Base station device, terminal device, control method, and program that enable efficient compensation of nonlinear distortion in relay device

Abstract

To enable efficient compensation of nonlinear distortion in a repeater device.SOLUTION: A base station device acquires, from a relay device that relays communications between a base station device and a terminal device, first information capable of identifying nonlinear distortion caused by a power amplifier possessed by the relay device, and notifies the terminal device of second information used when the terminal device compensates for the nonlinear distortion caused by the power amplifier of the relay device.SELECTED DRAWING: Figure 12

Description

[Technical Field]

[0001] The present invention relates to a technique for compensating for nonlinear distortion in a repeater device. [Background technology]

[0002] In wireless communications, a device on the transmitting side of a signal uses a power amplifier to amplify and output the power of a signal to be transmitted. This power amplifier is usually used in an operating region where nonlinear distortion does not occur in the signal waveform. However, such an operating region where nonlinear distortion does not occur is not necessarily power efficient. In response to this, a technology that modifies the waveform to compensate for nonlinear distortion can be used to operate the power amplifier near the saturation region where nonlinear distortion occurs, thereby improving power efficiency. Such a technology is, for example, digital pre-distortion (DPD) in the transmitting device and digital post-distortion (DPoD) in the receiving device. Non-Patent Document 1 describes that a UE provides information to a base station device to make it use DPD, and that a reference signal or the like is transmitted to make a terminal device use DPoD. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP (registered trademark) Contribution, R1-2213007 Summary of the Invention [Problem to be solved by the invention]

[0004] To extend the communication distance in wireless communication, relay devices such as wireless repeaters can be used. To improve the power efficiency of systems that use such relay devices, it is expected that the power amplifiers used in the relay devices will also operate near the saturation region where nonlinear distortion may occur. In this case, nonlinear distortion compensation processing using DPD or DPoD can be performed taking into account the nonlinear distortion in the relay devices. [Means for solving the problem]

[0005] The present invention provides a technique that enables efficient compensation of nonlinear distortion in a repeater.

[0006] A base station device according to one embodiment of the present invention has an acquisition means for acquiring, from the relay device, first information capable of identifying nonlinear distortion caused by a power amplifier possessed by the relay device that relays communications between the base station device and a terminal device, and a notification means for notifying the terminal device of second information used when the terminal device compensates for the nonlinear distortion caused by the power amplifier of the relay device.

[0007] A terminal device according to one embodiment of the present invention comprises: a receiving means for receiving, from the base station device, second information used when compensating for nonlinear distortion caused by a power amplifier of the relay device, the second information being based on first information capable of identifying nonlinear distortion caused by a power amplifier possessed by the relay device that relays communication between the base station device and the terminal device; and a processing means for performing compensation processing for nonlinear distortion caused by the power amplifier of the relay device in communication with the base station device via the relay device, based on the second information. [Effects of the Invention]

[0008] According to the present invention, it is possible to efficiently compensate for nonlinear distortion in a repeater device. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. [Figure 2] FIG. 10 is a diagram illustrating the application of predistortion in a base station device. [Figure 3] FIG. 10 is a diagram illustrating the application of post-distortion in a base station device. [Figure 4] FIG. 10 is a diagram illustrating the application of predistortion in a terminal device. [Figure 5]FIG. 10 is a diagram illustrating the application of post-distortion in a terminal device. [Figure 6] 2 is a diagram illustrating an example of the hardware configuration of a base station device, a relay device, and a terminal device. [Figure 7] FIG. 2 is a diagram illustrating an example of a functional configuration of a base station device. [Figure 8] FIG. 2 illustrates an example of a functional configuration of a relay device. [Figure 9] FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal device. [Figure 10] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. [Figure 11] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. [Figure 12] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. [Figure 13] FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention as claimed, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the features described in the embodiments may be combined in any desired manner. Furthermore, the same reference numerals are used to designate identical or similar components, and redundant descriptions will be omitted.

[0011] (System Configuration) Fig. 1 shows an example of the configuration of a wireless communication system according to this embodiment. This wireless communication system is, for example, a cellular communication system including a relay device, and is configured to include a base station device 101, a relay device 102, and a terminal device 103. For simplicity of explanation, Fig. 1 shows a state in which there is one each of base station device 101, relay device 102, and terminal device 103, but naturally, there can be multiple of these devices. Furthermore, the technique described below can also be applied to wireless communication systems other than cellular communication systems.

[0012] In this embodiment, for example, a radio signal transmitted from the base station device 101 is amplified and forwarded by the relay device 102, and then received by the terminal device 103. Furthermore, a radio signal transmitted from the terminal device 103 is amplified and forwarded by the relay device 102, and then received by the base station device 101. The relay device 102 may be, for example, a radio repeater. However, this is just an example, and the relay device 102 may also be a relay device that performs regenerative relaying. The relay device 102 amplifies and forwards the received radio signal near a saturation region where nonlinear distortion may occur. For this reason, the nonlinear distortion is compensated for, for example, by digital post-distortion (DPoD) in the device receiving the radio signal or digital pre-distortion (DPD) in the device transmitting the radio signal. For example, in the downlink, the terminal device 103 receives the radio signal transmitted by the base station device 101 and amplified and forwarded by the relay device 102, and applies DPoD to the radio signal. As a result, the terminal device 103 can demodulate and decode the radio signal while reducing the effects of nonlinear distortion in the base station device 101 and the relay device 102. Similarly, in the uplink, the base station device 101 receives a radio signal transmitted by the terminal device 103 and amplified and forwarded by the relay device 102, and can apply DPoD to the radio signal. Also, in the downlink, the base station device 101 takes into account nonlinear distortion in the base station device 101 and the relay device 102, pre-distorts the signal to be transmitted using DPD so that the amplified signal is distortion-free, and then transmits the signal. Similarly, in the uplink, the terminal device 103 takes into account nonlinear distortion in the relay device 102, pre-distorts the signal to be transmitted using DPD so that the amplified signal is distortion-free, and then transmits the signal. Note that in the terminal device 103, when a signal is amplified near a saturation region where nonlinear distortion may occur, DPoD and DPD can be performed in the uplink, taking into account nonlinear distortion occurring not only in the relay device 102 but also in the terminal device 103.

[0013] For efficient application of DPD or DPoD, it is useful to provide information related to the nonlinear distortion that occurs to a device that performs compensation processing for the linear distortion. That is, when DPD is performed, the information can be provided to a device that transmits a wireless signal, and when DPoD is performed, the information can be provided to a device that receives a wireless signal. This embodiment provides such a method of providing information.

[0014] In this embodiment, the relay device 102 notifies the base station device 101 of information about nonlinear distortion in its power amplifier, regardless of whether DPD or DPoD is used, and regardless of whether the base station device 101 or the terminal device 103 performs nonlinear distortion compensation processing. The base station device 101 then notifies the terminal device 103 of information about nonlinear distortion in the power amplifier of the relay device 102. Note that the base station device 101 may notify the terminal device 103 of information about nonlinear distortion in the power amplifier of the relay device 102 only when the terminal device 103 performs nonlinear distortion compensation processing. In other words, when the terminal device 103 performs DPD in the uplink or DPoD in the downlink, the base station device 101 may notify the terminal device 103 of information about nonlinear distortion in the power amplifier of the relay device 102, which information has been received from the relay device 102.

[0015] The relay device 102 may be configured to communicate with the base station device 101 via the wireless signal that it relays. For example, the relay device 102 may multiplex information that the relay device 102 should notify the base station device 101 with a signal received from the terminal device 103, and forward the multiplexed information to the base station device 101. The relay device 102 may also generate a signal separate from the signal from the terminal device 103 using wireless resources (frequency and time resources) different from those used when receiving a signal from the terminal device 103, and notify the base station device 101 of the information. The relay device 102 may have a function to demodulate and decode some signal components (e.g., control signals) of wireless signals transmitted and received between the base station device 101 and the terminal device 103, and may acquire information from the base station device 101 or the terminal device 103 using the some signal components. The relay device 102 may communicate with the base station device 101 using a wireless communication standard different from the wireless communication standard to which the wireless signal to be relayed conforms. For example, the relay device 102 may be configured to relay a fifth-generation (5G) radio signal between the base station device 101 and the terminal device 103 and to communicate with the base station device 101 using Long Term Evolution (LTE). When using a cellular communication link, the relay device 102 may notify the base station device 101 of information using, for example, a control channel (e.g., a Physical Uplink Control Channel (PUCCH)), Radio Resource Control (RRC) signaling, or the like. The relay device 102 may also notify the base station device 101 of information in a higher layer such as an application layer. A communication link other than the cellular communication link may be used for communication between the base station device 101 and the relay device 102. For example, a fixed wireless access (FWA) or a wireless local area network (wireless LAN) may be used for communication between the base station device 101 and the relay device 102. Alternatively, a wired communication line may be established between the base station device 101 and the relay device 102, and communication between the base station device 101 and the relay device 102 may be performed using the wired communication line.

[0016] The repeater device 102 may notify the base station device 101 of information about the nonlinear distortion in the power amplifier, such as information about a polynomial y=f(x) that takes a signal to be amplified as an argument x and gives an amplified output y. The polynomial information may be in any format that allows the base station device 101 to reproduce the polynomial, such as information indicating the coefficients of the polynomial. The repeater device 102 may also notify the base station device 101 of a trained model that reproduces the characteristics of the power amplifier obtained by, for example, machine learning using the signal to be amplified as input x and the output y observed at that time as training data. Information about the polynomial or trained model that reproduces the characteristics of the power amplifier of the repeater device 102 may be written to a read-only memory (ROM) held by the repeater device 102, for example, during manufacturing or installation. In other words, the repeater device 102 may store information about its own power amplifier in advance. This is just an example, and the repeater device 102 may, for example, have a function internally for identifying the characteristics of the power amplifier. For example, the relay device 102 may have a function for performing machine learning internally using the relationship between the signal to be amplified and the signal output from the power amplifier. In this case, the relay device 102 can perform machine learning internally to obtain a trained model that reproduces the characteristics of the power amplifier. With this configuration, even if the characteristics of the power amplifier change due to changes in the environment in which the relay device 102 is placed or due to aging, the relay device 102 can accurately identify information about the characteristics and notify the base station device 101.

[0017] When the base station device 101 receives the information about the power amplifier of the relay device 102, the base station device 101 can use the information to perform compensation processing for nonlinear distortion in communication with the terminal device 103.

[0018] For example, the base station device 101 can perform DPD in downlink communications. In this case, the base station device 101 distorts the signal waveform in advance, taking into account both the nonlinear distortion caused by its own power amplifier and the nonlinear distortion caused by the power amplifier of the relay device 102, and transmits the distorted signal. FIG. 2 schematically illustrates an example of a signal flow when DPD is performed. First, DPD 202 is applied to a signal 201 to be transmitted, artificially distorting the signal. This distortion has a characteristic that cancels out the nonlinear distortion caused by the first power amplifier 203 of the base station device 101 and the second power amplifier 204 of the relay device 102. The artificially distorted signal is then input to the first power amplifier 203 of the base station device 101 and transmitted, and then becomes a relay signal 205 that is transferred to the terminal device 103 via the second power amplifier 204 of the relay device 102.

[0019] In this case, the DPD 202 is configured so that the waveform of the relay signal 205 after passing through the first power amplifier 203 and the second power amplifier 204 matches the waveform of the transmission target signal 201 (except for its power). To this end, the base station device 101, for example, identifies the relationship between the input x0 to the first power amplifier 203 and the output y0 of the second power amplifier 204 based on information indicating the characteristics of the first power amplifier 203 and the second power amplifier 204. The base station device 101 can then create a trained model of the DPD 202 by machine learning, using x0 as training data related to the output when y0 is input data. That is, the base station device 101 identifies various combinations of the values ​​of x0 and y0 based on the information indicating the characteristics of the first power amplifier 203 and the second power amplifier 204, and performs machine learning so that when the value of y0 in that combination is input to the DPD 202, the x0 corresponding to that y0 is the correct output data. As a result of this machine learning, the base station device 101 acquires a trained model of the DPD 202. After the trained model is acquired, when a transmission target signal is generated, the base station device 101 inputs the signal to the trained model of the DPD 202 to acquire a distorted signal. By the base station device 101 pre-distorting the signal using the DPD 202, it becomes possible for the terminal device 103 to receive a radio signal that is free from nonlinear distortion in the first power amplifier 203 and the second power amplifier 204 (the influence of such distortion can be ignored).

[0020] Furthermore, the base station device 101 may identify a polynomial that indicates the inverse transformation of the nonlinear distortion of the first power amplifier 203 and the second power amplifier 204, for example, without using machine learning. In this case, the DPD 202 can be performed by applying the polynomial to the signal 201 to be transmitted.

[0021] Furthermore, the base station device 101 can perform DPoD in uplink communications. In this case, a transmission signal 301 from the terminal device 103 is received at the base station device 101 via a third power amplifier 302 included in the terminal device 103 and a fourth power amplifier 303 included in the relay device 102. The fourth power amplifier 303 included in the relay device 102 may be the same as or different from the second power amplifier 204 described above. That is, a common power amplifier may be used (for example, in a time-division manner) for uplink and downlink, or separate power amplifiers for downlink and uplink may be provided. Furthermore, the terminal device 103 may operate the third power amplifier 302 in a range where the linearity of the transmission signal can be ensured. In this case, nonlinear distortion does not occur in the terminal device 103, but occurs only in the fourth power amplifier 303 included in the relay device 102. For this reason, when compensating for nonlinear distortion in this case, only the characteristics of the fourth power amplifier 303 can be used. Note that, if nonlinear distortion also occurs in the third power amplifier 302 included in the terminal device 103, the terminal device 103 can notify the base station device 101 of information related to the nonlinear distortion of the third power amplifier 302. This allows the base station device 101 to identify the nonlinear distortion in the third power amplifier 302 and the fourth power amplifier 303, and to appropriately perform DPoD 304 based on the identified nonlinear distortion.

[0022] The DPoD 304 performs nonlinear distortion compensation processing on the received signal and outputs the processed received signal 305. Here, the DPoD 304 is applied so that the waveform of the processed received signal 305 matches the waveform of the transmission signal 301 of the terminal device 103 (excluding its power). For example, the DPoD 304 identifies the relationship between the input signal x1 to the third power amplifier 302 and the output signal y1 of the fourth power amplifier 303, based on information indicating the characteristics of the third power amplifier 302 received from the terminal device 103 and information indicating the characteristics of the fourth power amplifier 303 received from the relay device 102. Then, the base station device 101 can form a trained model of the DPoD 304 by machine learning, using x1 as training data related to the output when the input data is y1. That is, the base station device 101 identifies various combinations of values ​​of x1 and y1 based on information indicating the characteristics of the third power amplifier 302 and the fourth power amplifier 303, and performs machine learning so that when the value of y1 in that combination is input to the DPoD 304, the x1 corresponding to that y1 is the correct data to be output. Alternatively, the base station device 101 may identify a polynomial indicating an inverse transformation that cancels the nonlinear distortion of the third power amplifier 302 and the fourth power amplifier 303, for example, without using machine learning. In this case, the DPoD 304 can be performed by applying the polynomial to the received signal received from the relay device 102 (output from the fourth power amplifier 303).

[0023] The above-described nonlinear distortion compensation process may be performed in the terminal device 103. In this case, the base station device 101 notifies the terminal device 103 of information related to the nonlinear distortion of the power amplifier of the relay device 102 received from the relay device 102. Based on the information, the terminal device 103 can perform DPD or DPoD in the same manner as the process performed by the base station device 101 described above.

[0024] For example, in uplink communications, the terminal device 103 may apply DPD 402 to a transmission target signal 401 to distort the signal, as shown in FIG. 4 . This distortion has characteristics that cancel nonlinear distortion in the third power amplifier 302 of the terminal device 103 and the fourth power amplifier 303 of the relay device 102. Note that when the third power amplifier 302 of the terminal device 103 is used in a region where nonlinear distortion does not occur, the DPD 402 may be configured to cancel only the nonlinear distortion in the fourth power amplifier 303 without taking into account the influence of the third power amplifier 302. The artificially distorted signal is then input to the third power amplifier 302 of the terminal device 103 and transmitted, and then becomes a relay signal 403 that is transferred to the base station device 101 via the fourth power amplifier 303 of the relay device 102.

[0025] In this case, the DPD 402 is configured so that the waveform of the relay signal 403 after passing through the third power amplifier 302 and the fourth power amplifier 303 matches the waveform of the transmission target signal 401 (except for its power). To this end, the terminal device 103, for example, identifies the relationship between the input x2 to the third power amplifier 302 and the output y2 of the fourth power amplifier 303 based on information indicating the characteristics of the third power amplifier 302 and the fourth power amplifier 303, respectively. The terminal device 103 can then form a trained model of the DPD 402 by machine learning in which x2 is used as training data related to the output when y2 is the input data. That is, the terminal device 103 identifies various combinations of the values ​​of x2 and y2 based on the information indicating the characteristics of the third power amplifier 302 and the fourth power amplifier 303, and performs machine learning so that when the value of y2 in that combination is input to the DPD 402, x2 corresponding to that y2 is the correct output data. As a result of this machine learning, the terminal device 103 acquires a trained model of the DPD 402. After the trained model is acquired, when a transmission target signal is generated, the terminal device 103 inputs the signal to the trained model of the DPD 402 to acquire a distorted signal. By the terminal device 103 pre-distorting the signal using the DPD 402, the base station device 101 can receive a radio signal that is free from nonlinear distortion in the third power amplifier 302 and the fourth power amplifier 303 (the influence of such distortion can be ignored).

[0026] Also in this case, polynomials representing the inverse transform of the nonlinear distortion of the third power amplifier 302 and the fourth power amplifier 303 may be identified without using machine learning. In this case, the DPD 402 can be performed by applying the inverse transform to the transmission target signal 401.

[0027] The trained model of DPD 402 and the inverse transform polynomial may be identified not by the terminal device 103 but by another device such as the base station device 101 or a server (not shown) connected to the network. That is, since the base station device 101 receives the nonlinear distortion characteristics of the fourth power amplifier 303 included in the relay device 102, the base station device 101 may identify DPD 402 based on the characteristics. If no nonlinear distortion occurs in the third power amplifier 302 of the terminal device 103, the base station device 101 can identify the trained model of DPD 402 and the inverse transform polynomial based only on information about the nonlinear distortion characteristics of the fourth power amplifier 303. If nonlinear distortion also occurs in the third power amplifier 302 included in the terminal device 103, the terminal device 103 may notify the base station device 101 of information about the nonlinear distortion characteristics of the third power amplifier 302. When the server identifies the DPD 402, the base station device 101 provides the server with the nonlinear distortion characteristics of the third power amplifier 302 included in the terminal device 103 and the nonlinear distortion characteristics of the fourth power amplifier 303 included in the relay device 102. The server then notifies the base station device 101 of the identified DPD 402. The learned model and inverse transform polynomial of the DPD 402 are identified in the same manner as when the terminal device 103 identifies them as described above. The base station device 101 can then notify the terminal device 103 of the identified learned model and inverse transform polynomial of the DPD 402. This allows the terminal device 103 to apply the DPD 402 to a signal to be transmitted by directly using the notified learned model and inverse transform polynomial.

[0028] Furthermore, as shown in FIG. 5 , the terminal device 103 can perform DPoD in downlink communications. In this case, a transmission signal 501 from the base station device 101 is received at the terminal device 103 via a first power amplifier 203 included in the base station device 101 and a second power amplifier 204 included in the relay device 102. The base station device 101 may operate the first power amplifier 203 in a range where the linearity of the transmission signal can be ensured. In this case, nonlinear distortion does not occur in the base station device 101, but occurs only in the second power amplifier 204 included in the relay device 102. Therefore, when compensating for nonlinear distortion, only the characteristics of the second power amplifier 204 can be used. In addition, if nonlinear distortion also occurs in the first power amplifier 203 included in the base station device 101, the base station device 101 can notify the terminal device 103 of information on the nonlinear distortion of the first power amplifier 203 as well as information on the nonlinear distortion of the second power amplifier 204. This allows the terminal device 103 to identify the nonlinear distortion in the first power amplifier 203 and the second power amplifier 204, and to appropriately perform DPoD 502 based on the identified nonlinear distortion.

[0029] The DPoD 502 performs nonlinear distortion compensation processing on the received signal and outputs a processed received signal 503. Here, the DPoD 502 is applied so that the waveform of the processed received signal 503 matches the waveform of the transmission signal 501 of the base station device 101 (excluding its power). For example, the DPoD 502 identifies the relationship between an input signal x3 to the first power amplifier 203 and an output signal y3 of the second power amplifier 204, based on information received from the base station device 101 indicating the characteristics of the first power amplifier 203 of the base station device 101 and information indicating the characteristics of the second power amplifier 204 of the relay device 102. Then, the terminal device 103 can form a trained model of the DPoD 502 by machine learning using x3 as training data related to the output when the input data is y3. That is, the terminal device 103 identifies various combinations of values ​​of x3 and y3 based on information indicating the characteristics of the first power amplifier 203 and the second power amplifier 204, and performs machine learning so that when the value of y3 in that combination is input to DPoD 502, the x3 corresponding to that y3 is the correct data to be output. Furthermore, the terminal device 103 may identify a polynomial indicating an inverse transformation that cancels the nonlinear distortion of the first power amplifier 203 and the second power amplifier 204, for example, without using machine learning. In this case, DPoD 502 can be performed by applying the polynomial to the received signal received from the relay device 102 (output from the second power amplifier 204).

[0030] The trained model and inverse transform polynomial of DPoD502 may be identified not by the terminal device 103 but by another device such as the base station device 101 or a server (not shown) connected to the network. That is, since the base station device 101 receives the nonlinear distortion characteristics of the second power amplifier 204 of the relay device 102, the base station device 101 may identify DPoD502 based on those characteristics. If no nonlinear distortion occurs in the first power amplifier 203 of the base station device 101, the base station device 101 can identify the trained model and inverse transform polynomial of DPoD502 based only on information about the nonlinear distortion characteristics of the second power amplifier 204. On the other hand, even if nonlinear distortion occurs in the first power amplifier 203 of the base station device 101, the base station device 101 knows the characteristics of its own first power amplifier 203 and can therefore identify the trained model of DPoD502 and the inverse transformation polynomial based on the characteristics of the first power amplifier 203 and the characteristics of the second power amplifier 204 without acquiring information from the terminal device 103. When the server identifies DPoD502, the base station device 101 provides the server with the nonlinear distortion characteristics of its own first power amplifier 203 and the nonlinear distortion characteristics of the second power amplifier 204 of the relay device 102. The server then notifies the base station device 101 of the identified DPoD502. The trained model and the inverse transformation polynomial of DPoD502 are identified in the same manner as when the terminal device 103 identifies them as described above. Then, the base station device 101 can notify the identified trained model and inverse transform polynomial of DPoD502 to the terminal device 103. As a result, the terminal device 103 can apply DPoD502 to the received signal by directly using the notified trained model and inverse transform polynomial.

[0031] (Device configuration) Next, the device configuration will be described. Fig. 6 shows an example of the hardware configuration of the base station device 101, relay device 102, and terminal device 103 according to this embodiment. In one example, the base station device 101, relay device 102, and terminal device 103 are configured to include a processor 601, a ROM 602, a RAM 603, a storage device 604, and a communication circuit 605. The processor 601 is a computer configured to include one or more processing circuits, such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and performs overall device processing and each of the above-mentioned processes by reading and executing programs stored in the ROM 602 or the storage device 604. The ROM 602 is a read-only memory that stores information such as programs and various parameters related to the processes executed by the base station device 101, relay device 102, and terminal device 103. The RAM 603 functions as a workspace when the processor 601 executes programs and is a random access memory that stores temporary information. The storage device 604 may be, for example, a removable external storage device. The communication circuit 605 may be, for example, a circuit for LTE or 5G wireless communication. While FIG. 6 illustrates one communication circuit 605, the base station device 101, the relay device 102, and the terminal device 103 may each have multiple communication circuits. For example, the base station device 101 and the terminal device 103 may each have wireless communication circuits for LTE, 5G, and a successor standard, respectively, and a common antenna for these circuits. The relay device 102 has a communication circuit that functions as a wireless repeater. The relay device 102 is configured, for example, to receive a wireless signal transmitted in a predetermined frequency band, amplify the wireless signal, and output the amplified signal (after frequency conversion, if necessary). The base station device 101 may also have a wired communication circuit used when communicating with other base station devices or nodes in the core network. The base station device 101 and the relay device 102 may also include communication circuits for communicating with each other using, for example, LTE or a wired communication line.Furthermore, the terminal device 103 may further include a communication circuit conforming to a wireless communication standard other than the cellular communication standard, such as a wireless local area network (LAN) or Bluetooth (registered trademark).

[0032] FIG. 7 is a diagram illustrating an example of the functional configuration of the base station device 101 according to this embodiment. The base station device 101 includes, as its functional configuration, a characteristic information acquisition unit 701, an information notification unit 702, a transmission control unit 703, and a reception control unit 704. Note that FIG. 7 illustrates only functions particularly related to this embodiment, and does not illustrate various other functions that the base station device 101 may have. For example, the base station device 101 naturally has other functions that are generally possessed by base station devices compliant with 5G and its successor standards. The functional blocks in FIG. 7 are illustrated schematically, and the respective functional blocks may be integrated or further subdivided. Each function in FIG. 7 may be realized, for example, by the processor 301 executing a program stored in the ROM 302 or the storage device 304, or by a processor within the communication circuit 305 executing predetermined software. The details of the processing performed by each functional unit will not be described here, and only the general functions will be outlined.

[0033] The characteristic information acquisition unit 701 acquires, from the relay device 102, characteristic information of the power amplifier used in the relay device 102. This information of the power amplifier characteristic is, for example, information capable of identifying nonlinear distortion in the saturation region. Note that this information has the form of, for example, a polynomial or a trained model that can obtain a corresponding output when an input is given to the power amplifier. This polynomial or trained model is assumed to be specified and stored in the relay device 102 in advance (at the time of manufacture or shipment). Note that the trained model can be acquired, for example, by measuring output signals when input signals are given in multiple patterns using an indoor experiment system or the like for the power amplifier used in the relay device 102, and using the input signals as inputs to the trained model and the corresponding output signals as training data. Furthermore, the characteristic information acquisition unit 701 acquires, from the terminal device 103, characteristic information of the power amplifier used in the terminal device 103, for example, when DPoD is applied in uplink communications. Note that, when the terminal device 103 uses a power amplifier in a region where nonlinear distortion does not occur, the characteristic information acquisition unit 701 does not need to acquire information about the power amplifier even when DPoD is applied. Note that the base station device 101 is capable of identifying whether the terminal device 103 is connected to the base station device 101 via the relay device 102. For example, when relaying a wireless signal, the relay device 102 transfers the wireless signal in a predetermined frequency band for relay transmission, or adds additional information such as a predetermined header to the wireless signal, so that the base station device 101 or the terminal device 103 that receives the signal can recognize that communication is being performed via the relay device 102.

[0034] When the terminal device 103 applies DPD or DPoD, the information notifying unit 702 notifies the terminal device 103 of information on the characteristics of the power amplifier used in the relay device 102, which information is acquired from the relay device 102 by the characteristic information acquiring unit 701. Furthermore, when nonlinear distortion occurs due to the power amplifier applied to a transmission signal in the base station device 101, the base station device 101 can notify the terminal device 103 of information on the characteristics of the power amplifier of the base station device 101. Note that when the base station device 101 uses a power amplifier in a range where nonlinear distortion does not occur, the characteristics of the power amplifier of the base station device 101 do not need to be notified to the terminal device 103.

[0035] Furthermore, when a learned model or polynomial of DPD or DPoD to be applied by the terminal device 103 is identified by, for example, a server within the base station device 101 or connected to another network, the information notifying unit 702 may notify the terminal device 103 of the learned model or polynomial (i.e., information indicating the characteristics of DPD or DPoD). When DPD is applied in the terminal device 103, information on the power amplifier of the relay device 102 and information on the power amplifier of the terminal device 103 are used to identify the learned model or polynomial of DPD. When the terminal device 103 uses a power amplifier in a region where nonlinear distortion does not occur, only information on the power amplifier of the relay device 102 may be used. When DPoD is applied in the terminal device 103, information on the power amplifier of the base station device 101 and information on the power amplifier of the relay device 102 are used to identify the learned model or polynomial of DPoD. When the base station device 101 uses a power amplifier in a region where nonlinear distortion does not occur, only the information of the power amplifier of the relay device 102 may be used. When a server different from the base station device 101 identifies a trained model or polynomial for DPD or DPoD, the information notification unit 702 notifies the server of that information. Thereafter, the information notification unit 702 receives the trained model or polynomial for DPD or DPoD from the server, and notifies the terminal device 103 of the information on the trained model or polynomial.

[0036] The transmission control unit 703 controls the transmission of signals to the terminal device 103. For example, when DPD is used in the base station device 101, the transmission control unit 703 identifies a DPD trained model or polynomial to be applied to a signal to be transmitted, based at least on information about the power amplifier of the relay device 102. Note that when the power amplifier of the base station device 101 operates near the saturation region, the transmission control unit 703 may also consider information about the power amplifier of the base station device 101 to identify a DPD trained model or polynomial to be applied to a signal to be transmitted. The transmission control unit 703 inputs the signal to be transmitted to the identified trained model or applies the identified polynomial to the signal to be transmitted, thereby artificially distorting the signal to be transmitted. The transmission control unit 703 then amplifies the artificially distorted signal using a power amplifier and transmits it via an antenna. The artificially distorted waveform of the signal is cancelled out by the nonlinear distortion of the power amplifier of the relay device 102, and the signal is received by the terminal device 103 as a signal that is not affected by the nonlinear distortion of the power amplifier. Note that, for example, when DPoD is applied to the terminal device 103, the transmission control unit 703 can transmit the radio signal without applying DPD.

[0037] The reception control unit 704 controls reception of a signal from the terminal device 103 (via the relay device 102). For example, when DPoD is used in the base station device 101, the reception control unit 704 identifies a trained model or polynomial of DPoD to be applied to the received signal based at least on information about the power amplifier of the relay device 102. Note that when the power amplifier of the terminal device 103 operates near the saturation region, the reception control unit 704 may also consider information about the power amplifier of the terminal device 103 to identify a trained model or polynomial of DPoD to be applied to the received signal. The reception control unit 704 inputs the received signal to the trained model or applies the polynomial to the received signal, and obtains a processed received signal. The processed received signal is a signal that is not affected by the nonlinear distortion of the power amplifier, as the nonlinear distortion of the power amplifier of the terminal device 103 and the power amplifier of the relay device 102 is canceled by DPoD. The reception control unit 704 then performs, for example, channel estimation, demodulation, and decoding on the processed received signal. Note that, for example, when DPD is applied in the terminal device 103, the reception control unit 704 does not apply DPoD to the received signal.

[0038] FIG. 8 is a diagram illustrating an example of the functional configuration of the relay device 102 according to this embodiment. The relay device 102 includes, for example, a characteristic information notification unit 801 and a transfer control unit 802 as its functional configuration. Note that FIG. 8 illustrates only functions particularly related to this embodiment, and does not illustrate various other functions that the relay device 102 may have. The functional blocks in FIG. 8 are illustrated schematically, and the functional blocks may be integrated or further subdivided. Each function in FIG. 8 may be implemented, for example, by the processor 301 executing a program stored in the ROM 302 or the storage device 304, or by a processor within the communication circuit 305 executing predetermined software. Details of the processes performed by each functional unit will not be described here, and only their general functions will be outlined.

[0039] The characteristic information notifying unit 801 notifies the base station device 101 of information on the characteristics of the power amplifier used in the relay device 102. That is, the information acquired in the characteristic information acquiring unit 701 of the base station device 101 is notified by the characteristic information notifying unit 801. The notified information is as described above, and will not be repeated here. The transfer control unit 802 transfers radio signals. For example, when the transfer control unit 802 receives a radio signal transmitted from the base station device 101, the transfer control unit 802 amplifies the signal using the second power amplifier 204 and transmits the amplified signal toward the terminal device 103. Furthermore, when the transfer control unit 802 receives a radio signal transmitted from the terminal device 103, the transfer control unit 802 amplifies the signal using the fourth power amplifier 303 and transmits the amplified signal toward the base station device 101.

[0040] FIG. 9 is a diagram illustrating an example of the functional configuration of the terminal device 103 according to this embodiment. The terminal device 103 includes, for example, an information acquisition unit 901, a transmission control unit 902, and a reception control unit 903 as its functional configuration. Note that FIG. 9 illustrates only functions particularly related to this embodiment, and does not illustrate various other functions that the terminal device 103 may have. For example, the terminal device 103 naturally has other functions that terminal devices compliant with 5G or its successor standards generally have. The functional blocks in FIG. 9 are illustrated schematically, and the respective functional blocks may be integrated or further subdivided. Each function in FIG. 9 may be realized, for example, by the processor 301 executing a program stored in the ROM 302 or the storage device 304, or by a processor within the communication circuit 305 executing predetermined software. The details of the processes performed by each functional unit will not be described here, and only their general functions will be outlined.

[0041] When the terminal device 103 uses DPD or DPoD, the information acquisition unit 901 acquires information for the DPD or DPoD from the base station device 101. The information acquisition unit 901 acquires, for example, information about the power amplifier of the relay device 102. The information acquisition unit 901 may also acquire information about the power amplifier of the base station device 101. Note that when the base station device 101 or a server connected to the network identifies a trained model or polynomial for DPD or DPoD, the information acquisition unit 901 may acquire information about the trained model or polynomial (i.e., information indicating the characteristics of DPD or DPoD) from the base station device 101.

[0042] The transmission control unit 902 controls the transmission of signals to the base station device 101. For example, when DPD is used in the terminal device 103, the transmission control unit 902 identifies a DPD trained model or polynomial to be applied to a signal to be transmitted, based at least on information about the power amplifier of the relay device 102. Note that when the power amplifier of the terminal device 103 operates near the saturation region, the transmission control unit 902 may identify a DPD trained model or polynomial to be applied to a signal to be transmitted, taking into account information about the power amplifier of the terminal device 103. Note that when the transmission control unit 902 receives information about a DPD trained model or polynomial from the base station device 101, the transmission control unit 902 can use the trained model or polynomial as is. The transmission control unit 902 inputs the signal to be transmitted to a trained model or applies a polynomial to the signal to be transmitted, thereby artificially distorting the signal to be transmitted. The transmission control unit 902 then amplifies the artificially distorted signal using a power amplifier and transmits it via an antenna. The artificially distorted waveform of the signal is cancelled out by the nonlinear distortion of the power amplifier of the terminal device 103 and the power amplifier of the relay device 102, and the signal is received by the base station device 101 as a signal that is not affected by the nonlinear distortion of the power amplifier. Note that, for example, when DPoD is applied in the base station device 101, the transmission control unit 902 can transmit the radio signal without applying DPD.

[0043] The reception control unit 903 controls reception of a signal from the base station device 101 (via the relay device 102). For example, when DPoD is used in the terminal device 103, the reception control unit 903 identifies a trained model or polynomial of DPoD to be applied to the received signal based at least on information about the power amplifier of the relay device 102. Note that when the power amplifier of the base station device 101 operates near the saturation region, the reception control unit 903 may also consider information about the power amplifier of the base station device 101 to identify a trained model or polynomial of DPoD to be applied to the received signal. The reception control unit 903 inputs the received signal to the trained model or applies the polynomial to the received signal, and obtains a processed received signal. The nonlinear distortion of the power amplifier of the base station device 101 and the power amplifier of the relay device 102 is canceled by DPoD, resulting in a signal that is not affected by the nonlinear distortion of the power amplifier. The reception control unit 903 then performs, for example, channel estimation, demodulation, and decoding on the processed received signal. Note that, for example, when DPD is applied in the base station device 101, the reception control unit 903 does not apply DPoD to the received signal.

[0044] (Processing flow) Next, an example of the flow of processing executed in a wireless communication system will be described. FIG. 10 shows an example of the flow of processing when DPD is applied to a transmission signal in a base station device 101. In this processing example, the relay device 102 notifies the base station device 101 of the nonlinear distortion characteristics of its own power amplifier (S1001). The base station device 101 performs machine learning based on the notified information about the power amplifier of the relay device 102 (S1002) to acquire a trained DPD model. Here, if it is expected that nonlinear distortion will occur due to operating the power amplifier of the base station device 101 near the saturation region, the base station device 101 performs machine learning taking into account the characteristics of the power amplifier of the own device. Note that, although an example in which machine learning is performed will be described here, a polynomial indicating an inverse transformation of a transfer function of nonlinear distortion may also be specified. Thereafter, when data to be transmitted is generated (S1003), the base station device 101 performs modulation and the like based on the data to be transmitted to generate a signal to be transmitted. The base station device 101 inputs the transmission target signal into the trained model acquired in S1002 and applies DPD to the transmission target signal (S1004). The base station device 101 then amplifies the signal after DPD application (S1005) and outputs it as a wireless signal (S1006). Upon receiving the wireless signal, the relay device 102 amplifies the wireless signal (S1007) and forwards it. The terminal device 103 receives the forwarded wireless signal (S1008).

[0045] This allows the terminal device 103 to receive a radio signal that is not affected by nonlinear distortion that may occur in S1005 and S1007.

[0046] Next, an example of a processing flow when DPoD is applied to a received signal in the base station device 101 will be described with reference to FIG. 11. In this processing example, the relay device 102 notifies the base station device 101 of the nonlinear distortion characteristics of its own power amplifier (S1101). Furthermore, if it is expected that nonlinear distortion will occur due to the operation of its own power amplifier near the saturation region, the terminal device 103 may notify the base station device 101 of the nonlinear distortion characteristics of its own power amplifier (S1102). Then, the base station device 101 performs machine learning based on the notified information about the power amplifier of the relay device 102 (and information about the power amplifier of the terminal device 103, if present) (S1103) to acquire a trained model for DPoD. Note that, although an example in which machine learning is performed will be described here, a polynomial indicating the inverse transformation of the transfer function of the nonlinear distortion may also be specified. Thereafter, when data to be transmitted is generated (S1104), the terminal device 103 performs modulation or the like based on the data to be transmitted, generates a signal to be transmitted, amplifies the generated signal (S1105), and outputs it as a wireless signal (S1106). When the relay device 102 receives the wireless signal, it amplifies the wireless signal (S1107) and forwards it. When the base station device 101 receives the wireless signal (S1108), it inputs the wireless signal into the trained model acquired in S1003 and applies DPoD to the received wireless signal (S1109).

[0047] This makes it possible for the base station device 101 to acquire a signal from the received signal in which the influence of nonlinear distortion that may occur in S1105 and S1107 has been cancelled.

[0048] Next, an example of a processing flow when DPD is applied to a transmission signal in the terminal device 101 will be described with reference to FIG. 12. In this processing example, the relay device 102 notifies the base station device 101 of the nonlinear distortion characteristics of its own power amplifier (S1201). The base station device 101 notifies the terminal device 103 of the nonlinear distortion characteristics of the power amplifier of the relay device 102 (S1202). The terminal device 103 performs machine learning based on the notified information about the power amplifier of the relay device 102 (S1002) to acquire a trained DPD model. Note that, for example, when it is expected that nonlinear distortion will occur due to operating the power amplifier of the terminal device 103 near the saturation region, the terminal device 103 may perform machine learning taking into account the nonlinear distortion characteristics of the power amplifier of the terminal device. Note that, although an example in which machine learning is performed will be described here, a polynomial indicating an inverse transformation of the transfer function of the nonlinear distortion may also be identified. Thereafter, when data to be transmitted is generated (S1204), the terminal device 103 performs modulation and the like based on the data to be transmitted to generate a signal to be transmitted. The terminal device 103 inputs the transmission target signal into the trained model acquired in S1203 and applies DPD to the transmission target signal (S1205). Then, the terminal device 103 amplifies the signal after DPD application (S1206) and outputs it as a wireless signal (S1207). Upon receiving the wireless signal, the relay device 102 amplifies the wireless signal (S1208) and forwards it. The base station device 101 receives the forwarded wireless signal (S1209).

[0049] This allows the base station device 101 to receive a radio signal that is not affected by nonlinear distortion that may occur in S1206 and S1208.

[0050] Next, an example of a processing flow when DPoD is applied to a received signal in the terminal device 101 will be described with reference to FIG. 13. In this processing example, the relay device 102 notifies the base station device 101 of the nonlinear distortion characteristics of its own power amplifier (S1301). The base station device 101 notifies the terminal device 103 of the nonlinear distortion characteristics of its own power amplifier (S1302). Note that, for example, if it is expected that nonlinear distortion will occur due to the base station device 101 operating its own power amplifier near a saturation region, the base station device 101 may also notify the terminal device 103 of the nonlinear distortion characteristics of its own power amplifier. Then, the terminal device 103 performs machine learning based on the notified information about the power amplifier of the relay device 102 (and information about the power amplifier of the base station device 101, if present) (S1303) to acquire a trained model for DPoD. Note that, although an example in which machine learning is performed will be described here, a polynomial indicating the inverse transformation of the transfer function of the nonlinear distortion may also be specified. Thereafter, when data to be transmitted is generated (S1304), the base station device 101 performs modulation and the like based on the data to be transmitted, generates a signal to be transmitted, amplifies the generated signal (S1305), and outputs it as a wireless signal (S1306). When the relay device 102 receives the wireless signal, it amplifies the wireless signal (S1307) and forwards it. When the terminal device 103 receives the wireless signal (S1308), it inputs the wireless signal into the trained model acquired in S1303 and applies DPoD to the received wireless signal (S1309).

[0051] This makes it possible for the terminal device 103 to acquire a signal from the received signal in which the influence of nonlinear distortion that may occur in S1305 and S1307 has been cancelled.

[0052] In this way, by making it possible to compensate for nonlinear distortion in the power amplifiers in repeater equipment, it is possible to tolerate the occurrence of that nonlinear distortion and improve the power efficiency of the entire system. This will contribute to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "Build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0053] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention.

Claims

1. A base station device, an acquisition means for acquiring, from a relay device that relays communication between the base station device and a terminal device, first information that can identify nonlinear distortion caused by a power amplifier included in the relay device; a notification means for notifying the terminal device of second information used when the terminal device compensates for nonlinear distortion caused by the power amplifier of the relay device; A base station device comprising:

2. 2. The base station device according to claim 1, wherein the second information is the first information.

3. 3. The base station apparatus according to claim 2, wherein the second information further includes third information capable of identifying nonlinear distortion caused by a power amplifier included in the base station apparatus.

4. 2. The base station device according to claim 1, wherein the second information is information indicating characteristics of predistortion, which is specified based on the first information and which predistorts a signal to be transmitted in order to compensate for nonlinear distortion caused by a power amplifier included in the relay device.

5. The acquisition means further acquires, from the terminal device, fourth information capable of identifying nonlinear distortion caused by a power amplifier included in the terminal device; 2. The base station device according to claim 1, wherein the second information is information indicating characteristics of predistortion that pre-distorts a signal to be transmitted in order to compensate for nonlinear distortion caused by a power amplifier included in the terminal device and a power amplifier included in the relay device, the predistortion characteristics being specified based on the first information and the fourth information.

6. 2. The base station device according to claim 1, wherein the second information is information indicating post-distortion characteristics, which are specified based on the first information, and which cancel nonlinear distortion caused by a power amplifier included in the relay device from a received signal transmitted from the base station device and received via the relay device.

7. The base station device according to claim 1, characterized in that the second information is information indicating post-distortion characteristics that cancel nonlinear distortion caused by a power amplifier possessed by the base station device and nonlinear distortion caused by a power amplifier possessed by the relay device from a received signal transmitted from the base station device and received via the relay device, the post-distortion characteristics being identified based on the first information and third information that can identify nonlinear distortion caused by a power amplifier possessed by the base station device.

8. A terminal device, a receiving means for receiving, from the base station device, second information used when compensating for nonlinear distortion caused by a power amplifier of the relay device, the second information being based on first information capable of identifying nonlinear distortion caused by a power amplifier of the relay device that relays communication between the base station device and the terminal device; a processing means for performing compensation processing for nonlinear distortion caused by a power amplifier of the relay device in communication with the base station device via the relay device based on the second information; A terminal device comprising:

9. the second information is the first information, The terminal device according to claim 8, further comprising a determination means for determining, based on the first information, predistortion characteristics for a signal to be transmitted to the base station device or postdistortion characteristics for a signal received from the base station device.

10. The terminal device according to claim 8, characterized in that the second information is information indicating pre-distortion characteristics for a signal to be transmitted to the base station device or post-distortion characteristics for a signal received from the base station device based on the first information.

11. A control method executed by a base station device, acquiring, from a relay device that relays communication between the base station device and a terminal device, first information that can identify nonlinear distortion caused by a power amplifier included in the relay device; notifying the terminal device of second information used when the terminal device compensates for nonlinear distortion caused by the power amplifier of the relay device; A control method comprising:

12. A control method executed by a terminal device, comprising: receiving, from the base station device, second information to be used when compensating for nonlinear distortion caused by a power amplifier of the relay device, the second information being based on first information capable of identifying nonlinear distortion caused by a power amplifier of the relay device that relays communication between the base station device and the terminal device; performing compensation processing for nonlinear distortion caused by a power amplifier of the relay device in communication with the base station device via the relay device based on the second information; A control method comprising:

13. A program for causing a computer to function as each of the means included in the base station device according to any one of claims 1 to 7.

14. A program for causing a computer to function as each of the means included in the terminal device according to any one of claims 8 to 10.

Images