Transmission power control method, terminal, and wireless communication system

Abstract

To make it possible to ensure, when terminals transmit signals to two respective base stations, an appropriate reception power difference between the terminals in each base station.SOLUTION: There is provided a transmission power control method for a terminal capable of transmitting a first signal received by a first base station and a second signal received by a second base station by power-domain non-orthogonal multiple access. In a case where reception power is divided into at least two ranks at equal intervals, each of the at least two ranks has an allowable variation range having an identical size, a margin is defined between a lower limit of the allowable variation range in an upper rank and an upper limit of the allowable variation range in a lower rank in the at least two ranks, and where a size of the allowable variation range is equal to or larger than a size of the margin, the terminal adjusts transmission power of the first signal and the second signal by using a transmission power adjustment amount calculated such that reception power of the first signal and reception power of the second signal fall within the allowable variation range of any of the at least two ranks by using the reception power of the first signal, the reception power of the second signal, a reception power difference therebetween, the at least two ranks, the allowable variation range, and the margin.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present invention relates to a transmission power control method, a terminal, and a wireless communication system.

Background Art

[0002] With the increase in the number of terminals used in the Internet of Things (IoT), there is concern about the congestion of the uplink. In order to increase the number of terminals that can be connected in the uplink, the application of Power-Domain Uplink Non-orthogonal Multiple Access (PD-UL-NOMA) targeting the uplink in the power domain is expected. Also, in an environment where the communication environment fluctuates greatly such as during mobile communication, a distributed base station configuration in which a plurality of base stations are arranged in a cell is being considered to improve the communication quality of the uplink.

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In NOMA, a signal in which a plurality of signals with different received powers are superimposed is received, and each signal is separated from the superimposed signal and decoded. For proper separation, it is required that a sufficient difference in received power be provided between the signals.

[0005] In a distributed base station configuration using PD-UL-NOMA, it is conceivable that each of a plurality of terminals existing in a cell transmits a signal to two distributed base stations. Regarding the distributed base station configuration using PD-UL-NOMA, currently, a terminal transmission power control method within a cell has not been proposed. For this reason, for example, when there are two distributed base stations, it is conceivable to adjust the transmission power so that the difference in received power between terminals becomes appropriate for one of the base stations. However, even if the difference in received power between terminals at one of the distributed base stations is appropriately set, the difference in received power between terminals at the other distributed base station may be insufficient, and a sufficient difference in received power may not be ensured at the other base station, potentially preventing proper signal separation and decoding.

[0006] An object of the present disclosure is to provide a transmission power control method, a terminal, and a wireless communication system that can ensure an appropriate difference in received power between terminals at each base station for a terminal that transmits signals to each of two base stations.

Means for Solving the Problem

[0007] One aspect of the present disclosure is a transmission power control method for a terminal capable of transmitting a first signal received by a first base station and a second signal received by a second base station by power domain non-orthogonal multiple access, wherein the terminal has a received power divided into two or more ranks at equal intervals, each of the two or more ranks has an allowable fluctuation range of the same size, and for adjacent upper and lower ranks among the two or more ranks, a margin is defined between the lower limit of the allowable fluctuation range in the upper rank and the upper limit of the allowable fluctuation range in the lower rank, and when the size of the allowable fluctuation range is equal to or greater than the size of the margin, the received power of the first signal, the received power of the second signal, the first signal and the second Using the received power difference from the signal, two or more ranks, the allowable variation range, and the margin, calculate the transmission power adjustment amounts for the first signal and the second signal so that the received power of each of the first signal and the second signal falls within the allowable variation range of any of the two or more ranks, and adjust the transmission powers of the first signal and the second signal at the terminal using the transmission power adjustment amounts. This is a transmission control method.

[0008] One of the other aspects of the present disclosure is a terminal capable of transmitting a first signal received by a first base station and a second signal received by a second base station by power domain non-orthogonal multiple access. The received power is divided into two or more ranks at equal intervals, each of the two or more ranks has an allowable variation range of the same size, and for adjacent upper and lower ranks among the two or more ranks, a margin is defined between the lower limit of the allowable variation range in the upper rank and the upper limit of the allowable variation range in the lower rank. When the size of the allowable variation range is equal to or greater than the size of the margin, using the received power of the first signal, the received power of the second signal, the received power difference between the first signal and the second signal, two or more ranks, the allowable variation range, and the margin, calculate the transmission power adjustment amounts for the first signal and the second signal so that the received power of each of the first signal and the second signal falls within the allowable variation range of any of the two or more ranks, and include a control unit that adjusts the transmission powers of the first signal and the second signal at the terminal using the transmission power adjustment amounts.

[0009] One aspect of other embodiments of the present disclosure includes a first base station, a second base station, and a terminal capable of transmitting a first signal received by the first base station and a second signal received by the second base station through power domain non-orthogonal multiple access. The terminal divides the received power into two or more ranks at equal intervals, each of the two or more ranks has an allowable variation width of the same size, and for adjacent upper and lower ranks among the two or more ranks, a margin is defined between the lower limit of the allowable variation width in the upper rank and the upper limit of the allowable variation width in the lower rank. When the size of the allowable variation width is greater than or equal to the size of the margin, the received power of the first signal, the received power of the second signal, the received power difference between the first signal and the second signal, the two or more ranks, the allowable variation width, and the margin are used to calculate the transmission power adjustment amounts of the first signal and the second signal so that the received power of each of the first signal and the second signal falls within the allowable variation width of any of the two or more ranks, and a control unit that adjusts the transmission power of the first signal and the second signal at the terminal using the transmission power adjustment amounts. It is a wireless communication system.

Advantages of the Invention

[0010] According to the present disclosure, for a terminal that transmits signals to each of two base stations, it is possible to ensure an appropriate received power difference between terminals at each base station.

Brief Description of the Drawings

[0011]

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Mode for Carrying Out the Invention

[0012] In the embodiment, a transmission power control method for a terminal capable of transmitting a first signal received by a first base station and a second signal received by a second base station by power domain non-orthogonal multiple access (PD-NOMA) will be described. In this transmission power control method, the received power is divided into two or more ranks at equal intervals, each of the two or more ranks has an allowable variation width of the same size, and for adjacent upper and lower ranks among the two or more ranks, a margin is defined between the lower limit of the allowable variation width in the upper rank and the upper limit of the allowable variation width in the lower rank, and the size of the allowable variation width is equal to or greater than the size of the margin. The terminal uses the received power of the first signal, the received power of the second signal, the received power difference between the first signal and the second signal, two or more ranks, the allowable variation width, and the margin to calculate the transmission power adjustment amounts of the first signal and the second signal so that the received power of each of the first signal and the second signal falls within the allowable variation width of any of the two or more ranks. Then, the terminal adjusts the transmission powers of the first signal and the second signal at the terminal using the transmission power adjustment amounts.

[0013] According to the transmission power control method, the transmission powers of the first signal and the second signal are adjusted so that the received power of the first signal and the received power of each of the second signals fall within the allowable variation width of any of the two or more ranks. By each terminal connected to the first and second base stations performing such an operation, each of the first and second base stations can receive a superimposed signal from each terminal with an appropriate received power difference ensured. That is, for a terminal that transmits a signal to each of the two base stations, an appropriate received power difference between terminals can be ensured at each base station.

[0014] In the transmission power control method according to the embodiment, the size of the allowable variation range and the size of the margin may be equal, and the interval between two or more ranks may be defined by a value obtained by doubling the sum of the size of the allowable variation range and the size of the margin. The size of the allowable variation range only needs to be equal to or greater than the margin, but if such a configuration is adopted, it becomes possible to give an accurate power difference.

[0015] The transmission power control method according to the embodiment may adopt the following configuration. That is, when the reception power difference between the first signal and the second signal is smaller than the allowable variation range, the terminal specifies, from among two or more ranks, the rank closest to the first reception power, which is the reception power with the larger value, of the reception power of the first signal and the reception power of the second signal. Then, the terminal calculates a transmission power adjustment amount so that the reception power of the first signal and the reception power of the second signal fall within the allowable variation range of the closest rank. In this way, a sufficient power difference can be ensured.

[0016] The transmission power control method according to the embodiment may adopt the following configuration. That is, when the remainder obtained by dividing the reception power difference between the first signal and the second signal by twice the sum of the size of the allowable variation range and the size of the margin is smaller than the sum value, the terminal specifies, from among two or more ranks, the rank closest to the first reception power, which is the reception power with the larger value, of the reception power of the first signal and the reception power of the second signal. Further, the terminal calculates, as the transmission power adjustment amount for the first reception power, a value obtained by adding or subtracting half of the remainder to or from the value obtained by subtracting the first reception power from the reception power of the closest rank. Then, the terminal 10 calculates the transmission power adjustment amount for the second reception power, which is the reception power with the smaller value, of the reception power of the first signal and the reception power of the second signal, from the transmission power adjustment amount for the first reception power and the reception power difference. In this way, a sufficient power difference can be ensured.

[0017] The transmission power control method according to the embodiment may adopt the following configuration. That is, when the received power difference between the first signal and the second signal is greater than or equal to the allowable variation range and less than or equal to twice the sum of the size of the allowable variation range and the size of the margin, the terminal determines, from among ranks 2 and above, the rank closest to the first received power, which is the larger of the received power of the first signal and the received power of the second signal. Further, the terminal calculates the transmission power adjustment amounts for the first received power and the second received power such that the first received power falls within the allowable variation range of the closest rank and the second received power, which is the smaller of the received power of the first signal and the received power of the second signal, falls within the allowable variation range of a rank lower than the closest rank. In this way, a sufficient power difference can be ensured.

[0018] The transmission power control method according to the embodiment may adopt the following configuration. That is, when the remainder obtained by dividing the received power difference between the first signal and the second signal by twice the sum of the size of the allowable variation range and the size of the margin is greater than the sum value, the terminal determines, from among ranks 2 and above, the rank closest to the first received power, which is the larger of the received power of the first signal and the received power of the second signal. Further, the terminal calculates, as the transmission power adjustment amount for the first received power, a value obtained by adding or subtracting half of the value obtained by subtracting the remainder from twice the sum value to the value obtained by subtracting the first received power from the received power of the closest rank. Then, the terminal calculates the transmission power adjustment amount for the second received power, which is the smaller of the received power of the first signal and the received power of the second signal, from the transmission power adjustment amount for the first received power and the received power difference. In this way, a sufficient power difference can be ensured.

[0019] The transmission power control method according to the embodiment may adopt the following configuration. That is, the terminal determines the sum of the number of connected terminals for the first rank, which is the sum of the number of connected terminals to the first base station and the number of connected terminals to the second base station, from the information indicating the sum for each rank of 2 or more. Also, the terminal calculates the sum of the second rank, which is the sum of the number of connected terminals to the first base station and the number of connected terminals to the second base station for each lower rank up to a predetermined rank when the rank to which the reception power of each of the first signal and the second signal belongs is lowered by 1 or 2 or more ranks lower. Further, when the average value of the sum of the first rank and the sum of the second rank for each lower rank is exceeded by the sum of the first rank, the terminal determines with a first probability to shift the rank to which the reception power of each of the first signal and the second signal belongs to a lower rank where the sum of the second rank is smaller than the average value. Then, the terminal reduces the transmission power of the first signal and the second signal according to the shift to the lower rank. In this way, when the sum of the number of connected terminals transmitting signals at the same rank as the rank of the first signal and the second signal transmitted by the terminal is more than the average value, the number of connected terminals shifts to a rank lower than the average value with the first probability, so that the possibility (probability) that the first signal and the second signal collide with signals from other terminals (connected terminals) (a sufficient power difference cannot be ensured) can be reduced.

[0020] The transmission power control method according to the embodiment may adopt the following configuration. That is, the terminal calculates the first probability by dividing the value obtained by subtracting the average value from the sum of the first rank by the sum of the first rank. In this way, the terminal can be shifted with a suitable probability to reduce the number of connected terminals and the possibility of collision.

[0021] The transmission power control method according to the embodiment may adopt the following configuration. That is, when there are two or more lower ranks where the sum of the second ranks is smaller than the average value, the terminal calculates the absolute value of the sum of the values obtained by subtracting the average value from the sum of the second ranks in each of the two or more lower ranks, and for each of the two or more lower ranks, calculates the value obtained by dividing the value obtained by subtracting the average value from the sum of the second ranks by the absolute value as the probability that each of the two or more lower ranks is selected as the migration destination. In this way, the migration destinations of the terminals can be properly dispersed.

[0022] The embodiments of the present disclosure may include a terminal that performs transmission power control using the above-described transmission power control method, and a wireless communication system including such a terminal. Further, the embodiments of the present disclosure may also include a program for implementing the transmission power control method, which is executed by an information processing apparatus such as a terminal, and a non-transitory computer-readable recording medium storing the program.

[0023] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The configurations of the following embodiments are examples, and the present disclosure is not limited to the configurations of the embodiments.

[0024] <Wireless communication system> FIG. 1 is a diagram showing a configuration example of a wireless communication system according to an embodiment. The wireless communication system includes a plurality of base stations 11 existing in cell 1 and a plurality of (one or two or more) terminals 10 that can communicate by connecting to each base station 11.

[0025] When each of the plurality of terminals 10 transmits data such as IoT-related data obtained by a sensor to a predetermined destination, uplink communication using PD-UL-NOMA is performed. For example, in FIG. 1, the plurality of base stations 11 operate as two distributed base stations DB1 and DB2. For example, each of the terminals 10A, 10B, and 10C included in the plurality of terminals 10 transmits a wireless signal as a first signal to the distributed base station DB1 and transmits a wireless signal as a second signal to the distributed base station DB2. In the following description, when the terminal is not specified, the notation "terminal 10" is simply used.

[0026] Each of the distributed base stations DB1 and DB2 receives signals (first and second signals) transmitted in parallel from terminals 10A, 10B, and 10C. Each of the distributed base stations DB1 and DB2 is connected to the control station, receives a superimposed signal in which the signals transmitted from terminals 10A, 10B, and 10C are superimposed, and sends it to the control station. The control station uses successive interference cancellation (SIC) to separate and decode the signals from each of terminals 10A, 10B, and 10C from the superimposed signal, thereby obtaining the data from each of terminals 10A, 10B, and 10C. The control station processes the first signal and the second signal separately so that normal data can be obtained from either one of the first signal and the second signal. From, the data from each of terminals 10A, 10B, and 10C can be obtained. The control station processes the first signal and the second signal separately so that normal data can be obtained from either one of the first signal and the second signal.

[0027] Figure 2 shows the received power of signals from a plurality of terminals 10 received by a certain base station 11. As a condition for enabling communication in PD-UL-NOMA, a necessary power difference (margin) x m is required between the received powers of the signals from each terminal 10. In PD-UL-NOMA, the base station 11 communicates with each terminal 10 so that a power difference x m occurs in the received power of the signal from each received terminal 10.

[0028] In the example shown in Figure 2, for example, the power difference between the received power of the signal from terminal 10C and the received power of the signal from terminal 10B is x m or more. In this case, since the signals can be properly separated and decoded by SIC, terminal 10C is in a state where it can communicate with base station 11.

[0029] On the other hand, in the example shown in Figure 2, the power difference between the received power of the signal from terminal 10B and the received power of the signal from terminal 10A is x m is smaller. In this case, proper signal separation and decoding cannot be performed due to interference between the signals, and terminals 10B and 10A are in a state where they cannot communicate with base station 11.

[0030] Note that the margin xm Examples of elements for determining the size include, for example, packet error rate (PER), communication bandwidth, modulation method, or error correction method, etc.

[0031] FIG. 3 is an explanatory diagram showing an example of transmission power control in a certain base station 11. As shown in FIG. 3, it is conceivable that each terminal 10 performs transmission power control of a signal so that the received power is segmented in units of margin x m In this case, the maximum receivable power P max is determined by limiting factors such as the input power limit of the amplifier or the number of quantization bits. Also, the minimum receivable power P min is determined by, for example, the signal-to-noise power ratio (SNR) that enables communication.

[0032] Next, consider the case where the wireless communication system has a distributed base station configuration using PD-UL-NOMA. For example, in the example shown in FIG. 1, as described above, each of terminals 10A, 10B, and 10C transmits signals in parallel to each of distributed base stations DB1 and DB2. Each of distributed base stations DB1 and DB2 receives a signal in which the signals from terminals 10A, 10B, and 10C are superimposed.

[0033] Here, for example, as shown in FIG. 4A, in order to ensure an appropriate received power difference, it is conceivable that each of terminals 10A, 10B, and 10C performs transmission power control so that a power difference of x dB occurs between the signals received by distributed base station DB1. However, even if such transmission power control is performed, in the superimposed signal received by distributed base station DB2, as shown in FIG. 4B, a sufficient power difference cannot be obtained between terminal 10B and terminal 10C, and there is a possibility of communication failure. The terminal 10 according to the embodiment is provided with a configuration for solving such a problem.

[0034] Figures 5 to 11 are explanatory diagrams of a transmission power control method for a terminal according to an embodiment. As described above, in the case of a distributed base station configuration, two signals transmitted from one terminal 10 (each of terminals 10A, 10B, and 10C) are received by two distributed base stations DB1 and DB2. Figure 5 shows the received power P1 of the signal transmitted from one terminal 10 to the distributed base station DB1 and the received power P2 of the signal transmitted to the distributed base station DB1. The power difference ΔP between these two signals P1 and P2 is fixed regardless of the magnitude of the transmission power.

[0035] Therefore, as shown in Figure 5, a reception rank is set (specified) for the received power, and it is prohibited that the received power from the terminal 10 falls within the allowable variation range (hereinafter referred to as the "allowable range") of the received power of each reception rank and the received power of the terminal 10 is located in other regions (margins). In other words, in the transmission power control method according to the embodiment, a margin x m is provided in addition to the allowable range x h so that the required power difference for PD-UL-NOMA can be obtained for any ΔP. Then, transmission power control (adjustment (increase or decrease) of the transmission power) is performed so that each of the received powers of the two signals moves up and down while maintaining ΔP between the signals and enters the allowable range.

[0036] As a result, the number of terminals 10 capable of superimposing signals decreases, but the required power difference for PD-UL-NOMA can be obtained. Therefore, the signals from each terminal 10 can be preferably separated and decoded. That is, effects such as enabling communication between the base station 11 and the terminal 10 or improving the communication quality between the two can be obtained.

[0037] As shown in Figure 6, the received power at the base station 11 is divided by a plurality (N (N is an integer of 1 or more)) of reception ranks a1, a2,..., a N . Each reception rank has a received power value (P(a1) to P(a N )) and has an allowable range x h centered on this received power value. The allowable range x h is equally divided by the received power value of the reception rank and is plus or minus x from the received power value.h is defined within the range of / 2. Margin x m is provided between the lower limit of the tolerance range in the higher received rank and the upper limit of the tolerance range in the lower received rank among two adjacent received ranks. Then, transmission power control is performed at the terminal 10 so that the received powers of two signals transmitted from one terminal 10 fall within the tolerance range of any received rank.

[0038] Tolerance width x h is set to be equal to or larger than the size of margin x m For example, as shown in FIG. 7, there is a case where one of the two signals falls within margin x m . Generally, when tolerance width x h is smaller than margin x m and ΔP = (x h + x m ) / 2, the received power of one of the two signals falls within any margin of the distributed base station. Therefore, tolerance width x h is defined to be equal to or larger than margin x m . However, the smaller the tolerance width x h , the more accurate the power difference is given. Therefore, it is preferable that the size of tolerance width x h is equal to the size of margin x m .

[0039] Therefore, as shown in FIG. 6, in the present embodiment, tolerance width x h = margin x m = X is set, and the received power difference between adjacent received ranks is defined as 2X. As an example, the received power P(a1) of the topmost received rank a1 is set to, for example, -50 dBm, X = 4 dB is set, and the received power is set to decrease by -8 dBm every time the received rank goes down by one. However, the value of the topmost received rank and the value of X are not limited to the above.

[0040] FIG. 8 shows an example of a transmission power control method when the difference in received power ΔP = (|P1 - P2|) < X. P1 is the received power of a signal (first signal) that the distributed base station DB1 receives from the terminal 10A, and P2 is the received power of a signal (second signal) that the distributed base station DB2 receives from the terminal 10A (see FIG. 1).

[0041] In the case shown in FIG. 8, the received power P1 of the signal received by the distributed base station DB1 from the terminal 10A is P M is the margin x between the receiving rank a2 and the receiving rank a3 m In this case, the terminal 10 is M In FIG. 8, the reception power P(a3) and P M The difference between the received power P(a2) and P M Therefore, the reception rank a3 is identified as the closest rank.

[0042] The terminal 10A is ΔP T =P(a3)-P M +ΔP / 2 is the transmission power adjustment value ΔP T Calculate ΔP T In other words, the transmission power of the signal (first signal) for distributed base station DB1 is controlled so that P1 is changed to a position higher than the reception power P(a3) of reception rank a3 by ΔP / 2. Also, since ΔP is fixed, the transmission power of the signal (second signal) for distributed base station DB2 is controlled so that P2 is changed to a position lower than the reception power P(a3) of reception rank a3 by ΔP / 2 in accordance with the change in P1.

[0043] As a result, the reception power of the signal received by the distributed base station DB1 from the terminal 10A falls within the allowable range of the reception rank a2 in the distributed base station DB1. Also, the reception power of the signal received by the distributed base station DB2 from the terminal 10A falls within the allowable range of the reception rank a3 in the distributed base station DB2. ΔP <Xであるため、二つの信号の受信電力は必ず許容幅x h Go inside.

[0044] Figure 9 generalizes the case of Figure 8 and shows the case where the remainder ΔP’ = mod(ΔP, 2X) obtained by dividing the power difference ΔP by 2X is smaller than X. In the case shown in Figure 9, ΔP T = P(a2) - P M + ΔP’ / 2 (where P1 = P M ), and the transmission power adjustment value ΔP T is obtained. The terminal 10 performs transmission power control so that the received power of each of the two signals decreases by ΔP T . As a result, the received power of the signal received by the distributed base station DB1 from the terminal 10A falls within the allowable range of the reception rank a2 in the distributed base station DB1. Also, the received power of the signal from the terminal 10A received by the distributed base station DB2 falls within the allowable range of the reception rank a3 in the distributed base station DB2.

[0045] Figure 10 shows the case where the power difference ΔP is equal to or greater than X and less than or equal to 2X. In the case shown in Figure 10, ΔP T = P(a2) - P M - (2X - ΔP) / 2 (where P1 = P M ), and the transmission power adjustment value ΔP T is obtained. The terminal 10 performs transmission power control so that the received power of each of the two signals increases by ΔP T . That is, the transmission power control of the signal (the first signal) for the distributed base station DB1 is performed so that P1 is changed (increased) to a position that is (2X - ΔP) / 2 lower from the received power P(a2) of the nearest reception rank a2. Also, since ΔP is fixed, along with the change in P1, the transmission power control of the signal (the second signal) for the distributed base station DB2 is performed so that P2 is changed (increased) to a position that is ΔP / 2 higher than the received power P(a3) of the reception rank a3. Thus, when the transmission power is adjusted in the upward direction by transmission power control, P M is changed to a position that is lower from the received power of the nearest reception rank. On the other hand, when the transmission power is adjusted in the downward direction by transmission power control, P M is changed to a position that is higher from the received power of the nearest reception rank (see Figure 8).

[0046] As a result, the received power of the signal received by the distributed base station DB1 from the terminal 10A falls within the allowable range of the reception rank a2 in the distributed base station DB1. Also, the received power of the signal from the terminal 10A received by the distributed base station DB2 falls within the allowable range of the reception rank a3 in the distributed base station DB2.

[0047] FIG. 11 generalizes the case of FIG. 10 and shows the case where the above-mentioned excess ΔP’ is X or more and 2X or less. In the case shown in FIG. 10, ΔP T =P(a2)-P M -(2X - ΔP’) / 2 operation (where P1 = P M ) is used to obtain the transmission power adjustment value ΔP T . The terminal 10 performs transmission power control so that the received power of each of the two signals increases by ΔP T . As a result, the received power of the signal received by the distributed base station DB1 from the terminal 10 falls within the allowable range of the reception rank a2 in the distributed base station DB1, and the received power of the signal received by the distributed base station DB2 from the terminal 10A falls within the allowable range of the reception rank a3 in the distributed base station DB2.

[0048] FIG. 12 is a diagram showing a configuration example of the terminal 10 according to the embodiment. In FIG. 12, the terminal 10 includes a processor 31 (an example of a control unit), a storage device 32, a communication interface (communication IF) 33, an input device 34, and a display 35, which are interconnected via a bus B.

[0049] The storage device 32 includes a main storage device and an auxiliary storage device. The main storage device is used, for example, as a storage area for programs and data, a working area for the processor 31, or a buffer area for temporarily storing communication data. The main storage device is composed of, for example, a RAM (Random Access Memory), or a combination of a RAM and a ROM (Read Only Memory). The auxiliary storage device is used for storing programs and data. The auxiliary storage device is a hard disk, an SSD (Solid State Drive), an EEPROM (Electrically Erasable Programmable Read-Only Memory), or the like. However, the type of the storage device 32 is not limited to the above examples.

[0050] The communication IF 33 is a communication circuit that supports a predetermined wireless communication standard such as 5G. The communication IF 33 is connected to an antenna 33a that transmits and receives wireless signals, can generate wireless signals that comply with PD-UL-NOMA, and transmit the wireless signals to each of the distributed base stations DB1 and DB2.

[0051] The input device is, for example, a key, a button, or a pointing device, etc., and is used for inputting information and data. The display 35 is used for displaying information and data.

[0052] The processor 31 is, for example, a Central Processing Unit (CPU) or a Microprocessor Unit (MPU). The processor 31 is not limited to a single processor and may have a multi-processor configuration. Also, a single physical CPU connected by a single socket may have a multi-core configuration. Furthermore, the processor 31 may include processors other than the CPU, such as a Digital Signal Processor (DSP) or a Graphics Processing Unit (GPU). Also, the processor 31 may cooperate with an integrated circuit (IC), other digital circuits, or analog circuits. The integrated circuit is, for example, a large-scale integration (LSI), an Application Specific Integrated Circuit (ASIC), or a programmable logic device (PLD). The PLD includes, for example, a Field-Programmable Gate Array (FPGA). The processor 31 may be a circuit called, for example, a microcontroller (MCU ), a System-on-a-chip (SoC), a system LSI, or a chipset, etc.

[0053] The processor 31 controls the transmission power of the signal transmitted to the distributed base station by using the above-described transmission power control method by executing a program. FIG. 13 is a flowchart showing an example of the processing of the terminal 10 according to the embodiment. The processing of the flowchart shown in FIG. 13 is performed when the terminal 10 transmits data.

[0054] In step S001, the processor 31 of the terminal 10 receives information for calculating the reception power of the signal from the terminal 10 at each of a plurality of base stations 11 communicable with the terminal 10, and uses the information to determine the reception power P1 of the signal from the terminal 10 at the base station 11 corresponding to the distributed base station DB1 and the reception power P2 of the signal from the terminal 10 at the base station 11 corresponding to the distributed base station DB2.

[0055] In step S002, the processor 31 determines whether the received power P1 is greater than the received power P2. If it is determined that the received power P1 is greater than the received power P2, the process proceeds to step S003; otherwise, the process proceeds to step S004. In step S003, the value of P1 is set to P M In step S004, the value of P2 is set to P M .

[0056] In step S005, the processor 31 obtains the received power P(a M ), the power difference ΔP, and the remainder ΔP'. The received power P(a M ) indicates the received power closest to P M . ΔP and ΔP' are as described above.

[0057] In step S006, the processor 31 determines whether ΔP' is less than X = x m . At this time, if it is determined that ΔP' is less than X, the process proceeds to step S007; otherwise, the process proceeds to step S008.

[0058] In step S007, when ΔP' < X, the transmission power adjustment value ΔP T is calculated, and transmission power control is performed using the calculated ΔP T . In step S008, when ΔP' < X, the transmission power adjustment value ΔP T is calculated, and transmission power control is performed using the calculated ΔP T .

[0059] Note that in the calculation formula of step S007 shown in FIG. 13, it is assumed that the received power of the closest received rank is less than P M , and it is "+ΔP' / 2". On the other hand, when the received power of the closer received rank is greater than P M , it is "-ΔP' / 2". Also, in the calculation formula of step S008, when the received power of the closest received rank is P M ​Since it is larger, it is “-X + ΔP’ / 2”. However, when the received power of the nearest received rank is greater than P M it is “+X - ΔP’ / 2”.

[0060] In step S009, the processor 31 determines whether there is margin in the transmission power. If it is determined that there is margin in the transmission power, the process proceeds to S010, and if not, the process proceeds to step S012.

[0061] When the process proceeds to step S010, the processor 31 calculates ΔP T_max (steps S010 and S011). Here, P max max represents the maximum value of the transmission power that can be increased and ΔP T_max is the transmission power adjustment value that can maximize the transmission power. When there is margin in the power the processor 31 calculates the transmission power adjustment amount so as to obtain the maximum received rank within the range of P max (steps S010 and S011). Here, P .

[0062] In step S012, the processor 31 performs transmission power control using the transmission power adjustment value ΔP T or ΔP T_max . That is, the processor 31 changes ( increases or decreases) the transmission power used for signal transmission from the terminal 10 to the distributed base stations DB1 and DB2 according to ΔP T or ΔP T_max . As a result, the received power of the signal from the terminal 10 at the distributed base stations DB1 and DB2 falls within the allowable range x . h .

[0063] The process shown in FIG. 13 is performed for each of the terminals 10A, 10B, and 10C in the example shown in FIG. 1. At this time, at each of the distributed base stations DB1 and DB2, the margin x mTransmission power is adjusted for each of terminals 10A, 10B, and 10C so that signals (superimposed signals) from terminals 10A, 10B, and 10C having the above reception power difference are received. As a premise of the process shown in FIG. 13, the initial values (transmission power before adjustment) and ΔP of the transmission power of the first and second signals used by terminals 10A, 10B, and 10C are determined in advance. Alternatively, terminals 10A, 10B, and 10C may receive an instruction to transmit at a transmission power such that a sufficient reception power difference (see FIG. 4A) is ensured from a distributed base station DB1 or the like.

[0064] Once the transmission power for the distributed base station DB1 is determined, since ΔP is fixed, the transmission power for the distributed base station DB2 is also determined. Information for calculating the reception power for signals transmitted to the distributed base stations DB1 and DB2 at such transmission power is received from the distributed base stations DB1 and DB2, and the reception powers P1 and P2 are calculated in step S001. However, the method by which terminals 10A, 10B, and 10C transmit signals having a power difference may be other than the above.

[0065] Each of a plurality of terminals 10 that transmit signals to the distributed base stations DB1 and DB2 in parallel performs the process shown in FIG. 13, and the reception rank of the signals in each terminal 10 is determined. Such information is managed by the control stations of the distributed base stations DB1 and DB2 and is supplied from one of the distributed base stations DB1 and DB2 to each terminal 10.

[0066] FIG. 14A is a diagram showing an example of the connection number information supplied to terminal 10. In FIG. 14A, the connection number information shows, for each reception rank, the number of terminals 10 connected to the distributed base station DB1 and the number of terminals 10 connected to the distributed base station DB2. The connection number indicates the number of connections per unit time and is calculated on the assumption that each terminal 10 transmits a signal at a probability of J times per unit time according to a Poisson distribution.

[0067] FIG. 14B is a diagram showing an example of reception rank collision. In the example shown in FIG. 14B, for a certain reception rank a MThe tolerance range shows a collision caused by the received power of terminal 10A connected to distributed base station DB1 and the received power of terminal 10B connected to distributed base station DB1. Also, as another example, reception rank a M+1 The tolerance range shows a collision caused by the received power of terminal 10A connected to distributed base station DB2 and the received power of terminal 10C connected to distributed base station DB2. When a collision occurs, the decoding of terminal 10 related to the collision cannot be performed normally, and communication becomes impossible. In the distributed base station configuration, if no collision occurs for the signal received by either one of distributed base stations DB1 and DB2, normal decoding (communication) of that signal becomes possible.

[0068] Figures 15 to 17 are explanatory diagrams of a method for reducing the possibility of collision between terminals in a distributed base station according to an embodiment. Figure 15 is a diagram showing connection number information and the sum of the number of terminals connected to two distributed base stations. The terminal 10 according to the embodiment performs the following processing in order to reduce the possibility that the transmission signal from its own terminal causes a collision by using the connection number information.

[0069] In the example shown in Figure 15, in the set of reception ranks, the reception rank of the signal transmitted from terminal 10A at distributed base station DB1 is reception rank a M and the reception rank at distributed base station DB2 is reception rank a which is 2 ranks lower than the reception rank at distributed base station DB1 M+2 is shown. The connection number of reception rank a M is 500, the connection number of reception rank a M+2 is 500, and their sum (total value) Y d is 1000. When the rank of the above-mentioned set of reception ranks is lowered by 1 due to a decrease in transmission power, the reception rank at distributed base station DB1 becomes reception rank a M+1 and the reception rank at distributed base station DB2 becomes reception rank a M+3 . The sum Y d of the connection numbers in this set of reception ranks becomes 500. In this way, when the rank of the set of reception ranks is lowered by 2 to 4, the sum Y d of the connection numbers becomes 300, 200, and 100. Sum Y dThe smaller the number, the lower the probability of a collision occurring.

[0070] Therefore, the terminal 10 determines whether it is necessary to shift to a lower rank of the reception rank and determines the reception rank of the destination when shifting is necessary. For these processes, the sum Y as shown in FIG. 16 d The average value Y of ave And the difference Δy from the average value d =Y d -Y ave And the probability of shifting to a lower reception rank (shifting probability) P o =(Y d -Y ave ) / Y d And the probability of coming from a higher reception rank and shifting Rate (probability of being shifted) P I =-ΔY d / Z sum And are obtained. -ΔY d Is the absolute value of ΔY with a negative value d Of Indicates the absolute value, and Z sum Is the sum (total value) of the absolute values of Δy with a negative value d Is. Also, FIG. The connection number table shown in 15 and the table showing the relationship between the order of ranks and the sum Y of the connection numbers d Can be generalized in the characters shown in FIG. 17.

[0071] FIGS. 18 and 19 are flowcharts showing examples of collision probability reduction processing in the terminal 10. The processes in FIGS. 18 and 19 are performed at appropriate timings when the processor 31 executes a program.

[0072] In step S101, the processor 31 determines whether the value of the sum Y1 in the divided base station DB1 obtained from the connection number information is greater than or equal to the value of the average value Y ave If Y1 is determined to be greater than or equal to Y ave If so, the process proceeds to step S102, and if not, the process proceeds to step S109. The process proceeding from step S101 to step S109 means that the sum does not exceed the average value and it is determined that a decrease in the reception rank (shifting to a lower rank) is unnecessary.

[0073] In step S109, the transmission power adjustment amount ΔP t is set to ΔP T_max , and the processor 31 performs transmission power control accordingly (step S109). However, instead of ΔP , the value of ΔP T_max may be used. T

[0074] In step S102, the processor 31 determines whether the probability P O associated with the first in rank order (Y1), obtained from the number of connected units information, is less than the random number rand1. The random number rand1 is greater than 0 and less than 1. If the probability P O is determined to be less than the random number rand1, the process proceeds to step S103; otherwise, the process proceeds to step S109. Using the random number rand1 , the process randomly proceeds from step S102 to step S109 according to the transition probability P o (an example of the first probability). As a result, the number of connected units is dispersed between the terminals 10 that are transferred and the terminals 10 that remain without being transferred.

[0075] In step S103, the processor 31 sets the value of d, which indicates the order of the ranks managed using, for example, the storage device 32, to 1, sets the value of U to 0, and sets the value of q, which indicates a random number, to the value specified by the random number rand2. The random number rand2 is greater than 0 and less than 1.

[0076] In step S104, the processor 31 increments the value of d. In step S105, it is determined whether the value of the sum Y d of the number of connected units is less than the value of the average value Y ave . If Y d is determined to be less than Y ave , the process proceeds to step S106; otherwise , the process returns to step S104. As a result, the value of Y d becomes the average value Yave Above The transition to the received rank above is skipped.

[0077] In step S106, the processor 31 sets the value of U to the transition probability P corresponding to the value of Y at that time. In step S107, the processor 31 determines whether the value of U is greater than the random number rand2. If it is determined that the value of U is greater than the random number rand2, the process proceeds to step S108; otherwise, the process proceeds to step S104. In step S107, the random number rand2 is used to randomly allocate the destination rank order according to the transition probability P d (An example of the second probability). I (An example of the second probability). I (An example of the second probability) is randomly allocated.

[0078] In step S108, the processor 31 calculates a value where the received rank has decreased by 1 or more as the transmission power adjustment amount ΔP, and performs transmission power control. In this way, when the sum Y of the number of connected devices exceeds its average value Y t , a transition to a lower received rank is performed with a predetermined probability. d exceeds its average value Y ave , a transition to a lower received rank is performed with a predetermined probability. is performed.

[0079] FIG. 19 is a flowchart for calculating Z sum . In step S121, the processor 31 sets the values of d and Z to 0. In step S122, the value of d is incremented. sum In step S123, the processor 31 determines whether Y is less than Y

[0080] . If it is determined that Y d is less than Y ave , the process proceeds to step S124; otherwise, the process returns to step S122. As a result, when ΔY takes a negative value, the process proceeds to step S124. d is less than Y ave , the process proceeds to step S124; otherwise, the process returns to step S122. As a result, when ΔY takes a negative value, the process proceeds to step S124. d takes a negative value, the process proceeds to step S124.

[0081] In step S124, the processor 31 sets the value of Z sum to the value of "Z sum +Y ave -Y d " to obtain the sum of the absolute values of negative ΔY d . In step S125, the processor 31 determines whether d has reached D indicating the lowest rank order. If it is determined that d = D, the process of FIG. 19 ends, and the current value of Z sum is used as the final value of Z sum in the process of step S106. If it is determined in step S125 that d ≠ D, the process returns to step S122.

[0082] FIGS. 20 and 21 are explanatory diagrams of a simulation as an example. In FIG. 20, the cell radius is 2000 m, and the base stations 11, which are distributed base stations DB1 and DB2, are located at positions 500 m apart from the center of cell 1 in opposite directions. The antenna gain of the base station 11 is 12 dBi, and the antenna gain of the terminal 10 is 2 dBi. And the maximum transmission power of the terminal 10 is 23 dBm. FIG. 21 shows the simulation parameters in tabular form. The parameters include the number of base stations 11, the number of antennas of the distributed base stations, the number of terminals 10, the transmission frequency of the terminals 10, the number of transmission slots per second, the number of reception ranks, the number of antennas of the terminals 10, the cell radius, the displacement of the arrangement of each base station from the cell center, long-term variation, short-term variation, instantaneous value variation, the antenna gain of the base station 11, the antenna gain of the terminal 10, and the maximum terminal output.

[0083] FIG. 22 is a graph showing the results of simulation. The horizontal axis of the graph represents the number of terminals, and the vertical axis represents the packet collision probability. Graph G1 shows the results for one base station 11, graph G2 shows the results for two distributed base stations without applying the process (collision probability reduction method) of FIG. 18, and graph G3 shows the results when the collision probability reduction method is applied. Graphs G2 and G3 show the probability that no collision occurs in one of the two distributed base stations. From graphs G2 and G3, it can be seen that the application of the collision probability reduction method can reduce the probability of a collision occurring in the reception rank.

[0084] In the wireless communication system according to the embodiment, the terminal 10 (each of terminals 10A, 10B, and 10C) capable of transmitting the first signal received by the distribution base station DB1 (first base station) and the second signal received by the distribution base station DB2 (second base station) by PD-UL-NOMA performs transmission power control. In the transmission power control, as shown in FIG. 6, the received power is divided into two or more reception ranks (ranks) at equal intervals, and each of the two or more reception ranks has an allowable variation width x h of the same size. Regarding adjacent upper ranks (for example, reception rank a1) and lower ranks (for example, reception rank a2) among the two or more reception ranks, a margin x h is defined between the lower limit of the allowable variation width x m in the upper rank a1 and the upper limit of the allowable variation width in the lower rank a2. The same applies between reception ranks a2 - a3 and between reception ranks a3 - a4.

[0085] And the size of the allowable variation width x h is greater than or equal to the size of the margin x m (however, in FIG. 6, x h = x m ). The terminal 10 uses the received power P1 of the first signal, the received power P2 of the second signal, the received power difference ΔP between the first signal and the second signal, the reception ranks a1 - a4 (two or more ranks), the allowable variation width x h , and the margin x m to determine whether the received power of each of the first signal and the second signal is within the allowable variation width x hThe transmission power adjustment amount ΔP of the first signal and the second signal is set to within T (FIG. 13). Then, the terminal 10 calculates the transmission power adjustment amount ΔP T is used to adjust the transmission power of the first signal and the second signal at the terminal 10.

[0086] Such an operation is performed by each of the terminals 10A, 10B, and 10C (multiple terminals 10) connected to the distributed base stations DB1 and DB2 (first and second base stations). As a result, each of the distributed base stations DB1 and DB2 can receive a signal on which the signals from the terminals 10A, 10B, and 10C are superimposed, with an appropriate reception power difference being ensured. That is, with respect to the terminals 10A, 10B, and 10C that transmit signals to the distributed base stations DB1 and DB2, respectively, an appropriate reception power difference between the terminals can be ensured in the distributed base stations DB1 and DB2.

[0087] In the embodiment, the allowable fluctuation range x h = margin x m =X, and the size between the receiving ranks is specified as 2X (Figure 6). This configuration makes it possible to provide an accurate power difference.

[0088] As shown in FIG. 8 and FIG. 13, the terminal 10 (the processor 31 serving as the control unit thereof) according to the embodiment detects whether the reception power difference ΔP between the reception power P1 of the first signal and the reception power P2 of the second signal is within the allowable fluctuation width x h If P1 or P2 is smaller than P2, the first reception power (P M ) from among the reception ranks a1 to a4. Then, the terminal 10 determines the allowable fluctuation width x h The transmission power adjustment amount ΔP T In this way, each base station can receive sufficient power. The difference can be ensured.

[0089] 9 and 13, the terminal 10 according to the embodiment calculates the reception power difference ΔP between the first signal and the second signal within an allowable fluctuation width xh Size and margin x m When the remainder ΔP’ obtained by dividing by twice the total value 2X of the size of m and the size of h is smaller than the total value X, the following is performed. That is, the terminal 10 selects P, which is the larger of P1 and P2 M identifies the nearest received rank a2 among the received ranks a1 to a4. Also, the terminal 10 subtracts the first received power P from the received power P(a2) of the nearest received rank a2 M adds or subtracts half of the remainder ΔP’, “ΔP’ / 2”, to the resulting value to obtain the transmission power adjustment amount ΔP for the first received power P M = P1 T and calculates it. Then, the terminal 10 calculates the transmission power adjustment amount for the second received power P2, which is the smaller of the first received power P1 and the second received power P2, from the first received power P M = P1 and the received power difference ΔP, and adjusts the transmission power using these transmission power adjustment amounts. In this way, a sufficient received power difference can be ensured at each base station. T As shown in FIGS. 10 and 13, when ΔP is equal to or greater than X and equal to or less than 2X, the terminal 10 according to the embodiment selects P, which is the larger of P1 and P2

[0090] M identifies the nearest received rank a2 of P among ranks 2 or higher. Also, the terminal 10 determines that the first received power P M = P1 falls within the allowable variation range of the nearest rank a2, and the second received power P2 falls within the allowable variation range x of rank a3, which is lower than the nearest rank a2 of P1 h and calculates the transmission power adjustment amount ΔP for P1 and P2. In this way, a sufficient power difference can be ensured at each base station. T As shown in FIGS. 11 and 13, when the remainder ΔP’ is larger than the total value X, the terminal 10 according to the embodiment selects the nearest rank a2 of P

[0091] = P1 from the received ranks a1 to a4. Also, the terminal 10 subtracts P from the received power P(a2) of the received rank a2 M M = P1 from the received power P(a2) of the received rank a2M To the value obtained by subtracting M , add or subtract half of the value obtained by subtracting the remainder ΔP’ from twice the total value 2X, and define this as P M = The transmission power adjustment amount ΔP for P1 T Calculate it as such. Then, the terminal 10 calculates the transmission power adjustment amount for P2 from ΔPT and ΔP, etc. In this way, a sufficient power difference can be ensured at each base station.

[0092] As shown in FIGS. 14 to 19, the terminal 10 according to the embodiment determines the sum Y M of the number A of connected terminals to the distributed base station DB1 (first base station) M and the number B of connected terminals to the distributed base station DB2 (second base station) d from the information indicating for each rank (rank order d = 1 to 5) of 2 or more, the rank a M to which the reception power of each of the first signal and the second signal belongs M+2 and the sum Y of the number of connected terminals in the rank a d of the first rank (rank order 1), which is Y1 (= A M + B M+s ). Also, the terminal 10 determines the sum Y2 to Y of the second rank, which is the sum of the number of connected terminals to the first base station and the number of connected terminals to the second base station in each lower rank (rank order 2 to D) up to a predetermined rank (rank order D) that is 1 or 2 ranks or more lower than the rank (A , B M ) to which the reception power of each of the first signal and the second signal belongs. M+2 Also, when the average value Y D of the sum Y1 of the first rank and the sums Y2 to Y of the second rank in each lower rank is such that the Y1 of the first rank is exceeded, the terminal 10 shifts the rank to which the reception power of each of the first signal and the second signal belongs to a lower rank (rank order 3 to 5 in FIG. 17) where the sum Y of the second rank is smaller than the average value Y D with a first probability P ave When the Y1 of the first rank exceeds the average value Y d shift the rank to which the reception power of each of the first signal and the second signal belongs to a lower rank (rank order 3 to 5 in FIG. 17) where the sum Y of the second rank is smaller than the average value Y ave with a first probability P o ​​It is determined by this. Then, the terminal 10 reduces the transmission power of the first signal and the second signal in accordance with the transition to a lower rank (S108 in FIG. 13).

[0093] In this way, when the sum Y1 of the number of connection terminals that transmit signals at the same rank as the ranks of the first signal and the second signal transmitted by the terminal 10 is larger than the average value Y ave more, the first probability P o and the sum Y of the number of connection terminals d shifts to a rank lower than the average value Y ave For this reason, the possibility (probability) that the first signal and the second signal collide with signals from other terminals (connection terminals) (a sufficient power difference cannot be ensured) can be reduced.

[0094] The terminal 10 according to the embodiment calculates the first probability P o by dividing the value obtained by subtracting the average value Y ave from the sum Y1 of the first ranks by the sum Y1 of the first ranks (FIG. 16). In this way, the reception power of the terminal 10 can be shifted to a lower rank with a suitable probability, the number of connection terminals can be reduced, and the collision possibility can be reduced.

[0095] The terminal 10 according to the embodiment, as shown in FIG. 16, when there are two or more lower ranks where the sum Y d of the second ranks is smaller than the average value Y ave calculates the absolute value Z of the sum (Δy3 + Δy4 + Δy5) of the values -Δy d obtained by subtracting the average value Y ave from the sums (Y3, Y4, Y5) of the sums of the second ranks in each of these two or more lower ranks (rank order d d = 3, 4, 5). Then, for each of the two or more lower ranks (d = 3, 4, 5), the terminal 10 divides Z sum by -Δy sum and uses the resulting value as the one selected as the transition destination when transitioning to a lower rank. d the second It is calculated as the probability of 2. In this way, the destination of the terminal can be appropriately dispersed.

[0096] <Other Embodiments> The above embodiments are merely examples, and the present disclosure can be appropriately modified and implemented without departing from the gist thereof.

[0097] The processes and means described in the present disclosure can be freely combined and implemented as long as no technical contradictions occur.

[0098] Also, the processes described as being performed by one device may be shared and executed by a plurality of devices. Alternatively, the processes described as being performed by different devices may be executed by one device. In a computer system, how each function is realized by a hardware configuration (server configuration) can be flexibly changed.

[0099] The present disclosure can also be realized by supplying a computer program that implements the functions described in the above embodiments to a computer, and causing one or more processors included in the computer to read and execute the program. Such a computer program may be provided to the computer by a non-transitory computer-readable storage medium connectable to the system bus of the computer, or may be provided to the computer via a network. The non-transitory computer-readable storage medium includes, for example, any type of disk such as a magnetic disk (floppy (registered trademark) disk, hard disk drive (HDD), etc.), an optical disk (CD-ROM, DVD disk, Blu-ray disk, etc.), a read-only memory (ROM), a random access memory (RAM), an EPROM, an EEPROM, a magnetic card, a flash memory, an optical card, and any type of medium suitable for storing electronic instructions.

Description of Reference Numerals

[0100] DB1, DB2... Distributed base stations 1... Cell 10... Terminal 11... Base station 31... Processor 32... Memory device 33... Communication IF 34... Input device 35... Display

Claims

1. A transmission power control method for a terminal capable of transmitting a first signal received by a first base station and a second signal received by a second base station through non-orthogonal multi-connection in the power domain, wherein the terminal the received power is divided into two or more ranks at equal intervals, each of the two or more ranks has an allowable fluctuation range of the same size, and for adjacent upper and lower ranks among the two or more ranks, a margin is defined between the lower limit of the allowable fluctuation range in the upper rank and the upper limit of the allowable fluctuation range in the lower rank. When the size of the allowable fluctuation range is equal to or greater than the size of the margin, using the received power of the first signal, the received power of the second signal, the received power difference between the first signal and the second signal, the two or more ranks, the allowable fluctuation range, and the margin, calculate the transmission power adjustment amounts of the first signal and the second signal so that the received power of each of the first signal and the second signal falls within the allowable fluctuation range of any of the two or more ranks, adjust the transmission powers of the first signal and the second signal in the terminal using the transmission power adjustment amounts A transmission power control method including this.

2. The size of the allowable fluctuation range is equal to the size of the margin, and the interval between the two or more ranks is defined by the sum of the size of the allowable fluctuation range and the size of the margin The transmission power control method according to Claim 1.

3. The terminal when the received power difference between the first signal and the second signal is smaller than the allowable fluctuation range, identify the rank closest to the first received power, which is the larger of the received power of the first signal and the received power of the second signal, from among the two or more ranks, calculate the transmission power adjustment amount so that the received power of the first signal and the received power of the second signal fall within the allowable fluctuation range of the closest rank The transmission power control method according to Claim 1 or 2.

4. The terminal when the remainder when the received power difference between the first signal and the second signal is divided by the sum of the size of the allowable fluctuation range and the size of the margin is smaller than the sum value, identify the rank closest to the first received power, which is the larger of the received power of the first signal and the received power of the second signal, from among the two or more ranks, Calculate a value obtained by adding or subtracting half of the remainder to / from the value obtained by subtracting the first received power from the received power of the nearest rank, and use this value as the transmission power adjustment amount for the first received power. Adjust so that the received power of each of the first signal and the second signal is reduced by the transmission power adjustment amount. The transmission power control method according to any one of claims 1 to 3.

5. The terminal is When the received power difference between the first signal and the second signal is equal to or greater than the allowable variation width and less than or equal to the sum of the size of the allowable variation width and the size of the margin, among the received power of the first signal and the received power of the second signal, identify the nearest rank of the first received power, which is the larger of the two values, from among the two or more ranks. Calculate the transmission power adjustment amounts for the first received power and the second received power such that the first received power falls within the allowable variation width of the nearest rank and the second received power, which is the smaller of the received power of the first signal and the received power of the second signal, falls within the allowable variation width of a rank lower than the nearest rank. The transmission power control method according to any one of claims 1 to 4.

6. The terminal is When the remainder obtained by dividing the received power difference between the first signal and the second signal by the sum of the size of the allowable variation width and the size of the margin is greater than the sum value, among the received power of the first signal and the received power of the second signal, identify the nearest rank of the first received power, which is the larger of the two values, from among the two or more ranks. Calculate a value obtained by adding or subtracting half of the value obtained by subtracting the remainder from twice the sum value to / from the value obtained by subtracting the first received power from the received power of the nearest rank, and use this value as the transmission power adjustment amount for the first received power. Adjust the transmission powers of the first signal and the second signal so that the received power of each of the first signal and the second signal is reduced by the transmission power adjustment amount. The transmission power control method according to any one of claims 1 to 5.

7. The terminal is Identify the sum of the number of connected terminals in the first rank, which is the sum of the number of connected terminals in the rank to which the received power of each of the first signal and the second signal belongs, from the information indicating the sum of the number of connected terminals to the first base station and the number of connected terminals to the second base station for each of the two or more ranks. When the ranks to which the reception powers of the first signal and the second signal respectively belong are lowered to a predetermined rank that is lower by one or two ranks or more, calculate the sum of the second ranks, which is the sum of the number of connected terminals to the first base station and the number of connected terminals to the second base station at each lower rank up to the predetermined rank. When the average value of the sum of the first ranks and the sum of the second ranks at each lower rank is exceeded by the sum of the first ranks, determine with a first probability to shift the ranks to which the reception powers of the first signal and the second signal respectively belong to a lower rank where the sum of the second ranks is smaller than the average value. Lower the transmission powers of the first signal and the second signal in response to the shift to the lower rank. The transmission power control method according to any one of claims 1 to 6.

8. The terminal is Calculate the first probability by dividing the value obtained by subtracting the average value from the sum of the first ranks by the sum of the first ranks. The transmission power control method according to claim 7.

9. The terminal is When there are two or more lower ranks where the sum of the second ranks is smaller than the average value, calculate the absolute value of the sum of the values obtained by subtracting the average value from the sum of the second ranks at each of the two or more lower ranks. For each of the two or more lower ranks, calculate the value obtained by dividing the absolute value by the value obtained by subtracting the average value from the sum of the second ranks as the probability that each of the two or more lower ranks is selected as the destination of the shift. The transmission power control method according to claim 7 or 8.

10. A terminal capable of transmitting a first signal received by a first base station and a second signal received by a second base station by power domain non-orthogonal multiple access. The received power is divided into two or more ranks at equal intervals, each of the two or more ranks has an allowable variation width of the same size, and for adjacent upper and lower ranks among the two or more ranks, a margin is defined between the lower limit of the allowable variation width in the upper rank and the upper limit of the allowable variation width in the lower rank. When the size of the allowable variation width is greater than or equal to the size of the margin, using the received power of the first signal, the received power of the second signal, the difference in received power between the first signal and the second signal, the two or more ranks, the allowable variation width, and the margin, calculate the transmission power adjustment amounts of the first signal and the second signal so that the received power of each of the first signal and the second signal falls within the allowable variation width of any of the two or more ranks. Adjust the transmission powers of the first signal and the second signal in the terminal using the transmission power adjustment amounts. A terminal including a control unit.

11. The size of the allowable variation width is equal to the size of the margin, and the interval between the two or more ranks is defined by the sum of the size of the allowable variation width and the size of the margin. The terminal according to claim 10.

12. The control unit When the difference in received power between the first signal and the second signal is smaller than the allowable variation width, identify, from among the two or more ranks, the rank closest to the first received power, which is the received power with the larger value among the received power of the first signal and the received power of the second signal. Calculate the transmission power adjustment amount so that the received power of the first signal and the received power of the second signal fall within the allowable variation width of the closest rank. The terminal according to claim 10 or 11.

13. The control unit When the remainder obtained by dividing the difference in received power between the first signal and the second signal by the sum of the size of the allowable variation width and the size of the margin is smaller than the sum value, identify, from among the two or more ranks, the rank closest to the first received power, which is the received power with the larger value among the received power of the first signal and the received power of the second signal. Calculate, as the transmission power adjustment amount for the first received power, a value obtained by adding or subtracting half of the remainder to the value obtained by subtracting the first received power from the received power of the closest rank. Adjust so that the received power of each of the first signal and the second signal decreases by the transmission power adjustment amount. The terminal according to any one of claims 10 to 12.

14. The control unit when the reception power difference between the first signal and the second signal is greater than or equal to the allowable variation range and less than or equal to the sum of the size of the allowable variation range and the size of the margin, among the reception power of the first signal and the reception power of the second signal, identify the rank closest to the first reception power, which is the larger of the two values, from among the two or more ranks, calculate the transmission power adjustment amounts for the first reception power and the second reception power such that the first reception power falls within the allowable variation range of the closest rank and the second reception power, which is the smaller of the reception power of the first signal and the reception power of the second signal, falls within the allowable variation range of a rank lower than the closest rank The terminal according to any one of claims 10 to 13.

15. The control unit when the remainder when the reception power difference between the first signal and the second signal is divided by the sum of the size of the allowable variation range and the size of the margin is greater than the sum value, among the reception power of the first signal and the reception power of the second signal, identify the rank closest to the first reception power, which is the larger of the two values, from among the two or more ranks, calculate, as the transmission power adjustment amount for the first reception power, a value obtained by adding or subtracting one-half of the value obtained by subtracting the remainder from twice the sum value to the value obtained by subtracting the first reception power from the reception power of the closest rank, adjust so that the reception power of each of the first signal and the second signal is decreased by the transmission power adjustment amount The terminal according to any one of claims 10 to 14.

16. The control unit identify, from the information indicating the sum of the number of connected terminals to the first base station and the number of connected terminals to the second base station for each of the two or more ranks, the sum of the first ranks, which is the sum of the number of connected terminals in the rank to which the reception power of each of the first signal and the second signal belongs, calculate the sum of the second ranks, which is the sum of the number of connected terminals to the first base station and the number of connected terminals to the second base station in each lower rank up to a predetermined rank when the rank to which the reception power of each of the first signal and the second signal belongs is lowered by one or two or more ranks to the predetermined rank When the sum of the first ranks and the average value of the sums of the second ranks in each of the lower ranks are exceeded by the sum of the first ranks, the ranks to which the reception powers of the first signal and the second signal respectively belong are shifted to the lower ranks where the sum of the second ranks is smaller than the average value, which is determined with a first probability. Reduce the transmission powers of the first signal and the second signal in response to the shift to the lower ranks. The terminal according to any one of claims 10 to 15.

17. The control unit calculates the first probability by dividing the value obtained by subtracting the average value from the sum of the first ranks by the sum of the first ranks. The terminal according to claim 16.

18. The control unit when there are two or more of the lower ranks where the sum of the second ranks is smaller than the average value, calculates the absolute value of the sum of the values obtained by subtracting the average value from the sum of the second ranks in each of the two or more lower ranks. For each of the two or more lower ranks, calculates the value obtained by dividing the absolute value by the value obtained by subtracting the average value from the sum of the second ranks as the probability that each of the two or more lower ranks is selected as the destination of the shift. The terminal according to claim 16 or 17.

19. A first base station, a second base station, a terminal capable of transmitting a first signal received by the first base station and a second signal received by the second base station by power domain non-orthogonal multiple access, wherein the terminal has reception powers divided into two or more ranks at equal intervals, each of the two or more ranks having an allowable variation width of the same size, and for adjacent upper and lower ranks among the two or more ranks, a margin is defined between the lower limit of the allowable variation width in the upper rank and the upper limit of the allowable variation width in the lower rank, and when the size of the allowable variation width is greater than or equal to the size of the margin, using the reception power of the first signal, the reception power of the second signal, the reception power difference between the first signal and the second signal, the two or more ranks, the allowable variation width, and the margin, calculate the transmission power adjustment amounts of the first signal and the second signal so that the reception powers of the first signal and the second signal respectively fall within the allowable variation widths of any of the two or more ranks. Adjust the transmission powers of the first signal and the second signal in the terminal using the transmission power adjustment amounts. including a control unit a wireless communication system.

20. The control unit: From the information indicating the sum of the number of connected terminals to the first base station and the number of connected terminals to the second base station for each of the two or more ranks, identifies the sum of the first rank, which is the sum of the number of connected terminals in the rank to which the reception power of each of the first signal and the second signal belongs; Calculates the sum of the second rank, which is the sum of the number of connected terminals to the first base station and the number of connected terminals to the second base station in each lower rank up to a predetermined rank when the rank to which the reception power of each of the first signal and the second signal belongs is lowered by one or two or more ranks; When the average value of the sum of the first rank and the sum of the second rank in each lower rank is exceeded by the sum of the first rank, determines with a first probability to shift the rank to which the reception power of each of the first signal and the second signal belongs to a lower rank where the sum of the second rank is smaller than the average value; Reduces the transmission power of the first signal and the second signal in response to the shift to the lower rank The wireless communication system according to claim 19.

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