JP7761603B2 - Base station device, terminal device, control method, and program that enable efficient compensation of nonlinear distortion in relay device - Google Patents

Description

The present invention relates to a technique for compensating for nonlinear distortion in relay devices.

In wireless communications, a device transmitting a signal uses a power amplifier to amplify and output the power of the signal to be transmitted. This power amplifier is typically used in an operating region where nonlinear distortion does not occur in the signal waveform. However, this operating region where nonlinear distortion does not occur is not necessarily power efficient. In response to this, techniques that modify 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. Examples of such techniques include digital pre-distortion (DPD) in the transmitting device and digital post-distortion (DPoD) in the receiving device. Non-Patent Document 1 describes how the UE provides information to the base station device to use DPD, and how it transmits reference signals and other signals to cause the terminal device to use DPoD.

3GPP (registered trademark) Contribution, R1-2213007

Relay devices such as wireless repeaters can be used to extend the communication distance in wireless communications. To improve power efficiency in 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 can occur. In this case, compensation for nonlinear distortion caused by DPD or DPoD can be performed while taking into account the nonlinear distortion in the relay device.

The present invention provides technology that enables efficient compensation of nonlinear distortion in relay devices.

A base station device according to one aspect of the present invention includes an acquisition means for acquiring, from the relay device, first information capable of identifying nonlinear distortion caused by a power amplifier included in a 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 nonlinear distortion caused by the power amplifier of the relay device.

A terminal device according to one aspect of the present invention comprises: receiving means for receiving, from the base station device, second information used when compensating for nonlinear distortion caused by the power amplifier of the relay device, based on first information that can identify nonlinear distortion caused by the power amplifier of the relay device that relays communications between the base station device and the terminal device; and processing means for performing compensation processing for nonlinear distortion caused by the power amplifier of the relay device in communications with the base station device via the relay device, based on the second information.

This invention makes it possible to efficiently compensate for nonlinear distortion in relay devices.

FIG. 1 is a diagram illustrating an example of the configuration of a wireless communication system. FIG. 10 is a diagram illustrating the application of predistortion in a base station device. FIG. 10 is a diagram illustrating the application of post-distortion in a base station device. FIG. 10 is a diagram illustrating the application of predistortion in a terminal device. FIG. 10 is a diagram illustrating the application of post-distortion in a terminal device. 2 is a diagram illustrating an example of the hardware configuration of a base station device, a relay device, and a terminal device. FIG. 2 is a diagram illustrating an example of a functional configuration of a base station device. FIG. 2 illustrates an example of a functional configuration of a relay device. FIG. 2 is a diagram illustrating an example of a functional configuration of a terminal device. FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system. FIG. 1 is a diagram illustrating an example of a flow of processing executed in a wireless communication system.

The following embodiments are described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the claimed invention, and not all combinations of features described in the embodiments are necessarily essential to the invention. Two or more of the multiple features described in the embodiments may be combined in any desired manner. Furthermore, the same reference numbers are used for identical or similar components, and duplicate descriptions will be omitted.

(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. Note that for simplicity of explanation, Fig. 1 shows a state in which there is one base station device 101, one relay device 102, and one 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.

In this embodiment, for example, a radio signal transmitted from base station device 101 is amplified and forwarded by relay device 102, and then received by terminal device 103. Furthermore, a radio signal transmitted from terminal device 103 is amplified and forwarded by relay device 102, and then received by base station device 101. Note that relay device 102 may be, for example, a wireless repeater. However, this is just one example, and relay device 102 may also be a relay device that performs regenerative relaying. Relay device 102 amplifies and forwards the received radio signal near the saturation region where nonlinear distortion may occur. Therefore, for example, the nonlinear distortion is compensated for 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, terminal device 103 receives the radio signal transmitted by base station device 101 and amplified and forwarded by relay device 102, and applies DPoD to the radio signal. This allows the terminal device 103 to demodulate and decode the radio signal while reducing the effects of nonlinear distortion in the base station device 101 and 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. Furthermore, in the downlink, the base station device 101 takes into account nonlinear distortion in the base station device 101 and relay device 102 and pre-distorts the signal to be transmitted using DPD so that the amplified signal is distortion-free before transmitting the signal. Similarly, in the uplink, the terminal device 103 takes into account nonlinear distortion in the relay device 102 and pre-distorts the signal to be transmitted using DPD so that the amplified signal is distortion-free before transmitting the signal. Note that, in the terminal device 103, when a signal is amplified near the 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.

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

In this embodiment, the relay device 102 notifies the base station device 101 of information about nonlinear distortion in its own 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 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 on the uplink or DPoD on 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 that it received from the relay device 102.

The relay device 102 may be configured to communicate with the base station device 101 via the wireless signal it relays. For example, the relay device 102 may multiplex information that it should notify the base station device 101 onto 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 to receive the signal from the terminal device 103, and notify the information to the base station device 101. The relay device 102 may also have the function of demodulating and decoding some signal components (e.g., control signals) of the wireless signal transmitted and received between the base station device 101 and the terminal device 103, and may obtain information from the base station device 101 or the terminal device 103 using these signal components. The relay device 102 may also 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 fifth-generation (5G) radio signals 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. Alternatively, the relay device 102 may notify the base station device 101 of information in a higher layer, such as an application layer. Alternatively, 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 carried out using the wired communication line.

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 the polynomial y = f(x), which takes the signal to be amplified as argument x and gives the 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 polynomial's coefficients. 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, for example, by 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 one example; for example, the repeater device 102 may 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, information about those characteristics can be identified with high accuracy and notified to the base station device 101.

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

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, before transmitting the signal. Figure 2 schematically illustrates an example of the signal flow when DPD is performed. First, DPD 202 is applied to a signal to be transmitted 201, artificially distorting the signal. This distortion has characteristics that cancel out the nonlinear distortion caused by the first power amplifier 203 in the base station device 101 and the second power amplifier 204 in the relay device 102. The artificially distorted signal is then input to the first power amplifier 203 in the base station device 101 and transmitted. It then becomes a relay signal 205, which is forwarded to the terminal device 103 via the second power amplifier 204 in the relay device 102.

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 achieve this, the base station device 101, for example, determines 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, respectively. The base station device 101 can then create a trained model of the DPD 202 through machine learning, using x0 as training data related to the output when y0 is the input data. That is, the base station device 101 determines 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 each 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 for the DPD 202. After the trained model is acquired, when a signal to be transmitted is generated, the base station device 101 inputs the signal into the trained model for the DPD 202 to acquire a distorted signal. By the base station device 101 pre-distorting the signal using the DPD 202, the terminal device 103 can receive a radio signal that is free of nonlinear distortion in the first power amplifier 203 and the second power amplifier 204 (the effects of such distortion can be ignored).

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 transmission target signal 201.

The base station device 101 can also perform DPoD in uplink communications. In this case, the transmission signal 301 from the terminal device 103 is received at the base station device 101 via the third power amplifier 302 of the terminal device 103 and the fourth power amplifier 303 of the relay device 102. The fourth power amplifier 303 of 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 (e.g., time-shared) for the uplink and downlink, or separate power amplifiers may be provided for the downlink and uplink. The terminal device 103 may also operate the third power amplifier 302 in a range that ensures the linearity of the transmission signal. In this case, nonlinear distortion does not occur in the terminal device 103, but occurs only in the fourth power amplifier 303 of the relay device 102. Therefore, 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 regarding 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 appropriately execute DPoD 304 based on that information.

DPoD304 performs nonlinear distortion compensation processing on the received signal and outputs the processed received signal 305. Here, DPoD304 is applied so that the waveform of the processed received signal 305 matches the waveform of the transmission signal 301 from the terminal device 103 (excluding its power). For example, DPoD304 determines 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 DPoD304 by machine learning, using x1 as training data related to the output when y1 is input data. That is, the base station device 101 identifies various combinations of the 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 output data. 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 that polynomial to the received signal received from the relay device 102 (output from the fourth power amplifier 303).

The above-mentioned nonlinear distortion compensation process may be performed by 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 this information, the terminal device 103 can perform DPD or DPoD in a manner similar to the process performed by the base station device 101 described above.

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 range 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 forwarded to the base station device 101 via the fourth power amplifier 303 of the relay device 102.

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, determines 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 create a trained model of the DPD 402 through machine learning, using x2 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, the 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 into 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 of nonlinear distortion in the third power amplifier 302 and the fourth power amplifier 303 (the effects of such distortion can be ignored).

Also in this case, a polynomial representing the inverse transformation 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 transformation to the transmission target signal 401.

The learned model and inverse transform polynomial of DPD 402 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 of the relay device 102, it may identify DPD 402 based on those characteristics. Note that if no nonlinear distortion occurs in the third power amplifier 302 of the terminal device 103, the base station device 101 can identify the learned model and inverse transform polynomial of DPD 402 based solely on information about the nonlinear distortion characteristics of the fourth power amplifier 303. Note that if nonlinear distortion also occurs in the third power amplifier 302 of 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 in the terminal device 103 and the nonlinear distortion characteristics of the fourth power amplifier 303 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 the signal to be transmitted by directly using the notified learned model and inverse transform polynomial.

Furthermore, as shown in FIG. 5, the terminal device 103 can perform DPoD in downlink communications. In this case, the transmission signal 501 from the base station device 101 is received at the terminal device 103 via the first power amplifier 203 of the base station device 101 and the second power amplifier 204 of the relay device 102. Note that 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 of the relay device 102. Therefore, when compensating for nonlinear distortion, only the characteristics of the second power amplifier 204 can be used. Note that if nonlinear distortion also occurs in the first power amplifier 203 of the base station device 101, the base station device 101 may notify the terminal device 103 of not only information about the nonlinear distortion of the second power amplifier 204 but also information about the nonlinear distortion of the first power amplifier 203. This allows the terminal device 103 to identify nonlinear distortion in the first power amplifier 203 and the second power amplifier 204 and appropriately perform DPoD502 based on that information.

DPoD502 performs nonlinear distortion compensation processing on the received signal and outputs the processed received signal 503. Here, DPoD502 is applied so that the waveform of the processed received signal 503 matches the waveform of the transmission signal 501 from the base station device 101 (excluding its power). For example, DPoD502 determines the relationship between the input signal x3 to the first power amplifier 203 and the 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 possessed by the base station device 101 and information indicating the characteristics of the second power amplifier 204 possessed by the relay device 102. Then, the terminal device 103 can form a trained model of DPoD502 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 the 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 the DPoD 502, the x3 corresponding to that y3 is the correct output data. Alternatively, 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, the DPoD 502 can be performed by applying that polynomial to the received signal received from the relay device 102 (output from the second power amplifier 204).

The learned model and inverse transformation 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, it may identify DPoD502 based on those characteristics. Note that 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 learned model and inverse transformation polynomial of DPoD502 based solely 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 learned model and inverse transform polynomial of the DPoD 502 based on that characteristic and the characteristics of the second power amplifier 204 without acquiring information from the terminal device 103. When the server identifies the DPoD 502, 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 DPoD 502. The learned model and inverse transform polynomial of the DPoD 502 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 DPoD502 trained model and inverse transform polynomial. This allows the terminal device 103 to apply DPoD502 to the received signal using the notified trained model and inverse transform polynomial as is.

(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-described 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, as well as 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 wireless signals transmitted in a predetermined frequency band, amplify the wireless signals, and output the amplified signals (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 a communication circuit for communicating with each other using, for example, LTE or a wired communication line. The terminal device 103 may also have a communication circuit that complies with a wireless communication standard other than the cellular communication standard, such as a wireless local area network (LAN) or Bluetooth (registered trademark).

Figure 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, for example, a characteristic information acquisition unit 701, an information notification unit 702, a transmission control unit 703, and a reception control unit 704. Note that Figure 7 only illustrates functions specifically 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 Figure 7 are illustrated schematically, and the functional blocks may be integrated or further subdivided. Each function in Figure 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; only their general functions will be outlined.

The characteristic information acquisition unit 701 acquires, from the relay device 102, information on the characteristics of the power amplifier used in the relay device 102. This power amplifier characteristic information 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 obtains a corresponding output when an input is given to the power amplifier. This polynomial or trained model is assumed to be identified 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 the output signals of the power amplifier used in the relay device 102 when input signals are given in multiple patterns using an indoor experiment system, and then using the input signals as input 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, information on the characteristics of the power amplifier used in the terminal device 103, for example, when DPoD is applied in uplink communications. Note that, if the terminal device 103 uses a power amplifier in a range where nonlinear distortion does not occur, the characteristic information acquisition unit 701 does not need to acquire information about that 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 can transfer the wireless signal in a specified frequency band for relay transmission, or add additional information such as a specified header to the wireless signal, thereby enabling the base station device 101 or terminal device 103 receiving the signal to recognize that communication is taking place via the relay device 102.

When the terminal device 103 applies DPD or DPoD, the information notification unit 702 notifies the terminal device 103 of information on the characteristics of the power amplifier used in the relay device 102, acquired from the relay device 102 by the characteristics information acquisition unit 701. The base station device 101 can also notify the terminal device 103 of information on the characteristics of its own power amplifier when nonlinear distortion occurs due to the power amplifier applied to the transmission signal in 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.

Furthermore, when a learned model or polynomial for DPD or DPoD to be applied by the terminal device 103 is identified, for example, by a server within the base station device 101 or connected to another network, the information notification 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 for DPD. When the terminal device 103 uses a power amplifier in a range 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 for DPoD. Note that when the base station device 101 uses a power amplifier in a region where nonlinear distortion does not occur, only the information about the power amplifier of the relay device 102 may be used. Note that when a server other than the base station device 101 identifies a trained model or polynomial for DPD or DPoD, the information notification unit 702 notifies that server of that information. The information notification unit 702 then receives the trained model or polynomial for DPD or DPoD from the server, and notifies the terminal device 103 of the information about the trained model or polynomial.

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 the DPD trained model and polynomial to be applied to the 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 the DPD trained model and polynomial to be applied to the signal to be transmitted. The transmission control unit 703 inputs the signal to be transmitted into 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 this signal is canceled 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.

The reception control unit 704 controls the reception of signals 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 DPoD trained model or polynomial 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 DPoD trained model or polynomial to be applied to the received signal. The reception control unit 704 inputs the received signal into the trained model or applies the polynomial to the received signal, and obtains a processed received signal. The processed received signal has the nonlinear distortion of the power amplifier of the terminal device 103 and the power amplifier of the relay device 102 canceled out by DPoD, resulting in a signal that is not affected by the nonlinear distortion of the power amplifier. The reception control unit 704 then performs, for example, channel estimation, demodulation, and decoding on the processed received signal. Note that, for example, if DPD is applied to the terminal device 103, the reception control unit 704 does not apply DPoD to the received signal.

Figure 8 is a diagram showing an example of the functional configuration of the relay device 102 of 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 Figure 8 only shows functions particularly related to this embodiment, and does not show various other functions that the relay device 102 may have. The functional blocks in Figure 8 are shown schematically, and the functional blocks may be integrated or further subdivided. Each function in Figure 8 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. Details of the processing performed by each functional unit will not be described here, and only a general overview of their functions will be provided.

The characteristic information notification 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 by the characteristic information acquisition unit 701 of the base station device 101 is notified by the characteristic information notification unit 801. The notified information is as described above, so it will not be repeated here. The transfer control unit 802 transfers wireless signals. For example, when the transfer control unit 802 receives a wireless signal transmitted from the base station device 101, it 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 wireless signal transmitted from the terminal device 103, it amplifies the signal using the fourth power amplifier 303 and transmits the amplified signal toward the base station device 101.

Figure 9 is a diagram showing an example of the functional configuration of the terminal device 103 of 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 Figure 9 only shows 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. Furthermore, the functional blocks in Figure 9 are shown schematically, and the respective functional blocks may be integrated or further subdivided. Furthermore, each function in Figure 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. Note that the details of the processing performed by each functional unit will not be described here; only their general functions will be outlined.

When the terminal device 103 uses DPD or DPoD, the information acquisition unit 901 acquires information for that 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 that trained model or polynomial (i.e., information indicating the characteristics of DPD or DPoD) from the base station device 101.

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 the DPD trained model or polynomial to be applied to the signal to be transmitted based at least on information about the power amplifier of the relay device 102. If the power amplifier of the terminal device 103 operates near the saturation region, the transmission control unit 902 may also consider information about the power amplifier of the terminal device 103 to identify the DPD trained model or polynomial to be applied to the signal to be transmitted. If the transmission control unit 902 receives information about the DPD trained model or polynomial from the base station device 101, it can use the trained model or polynomial as is. The transmission control unit 902 artificially distorts the signal to be transmitted by inputting the signal to be transmitted into the trained model or applying a polynomial to 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 this signal is canceled 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 to the base station device 101, the transmission control unit 902 can transmit the radio signal without applying DPD.

The reception control unit 903 controls the reception of signals 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 DPoD trained model or polynomial 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 DPoD trained model or polynomial to be applied to the received signal. The reception control unit 903 inputs the received signal into the trained model or applies the polynomial to the received signal, and obtains a processed received signal. The processed received signal has the nonlinear distortion of the power amplifier of the base station device 101 and the power amplifier of the relay device 102 canceled out 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, if DPD is applied in the base station device 101, the reception control unit 903 does not apply DPoD to the received signal.

(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 relay device 102's power amplifier (S1002) to acquire a trained DPD model. Here, if it is expected that nonlinear distortion will occur when the base station device 101 operates its own power amplifier near the saturation region, the base station device 101 performs machine learning taking into account the characteristics of its own power amplifier. Note that, although an example in which machine learning is performed will be described here, a polynomial representing the inverse transformation of the transfer function of nonlinear distortion may also be identified. Thereafter, when data to be transmitted is generated (S1003), the base station device 101 performs modulation, etc. 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).

This enables the terminal device 103 to receive radio signals that are not affected by nonlinear distortion that may occur in S1005 and S1007.

Next, using FIG. 11, an example of the processing flow when applying DPoD to a received signal at the base station device 101 is described. In this processing example, the relay device 102 notifies the base station device 101 of the nonlinear distortion characteristics of its own device's power amplifier (S1101). Furthermore, if the terminal device 103 anticipates that nonlinear distortion will occur due to operating its own device's power amplifier near the saturation region, it may notify the base station device 101 of the nonlinear distortion characteristics of its own device's power amplifier (S1102). The base station device 101 then performs machine learning based on the notified information about the relay device 102's power amplifier (and, if present, information about the terminal device 103's power amplifier) (S1103) to obtain a trained model for DPoD. Note that while an example in which machine learning is performed is described here, a polynomial representing the inverse transformation of the transfer function of the nonlinear distortion may also be identified. Thereafter, when data to be transmitted is generated (S1104), the terminal device 103 performs modulation and other operations 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 it into the trained model acquired in S1003 and applies DPoD to the received wireless signal (S1109).

This enables the base station device 101 to obtain a signal from the received signal in which the effects of nonlinear distortion that may occur in steps S1105 and S1107 have been cancelled.

Next, an example of the processing flow when applying DPD to a transmission signal in the terminal device 101 will be described using 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 then notifies the terminal device 103 of the nonlinear distortion characteristics of the relay device 102's power amplifier (S1202). The terminal device 103 performs machine learning based on the notified information about the relay device 102's power amplifier (S1002) to acquire a trained DPD model. Note that, for example, if the terminal device 103 anticipates that nonlinear distortion will occur due to operating its own power amplifier near the saturation region, it may also perform machine learning taking into account the nonlinear distortion characteristics of its own power amplifier. Note that, while an example of machine learning is described here, a polynomial representing the inverse transformation of the nonlinear distortion transfer function may also be identified. Thereafter, when data to be transmitted is generated (S1204), the terminal device 103 performs modulation, etc. 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). The terminal device 103 then 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).

This enables the base station device 101 to receive radio signals that are not affected by nonlinear distortion that may occur in steps S1206 and S1208.

Next, an example of the processing flow when applying DPoD to a received signal at the terminal device 101 will be described using FIG. 13 . In this processing example, the relay device 102 notifies the base station device 101 of the nonlinear distortion characteristics of its own device's power amplifier (S1301). The base station device 101 notifies the terminal device 103 of the nonlinear distortion characteristics of its own device's power amplifier (S1302). Note that, for example, if it is expected that nonlinear distortion will occur due to operating its own device's power amplifier near the saturation region, the base station device 101 may also notify the terminal device 103 of the nonlinear distortion characteristics of its own device's power amplifier. The terminal device 103 then performs machine learning based on the notified information about the relay device 102's power amplifier (and, if present, the information about the base station device 101's power amplifier) (S1303) to obtain a trained model for DPoD. Note that, although an example in which machine learning is performed is described here, a polynomial representing the inverse transformation of the nonlinear distortion transfer function may also be identified. Thereafter, when data to be transmitted is generated (S1304), the base station device 101 performs modulation and other processes 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 signal into the trained model acquired in S1303 and applies DPoD to the received wireless signal (S1309).

This enables the terminal device 103 to obtain a signal from the received signal in which the effects of nonlinear distortion that may occur in S1305 and S1307 have been cancelled.

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

The invention is not limited to the above-described embodiments, and various modifications and variations are possible within the scope of the invention.

Claims (14)

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: The base station device according to claim 1, wherein the second information is the first information. The base station device according to claim 2, wherein the second information further includes third information that can identify nonlinear distortion caused by a power amplifier included in the base station device. The base station device according to claim 1, wherein the second information is information indicating predistortion characteristics, determined based on the first information, that predistort a signal to be transmitted in order to compensate for nonlinear distortion caused by a power amplifier included in the relay device. 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. The base station device according to claim 1, wherein the second information is information indicating post-distortion characteristics, determined based on the first information, that 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. The base station device according to claim 1, wherein the second information is information indicating post-distortion characteristics that cancel nonlinear distortion caused by the power amplifier of the base station device and the power amplifier of the relay device from a received signal transmitted from the base station device and received via the relay device, the information being identified based on the first information and third information capable of identifying nonlinear distortion caused by the power amplifier of the base station device. 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: 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. The terminal device according to claim 8, wherein the second information is information indicating 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 based on the first information. 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: 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: A program for causing a computer to function as each of the means possessed by the base station device described in any one of claims 1 to 7. A program for causing a computer to function as each of the means possessed by the terminal device described in any one of claims 8 to 10.