Base station equipment, communication methods, and computer programs

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 apparatus, a communication method, and a computer program. 【Background Art】 【0002】 In a fifth-generation (5G) mobile communication system (hereinafter referred to as a 5G system), at the initial access of a terminal (UE), a base station (gNB) simultaneously broadcasts notification information necessary for the terminal to perform a connection procedure to a cell using a notification channel (PBCH (Physical Broadcast CHannel)). The notification information includes, for example, information on a downlink (direction from the base station to the terminal) common channel and information on a random access channel (RACH) which is an uplink (direction from the terminal to the base station) common channel. 【0003】 Patent Document 1 describes a technique using different modulation schemes in the uplink and downlink directions. For example, the OTFS (Orthogonal Time Frequency Space) modulation scheme is used in the uplink direction, while the OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme is used in the downlink direction. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 International Publication No. 2022 / 217536 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 OFDM modulation suffers from degraded communication performance due to the Doppler effect when the terminal is moving. This degradation is particularly pronounced in terminals moving at high speeds, leading to a greater deterioration in OFDM performance. While OTFS modulation can be used to address this problem, the challenge lies in appropriately switching between OFDM and OTFS modulation. For example, OTFS modulation offers superior tracking capabilities for high-speed movement, but it also requires more signal processing for transmission and reception compared to OFDM modulation. Therefore, a method was needed to appropriately switch between these modes depending on the situation. 【0006】 This invention was made in consideration of these circumstances, and its purpose is to appropriately switch between modulation schemes depending on the situation in a communication system that supports both OFDM modulation and OTFS modulation schemes. [Means for solving the problem] 【0007】 One aspect of the present invention 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 using the OFDM modulation method, and converts the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS modulation method, and a wireless transmission unit that transmits a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal. A wireless receiving unit that receives an OFDM modulated signal or an OTFS modulated signal transmitted from a terminal that has received the OFDM modulated signal or the OTFS modulated signal converted from the broadcast signal, and a determination unit that determines the movement status of the transmitting terminal based on the terminal transmission signal received by the wireless receiving unit, This is a base station device equipped with [the following features]. One aspect of the present invention is a base station device in which the determination unit determines that the movement status of the transmitting terminal is slow if the resource of the terminal transmission signal received by the wireless receiver is the resource specified by the broadcast signal transmitted using OFDM modulation, and determines that the movement status of the transmitting terminal is fast if the resource of the terminal transmission signal received by the wireless receiver is the resource specified by the broadcast signal transmitted using OTFS modulation. One aspect of the present invention is a base station device in which the determination unit determines that the movement state of the transmitting terminal is slow when the terminal transmission signal received by the wireless receiver is in OFDM modulation, and determines that the movement state of the transmitting terminal is fast when the terminal transmission signal received by the wireless receiver is in OTFS modulation. One aspect of the present invention is a base station device further comprising a communication control unit that performs data communication using the OFDM modulation scheme for terminals determined to be moving at a low speed, and performs data communication using the OTFS modulation scheme for terminals determined to be moving at a high speed. One aspect of the present invention is, The system comprises a signal processing unit that converts a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using the OFDM modulation method, and converts the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS modulation method, and a wireless transmission unit that transmits a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal, wherein the broadcast signal is a PBCH (Physical Broadcast Channel) signal. The base station device further comprises a radio receiving unit that receives a RACH (Random Access Channel) signal transmitted from a terminal using radio resources used for OFDM modulation or OTFS modulation, which are notified to the terminal by the aforementioned PBCH signal. One aspect of the present invention is a base station device further comprising a determination unit that determines the movement status of the transmitting terminal based on the RACH signal received by the wireless receiving unit. One aspect of the present invention is a base station device in which the determination unit determines that the movement status of the transmitting terminal is slow when the RACH signal received by the wireless receiver is in OFDM modulation mode, and determines that the movement status of the transmitting terminal is fast when the RACH signal received by the wireless receiver is in OTFS modulation mode. One aspect of the present invention is a base station device further comprising a communication control unit that performs data communication using the OFDM modulation scheme for terminals determined to be moving at a low speed, and performs data communication using the OTFS modulation scheme for terminals determined to be moving at a high speed. 【0008】 One aspect of the present invention is a communication method performed by a base station device, comprising: a signal processing step of converting a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, and converting the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using an OTFS (Orthogonal Time Frequency Space) modulation scheme; and a wireless transmission step of transmitting a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal. A wireless reception step of receiving a terminal transmission signal in OFDM modulation or OTFS modulation scheme transmitted from a terminal that has received the OFDM modulation signal or OTFS modulation signal converted from the broadcast signal; and a determination step of determining the movement status of the transmitting terminal based on the terminal transmission signal received by the wireless reception step. This is a communication method that includes [something]. One aspect of the present invention is a communication method performed by a base station device, comprising: a signal processing step of converting a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using an OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, and converting the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using an OTFS (Orthogonal Time Frequency Space) modulation scheme; and a wireless transmission step of transmitting a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal, wherein the broadcast signal is a PBCH (Physical Broadcast Channel) signal, and further comprising a wireless reception step of receiving a RACH (Random Access Channel) signal transmitted from a terminal using wireless resources used for the OFDM modulation scheme or wireless resources used for the OTFS modulation scheme that are notified to the terminal by the PBCH signal. 【0009】 One aspect of the present invention provides a signal processing step in which a computer in a base station device converts a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using the OFDM modulation scheme, and converts the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS modulation scheme, and transmits a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal. A wireless reception step of receiving a terminal transmission signal in OFDM modulation or OTFS modulation scheme transmitted from a terminal that has received the OFDM modulation signal or OTFS modulation signal converted from the broadcast signal; and a determination step of determining the movement status of the transmitting terminal based on the terminal transmission signal received by the wireless reception step. It is a computer program designed to execute [something]. One aspect of the present invention is a computer program that causes a base station device's computer to perform a signal processing step of converting a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using the OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, and converting the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS (Orthogonal Time Frequency Space) modulation scheme, and 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, wherein the broadcast signal is a PBCH (Physical Broadcast Channel) signal, and the computer further performs a wireless reception step of receiving a RACH (Random Access Channel) signal transmitted from a terminal using wireless resources used for the OFDM modulation scheme or wireless resources used for the OTFS modulation scheme that are notified to the terminal by the PBCH signal. [Effects of the Invention] 【0010】 According to the present invention, in a communication system that supports both OFDM modulation and OTFS modulation, the effect is obtained that the modulation method can be appropriately switched depending on the situation. [Brief explanation of the drawing] 【0011】 [Figure 1] This block diagram shows a schematic configuration example of a base station device according to one embodiment. [Figure 2] This flowchart shows an example of the procedure for a communication method according to one embodiment. [Figure 3] This is a sequence chart between a base station (gNB) and a terminal (UE) showing an example of the procedure of a communication method according to an embodiment. [Figure 4] This is a diagram showing an example of a multiplexing method for an OFDM modulation signal and an OTFS modulation signal according to an embodiment. [Figure 5] This is a diagram showing an example of a multiplexing method for an OFDM modulation signal and an OTFS modulation signal according to an embodiment. [Figure 6] This is a diagram showing an example of a multiplexing method for an OFDM modulation signal and an OTFS modulation signal according to an embodiment. 【Embodiments for Carrying out the Invention】 【0012】 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration example of a base station apparatus according to an embodiment. The base station apparatus 1 may be, for example, a base station (gNB) of a mobile communication system such as a 5G system, or may be an access point (AP) of a wireless LAN system or the like. Hereinafter, as an example of the base station apparatus 1 according to the present embodiment, a base station (gNB) of a mobile communication system such as a 5G system will be described. 【0013】 In FIG. 1, the base station apparatus 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 apparatus 1 may be realized by dedicated hardware, or may be composed of a CPU (Central Processing Unit) and a memory or the like, and the CPU executes a computer program for realizing the functions of each part to realize the functions. 【0015】 The transmission signal A to be transmitted to the terminal (UE) is input to the signal processing unit 10. The transmission signal A is, for example, a broadcast signal that broadcasts to the terminal. The transmission signal A is, for example, a PBCH (Physical Broadcast Channel) signal. The PBCH signal is a broadcast signal that broadcasts to the terminal. 【0016】 The signal processing unit 10 includes a sub-carrier 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) addition unit 105, and a scheduler 106. 【0017】 The sub-carrier mapping unit 101 maps the transmission signal A to sub-carriers. The scheduler 106 instructs the sub-carrier mapping unit 101 as to which sub-carriers the transmission signal A is to be mapped to. 【0018】 The ISFFT unit 102 performs an ISFFT on the transmission signal A mapped to sub-carriers. 【0019】 The multiplexing unit 103 multiplexes the transmission signal A mapped to sub-carriers and the ISFFT'ed 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 obtained by multiplexing the transmitted signal A mapped to the subcarrier and the transmitted signal A after ISFFT. By performing IDFT on the transmitted signal A mapped to the subcarrier, a signal with OFDM (orthogonal frequency division multiplexing) modulation scheme (the OFDM modulated signal of transmitted signal A) is generated. By performing IDFT on the transmitted signal A after ISFFT, a signal with OTFS (orthogonal time-frequency space) modulation scheme (the OTFS modulated signal of transmitted signal A) is generated. 【0021】 The CP addition unit 105 adds CP to the IDFT output signal output from the IDFT unit 104. The IDFT output signal is a signal that includes the OFDM modulated signal of the transmitted signal A and the OTFS modulated signal of the transmitted signal A. 【0022】 The wireless unit 20 wirelessly transmits the CP-equipped IDFT output signal B, which has a CP added to it, via the antenna 30. As a result, the CP-equipped IDFT output signal B, which includes the OFDM modulated signal of the transmitted signal A and the OTFS modulated signal of the transmitted signal A, is wirelessly transmitted. The CP-equipped 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 OFDM modulation or OTFS modulation scheme transmitted from a terminal that has received a CP-equipped IDFT output signal B wirelessly transmitted from the base station device 1. 【0024】 The determination unit 40 determines the movement status of the transmitting terminal based on the terminal transmission signal C received by the wireless unit 20. As an example of the movement status determination method according to this embodiment, the determination unit 40 determines that the movement status of the transmitting terminal is slow if the terminal transmission signal C received by the wireless unit 20 is in the OFDM modulation scheme. Note that slow speed includes being stationary. On the other hand, the determination unit 40 determines that the movement status of the transmitting terminal is high speed if the terminal transmission signal C received by the wireless unit 20 is in the OTFS modulation scheme. 【0025】 The communication control unit 50 performs data communication using the OFDM modulation method for terminals that are determined to be moving at a low speed. On the other hand, the communication control unit 50 performs data communication using the OTFS modulation method for terminals that are determined to be moving at a 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 Figures 2 and 3. Figure 2 is a flowchart showing an example of the procedure of the communication method according to this embodiment. Here, the PBCH signal is used as an example of the transmission signal A. 【0027】 (Step S1) The base station device 1 periodically transmits wirelessly a CP-equipped IDFT output signal B (OFDM-PBCH and OTFS-PBCH multiplexed signal) which includes the OFDM modulated signal of the PBCH signal and the OTFS modulated signal of the PBCH signal. Here, the PBCH signal has information about the RACH (Random Access Channel), which is a common uplink channel. The RACH information includes OFDM resource designation information that specifies the wireless resources to be used for the OFDM modulation scheme and OTFS resource designation information that specifies the wireless resources to be used for the OTFS modulation scheme. Furthermore, from the standpoint of correctly detecting RACH, it is preferable to operate in such a way that the RACH of the OFDM modulation method and the RACH of the OTFS modulation method do not interfere with each other, by setting the radio resources for the RACH used in the OFDM modulation method and the radio resources for the RACH used in the OTFS modulation method to different time-frequency resources. In this case, the RACH information of the PBCH signal included in the OFDM modulation signal and the RACH information of the PBCH signal included in the OTFS modulation signal may be common information having both OFDM resource specification information and OTFS resource specification information, or they may be separate information having only the respective resource specification information (OFDM modulation signal having only OFDM resource specification information, and OTFS modulation signal having only OTFS resource specification information). 【0028】 A terminal that receives a CP-equipped IDFT output signal B transmitted wirelessly from base station device 1 acquires the PBCH signal by successfully demodulating either the OFDM modulated signal or the OTFS modulated signal of 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 signal of the PBCH signal, it transmits an uplink signal using the OFDM modulation scheme with the radio resources specified in the OFDM resource designation information. 【0030】 On the other hand, if the demodulation of the OFDM-modulated PBCH signal fails, but the demodulation of the OTFS-modulated PBCH signal succeeds, the terminal will transmit an uplink signal using the OTFS modulation scheme with the radio resources specified in the OTFS resource designation information. A terminal that successfully demodulates the OTFS-modulated signal when the OFDM-modulated signal fails is considered to be a terminal moving at high speed. As an example of a method for determining demodulation success, the CRC (Cyclic Redundancy Check) included in the PBCH may be used. Alternatively, the terminal may perform a CRC check for each of the multiple received IDFT output signals B with CP, and determine whether or not the demodulation of the OFDM-modulated PBCH was successful based on the results of these multiple checks. 【0031】 (Step S2) The base station device 1 receives a RACH (Random Access Channel) signal (terminal transmission signal C) in OFDM modulation or OTFS modulation transmitted from a terminal that has received the IDFT output signal B with CP wirelessly transmitted from the base station device 1. The base station device 1 determines whether or not it has detected (received) an OFDM-modulated RACH signal (OFDM-RACH signal). 【0032】 If the base station device 1 determines that it has detected (received) an OFDM-modulated RACH signal (step S2, YES), it records that the transmitting terminal is moving at a low speed and is a terminal that transmits an uplink signal using OFDM modulation. After this, the device proceeds to step S4. 【0033】 On the other hand, if it is determined that the OFDM-modulated RACH signal 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) an OTFS-modulated RACH signal (OTFS-RACH signal). 【0035】 If it is determined that a RACH signal using the OTFS modulation method has been detected (received) (step S3, YES), the base station device 1 records that the transmitting terminal is in a high-speed mobile state and is a terminal that transmits an uplink signal using the OTFS modulation method. After this, the device proceeds to step S6. 【0036】 On the other hand, if it is determined that the RACH signal in OTFS modulation has not been detected (received) (step S3, NO), the process returns to step S2. 【0037】 (Step S4) The base station device 1 uses OFDM modulation to complete initial access with the terminal in question according to a predetermined random access procedure. 【0038】 (Step S5) The base station device 1 performs data communication with a terminal whose movement status is determined to be low speed by the OFDM modulation method using an OFDM modulated signal. 【0039】 (Step S6) The base station device 1 uses the OTFS modulation scheme to complete the initial access with the terminal in question according to a predetermined random access procedure. 【0040】 (Step S7) The base station device 1 performs data communication with the terminal that has been determined to be moving at high speed using the OTFS modulation method, using the OTFS modulation method. 【0041】 Furthermore, the base station device 1 may monitor changes in the modulation scheme used by the terminal (changes between OFDM modulation and OTFS modulation), determine an increase or decrease in the terminal's movement speed based on the monitoring results, and record the determination result of the increase or decrease in the terminal's movement speed. If the modulation scheme is changed from OFDM to OTFS, the determination unit 40 determines that the terminal's movement speed has increased. On the other hand, if the modulation scheme is changed from OTFS to OFDM, the determination unit 40 determines that the terminal's movement speed has decreased. 【0042】 Alternatively, a threshold value for the terminal's movement speed when changing from OFDM modulation to OTFS modulation may be set in advance in the determination unit 40, and the determination unit 40 may estimate the terminal's movement speed based on that threshold value. 【0043】 Figure 3 is a sequence chart between a base station (gNB) and a terminal (UE) showing an example of the communication method according to this embodiment. Here, the PBCH signal is used as an example of the transmission signal A. 【0044】 (Step S101) The base station (gNB) periodically transmits wirelessly a CP-equipped IDFT output signal B (a multiplexed signal of OFDM-PBCH and OTFS-PBCH) which includes an OFDM-modulated signal of the PBCH signal and an OTFS-modulated signal of the PBCH signal. 【0045】 The terminal (UE) receives the IDFT output signal B with CP wirelessly transmitted from the base station device 1. Upon receiving the IDFT output signal B with CP, the terminal (UE) acquires the PBCH signal by successfully demodulating either the OFDM modulated signal or the OTFS modulated signal of 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. 【0046】 (Step S102) If the terminal (UE) successfully demodulates the OFDM modulated signal of the PBCH signal, it transmits a RACH signal (OFDM-RACH signal) using the OFDM modulation scheme with the radio resources specified in the OFDM resource designation information. 【0047】 On the other hand, if the demodulation of the OFDM-modulated PBCH signal fails, the terminal (UE) will transmit a RACH signal (OTFS-RACH signal) using the OTFS modulation scheme with the radio resources specified in the OTFS resource designation information, if the demodulation of the OTFS-modulated PBCH signal is successful. 【0048】 The base station (gNB) detects (receives) a RACH signal from the terminal (UE) using either OFDM modulation or OTFS modulation. 【0049】 The base station (gNB) uses the PBCH signal to specify the radio resources that the terminal (UE) uses for OFDM modulation and the radio resources that it uses for OTFS modulation, using separate radio resources. This allows the base station (gNB) to determine whether the transmitting terminal (UE) is using OFDM modulation (a terminal with a low-speed mobile state) or OTFS modulation (a terminal with a high-speed mobile state) by detecting the radio resources used in the RACH signal transmitted from the terminal (UE). 【0050】 When a base station (gNB) detects (receives) a RACH signal from a terminal (UE) using OFDM modulation on a specified resource via a PBCH, it records that the transmitting terminal (UE) is in a slow mobile state and will use OFDM modulation in subsequent communications. On the other hand, when a base station (gNB) detects (receives) a RACH signal from a terminal (UE) using OTFS modulation on a specified resource via a PBCH, it records that the transmitting terminal (UE) is in a high mobile state and will transmit signals using OTFS modulation in subsequent communications. 【0051】 (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 scheme. 【0052】 On the other hand, if the demodulation of the OFDM-modulated PBCH signal fails, the terminal (UE) will complete a predetermined initial access procedure using the OTFS modulation scheme if the demodulation of the PBCH signal using the OFDM-modulated PBCH signal is successful. 【0053】 (Step S104) The base station (gNB) communicates data with terminals that are determined to be moving at a low speed using OFDM modulation signals. On the other hand, the base station (gNB) communicates data with terminals that are determined to be moving at a high speed using OTFS modulation. 【0054】 Next, the multiplexing method for OFDM-modulated signals and OTFS-modulated signals according to this embodiment will be described. Figure 4-6 shows an example of the multiplexing method for OFDM-modulated signals and OTFS-modulated signals according to this embodiment. 【0055】 Figure 4(1) shows an example of multiplexing OFDM-modulated signals and OTFS-modulated signals using the TDM method for a PBCH signal. Figure 4(2) shows an example of multiplexing OFDM-modulated signals and OTFS-modulated signals using the FDM method for a PBCH signal. 【0056】 Figure 5(1) shows another example of multiplexing OFDM-modulated and OTFS-modulated signals using the TDM method for a PBCH signal. Figure 5(2) shows another example of multiplexing OFDM-modulated and OTFS-modulated signals using the FDM method for a PBCH signal. 【0057】 Figure 6 shows examples of multiplexing OFDM-modulated signals and OTFS-modulated signals using TDM and FDM methods for a PBCH signal. 【0058】 According to this embodiment, broadcast signals, such as PBCH signals, can be broadcast to terminals using both OFDM modulation and OTFS modulation. As a result, even if the demodulation of the OFDM modulation fails, a terminal moving at high speed can still correctly receive the broadcast signal if the demodulation of the OTFS modulation is successful. Similarly, a terminal moving at low speed can still correctly receive the broadcast signal if the demodulation of the OFDM modulation is successful. Therefore, according to this embodiment, both high-speed and low-speed terminals can correctly receive broadcast signals, such as PBCH signals, thus improving the stability of communication between the base station and the terminal. 【0059】 Furthermore, by receiving the OFDM-modulated or OTFS-modulated terminal transmission signal transmitted from a terminal that received the OFDM-modulated or OTFS-modulated signal converted from the broadcast signal, it is possible to determine whether the transmitting terminal is moving at a low speed or a high speed. This is because a low-speed terminal is expected to successfully demodulate the OFDM-modulated signal, while a high-speed moving terminal is expected to successfully demodulate the OTFS-modulated signal even if the OFDM-modulated signal fails to demodulate. 【0060】 Furthermore, by using OFDM modulation for data communication with terminals determined to be moving at a low speed and OTFS modulation for terminals determined to be moving at a high speed, it is possible to select a modulation method suitable for the terminal's movement state. Using OFDM modulation for terminals moving at a low speed makes it possible to reduce power consumption and processing delays associated with signal processing. 【0061】 Furthermore, this will enable improvements in overall service quality, such as in mobile communication systems, and will contribute to Goal 9 of the United Nations-led Sustainable Development Goals (SDGs): "Build resilient infrastructure, promote sustainable industrialization and foster innovation." 【0062】 Although embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and design modifications and the like are also included within the scope of the gist of the present invention. 【0063】 Alternatively, computer programs for realizing the functions of each of the above-mentioned devices may be recorded on a computer-readable recording medium, and the programs recorded on this recording medium may be loaded into a computer system and executed. Note that the term "computer system" here may include hardware such as an operating system and peripheral devices. Furthermore, "computer-readable recording media" refers to writable non-volatile memory such as flexible disks, magneto-optical disks, ROMs, and flash memory, portable media such as DVDs (Digital Versatile Discs), and storage devices such as hard disks built into computer systems. 【0064】 Furthermore, "computer-readable recording media" also includes volatile memory (such as DRAM (Dynamic Random Access Memory)) within computer systems that act as servers or clients when programs are transmitted via networks such as the Internet or communication lines such as telephone lines, which retain programs for a certain period of time. Furthermore, the above program may be transmitted from a computer system that stores the program in a memory device or the like to another computer system via a transmission medium or by transmission waves within the transmission medium. Here, the "transmission medium" used to transmit the program refers to a medium that has the function of transmitting information, such as a network (communication network) like the Internet or a communication line (communication line) like a telephone line. Furthermore, the above program may be intended to implement some of the functions described above. It may also be a so-called differential file (differential program) that can implement the aforementioned functions in combination with programs already recorded in the computer system. [Explanation of symbols] 【0065】 1...Base station equipment, 10...Signal processing unit, 20...Wireless 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 addition unit, 106...Scheduler

Claims

[Claim 1] A signal processing unit that converts a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using the OFDM modulation method, and converts the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS modulation method, A wireless transmission unit transmits a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal, A wireless receiving unit that receives a terminal transmission signal in OFDM modulation or OTFS modulation transmitted from a terminal that has received the OFDM modulation signal or OTFS modulation signal converted from the broadcast signal, A determination unit determines the movement status of the transmitting terminal based on the terminal transmission signal received by the wireless receiving unit, A base station device equipped with the following features. [Claim 2] The determination unit, If the resource of the terminal transmission signal received by the wireless receiver is the resource specified in the broadcast signal transmitted using OFDM modulation, the wireless receiver determines that the transmitting terminal is moving at a low speed. The wireless receiver determines that the source terminal is moving at high speed if the resource of the terminal transmission signal received by the wireless receiver is the resource specified by the broadcast signal transmitted using the OTFS modulation method. The base station device according to claim 1. [Claim 3] The determination unit, When the terminal transmission signal received by the wireless receiver is in OFDM modulation, it is determined that the transmitting terminal is moving at a low speed. When the terminal transmission signal received by the wireless receiver is in OTFS modulation mode, it is determined that the transmitting terminal is moving at high speed. The base station device according to claim 1. [Claim 4] A communication control unit that performs data communication using OFDM modulation for terminals determined to be moving at a low speed, and uses OTFS modulation for terminals determined to be moving at a high speed. The base station device according to claim 3, further comprising: [Claim 5] A signal processing unit that converts a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using the OFDM (Orthogonal Frequency Division Multiplexing) modulation scheme, and converts the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS (Orthogonal Time Frequency Space) modulation scheme, A wireless transmission unit transmits a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal, Equipped with, The aforementioned broadcast signal is a PBCH (Physical Broadcast Channel) signal, A wireless receiver unit that receives a RACH (Random Access Channel) signal transmitted from a terminal using wireless resources used for OFDM modulation or OTFS modulation, which are notified to the terminal by the PBCH signal. A base station device further equipped with these features. [Claim 6] A determination unit determines the movement status of the transmitting terminal based on the RACH signal received by the wireless receiving unit. The base station device according to claim 5, further comprising: [Claim 7] The determination unit, If the RACH signal received by the wireless receiver is in OFDM modulation mode, it is determined that the transmitting terminal is moving at a low speed. The wireless receiver determines that the transmitting terminal is moving at high speed when the RACH signal received by the wireless receiver is in OTFS modulation mode. The base station device according to claim 6. [Claim 8] A communication control unit that performs data communication using OFDM modulation for terminals determined to be moving at a low speed, and uses OTFS modulation for terminals determined to be moving at a high speed. The base station device according to claim 7, further comprising: [Claim 9] A communication method performed by a base station device, A signal processing step which involves converting a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using the OFDM modulation method, and then converting the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS modulation method, A wireless transmission step of transmitting a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal, A wireless reception step of receiving a terminal transmission signal in OFDM modulation or OTFS modulation transmitted from a terminal that has received the OFDM modulation signal or OTFS modulation signal converted from the broadcast signal, A determination step which determines the movement status of the transmitting terminal based on the terminal transmission signal received in the wireless reception step, A communication method that includes this. [Claim 10] A communication method performed by a base station device, A signal processing step which involves converting a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using the OFDM modulation method, and then converting the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS modulation method, A wireless transmission step of transmitting a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal, Includes, The aforementioned broadcast signal is a PBCH (Physical Broadcast Channel) signal, A wireless reception step of receiving a RACH (Random Access Channel) signal transmitted from a terminal using wireless resources used for OFDM modulation scheme or OTFS modulation scheme, which are notified to the terminal by the PBCH signal. A communication method that further includes this. [Claim 11] In the base station equipment computer, A signal processing step which involves converting a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using the OFDM modulation method, and then converting the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS modulation method, A wireless transmission step of transmitting a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal, A wireless reception step of receiving a terminal transmission signal in OFDM modulation or OTFS modulation transmitted from a terminal that has received the OFDM modulation signal or OTFS modulation signal converted from the broadcast signal, A determination step which determines the movement status of the transmitting terminal based on the terminal transmission signal received in the wireless reception step, A computer program designed to execute something. [Claim 12] The computer of the base station device, A signal processing step which involves converting a broadcast signal to be broadcast to a terminal into an OFDM (Orthogonal Frequency Division Multiplexing) modulated signal using the OFDM modulation method, and then converting the broadcast signal to be broadcast to the terminal into an OTFS (Orthogonal Time Frequency Space) modulated signal using the OTFS modulation method, A wireless transmission step of transmitting a multiplexed signal obtained by multiplexing the OFDM modulated signal and the OTFS modulated signal converted from the broadcast signal, Make it run, The aforementioned broadcast signal is a PBCH (Physical Broadcast Channel) signal, A wireless reception step of receiving a RACH (Random Access Channel) signal transmitted from a terminal using wireless resources used for OFDM modulation scheme or OTFS modulation scheme, which are notified to the terminal by the PBCH signal. A computer program to perform further actions.

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