Terminal device, communication method, and computer program

Abstract

To improve the stability of communication between base stations and terminals.SOLUTION: A terminal device includes a radio receiving unit that receives a multiplexed signal, in which an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal of a base station transmission signal and an OTFS (Orthogonal Time Frequency Space) modulated signal of the base station transmission signal are multiplexed, transmitted from a base station, a signal processing unit that performs demodulation of an OTFS modulation method when demodulation of an OFDM modulation method on the received multiplexed signal fails, and a radio transmitting unit that transmits a first terminal transmission signal notifying the base station that the demodulation of the OTFS modulation method has been successful when the demodulation of the OFDM modulation method on the received multiplexed signal has failed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a terminal device, a communication method, and a computer program. [Background technology]

[0002] In a fifth generation (5G) mobile communication system (hereinafter referred to as a 5G system), in the initial access of a terminal (UE), a base station (gNB) uses a broadcast channel (PBCH (Physical Broadcast CHannel)) to simultaneously broadcast broadcast information required for the terminal to perform a connection procedure to a cell. The broadcast information includes, for example, information on a common channel in the downlink direction (direction from the base station to the terminal) and information on a Random Access Channel (RACH) which is a common channel in the uplink direction (direction from the terminal to the base station).

[0003] Patent Document 1 describes a technique that uses different modulation methods for the upstream and downstream directions. For example, the Orthogonal Time Frequency Space (OTFS) modulation method is used for the upstream direction, while the Orthogonal Frequency Division Multiplexing (OFDM) modulation method is used for the downstream direction. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2022 / 217536 Summary of the Invention [Problem to be solved by the invention]

[0005] The communication performance of the OFDM modulation method is degraded by the Doppler effect when the terminal is moving. In particular, the Doppler effect is more pronounced for terminals moving at high speeds, so the communication performance of the OFDM modulation method is also more degraded. One way to address this issue is to use the OTFS modulation method, but the issue was how to use the OFDM modulation method and the OTFS modulation method.

[0006] The present invention has been made in consideration of the above circumstances, and has an object to improve the stability of communications between a base station and a terminal. [Means for solving the problem]

[0007] One aspect of the present invention is a terminal device comprising: a wireless receiving unit that receives a multiplexed signal transmitted from a base station by multiplexing an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal of a base station transmission signal and an OTFS (Orthogonal Time Frequency Space) modulated signal of a base station transmission signal; a signal processing unit that performs OTFS modulation method demodulation on the received multiplexed signal when demodulation of the OFDM modulation method fails; and a wireless transmitting unit that transmits a first terminal transmission signal notifying the base station that demodulation of the OTFS modulation method was successful when demodulation of the OFDM modulation method on the received multiplexed signal fails. One aspect of the present invention is the terminal device, wherein the first terminal transmission signal is an OTFS modulated signal. One aspect of the present invention is a terminal device as described above, in which the radio transmission unit transmits a second terminal transmission signal to notify the base station that demodulation of the OFDM modulation scheme for the received multiplexed signal has been successful. One aspect of the present invention is the terminal device, wherein the second terminal transmission signal is an OFDM modulated signal. One aspect of the present invention is the terminal device, wherein the base station transmission signal is a PBCH (Physical Broadcast CHannel) signal. One aspect of the present invention is the terminal device, wherein the first terminal transmission signal is an OTFS modulated signal of a RACH (Random Access CHannel) signal. One aspect of the present invention is a terminal device in which the radio transmitting unit transmits an OFDM modulated signal of a RACH signal as a second terminal transmission signal notifying the base station that demodulation of the received multiplexed signal using an OFDM modulation scheme has been successful.

[0008] One aspect of the present invention is a communication method executed by a terminal device, the communication method including: a wireless receiving step of receiving a multiplexed signal transmitted from a base station by multiplexing an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal of a base station transmission signal and an OTFS (Orthogonal Time Frequency Space) modulated signal of a base station transmission signal; a signal processing step of demodulating the received multiplexed signal using an OTFS modulation method when demodulation using the OFDM modulation method has failed; and a wireless transmitting step of transmitting a first terminal transmission signal notifying the base station that demodulation using the OTFS modulation method has been successful when demodulation using the OFDM modulation method has failed for the received multiplexed signal. One aspect of the present invention is the above-mentioned communication method, wherein the base station transmission signal is a PBCH (Physical Broadcast CHannel) signal.

[0009] One aspect of the present invention is a computer program for causing a computer of a terminal device to execute the following steps: a wireless receiving step of receiving a multiplexed signal transmitted from a base station by multiplexing an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal of a base station transmission signal and an OTFS (Orthogonal Time Frequency Space) modulated signal of a base station transmission signal; a signal processing step of demodulating the received multiplexed signal using an OTFS modulation scheme when demodulation using the OFDM modulation scheme has failed; and a wireless transmitting step of transmitting a first terminal transmission signal notifying the base station that demodulation using the OTFS modulation scheme has been successful when demodulation using the OFDM modulation scheme has failed for the received multiplexed signal. One aspect of the present invention is the computer program, wherein the base station transmission signal is a PBCH (Physical Broadcast CHannel) signal. Effect of the Invention

[0010] According to the present invention, it is possible to obtain an effect that the stability of communication between a base station and a terminal can be improved. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a schematic configuration example of a terminal device according to an embodiment; [Diagram 2] 1 is a flowchart illustrating an example of a procedure of a communication method according to an embodiment. [Diagram 3] 1 is a sequence chart between a base station (gNB) and a terminal device (UE) showing an example of a procedure of a communication method according to an embodiment. [Figure 4] 1 is a diagram illustrating an example of a multiplexing method of an OFDM modulated signal and an OTFS modulated signal according to an embodiment. [Diagram 5] 1 is a diagram illustrating an example of a multiplexing method of an OFDM modulated signal and an OTFS modulated signal according to an embodiment. [Figure 6]1 is a diagram illustrating an example of a multiplexing method of an OFDM modulated signal and an OTFS modulated signal according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 is a block diagram showing a schematic configuration example of a terminal device according to an embodiment. The terminal device 1 may be a terminal (UE) of a mobile communication system such as a 5G system, or a terminal of a wireless LAN system. Hereinafter, a terminal (UE) of a mobile communication system such as a 5G system will be described as an example of the terminal device 1 according to the present embodiment.

[0013] In FIG. 1, the terminal device 1 includes a signal processing unit 10, a radio unit 20, an antenna 30, a communication control unit 50, and a transmission processing unit 60.

[0014] Each part of the terminal device 1 may be realized by dedicated hardware, or may be composed of a CPU (Central Processing Unit) and memory, etc., and the functions of each part may be realized by the CPU executing a computer program for realizing the function of each part.

[0015] The radio unit 20 receives a radio signal transmitted from a base station device via the antenna 30. A received signal A, which is a radio signal transmitted from the base station device and received by the radio unit 20, is input to the signal processing unit 10. The received signal A is, for example, a broadcast signal broadcast to terminals. The received signal A is, for example, a PBCH (Physical Broadcast Channel) signal. The PBCH signal is a broadcast signal broadcast to terminals.

[0016] The signal processing unit 10 includes a CP (Cyclic Prefix) removal unit 101, an OFDM (Orthogonal Frequency Division Multiplexing) demodulation unit 102, an OTFS (Orthogonal Time Frequency Space) demodulation unit 103, and a determination unit 104.

[0017] The CP removal unit 101 removes the CP from the received signal A.

[0018] The OFDM demodulation unit 102 performs OFDM demodulation on a CP-removed received signal B, which is obtained by removing the CP from received signal A.

[0019] The OTFS demodulation unit 103 performs OTFS demodulation on the CP-removed received signal B obtained by removing the CP from the received signal A.

[0020] The decision unit 104 decides whether or not the demodulation of the OFDM modulation scheme has been successful for the OFDM demodulated signal C that is the result of the demodulation of the CP removed received signal B according to the OFDM modulation scheme.

[0021] The determination unit 104 determines whether or not the demodulation of the OTFS modulation scheme has been successful with respect to an OTFS demodulated signal D, which is the result of demodulating the CP-removed received signal B using the OTFS modulation scheme.

[0022] If demodulation using the OFDM modulation method fails, the determination unit 104 outputs an OTFS demodulation control signal E instructing demodulation using the OTFS modulation method to the OTFS demodulation unit 103. In response to the OTFS demodulation control signal E instructing demodulation using the OTFS modulation method, the OTFS demodulation unit 103 starts demodulation using the OTFS modulation method for the CP-removed received signal B. If demodulation using the OTFS modulation method is not instructed by the OTFS demodulation control signal E, the OTFS demodulation unit 103 does not demodulate the CP-removed received signal B using the OTFS modulation method.

[0023] When the demodulation of the OFDM modulation method is successful, the determination unit 104 outputs an OTFS demodulation control signal E instructing the OTFS modulation method to be stopped, to the OTFS demodulation unit 103. The OTFS demodulation unit 103 stops the demodulation of the OTFS modulation method for the CP-removed received signal B in response to the OTFS demodulation control signal E instructing the OTFS modulation method to be stopped.

[0024] The determination unit 104 outputs to the communication control unit 50 a demodulation status signal G indicating whether demodulation in the OFDM modulation method and demodulation in the OTFS modulation method have been successful.

[0025] When demodulation of the OFDM modulation method is successful, the determination unit 104 outputs the OFDM demodulated signal C as the demodulated signal F. When demodulation of the OTFS modulation method is successful when demodulation of the OFDM modulation method is successful, the determination unit 104 outputs the OTFS demodulated signal D as the demodulated signal F.

[0026] The communication control unit 50 determines whether the OFDM modulation method or the OTFS modulation method is to be used for transmission to the base station device based on the demodulation status signal G. When the demodulation status signal G indicates that the OFDM modulation method has been successfully demodulated, the communication control unit 50 uses the OFDM modulation method for transmission to the base station device. When the demodulation status signal G indicates that the OFDM modulation method has been unsuccessful but that the OTFS modulation method has been successfully demodulated, the communication control unit 50 uses the OTFS modulation method for transmission to the base station device. The communication control unit 50 instructs the transmission processing unit 60 as to whether the OFDM modulation method or the OTFS modulation method is to be used for transmission to the base station device.

[0027] The transmission processing unit 60 modulates a signal (terminal transmission signal) to be transmitted to the base station device using a modulation method designated by the communication control unit 50 from among the OFDM modulation method and the OTFS modulation method.

[0028] The OFDM modulated signal obtained by converting the terminal transmission signal by the OFDM modulation method is wirelessly transmitted by the radio unit 20 via the antenna 30 and received by the base station device. The OTFS modulated signal obtained by converting the terminal transmission signal by the OTFS modulation method is wirelessly transmitted by the radio unit 20 via the antenna 30 and received by the base station device.

[0029] Next, an example of the operation of the terminal device 1 according to this embodiment will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a flowchart showing an example of the procedure of the communication method according to this embodiment. Here, a PBCH signal is used as an example of the received signal A.

[0030] (Step S1) The base station device periodically wirelessly transmits a multiplexed signal (OFDM-PBCH and OTFS-PBCH multiplexed signal) including an OFDM modulated signal of a PBCH signal and an OTFS modulated signal of the PBCH signal. The multiplexing method of the multiplexed signal may be a TDM (Time Division Multiplexing) method or an FDM (Frequency Division Multiplexing) method.

[0031] Here, the PBCH signal has information (RACH information) of a random access channel (RACH) which is an uplink common channel. The RACH information includes OFDM resource designation information that designates radio resources used in the OFDM modulation method and OTFS resource designation information that designates radio resources used in the OTFS modulation method. In addition, from the viewpoint of correct detection of RACH, it is preferable to operate the RACH of the OFDM modulation scheme and the RACH of the OTFS modulation scheme so that they do not interfere with each other by setting the radio resource of the RACH used in the OFDM modulation scheme and the radio resource of the RACH used in the OTFS modulation scheme to different time-frequency resources. In this case, the RACH information of the PBCH signal included in the OFDM modulated signal and the RACH information of the PBCH signal included in the OTFS modulated signal may be common information having both OFDM resource designation information and OTFS resource designation information, or may be separate information having only the respective resource designation information (the OFDM modulated signal has only the OFDM resource designation information, and the OTFS modulated signal has only the OTFS resource designation information).

[0032] The terminal device 1 receives a multiplexed signal of OFDM-PBCH and OTFS-PBCH periodically wirelessly transmitted from a base station device. The terminal device 1 removes the CP from the received multiplexed signal of OFDM-PBCH and OTFS-PBCH (received signal A).

[0033] (Step S2) The terminal device 1 performs OFDM modulation demodulation on a CP-removed received signal B in which the CP has been removed from the received OFDM-PBCH and OTFS-PBCH multiplexed signal (received signal A). The terminal device 1 determines whether the OFDM modulation demodulation has been successful for an OFDM demodulated signal C that is the result of the demodulation using the OFDM modulation method.

[0034] As an example of this determination method, CRC (Cyclic Redundancy Check) may be used. The base station device includes a CRC code of the PBCH signal in the multiplexed signal of OFDM-PBCH and OTFS-PBCH. The terminal device 1 determines whether or not a PBCH signal of the OFDM modulation method has been received (whether demodulation of the OFDM modulation method has been successful) using the CRC code of the PBCH signal included in the multiplexed signal of OFDM-PBCH and OTFS-PBCH. The terminal device 1 may perform a determination using the CRC for each of the multiple received OFDM-PBCH and OTFS-PBCH multiplexed signals, and determine whether or not a PBCH signal of the OFDM modulation method has been received (whether demodulation of the OFDM modulation method has been successful) from the multiple determination results.

[0035] If it is determined that a PBCH signal using the OFDM modulation method has been received (demodulation using the OFDM modulation method has been successful) (step S2, YES), the process proceeds to step S4. On the other hand, if it is determined that a PBCH signal using the OFDM modulation method has not been received (demodulation using the OFDM modulation method has failed) (step S2, NO), the process proceeds to step S3.

[0036] (Step S3) The terminal device 1 performs OTFS modulation demodulation on a CP-removed received signal B in which the CP has been removed from the received OFDM-PBCH and OTFS-PBCH multiplexed signal (received signal A). The terminal device 1 determines whether or not the OTFS modulation demodulation has been successful for an OTFS demodulated signal D that is the result of the demodulation using the OTFS modulation method. As an example of a method for this determination, a CRC may be used, as in the case of the OFDM modulation method.

[0037] If it is determined that a PBCH signal using the OTFS modulation method has been received (demodulation using the OTFS modulation method has been successful) (step S3, YES), the process proceeds to step S7. On the other hand, if it is determined that a PBCH signal using the OTFS modulation method has not been received (demodulation using the OTFS modulation method has failed) (step S3, NO), the process returns to step S2.

[0038] (Step S4) Since the demodulation of the OFDM modulation scheme is successful, the terminal device 1 uses the OFDM modulation scheme for transmission to the base station device. When the demodulation of the OFDM modulated signal of the PBCH signal is successful, the terminal device 1 transmits an uplink signal by the OFDM modulation scheme using the radio resource specified by the OFDM resource designation information included in the PBCH signal. The terminal device 1 transmits a RACH signal (OFDM-RACH signal) of the OFDM modulation scheme obtained by converting the RACH signal by the OFDM modulation scheme using the radio resource specified by the OFDM resource designation information.

[0039] When the base station device determines that it has received a RACH signal of the OFDM modulation method from the terminal device 1, it records that the source terminal device 1 is moving at a low speed and is a terminal that transmits uplink signals by the OFDM modulation method. Note that low speed also includes stationary.

[0040] (Step S5) The terminal device 1 uses the radio resources specified by the OFDM resource specification information to complete initial access to the relevant base station by the OFDM modulation scheme, following a predetermined random access procedure.

[0041] (Step S6) The terminal device 1 performs data communication with the base station device using an OFDM modulated signal.

[0042] (Step S7) Since the demodulation of the OTFS modulation method was successful when the demodulation of the OFDM modulation method failed, the terminal device 1 uses the OTFS modulation method for transmission to the base station device. If the demodulation of the OTFS modulated signal of the PBCH signal is successful, the terminal device 1 transmits an uplink signal by the OTFS modulation method using the radio resource specified by the OTFS resource designation information included in the PBCH signal. The terminal device 1 transmits a RACH signal (OTFS-RACH signal) of the OTFS modulation method obtained by converting the RACH signal by the OTFS modulation method using the radio resource specified by the OTFS resource designation information.

[0043] When the base station device determines that it has received a RACH signal of the OTFS modulation method from the terminal device 1, it records that the source terminal device 1 is moving at high speed and is a terminal that transmits an uplink signal by the OTFS modulation method. If the demodulation of the OFDM modulation method fails, the terminal that succeeds in demodulation of the OTFS modulation method is considered to be a terminal moving at high speed.

[0044] (Step S8) The terminal device 1 uses the wireless resource specified by the OTFS resource specification information to complete initial access to the relevant base station by the OTFS modulation method according to a predetermined random access procedure.

[0045] (Step S9) The terminal device 1 performs data communication with the base station device using an OTFS modulated signal.

[0046] The base station device may monitor a change in the modulation method used by the terminal device 1 (a change between the OFDM modulation method and the OTFS modulation method), determine an increase or decrease in the moving speed of the terminal device 1 from the monitoring result, and record the determination result of the increase or decrease in the moving speed of the terminal device 1. When the modulation method is changed from the OFDM modulation method to the OTFS modulation method, the base station device determines that the moving speed of the terminal device 1 has increased. On the other hand, when the modulation method is changed from the OTFS modulation method to the OFDM modulation signal, the base station device determines that the moving speed of the terminal device 1 has decreased.

[0047] Also, a threshold value of the moving speed of the terminal device 1 when the modulation method is changed from the OFDM modulation method to the OTFS modulation method may be set in advance in the base station device, and the base station device may estimate the moving speed of the terminal device 1 using the threshold value. Also, a threshold value of the moving speed of the terminal device 1 when the modulation method is changed from the OTFS modulation method to the OFDM modulation method may be set in advance in the base station device, and the base station device may estimate the moving speed of the terminal device 1 using the threshold value.

[0048] 3 is a sequence chart showing an example of a procedure of a communication method according to the present embodiment between a base station (gNB) and a terminal device 1 (UE). Here, a PBCH signal is used as an example of a received signal A.

[0049] (Step S101) The base station (gNB) periodically wirelessly transmits a multiplexed signal (OFDM-PBCH and OTFS-PBCH multiplexed signal) including an OFDM modulated signal of a PBCH signal and an OTFS modulated signal of the PBCH signal.

[0050] The terminal device 1 (UE) receives a multiplexed signal of OFDM-PBCH and OTFS-PBCH wirelessly transmitted from a base station device. The terminal device 1 (UE) that has received the multiplexed signal of OFDM-PBCH and OTFS-PBCH acquires the PBCH signal by successfully demodulating either the OFDM modulated signal of the PBCH signal or the OTFS modulated signal of the PBCH signal, acquires RACH information included in the acquired PBCH signal, and acquires OFDM resource designation information and OTFS resource designation information included in the acquired RACH information.

[0051] (Step S102) If the demodulation of the OFDM modulated PBCH signal is successful, the terminal device 1 (UE) transmits a RACH signal (OFDM-RACH signal) by the OFDM modulation scheme using the radio resource specified by the OFDM resource specification information.

[0052] On the other hand, when the demodulation of the OFDM modulated signal of the PBCH signal fails but the demodulation of the OTFS modulated signal of the PBCH signal is successful, the terminal device 1 (UE) transmits a RACH signal (OTFS-RACH signal) by the OTFS modulation method using the radio resource specified by the OTFS resource specification information.

[0053] The base station (gNB) receives a RACH signal using the OFDM modulation method or the OTFS modulation method from the terminal (UE).

[0054] The base station (gNB) specifies, by the PBCH signal, the radio resources used by the terminal device 1 (UE) for the OFDM modulation method and the radio resources used for the OTFS modulation method, each of which is different from the other. This allows the base station (gNB) to detect the radio resources used for the RACH signal transmitted from the terminal device 1 (UE) to determine whether the transmitting terminal device 1 (UE) is a terminal using the OFDM modulation method (a terminal moving at a low speed) or a terminal using the OTFS modulation method (a terminal moving at a high speed).

[0055] When a base station (gNB) receives a RACH signal of OFDM modulation from a terminal device 1 (UE), the base station records that the terminal device 1 (UE) is moving at a low speed and is a terminal that transmits uplink signals by the OFDM modulation. On the other hand, when a base station (gNB) receives a RACH signal of OTFS modulation from a terminal device 1 (UE), the base station records that the terminal device 1 (UE) is moving at a high speed and is a terminal that transmits uplink signals by the OTFS modulation.

[0056] (Step S103) If the demodulation of the OFDM modulated signal of the PBCH signal is successful, the terminal (UE) completes a predetermined initial access procedure using the OFDM modulation method. On the other hand, if the demodulation of the OFDM modulated signal of the PBCH signal is unsuccessful but the demodulation of the OTFS modulated signal of the PBCH signal is successful, the terminal (UE) completes a predetermined initial access procedure using the OTFS modulation method.

[0057] The base station (gNB) detects a reference signal of the OFDM modulation method or the OTFS modulation method transmitted from the terminal device 1 (UE).

[0058] (Step S104) The base station (gNB) performs data communication by OFDM modulation signals with the terminal device 1 (terminal whose moving state is determined to be low speed) that transmits uplink signals by the OFDM modulation method. On the other hand, the base station (gNB) performs data communication by OTFS modulation with the terminal device 1 (terminal whose moving state is determined to be high speed) that transmits uplink signals by the OTFS modulation method.

[0059] Next, a method for multiplexing an OFDM modulated signal and an OTFS modulated signal according to this embodiment will be described below. Figures 4 to 6 are diagrams showing examples of a method for multiplexing an OFDM modulated signal and an OTFS modulated signal according to this embodiment.

[0060] Fig. 4(1) shows an example of multiplexing an OFDM modulated signal and an OTFS modulated signal for a PBCH signal using the TDM method. Fig. 4(2) shows an example of multiplexing an OFDM modulated signal and an OTFS modulated signal for a PBCH signal using the FDM method.

[0061] Fig. 5(1) shows another example of multiplexing an OFDM modulated signal and an OTFS modulated signal by TDM for a PBCH signal. Fig. 5(2) shows another example of multiplexing an OFDM modulated signal and an OTFS modulated signal by FDM for a PBCH signal.

[0062] FIG. 6 shows an example in which an OFDM modulated signal and an OTFS modulated signal are multiplexed using the TDM method and the FDM method for a PBCH signal.

[0063] According to this embodiment, the base station transmission signal, such as a PBCH signal, transmitted from the base station device to the terminal device 1 can be transmitted from the base station device by both the OFDM modulation method and the OTFS modulation method. As a result, even if the terminal device 1 moving at high speed fails to demodulate the OFDM modulation method, the terminal device 1 can correctly receive the base station transmission signal by successfully demodulating the OTFS modulation method. Also, the terminal device 1 moving at low speed can correctly receive the base station transmission signal by successfully demodulating the OFDM modulation method. Therefore, according to this embodiment, even if the terminal device 1 moving at high speed or at low speed is capable of correctly receiving the base station transmission signal, such as a PBCH signal, the effect of improving the stability of communication between the base station and the terminal can be obtained.

[0064] In addition, since the terminal device 1 performs demodulation using the OTFS modulation method when demodulation using the OFDM modulation method fails, it is not necessary to perform demodulation using the OTFS modulation method all the time. This makes it possible to reduce power consumption in the terminal device 1.

[0065] In addition, the base station device can determine whether the moving state of the transmitting terminal device 1 is low speed or high speed by receiving a terminal transmission signal of the OFDM modulation method or the OTFS modulation method transmitted from the terminal device 1 that has received the OFDM modulation signal or the OTFS modulation signal converted from the base station transmission signal. This is because it is considered that the slow terminal device 1 will succeed in demodulating the OFDM modulation method, while the terminal device 1 moving at high speed will succeed in demodulating the OTFS modulation method even if the demodulation of the OFDM modulation method fails.

[0066] In addition, a terminal device 1 determined to be moving at a low speed performs data communication using the OFDM modulation method, and a terminal device 1 determined to be moving at a high speed performs data communication using the OTFS modulation method, thereby contributing to realizing stable data communication between the base station and the terminal device 1.

[0067] This will, for example, make it possible to improve the overall service quality of mobile communications systems, thereby contributing to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote sustainable industrialization and foster innovation."

[0068] Although an embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like that do not deviate from the gist of the present invention are also included.

[0069] In addition, a computer program for implementing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the program recorded on the recording medium may be read into a computer system and executed. Note that the "computer system" referred to here may include hardware such as an OS and peripheral devices. In addition, the term "computer-readable recording medium" refers to writable non-volatile memory such as a flexible disk, an optical magnetic disk, a ROM, or a flash memory, a portable medium such as a DVD (Digital Versatile Disc), or a storage device such as a hard disk built into a computer system.

[0070] Furthermore, the term "computer-readable recording medium" includes devices that retain a program for a certain period of time, such as volatile memory (e.g., DRAM (Dynamic Random Access Memory)) within a computer system that serves as a server or client when a program is transmitted via a network such as the Internet or a communication line such as a telephone line. The program may be transmitted from a computer system in which the program is stored in a storage device or the like to another computer system via a transmission medium, or by a transmission wave in the transmission medium. Here, the "transmission medium" that transmits the program refers to a medium that has a function of transmitting information, such as a network (communication network) such as the Internet or a communication line (communication line) such as a telephone line. The program may be for implementing some of the functions described above, or may be a so-called differential file (differential program) that can implement the functions described above in combination with a program already recorded in the computer system. [Explanation of symbols]

[0071] 1... terminal device, 10... signal processing unit, 20... radio unit, 30... antenna, 50... communication control unit, 60... transmission processing unit, 101... CP removal unit, 102... OFDM demodulation unit, 103... OTFS demodulation unit, 104... determination unit

Claims

1. a wireless receiving unit for receiving a multiplexed signal transmitted from a base station, the multiplexed signal being an orthogonal frequency division multiplexing (OFDM) modulated signal of a base station transmission signal and an orthogonal time frequency space (OTFS) modulated signal of a base station transmission signal; a signal processing unit that performs demodulation of the received multiplexed signal according to an OTFS modulation scheme when demodulation of the received multiplexed signal according to an OFDM modulation scheme has failed; a wireless transmission unit that transmits a first terminal transmission signal to notify the base station that demodulation of the received multiplexed signal according to the OTFS modulation method has been successful when demodulation of the received multiplexed signal according to the OFDM modulation method has failed; A terminal device comprising:

2. The first terminal transmission signal is an OTFS modulated signal; The terminal device according to claim 1 .

3. the wireless transmission unit transmits a second terminal transmission signal to notify the base station that demodulation of the received multiplexed signal according to the OFDM modulation method has been successful. The terminal device according to claim 1 or 2.

4. The second terminal transmission signal is an OFDM modulated signal. The terminal device according to claim 3.

5. The base station transmission signal is a PBCH (Physical Broadcast CHannel) signal. The terminal device according to claim 1 .

6. The first terminal transmission signal is an OTFS modulated signal of a RACH (Random Access CHannel) signal. The terminal device according to claim 5.

7. the wireless transmission unit transmits an OFDM modulated signal of a RACH signal as a second terminal transmission signal for notifying the base station that demodulation of the received multiplexed signal according to the OFDM modulation method has been successful. The terminal device according to claim 5 or 6.

8. A communication method executed by a terminal device, comprising: a wireless receiving step of receiving a multiplexed signal transmitted from a base station, the multiplexed signal being an orthogonal frequency division multiplexing (OFDM) modulated signal of a base station transmission signal and an orthogonal time frequency space (OTFS) modulated signal of a base station transmission signal; a signal processing step of performing demodulation of the received multiplexed signal according to an OTFS modulation scheme when demodulation of the OFDM modulation scheme has failed; a wireless transmission step of transmitting a first terminal transmission signal for notifying the base station that demodulation of the received multiplexed signal in the OTFS modulation scheme has been successful when demodulation of the received multiplexed signal in the OFDM modulation scheme has failed; A communication method including:

9. The base station transmission signal is a PBCH (Physical Broadcast CHannel) signal. The communication method according to claim 8.

10. The terminal device computer a wireless receiving step of receiving a multiplexed signal transmitted from a base station, the multiplexed signal being an orthogonal frequency division multiplexing (OFDM) modulated signal of a base station transmission signal and an orthogonal time frequency space (OTFS) modulated signal of a base station transmission signal; a signal processing step of performing demodulation of the received multiplexed signal according to an OTFS modulation scheme when demodulation of the OFDM modulation scheme has failed; a wireless transmission step of transmitting a first terminal transmission signal for notifying the base station that demodulation of the received multiplexed signal in the OTFS modulation scheme has been successful when demodulation of the received multiplexed signal in the OFDM modulation scheme has failed; A computer program for executing the above.

11. The base station transmission signal is a PBCH (Physical Broadcast CHannel) signal.

11. A computer program product as claimed in claim 10.

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