, the MIMO demodulation unit 49 performs signal separation by multiplying the weight W by the received signal r. The demodulated signal calculated at this time is represented by Equation 2.

[0051]

[0052] The simplified channel estimation method will be explained in detail. Figure 7 shows the acquisition of deployment area information according to Embodiment 1 of this disclosure. This disclosure achieves increased feeder link capacity without requiring accurate CSI feedback to the transmitting station 2, which is a mobile station such as a low Earth orbit satellite. Therefore, the transmitting station 2 performs simplified channel estimation based on the deployment area information.

[0053] First, transmitting station 2 acquires location area information. This location area information is for area 60, the area where receiving station 4 is located. The information for area 60 is expressed, for example, as the area angle (azimuth angle θ, zenith angle φ) relative to transmitting station 2. By extracting the area angle from the acquired location area information, transmitting station 2 can determine the approximate direction of receiving station 4, the destination of the transmission.

[0054] Furthermore, if the placement area information includes the area angle, the placement area information does not need to include detailed location information for each receiving station 4 located in area 60. Detailed location information refers to, for example, the latitude or longitude of each receiving station 4.

[0055] Figure 8 is a diagram showing a method for acquiring placement area information according to Embodiment 1 of this disclosure. The placement area information may be stored in advance in the memory of the transmitting station 2, or it may be acquired by an external sensor such as a camera. Alternatively, the placement area information may be acquired by receiving a notification from the control station 8.

[0056] Figure 9 shows a simplified channel estimation according to Embodiment 1 of the present disclosure. Transmitting station 2 performs simplified channel estimation based on acquired placement area information. Transmitting station 2 performs simplified channel estimation by assuming that the incoming wave is transmitted from the receiving station 4 where it is located and performing a plane wave approximation. At this time, the angle of the incoming wave may be set randomly, or it may be assumed that it arrives uniformly.

[0057] More specifically, transmitting station 2 performs simplified channel estimation using array response vector a. Array response vector a is calculated using the angle of the arriving wave as input. If the number of ground antennas is Nr, the simplified channel H is a matrix formed by concatenating array response vectors equal to the number of ground antennas.ｓｉｍｐｌｅ This is expressed by equation 3.

[0058]

[0059] The array response vector a is expressed by equation 4, and the array response vector components are expressed by equation 5.

[0060]

[0061]

[0062] Here, r ｋ This is the position vector of the kth transmitting antenna among the transmitting antennas 21a to 21m mounted on transmitting station 2. The unit vector of the viewing direction L is expressed by equation 6.

[0063]

[0064] Next, transmitting station 2 calculates the beamforming weight P. Specifically, transmitting station 2 calculates the beamforming weight H ｓｉｍｐｌｅ Based on this, we calculate the weight P that enables highly orthogonal beamforming. This is because selecting a weight P that enables highly orthogonal beamforming improves transmission capacity.

[0065] The realization of a highly orthogonal beam can be achieved, for example, by eigenmode transmission. Eigenmode transmission is a known method for obtaining high transmission capacity in MIMO transmission. Eigenmode transmission is a method that utilizes the singular value decomposition of the channel. Specifically, eigenmode transmission is a method in which transmitting station 2 utilizes the right singular matrix (unitary matrix) obtained by the singular value decomposition of the channel.

[0066] Simple Channel H ｓｉｍｐｌｅ The singular value decomposition of is expressed by equation 7.

[0067]

[0068] In this case, the beamforming weight P is expressed by equation 8.

[0069]

[0070] In this disclosure, the transmitting station 2 does not acquire an actual channel. Therefore, in this disclosure, the transmitting station 2 uses a simplified channel H instead of an actual channel. ｓｉｍｐｌｅ By performing singular value decomposition, we obtain a unitary matrix.

[0071] Alternatively, a highly orthogonal beam can be achieved, for example, by transmitting beamformation based on DFT (Discrete Fourier Transform), or by selecting channels that have high channel capacitance. The selection of L beams that have high channel capacitance can be achieved, for example, by exhaustively searching for the combination that maximizes capacitance from a simplified channel matrix of Nr × Nt. In this case, L is the spatial multiplexing number and is expressed by equation 9.

[0072]

[0073] On the other hand, using a brute-force search method leads to increased computational complexity. Therefore, the selection of L beams that maximize channel capacity can be achieved by selecting the channels to use from a simplified Nr × Nt channel matrix using a greedy algorithm or similar method. This method reduces computational complexity while simultaneously maximizing channel capacity.

[0074] The issues that this disclosure addresses will be explained in detail. In recent years, many wireless communication use cases are envisioned for wireless communication using NTN. For example, Non-Patent Document 1 discloses use cases such as direct connection of terrestrial mobile terminals, mobile backhaul, and connection of IoT terminals.

[0075] As a result, wireless communication using NTN tends to have increased transmission capacity compared to existing satellite communication services. Therefore, increasing the capacity of the feeder link is required for wireless communication using NTN.

[0076] The feeder link is a circuit that connects the aerial platform to the ground gateway station. The aerial platform is, for example, a satellite or a High Altitude Platform Station (HAPS).

[0077] As a method for increasing the capacity of the feeder link, for example, Non-Patent Document 2 discloses a technology that uses an ultra-wide-area Massive MIMO system. In this technology, an ultra-wide-area Massive MIMO system is formed by arranging multiple antennas on an aerial platform and numerous small antennas on a ground gateway station. In other words, the number of spatial multiplexing operations is increased by arranging numerous antennas on both the transmitting and receiving sides. As a result, an increase in the capacity of the feeder link can be expected.

[0078] In the above-mentioned technology, if the upper-air platform is a mobile station such as a low-Earth orbit satellite, beamforming is required on the mobile station side. In particular, when beamforming is performed for the purpose of high-capacity communication, Channel State Information (CSI) between the transmitter and receiver is required.

[0079] However, the aforementioned technology had a problem in that, in environments where mobile stations move at high speeds, it was difficult for mobile stations to estimate the CSI between a large number of total receiving antennas and to provide accurate CSI feedback.

[0080] The wireless communication system according to Embodiment 1 of this disclosure performs simplified channel estimation based on location area information. As a result, it is possible to increase the capacity of the feeder link without requiring accurate CSI feedback to the transmitting station.

[0081] A simulation example according to Embodiment 1 of this disclosure is shown. Figure 10 is a diagram showing the environment of the simulation example according to Embodiment 1 of this disclosure. Here, a simulation example is shown for the median value of the channel capacity when the transmitting station 2 is moved on a two-dimensional coordinate plane.

[0082] In this simulation, transmitting station 2 is assumed to move in the x-axis direction. The transmitting antenna of transmitting station 2 has 16 elements, and the element spacing is set to two patterns: 0.5λ and 2.5λ.

[0083] Furthermore, in this simulation, the receiving antennas of receiving station 4 are assumed to be randomly placed in the range from -500 km to 500 km. In addition, the total gain of the receiving antennas of receiving station 4 is kept constant, while the total number of antennas is varied.

[0084] The other settings used in this simulation are as shown in Table 1.

[0085]

[0086] Furthermore, this simulation compares the channel capacity obtained by the simplified channel estimation method according to Embodiment 1 of this disclosure with the channel capacity obtained by the conventional channel estimation method. In this case, the channel capacity obtained by the conventional channel estimation method is an ideal value. In addition, this simulation compares the case where a unitary matrix is ​​selected as the beamforming standard with the case where maximum ratio synthesis is selected.

[0087] Furthermore, when using maximum ratio synthesis as the standard, beamforming weights are selected by selecting those that maximize capacitance using a greedy method. In addition, MMSE is used for interference compensation on the receiving station 4 side.

[0088] Figure 11 is a graph showing the results of a first simulation according to Embodiment 1 of the present disclosure. Here, the results of the simulation of the median channel capacitance when the element spacing of the transmitting antenna of the transmitting station 2 is 0.5λ are shown.

[0089] In Figure 11 and Figure 12 (described later), "Proposal 1" shows the results of simplified channel estimation and unitary matrix-referenced beamforming (BF), while "Proposal 2" shows the results of simplified channel estimation and maximalized composite-referenced BF. Also in Figure 11 and Figure 12 (described later), "Ideal Value" shows the results of conventional channel estimation and unitary matrix-referenced BF, while "Comparative Example" shows the results of conventional channel estimation and maximalized ratio-referenced BF.

[0090] As shown in the graph, as the number of ground antennas increases, the channel capacity obtained by simplified channel estimation asymptotically approaches the ideal value, which is the channel capacity obtained by conventional channel estimation. In other words, it can be seen that the method shown in Embodiment 1 of this disclosure is effective.

[0091] Furthermore, the channel capacity is significantly increased, particularly in the results obtained using the unitary matrix-based beamforming method shown in Proposal 1. This indicates that selecting a unitary matrix as the beamforming standard makes it possible to increase capacity.

[0092] Figure 12 is a graph showing the results of a second simulation according to Embodiment 1 of this disclosure. Here, the results of the simulation show the median channel capacitance when the element spacing of the transmitting antenna of the transmitting station 2 is 2.5λ.

[0093] As shown in the graph, as the number of ground antennas increases, the channel capacity obtained by simplified channel estimation asymptotically approaches the ideal value, which is the channel capacity obtained by conventional channel estimation. In other words, it can be seen that the method shown in Embodiment 1 of this disclosure is effective.

[0094] Furthermore, the channel capacity is significantly increased, particularly in the results obtained using the unitary matrix-based beamforming method shown in Proposal 1. This indicates that selecting a unitary matrix as the beamforming standard makes it possible to increase capacity.

[0095] The possible forms of disclosure are listed as an addendum.

[0096] [Note 1] A wireless communication system comprising a transmitting station and a receiving station equipped with one or more antennas, wherein the transmitting station is configured to perform the following: a process of acquiring location area information which is information of the area where the receiving station is located; a process of performing simplified channel estimation based on the location area information; a process of calculating beamforming weights based on the results of the simplified channel estimation; and a process of transmitting a signal by beamforming based on the weights, and the receiving station is configured to perform a process of separating the received signal. [Note 2] The wireless communication system according to Note 1, wherein the simplified channel estimation is achieved by assuming that the arriving wave is transmitted from the area and performing a plane wave approximation. [Note 3] The wireless communication system according to Note 1 or 2, wherein the weights are calculated based on the simplified channel acquired in the simplified channel estimation so as to achieve highly orthogonal beamforming. [Note 4] The wireless communication system according to Note 3, wherein the weights are calculated using a unitary matrix obtained by singular value decomposition of the simplified channel. [Note 5] The weight is calculated by determining the beam direction of the antenna in which the channel capacity is near-maximized, as described in any one of Notes 1 to 4 of the wireless communication system.

[0097] 2 transmitting stations 4 receiving stations 60 area 100 wireless communication system

Claims

1. A wireless communication system in which a transmitting station and a receiving station perform wireless communication, wherein the transmitting station is configured to perform the following processes: acquiring location area information which is information about the area in which the receiving station is located; performing a simplified channel estimation using plane wave approximation for a plurality of receiving stations belonging to the area based on the location area information; calculating beamforming weights based on the results of the simplified channel estimation; and transmitting a signal based on the weights.

2. A wireless communication method implemented by a wireless communication system in which a transmitting station and a receiving station communicate wirelessly, comprising: acquiring location area information which is information about the area in which the receiving station is located; performing a simplified channel estimation by plane wave approximation for a plurality of receiving stations belonging to the area based on the location area information; calculating beamforming weights based on the results of the simplified channel estimation; and transmitting a signal based on the weights.

3. A wireless communication device that performs wireless communication with a receiving station, the device being configured to perform the following steps: acquire location area information which is information about the area where the receiving station is located; perform a simplified channel estimation using plane wave approximation for a plurality of the receiving stations belonging to the area based on the location area information; calculate beamforming weights based on the results of the simplified channel estimation; and transmit a signal based on the weights.

4. A wireless communication program to be implemented by a wireless communication device having a processor and memory, which performs wireless communication with a receiving station, the program being stored in the memory and computer-readable, and including a program to cause the processor to perform the following: a process of acquiring location area information which is information of the area where the receiving station is located; a process of performing a simplified channel estimation by plane wave approximation for a plurality of the receiving stations belonging to the area based on the location area information; a process of calculating beamforming weights based on the results of the simplified channel estimation; and a process of transmitting a signal based on the weights.

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