Wireless communication control method, receiving station, program, and wireless terminal

Abstract

In this wireless communication control method, in order to increase the efficiency of uplink communication, a base station, to which a plurality of wireless terminals are connected, transmits, to a wireless terminal belonging to a second group different from a first group among the plurality of wireless terminals, first information for performing uplink communication through repetition transmission using an orthogonal cover code, and the base station transmits, to a wireless terminal belonging to the first group among the plurality of wireless terminals, second information for performing uplink communication using non-orthogonal multiple access.

Description

Wireless communication control method, receiving station, program, and wireless terminal

[0001] The present disclosure relates to a wireless communication control method, a receiving station, a program, and a wireless terminal.

[0002] 3GPP (registered trademark) has standards for base stations that support Non-Terrestrial Networks (NTN) (e.g., Non-Patent Document 1). 3GPP also has standards related to Non-Orthogonal Multiple Access (NOMA), a technology that enables information to be sent to multiple users in the same frequency band by transmitting signals with varying transmission power (e.g., Non-Patent Document 2).

[0003] 3GPP (registered trademark) TR 38.811 V15.4.0 (2020-09) 3GPP (registered trademark) TS 38.211 V18.1.0 (2023-12), 6.3.1

[0004] The present disclosure aims to provide a wireless communication control method, a receiving station, a program, and a wireless terminal that can improve the efficiency of uplink communication in a situation where multiple wireless terminals are connected to a base station.

[0005] One aspect of the present disclosure is a wireless communication control method including: a base station to which a plurality of wireless terminals are connected transmits first information to wireless terminals among the plurality of wireless terminals that belong to a second group different from a first group, the first information being for performing uplink communication by continuous transmission using an orthogonal cover code; and transmitting second information to wireless terminals among the plurality of wireless terminals that belong to the first group, the second information being for performing uplink communication using non-orthogonal multiple access.

[0006] Also, one aspect of the present disclosure is a receiving station that receives uplink communication signals from a plurality of wireless terminals, the receiving station including a circuit that executes the following processes: a process of transmitting first information for performing uplink communication by continuous transmission using an orthogonal cover code to wireless terminals among the plurality of wireless terminals that belong to a second group different from the first group; and a process of transmitting second information for performing uplink communication using non-orthogonal multiple access to wireless terminals among the plurality of wireless terminals that belong to the first group.

[0007] One aspect of the present disclosure is a program that causes a computer possessed by a receiving station that receives uplink communication signals from a plurality of wireless terminals to transmit first information for performing uplink communication by continuous transmission using an orthogonal cover code to wireless terminals among the plurality of wireless terminals that belong to a second group whose communication environment is inferior to the communication environment of the wireless terminals belonging to a first group, and causes the base station to transmit second information for performing uplink communication using non-orthogonal multiple access to wireless terminals among the plurality of wireless terminals that belong to the first group.

[0008] One aspect of the present disclosure is a wireless terminal connected to a base station, the wireless terminal including: a circuit for causing the wireless terminal to perform uplink communication by continuous transmission using an orthogonal cover code based on first information received from the base station; and a circuit for causing the wireless terminal to perform uplink communication using non-orthogonal multiple access based on second information received from the base station. The present disclosure may also include a communication system including the above-mentioned base station and a plurality of wireless terminals, the wireless terminals constituting the communication system, and a storage medium capable of temporarily storing a program.

[0009] According to the present disclosure, it is possible to improve the efficiency of uplink communication in a situation where multiple wireless terminals are connected to a base station.

[0010] FIG. 1A is a diagram showing a first configuration example of a communication system according to an embodiment, and FIG. 1B is a diagram showing an example of a received signal at a base station (satellite station). FIG. 2 is an explanatory diagram of a signal demodulation method using successive interference cancellation (SIC). FIG. 3A is a diagram showing a residual signal after demodulation using SIC, and FIG. 3B is an explanatory diagram of a demodulation method for a continuously transmitted signal using an orthogonal cover code (OCC). FIG. 4 is a diagram showing an example of a case where transmission power control (TPC) is performed in continuously transmitted signals using OCC. FIG. 5A is a diagram showing an example of a received signal at a base station (satellite station) in the case shown in FIG. 4, and FIG. 5B is an explanatory diagram of amplification of the residual signal. FIG. 6A is a diagram showing a second configuration example of a communication system, and FIG. 6B is a diagram showing an example of a received signal at a base station (satellite station) in the second configuration example. FIG. 7 is a diagram showing a third configuration example of a communication system. FIG. 8 is a diagram showing an example of a configuration of a wireless device. Fig. 9 is a sequence diagram showing an example of message exchange between a terminal station and a base station. Fig. 10 is a diagram showing an example of the configuration of a base station. Fig. 11 is an explanatory diagram of OCC and transmission power control. Fig. 12 is a diagram showing an example of the configuration of a terminal station. Fig. 13 is a flowchart showing an example of processing by a terminal station. Fig. 14 is a flowchart showing an example of processing by a base station.

[0011] The sixth-generation mobile communication system (6G) is being considered to ensure communication means anywhere on Earth. NTNs, such as satellite communications, are promising wireless communication networks that will realize the above-mentioned communication means. NTNs are also expected to not only address dead zones in terrestrial networks (TNs), but also improve reliability when combined with TNs and be used for IoT (Internet of Things) communications.

[0012] However, there are limitations on the frequencies available for NTN, and technology is needed to accommodate the expected surge in traffic. Furthermore, there is a problem of whether the desired communication quality can be ensured for non-line-of-site (NLOS) terminal stations, where the distance between the satellite station and the terminal station is so great that high-gain antennas cannot be used.

[0013] A communication system according to an embodiment includes a base station and a plurality of wireless terminals (terminal stations) connected to the base station. The base station may be connected to the plurality of wireless terminals via a relay station such as a satellite station, or may be connected directly to the plurality of wireless terminals. The plurality of wireless terminals may belong to either a first group (first wireless terminal group) or a second group (second wireless terminal group) different from the first group. For example, the communication environment (or communication conditions) of the wireless terminals belonging to the second group may be inferior to the communication environment (or communication conditions) of the wireless terminals belonging to the first group.

[0014] The base station transmits, to the wireless terminals belonging to the second group, information (first information) for performing uplink communication by continuous transmission using an orthogonal cover code. The base station also transmits, to the wireless terminals belonging to the first group, information (second information) for performing uplink communication using non-orthogonal multiple access. The efficiency of uplink communication can be improved by having the multiple wireless terminals perform uplink communication according to the first information or the second information.

[0015] Hereinafter, a communication system and a wireless communication control method in a communication system according to an embodiment 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. Note that, although a 5G (fifth generation mobile communication system) communication system is exemplified in the embodiments, the mobile communication method according to the present disclosure can be applied to wireless communication systems other than 5G, such as 4G (LTE) and 6G.

[0016] Fig. 1A is a diagram showing a first configuration example of a communication system. In Fig. 1A, the communication system according to the first configuration example includes a base station 1 which is a ground station, a satellite station 2 which is an example of a relay station, and a plurality of terminal stations (terminals) 10 connected to the base station 1 via the satellite station 2. Each of the plurality of terminals 10 is a wireless terminal. The satellite station 2 is an example of a "receiving station" that receives uplink communication signals. The terminals 10 are called UE (User Equipment), and the base station 1 is called gNodeB (gNB), etc.

[0017] In the example shown in FIG. 1 , terminal 10A, terminal 10B, terminal 10a, and terminal 10b are illustrated as multiple terminals 10. Terminal 10A is a terminal equipped with a high-gain antenna. Terminal 10B is mounted on an aircraft and has good line of sight (LOS). In contrast, terminals 10a and 10b are mobile terminals such as smartphones and do not have high-gain antennas (their antenna gains are lower than that of terminal 10A). Furthermore, terminals 10a and 10b are used in urban areas and have higher propagation loss than terminal 10A or terminal 10B due to the influence of obstacles such as buildings.

[0018] In the communication system according to the embodiment, terminals such as terminal 10A and terminal 10B that have a good communication environment (or communication conditions) with base station 1 (satellite station 2) are treated as terminals belonging to a first group. On the other hand, terminals such as terminals 10a and 10b that have a worse communication environment than terminals belonging to the first group are treated as terminals belonging to a second group.

[0019] The quality or inferiority of the communication environment (i.e., whether a wireless terminal belongs to the first wireless terminal group or the second wireless terminal group) can be determined based on whether the line of sight is good (LOS) or non-line of sight (NLOS), the level (magnitude) of the antenna gain, the distance from the base station 1 (satellite station 2), the magnitude of the received power at the satellite station 2, etc. However, whether each terminal belongs to the first group or the second group may be determined using criteria other than these criteria.

[0020] The base station 1 transmits first information for performing uplink communication by continuous transmission using an orthogonal cover code (OCC) (referred to as OCC continuous transmission) to the terminals 10a and 10b belonging to the second group via the satellite station 2. The base station 1 also transmits second information for performing uplink communication using non-orthogonal multiple access (NOMA) to the terminals 10A and 10B belonging to the first group.

[0021] 1B is a diagram showing an example of a received signal at satellite station 2. FIG. 1B shows the received power of signals for uplink communication transmitted from terminal 10A, terminal 10B, terminal 10a, and terminal 10b in two consecutive radio resources (resource blocks: RBs, one RB is one slot on the time axis). The two RBs are denoted as RB#1 and RB#2. Note that the multiple RBs used for continuous transmission may be continuous or discrete on the time axis.

[0022] In accordance with the second information, terminal 10A transmits a signal for uplink communication on RB #1 of RB #1 and RB #2. In accordance with the second information, terminal 10B transmits a signal for uplink communication on RB #2. The signal for uplink communication is obtained by modulating and coding data to be uplink communicated in accordance with a specified modulation and coding scheme (MCS).

[0023] The terminal 10a repeatedly transmits uplink communication signals on RBs #1 and #2 through continuous transmission. Signals repeatedly transmitted multiple times through continuous transmission are collectively referred to as "continuous transmission signals." The number of transmissions in continuous transmission is called the continuous transmission count, and each transmission (each transmission timing) in continuous transmission can be managed, for example, by a number called a continuous transmission index number.

[0024] The uplink communication signal repeatedly transmitted in continuous transmission is a signal obtained by multiplying a signal obtained by modulating and encoding the data to be communicated via uplink communication in accordance with a designated MCS by an OCC code corresponding to the OCC pattern. The uplink communication signal transmitted in RB #1 is multiplied by the OCC code "1" in accordance with the OCC pattern "+1, +1". The uplink communication signal transmitted in RB #2 is multiplied by the OCC code "1" in accordance with the OCC pattern "+1, +1" assigned to the terminal 10a. In the figures following Figure 1B, signals multiplied by the code "1" are indicated by "+", and signals multiplied by the code "-1" are indicated by "-".

[0025] Terminal 10b repeatedly transmits uplink communication signals on RBs #1 and #2 through continuous transmission. The uplink communication signals transmitted on RB #1 are multiplied by the OCC code "1" in accordance with the OCC pattern "+1, -1" assigned to terminal 10b. The uplink communication signals transmitted on RB #2 are multiplied by the code "-1" in accordance with the pattern "+1, -1".

[0026] As shown in the above example, the OCC patterns are assigned differently among the terminals 10 (10a, 10b) belonging to the second group. The uplink communication signals transmitted from the terminals 10a and 10b in RBs #1 and #2 are an example of "first signals in which orthogonal cover codes corresponding to the orthogonal cover code patterns are applied to uplink communication signals." The uplink communication signals transmitted from the terminals 10A and 10B in RBs #1 and #2 are an example of "first signals." The first information can include information indicating the number of continuous transmissions described above and information indicating the OCC to be applied to signals transmitted in each transmission (RB) in the continuous transmission (information indicating the OCC pattern).

[0027] Satellite station 2 receives signal S1 on RB #1, in which signals transmitted from terminal 10A, terminal 10a, and terminal 10b are superimposed. Also, satellite station 2 receives signal S2 on RB #2, in which signals transmitted from terminal 10B, terminal 10a, and terminal 10b are superimposed. Here, for demodulation using SIC, a sufficient power difference is provided between the received power of the signal transmitted from terminal 10A and the received power of the signals transmitted from terminals 10a and 10b.

[0028] The satellite station 2 operates as a repeater (relay station) that transmits signals received from the base station 1 to each terminal and transfers signals received from each terminal to the base station 1. However, the satellite station 2 may also have a mechanism for demodulating signals for uplink communication received from each terminal.

[0029] Fig. 2 is an explanatory diagram of a signal demodulation method using SIC at a receiving station. In NOMA, a signal is received at a receiving station in which multiple signals (Signals 1 and 2 are shown in Fig. 2) using the same frequency band and with different reception field strengths (received power) are superimposed. The receiving station demodulates the signal with the highest reception power (Signal 1 in Fig. 2). Next, the receiving station generates a replica signal of Signal 1 and removes Signal 1 from the superimposed signal. This results in Signal 2.

[0030] 3A is a diagram showing a residual signal after demodulation by SIC. In the process of performing the demodulation process using SIC on signals S1 and S2 shown in FIG. 1B, the signal of terminal 10A is demodulated using signal S1, and the signal of terminal 10B is demodulated using signal S2. Furthermore, by SIC, the signal of terminal 10A is removed from signal S1 to obtain residual signal S1, and the signal of terminal 10B is removed from signal S2 to obtain residual signal S2.

[0031] 3B is an explanatory diagram of a method for demodulating a continuous transmission signal using OCC. As shown in FIG. 3B, when residual signal S2 is added to residual signal S1, the signal components from terminal 10b in residual signals S1 and S2 cancel each other out, leaving only the signal component from terminal 10a. Combining the remaining signal components results in a result equivalent to receiving a signal from terminal 10a with twice the received power of each RB. On the other hand, when residual signal S2 is subtracted from residual signal S1, the signal components from terminal 10a in residual signals S1 and S2 cancel each other out, leaving only the signal component from terminal 10b. Combining the remaining signal components results in a result equivalent to receiving a signal from terminal 10b with twice the received power of each RB. By using OCC in this way, multiple terminals 10 can share RBs, making it possible to achieve continuous transmission without increasing RB consumption. This improves the efficiency of uplink communication for the terminals 10a and 10b belonging to the second group, and improves the reception quality from the terminals 10a and 10b.

[0032] Fig. 4 is a diagram showing an example of a case where transmission power control is performed in OCC continuous transmission. Fig. 5A is a diagram showing an example of a received signal at a receiving station in the case shown in Fig. 4, and Fig. 5B is an explanatory diagram of the amplification of a residual signal.

[0033] In SIC, it is preferable to provide a sufficient difference between the received power of the replica signal and the received power of the residual signal obtained by removing the replica signal from the superimposed signal. However, there may be cases where the terminals 10 (10A, 10B) belonging to the first group cannot transmit signals with sufficient transmission power (the received power is insufficient).

[0034] 4 illustrates a case in the communication system shown in FIG. 1 where the satellite station 2 cannot receive a signal from the terminal 10A with a reception power sufficient to perform suitable SIC. In this case, the base station 1 can transmit to the terminals 10a and 10b first information that further includes information for reducing the transmission power of the RB in which the terminal 10A transmits a signal compared to the normal transmission power (an example of information indicating the transmission power of the signal transmitted in each transmission in a continuous transmission). The transmission (RB) in which the transmission power is reduced can be identified, for example, by a continuous transmission index number.

[0035] In this case, as shown in Figure 5A, the received power of the signals of terminals 10a and 10b in signal S1 is smaller than the received power of the signals of terminals 10a and 10b in signal S2, but a sufficient power difference can be established between the signal of terminal 10A.

[0036] When demodulating the signals from terminals 10a and 10b, base station 1 obtains residual signals S1 and S2 by removing the signals from terminals 10A and 10B from superimposed signals S1 and S2 (see FIG. 5A), as shown in FIG. 5B, and amplifies residual signal S1 so that the power level of residual signal S1 is equivalent to the power level of residual signal S2. This makes it possible to obtain residual signals S1 and S2 that are equivalent to signals transmitted at the same transmission power in each RB. For such residual signals, the OCC demodulation method described with reference to FIG. 3B can be used to obtain the signals from terminal 10a and terminal 10b.

[0037] 6A is a diagram showing a second configuration example of a communication system, and FIG. 6B is a diagram showing an example of a received signal at a base station 1 (satellite station 2) in the second configuration example. Continuous transmission using OCC requires resources that are a power of 2, but the number of terminals 10 that are superimposed on one resource and the number of terminals 10 that are superimposed in NOMA can be set arbitrarily.

[0038] In the second configuration example shown in Fig. 6A, terminal 10A belongs to a first group, and terminals 10a to 10d belong to a second group. As shown in Fig. 6B, the number of times that terminals 10a to 10d transmit a continuous signal is four, and the continuous signal is repeatedly transmitted in four consecutive RBs (RBs #1 to #4).

[0039] Different OCC patterns are assigned to the terminals 10a to 10d. For example, the terminal 10a is assigned a pattern of "+1, +1, -1, -1", the terminal 10b is assigned a pattern of "-1, +1, -1, +1", the terminal 10c is assigned a pattern of "-1, +1, +1, -1", and the terminal 10d is assigned a pattern of "+1, +1, +1, +1". The corresponding OCC codes are applied (multiplied) to the signals transmitted in RBs #1 to #4. Even when the number of consecutive transmissions (OCC patterns) is four or more, the desired signal components can be retained by adding or subtracting signals in each RB.

[0040] The OCC patterns are stored in advance in the terminal 10 in table format, and an index number is assigned to each OCC length and code pattern. By transmitting first information including the index number to the terminal 10, the terminal 10 can perform continuous transmission according to the OCC pattern corresponding to the index number. In this case, a configuration can be employed in which the pattern and the number of continuous transmissions are associated and stored in a table, and the number of continuous transmissions and the pattern are identified from the index number included in the first information. However, a configuration can also be employed in which the first information is transmitted that includes information indicating the number of continuous transmissions and information indicating the pattern itself.

[0041] 6A and 6B, a signal is transmitted from terminal 10A on RB #2, and terminals 10a to 10b reduce the transmission power of the signal transmitted on RB #2 below the transmission power used on other RBs #1, #3, and #4 in accordance with the first information. However, it is possible to appropriately set the time (RB) on which the signal from terminal 10A is superimposed and whether or not to reduce the transmission power on that RB.

[0042] FIG. 7 illustrates a third exemplary configuration of a communication system. In this third exemplary configuration, there is no relay station (satellite station), and multiple terminals 10 are directly connected to the base station 1. Among the multiple terminals 10, terminals 10A and 10B are located closer to the base station 1, while terminals 10a and 10b are located farther from the base station 1. Since the longer the distance between the terminal 10 and the base station 1, the lower the received power tends to be, the terminals 10A and 10B are treated as terminals belonging to a first group, and terminals 10a and 10b are treated as terminals belonging to a second group. The method for controlling uplink communication (wireless communication control method) for each of the multiple terminals 10 is the same as the wireless communication control method described in the first exemplary configuration, and therefore a description thereof will be omitted. In this manner, the signal from the receiving station of the uplink communication may be a relay station such as the satellite station 2 or the base station 1.

[0043] FIG. 8 illustrates a hardware configuration of a wireless device applicable to the base station 1 and the terminal 10. The wireless device 100 includes a CPU 11, a main memory device 12, and external devices, all interconnected via a bus 17, and executes communication and information processing using a computer program. The CPU 11 is also referred to as a processor. The CPU 11 is not limited to a single processor and may have a multi-processor configuration. The CPU 11 may also include a graphics processing unit (GPU), a digital signal processor (DSP), or the like. The CPU 11 may also cooperate with a hardware circuit such as a field programmable gate array (FPGA). Examples of external devices include an external memory device 13, an output device 14, an operation device (input device) 15, and a communication device 16, as shown in FIG. 8.

[0044] The CPU 11 executes a computer program executable in the main memory device 12, causing the wireless device 100 to operate as a base station 1 or a terminal 10. The main memory device 12 stores the computer program executed by the CPU 11, data processed by the CPU 11, etc. The main memory device 12 is, for example, a dynamic random access memory (DRAM), a static random access memory (SRAM), a read-only memory (ROM), etc. The external memory device 13 is used as a storage area supporting the main memory device 12 and stores the computer program executed by the CPU 11, data processed by the CPU 11, etc. The external memory device 13 is, for example, a hard disk drive, a solid state drive (SSD), etc. Furthermore, a drive device for a removable storage medium may be connected to the wireless device 100. The removable storage medium may be, for example, a Blu-ray disc, a digital versatile disc (DVD), a compact disc (CD), a flash memory card, etc.

[0045] The output device 14 is, for example, a display device such as a liquid crystal display or an electroluminescence panel. However, the output device 14 may also include a speaker or other device that outputs sound. The operation device 15 is, for example, a key, button, dial, or touch panel with a touch sensor overlaid on a display. The communication device 16 communicates with the base station 1 and an external network such as the Internet via, for example, optical fiber. The communication device 16 includes a wireless communication device (including a transmitting / receiving antenna) used for wireless communication between the base station 1 or satellite station 2 and the terminal 10, and a communication device for the base station 1 to communicate with the core network. The communication device 16 may also include communication equipment for connecting to a wireless LAN (Wi-Fi). The communication device 16 may be a single device or a combination of multiple devices.

[0046] The processes executed by the CPU 11 and memory (e.g., main storage device 12) may be executed by semiconductor devices such as FPGA, CPLD (Complex Programmable Logic Device), ASIC (Application Specific Integrated Circuit), SoC (System on a chip), etc. The CPU 11 (processor), FPGA, CPLD, ASIC, and SoC are examples of "circuitry" included in a wireless device operable as the base station 1 or the terminal 10.

[0047] Fig. 9 is a sequence diagram showing an example of message exchange between a terminal station (terminal 10) and base station 1. In Fig. 9, the relay station (satellite station 2) described in the first and second configuration examples is omitted because it does not change the content of information transmitted and received between the terminal 10 and base station 1.

[0048] 9, the terminal 10 transmits a scheduling request message (SR) to the base station 1 at a predetermined timing (FIG. 9(1)). The base station 1, having received the SR, transmits a grant permission message to the terminal 10 as a response message to the SR (FIG. 9(2)).

[0049] The terminal 10 that has received the grant transmits a message including information required for the scheduler to the base station 1 (FIG. 9 (3)). The information required for the scheduler includes, for example, the channel state (channel state information), information indicating the remaining transmission power, information indicating the buffer amount, and information indicating the priority. The base station 1 can determine whether the terminal 10 belongs to the first group or the second group based on, for example, the information indicating the remaining transmission power.

[0050] Upon receiving the information indicating the priority, the base station 1 transmits to the terminal 10 information indicating the allocation of radio resources (RBs) to be used for uplink communication (corresponding to the first information) (FIG. 9 (4)). At this time, if the terminal 10 belongs to the second group, the base station 1 transmits an OCC instruction, or an OCC instruction and a transmission power instruction. The OCC instruction is an instruction for continuous transmission using OCC and is information included in the first information. The OCC instruction may include information indicating the number of continuous transmissions and information indicating the OCC pattern. The transmission power instruction is also information included in the first information and is information indicating the transmission power of each continuous transmission. For example, it is a continuous transmission index number corresponding to a transmission using a transmission power lower than the normal transmission power. However, the transmission power instruction can be omitted if transmission power control is not performed. The information indicating the allocation of radio resources (radio resource allocation), the OCC instruction, and the transmission power instruction may be transmitted together in one message or transmitted separately in two or more messages.

[0051] Here, information indicating wireless resource allocation is transmitted to terminals 10 belonging to the first group, but an OCC instruction and a transmission power instruction are not transmitted. In this case, the information indicating wireless resource allocation corresponds to the “second information.”

[0052] The terminal 10 that has received the information indicating the radio resource allocation and the OCC instruction performs uplink communication (data transmission) by OCC continuous transmission using the radio resources (RBs) indicated in the radio resource allocation (FIG. 9 (5)). At this time, if a transmission power instruction has also been received, the terminal 10 performs transmission power control in accordance with the transmission power instruction. On the other hand, the terminal 10 that has received the information indicating the radio resource allocation performs uplink communication (data transmission) using the radio resources (RBs) indicated in the radio resource allocation.

[0053] Fig. 10 is a diagram showing an example of the configuration of a base station 1. The wireless device 100 shown in Fig. 8 can operate as a base station 1 having the configuration shown in Fig. 10 by the CPU 11 executing a program. In Fig. 10, the base station 1 operates as a device including a radio protocol control unit 201, a scheduler 202, a physical downlink control channel (PDCCH) control unit 203, a radio unit 204, an antenna 205, a NOMA demodulation unit 206, and an OCC demodulation unit 207. The numbers in parentheses shown in Fig. 10 correspond to the numbers in parentheses in the sequence diagram shown in Fig. 9.

[0054] The antenna 205 is an antenna for transmitting and receiving radio waves. The radio unit 204 demodulates the radio signal received by the antenna 205. The SR transmitted from the terminal 10 is provided to the radio protocol control unit 201 via the antenna 205 and the radio unit 204 (FIG. 10(1)).

[0055] The radio protocol control unit 201 has a scheduler 202, and upon receiving the SR, the scheduler 202 determines whether or not to permit uplink communication according to the SR. If uplink communication is permitted, the radio protocol control unit 201 issues a grant permission. The grant permission is mapped to a PDCCH by the PDCCH control unit 203, converted into a radio signal (radio wave) by the radio unit 204, and radiated (transmitted) from the antenna 205 (FIG. 10 (2)).

[0056] The information required for the scheduler, which is transmitted by the terminal 10 that has received the grant, is supplied to the scheduler 202 via the antenna 205 and the radio unit 204 (FIG. 10 (3)). The scheduler 202 refers to the information required for the scheduler (e.g., information indicating transmission power and information indicating remaining transmission power) and determines whether the terminal 10 belongs to the first group or the second group.

[0057] When it is determined that the terminal 10 belongs to the first group, the scheduler 202 issues information indicating the allocation of radio resources for uplink communication so as to perform uplink communication by NOMA, but does not issue an OCC instruction or a transmission power instruction. The information indicating the radio resource allocation is mapped to the PDCCH by the PDCCH control unit 203 and transmitted from the antenna 205 via the radio unit 204 (FIG. 10 (4)).

[0058] When the terminal 10 is determined to belong to the second group, the scheduler 202 issues information indicating radio resource allocation for uplink communication and an OCC instruction to cause the terminal 10 to perform uplink communication by OCC continuous transmission. At this time, when the terminal 10 is to perform transmission power control, the scheduler 202 further issues a transmission power instruction.

[0059] FIG. 11 is an explanatory diagram of OCC and transmission power control. FIG. 11 illustrates four types of OCC and transmission power instruction patterns when the number of consecutive transmissions is 4. Patterns 1 to 4 have different OCC code patterns. Also, patterns 1 to 4 illustrate an example in which the transmission power in the second transmission (continuous transmission index number = 2) in consecutive transmission is reduced by -3 dB from the normal transmission power (difference = -3 dB). In the first, third, and fourth transmissions (continuous transmission index numbers = 1, 3, 4), the difference from the normal transmission power is 0 dB. For example, a consecutive transmission index number corresponding to the number of RBs (RBs) in which the transmission power is reduced can be applied as the transmission power instruction.

[0060] The information indicating the radio resource allocation, the OCC instruction, and the transmission power instruction (if issued) output from the radio protocol control unit 201 are mapped to the PDCCH by the PDCCH control unit 203 and transmitted from the antenna 205 via the radio unit 204 (Figure 10 (4)).

[0061] When an uplink communication signal from a terminal 10 belonging to the first group is acquired by the antenna 205 and the radio unit 204 (FIG. 10(5)), the NOMA demodulation unit 206 performs demodulation processing using SIC (FIG. 2) and decoding processing to restore data from the terminal 10. The data is passed to a higher layer, where predetermined processing is performed.

[0062] When an uplink communication signal from a terminal 10 belonging to the second group is acquired by the antenna 205 and the radio unit 204 (FIG. 10(5)), the NOMA demodulation unit 206 performs demodulation processing using SIC (FIG. 2) and decoding processing to restore the data from the terminal 10. The data is passed to a higher layer, where predetermined processing is performed.

[0063] Fig. 12 is a diagram showing an example of the configuration of a terminal station (terminal 10). The wireless device 100 shown in Fig. 8 operates as the terminal 10 having the configuration shown in Fig. 12 when the CPU 11 executes a program. In Fig. 12, the terminal 10 operates as a device including a radio protocol control unit 101, a physical uplink control channel (PUCCH) and physical uplink shared channel (PUSCH) control unit (PUCCH / PUSCH control unit) 102, a radio unit 103, an antenna 104, and a PUSCH control unit 105. The numbers in parentheses shown in Fig. 12 match the numbers in parentheses shown in Figs. 9 and 10.

[0064] The radio protocol control unit 101 issues an SR at a predetermined timing. The SR is mapped to the PUCCH by the PUCCH / PUSCH control unit 102, converted into a radio signal and radio wave by the radio unit 103, and radiated (transmitted) from the antenna 104 (FIG. 12 (1)).

[0065] A grant from the base station 1 is supplied to the radio protocol control unit 101 via the antenna 104 and the radio unit 103 (FIG. 12 (2)). The radio protocol control unit 101 issues information required for the scheduler 202, and the information required for the scheduler 202 is mapped to, for example, a PUSCH by the PUCCH / PUSCH control unit 102 and transmitted from the antenna 104 via the radio unit 103 (FIG. 12 (3)).

[0066] The first information (including a radio resource allocation and an OCC instruction, and possibly including a transmission power instruction) or the second information (information indicating the radio resource allocation) from the base station 1 is supplied to the radio protocol control unit 101 via the antenna 104 and the radio unit 103 (FIG. 12 (4)). The radio protocol control unit 101 receives data (user data) to be transmitted in uplink communication supplied from a higher layer and supplies it to the PUSCH control unit 105. The PUSCH control unit 105 modulates and encodes the user data in accordance with the MCS. At this time, if the radio protocol control unit 101 has not received an OCC instruction, the PUSCH control unit 105 maps the signal (NOMA signal) obtained by modulating and encoding the user data to the PUSCH radio resource (RB) allocated by the radio resource allocation. The mapped signal is converted into a high-frequency signal in the radio unit 103, and further converted into a radio wave, which is then radiated (transmitted) from the antenna 104 (FIG. 12 (5)). Normal transmission power is applied to the radiation of this radio wave.

[0067] On the other hand, when the radio protocol control unit 101 receives an OCC instruction together with the radio resource allocation, the PUSCH control unit 105 generates a signal by multiplying the signal (NOMA signal) obtained by modulating and encoding the user data by an OCC according to the OCC pattern. The generated signal is mapped to the PUSCH radio resource (RB) allocated by the radio resource allocation. The mapped signal is converted into a high-frequency signal in the radio unit 103, and further converted into radio waves, which are then radiated (transmitted) from the antenna 104 (FIG. 12 (5)). This process is repeated according to the number of continuous transmissions specified in the OCC instruction. Furthermore, when a transmission power instruction is received together with the radio resource allocation, a transmission power lower than the normal transmission power is applied to the transmission of the signal mapped to the radio resource (RB) corresponding to the continuous transmission index number specified in the transmission power instruction.

[0068] Fig. 13 is a flowchart showing an example of processing by a terminal station (terminal 10). Numbers in parentheses shown in Fig. 13 correspond to the numbers in parentheses shown in Fig. 9, Fig. 10, and Fig. 12. In Fig. 13, when data (user data) to be used for uplink communication is generated (step S001), the terminal 10 performs processing to transmit an SR to the base station 1 (step S002).

[0069] In step S003, if it is determined that a grant has been acquired (received) from the base station 1, the process proceeds to step S004; otherwise, the process returns to step S002.

[0070] In step S004, the terminal 10 performs a process of transmitting necessary information to the scheduler 202. In step S005, if the terminal 10 belongs to the first group, it receives a radio resource allocation from the base station 1. On the other hand, if the terminal 10 belongs to the second group, it receives a radio resource allocation, an OCC instruction, and a transmission power instruction (if issued) from the base station 1.

[0071] In step S006, the terminal 10 generates a packet including a signal obtained by demodulating and encoding the user data. The packet is transmitted using the PUSCH.

[0072] The process of step S007 is performed when an OCC instruction is received. The terminal 10 generates a packet including a signal obtained by demodulating and encoding user data and multiplying the signal by an OCC (1 or −1) according to the pattern. The packet is mapped to the number of radio resources (RBs) of the PUSCH specified by the OCC instruction and transmitted.

[0073] The process of step S008 is performed when a transmission power instruction is received. The terminal 10 performs transmission power control to set the transmission power to be applied to the radio resource having the continuous transmission index number specified in the transmission power instruction to a transmission power that is reduced by a predetermined amount from the normal transmission power.

[0074] The processes of steps S006 and S007 are executed when the terminal 10 belongs to the second group, and are not executed when the terminal 10 belongs to the first group (jump from step S006 to step S009).

[0075] In step S009, the terminal 10 performs a process of transmitting packets mapped to predetermined radio resources (RBs) in the PUSCH. At this time, if continuous transmission using OCC is performed, the packets to which OCC is applied are repeatedly transmitted using multiple radio resources corresponding to the number of continuous transmissions.

[0076] Fig. 14 is a flowchart showing an example of processing by the base station 1. The numbers in parentheses shown in Fig. 13 correspond to the numbers in parentheses shown in Figs. 9, 10, 12, and 13. In step S101, the base station 1 receives the SR transmitted from the terminal 10.

[0077] In step S102, the base station 1 determines whether or not radio resources (communication resources) for uplink communication can be allocated to the terminal 10 that sent the SR (scheduling request). If it is determined that communication resources can be allocated, the process proceeds to step S103; otherwise, the process proceeds to step S110, where the SR is rejected (communication is not permitted).

[0078] In step S103, the base station 1 performs a process of transmitting a grant to the terminal 10 that is the source of the SR. In step S104, the base station 1 performs a process of receiving information required for the scheduler 202 from the terminal 10 that is the source of the SR.

[0079] In step S105, the base station 1 determines the group (first group or second group) to which the terminal 10 that transmitted the SR belongs, using information required for the scheduler 202. If the terminal 10 belongs to the first group, the base station 1 performs a process of transmitting first information including information indicating radio resource allocation. On the other hand, if the terminal 10 belongs to the second group, the base station 1 performs a process of transmitting second information including information indicating radio resource allocation, an OCC instruction, and a transmission power instruction (if transmission power control is performed).

[0080] In step S106, the base station 1 determines whether a packet has been received. That is, the base station 1 determines whether a packet related to uplink communication has been acquired from the PUSCH radio resource (RB) allocated by the radio resource allocation within a predetermined time after the first information or the second information has been transmitted. If it is determined that a packet has been received, the process proceeds to step S107. If not, the process proceeds to step S111, where a process of transmitting a NACK (Negative Acknowledgement) is performed.

[0081] In step S107, if the terminal 10 belongs to the first group, the base station 1 performs demodulation using NOMA, i.e., demodulation processing using SIC (Figure 2), on the packets received using the radio resources (RBs) allocated in the radio resource allocation.

[0082] In step S107A, the base station 1 determines whether user data has been obtained (demodulated) by the demodulation process in step S107. If it is determined that user data has been obtained, the base station 1 transmits the user data to the upper layer. On the other hand, if it is determined that user data has not been obtained, the process proceeds to step S108.

[0083] In step S108, demodulation processing using OCC (FIG. 3B) is performed using the residual signal (see FIG. 3A) from which the signals from the terminals 10 belonging to the first group have been removed by the processing in step S107.

[0084] In step S108, the base station 1 determines whether or not user data has been obtained by the demodulation process in step S108 (whether or not demodulation has been successful). If it is determined that user data has been obtained, the base station 1 transmits the user data to the upper layer. On the other hand, if it is determined that user data has not been obtained, a NACK is transmitted (step S112).

[0085] In the communication system according to the embodiment, a base station 1 connected to a plurality of terminals 10 (wireless terminals) transmits first information (radio resource allocation, OCC instruction, and transmit power instruction) for performing uplink communication by continuous transmission using an orthogonal cover code (OCC) to terminals 10 (e.g., terminals 10a and 10b in FIG. 1 ) belonging to a second group different from the first group among the plurality of terminals 10. The base station 1 also transmits second information (radio resource allocation) for performing uplink communication using non-orthogonal multiple access to terminals 10 (terminals 10A and 10B in FIG. 1 ) belonging to the first group among the plurality of terminals 10. This effectively increases the received power of signals from terminals 10 belonging to the second group, thereby suppressing delays and retransmissions of signals from terminals 10 belonging to the second group. This enables efficient uplink communication when a plurality of terminals 10 are connected to the base station 1.

[0086] In an embodiment, the first information may include an OCC instruction, and the OCC instruction may include information indicating the number of consecutive transmissions and information indicating an orthogonal cover code to be applied to a signal transmitted in each of the consecutive transmissions. The first information may further include information indicating the transmission power of the signal transmitted in each of the consecutive transmissions (transmission power instruction: information indicating the amount of reduction in transmission power in a given transmission).

[0087] In the embodiment, the first information may include information for causing the terminals 10 belonging to the second group to transmit first signals (e.g., signals transmitted from the terminals 10 a and 10 b in FIG. 1A ) in which an orthogonal cover code corresponding to a pattern of the orthogonal cover code is applied to an uplink communication signal transmitted in each of a plurality of radio resources corresponding to the number of consecutive transmissions. The pattern of the orthogonal cover code differs between the terminals 10 belonging to the second group (e.g., see FIG. 1A ).

[0088] In an embodiment, the second information may include information that causes a terminal 10 belonging to the first group to transmit a second signal for uplink communication (a signal transmitted from terminals 10A and 10B in FIG. 1A) that is superimposed on the first signal in any one of a plurality of radio resources.

[0089] In the embodiment, the first information may include information (transmission power instruction) to reduce the transmission power of a second signal transmitted in the radio resource in which the first signal is transmitted.

[0090] In the embodiment, an example is given of a case where the communication environment of a terminal 10 belonging to the second group is inferior to the communication environment of a terminal 10 belonging to the first group, but the criteria for classification into either the first group or the second group may be other than the above example.

[0091] The receiving station that receives uplink communication signals from the plurality of terminals 10 may be a satellite station 2 (FIGS. 1 and 6) or a base station 1 (FIG. 7).

[0092] The embodiment also includes a terminal 10 connected to the base station 1. The terminal 10 may include a circuit (such as a CPU 11) that performs a process of causing the terminal 10 to perform uplink communication by continuous transmission using OCC based on first information received from the base station 1, and a process of causing the terminal 10 to perform uplink communication using NOMA based on second information received from the base station 1.

[0093] The above-described embodiment is merely an example, and the present disclosure may be modified as appropriate within the scope of the present disclosure. Furthermore, the processes and means described in the present disclosure may be freely combined and implemented as long as no technical contradiction occurs.

[0094] 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 a single device. In a computer system, the hardware configuration (server configuration) by which each function is realized can be flexibly changed.

[0095] 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 having one or more processors in the computer read and execute the program. Such a computer program may be provided to the computer on 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 any type of medium suitable for storing electronic instructions, such as any type of disk, including magnetic disks (e.g., floppy disks, hard disk drives (HDDs), etc.), optical disks (e.g., CD-ROMs, DVDs, Blu-ray disks), read-only memory (ROM), random access memory (RAM), EPROM, EEPROM, magnetic cards, flash memory, or optical cards.

Claims

1. A wireless communication control method comprising: a base station to which a plurality of wireless terminals are connected transmits first information for performing uplink communication by continuous transmission using an orthogonal cover code to wireless terminals of the plurality of wireless terminals that belong to a second group different from a first group; and the base station transmits second information to wireless terminals of the plurality of wireless terminals that belong to the first group for performing uplink communication using non-orthogonal multiple access.

2. A wireless communication control method according to claim 1, wherein the first information includes information indicating the number of consecutive transmissions and information indicating an orthogonal cover code to be applied to the signal transmitted in each of the consecutive transmissions.

3. The wireless communication control method according to claim 2, wherein the first information further includes information indicating the transmission power of the signal transmitted in each successive transmission.

4. A wireless communication control method as described in claim 1, wherein the first information includes information for causing a wireless terminal belonging to the second group to transmit a first signal to which an orthogonal cover code corresponding to an orthogonal cover code pattern is applied to an uplink communication signal transmitted on each of a plurality of wireless resources equal to the number of consecutive transmissions, and the orthogonal cover code pattern differs between wireless terminals belonging to the second group.

5. The wireless communication control method according to claim 4, wherein the second information includes information for causing a wireless terminal belonging to the first group to transmit a second signal for uplink communication superimposed on the first signal in any one of the plurality of wireless resources.

6. The radio communication control method according to claim 5, wherein the first information includes information for reducing the transmission power of the second signal transmitted in the radio resource in which the first signal is transmitted.

7. The wireless communication control method according to claim 1, wherein the communication environment of the wireless terminals belonging to the second group is inferior to the communication environment of the wireless terminals belonging to the first group.

8. A receiving station that receives uplink communication signals from a plurality of wireless terminals, the receiving station including a circuit that executes the following processes: transmitting first information for performing uplink communication by continuous transmission using an orthogonal cover code to wireless terminals among the plurality of wireless terminals that belong to a second group different from the first group; and transmitting second information for performing uplink communication using non-orthogonal multiple access to wireless terminals among the plurality of wireless terminals that belong to the first group.

9. The receiving station according to claim 8, wherein the first information includes information indicating the number of consecutive transmissions and information indicating an orthogonal cover code to be applied to data to be communicated in uplink communication in each transmission in the consecutive transmissions.

10. The receiving station according to claim 9, wherein the first information further includes information indicating a transmission power to be applied to each transmission in the continuous transmission.

11. A receiving station as described in claim 8, wherein the first information includes information for causing a wireless terminal belonging to the second group to transmit a first signal for uplink communication in which an orthogonal cover code corresponding to a pattern of an orthogonal cover code is applied to data to be uplink communicated, in each of a plurality of consecutive wireless resources equal to the number of consecutive transmissions, and the pattern of the orthogonal cover code differs between wireless terminals belonging to the second group.

12. The receiving station according to claim 11, wherein the second information includes information for causing a wireless terminal belonging to the first group to transmit a second signal for uplink communication superimposed on the first signal in any one of the plurality of wireless resources.

13. The receiving station according to claim 12, wherein the first information includes information to reduce the transmission power of the second signal transmitted in the radio resource in which the first signal is transmitted.

14. A program that causes a computer possessed by a receiving station that receives uplink communication signals from a plurality of wireless terminals to execute the following process: transmitting first information for performing uplink communication by continuous transmission using an orthogonal cover code to wireless terminals of the plurality of wireless terminals that belong to a second group whose communication environment is inferior to that of the wireless terminals of the first group; and transmitting second information for performing uplink communication using non-orthogonal multiple access to wireless terminals of the plurality of wireless terminals that belong to the first group.

15. The program according to claim 14, wherein the first information includes information indicating the number of consecutive transmissions and information indicating an orthogonal cover code to be applied to the data to be transmitted in uplink communication in each transmission in the consecutive transmissions.

16. The program according to claim 15, wherein the first information further includes information indicating the transmission power to be applied to each transmission in the continuous transmission.

17. The program described in claim 14, wherein the first information includes information for causing a wireless terminal belonging to the second group to transmit a first signal for uplink communication in which an orthogonal cover code corresponding to an orthogonal cover code pattern is applied to data to be uplink communicated, in each of a plurality of consecutive wireless resources equal to the number of consecutive transmissions, and the orthogonal cover code pattern differs between wireless terminals belonging to the second group.

18. The program according to claim 17, wherein the second information includes information for causing a wireless terminal belonging to the first group to transmit a second signal for uplink communication superimposed on the first signal in any one of the plurality of wireless resources.

19. The program according to claim 18, wherein the first information includes information for reducing the transmission power of the second signal transmitted in the radio resource in which the first signal is transmitted.

20. A wireless terminal connected to a base station, comprising a circuit for performing a process of causing the wireless terminal to perform uplink communication by continuous transmission using an orthogonal cover code based on first information received from the base station, and a process of causing the wireless terminal to perform uplink communication using non-orthogonal multiple access based on second information received from the base station.

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