Base station and communication system

Abstract

To enable a base station to transmit information indicating transmission power to each of a plurality of terminals.SOLUTION: There is provided a base station provided with a control device and a radio device. The radio device receives reference signals from each of a plurality of terminals. The control device estimates reception quality of transmission from the terminals based on the reference signals for each of the plurality of terminals. The control device determines transmission power for the terminals to transmit uplink signals based on the estimated reception quality for each of the plurality of terminals. The radio device transmits information indicating the determined transmission power to each of the plurality of terminals.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a base station and a terminal. [Background technology]

[0002] The mobile communications standardization organization 3GPP (Third Generation Partnership Project) has set coverage enhancement as one of the topics for Release 17. The conference is examining technologies that will enable communications that meet desired communication requirements, regardless of the distance from the base station, even when there is significant propagation loss between the base station and the terminal.

[0003] Background art related to the present disclosure includes, for example, a technology for improving the signal-to-noise ratio (SNR) at a receiving station by repeatedly transmitting the same signal and integrating the same signal at the receiving station (e.g., Non-Patent Document 1). Also, there is a technology for enabling multiple terminals connected to a base station via Non-orthogonal Multiple Access (NOMA) to transmit data in the same time period using the same frequency band (e.g., Non-Patent Document 2). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] 3GPP TR 38.830, Study on NR coverage enhancements (Release 17), December 2020 [Non-patent document 2] M. Moriyama, T. Takizawa, M. Oodo, H. Tezuka, and F. Kojima, “Experimental Evaluation of a Novel Up-link NOMA System for IoT communication Equipping Repetition Transmission and Receive Diversity,” IEICE Trans. Commun., Vol.E102 -B, No.8, pp1467-1476 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a technique that enables a plurality of transmitting stations connected to a receiving station via non-orthogonal multiple access to perform suitable continuous transmission. [Means for solving the problem]

[0006] One aspect of the present disclosure is a transmission control method for a plurality of transmitting stations that are non-orthogonally multiple-connected with a receiving station of a wireless communication partner, each of which is capable of transmitting the same signal to the receiving station a predetermined number of times in succession at a predetermined period common to the plurality of transmitting stations by continuous transmission. In this transmission control method, an information processing device calculates an initial value of transmission power to be allocated to each of the plurality of transmitting stations, which increases as the reception quality at the receiving station improves and which ensures a required reception power difference between the transmitting stations, and calculates the number of continuous transmissions for a first transmitting station among the plurality of transmitting stations that is assigned the largest initial value of transmission power, based on an index value of reception quality.

[0007] Another aspect of the present disclosure is an information processing device including a control unit, wherein the control unit calculates an initial value of transmission power to be allocated to each of a plurality of transmitting stations that are non-orthogonal multiple-connected with a receiving station in wireless communication, the plurality of transmitting stations being capable of transmitting the same signal to the receiving station a predetermined number of times in succession at a predetermined period common to the plurality of transmitting stations through continuous transmission, the initial value of transmission power being higher as reception quality at the receiving station improves and that ensures a required difference in reception power between the transmitting stations, and calculates the number of continuous transmissions of a first transmitting station among the plurality of transmitting stations that is assigned the largest initial value of transmission power, based on an index value of reception quality.

[0008] Another aspect of the present disclosure is a transmission control method for a first transmitting station included in a plurality of transmitting stations that are non-orthogonal multiple-accessed with a receiving station of a wireless communication partner, each of which is capable of transmitting the same signal to the receiving station a predetermined number of times in succession at a predetermined period common to the plurality of transmitting stations through continuous transmission. This transmission control method includes the first transmitting station receiving information including the number of continuous transmissions to the receiving station and the transmission power to be used for each continuous transmission, and performing continuous transmission based on the information. The information includes, as the transmission power, a first value that is an initial value of transmission power assigned to the first transmitting station, and, if the first value is not the maximum value of the initial values ​​of transmission power assigned to the plurality of transmitting stations, further includes a second value that is greater than the first value and is used after the continuous transmission of the transmitting station assigned the maximum value is stopped.

[0009] Another aspect of the present disclosure is a first transmitting station included in a plurality of transmitting stations that are non-orthogonally multiple-connected with a receiving station of a wireless communication partner, each of which is capable of transmitting the same signal to the receiving station a predetermined number of times in a predetermined cycle common to the plurality of transmitting stations through continuous transmission. The first transmitting station includes a communication unit that receives information including the number of continuous transmissions to the receiving station and the transmission power to be used for each continuous transmission, and a control unit that controls the continuous transmission based on the information using the communication unit. The information includes a first value that is an initial value of transmission power assigned to the first transmitting station as transmission power, and if the first value is not the maximum value of the initial values ​​of transmission power assigned to the plurality of transmitting stations, further includes a second value that is greater than the first value and is used for continuous transmission after continuous transmission in the transmitting station to which the maximum value is assigned has stopped.

[0010] Other aspects of the present disclosure may include a wireless communication system including the above-described plurality of transmitting stations and receiving stations, a program for causing a computer to operate as the above-described transmitting station, receiving station, or information processing device, a non-transitory storage medium on which the program is recorded, and the like. [Effects of the Invention]

[0011] According to the present disclosure, it becomes possible for a plurality of transmitting stations connected to a receiving station via non-orthogonal multiple access to perform suitable continuous transmission. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1A is a diagram showing a first example of the configuration of a wireless communication system, and FIG. 1B is a diagram showing a second example of the configuration of a wireless communication system. [Figure 2] FIG. 2 is a diagram illustrating an example of a radio frame applied to a radio communication system. [Figure 3] FIG. 3 is an explanatory diagram of power multiplexing and interference suppression and cancellation techniques. [Figure 4] FIG. 4 is a diagram showing an example of continuous transmission in a wireless communication system. [Figure 5]FIG. 5 is a diagram illustrating an example of the hardware configuration of a base station and a terminal. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of a terminal. [Figure 7] FIG. 7 is a block diagram showing an example of the configuration of a base station. [Figure 8] FIG. 8 is a flowchart showing an example of processing (calculation of the number of consecutive transmissions and the transmission power used in each transmission) in the base station. [Figure 9] FIG. 9 is a flowchart illustrating the details (first example) of step S001 in FIG. [Figure 10] FIG. 10 is a flowchart illustrating details (second example) of step S001 in FIG. [Figure 11] FIG. 11 is a flowchart illustrating the details of step S002 in FIG. [Figure 12] FIG. 12 is a flowchart illustrating the details of step S003 in FIG. [Figure 13] FIG. 13 is a diagram illustrating the calculation formula for SINR. [Figure 14] FIG. 14 illustrates an example of improved continuous transmission performed in a wireless communication system. [Figure 15] FIG. 15 is a diagram showing an experimental example relating to continuous transmission. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Wireless communication system configuration> Fig. 1 is a diagram showing a first configuration example of a wireless communication system according to an embodiment. Fig. 1B is a diagram showing a second configuration example of the wireless communication system. The wireless communication system according to the first configuration example includes a base station 1 and a plurality of terminals 2 (#0 to #K-1, K is a natural number including 0) that communicate wirelessly with the base station 1. The base station 1 is an example of a receiving station, and the plurality of terminals 2 are an example of a plurality of transmitting stations.

[0014] Each of the multiple terminals 2 is called UE (User Equipment). Each of the multiple terminals 2 includes an antenna 20, a radio device 2a connected to the antenna 20, and a control device 2b connected to the radio device 2a. The control device 2b acquires (receives) data from a sensor 3 or the like. The control device 2b controls the radio device 2a to transmit data signals or control signals to the base station 1 or to receive control signals and the like from the base station 1. The radio device 2a converts signals to be transmitted, including data signals and control signals, into radio signals and radiates (transmits) them from the antenna 20. The radio device 2a converts the radio signals received from the antenna 20 into a signal format that can be handled by the control device 2b. The number of antennas 20 may be one or two or more. The terminal 2 may have two or more antennas, and perform MIMO (multiple-input and multiple-output) communication with the base station 1.

[0015] The base station 1 includes one or more antennas 10, a radio device 1a connected to the antenna 10, and a control device 1b connected to the radio device 1a. The radio device 1a and the control device 1b have the same functions as the radio device 2a and the control device 2b. The control device 2b can transmit data received from the terminal 2 to a server 4 or the like. The control device 1b is an example of an information processing device (computer). Note that the information processing device may be included in the base station 1, or may be a terminal device (such as a server) different from the base station 1 (independent from the base station 1). In other words, a terminal device such as a server may be configured to calculate the number of consecutive transmissions to multiple terminals 2 and the transmission power to be used for each transmission, and transmit the data to each terminal 2.

[0016] According to the wireless communication system, for example, data (such as IoT (Internet of Things) data) acquired from sensors 3 at each of a plurality of terminals 2 can be accumulated in a server 4 via a base station 1. Data from the server 4 can also be transmitted to each of the plurality of terminals 2 via the base station 1. The terminals 2 may be fixed terminals or mobile terminals. The mobile terminals may be portable terminals or in-vehicle terminals. The in-vehicle terminals may be terminals mounted on a vehicle or terminals installed in the vehicle.

[0017] As shown in the second configuration example of FIG. 1B, a base station 1A having two or more distributed base stations and a control device 1b may be applied instead of the base station 1. The distributed base station has an antenna 10 and a radio device 1a, and is called an RRH (Remote Radio Head: radio unit). The control device 1b to which the distributed base station is connected is called a BBU (Base Band Unit: signal processing unit). In the following description, a base station 1 having a first configuration example will be described.

[0018] In the first and second configuration examples, the base station 1 and each of the multiple terminals 2 communicate (transmit and receive signals) using a downlink (DL) and an uplink (UL). The DL is a line from the base station 1 to the terminals 2, and includes a control channel (control CH) used to transmit (notify) control signals. On the other hand, the UL is a line from the terminals 2 to the base station 1, and includes a control CH and a shared channel (shared CH) used to transmit data (user data). The shared CH is also called a data channel.

[0019] <radio frame> UL signals and DL signals are transmitted using time domains allocated by time division multiplexing. FIG. 2 is a diagram illustrating an example of a radio frame applied to a wireless communication system. In FIG. 2, the radio frame has a predetermined time length. The radio frame length is 10 ms in 5G, but may be shorter or longer than 10 ms. The radio frame is also divided into multiple subframes. In 5G, the subframe length is specified as 1 ms, and the radio frame is divided into 10 subframes. However, the subframe length and the number of divisions are not limited to the example of 5G. The subframe may be further divided into two or more slots (slot length: 500 μm). As shown in FIG. 2, each subframe of the radio frame is allocated to DL or UL. In the example of FIG. 2, DL and UL are allocated so that one DL is followed by four ULs. However, this allocation can be changed. The slots in the subframe allocated to UL are equally divided, with a reference signal (RS) mapped to the first half and a data signal (DS) mapped to the second half. However, the arrangement of the reference signal and the data signal in one slot can be changed as appropriate.

[0020] The reference signal is a signal known to the receiving station (base station 1) and is used to estimate the channel (propagation path or communication path) of the radio signal. The data signal is a signal in which user data is modulated and coded according to a predetermined MCS (Modulation and Coding Scheme).

[0021] <Characteristics of wireless communication systems> The wireless communication system has the following features in uplink communication of data signals. First, the wireless communication system of this embodiment employs configured grant (CG). As shown in FIG. 2, in UL communication, CG is realized by notifying terminals 2 in advance of frequency channels and slots available for CG, preparing different reference signals for each terminal 2, and transmitting the reference signals together with data signals as payloads. CG can eliminate communication delays associated with the procedure in which terminals obtain grants, which are permission to communicate, from the base station.

[0022] Second, in a wireless communication system, non-orthogonal multiple access is used to transmit wireless signals (reference signals and data signals) from multiple terminals 2 using the same frequency domain and the same time domain (slot). At this time, each terminal 2 transmits a wireless signal at a transmission power specified by the base station 1 so that a desired difference in received power occurs between the terminals 2 at the base station 1. NOMA can reduce the waiting time for signal transmission. However, it is necessary for the base station 1 to suppress and remove inter-terminal interference from each terminal 2.

[0023] Figure 3 is an explanatory diagram of power multiplexing and interference suppression / cancellation technology. The diagram on the left side of Figure 3 schematically shows the received power at base station 1 of radio signals transmitted from terminals A, B, and C, which are examples of multiple terminals 2. In this example, the data signals received from terminals A, B, and C are in a state where they are superimposed (superimposed signals) with the received power at base station 1. The power difference D1 between the received power at terminal A and the received power at terminal B, and the power difference D2 between the received power at terminal B and the received power at terminal C, are each equal to or greater than the received power difference between terminals 2 at base station 1 (required power difference ΔP) required for suitable interference suppression / cancellation.

[0024] The base station 1 obtains the propagation path characteristics based on the reference signal, and performs demodulation and decoding of the superimposed signal using the propagation path characteristics, thereby obtaining data from the terminal A. The inventors of the present application have referred to the wireless communication system including the above-mentioned CG, UL communication using NOMA, and interference suppression and elimination technology (SIC, etc.) as STABLE (Simultaneous Transmission Acceleration). However, the transmission (continuous transmission) control method according to the present application is as follows: It is applicable to wireless communication systems that use NOMA other than STABLE.

[0025] The Successive Interference Cancellation (SIC) algorithm is used to suppress and remove interference from the signal of terminal A from the superimposed signal. SIC is an algorithm that sequentially evaluates signals from terminals one by one in descending order of received signal strength (Received Signal Strength Indicator: RSSI) and eliminates those signals. The SIC algorithm uses an estimate of the communication path (propagation path) characteristics between terminal 2 and base station 1 using a reference signal specific to terminal 2. In other words, the SIC algorithm uses the estimate of the propagation path characteristics to reproduce (generate) the signal (called a replica signal) transmitted from terminal 2 (terminal A) with the strongest received signal among the superimposed signals, and subtracts it from the superimposed signal. This eliminates interference from the data signal from terminal A from the superimposed signal (see the middle diagram in Figure 3).

[0026] The superimposed signal from which the data signal from terminal A has been removed can be demodulated and decoded using channel characteristics based on the reference signal of terminal B to obtain the data from terminal B. Furthermore, a replica signal of the data signal transmitted from terminal B is generated using the SIC algorithm and subtracted from the superimposed signal, thereby removing the interference from the data signal from terminal B and leaving the data signal transmitted from terminal C (see the diagram on the right of Figure 3). The data from terminal C can be obtained by demodulating and decoding this signal using channel characteristics based on the reference signal of terminal C.

[0027] <Repetition> Furthermore, in the wireless communication system, each of the multiple terminals 2 can perform continuous transmission. Continuous transmission means repeatedly transmitting the same signal at a predetermined cycle (for example, a slot). The signals transmitted from the terminals 2 by continuous transmission are received and integrated by the base station 1. The integration allows the received signals to be added together, thereby increasing the SNR and improving the reception quality (propagation loss).

[0028] When multiple terminals 2 performing UL communication using the same frequency domain and the same time domain perform continuous transmission, the number of continuous transmissions (number of times the same signal is transmitted, number of slots for transmitting the same signal) N is determined according to the terminal 2 with the smallest received power (largest propagation loss) among the multiple terminals 2. N is a natural number.

[0029] Fig. 4 is a diagram showing an example of continuous transmission. In Fig. 4, it is assumed that there are five terminals 2 (K=5) performing UL communication in NOMA. The identification information (user IDs) of the five terminals 2 are "1", "2", "3", "4", and "5". The order of the numbers of terminals "1" to "5" is in descending order of received power at base station 1, and the received power of the signal from terminal "5" is the smallest and has the largest propagation loss. For this reason, the number of continuous transmissions N for terminal "5" is set to 6 (N=6). In this case, the number of continuous transmissions N for the remaining terminals "1" to "4" is also set to the same number (6) as for terminal "5".

[0030] However, for example, terminal "1" has the highest reception power among the five terminals 2, and therefore the number of consecutive transmissions required to obtain the desired reception quality (SINR or error rate) by integration is thought to be less than that of terminal "5." Nevertheless, transmitting with the same number of consecutive transmissions as terminal "5" would result in unnecessary power consumption, and would not be considered suitable consecutive transmission. The following description will explain in detail a wireless communication system that can at least solve the above-mentioned problems.

[0031] <Hardware configuration> FIG. 5 is a diagram illustrating an example of the hardware configuration of the base station 1 and the terminal 2. 1A, the base station 1 includes M antennas 10 (10-1 to 10-M (M is a natural number)), a radio (radio processing device) 1a, and a control device 1b. The control device 1b includes a processor 11, a storage device (memory) 12, an internal interface 13, and a network interface 14 for communicating with other base stations, etc.

[0032] The processor 11 is also called a Central Processing Unit (CPU) or a Microprocessor Unit (MPU). The processor 11 is not limited to a single processor. The processor 11 may have a multi-processor configuration. The processor 11 may also have a multi-core configuration with a single physical CPU connected via a single socket. The processor 11 may also include an arithmetic unit with various circuit configurations, such as a Digital Signal Processor (DSP) or a Graphics Processing Unit (GPU). The processor 11 may also be one that cooperates with an integrated circuit (IC), other digital circuits, or analog circuits. The integrated circuit may be, for example, an LSI, an Application Specific Integrated Circuit (ASIC), or a Programmable Logic Device (PLD). The PLD may be, for example, a Field-Programmable The processor 11 is, for example, a microcontroller ( The processor 11 may be what is called an MCU, an SoC (System-on-a-chip), a system LSI, a chipset, etc. The processor 11 is an example of a control unit.

[0033] The storage device 12 stores a sequence of instructions (computer program) executed by the processor 11, or data processed by the processor 11. The internal interface (internal IF) 13 is a circuit that connects various peripheral devices to the processor 11.

[0034] The network interface (NW-IF) 14 is a communication device that enables the base station 1 to access a network to which other base stations are connected. The network to which other base stations are connected is also called a backhaul. The backhaul is, for example, a wired network using optical communication.

[0035] The wireless device 1a includes a transmitter for transmitting a wireless signal and a receiver for receiving the wireless signal, and is connected to antennas 10 (10-1, . . . , 10-M). The wireless device 1a may have M systems of transmitters and receivers, the same number as the number of antennas.

[0036] 5, the terminal 2 includes an antenna 20, a radio (radio processing device) 2a, and a control device 2b. The control device 2b includes a processor 21, a storage device (memory) 22, an internal interface (internal IF) 23, and a network interface (NW-IF) 24 for communicating with other base stations, etc. The processor 21 is an example of a "control unit," and the NW-IF 24 is an example of a "communication unit."

[0037] The processor 21, the storage device 22, the internal IF 23, the NW-IF 24, and the radio 2a have the same functions as the processor 11, the storage device 12, the internal IF 13, the NW-IF 14, and the radio 1a.

[0038] <Device configuration> Fig. 6 is a block diagram showing an example of the configuration of a terminal. When the processor 21 shown in Fig. 5 executes a program stored in the storage device 22, the terminal 2 operates as a device equipped with an RS unit 210 and a DS unit 220. The RS unit 210 includes an RS generation unit 211. The RS generation unit 211 generates a reference signal.

[0039] The DS unit 220 includes an encoding unit 221 and a modulation unit 222. The encoding unit 221 performs predetermined error correction encoding on input data (user data). The error correction encoding is, for example, turbo encoding, but other encoding formats may also be used. Before that, for example, CRC (Cyclic Redundancy Check) coding may be performed.

[0040] The modulation unit 222 digitally modulates the coded data to generate a data signal. The digital modulation method is, for example, Quadrature Amplitude Modulation (QAM), Phase Shift Keying (PSK), etc. The coding and modulation method is determined by the MPEG encoding method set in the terminal 2. Follow CS.

[0041] The terminal 2 further includes a multiplexer (multiplexing unit) 202. The output terminal of the multiplexer 202 is connected to the antenna 20. After outputting the reference signal, the multiplexer 202 switches to outputting the data signal, thereby connecting one slot's worth of reference signal and data signal to the antenna 20. Note that a signal called a CP (Cyclic Prefix) is provided in the preceding stage of each of the reference signal and the data signal to compensate for the influence of delayed waves. In the case of continuous transmission, the data signal is generated so that the same data signal is transmitted a specified number of times (N times) from the base station 1. Alternatively, the generated data signal may be duplicated and transmitted a specified number of times (N times).

[0042] <Base station configuration> Fig. 7 is a diagram showing an example of the configuration of the base station 1. When the processor 11 of the base station 1 executes a program stored in the storage device 12, the base station 1 operates as a device having the blocks shown in Fig. 7. As shown in Fig. 7, the base station 1 includes an antenna 10, a demultiplexer (separation unit) 101, an RS unit 110, and a DS unit 120. The demultiplexer 101, by a switching operation, sends a reference signal in a signal received from the antenna 10 to an integrator 111 of the RS unit 110, and sends a data signal to an integrator 121 of the DS unit 120. At this time, the CPs added to the reference signal and the data signal are removed.

[0043] The integrator 111 adds up the reference signals received by successive transmissions to obtain a reference signal with sufficient received signal power. The channel estimator 112 uses the integrated reference signal to calculate an estimate of the channel characteristics (channel vector). This estimate is used for demodulation processing in the demodulator 123 and for generating a replica signal.

[0044] The DS unit 120 includes an integrator 121, a replica remover 122, a demodulator 123, a decoder 124, and a replica generator 126. The integrator 121 calculates the number of consecutive transmissions N assigned to the target terminal 2 (terminal k). k The SNR is improved by adding together the data signals (N slots).

[0045] The replica removal unit 122 subtracts the replica signal generated by the replica generation unit 126 from the integrated received signal (superimposed signal). The demodulation unit 123 uses the estimated value of the communication channel characteristics from the communication channel estimation unit 112 to separate the data signal of the target terminal 2 (terminal 2 with the largest transmission power value among the terminals that have transmitted the superimposed signal) and demodulates the separated data signal. The decoding unit 124 decodes the coding performed by the coding unit 221 of terminal 2 and outputs the original data.

[0046] The replica generation unit 126 includes an encoding unit 127, a modulation unit 128, and a multiplication unit 129. The encoding unit 127 and the modulation unit 128 perform the encoding and digital modulation performed in the terminal 2 on the data output from the decoding unit 124. The multiplication unit 129 multiplies the modulated data by an estimate of the communication path characteristics between the target terminal 2 (terminal 2 that is the source of the decoded data) and the base station 1. This generates a replica signal. The replica signal is supplied to the replica removal unit 122.

[0047] <Calculation of number of consecutive transmissions and transmission power> Fig. 8 is a flowchart showing an example of processing in a base station (calculating the number of consecutive transmissions and the transmission power value used in each transmission). The processing shown in Fig. 8 is performed, for example, by the processor 11 of the base station 1. For example, when multiple terminals 2 transmit data to the base station 1, this processing is started when the base station 1 receives a transmission request for a data signal from the terminal 2 via the UL control channel. However, the start trigger is not limited to the above. The input parameters to the processor 11 are as follows: Terminal ID (user ID) k: k takes a value from the minimum value "0" to the maximum value "K-1". Maximum number of consecutive transfers N max : The maximum number of consecutive transmissions possible in a wireless communication system. For example, in 5G, In this case, operation with 32 times is being considered. The maximum number of consecutive transmissions can be set appropriately, and it may be 32 times, or more or less than 32 times. BLER (Block Error Rate) characteristics S(γ) for SINR and MCS BLER target value S target ·Maximum transmission power P max,UE : Maximum transmission power allowed for use by terminal 2 Base station noise power P N Required power difference ΔP: The difference in received power between terminals at the base station required for optimal interference suppression and cancellation.

[0048] The input parameters are stored in, for example, the storage device 12. The BLER characteristics for SINR are prepared in, for example, a correspondence table in the storage device 12, and the BLER characteristics for the input SINR are retrieved. The input parameters may be stored in a location other than the storage device 12. Alternatively, the processor 11 may acquire some or all of the input parameters from a network.

[0049] In step S001, the processor 11 calculates the propagation loss L between the base station 1 and the terminal 2 for a plurality of (K) terminals 2 performing UL communication by NOMA. k The processor 11 also measures the propagation loss L k Arrange in ascending order of reception quality.

[0050] In step S002, the processor 11 sets the initial value of transmission power (initial power value P k,0 ) to assign

[0051] In step S003, the processor 11 calculates the number of consecutive transmissions N for each of the K terminals 2. k and the transmission power value P k,n Update the program at the end of step S003. The output parameters from the processor 11 are as follows: The number of consecutive transmissions N specified for each of K terminals 2 (terminals with terminal IDs k=0 to K-1) k The transmission power value P used in each of the K terminals 2 in the continuous transmission k,n (n=1~maximum Maximum number of transfers (N k ))

[0052] In step S004, the base station 1 notifies (transmits) information including output parameters via the DL control channel to each of the multiple terminals 2. At this time, the base station 1 can include information indicating the continuous transmission start slot and the frequency channel to be used in the notified information.

[0053] 9 is a flowchart illustrating the details (first example) of step S001 in FIG. 8. In step S011, the processor 11 sets the transmission power for each terminal 2 to a transmission power value p k,UE This instruction is sent through the DL control channel.

[0054] In step S012, the processor 11 receives a signal from each terminal 2 via a UL control channel. The received signal strength r of the control signal transmitted to base station 1 k,BS Measure.

[0055] In step S013, the processor 11 calculates the transmission power value p k,UE Received signal strength r k,BS By subtracting this, the propagation loss L between terminal 2 and base station 1 is k In step S003, if the base station 1 has a plurality of antennas 10, for example, the average value of the propagation loss related to the received signal of each antenna 10 is calculated as the propagation loss L k It can be used as:

[0056] Fig. 10 is a flowchart illustrating details (second example) of step S001 in Fig. 8. In step S021, the processor 11 instructs each terminal 2, via the DL control channel, to measure and report the received signal strength of a transmission signal (designated transmission signal) designated by the base station 1 to the terminal 2.

[0057] In step S022, each terminal 2 receives a signal strength r k,UE Each terminal 2 measures the received signal strength r k,UE The base station 1 then transmits a report including the measurement results.

[0058] In step S023, the processor 11 of the base station 1 receives the report from each terminal 2 and calculates the transmission power value p k,BS From the received signal strength rk,UE By subtracting k Calculate the propagation loss L k Either the first or second example may be used to calculate the value.

[0059] FIG. 11 is a flowchart illustrating the details of step S002 in FIG. 8. In step S031, the processor 11 sets the value of the number k that identifies one of K terminals 2 (terminals #0 to #K-1) to 0. For the K terminals 2, the values ​​of k=0 to K-1 that are terminal IDs correspond to the propagation loss L k The terminal 2 with k=0 has a path loss L k indicates the smallest terminal 2.

[0060] In step S032, processor 11 determines whether the current value of k is the minimum value of k, 0. If it is determined that the value of k is 0, the process proceeds to step S033; otherwise, the process proceeds to step S034.

[0061] In step S033, the processor 11 sets the power initial value P 0,0 The maximum transmission power P max,UE However, the maximum transmission power P max,UE Instead of P max,UE A lower desired value may be used, and then the process proceeds to step S035.

[0062] When the process proceeds to step S034, the processor 11 sets the initial power value P k,0 is determined to be the smaller of the first and second values ​​shown below. First value: Maximum transmission power P of terminal 2 max,UE Second value: power value P of terminal 2 (terminal k-1) of k-1 k-1,0 From terminal 2 of k (terminal k) Propagation loss L k and the propagation loss L of terminal k-1 k-1 and the difference in required power ΔP minus The second value is smaller than the first value. The second value is equal to or larger than the required power difference ΔP, so that a sufficient power difference can be obtained between terminals 2.

[0063] In step S035, processor 11 determines whether the current value of k is K-1 (the maximum value of k). If it is determined that the value of k is K-1, the flow in Fig. 11 ends; otherwise, the process proceeds to step S036. In step S036, the value of k is incremented (1 is added to the current value of k), and the process returns to step S032.

[0064] Fig. 12 is a flowchart illustrating details of step S003 in Fig. 8. In step S041, the processor 11 sets the value of terminal k to 0 and the value of the number of consecutive transmissions n to 1.

[0065] In step S042, the SINR γ k,n Calculate γ k,n The value of can be calculated using the formula shown in Figure 13. k,n The value of is determined by the value of A in the formula. The value of A in the formula is the power value (integral value) after terminal 2 with terminal ID=k has transmitted n times in succession. Also, B in the formula is the interference power received from terminals 2 other than terminal ID=k. P n is the noise power of base station 1 as described above.

[0066] In step S043, the processor 11 determines the desired number of consecutive transmissions N k Calculate the value of the desired number of consecutive transfers N k is, for example, the BLER characteristic S( γ) is the target value of BLER S target Find the value of n when it is the smallest value when it is smaller than Therefore, the value of n at that time is N k This means that terminal 2 of the current value of k is set to N kThis means that if continuous transmission is performed once, continuous transmission will be stopped (continuous transmission will not be performed in the next slot). Then, the process proceeds to step S044.

[0067] However, in step S043, the value of n obtained is the maximum number of consecutive transmissions N max If it is more than In step S046, the processor 11 k The value of N max After that, the flow of FIG. 12 ends.

[0068] In step S044, the power value P k+1以降,n+1 That is, the processor 11 allocates the number of consecutive transmissions n=N calculated in step S043 for the terminals 2 from k+1 onwards for the current value of k. k The transmission power value is allocated to the next slot n+1 after the desired number of consecutive transmissions N. The calculation of the transmission power value can be performed by the same process as that of step S002 (the flow of S031 to S36 shown in FIG. 11). However, this process is performed k The propagation loss L k The terminal IDs are assigned in ascending order of terminal ID: 0 to K-1.

[0069] In step S045, processor 11 determines whether the current value of k is K-1. If it is determined that the value of k is K-1, the flow in Fig. 12 ends, and if not, the process proceeds to step S047. In step S047, processor 11 increments the value of k, and the process returns to step S042.

[0070] Fig. 14 is a diagram showing an example of improved continuous transmission executed in a wireless communication system. When the processes according to the flows shown in Figs. 8 to 12 are performed for the terminals 2 with terminal IDs "1" to "5" shown in Fig. 4, the following occurs. That is, the propagation loss L kThe terminals "1" to "5" are arranged in ascending order of propagation loss L (step S001), and an initial power value is assigned to each terminal (step S002). k The maximum transmission power is allocated to terminal "1" having the smallest transmission power, and initial power values ​​are set for terminals "2" to "5" so that the difference in received power at base station 1 is equal to or greater than the required power difference ΔP.

[0071] Then, in step S003 of the flow of FIG. 12, the desired number of consecutive transmissions N of terminal "1" is k When is set to 2 (step S043), continuous transmission from terminal "1" is performed in the first (n=1) and second (n=2) slots in FIG. 14, and is stopped in the slot n=2.

[0072] In this case, for the next slot n=3, the remaining terminals “2” to “5” except for terminal “1” At this time, the transmission power value of terminal "2" is updated to the maximum transmission power, and the transmission powers of terminals "3" to "5" are set to values ​​that provide a power difference in the received power at base station 1 that is equal to or greater than the required power difference ΔP. As a result, the received powers of terminals "2" to "5" in slot n=3 are each increased.

[0073] In the subsequent step S043, the number of consecutive transmissions N for terminal "2" is k is set to 3, the continuous transmission of terminal "2" stops at slot n=3. As a result, the transmission power values ​​of the remaining terminals "3" to "5" in the next slot n=4 are updated to increasing values ​​(step S044), and the received power at base station 1 increases.

[0074] In the subsequent step S043, the number of consecutive transmissions N for terminal "3" is k is set to 4, the continuous transmission of terminal "3" stops at slot n=4. As a result, the transmission power values ​​of the remaining terminals "4" and "5" in the next slot n=5 are updated to increasing values ​​(step S044), and the received power at base station 1 increases.

[0075] In the subsequent step S043, the number of consecutive transmissions N for terminal "4" is k When the number of consecutive transmissions N for terminal "4" is set to 5, the consecutive transmissions for terminal "4" are stopped at slot n=5. Therefore, the transmission power values ​​of the remaining terminal "5" in the next slot n=6 are updated to increasing values ​​(step S044). However, in this embodiment, in the subsequent step S043, the number of consecutive transmissions N for terminal "5" is k is set to 5. In this case, since the continuous transmission of terminal "5" stops at slot n=5, base station 1 does not notify terminal "5" of the transmission power value to be used in slot n=6.

[0076] Therefore, in the example shown in FIG. 13, no signal related to the continuous transmission in slot n=6 is transmitted. Therefore, slot n=6 can be effectively used for other purposes. Furthermore, the number of continuous transmissions for each of terminals "1" to "5" is reduced, so power consumption can be reduced. Furthermore, the transmission power values ​​for terminals "2" to "5" are updated to increase, so the received power and reception quality are improved. In this way, terminals "1" to "5", which are multiple terminals 2, can perform suitable continuous transmissions.

[0077] 15 is a diagram showing an example of an experiment relating to continuous transmission using the wireless communication system according to the embodiment. The environment in the example of the experiment is as follows. ·ISD (Inter-Site Distance: distance between base stations): 1732m NLOS (Non Line Of Sight) environments Maximum transmit power: 23dBm Number of antennas at base station 1: 2 MCS=1

[0078] In the graph on the left side of Figure 15, multiple user IDs (terminals 2) "1" to "6" are arranged in order of decreasing propagation loss. The vertical axis of the graph is the number of continuous transmissions. When the number of continuous transmissions is the same among multiple terminals 2, the minimum, maximum, and average values ​​of the number of continuous transmissions for user IDs "1" to "6" are constant regardless of the propagation loss value. In contrast, as shown in the graph on the right side, when the processing of Figures 8 to 12 is performed for user IDs "1" to "6", the smaller the propagation loss, the smaller the desired number of continuous transmissions becomes. The number of continuous transmissions in the graph on the right side has decreased to a maximum of approximately one-quarter compared to the graph on the left side. The average number of continuous transmissions has also decreased, indicating an improvement.

[0079] <Effects of the embodiment> The wireless communication system according to the embodiment includes a plurality of transmitting stations (terminals 2) that are connected to a wireless communication partner receiving station (base station 1) in a non-orthogonal multiple access manner (FIGS. 1A and 1B). By continuous transmission, the same signal can be transmitted to the base station 1 a predetermined number of times in succession in a predetermined period (slot) common to a plurality of terminals 2 (FIG. 4).

[0080] The information processing device included in the base station 1, i.e., the control device 1b including the processor 11, calculates an initial value of transmission power to be allocated to each of the multiple terminals 2, which increases as the reception quality at the base station 1 improves (the propagation loss decreases) and can ensure the required difference in reception power at the base station 1 (required power difference ΔP) between the terminals 2 (S002 in FIG. 8, FIG. 11). Also, the control device 1b calculates the number of continuous transmissions of the first transmitting station (terminal 2 with k=0) among the multiple terminals 2, which is assigned the largest initial value of transmission power, based on the index value of reception quality at the base station 1 (SINR) (S043 in FIG. 12).

[0081] According to the above-described configuration, the number of continuous transmissions of the terminal 2 with the smallest propagation loss (to which the largest initial value of transmission power is assigned) can be reduced compared to when the number of continuous transmissions of the multiple terminals is set to the same number as the terminal 2 with the largest propagation loss among the multiple terminals 2. This makes it possible to reduce the power consumption of the terminal 2. In other words, it is possible to perform suitable continuous transmissions.

[0082] Furthermore, in the embodiment, the control device 1b or the processor 11 can further execute the following: excluding a terminal 2 (corresponding to a first transmitting station) for which a desired number of continuous transmissions is set from the plurality of terminals 2; and calculating the number of continuous transmissions and the transmission power to be used after the exclusion for each of the remaining terminals 2 (S044 in FIG. 12). This makes it possible to reduce the number of continuous transmissions for the remaining terminals 2. Furthermore, by reducing the number of continuous transmissions, the number of cycles (slots) used for continuous transmission can be reduced, enabling more effective use of resources.

[0083] In the embodiment, the control device 1b or the processor 11 can allocate to each of the remaining terminals 2 a transmission power that is greater than the transmission power allocated before the terminal 2 for which the desired number of consecutive transmissions is set is excluded. By increasing the transmission power, it is possible to improve the reception quality (SINR or error rate) at the base station 1 (S044 in FIG. 12, S033 in FIG. 11).

[0084] In addition, in an embodiment, the control device 1b or the processor 11 can calculate the propagation loss using the received signal strength at the base station 1 when each of multiple terminals 2 transmits a signal to the base station 1 at a predetermined transmission power (Figure 9).

[0085] In addition, in an embodiment, the control device 1b or the processor 11 can calculate the propagation loss using the received signal strength at each of the multiple terminals 2 when the base station 1 transmits a signal to each of the multiple terminals 2 at a predetermined transmission power (Figure 10).

[0086] Furthermore, in the embodiment, the control device 1b or the processor 11 allocates the maximum allocable transmission power to the transmitting station with the best reception quality (terminal 2 with the smallest propagation loss) among the multiple terminals 2 in allocating transmission power. Furthermore, the control device 1b or the processor 11 calculates the transmission power to be allocated to each of the remaining transmitting stations (terminals 2) excluding the transmitting station with the best reception quality, so that the required power difference ΔP is secured within a range of power lower than the maximum transmission power (S034 in FIG. 11).

[0087] In the embodiment, the control device 1b or the processor 11 calculates the reception quality (S(γ)) at different numbers of consecutive transmissions n in calculating the number of consecutive transmissions of the terminal 2 to which the maximum transmission power is assigned among the multiple terminals 2. Then, the control device 1b or the processor 11 determines whether the reception quality obtained by the calculation is equal to or exceeds the desired reception quality (S target ) is determined as the number of consecutive transmissions for the terminal 2 (S043 in FIG. 12).

[0088] In the embodiment, the base station 1, which is the receiving station, can transmit information including the number of consecutive transmissions assigned to each of the plurality of terminals 2 and the transmission power used in each consecutive transmission to each of the plurality of terminals 2 via the downlink control channel (S004 in FIG. 8). This allows each of the plurality of terminals 2 to perform consecutive transmissions using the transmission power according to the information.

[0089] The processes and means described in this disclosure can be freely combined and implemented as long as no technical contradictions arise. Furthermore, a process described as being performed by one device may be shared and executed by multiple devices. Alternatively, a process described as being performed by different devices may be executed by one device. In a computer system, the hardware configuration (server configuration) by which each function is realized can be flexibly changed.

[0090] The present disclosure can also be realized by providing a computer program implementing the functions described in the above embodiments to a computer, and having one or more processors in the computer read and execute the program. Such a computer program may be provided to the computer via a non-transitory computer-readable storage medium connectable to the computer's system bus or via a network. Non-transitory computer-readable storage media include, for example, any type of disk, such as a magnetic disk (e.g., a floppy disk, a hard disk drive (HDD), etc.), an optical disk (e.g., a CD-ROM, a DVD disk, a Blu-ray disk), a read-only memory (ROM), a random-access memory (RAM), an EPROM, an EEPROM, a magnetic card, a flash memory, an optical card, or any type of medium suitable for storing electronic instructions. [Explanation of symbols]

[0091] 1...Base station 1a, 2a... Radio (radio processing device) 1b, 2b...Control device 2. Terminal 10,20...antenna 11,21... Processor 12,22...Storage device 13,23 Internal Interface 14,24... Network Interface 101 Demultiplexer 110,210...RS section 111,121...Integrator part 112 Communication channel estimation unit 120,220...DS section 122 Replica removal unit 123 Demodulation section 124 Decoding section 126... Replica generation unit 127...Encoding section 128... Modulation section 129... multiplication unit 202 Multiplexer 220...DS section 221...encoding section 222 Modulation section

Claims

1. A base station including a control device and a radio, the radio device receives a reference signal from each of a plurality of terminals including a first terminal and a second terminal; the control device executes a process of estimating, for each of the plurality of terminals, a reception quality of a transmission from each of the plurality of terminals based on the reference signal, and determining a transmission power for transmitting an uplink signal by each of the plurality of terminals based on the estimated reception quality; In the process, the first terminal determines a first transmit power for transmitting an uplink signal; determining a second transmission power for the second terminal to transmit an uplink signal based on the estimated reception quality and the determined first transmission power, and repeating a process of determining transmission powers with the second transmission power as the first transmission power and the remaining terminals of the plurality of terminals as second terminals in sequence; The base station, wherein the radio device transmits information indicating the determined transmission power to each of the plurality of terminals.

2. the radio receives uplink signals transmitted using Non-orthogonal Multiple Access (NOMA) from each of a plurality of terminals; The base station of claim 1 .

3. the control device determines, for each of the plurality of terminals, a number of times for the terminal to repeatedly transmit an uplink signal based on the estimated reception quality; The wireless device transmits information indicating the determined number of times to the terminal. The base station according to claim 1 or 2.

4. The control device allocates resources for each of the plurality of terminals to transmit the uplink signal by using a configured grant (CG). assign a A base station according to any one of claims 1 to 3.

5. a difference between the determined first transmission power and the determined second transmission power is equal to or greater than a predetermined power difference; The base station of claim 1 .

6. the radio device transmits, to each of the plurality of terminals, information indicating a slot in which the terminal starts to repeatedly transmit the uplink signal; A base station according to any one of claims 1 to 5.

7. the radio device transmits, to each of the plurality of terminals, information indicating a frequency channel used by the terminal to repeatedly transmit the uplink signal; A base station according to any one of claims 1 to 6.

8. A communication system having a base station including a control device and a radio device, and a plurality of terminals including a first terminal and a second terminal, the wireless device receives a reference signal from each of the plurality of terminals; the control device estimates a reception quality of a transmission from each of the plurality of terminals based on the reference signal, and executes a process of determining a transmission power for transmitting an uplink signal by each of the plurality of terminals based on the estimated reception quality; In the process, the first terminal determines a first transmit power for transmitting an uplink signal; determining a second transmission power for the second terminal to transmit an uplink signal based on the estimated reception quality and the determined first transmission power, and repeating a process of determining transmission powers with the second transmission power as the first transmission power and the remaining terminals of the plurality of terminals as second terminals in sequence; the wireless device transmits information indicating the determined transmission power to each of the plurality of terminals; each of the plurality of terminals determines a transmit power for transmitting the uplink signal based on the received information; transmitting the uplink signal to the base station using the determined transmit power.

9. A difference between the determined first transmission power and the determined second transmission power is equal to or greater than a predetermined power difference.

9. The communication system of claim 8.

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