Base station device, communication method, and computer program

Abstract

To improve the stability of communication between base stations and terminals.SOLUTION: A base station device includes a signal processing unit that converts a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal by OFDM modulation method, and converts the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal by OTFS modulation method, and a radio transmitting unit that transmits a multiplexed signal in which the OFDM modulated signal and OTFS modulated signal converted from the broadcast signal are multiplexed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a base station 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 influence of the Doppler effect is large for terminals moving at high speed, so the communication performance of the OFDM modulation method is also degraded. One solution to this problem is to use the OTFS modulation method, but the challenge was to switch appropriately between the OFDM modulation method and the OTFS modulation method. For example, while the OTFS modulation method has high adaptability to high-speed movement, it has the problem of requiring more signal processing for transmission and reception compared to the OFDM modulation method, so a method was needed to switch between them appropriately depending on the situation.

[0006] The present invention has been made in consideration of the above circumstances, and has as its object to appropriately switch between modulation schemes depending on the situation in a communication system that supports both OFDM modulation scheme and OTFS modulation scheme. [Means for solving the problem]

[0007] One aspect of the present invention is a base station device comprising: a signal processing unit that converts a broadcast signal to be broadcast to a terminal into an OFDM modulated signal by an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, and converts the broadcast signal to be broadcast to the terminal into an OTFS modulated signal by an OTFS (Orthogonal Time Frequency Space) modulation method, and a wireless transmission unit that transmits a multiplexed signal in which the OFDM modulated signal converted from the broadcast signal and the OTFS modulated signal are multiplexed. One aspect of the present invention is a base station device, as described above, further comprising a radio receiving unit that receives a terminal transmission signal in an OFDM modulation method or an OTFS modulation method transmitted from a terminal that has received the OFDM modulated signal or the OTFS modulated signal converted from the broadcast signal. One aspect of the present invention is the above-mentioned base station device, further comprising a determination unit that determines a moving state of a source terminal based on the terminal transmission signal received by the radio receiving unit. One aspect of the present invention is a base station device, wherein in the above-mentioned base station device, a broadcast signal transmitted using an OFDM modulation method includes resource information of a Random Access CHannel (RACH) transmitted by a terminal that receives the broadcast signal, and a broadcast signal transmitted using an OTFS modulation method includes resource information of a RACH transmitted by a terminal that receives the broadcast signal. One aspect of the present invention is a base station device, wherein in the above-mentioned base station device, the determination unit determines that the movement state of the transmitting terminal is slow when the resource of the terminal transmission signal received by the wireless receiving unit is a resource specified by a broadcast signal transmitted using an OFDM modulation method, and determines that the movement state of the transmitting terminal is fast when the resource of the terminal transmission signal received by the wireless receiving unit is a resource specified by a broadcast signal transmitted using an OTFS modulation method. One aspect of the present invention is a base station device, wherein in the above-mentioned base station device, the determination unit determines that the movement state of the transmitting terminal is low when the terminal transmission signal received by the wireless receiving unit is an OFDM modulation method, and determines that the movement state of the transmitting terminal is high when the terminal transmission signal received by the wireless receiving unit is an OTFS modulation method. One aspect of the present invention is a base station device further comprising a communication control unit that performs data communication using an OFDM modulation method for a terminal determined to be in a low-speed moving state, and performs data communication using an OTFS modulation method for a terminal determined to be in a high-speed moving state. One aspect of the present invention is the base station apparatus, wherein the broadcast signal is a PBCH (Physical Broadcast CHannel) signal. One aspect of the present invention is a base station device, as described above, further comprising a radio receiving unit that receives a Random Access CHannel (RACH) signal transmitted from the terminal using radio resources used for an OFDM modulation scheme or radio resources used for an OTFS modulation scheme notified to the terminal by the PBCH signal. One aspect of the present invention is the above-mentioned base station device, further comprising a determination unit that determines a movement state of a source terminal based on the RACH signal received by the radio receiving unit. One aspect of the present invention is a base station device, wherein in the above-mentioned base station device, the determination unit determines that the movement state of the source terminal is low when the RACH signal received by the wireless receiving unit is an OFDM modulation method, and determines that the movement state of the source terminal is high when the RACH signal received by the wireless receiving unit is an OTFS modulation method. One aspect of the present invention is a base station device further comprising a communication control unit that performs data communication using an OFDM modulation method for a terminal determined to be in a low-speed moving state, and performs data communication using an OTFS modulation method for a terminal determined to be in a high-speed moving state.

[0008] One aspect of the present invention is a communication method executed by a base station device, the communication method including: a signal processing step of converting a broadcast signal to be broadcast to a terminal into an OFDM modulated signal by an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, and converting the broadcast signal to be broadcast to the terminal into an OTFS modulated signal by an OTFS (Orthogonal Time Frequency Space) modulation method; and a wireless transmission step of transmitting a multiplexed signal in which the OFDM modulated signal converted from the broadcast signal and the OTFS modulated signal are multiplexed. One aspect of the present invention is the above-mentioned communication method, wherein the broadcast 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 base station device to execute a signal processing step of converting a broadcast signal to be broadcast to a terminal into an OFDM modulated signal by an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, and converting the broadcast signal to be broadcast to the terminal into an OTFS modulated signal by an OTFS (Orthogonal Time Frequency Space) modulation method, and a wireless transmission step of transmitting a multiplexed signal in which the OFDM modulated signal converted from the broadcast signal and the OTFS modulated signal are multiplexed. One aspect of the present invention is the computer program, wherein the broadcast signal is a PBCH (Physical Broadcast CHannel) signal. Effect of the Invention

[0010] According to the present invention, in a communication system compatible with both the OFDM modulation method and the OTFS modulation method, it is possible to obtain an effect of being able to appropriately switch the modulation method according to the situation. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a schematic configuration example of a base station device according to an embodiment. FIG. [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 (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 base station device according to an embodiment. The base station device 1 may be a base station (gNB) of a mobile communication system such as a 5G system, or an access point (AP) of a wireless LAN system. Hereinafter, a base station (gNB) of a mobile communication system such as a 5G system will be described as an example of the base station device 1 according to the present embodiment.

[0013] In FIG. 1, the base station device 1 includes a signal processing unit 10, a radio unit 20, an antenna 30, a determination unit 40, and a communication control unit 50.

[0014] Each part of the base station 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] A transmission signal A to be transmitted to a terminal (UE) is input to the signal processing unit 10. The transmission signal A is, for example, a broadcast signal broadcast to the terminal. The transmission signal A is, for example, a PBCH (Physical Broadcast Channel) signal. The PBCH signal is a broadcast signal broadcast to the terminal.

[0016] The signal processing unit 10 includes a subcarrier mapping unit 101, an ISFFT (Inverse Symplectic fast Fourier Transform) unit 102, a multiplexing unit 103, an IDFT (Inverse Discrete Fourier Transform) unit 104, a CP (Cyclic Prefix) adding unit 105, and a scheduler 106.

[0017] The subcarrier mapping unit 101 maps the transmission signal A to subcarriers. The scheduler 106 instructs the subcarrier mapping unit 101 as to which subcarrier the transmission signal A is to be mapped.

[0018] The ISFFT unit 102 performs ISFFT on the transmission signal A mapped to the subcarriers.

[0019] The multiplexing unit 103 multiplexes the transmission signal A mapped to the subcarriers and the ISFFT-processed transmission signal A. This multiplexing method may be a TDM (Time Division Multiplexing) method or an FDM (Frequency Division Multiplexing) method.

[0020] The IDFT unit 104 performs IDFT on a multiplexed signal in which the transmission signal A mapped to the subcarriers and the ISFFT-processed transmission signal A are multiplexed. The transmission signal A mapped to the subcarriers is subjected to IDFT to generate a signal of the OFDM (orthogonal frequency division multiplexing) modulation method of the transmission signal A (the OFDM modulated signal of the transmission signal A). The ISFFT-processed transmission signal A is subjected to IDFT to generate a signal of the OTFS (orthogonal time frequency space) modulation method of the transmission signal A (the OTFS modulated signal of the transmission signal A).

[0021] CP adding section 105 adds a CP to the IDFT output signal output from IDFT section 104. The IDFT output signal is a signal including the OFDM modulated signal of transmission signal A and the OTFS modulated signal of transmission signal A.

[0022] The radio unit 20 wirelessly transmits the CP-added IDFT output signal B to which the CP has been added via the antenna 30. As a result, the CP-added IDFT output signal B including the OFDM modulated signal of the transmission signal A and the OTFS modulated signal of the transmission signal A is wirelessly transmitted. The CP-added IDFT output signal B wirelessly transmitted from the base station device 1 is wirelessly received by the terminal.

[0023] The wireless unit 20 receives a terminal transmission signal C in the OFDM modulation method or the OTFS modulation method, which is transmitted from a terminal that has received the CP-added IDFT output signal B wirelessly transmitted from the base station device 1.

[0024] The determination unit 40 determines the moving state of the source terminal based on the terminal transmission signal C received by the wireless unit 20. As an example of a moving state determination method according to the present embodiment, when the terminal transmission signal C received by the wireless unit 20 is OFDM modulation type, the determination unit 40 determines that the moving state of the source terminal is slow. Note that slow includes stationary. On the other hand, when the terminal transmission signal C received by the wireless unit 20 is OTFS modulation type, the determination unit 40 determines that the moving state of the source terminal is fast.

[0025] The communication control unit 50 performs data communication using the OFDM modulation method for terminals determined to be moving at low speed, while the communication control unit 50 performs data communication using the OTFS modulation method for terminals determined to be moving at high speed.

[0026] Next, an example of the operation of the base station 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 transmission signal A.

[0027] (Step S1) The base station device 1 periodically wirelessly transmits a CP-added IDFT output signal B (a multiplexed signal of OFDM-PBCH and OTFS-PBCH) including an OFDM modulated signal of a PBCH signal and an OTFS modulated signal of the PBCH signal. Here, the PBCH signal has information of a RACH (random access channel) which is a common channel in the uplink direction. The RACH information includes OFDM resource designation information which designates radio resources to be used for the OFDM modulation method and OTFS resource designation information which designates radio resources to be used for 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).

[0028] A terminal that receives a CP-added IDFT output signal B wirelessly transmitted from base station device 1 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 the PBCH signal, acquires the RACH information contained in the acquired PBCH signal, and acquires the OFDM resource designation information and OTFS resource designation information contained in the acquired RACH information.

[0029] If the terminal successfully demodulates the OFDM modulated PBCH signal, the terminal transmits an uplink signal in accordance with the OFDM modulation scheme using the radio resources specified by the OFDM resource specification information.

[0030] 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 succeeds, the terminal transmits an uplink signal by the OTFS modulation scheme using the radio resource specified by the OTFS resource specification information. A terminal that succeeds in demodulation of the OTFS modulation scheme when demodulation of the OFDM modulation scheme fails is considered to be a terminal moving at high speed. As an example of a method for determining whether demodulation has been successful, a CRC (Cyclic Redundancy Check) included in the PBCH may be used. Note that the terminal may perform a CRC determination for each CP-added IDFT output signal B received multiple times, and determine whether demodulation of the PBCH of the OFDM modulation method has been successful or not based on the multiple determination results.

[0031] (Step S2) The base station device 1 receives a RACH (Random Access Channel) signal (terminal transmission signal C) of the OFDM modulation method or the OTFS modulation method transmitted from the terminal that has received the CP-added IDFT output signal B wirelessly transmitted from the base station device 1. The base station device 1 determines whether or not it has detected (received) a RACH signal of the OFDM modulation method (OFDM-RACH signal).

[0032] When it is determined that the RACH signal of the OFDM modulation method is detected (received) (step S2, YES), the base station device 1 records that the source terminal is moving at a low speed and is a terminal that transmits an uplink signal by the OFDM modulation method. Then, the process proceeds to step S4.

[0033] On the other hand, if it is determined that the RACH signal of the OFDM modulation method has not been detected (received) (step S2, NO), the process proceeds to step S3.

[0034] (Step S3) The base station device 1 determines whether or not it has detected (received) a RACH signal in the OTFS modulation method (OTFS-RACH signal).

[0035] When it is determined that the RACH signal of the OTFS modulation method is detected (received) (step S3, YES), the base station device 1 records that the source terminal is moving at high speed and is a terminal that transmits an uplink signal by the OTFS modulation method. Then, the process proceeds to step S6.

[0036] On the other hand, if it is determined that the RACH signal in the OTFS modulation method has not been detected (received) (step S3, NO), the process returns to step S2.

[0037] (Step S4) The base station device 1 uses the OFDM modulation scheme to complete initial access with the relevant terminal according to a predetermined random access procedure.

[0038] (Step S5) The base station device 1 performs data communication using OFDM modulated signals with the terminal whose moving state has been determined to be low speed by the OFDM modulation method.

[0039] (Step S6) The base station device 1 uses the OTFS modulation method to complete initial access with the relevant terminal according to a predetermined random access procedure.

[0040] (Step S7) The base station device 1 performs data communication using the OTFS modulation method with the terminal whose moving state has been determined to be high speed using the OTFS modulation method.

[0041] The base station device 1 may monitor a change in the modulation method used by the terminal (a change between the OFDM modulation method and the OTFS modulation method), determine an increase or decrease in the moving speed of the terminal from the monitoring result, and record the determination result of the increase or decrease in the moving speed of the terminal. When the modulation method is changed from the OFDM modulation method to the OTFS modulation method, the determination unit 40 determines that the moving speed of the terminal has increased. On the other hand, when the modulation method is changed from the OTFS modulation method to the OFDM modulation signal, the determination unit 40 determines that the moving speed of the terminal has decreased.

[0042] Also, a threshold value for the moving speed of the terminal when the modulation method is changed from the OFDM modulation method to the OTFS modulation method may be set in advance in the determination unit 40, and the determination unit 40 may estimate the moving speed of the terminal based on the threshold value. Also, a threshold value for the moving speed of the terminal when the modulation method is changed from the OTFS modulation method to the OFDM modulation method may be set in advance in the determination unit 40, and the determination unit 40 may estimate the moving speed of the terminal based on the threshold value.

[0043] 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 (UE). Here, a PBCH signal is used as an example of a transmission signal A.

[0044] (Step S101) The base station (gNB) periodically wirelessly transmits a CP-added IDFT output signal B (a multiplexed signal of OFDM-PBCH and OTFS-PBCH) including an OFDM modulated signal of a PBCH signal and an OTFS modulated signal of the PBCH signal.

[0045] The terminal (UE) receives the CP-added IDFT output signal B wirelessly transmitted from the base station device 1. The terminal (UE) that has received the CP-added IDFT output signal B 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.

[0046] (Step S102) If the terminal (UE) has successfully demodulated the OFDM modulated PBCH signal, the terminal (UE) transmits a RACH signal (OFDM-RACH signal) by the OFDM modulation scheme using the radio resource specified by the OFDM resource specification information.

[0047] 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 (UE) transmits a RACH signal (OTFS-RACH signal) by the OTFS modulation scheme using the radio resource specified by the OTFS resource specification information.

[0048] The base station (gNB) detects (receives) a RACH signal using the OFDM modulation method or the OTFS modulation method from the terminal (UE).

[0049] The base station (gNB) specifies, by the PBCH signal, radio resources used by the terminal (UE) for the OFDM modulation scheme and radio resources used for the OTFS modulation scheme, each of which is different from the other. This allows the base station (gNB) to determine whether the transmitting terminal (UE) is a terminal using the OFDM modulation scheme (a terminal moving at a low speed) or a terminal using the OTFS modulation scheme (a terminal moving at a high speed) by detecting the radio resources used for the RACH signal transmitted from the terminal (UE).

[0050] When the base station (gNB) detects (receives) a RACH signal from a terminal (UE) using a resource specified by a PBCH of the OFDM modulation method, the base station records that the source terminal (UE) is moving at a low speed and is a terminal that uses the OFDM modulation method in subsequent communications. On the other hand, when the base station (gNB) detects (receives) a RACH signal from a terminal (UE) using a resource specified by a PBCH of the OTFS modulation method, the base station records that the source terminal (UE) is moving at a high speed and is a terminal that transmits signals using the OTFS modulation method in subsequent communications.

[0051] (Step S103) If the terminal (UE) has successfully demodulated the OFDM modulated PBCH signal, the terminal (UE) completes a predetermined initial access procedure using the OFDM modulation method.

[0052] On the other hand, when the terminal (UE) fails to demodulate the OFDM modulated signal of the PBCH signal but succeeds in demodulating the OTFS modulated signal of the PBCH signal, the terminal (UE) completes a predetermined initial access procedure using the OTFS modulation method.

[0053] (Step S104) The base station (gNB) performs data communication with the terminal determined to be moving at a low speed using an OFDM modulated signal. On the other hand, the base station (gNB) performs data communication with the terminal determined to be moving at a high speed using the OTFS modulation method.

[0054] Next, a method for multiplexing an OFDM modulated signal and an OTFS modulated signal according to this embodiment will be described below. Figures 4-6 are diagrams showing examples of a method for multiplexing an OFDM modulated signal and an OTFS modulated signal according to this embodiment.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] According to this embodiment, a broadcast signal such as a PBCH signal to be broadcast to terminals can be broadcast by both the OFDM modulation method and the OTFS modulation method. As a result, even if a terminal moving at high speed fails to demodulate the OFDM modulation method, the terminal can correctly receive the broadcast signal because the demodulation of the OTFS modulation method is successful. Also, a terminal moving at low speed can correctly receive the broadcast signal because the demodulation of the OFDM modulation method is successful. Therefore, according to this embodiment, whether a terminal moving at high speed or a terminal moving at low speed can correctly receive a broadcast signal such as a PBCH signal, it is possible to obtain an effect of improving the stability of communication between a base station and terminals.

[0059] In addition, by receiving a terminal transmission signal using the OFDM modulation method or the OTFS modulation method transmitted from a terminal that has received an OFDM modulation signal or an OTFS modulation signal converted from a broadcast signal, it is possible to determine whether the source terminal is moving at a low speed or a high speed. This is because a low-speed terminal is likely to be able to successfully demodulate the OFDM modulation method, whereas a terminal moving at a high speed is likely to be able to successfully demodulate the OTFS modulation method even if the OFDM modulation method demodulation fails.

[0060] In addition, by performing data communication using the OFDM modulation method for terminals determined to be moving slowly, and performing data communication using the OTFS modulation method for terminals determined to be moving quickly, it is possible to select a modulation method suitable for the terminal's moving state, and by using the OFDM modulation method for terminals moving slowly, it is possible to reduce power consumption and processing delays required for signal processing.

[0061] 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."

[0062] 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.

[0063] 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.

[0064] 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]

[0065] REFERENCE SIGNS LIST 1... base station device, 10... signal processing unit, 20... radio unit, 30... antenna, 40... determination unit, 50... communication control unit, 101... subcarrier mapping unit, 102... ISFFT unit, 103... multiplexing unit, 104... IDFT unit, 105... CP adding unit, 106... scheduler

Claims

1. a signal processing unit that converts a broadcast signal to be broadcast to a terminal into an OFDM modulated signal by an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, and converts the broadcast signal to be broadcast to the terminal into an OTFS modulated signal by an OTFS (Orthogonal Time Frequency Space) modulation method; a wireless transmission unit for transmitting a multiplexed signal in which the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal are multiplexed; A base station device comprising:

2. a wireless receiving unit for receiving a terminal transmission signal of an OFDM modulation method or an OTFS modulation method transmitted from a terminal that has received the OFDM modulated signal or the OTFS modulated signal converted from the broadcast signal; The base station apparatus according to claim 1 , further comprising:

3. a determination unit that determines a moving state of a source terminal based on the terminal transmission signal received by the wireless receiving unit; The base station apparatus according to claim 2 , further comprising:

4. The broadcast signal transmitted by the OFDM modulation method includes resource information of a RACH (Random Access CHannel) transmitted by a terminal that receives the broadcast signal, The broadcast signal transmitted by the OTFS modulation method includes resource information of the RACH transmitted by the terminal that received this broadcast signal. The base station device according to claim 1 .

5. The determination unit is When the resource of the terminal transmission signal received by the wireless receiving unit is a resource designated by a broadcast signal transmitted by an OFDM modulation method, it is determined that the movement state of the transmitting terminal is low speed; When the resource of the terminal transmission signal received by the wireless receiving unit is a resource designated by a broadcast signal transmitted by an OTFS modulation method, the moving state of the transmitting terminal is determined to be high speed. The base station device according to claim 3 .

6. The determination unit is When the terminal transmission signal received by the wireless receiving unit is modulated by OFDM, it is determined that the moving state of the transmitting terminal is low speed; determining that the moving state of the transmitting terminal is high speed when the terminal transmission signal received by the wireless receiving unit is modulated by an OTFS modulation method; The base station device according to claim 3 .

7. a communication control unit that performs data communication by the OFDM modulation method with respect to a terminal determined to be moving at a low speed, and performs data communication by the OTFS modulation method with respect to a terminal determined to be moving at a high speed; The base station apparatus according to claim 6 , further comprising:

8. The broadcast signal is a PBCH (Physical Broadcast CHannel) signal. The base station device according to claim 1 .

9. a radio receiving unit that receives a RACH (Random Access CHannel) signal transmitted from the terminal using a radio resource for an OFDM modulation scheme or a radio resource for an OTFS modulation scheme notified to the terminal by the PBCH signal; The base station apparatus according to claim 8 , further comprising:

10. A determination unit that determines a moving state of a source terminal based on the RACH signal received by the wireless receiving unit; The base station apparatus according to claim 9 , further comprising:

11. The determination unit is When the RACH signal received by the wireless receiving unit is modulated by OFDM, it is determined that the moving state of the transmitting terminal is low speed, When the RACH signal received by the wireless receiving unit is modulated by an OTFS modulation method, it is determined that the moving state of the transmitting terminal is high speed. The base station device according to claim 10.

12. a communication control unit that performs data communication by the OFDM modulation method with respect to a terminal determined to be moving at a low speed, and performs data communication by the OTFS modulation method with respect to a terminal determined to be moving at a high speed; The base station apparatus according to claim 11, further comprising:

13. A communication method executed by a base station device, comprising: a signal processing step of converting a broadcast signal to be broadcast to a terminal into an OFDM modulated signal by an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, and converting the broadcast signal to be broadcast to the terminal into an OTFS modulated signal by an OTFS (Orthogonal Time Frequency Space) modulation method; a wireless transmission step of transmitting a multiplexed signal in which the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal are multiplexed; A communication method including:

14. The broadcast signal is a PBCH (Physical Broadcast CHannel) signal. The communication method according to claim 13.

15. The base station device computer a signal processing step of converting a broadcast signal to be broadcast to a terminal into an OFDM modulated signal by an OFDM (Orthogonal Frequency Division Multiplexing) modulation method, and converting the broadcast signal to be broadcast to the terminal into an OTFS modulated signal by an OTFS (Orthogonal Time Frequency Space) modulation method; a wireless transmission step of transmitting a multiplexed signal in which the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal are multiplexed; A computer program for executing the above.

16. The broadcast signal is a PBCH (Physical Broadcast CHannel) signal.

16. A computer program according to claim 15.

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