Base station device, terminal device, and wireless communication method

Abstract

To provide a base station device, a terminal device, and a wireless communication method that reduces the computational overhead required for a base station device to select a codebook to feed back to a terminal device.SOLUTION: A base station device includes a selection unit that selects a predetermined transmission precoding matrix indicator when a terminal device is in a line-of-sight environment, and a communication unit that transmits the transmission precoding matrix indicator selected by the selection unit to the terminal device when receiving an uplink reference signal transmitted by the terminal device.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a base station device, a terminal device, and a wireless communication method. [Background technology]

[0002] In the uplink, the base station apparatus selects a Transmission Precoding Matrix Indicator (TPMI) index from a codebook based on an uplink reference signal transmitted by a terminal apparatus, and notifies the terminal apparatus of the selected TPMI index. The terminal device performs precoding based on the TPMI index notified from the base station device (for example, see Non-Patent Document 1). The base station device selects a transmission precoding matrix indicator index from a codebook based on an uplink reference signal transmitted by the terminal device, regardless of the environment in which the terminal device exists.

[0003] 2. Description of the Related Art Regarding wireless communication systems, there is known a technique for determining whether a system is in a line-of-site (LoS) environment or a non-line-of-sight (NLoS) environment (see, for example, Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] 3GPP, TS 38.211, NR; Physical channels and modulation, v17.5.0, 6.3.1.5 Precoding [Non-Patent Document 2] Chen Huang, Andreas F. Molisch, Ruisi He, Rui Wang, Pan Tang, Bo Ai, and Zhangdui Zhong, “Machine Learning-Enabled LOS / NLOS Identification for MIMO Systems in Dynamic Environments,” IEEE Transactions on Wireless Communications, vol. 19, NO. 6, pp. 3643-3657, June 2020 Summary of the Invention [Problem to be solved by the invention]

[0005] The base station device estimates a propagation channel matrix by using an uplink reference signal transmitted by a terminal device, and obtains a left singular matrix and a right singular matrix by performing singular value decomposition on the estimation result of the propagation channel matrix. If the base station device feeds back the right singular matrix to the terminal device as a precoder, the amount of calculation required for the singular value decomposition and the amount of data fed back will increase. An object of the present invention is to provide a base station apparatus, a terminal apparatus, and a wireless communication method that can reduce the overhead of the amount of calculation required for selecting a codebook that the base station apparatus feeds back to the terminal apparatus. [Means for solving the problem]

[0006] (1) One aspect of the present invention is a base station device comprising: a selection unit that selects a predetermined transmission precoding matrix indicator when a terminal device is in a line-of-sight environment; and a communication unit that transmits the transmission precoding matrix indicator selected by the selection unit to the terminal device when an uplink reference signal transmitted by the terminal device is received. (2) In one aspect of the present invention, in the base station device described in (1) above, the communication unit receives a physical uplink control channel transmitted by the terminal device, and the base station device further includes a determination unit that determines whether the physical uplink control channel received by the communication unit includes information indicating a line-of-sight environment, and the selection unit selects the transmission precoding matrix indicator that has been determined in advance when the determination unit determines that the physical uplink control channel includes information indicating a line-of-sight environment. (3) In one aspect of the present invention, in the base station device described in (1) above, the base station device further includes a judgment unit that judges whether the terminal device is in a line-of-sight environment based on an uplink reference signal transmitted by the terminal device, and the selection unit selects the transmission precoding matrix indicator that has been determined in advance when the judgment unit determines that the terminal device is in a line-of-sight environment. (4) In one aspect of the present invention, in the base station device described in (1) above, the base station device further includes a uniform rectangular array antenna, and the communication unit transmits the transmission precoding matrix indicator from the uniform rectangular array antenna to the terminal device equipped with a uniform rectangular array antenna. (5) In one aspect of the present invention, in the base station device described in (1) above, the base station device further includes a uniform circular array antenna, and the communication unit transmits the transmission precoding matrix indicator from the uniform circular array antenna to the terminal device equipped with a uniform circular array antenna. (6) In one aspect of the present invention, in the base station device described in (1) above, the base station device further includes a channel estimation unit that performs channel estimation based on an uplink reference signal, and the communication unit transmits to the terminal device the channel estimation result by the channel estimation unit and the transmission precoding matrix indicator selected by the selection unit.

[0007] (7) One aspect of the present invention is a terminal device comprising: a determination unit that determines whether a base station device is in a line-of-sight environment based on a downlink reference signal; a signal creation unit that creates a feedback signal to notify the base station device that it is in a line-of-sight environment when the determination unit determines that the base station device is in a line-of-sight environment; and a communication unit that transmits the feedback signal created by the signal creation unit to the base station device. (8) In one aspect of the present invention, in the terminal device described in (7) above, the signal creation unit creates the feedback signal by including information indicating that the environment is a line-of-sight environment in uplink control information of a physical uplink control channel. (9) In one aspect of the present invention, in the terminal device described in (7) above, the signal creation unit creates the feedback signal by including information indicating a line-of-sight environment in channel quality information of a physical uplink control channel. (10) In one aspect of the present invention, in the terminal device described in (7) above, the terminal device further includes a uniform rectangular array antenna, and the communication unit receives a transmission precoding matrix indicator transmitted by the base station device equipped with a uniform rectangular array antenna via the uniform rectangular array antenna. (11) In one aspect of the present invention, in the terminal device described in (7) above, the terminal device further includes a uniform circular array antenna, and the communication unit receives a precoding matrix indicator transmitted by the base station device equipped with a uniform circular array antenna via the uniform circular array antenna.

[0008] (12) One aspect of the present invention is a wireless communication method executed by a base station device, comprising: a step of selecting a predetermined transmission precoding matrix indicator when a terminal device is in a line-of-sight environment; and a step of transmitting the transmission precoding matrix indicator selected in the selection step to the terminal device when receiving an uplink reference signal transmitted by the terminal device. (13) One aspect of the present invention is a wireless communication method executed by a terminal device, comprising: a step of determining whether a base station device is in a line-of-sight environment based on a downlink reference signal; if it is determined in the determining step that the base station device is in a line-of-sight environment, a step of creating a feedback signal to notify the base station device that it is in a line-of-sight environment; and a step of transmitting the feedback signal created in the feedback signal creating step to the base station device. Effect of the Invention

[0009] According to the present invention, it is possible to provide a base station apparatus, a terminal apparatus, and a wireless communication method that can reduce the overhead of the amount of calculation required for the base station apparatus to select a codebook to be fed back to a terminal apparatus. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating an example of a configuration of a wireless communication system according to an embodiment of the present invention. [Diagram 2] 1 is a diagram illustrating a base station device and a terminal device included in a wireless communication system according to an embodiment of the present invention. [Diagram 3] 2 is a diagram illustrating an example of an antenna provided in a base station device and a terminal device according to the present embodiment. FIG. [Figure 4] FIG. 2 is a diagram illustrating an example of the operation of the wireless communication system according to the present embodiment. [Diagram 5] 11A and 11B are diagrams illustrating other examples of antennas provided in the base station device and the terminal device according to the present embodiment. [Figure 6] FIG. 11 is a diagram illustrating a base station device and a terminal device included in a wireless communication system according to a first modified example of an embodiment. [Figure 7] FIG. 11 is a diagram illustrating an example of an operation of the wireless communication system according to the first modification of the embodiment. [Figure 8] FIG. 11 is a diagram illustrating a base station device and a terminal device included in a wireless communication system according to a second modification of the embodiment. [Figure 9]FIG. 11 is a diagram illustrating an example of an operation of a wireless communication system according to a second modification of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Next, the base station device, the terminal device, and the wireless communication method of 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. In all the drawings for explaining the embodiment, the same reference numerals are used for the parts having the same functions, and the repeated description will be omitted. In addition, "based on XX" in this application means "based on at least XX," and includes cases where it is based on other elements in addition to XX. Furthermore, "based on XX" is not limited to cases where XX is used directly, but also includes cases where it is based on XX that has been calculated or processed. "XX" is any element (for example, any information).

[0012] (Wireless communication system configuration) 1 is a diagram showing an example of the configuration of a wireless communication system according to the present embodiment. An example of the wireless communication system 1 is a cellular communication system (mobile communication network) of a fifth generation mobile communication system (5G). However, the present invention is not limited to this, and the wireless communication system 1 may be, for example, a successor cellular communication system after 5G, or a wireless communication system other than a cellular system. The wireless system 1 includes a base station device 100 and a terminal device 200.

[0013] The base station device 100 and the terminal device 200 perform wireless communication. The base station device 100 performs MIMO (Multi-Input Multi-Output) transmission with the terminal device 200 using a modulation method such as phase shift keying or quadrature amplitude modulation. An example of the phase shift keying method is BPSK (Quadrature phase-shift keying), and an example of quadrature amplitude modulation is 16QAM (16 Quadrature Amplitude Modulation). The base station device 100 and the terminal device 200 each have multiple antennas, and transmit signals by multiplexing multiple streams (MIMO layers) according to the number of antennas.

[0014] The base station apparatus 100 selects a transmission precoding matrix indicator associated with a precoder that is determined in advance when the terminal apparatus 200 is in a line-of-sight environment. When the base station apparatus 100 receives an uplink reference signal transmitted by the terminal apparatus 200, the base station apparatus 100 transmits the selected transmission precoding matrix indicator to the terminal apparatus 200.

[0015] (Base station equipment) Fig. 2 is a diagram showing a base station apparatus and a terminal apparatus included in the wireless communication system according to this embodiment. Details of base station apparatus 100 will be described with reference to Fig. 2. Base station apparatus 100 includes antennas 101-1 to 101-j (j is an integer greater than 1), a communication unit 102, a channel estimation unit 104, a selection unit 106, and a storage unit 110. The antennas 101-1 to 101-j transmit and receive radio signals to and from the terminal device 200. An example of the antennas 101-1 to 101-j is a Uniform Rectangular Array (URA) antenna.

[0016] 3 is a diagram showing an example of antennas provided in a base station device and a terminal device according to this embodiment. The antennas 101-1 to 101-j are arranged two-dimensionally in a square on a substrate (not shown) to configure a URA antenna. For example, in the orthogonal x-axis and y-axis directions, the antennas 101-1 to 101-j are arranged at a first distance wTX in the x-axis direction and at a second distance hTX in the y-axis direction. As an example, a case where j is 4 will be described. In this case, the antennas 101-1 to 101-4 are arranged two-dimensionally in a square on a substrate (not shown) to form a URA antenna. In the example shown in Fig. 3, in the orthogonal x-axis and y-axis directions, two pairs of antenna elements (antennas 101-1 and 101-2, and antennas 101-3 and 101-4) are arranged at a first distance wTX in the x-axis direction, and two pairs of antenna elements (antennas 101-1 and 101-3, and antennas 101-2 and 101-4) are arranged at a second distance hTX in the y-axis direction. Fig. 3 further shows the center 101-C of the URA antenna. The first distance wTX and the second distance hTX are arbitrary and may be different. An example of the first distance wTX and the second distance hTX is half the wavelength λ1 (half wavelength: λ1 / 2) that has the highest intensity among the wavelengths included in the electromagnetic wave transmitted from the terminal device 200. Returning to FIG. 2, the explanation will be continued.

[0017] The communication unit 102 includes a receiving circuit that receives wireless signals (radio waves) from the multiple antennas 101-1 to 101-j and converts them into electrical signals, and a transmitting circuit that converts the electrical signals into wireless signals (radio waves) and transmits them from the multiple antennas 101-1 to 101-j. The storage unit 110 is realized by a hard disk drive (HDD), a flash memory, a random access memory (RAM), a read only memory (ROM), or the like. The storage unit 110 stores a codebook 108. The codebook 108 associates a plurality of codebooks (precoders) that can be set in the antenna of the terminal device 200 on the base station device 100 side with TPMI indices corresponding to each of the plurality of precoders. For example, each of the plurality of precoders is represented by a 4×4 matrix, and is classified into ranks 1 to 4.

[0018] The channel estimation unit 104 estimates a propagation channel matrix by performing channel estimation based on the uplink reference signal received by the communication unit 102. The channel estimation unit 104 obtains a left singular matrix and a right singular matrix by performing singular value decomposition on the estimation result of the propagation channel matrix. The selection unit 106 acquires a right singular matrix from the channel estimation unit 104, selects a precoder from the codebook 108 based on the acquired right singular matrix, and selects a TPMI indicator associated with the selected precoder. For example, the selection unit 106 selects a precoder so that the channel capacity is maximized. However, when the line of sight between the terminal device 200 and the base station device 100 is ensured, that is, when the terminal device 200 is in a line of sight environment, the selection unit 106 selects a TPMI indicator associated with a precoder that has been determined in advance. For example, the selection unit 106 may select a precoder included in rank 3, or may select a precoder included in rank 4.

[0019] The signal generating unit 107 generates a downlink signal. Specifically, the signal generating unit 107 acquires the TPMI indicator selected by the selecting unit 106, and generates a feedback signal including the acquired TPMI indicator. In addition, the signal generating unit 107 generates a downlink reference signal. The communication unit 102 transmits the feedback signal generated by the signal generation unit 107 to the terminal device 200 from the antennas 101-1 to 101-j.

[0020] The channel estimation unit 104, the selection unit 106 and the signal creation unit 107 are realized by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a computer program (software) stored in the storage unit 110. Furthermore, some or all of these functional units may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware.

[0021] (Terminal Device) 2, details of terminal device 200 will be described. Terminal device 200 includes antennas 201-1 to 201-k (k is an integer greater than 1), a communication unit 202, a precoding unit 204, a signal generation unit 207, and a storage unit 210. The antennas 201-1 to 201-k transmit and receive radio signals to and from the base station device 100. An example of the antennas 201-1 to 201-k is a uniform rectangular array antenna.

[0022] An example of the antennas 201-1 to 201-k will be described with reference to Fig. 3. The antennas 201-1 to 201-k are arranged two-dimensionally in a square on a substrate (not shown) to configure a URA antenna. For example, in the orthogonal x-axis and y-axis directions, the antennas 201-1 to 201-k are arranged at a first distance wRX in the x-axis direction and at a second distance hRX in the y-axis direction. As an example, a case where k is 4 will be described. The antennas 201-1 to 201-4 are arranged two-dimensionally in a square on a substrate (not shown) to form a URA antenna. In the example shown in Fig. 3, in the orthogonal x-axis and y-axis directions, two pairs of antenna elements (antennas 201-1 and 201-2, and antennas 201-3 and 201-4) are arranged at a first distance wRX in the x-axis direction, and two pairs of antenna elements (antennas 201-1 and 201-3, and antennas 201-2 and 201-4) are arranged at a second distance hRX in the y-axis direction. Fig. 3 further shows the center 201-C of the URA antenna. The first distance wRX and the second distance hRX are arbitrary and may be different. An example of the first distance wRX and the second distance hRX is half the wavelength λ2 (half wavelength: λ2 / 2) that has the highest intensity among the wavelengths included in the electromagnetic wave transmitted from the base station device 100. Returning to FIG. 2, the explanation will be continued.

[0023] The communication unit 202 includes a receiving circuit that receives wireless signals (radio waves) from the multiple antennas 201-1 to 201-k and converts them into electrical signals, and a transmitting circuit that converts the electrical signals into wireless signals (radio waves) and transmits them from the multiple antennas 201-1 to 201-k. The storage unit 210 is realized by a HDD, a flash memory, a RAM, a ROM, etc. The storage unit 210 stores a codebook 208. The codebook 208 is similar to the codebook 108.

[0024] The precoding unit 204 acquires a feedback signal received by the communication unit 202. The precoding unit 204 acquires a precoder associated with a TPMI indicator included in the acquired feedback signal from the codebook 208 in the storage unit 210. The precoding unit 204 performs precoding on the multiple antennas 201-1 to 201-k based on the acquired precoder. The signal generating unit 207 generates an uplink signal. Specifically, the signal generating unit 207 generates an uplink reference signal, a physical uplink control channel, a physical uplink shared channel, and the like. The communication unit 202 transmits the uplink signals generated by the signal generation unit 207 to the base station device 100 from the multiple antennas 201-1 to 201-k.

[0025] The precoding unit 204 and the signal generating unit 207 are realized by, for example, a hardware processor such as a CPU executing a computer program (software) stored in the storage unit 210. Furthermore, some or all of these functional units may be realized by hardware (including circuitry) such as an LSI, ASIC, FPGA, or GPU, or may be realized by a combination of software and hardware.

[0026] (Operation of wireless communication system) Fig. 4 is a diagram showing an example of the operation of the wireless communication system 1 according to this embodiment. With reference to Fig. 4, the operation when the terminal device 200 is in a line-of-sight environment with respect to the base station device 100 will be described. (Step S1-1) In the base station device 100, the selection unit 106 selects a TPMI indicator associated with a predetermined precoder because the terminal device 200 is in a line-of-sight environment. (Step S2-1) In the terminal device 200, the signal generating unit 207 generates an uplink reference signal. An example of the uplink reference signal is a Sounding Reference Signal (SRS).

[0027] (Step S3-1) In the terminal device 200, the communication unit 202 acquires an uplink reference signal from the signal generation unit 207, and transmits the uplink reference signal to the base station device 100 from the antennas 201-1 to 201-k. (Step S4-1) In the base station device 100, the communication unit receives an uplink reference signal transmitted by the terminal device 200. The channel estimation unit 204 performs channel estimation based on the uplink reference signal received by the communication unit .

[0028] (Step S5-1) In the base station apparatus 100, the signal generation unit 107 acquires the TPMI indicator selected by the selection unit 106, and generates a downlink feedback signal. (Step S6-1) In the base station device 100, the communication unit 102 acquires the feedback signal generated by the signal generation unit 107, and transmits it to the terminal device 200 from the antennas 101-1 to 101-j.

[0029] (Step S7-1) In the terminal device 200, the communication unit 202 receives a feedback signal transmitted by the base station device 100. The precoding unit 204 acquires the feedback signal received by the communication unit 202, and acquires a precoder associated with a TPMI indicator included in the acquired feedback signal from the codebook 208 in the storage unit 210. The precoding unit 204 performs precoding for the multiple antennas 201-1 to 201-k based on the acquired precoder.

[0030] (Step S8-1) In the terminal device 200, the signal generation unit 207 generates an uplink signal. For example, the signal generation unit 207 generates a Physical Uplink Shared channel (PUSCH). (Step S9-1) In the terminal device 200, the communication unit 202 transmits the uplink signal generated by the signal generation unit 207 to the base station device 100 from the antennas 101-1 to 101-j. Thereafter, the base station device 100 continues to transmit the predetermined TPMI indicator until the terminal device 200 is in a non-line-of-sight environment.

[0031] In the above embodiment, the antennas 101-1 to 101-j are arranged two-dimensionally in a square to form a URA antenna, but the present invention is not limited to this example. For example, the antennas 101-1 to 101-j may form a Uniform Circular Array (UCA) antenna.

[0032] FIG. 5 is a diagram showing another example of antennas provided in the base station device and the terminal device according to this embodiment. The antennas 101-1 to 101-j are arranged two-dimensionally in a circular ring shape at equal intervals on a substrate (not shown) to form a UCA antenna. For example, in the orthogonal x-axis and y-axis directions, the antennas 101-1 to 101-j are arranged at intervals of rTX×θm [degrees] along a circumference of a radius rTX. As an example, a case where j is 12 will be described. In this case, the antenna elements (antennas 101-1 to 101-j) are arranged at intervals of rTX×30 degrees along a circumference of a radius rTX. FIG. 5 further shows the center 101-C of the UCA antenna. The radius rTX is arbitrary.

[0033] In the above embodiment, as an example of antennas included in the terminal device 200, a case has been described in which the antennas 201-1 to 201-k are arranged two-dimensionally in a square to form a URA antenna, but this is not limiting. For example, the antennas 201-1 to 201-k may form a UCA antenna.

[0034] The following description will be made with reference to FIG. 5. The antennas 201-1 to 201-k are two-dimensionally arranged in a circular ring shape at equal intervals on a substrate (not shown) to form a UCA antenna. For example, in the orthogonal x-axis and y-axis directions, the antennas 201-1 to 201-k are arranged at intervals of rRX×θm [degrees] along a circumference of a radius rRX. As an example, a case where k is 12 will be described. In this case, the antenna elements (antennas 201-1 to 201-k) are arranged at intervals of rRX×30 degrees along a circumference of a radius rRX. FIG. 5 further shows the center 201-C of the UCA antenna. The radius rRX is arbitrary.

[0035] In the above-described embodiment, the base station device 100 may perform wireless communication with a plurality of terminal devices 100.

[0036] The base station device 100 according to this embodiment includes a selection unit 106 that selects a predetermined transmission precoding matrix indicator when the terminal device 200 is in a line-of-sight environment, and a communication unit 102 that transmits the transmission precoding matrix indicator selected by the selection unit 106 to the terminal device 200 when receiving an uplink reference signal transmitted by the terminal device 200.

[0037] With this configuration, the base station apparatus 100 can select a transmission precoding matrix indicator that is determined in advance when the terminal apparatus 200 is in a line-of-sight environment, and transmit the selected transmission precoding matrix indicator to the terminal apparatus 200. Therefore, compared with the case where the base station apparatus 100 selects a transmission precoding matrix indicator based on an uplink reference signal transmitted by the terminal apparatus 200, it is possible to reduce the overhead of the amount of calculation required for selecting a precoder. This will, for example, make it possible to improve the overall service quality in wireless networks, thereby contributing to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0038] Base station apparatus 100 further includes a uniform rectangular array antenna, and communication section 102 transmits the transmission precoding matrix indicator from the uniform rectangular array antenna to terminal apparatus 200 including the uniform rectangular array antenna. Base station apparatus 100 further includes a uniform circular array antenna, and communication section 102 transmits the transmission precoding matrix indicator from the uniform circular array antenna to terminal apparatus 200 including the uniform circular array antenna.

[0039] With this configuration, the derived channel matrix becomes a circulant matrix, and therefore the optimal precoder becomes a unitary matrix in the base station apparatus 100. Therefore, even if the base station apparatus 100 selects a transmission precoding matrix indicator associated with the determined precoder and transmits it to the terminal apparatus 200 without selecting a transmission precoding matrix indicator based on the uplink reference signal, the communication quality can be ensured.

[0040] In the base station device 100, the base station device 100 further includes a channel estimation unit 104 that performs channel estimation based on the uplink reference signal, and the communication unit 102 transmits the channel estimation result by the channel estimation unit and the transmission precoding matrix indicator selected by the selection unit 106 to the terminal device 200. With this configuration, the channel estimation result can be transmitted to terminal device 200 together with a predetermined transmission precoding matrix indicator.

[0041] (First Modification of the Embodiment) 6 is a diagram showing a base station device and a terminal device included in a wireless communication system according to Modification 1 of the embodiment. The wireless communication system 2 according to Modification 1 of the embodiment includes a base station device 300 and a terminal device 400. The wireless communication system 2 is different from the wireless communication system 1 in the following respects. The terminal device 400 determines whether the base station device 300 is in a line-of-sight environment based on the downlink reference signal. When the terminal device 400 determines that the base station device 200 is in a line-of-sight environment, the terminal device 400 creates an uplink signal including information indicating that the base station device 200 is in a line-of-sight environment, and transmits the uplink signal to the base station device 300. The base station device 300 receives an uplink signal transmitted by the terminal device 400, and determines whether the received uplink signal includes information indicating a line-of-sight environment. When the base station device 300 determines that the uplink signal includes information indicating a line-of-sight environment, the base station device 300 selects a transmission precoding matrix indicator associated with a precoder that has been determined in advance.

[0042] (Base station equipment) The details of the base station device 300 will be described with reference to Fig. 6. The base station device 300 further includes a determination unit 305 in addition to the base station device 100. The determination unit 305 acquires an uplink signal received by the communication unit 102, and determines whether or not the acquired uplink signal includes information indicating a line-of-sight environment. When the uplink signal includes information indicating a line-of-sight environment, the determination unit 305 notifies the selection unit 106 that the environment is a line-of-sight environment. When the determining unit 305 notifies the selecting unit 106 that the terminal is in a line-of-sight environment, the selecting unit 106 selects a TPMI indicator associated with a pre-determined precoder.

[0043] (Terminal Device) The details of the terminal device 400 will be described with reference to Fig. 6. The terminal device 400 further includes a determination unit 405 in the terminal device 200. The determination unit 405 acquires a downlink reference signal received by the communication unit 202, and determines whether or not the base station device 400 is in a line-of-sight environment based on the acquired downlink reference signal.

[0044] Specifically, when it is determined whether or not the base station device 300 is actually in a line-of-sight environment with respect to the terminal device 400, the determination unit 405 determines whether or not the base station device 300 is in a line-of-sight environment by inputting the characteristic parameters of the downlink reference signal received by the communication unit 202 into the learned model 406 in which the characteristic parameters, etc. of the downlink reference signal received by the terminal device 400 are already stored. An example of the characteristic parameter is the Rician K-factor. The Rician K-factor is defined as the ratio of the power of the (possible) dominant multipath component (usually LOS) to the power of the remaining multipath components. As an example of the characteristic parameter, at least one of the maximum power, kurtosis, skewness, rise time and delay spread of the received power, the difference between the emission angle and the arrival angle, the angular spread of the emission angle and the arrival angle, and the rate of change of the emission angle and the arrival angle may be used instead of or together with the Rician K-factor. The kurtosis of the received power is defined as the ratio of the fourth moment to the second moment of the amplitude of the received signal. Hereinafter, the characteristic parameters related to the generation of the learned model 406 (downlink reference signals for which the base station device 300 has actually determined whether or not the device 400 is in a line-of-sight environment and for which the characteristic parameters, etc. of the downlink reference signals have been stored) are referred to as the model target.

[0045] Generation of the trained model 406 will be described. The trained model 406 is generated by a training model generation device (not shown). That is, the training model generation device generates the trained model 406. Note that the terminal device 400 may include the training model generation device, or a device different from the terminal device 400 may be the training model generation device. That is, the terminal device 400 may generate the trained model 406, or a device different from the terminal device 400 may generate the trained model 406.

[0046] The learning model generation device trains a learning model (a model that is the basis of the learned model 406) using a learning data set in which input samples are characteristic parameters of a downlink reference signal to be modeled, and output samples are information indicating whether the base station device 300 that transmitted the downlink reference signal is in a line-of-sight environment, thereby generating the learned model 406. For example, a support vector machine (SVC), a random forest (RF), or an artificial neural network (ANN) may be used. An input sample is data that is input to the input layer when training a learning model. An output sample is data (teacher data) that is the correct answer to be compared with the output value output from the output layer when training a learning model. An input sample and an output sample are paired, and a learning dataset is made up of multiple pairs.

[0047] The learning model generation device inputs an input sample into the input layer of the learning model, calculates the error between the output value output from the output layer and the output sample (teacher data) corresponding to the input sample for all pairs, changes the parameters of the learning model (trains the learning model) so as to minimize the error, and generates a learned model 406. The learned model 406 generated as described above is received by the terminal device 400 from the learning model generation device via a network or medium, and is acquired by the determination unit 405.

[0048] The following describes a process of determining whether the base station device 300 is in a line-of-sight environment using the trained model 406. The determination unit 406 derives characteristic parameters and the like from a downlink reference signal to be determined, inputs the derived characteristic parameters to the trained model 406, and obtains an output value from the trained model 406.

[0049] The signal generating unit 207 acquires the result of the determination as to whether or not the base station device 300 is in a line-of-sight environment from the determining unit 406. When the acquired result of the determination as to whether or not the base station device 300 is in a line-of-sight environment indicates that the base station device 300 is in a line-of-sight environment, the signal generating unit 207 generates an uplink signal including information indicating that the base station device 300 is in a line-of-sight environment. Specifically, the signal creation unit 207 introduces a 1-bit identifier into uplink control information (UCI) of a physical uplink control channel (PUCCH). The signal creation unit 207 stores "1" in the 1 bit introduced into the uplink control information. The communication unit 202 transmits the uplink signal (physical uplink control channel) generated by the signal generation unit 207 to the base station device 100 from the antennas 201-1 to 201-k.

[0050] (Operation of wireless communication system) Fig. 7 is a diagram showing an example of the operation of the wireless communication system according to the first modification of the embodiment. With reference to Fig. 7, the operation when the base station device 300 is in a line-of-sight environment with respect to the terminal device 400 will be described. (Step S1-2) In the base station device 300, the signal generation unit 107 generates a downlink reference signal. The communication unit 102 transmits the downlink reference signal from the antennas 100-1 to 100-j. An example of the downlink reference signal is a Channel State Information-Reference Signal / Synchronization Signal Block (CSI-RS / SSB (Channel State Information-Reference Signal / Synchronization Signal Block)).

[0051] (Step S2-2) In the terminal device 400, the communication unit 202 receives the downlink reference signal transmitted by the base station device 300. The determination unit 405 acquires the downlink reference signal received by the communication unit 202, and determines whether or not the base station device 400 is in a line-of-sight environment based on the acquired downlink reference signal. Here, the description will continue for the case where the terminal device 400 determines that the base station device 400 is in a line-of-sight environment. (Step S3-2) In the terminal device 400, the signal generating unit 207 generates an uplink signal including information indicating that the terminal device 400 is in a line-of-sight environment. (Step S4-2) In the terminal device 400, the communication unit 202 transmits the uplink signals generated by the signal generation unit 207 to the base station device 100 from the antennas 201-1 to 201-k.

[0052] (Step S5-2) In the base station device 300, the communication unit 102 receives the uplink signal transmitted by the terminal device 200. The determination unit 305 acquires the uplink signal received by the communication unit 102 and determines whether or not the uplink signal includes information indicating a line-of-sight environment. Since the uplink signal includes information indicating a line-of-sight environment, the determination unit 305 notifies the selection unit 106 that the environment is a line-of-sight environment. When the selection unit 106 is notified by the determination unit 305 that the terminal device 200 is in a line-of-sight environment, the selection unit 106 selects a TPMI indicator associated with a precoder that has been determined in advance. Steps S6-2 to S12-2 can be implemented by steps S3-1 to S9-1, so a description thereof will be omitted.

[0053] In the modified example of the above-described embodiment, the signal creation unit 207 sets the one bit introduced into the uplink control information of the physical uplink control channel to “1” when the result of determining whether the acquired base station device 300 is in a line-of-sight environment indicates that the base station device 300 is in a line-of-sight environment, but this example is not limited to this. For example, when the acquired result of determining whether the base station device 300 is in a line-of-sight environment indicates that the base station device 300 is in a line-of-sight environment, the signal generating unit 207 may notify that the base station device 300 is in a line-of-sight environment by setting a predetermined bit, for example, one bit, of a Channel Quality Indicator (CQI) of the physical uplink control channel to “1.”

[0054] According to the wireless communication system 2 relating to the first variant of the embodiment, in the base station device 300, the communication unit 102 receives the physical uplink control channel transmitted by the terminal device 400, and the base station device 300 further includes a determination unit 305 that determines whether or not the physical uplink control channel received by the communication unit 102 includes information indicating a line-of-sight environment, and the selection unit 306 selects a predetermined transmission precoding matrix indicator when the determination unit 305 determines that the physical uplink control channel includes information indicating a line-of-sight environment.

[0055] With this configuration, when the physical uplink control channel transmitted by the terminal device 400 includes information indicating a line-of-sight environment, the base station device 300 can select a transmission precoding matrix indicator associated with a precoder determined in advance and transmit the transmission precoding matrix indicator to the terminal device 200. Therefore, compared with the case where the base station device 100 selects a transmission precoding matrix indicator based on the uplink reference signal transmitted by the terminal device 200, the overhead of the amount of calculation required for selecting a precoder can be reduced.

[0056] According to a wireless communication system 2 relating to a modified example of the embodiment, the terminal device 400 includes a determination unit 405 that determines whether the base station device 300 is in a line-of-sight environment based on a downlink reference signal, a signal creation unit 207 that creates a feedback signal for notifying the base station device 300 that it is in a line-of-sight environment when the determination unit 405 determines that the base station device 300 is in the line-of-sight environment, and a communication unit 200 that transmits the feedback signal created by the signal creation unit 207 to the base station device 300.

[0057] With this configuration, when the base station device 300 is in a line-of-sight environment, the terminal device 400 can notify the base station device 300 that it is in a line-of-sight environment. Therefore, the base station device 300 can select a transmission precoding matrix indicator that is determined in advance based on the notified information, and transmit the selected transmission precoding matrix indicator to the terminal device 400.

[0058] Furthermore, in the terminal device 400, the signal generating unit 207 generates a feedback signal by including information indicating a line-of-sight environment in the uplink control information of the physical uplink control channel. Furthermore, in the terminal device 400, the signal generating unit 207 generates a feedback signal by including information indicating a line-of-sight environment in the channel quality signal of the physical uplink control channel. By configuring in this way, the terminal device 400 can notify the base station device 300 that it is in a line-of-sight environment by using the physical uplink control channel. Therefore, it is not necessary to provide a new signal for notifying that it is in a line-of-sight environment, and the notification can be made by using an existing signal.

[0059] Terminal device 400 further includes a uniform rectangular array antenna, and communication section 202 transmits the transmission precoding matrix indicator from the uniform rectangular array antenna to base station apparatus 300 which is also equipped with a uniform rectangular array antenna. Terminal device 400 further includes a uniform circular array antenna, and communication section 202 transmits the transmission precoding matrix indicator from the uniform circular array antenna to base station apparatus 300 which is also equipped with the uniform circular array antenna.

[0060] With this configuration, the derived channel matrix becomes a circulant matrix, and therefore the optimal precoder becomes a unitary matrix in the base station apparatus 300. Therefore, even if the base station apparatus 300 selects a transmission precoding matrix indicator associated with the determined precoder and transmits it to the terminal apparatus 200 without selecting a transmission precoding matrix indicator based on the uplink reference signal, the communication quality can be ensured.

[0061] (Modification 2 of the embodiment) 8 is a diagram showing a base station device and a terminal device included in a wireless communication system according to Modification 2 of the embodiment. The wireless communication system 3 according to Modification 2 of the embodiment includes a base station device 500 and a terminal device 200. The wireless communication system 3 differs from the wireless communication system 1 in the following respects: The base station device 500 determines whether the terminal device 200 is in a line-of-sight environment based on an uplink reference signal transmitted by the terminal device 200, and selects a transmission precoding matrix indicator that has been determined in advance when it is determined that the terminal device 200 is in a line-of-sight environment.

[0062] (Base station equipment) The details of the base station device 500 will be described with reference to Fig. 8. The base station device 500 further includes a determination unit 505 in the base station device 100. The determination unit 505 acquires an uplink reference signal received by the communication unit 102, and determines whether or not the terminal device 200 is in a line-of-sight environment based on the acquired uplink reference signal.

[0063] Specifically, when the determination unit 505 determines whether the terminal device 200 is actually in a line-of-sight environment with respect to the base station device 500, the determination unit 505 determines whether the terminal device 200 is in a line-of-sight environment by inputting the characteristic parameters of the uplink reference signal received by the communication unit 102 into the learned model 506 in which the characteristic parameters, etc. of the uplink reference signal received by the base station device 500 are already stored. An example of the characteristic parameter is the Rice K factor. Alternatively, instead of or together with the Rice K factor, at least one of the maximum power, kurtosis, skewness, rise time and delay spread of the received power, the difference between the radiation angle and the arrival angle, the angle spread of the radiation angle and the arrival angle, and the rate of change of the radiation angle and the arrival angle may be used as an example of the characteristic parameter. Hereinafter, the characteristic parameters related to the generation of the learned model 506 (the uplink reference signal for which it has been determined whether the terminal device 600 is actually in a line-of-sight environment with respect to the base station device 500, and for which the characteristic parameters, etc. of the uplink reference signal have been stored) are referred to as the model target.

[0064] Generation of the trained model 506 will be described. The trained model 506 is generated by a trained model generation device (not shown). That is, the trained model generation device generates the trained model 506. Note that the base station device 500 may include the trained model generation device, or a device different from the base station device 500 may be the trained model generation device. That is, the base station device 500 may generate the trained model 406, or a device different from the base station device 500 may generate the trained model 506.

[0065] The learning model generation device trains a learning model (a model that is the basis of the learned model 506) using a learning data set in which input samples are characteristic parameters and the like of an uplink reference signal to be modeled, and output samples are information indicating whether or not the terminal device 200 that transmitted the uplink reference signal is in a line-of-sight environment, thereby generating the learned model 506. For example, a support vector machine, a random forest, or an artificial neural network may be used. The input sample is data input to an input layer when training the learning model. An output sample is data (teacher data) that is the correct answer to be compared with the output value output from the output layer during training of a learning model. An input sample and an output sample are paired, and a learning dataset is composed of multiple pairs.

[0066] The learning model generation device inputs an input sample to an input layer of the learning model, calculates an error between an output value output from the output layer and an output sample (teacher data) corresponding to the input sample for every pair, changes the parameters of the learning model (trains the learning model) so as to minimize the error, and generates a learned model 506. The learned model 506 generated as described above is received by the base station device 500 from the learning model generation device via a network or medium, and is acquired by the determination unit 505.

[0067] A process of determining whether or not the terminal device 600 is in a line-of-sight environment using the trained model 506 will be described. The determination unit 505 derives characteristic parameters and the like from the uplink reference signal to be determined, inputs the derived characteristic parameters to the trained model 506, and obtains an output value from the trained model 506. The selection unit 106 acquires the result of determining whether or not the base terminal device 600 is in a line-of-sight environment from the determination unit 505. The selection unit 106 selects a TPMI indicator associated with a precoder that is determined in advance when the result of determining whether or not the base terminal device 600 is in a line-of-sight environment from the determination unit 505 indicates that the terminal device 200 is in a line-of-sight environment.

[0068] (Operation of wireless communication system) Fig. 9 is a diagram showing an example of the operation of the wireless communication system according to the second modification of the embodiment. With reference to Fig. 9, the operation when the terminal device 200 is in a line-of-sight environment with respect to the base station device 500 will be described. (Step S1-3) In the terminal device 200, the signal generation unit 207 generates an uplink reference signal. The communication unit 202 transmits the uplink reference signal from the antennas 201-1 to 201-k. An example of the uplink reference signal is a sounding reference signal.

[0069] (Step S2-3) In the base station device 500, the communication unit 102 receives the uplink reference signal transmitted by the terminal device 200. The determination unit 505 acquires the uplink reference signal received by the communication unit 102, and determines whether or not the terminal device 200 is in a line-of-sight environment based on the acquired uplink reference signal. Here, the description will continue for the case where the base station device 500 determines that the terminal device 400 is in a line-of-sight environment.

[0070] (Step S3-3) In the base station device 500, the selection unit 106 acquires the result of determining whether or not the base terminal device 600 is in a line-of-sight environment from the determination unit 505. The selection unit 106 selects a TPMI indicator associated with a precoder that is determined in advance when the result of determining whether or not the base terminal device 600 is in a line-of-sight environment from the determination unit 505 indicates that the terminal device 200 is in a line-of-sight environment. Steps S4-3 to S10-3 can be implemented by steps S3-1 to S9-1, so a description thereof will be omitted.

[0071] According to the wireless communication system 3 relating to the second embodiment variant, the base station device 500 further includes a determination unit 505 in the base station device 100 that determines whether the terminal device 200 is in a line-of-sight environment based on the uplink reference signal transmitted by the terminal device 200, and the selection unit selects a transmission precoding matrix indicator that has been determined in advance when the determination unit 505 determines that the terminal device 200 is in a line-of-sight environment.

[0072] With this configuration, when the base station device 500 determines that the terminal device 200 is in a line-of-sight environment based on the uplink reference signal transmitted by the terminal device 200, the base station device 500 can select a predetermined transmission precoding matrix indicator and transmit it to the terminal device 200. Therefore, compared with the case where the base station device 500 selects a transmission precoding matrix indicator based on the uplink reference signal transmitted by the terminal device 200, it is possible to reduce the overhead of the amount of calculation required for selecting a precoder.

[0073] Although the embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like within the scope of the present invention are also included. For example, a computer program for realizing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the computer program recorded on the recording medium may be read into a computer system and executed. Note that the "computer system" referred to here may include hardware such as an OS and peripheral devices.

[0074] In addition, "computer-readable recording media" refers to writable non-volatile memories such as flexible disks, optical magnetic disks, ROMs, and flash memories, portable media such as DVDs (Digital Versatile Discs), and storage devices such as hard disks built into computer systems. Furthermore, "computer-readable recording media" also includes those that hold programs for a certain period of time, such as volatile memory (e.g., DRAM (Dynamic Random Access Memory)) inside computer systems that act as servers or clients when a computer program is transmitted via a network such as the Internet or a communication line such as a telephone line.

[0075] The program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium, or by a transmission wave in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for realizing part of the functions described above. Furthermore, the above-mentioned functions may be realized in combination with a program already recorded in the computer system, that is, a so-called differential file (differential program). [Explanation of symbols]

[0076] 1, 2, 3... wireless communication system, 100, 300, 500... base station device, 101-1 to 101-j... antenna, 102... communication unit, 104... channel estimation unit, 106... selection unit, 107... signal creation unit, 108... codebook, 110... storage unit, 200, 400... base station device, 201-1 to 201-k... antenna, 202... communication unit, 204... precoding unit, 207... signal creation unit, 208... codebook, 210... storage unit, 305... determination unit, 405... determination unit, 406... trained model, 505... determination unit, 506... trained model

Claims

1. A selection unit that selects a predetermined transmission precoding matrix indicator when the terminal device is in a line-of-sight environment; a communication unit that transmits the transmission precoding matrix indicator selected by the selection unit to the terminal device when receiving an uplink reference signal transmitted by the terminal device; A base station device comprising:

2. The communication unit receives a physical uplink control channel transmitted by the terminal device, The base station device, A determination unit that determines whether or not the physical uplink control channel received by the communication unit includes information indicating a line-of-sight environment. Further equipped with The base station apparatus according to claim 1 , wherein the selection unit selects the transmission precoding matrix indicator that is determined in advance when the determination unit determines that the physical uplink control channel includes information indicating a line-of-sight environment.

3. A determination unit that determines whether the terminal device is in a line-of-sight environment based on an uplink reference signal transmitted by the terminal device. Further equipped with The base station apparatus according to claim 1 , wherein the selection unit selects the transmission precoding matrix indicator that is determined in advance when the determination unit determines that the terminal apparatus is in a line-of-sight environment.

4. Uniform rectangular array antenna Further equipped with The base station apparatus according to claim 1 , wherein the communication unit transmits the transmission precoding matrix indicator from the uniform rectangular array antenna to the terminal apparatus equipped with a uniform rectangular array antenna.

5. Uniform circular array antenna Further equipped with The base station apparatus according to claim 1 , wherein the communication unit transmits the transmission precoding matrix indicator from the uniform circular array antenna to the terminal apparatus equipped with a uniform circular array antenna.

6. A channel estimation unit that performs channel estimation based on an uplink reference signal Further equipped with The base station apparatus according to claim 1 , wherein the communication unit transmits, to the terminal apparatus, a channel estimation result by the channel estimator and the transmission precoding matrix indicator selected by the selector.

7. a determination unit that determines whether the base station device is in a line-of-sight environment based on a downlink reference signal; a signal generating unit configured to generate a feedback signal for notifying the base station device that it is in a line-of-sight environment when the determining unit determines that the base station device is in a line-of-sight environment; a communication unit that transmits the feedback signal generated by the signal generation unit to the base station device; A terminal device comprising:

8. The terminal device according to claim 7 , wherein the signal generating unit generates the feedback signal by including information indicating a line-of-sight environment in uplink control information of a physical uplink control channel.

9. The terminal device according to claim 7 , wherein the signal generating unit generates the feedback signal by including information indicating a line-of-sight environment in channel quality information of a physical uplink control channel.

10. Uniform rectangular array antenna Further equipped with The terminal device according to claim 7 , wherein the communication unit receives, by the uniform rectangular array antenna, a transmission precoding matrix indicator transmitted by the base station device equipped with a uniform rectangular array antenna.

11. Uniform circular array antenna Further equipped with The terminal device according to claim 7 , wherein the communication unit receives, by the uniform circular array antenna, a precoding matrix indicator transmitted by the base station device equipped with a uniform circular array antenna.

12. selecting a predetermined transmission precoding matrix indicator when the terminal device is in a line-of-sight environment; transmitting the transmission precoding matrix indicator selected in the selecting step to the terminal device when receiving an uplink reference signal transmitted by the terminal device; A wireless communication method executed by a base station device.

13. determining whether the base station device is in a line-of-sight environment based on a downlink reference signal; generating a feedback signal for notifying the base station device that it is in a line-of-sight environment when it is determined that the base station device is in a line-of-sight environment in the determining step; transmitting the feedback signal generated in the generating step to the base station device; A wireless communication method executed by a terminal device.

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