Base station and communication method

Abstract

To provide a base station and a communication method that enable stable communication with a moving terminal in wireless communication using a milliwave band.SOLUTION: A base station comprises: a control section that determines a linkage scheme of a plurality of wireless stations for signal transmission and the number of streams at each of the wireless stations on the basis of information updated in line with the movement of a terminal; and a transmission section that causes the plurality of wireless stations to link to each other according to the determined linkage scheme and transmits a signal to the terminal using the streams.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a base station and a communication method.

Background Art

[0002] In 5G (5th generation mobile communication system), massive MIMO (Massive Multiple Input Multiple Output) using multi-element antennas is one of the main technologies. For example, in massive MIMO, a sharp beam is generated by beamforming to achieve high-speed and high-capacity communication (see, for example, Patent Document 1). Also, in massive MIMO, high-speed and high-capacity communication is achieved by multiplexing transmission for a plurality of users or a plurality of streams.

[0003] In a future smoke-free communication system, in order to achieve further high-speed and high-capacity communication, the use of the millimeter wave band that can be broadened is under consideration. For example, since the millimeter wave band has a larger path loss and a shorter transmission distance than sub-6, the communication area is narrow, and communication between a base station and a moving terminal may become unstable. Therefore, a technique in which a plurality of radio stations cooperate to communicate with a terminal is under consideration.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the study of the technique in which a plurality of radio stations cooperate to communicate with a terminal in the millimeter wave band is insufficient, and further study is required.

[0006] One aspect of the present disclosure is to cooperate a plurality of radio stations to perform stable communication with a terminal in the millimeter wave band.

Means for Solving the Problem

[0007] A base station according to an aspect of the present disclosure includes a control unit that determines a cooperation method in signal transmission of a plurality of radio stations and the number of streams in each of the radio stations based on information that appears due to the movement of a terminal, and a transmission unit that cooperates the plurality of radio stations according to the cooperation method and transmits a signal to the terminal using the streams.

[0008] A communication method according to an aspect of the present disclosure is such that a base station determines a cooperation method in signal transmission of a plurality of radio stations and the number of streams in each of the radio stations based on information that appears due to the movement of a terminal, cooperates the plurality of radio stations according to the cooperation method, and transmits a signal to the terminal using the streams.

Advantages of the Invention

[0009] According to the present disclosure, a base station can cooperate a plurality of radio stations and perform stable millimeter-wave band communication with a terminal.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 7

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments according to one aspect of the present disclosure will be described with reference to the drawings.

[0012] FIG. 1 is a diagram showing a configuration example of a wireless communication system according to an embodiment of the present disclosure. As shown in FIG. 1, the wireless communication system includes a CU1, a DU2, wireless stations 3a and 3b, and a terminal 4a. Note that CU is an abbreviation for Centralized Unit. DU is an abbreviation for Distributed Unit.

[0013] The CU1 has, for example, an RRC layer, an SDAP layer, and a PDCP layer. RRC is an abbreviation for Radio Resource Control. SDAP is an abbreviation for Service Data Adaptation Protocol. PDCP is an abbreviation for Packet Data Convergence Protocol.

[0014] The DU2 has, for example, an RLC layer, a MAC layer, and a PHY-High layer. RLC is an abbreviation for Radio Link Control. MAC is an abbreviation for Medium Access Control. PHY is an abbreviation for physical.

[0015] The wireless stations 3a and 3b have, for example, a PHY-Low&RF layer. RF is an abbreviation for Radio Frequency.

[0016] CU1 is connected to a core network (not shown) and DU2. CU1 processes the signals received from the core network based on the above layer functions and transmits them to DU2. Also, CU1 processes the signals received from DU2 based on the above layer functions and transmits them to the core network.

[0017] DU2 is connected to CU1 and radio stations 3a, 3b. DU2 processes the signals received from CU1 based on the above layer functions and transmits them to radio stations 3a, 3b. Also, DU2 processes the signals received from radio stations 3a, 3b based on the above layer functions and transmits them to CU1.

[0018] Radio stations 3a, 3b are connected to DU2. Also, radio stations 3a, 3b perform wireless communication with terminal 4a using the millimeter wave band. Radio stations 3a, 3b process the signals received from DU2 based on the above layer functions and transmit them to terminal 4a. Also, radio stations 3a, 3b process the signals received from terminal 4a based on the above layer functions and transmit them to DU1.

[0019] Note that the configuration example of the wireless communication system is not limited to the example in FIG. 1. For example, one radio station may be connected to DU2, or three or more radio stations may be connected to DU2.

[0020] Also, one DU may be connected to each of radio stations 3a, 3b. The DU connected to radio station 3a and the DU connected to radio station 3b may be connected to CU1.

[0021] Also, radio stations 3a, 3b may be cascade-connected. For example, radio station 3a may be connected to DU2, and radio station 3b may be connected to radio station 3a.

[0022] CU1 and DU2 may also be referred to as a base station or gNB. Also, CU1, DU2, and radio stations 3a, 3b may be referred to as base stations. The radio station may be referred to as an RU (Radio Unit), a remote radio unit, a transmission point, or an antenna panel.

[0023] Figures 2A, 2B, and 2C are diagrams for explaining an example of the cooperation method of radio stations 3a and 3b. In Figures 2A, 2B, and 2C, the same components as those in Figure 1 are denoted by the same reference numerals.

[0024] As a cooperation method (cooperation technique) of radio stations 3a and 3b that enables stable high-speed and high-capacity communication for a terminal 4a moving at high speed, for example, there are the following three cooperation methods.

[0025] A1. Cooperative transmission based on a plurality of radio stations 3a and 3b For example, as shown in Figure 2A, radio stations 3a and 3b transmit signals to terminal 4a using stream #0. That is, radio stations 3a and 3b transmit the same signal to terminal 4a. Note that the cooperative transmission may also be referred to as simultaneous transmission, cooperative MIMO, or joint transmission.

[0026] A2. Distributed MIMO based on a plurality of radio stations 3a and 3b For example, as shown in Figure 2B, radio station 3a transmits a signal to terminal 4a using stream #0. Radio station 3b transmits a signal to terminal 4a using stream #1. That is, radio stations 3a and 3b transmit different signals to terminal 4a. Note that the distributed MIMO may also be referred to as distributed transmission or distributed sending.

[0027] A3. Communication switching based on a plurality of radio stations 3a and 3b For example, as shown in Figure 2C, radio stations 3a and 3b seamlessly switch streams #0 and #1 in accordance with the movement of terminal 4a and transmit signals to terminal 4a. For example, radio station 3a stops transmitting a signal using stream #0 in accordance with the movement of terminal 4a, and radio station 3b starts transmitting a signal using stream #1.

[0028] Regarding the cooperation of the above-described radio stations 3a and 3b, there is room for consideration in determining the streams in each of radio stations 3a and 3b for a moving terminal 4a.

[0029] The base station of the present disclosure determines the cooperation method in the signal transmission of the radio stations 3a and 3b and the number of streams in each of the radio stations 3a and 3b based on the information that appears when the terminal 4a moves.

[0030] Note that the base station that determines the cooperation method and the number of streams may be the CU1 or the DU2. Also, the base station that determines the number of streams may be the CU1 and the DU2. Further, the "information" that appears when the terminal 4a moves may be rephrased as a signal, a parameter, or an element.

[0031] FIG. 3 is a diagram showing an example of the functional block configuration of a base station. As shown in FIG. 3, the base station 10 includes a control unit 11 and a communication unit 12.

[0032] The control unit 11 determines the cooperation method in the signal transmission of the radio stations 3a and 3b and the number of streams in each of the radio stations 3a and 3b based on the information that appears due to the movement of the terminal 4a. As will be described later, the information that appears due to the movement of the terminal 4a may be, for example, the spread of the Doppler spectrum or the fluctuation of the received power of the received signal in the base station 10 or the terminal 4a.

[0033] Further, the control unit 11 controls the phase rotation of the signal transmitted using the stream based on the amount of phase rotation of the received signal in the terminal 4a or the channel quality between the terminal 4a.

[0034] Also, the control unit 11 determines the cooperation method and the number of streams in the retransmission signal to the terminal 4a based on the information that appears due to the movement of the terminal 4a.

[0035] The communication unit 12 performs wireless communication with the terminal 4a using the millimeter wave band. The communication unit 12 cooperates the radio stations 3a and 3b according to the cooperation method determined by the control unit 11, and transmits a signal to the terminal 4a using the number of streams determined by the control unit 11 in each of the radio stations 3a and 3b.

[0036] <Regarding the method for determining the cooperation method and the number of streams> When the terminal 4a moves, the base station 10 determines the cooperation method and the number of streams of the radio stations 3a and 3b based on the following information that appears.

[0037] B1. Spread of Doppler spectrum When the terminal 4a moves, the Doppler spectrum spreads. For example, it can be understood that the faster the Doppler spectrum spreads, the faster the moving speed of the terminal 4a and the faster the channel variation. When the channel variation is fast, it may be difficult to separate the received signals at the terminal 4a.

[0038] Therefore, if the Doppler spectrum is wide, reducing the number of streams of the signals transmitted by the radio stations 3a and 3b may suppress the decrease in communication speed. Also, for the cooperation of the radio stations 3a and 3b, switching between the radio stations 3a and 3b is better than coordinated transmission and distributed MIMO.

[0039] For example, when the spread of the Doppler spectrum is equal to or greater than the threshold, the base station 10 determines that the terminal 4a is moving at high speed, does not perform coordinated transmission and distributed MIMO, and sets the number of streams of the signal transmitted to the terminal 4a to 1.

[0040] Note that the base station 10 may transmit a reference signal to the terminal 4a, and the terminal 4a may measure the spread of the Doppler spectrum of the reference signal. Then, the terminal 4a may feedback the measured spread of the Doppler spectrum to the base station 10. For example, DMRS (DeModulation Reference Signals) may be used as the reference signal.

[0041] Also, the terminal 4a may transmit a reference signal to the base station 10, and the base station 10 may measure the spread of the Doppler spectrum of the reference signal.

[0042] Further, the base station 10 may change the number of streams according to the spread of the Doppler spectrum of the signal. For example, the base station 10 may decrease the number of streams as the Doppler spectrum spreads. When the determined number of streams is equal to or greater than a threshold value, the base station 10 may perform either or both of cooperative transmission and distributed MIMO.

[0043] B2. Variation in received power B2-1. When the terminal 4a moves, the received power fluctuates. For example, when the received power of a signal (e.g., a reference signal) received from the terminal 4a by the radio station 3a decreases, the terminal 4a can be considered to be moving away from the radio station 3a. In other words, the terminal 4a can be considered to be moving towards the cell edge of the radio station 3a. The received power may be, for example, RSRP (Reference Signal Received Power).

[0044] Therefore, when the base station 10 determines that the terminal 4a is moving towards the cell edge of the radio station 3a based on the variation in the received power of the signal received by the radio station 3a from the terminal 4a, the base station 10 decreases the number of streams and concentrates the power of the signal transmitted to the terminal 4a.

[0045] In addition, the base station 10 applies cooperative transmission based on the radio station 3a and the radio station 3b in order to improve the received power of the terminal 4a at the cell edge.

[0046] In addition, if the moving speed of the terminal 4a is high, the base station 10 performs predictive (early) switching processing with the adjacent radio station 3b. That is, the base station 10 controls the timing of communication switching with the adjacent radio station 3b according to the moving speed of the terminal 4a.

[0047] B2-2. When the received powers of the signals of the terminal 4a received by the radio station 3a and the radio station 3b are equal, it can be considered that the communication quality between the radio station 3a and the terminal 4a and the communication quality between the radio station 3b and the terminal 4a are equal.

[0048] For example, when the difference between the received power of the signal of terminal 4a received by radio station 3a and the received power of the signal of terminal 4a received by radio station 3b is equal to or less than a threshold value, the communication quality between radio station 3a and terminal 4a and the communication quality between radio station 3b and terminal 4a can be regarded as equivalent.

[0049] Therefore, when the communication quality between radio station 3a and terminal 4a and the communication quality between radio station 3b and terminal 4a are equivalent, it is expected that the line of sight (LOS) between radio station 3a and terminal 4a and the LOS between radio station 3a and terminal 4a are established, and base station 10 transmits a signal to terminal 4a using a plurality of streams based on distributed MIMO.

[0050] That is, when base station 10 determines that the communication quality between radio station 3a and terminal 4a and the communication quality between radio station 3b and terminal 4a are equivalent (for example, the difference in communication quality is equal to or less than a threshold value), base station 10 transmits a signal to terminal 4a using a plurality of streams based on distributed MIMO.

[0051] Note that base station 10 may transmit a reference signal to terminal 4a, and terminal 4a may measure the received power of the reference signal. Then, terminal 4a may feedback the measured received power to base station 10.

[0052] In addition, base station 10 may independently execute control based on the above-mentioned "Doppler spectrum spread" and "received power fluctuation", or execute them in combination. In addition, base station 10 may perform the same control not only in a single-user environment but also in a multi-user environment.

[0053] <Regarding improvement of communication quality based on base station function and terminal function> In addition to determining the cooperation method and the number of streams in radio stations 3a and 3b, base station 10 may improve the communication quality of fast-moving terminal 4a by using the following functions of base station 10 and terminal 4a.

[0054] C1. AFC function of base station 10 When the base station 10 has an AFC function, it removes the phase rotation of the signal due to the Doppler shift of the LOS component on the base station 10 side. For example, the base station 10 applies a phase rotation to the signal in advance on the base station 10 side so that the signal received by the terminal 4a has a phase rotation of 0 at the terminal 4a. AFC is the abbreviation of Automatic Frequency Control.

[0055] C2. Channel Tracking Function of Base Station 10 When the base station 10 has a channel tracking function, it removes the phase rotation of the signal of the NLOS (Non Line Of Sight) component on the base station 10 side. For example, the base station 10 applies a phase rotation to the signal in advance on the base station 10 side so that the signal received by the terminal 4a has a phase rotation of 0 at the terminal 4a. Note that the channel tracking function refers to, for example, a function of monitoring the channel (instant by instant) to calculate the precoding matrix and applying the precoding matrix to the transmission signal.

[0056] C3. AFC Function of Terminal When the terminal 4a has an AFC function, it removes the phase rotation of the signal due to the Doppler shift of the LOS component on the terminal 4a side. If the frequency of removing the phase rotation by the terminal 4a is high, the number of OFDM (Orthogonal Frequency Division Multiplexing) symbols affected by the phase rotation can be reduced.

[0057] Note that when the base station 10 has both an AFC function and a channel tracking function, even if the terminal 4a does not have an AFC function, high-quality communication can be achieved between the base station 10 and the terminal 4a. The communication quality between the base station 10 and the terminal 4a is less affected (less dependent) by whether the terminal 4a has an AFC function or not.

[0058] In addition, when the base station 10 has either the AFC function or the channel tracking function, the communication quality with the terminal 4a deteriorates compared to the case where the base station 10 has both the AFC function and the channel tracking function. The communication quality between the base station 10 and the terminal 4a depends on the presence or absence of the AFC function of the terminal 4a compared to the case where the base station 10 has the AFC function and the channel tracking function.

[0059] Also, when the base station 10 does not have the AFC function and the channel tracking function, the communication quality between the base station 10 and the terminal 4a depends on whether the terminal 4a has the AFC function.

[0060] <Regarding the retransmission signal> The base station 10 may control the cooperation method and the number of streams of the radio stations 3a and 3b in the retransmission signal.

[0061] D1. Retransmission control in cooperative transmission The base station 10 determines the cooperation method and the number of streams of the radio stations 3a and 3b in the retransmission signal based on the information that appears when the terminal 4a moves. For example, when retransmission of a signal occurs, the base station 10 determines the stream for transmitting the retransmission signal to be a stream different from the stream for transmitting the signal based on the information that appears when the terminal 4a moves.

[0062] FIG. 4 is a diagram for explaining an example of stream control of a retransmission signal. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals.

[0063] As shown in FIG. 4, the base station 10 transmits a signal to the terminal 4a in stream #0 by cooperative transmission using the radio stations 3a and 3b.

[0064] Here, it is assumed that the terminal 4a moves away from the radio station 3a and approaches the radio station 3b as shown by the arrow A1 in FIG. 4. It is assumed that the base station 10 determines to retransmit the signal transmitted to the terminal 4a.

[0065] When the base station 10 determines to retransmit a signal, it determines the moving direction of the terminal 4a from the fluctuation of the received power of the signal. For example, when the received power of the signal of the terminal 4a at the radio station 3a decreases and the received power of the signal of the terminal 4a at the radio station 3b increases, the base station 10 determines that the terminal 4a is moving away from the radio station 3a and approaching the radio station 3b.

[0066] When the base station 10 determines the moving direction of the terminal 4a, it determines the stream of the retransmission signal based on the determined moving direction. For example, the base station 10 determines the stream so as to transmit the retransmission signal from the radio station 3b determined to be the moving destination of the terminal 4a. For example, as shown in FIG. 4, the base station 10 transmits a signal to the terminal 4a using the stream #0 of the radio station 3a and transmits a retransmission signal to the terminal 4a using the stream #0 of the radio station 3b.

[0067] D2. Retransmission Control in Distributed MIMO When the base station 10 is performing distributed MIMO, for example, if the signal transmitted at the first radio station (first stream) is in error and the signal transmitted at the second radio station (second stream) is not in error, the base station 10 transmits the retransmission signal at the second radio station.

[0068] FIG. 5 is a diagram for explaining an example of stream control of a retransmission signal. In FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals.

[0069] As shown in FIG. 5, the base station 10 transmits signals to the terminal 4a in streams #0 and #1 by distributed MIMO using the radio stations 3a and 3b.

[0070] Here, it is assumed that an error has occurred in the signal in stream #0. In this case, the base station 10 transmits the retransmission signal to the terminal 4a using the stream #1 of the radio station 3b instead of the stream #0 of the radio station 3a.

[0071] D3. Other Retransmission Controls When the number of retransmission times of the retransmission signal in the first radio station or the first stream reaches or exceeds a threshold value, the base station 10 transmits the retransmission signal from the second radio station or the second stream.

[0072] The base station 10 may combine the cooperation method and the control of the number of streams described in B1 and B2 above, the control based on the functions of the base station 10 and the terminal 4a described in C1, C2, and C3, and the retransmission control described in D1 and D2.

[0073] Hereinafter, the cooperation method and the control of the number of streams described in B1 may be referred to as "Control 1", the stream control described in B2 may be referred to as "Control 2", the control based on the functions described in C1, C2, and C3 may be referred to as "Control 3", and the retransmission control described in D1 and D2 may be referred to as "Control 4".

[0074] FIG. 6A, FIG. 6B, and FIG. 6C are flowcharts showing operation examples of the base station 10. The base station 10 repeatedly executes the processes of the flowcharts shown in FIG. 6A, FIG. 6B, and FIG. 6C, for example. Note that in the flowcharts shown in FIG. 6A, FIG. 6B, and FIG. 6C, the processes are connected at the numbers 1 to 3 shown in the figures.

[0075] The base station 10 determines whether to execute transmission control based on quality prediction (S1). For example, the base station 10 autonomously determines whether to execute transmission control based on quality prediction by AI (Artificial Intelligence). Alternatively, when transmission control based on quality prediction is set by an operator, the base station 10 determines to execute the transmission control. Note that the transmission control based on quality prediction refers to at least one of the above Controls 1 to 4.

[0076] When the base station 10 determines not to execute transmission control in S1 (No in S1), it transmits a signal and a retransmission signal based on the existing transmission control and the existing retransmission control (S10). Then, the base station 10 ends the process of this flowchart.

[0077] On the other hand, when the base station 10 determines to execute transmission control based on quality prediction at S1 (Yes in S1), it determines whether to apply Control 1 to the signal transmission control (S2). For example, when the spread of the Doppler spectrum is equal to or greater than a threshold value, the base station 10 determines to apply Control 1.

[0078] When the base station 10 determines to apply Control 2 to the signal transmission control at S2 (Yes in S2), it determines whether to apply Control 2 to the signal transmission control (S3). For example, the base station 10 determines to apply Control 2 based on the fluctuation of the received power. Specifically, when the received power fluctuates by more than a preset threshold value, the base station 10 determines to apply Control 2.

[0079] When the base station 10 determines to apply Control 3 to the signal transmission control at S3 (Yes in S3), it determines whether to apply Control 3 to the signal transmission control (S4). For example, when the base station 10 has both or one of the AFC function and the channel tracking function, the base station 10 determines to apply Control 3.

[0080] When the base station 10 determines to apply Control 3 at S4 (Yes in S4), it executes transmission control based on Controls 1, 2, and 3 (S5). On the other hand, when the base station 10 determines not to apply Control 3 at S4 (No in S4), it executes transmission control based on Controls 1 and 2 (S6).

[0081] The base station 10 determines whether to apply Control 4 (S7). For example, when signal retransmission occurs, the base station 10 determines to apply Control 4.

[0082] When the base station 10 determines to apply Control 4 at S7 (Yes in S7), it executes retransmission control based on Control 4 (S8). On the other hand, when the base station 10 determines not to apply Control 4 at S7 (No in S7), it ends the processing of this flowchart.

[0083] When the base station 10 determines not to apply Control 1 at S2 (No in S2), as shown in FIG. 6B, it determines whether to apply Control 2 to the signal transmission control (S11). For example, when there is a fluctuation in the received power, the base station 10 determines to apply Control 2.

[0084] When the base station 10 determines to apply Control 2 at S11 (Yes in S11), it determines whether to apply Control 3 to the signal transmission control (S12). For example, when the base station 10 has both or either the AFC function and the channel tracking function, the base station 10 determines to apply Control 3.

[0085] When the base station 10 determines to apply Control 3 at S12 (Yes in S12), it executes the transmission control based on Controls 2 and 3 (S13). On the other hand, when the base station 10 determines not to apply Control 3 at S12 (No in S12), it executes the transmission control based on Control 2 (S14).

[0086] When the base station 10 determines not to apply Control 2 at S11 (No in S11), it determines whether to apply Control 3 to the signal transmission control (S15). For example, when the base station 10 has both or either the AFC function and the channel tracking function, the base station 10 determines to apply Control 3.

[0087] When the base station 10 determines to apply Control 3 at S15 (Yes in S15), it executes the transmission control based on Control 3 (S16). On the other hand, when the base station 10 determines not to apply Control 3 at S15 (No in S16), it executes the existing transmission control (S17).

[0088] When the base station 10 determines not to apply Control 2 at S3 in FIG. 6A (No in S3), as shown in FIG. 6C, it determines whether to apply Control 3 to the signal transmission control (S18). For example, when the base station 10 has both or either the AFC function and the channel tracking function, the base station 10 determines to apply Control 3.

[0089] When the base station 10 determines to apply Control 3 at S18 (Yes in S18), it executes transmission control based on Controls 1 and 3 (S19). On the other hand, when the base station 10 determines not to apply Control 3 at S18 (No in S18), it executes transmission control based on Control 1 (S20).

[0090] As described above, the base station 10 includes a control unit 11 that determines a cooperation method in signal transmission of the radio stations 3a and 3b and the number of streams in each of the radio stations 3a and 3b based on information that appears due to the movement of the terminal 4a, and a communication unit 12 that transmits a signal to the terminal 4a using the determined streams.

[0091] Thereby, the base station 10 can cooperate a plurality of radio stations 3a and 3b and perform stable millimeter-wave band communication with the terminal 4a.

[0092] For example, information that appears due to the movement of the terminal 4a includes a widened Doppler spectrum or a variation in received power. The base station 10 determines a cooperation method in signal transmission of the radio stations 3a and 3b and the number of streams in each of the radio stations 3a and 3b based on the widened Doppler spectrum corresponding to the movement of the terminal 4a or the received power. Thereby, the base station 10 can perform appropriate signal transmission according to the movement of the terminal 4a and perform stable high-speed large-capacity communication with the fast-moving terminal 4a in millimeter-wave band wireless communication.

[0093] The above is the description of the present disclosure.

[0094] <Hardware Configuration, etc.> Note that the block diagrams used in the description of the above embodiments show blocks of functional units. These functional blocks (components) are realized by any combination of at least one of hardware and software. Also, the method of realizing each functional block is not particularly limited. That is, each functional block may be realized using one physically or logically combined device, or may be realized using two or more physically or logically separated devices directly or indirectly (for example, using wired, wireless, etc.) connected, and using these multiple devices. The functional block may be realized by combining software with the above one device or the above multiple devices.

[0095] Functions include, but are not limited to, judgment, decision, determination, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, solution, selection, selection, establishment, comparison, assumption, expectation, regarded as, notification (broadcasting), notification (notifying), communication (communicating), forwarding, configuration (configuring), reconfiguration (reconfiguring), allocation (allocating, mapping), assignment (assigning), etc. For example, a functional block (component) that functions to transmit is called a transmitting unit or a transmitter. In any case, as described above, the realization method is not particularly limited.

[0096] For example, the base station 10 in the embodiment of the present disclosure may function as a computer that performs the processing of the wireless communication method of the present disclosure. FIG. 7 is a diagram showing an example of the hardware configuration of the base station 10. The above-described base station 10 may be physically configured as a computer device including a processor 1001, a memory 1002, a storage 1003, a communication device 1004, an input unit 1005, an output unit 1006, a bus 1007, and the like.

[0097] In the following description, the term "device" can be read as a circuit, device, unit, etc. The hardware configuration of the base station 10 may be configured to include one or more of each device shown in the figure, or may be configured without including some of the devices.

[0098] Each function in the base station 10 is realized by loading a predetermined software (program) onto hardware such as the processor 1001 and the memory 1002, so that the processor 1001 performs calculations and controls the communication by the communication device 1004, or controls at least one of reading and writing data in the memory 1002 and the storage 1003. The functions of modules A, B, and C may be realized by the processor 1001.

[0099] The processor 1001 controls the entire computer by operating, for example, an operating system. The processor 1001 may be composed of a central processing unit (CPU: Central Processing Unit) including an interface with peripheral devices, a control device, an arithmetic device, registers, etc.

[0100] Also, the processor 1001 reads a program (program code), software module, data, etc. from at least one of the storage 1003 and the communication device 1004 into the memory 1002, and executes various processes according to these. As the program, a program that causes a computer to execute at least a part of the operations described in the above embodiments is used. For example, the function of the control unit 11 may be realized by a control program stored in the memory 1002 and operating in the processor 1001, and the same applies to other functional blocks. Although it has been described that the above various processes are executed by one processor 1001, they may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. Note that the program may be transmitted from a network via a telecommunication line.

[0101] The memory 1002 is a computer-readable recording medium and may be composed of at least one of, for example, ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), RAM (Random Access Memory), etc. The memory 1002 may be referred to as a register, a cache, a main memory (main storage device), etc. The memory 1002 can store a program (program code), a software module, etc. executable for implementing the wireless communication method according to an embodiment of the present disclosure.

[0102] The storage 1003 is a computer-readable recording medium and may be composed of at least one of, for example, an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, etc. The storage 1003 may be referred to as an auxiliary storage device. The above-described recording medium may be, for example, a database, a server, or other appropriate medium including at least one of the memory 1002 and the storage 1003.

[0103] The communication device 1004 is hardware (a transmission / reception device) for performing communication between computers via at least one of a wired network and a wireless network, and is also referred to as, for example, a network device, a network controller, a network card, a communication module, etc. The communication device 1004 may include, for example, a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. in order to implement at least one of frequency division duplex (FDD) and time division duplex (TDD). The communication unit 12 may be implemented by the communication device 1004. The communication unit 12 may include a receiving unit that receives a signal and a transmitting unit that transmits a signal.

[0104] An input device (e.g., a key device, a mouse, a microphone, a switch, a button, a sensor, etc.) for receiving an external input and an operating device (e.g., a dial) are connected to the input unit 1005. An output device (e.g., a display, a speaker, an LED lamp, etc.) is connected to the output unit 1006. Note that the input device and the output device connected to the input unit 1005 and the output unit 1006 may be an integrated device (e.g., a touch panel).

[0105] Also, each device such as the processor 1001 and the memory 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus or may be configured using different buses for each device.

[0106] Furthermore, the base station 10 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be implemented by the hardware. For example, the processor 1001 may be implemented using at least one of these hardware components.

[0107] <Notification of Information, Signaling> The notification of information is not limited to the aspects / embodiments described in the present disclosure, and other methods may be used. For example, the notification of information may be performed by physical layer signaling (e.g., downlink control information (DCI), uplink control information (UCI)), upper layer signaling (e.g., radio resource control (RRC) signaling, medium access control (MAC) signaling, notification information (master information block (MIB), system information block (SIB))), other signals, or a combination thereof. Also, the RRC signaling may be referred to as an RRC message, and may be, for example, an RRC connection setup message, an RRC connection reconfiguration message, etc.

[0108] <Applicable System> Each aspect / embodiment described in the present disclosure may be applied to at least one of systems using LTE (Long Term Evolution), LTE-A (LTE-Advanced), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), FRA (Future Radio Access), NR (new Radio), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, UWB (Ultra-WideBand), Bluetooth (registered trademark), and other suitable systems, and next-generation systems extended based on these. Further, multiple systems may be combined (for example, a combination of at least one of LTE and LTE-A and 5G, etc.) and applied.

[0109] <Processing procedures, etc.> The processing procedures, sequences, flowcharts, etc. of each aspect / embodiment described in the present disclosure may be rearranged as long as there is no contradiction. For example, regarding the methods described in the present disclosure, the elements of various steps are presented using an exemplary order and are not limited to the specific order presented.

[0110] <Operation of the base station> The specific operations assumed to be performed by the base station in the present disclosure may, in some cases, be performed by its upper node. In a network consisting of one or more network nodes having a base station, it is clear that various operations performed for communication with a terminal can be performed by at least one of the base station and other network nodes other than the base station (for example, but not limited to, MME or S-GW, etc.). Although the case where there is one other network node other than the base station has been exemplified above, a combination of a plurality of other network nodes (for example, MME and S-GW) may also be possible.

[0111] <Input / Output Direction> Information, etc. (see the item "Information, Signal") can be output from the upper layer (or lower layer) to the lower layer (or upper layer). It may be input and output via a plurality of network nodes.

[0112] <Handling of Input / Output Information, etc.> The input / output information, etc. may be stored in a specific location (for example, memory) or may be managed using a management table. The input / output information, etc. can be overwritten, updated, or appended. The output information, etc. may be deleted. The input information, etc. may be transmitted to other devices.

[0113] <Determination Method> The determination may be made based on a value represented by 1 bit (0 or 1), or may be made based on a boolean value (Boolean: true or false), or may be made by comparing numerical values (for example, comparison with a predetermined value).

[0114] <Variations of the Aspect, etc.> Each aspect / embodiment described in the present disclosure may be used alone, in combination, or switched and used during execution. Further, the notification of predetermined information (for example, the notification of "being X") is not limited to being explicitly performed, and may be performed implicitly (for example, by not performing the notification of the predetermined information).

[0115] As described above in detail, the present disclosure, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described in the present disclosure. The present disclosure can be implemented as modifications and variations without departing from the spirit and scope of the present disclosure defined by the claims. Therefore, the description of the present disclosure is for the purpose of illustration and has no restrictive meaning for the present disclosure.

[0116] <Software> Software should be broadly construed to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc., whether called software, firmware, middleware, microcode, a hardware description language, or by any other name.

[0117] Also, software, instructions, information, etc. may be transmitted and received via a transmission medium. For example, when software is transmitted from a website, server, or other remote source using at least one of wired technologies (such as coaxial cables, optical fiber cables, twisted pairs, digital subscriber lines (DSLs)) and wireless technologies (such as infrared rays, microwaves), at least one of these wired technologies and wireless technologies is included within the definition of the transmission medium.

[0118] <Information, Signal> The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc., which may be referred to throughout the above description, may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0119] In addition, with regard to the terms described in this disclosure and the terms necessary for understanding this disclosure, they may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Also, a signal may be a message. Also, a component carrier (CC) may be referred to as a carrier frequency, a cell, a frequency carrier, etc.

[0120] <“system”, “network”> The terms “system” and “network” used in this disclosure are used interchangeably.

[0121] <parameter, channel name> Also, the information, parameters, etc. described in this disclosure may be represented using absolute values, relative values from a predetermined value, or using corresponding other information. For example, a radio resource may be indicated by an index.

[0122] The names used for the above-described parameters are not limiting names in any way. Furthermore, mathematical formulas, etc. using these parameters may be different from those explicitly disclosed in this disclosure. Since various channels (e.g., PUCCH, PDCCH, etc.) and information elements can be identified by any suitable names, the various names assigned to these various channels and information elements are not limiting names in any way.

[0123] <base station> In the present disclosure, terms such as "Base Station (BS)", "radio base station", "fixed station", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", "access point", "transmission point", "reception point", "transmission / reception point", "cell", "sector", "cell group", "carrier", "component carrier" may be used interchangeably. The base station may also be referred to by terms such as macro cell, small cell, femto cell, pico cell, etc.

[0124] A base station can accommodate one or more (e.g., three) cells. When a base station accommodates multiple cells, the entire coverage area of the base station can be divided into multiple smaller areas, and each of the smaller areas can also provide communication services by a base station subsystem (e.g., a small indoor base station (RRH: Remote Radio Head)). The term "cell" or "sector" refers to part or all of the coverage area of at least one of the base station and the base station subsystem that provides communication services in this coverage.

[0125] <Mobile Station> In the present disclosure, terms such as "Mobile Station (MS)", "user terminal", "User Equipment (UE)", "terminal" may be used interchangeably.

[0126] The mobile station may be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other appropriate terms.

[0127] <Base station / mobile station> At least one of the base station and the mobile station may be referred to as a transmission device, a reception device, a communication device, etc. Note that at least one of the base station and the mobile station may be a device mounted on a moving body, the moving body itself, etc. The moving body may be a vehicle (e.g., a car, an airplane, etc.), a moving body that moves unmanned (e.g., a drone, a self-driving car, etc.), or a robot (humanoid or unmanned). Note that at least one of the base station and the mobile station also includes a device that does not necessarily move during communication operation. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0128] Also, the base station in the present disclosure may be read as a user terminal. For example, for a configuration in which communication between the base station and the user terminal is replaced with communication between a plurality of user terminals (which may be referred to as, for example, D2D (Device-to-Device), V2X (Vehicle-to-Everything), etc.), each aspect / embodiment of the present disclosure may be applied. In this case, the functions of the above-described base station may be configured as functions of the user terminal. Also, terms such as "uplink" and "downlink" may be read as terms corresponding to inter-terminal communication (e.g., "side"). For example, an uplink channel, a downlink channel, etc. may be read as a side channel.

[0129] Similarly, the user terminal in the present disclosure may be read as a base station. In this case, the functions of the above-described user terminal may be configured as functions of the base station.

[0130] <Meaning and interpretation of terms> The terms "determining" and "deciding" as used in this disclosure may encompass a wide variety of operations. "Determining" and "deciding" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up (e.g., searching in a table, database, or other data structure), ascertaining, and considering something as having been "determined" or "decided". Further, "determining" and "deciding" may include considering something as having been "determined" or "decided" after receiving (e.g., receiving information), transmitting (e.g., transmitting information), inputting, outputting, accessing (e.g., accessing data in memory), etc. Additionally, "determining" and "deciding" may include considering something as having been "determined" or "decided" after resolving, selecting, choosing, establishing, comparing, etc. That is, "determining" and "deciding" may include considering something as having been "determined" or "decided" after performing some operation. Also, "determining (deciding)" may be read as "assuming", "expecting", "considering", etc.

[0131] The terms "connected" and "coupled," or any variations thereof, mean any direct or indirect connection or coupling between two or more elements and can include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements can be physical, logical, or a combination thereof. For example, "connected" may be read as "accessed." As used in this disclosure, two elements can be considered to be "connected" or "coupled" to each other using at least one of one or more wires, cables, and printed electrical connections, as well as, by way of some non-limiting and non-exhaustive examples, electromagnetic energy having wavelengths in the radio frequency region, microwave region, and optical (both visible and invisible) region.

[0132] <Reference Signal> The reference signal can also be abbreviated as RS (Reference Signal) and may be referred to as a Pilot depending on the applied standard.

[0133] <Meaning of "based on"> As used in this disclosure, the recitation "based on" does not mean "based solely on" unless otherwise specified. In other words, the recitation "based on" means both "based solely on" and "based at least in part on."

[0134] <"First," "Second"> Any reference to an element using the designations "first," "second," etc. as used in this disclosure does not generally limit the quantity or order of those elements. These designations can be used in this disclosure as a convenient way to distinguish between two or more elements. Thus, a reference to a first and second element does not mean that only two elements can be employed or that the first element must precede the second element in any way.

[0135] <"means"> In the configurations of the above-described respective devices, the "means" may be replaced with a "section", "circuit", "device", or the like.

[0136] <Open format> In the present disclosure, when the terms "include", "including", and their variants are used, these terms are intended to be inclusive, similar to the term "comprising". Further, the term "or" used in the present disclosure is not intended to be an exclusive disjunction.

[0137] <Time units such as TTI, frequency units such as RB, radio frame configuration> A radio frame may be composed of one or more frames in the time domain. Each of one or more frames in the time domain may be referred to as a subframe.

[0138] A subframe may further be composed of one or more slots in the time domain. A subframe may have a fixed time length (e.g., 1 ms) that does not depend on numerology.

[0139] Numerology may be a communication parameter applied to at least one of transmission and reception of a certain signal or channel. Numerology may indicate, for example, at least one of subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, radio frame configuration, specific filtering processing performed by a transceiver in the frequency domain, specific windowing processing performed by a transceiver in the time domain, and the like.

[0140] A slot may be composed of one or more symbols (such as OFDM (Orthogonal Frequency Division Multiplexing) symbols, SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols, etc.) in the time domain. A slot may be a time unit based on a numerology.

[0141] A slot may include a plurality of mini-slots. Each mini-slot may be composed of one or more symbols in the time domain. Also, a mini-slot may be called a sub-slot. A mini-slot may be composed of a smaller number of symbols than a slot. A PDSCH (or PUSCH) transmitted in a time unit larger than a mini-slot may be called a PDSCH (or PUSCH) mapping type A. A PDSCH (or PUSCH) transmitted using a mini-slot may be called a PDSCH (or PUSCH) mapping type B.

[0142] A radio frame, a sub-frame, a slot, a mini-slot, and a symbol all represent time units for signal transmission. Different names corresponding to each of them may be used.

[0143] For example, one sub-frame may be called a transmission time interval (TTI), a plurality of consecutive sub-frames may be called a TTI, or one slot or one mini-slot may be called a TTI. That is, at least one of the sub-frame and the TTI may be a sub-frame (1 ms) in existing LTE, a period shorter than 1 ms (e.g., 1 - 13 symbols), or a period longer than 1 ms. Note that the unit representing the TTI may be called a slot, a mini-slot, etc. instead of a sub-frame.

[0144] Here, TTI refers to, for example, the minimum time unit for scheduling in wireless communication. For example, in an LTE system, the base station performs scheduling to allocate radio resources (such as the frequency bandwidth and transmission power that can be used at each user terminal) to each user terminal in units of TTI. Note that the definition of TTI is not limited to this.

[0145] TTI may be a transmission time unit such as a channel - encoded data packet (transport block), code block, codeword, etc., or may be a processing unit such as scheduling and link adaptation. Note that when TTI is given, the time interval (e.g., the number of symbols) in which a transport block, code block, codeword, etc. are actually mapped may be shorter than the TTI.

[0146] Note that when one slot or one mini - slot is called TTI, one or more TTIs (i.e., one or more slots or one or more mini - slots) may be the minimum time unit for scheduling. Also, the number of slots (mini - slot numbers) constituting the minimum time unit for the scheduling may be controlled.

[0147] A TTI having a time length of 1 ms may be called a normal TTI (TTI in LTE Rel.8 - 12), normal TTI, long TTI, normal sub - frame, normal sub - frame, long sub - frame, slot, etc. A TTI shorter than the normal TTI may be called a shortened TTI, short TTI, partial TTI (partial or fractional TTI), shortened sub - frame, short sub - frame, mini - slot, sub - slot, slot, etc.

[0148] Note that a long TTI (e.g., normal TTI, sub - frame, etc.) may be read as a TTI having a time length exceeding 1 ms, and a short TTI (e.g., shortened TTI, etc.) may be read as a TTI having a TTI length less than that of the long TTI and not less than 1 ms.

[0149] A resource block (RB) is a resource allocation unit in the time domain and the frequency domain, and in the frequency domain, it may include one or more consecutive subcarriers. The number of subcarriers included in an RB may be the same regardless of the numerology, for example, it may be 12. The number of subcarriers included in an RB may be determined based on the numerology.

[0150] Also, the time domain of an RB may include one or more symbols, and may be the length of 1 slot, 1 mini-slot, 1 sub-frame, or 1 TTI. 1 TTI, 1 sub-frame, etc. may each be composed of one or more resource blocks.

[0151] Note that one or more RBs may be referred to as physical resource blocks (PRBs), sub-carrier groups (SCGs), resource element groups (REGs), PRB pairs, RB pairs, etc.

[0152] Also, a resource block may be composed of one or more resource elements (REs). For example, 1 RE may be a radio resource area of 1 subcarrier and 1 symbol.

[0153] A bandwidth part (BWP) (which may also be called a partial bandwidth, etc.) may represent a subset of consecutive common resource blocks (RBs) for a certain numerology in a certain carrier. Here, the common RB may be specified by the index of the RB based on the common reference point of the carrier. A PRB is defined in a certain BWP and may be numbered within that BWP.

[0154] The BWP may include a BWP for UL (UL BWP) and a BWP for DL (DL BWP). One or more BWPs may be configured within one carrier for a UE.

[0155] At least one of the configured BWPs may be active, and the UE may not be assumed to transmit and receive a predetermined signal / channel outside the active BWP. Note that in the present disclosure, terms such as "cell" and "carrier" may be read as "BWP".

[0156] The structures such as the radio frames, subframes, slots, minislots, and symbols described above are merely examples. For example, the number of subframes included in a radio frame, the number of slots per subframe or radio frame, the number of minislots included in a slot, the number of symbols and RBs included in a slot or minislot, the number of subcarriers included in an RB, and the number of symbols, symbol length, cyclic prefix (CP) length, etc. within a TTI can be changed in various ways.

[0157] <Maximum Transmit Power> The "Maximum Transmit Power" described in the present disclosure may mean the maximum value of the transmit power, or may mean the nominal UE maximum transmit power, or may mean the rated UE maximum transmit power.

[0158] <Article> In the present disclosure, for example, when an article is added by translation like a, an, and the in English, the present disclosure may include that the noun following these articles is in the plural form.

[0159] <"Different"> In the present disclosure, the term "A and B are different" may mean that "A and B are different from each other". Note that the term may also mean that "A and B are each different from C". Terms such as "separate" and "coupled" may also be interpreted in the same way as "different".

Industrial Applicability

[0160] The present disclosure is useful for wireless systems.

Explanation of Signs

[0161] 1 CU 2 DU 3a, 3b Wireless stations 4a, 4b Terminals 10 Base station 11 Control unit 12 Communication unit

Claims

1. A control unit that determines a cooperation method in signal transmission of a plurality of radio stations and the number of streams in each of the radio stations based on information that appears due to movement of a terminal; A transmission unit that cooperates the plurality of radio stations according to the cooperation method and transmits a signal to the terminal using the stream; and when retransmission of a signal occurs, the control unit determines the cooperation method and the number of streams in the retransmission signal based on information that appears due to movement of the terminal; the information that appears due to movement of the terminal is the spread of the Doppler spectrum; Base station.

2. A control unit that determines a cooperation method in signal transmission of a plurality of radio stations and the number of streams in each of the radio stations based on information that appears due to movement of a terminal; A transmission unit that cooperates the plurality of radio stations according to the cooperation method and transmits a signal to the terminal using the stream; and when retransmission of a signal occurs, the control unit determines the cooperation method and the number of streams in the retransmission signal based on information that appears due to movement of the terminal; the information that appears due to movement of the terminal is the variation of received power; Base station.

3. The control unit controls the phase rotation of the signal transmitted using the stream based on the amount of phase rotation of the received signal in the terminal or the channel quality between the terminal; The base station according to claim 1 or 2.

4. A base station determines a cooperation method in signal transmission of a plurality of radio stations and the number of streams in each of the radio stations based on information that appears due to movement of a terminal; cooperates the plurality of radio stations according to the cooperation method and transmits a signal to the terminal using the stream; when retransmission of a signal occurs, determines the cooperation method and the number of streams in the retransmission signal based on information that appears due to movement of the terminal; the information that appears due to movement of the terminal is the spread of the Doppler spectrum; Communication method.

5. A base station determines a cooperation method in signal transmission of a plurality of radio stations and the number of streams in each of the radio stations based on information that appears due to movement of a terminal; cooperates the plurality of radio stations according to the cooperation method and transmits a signal to the terminal using the stream; when retransmission of a signal occurs, determines the cooperation method and the number of streams in the retransmission signal based on information that appears due to movement of the terminal; The information that appears due to the movement of the terminal is the fluctuation of the received power. Communication method.

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