Transmission control method and information processing apparatus

Abstract

The present disclosure enables proper retransmission by a transmission station connected with a reception station through NOMA. The transmission control method of the present disclosure is a transmission control method for a plurality of transmission stations (2) of non-orthogonal multiple access with a reception station (1) as a wireless communication object, the plurality of transmission stations (2) being able to respectively retransmit to continuously transmit the same signal to the reception station at a common prescribed period and a prescribed number of times among the plurality of transmission stations (2). In this method, an information processing device (1b) calculates an initial value of transmission power respectively allocated to the plurality of transmission stations (2), the initial value of the transmission power being higher as reception quality at the reception station (1) is better and ensuring a power difference required among the transmission stations, and the information processing device (1b) calculates a retransmission number of a first transmission station to which the largest initial value of the transmission power is allocated among the plurality of transmission stations (2) based on an index value of the reception quality.

Description

Technical Field

[0001] The present disclosure relates to a transmission control method and an information processing device. Background Art

[0002] In the mobile communications standards organization 3GPP (Third Generation Partnership Project), coverage enhancement (enhancing communication range) is one of the topics in Release 17. During the meeting, discussions were held on technologies for enabling communication that meets the desired communication requirements, regardless of the distance from the base station, even when there is significant transmission loss between the base station and the terminal.

[0003] As technical background for the present disclosure, there is a technique for retransmitting the same signal, integrating the same signal at a receiving station, and improving the signal-to-noise ratio (SNR) at the receiving station (e.g., Non-Patent Document 1). Furthermore, there is a technique for enabling multiple terminals to transmit data using the same frequency band and the same time band using a non-orthogonal multiple access (NOMA) base station (e.g., Non-Patent Document 2).

[0004]

Non-patent literature

[0005] [Non-Patent Document 1] 3GPP TR 38.830, Study on NR Coverage Enhancements (Release 17), December 2020

[0006] [Non-patent document 2] M. Moriyama, T. Takizawa, M. Oodo, H. Tezuka, and F. Kojima, "Experimental Evaluation of a Novel Up-link NOMA System for IoT communication Equipping Repetition Transmission and Receive Diversity," IEICE Trans. Commun., Vol. E102-B, No. 8, pp1467-1476 Summary of the Invention

[0007] The present disclosure aims to provide a technology that enables appropriate retransmission by multiple transmitting stations that are non-orthogonal to a receiving station through multiple access.

[0008] One embodiment of the present disclosure is a transmission control method for multiple transmitting stations that utilize non-orthogonal multiple access with a receiving station as a wireless communication target, wherein the multiple transmitting stations are capable of transmitting the same signal to the receiving station a predetermined number of times continuously at a common predetermined period through retransmission. In this transmission control method, an information processing device performs the following processing: calculating initial values ​​of transmission power to be allocated to each of the multiple transmitting stations, such that the initial values ​​of transmission power increase as the reception quality at the receiving station improves while ensuring a required reception power difference between the transmitting stations; and calculating the number of retransmissions for the first transmitting station, among the multiple transmitting stations, to which the initial transmission power value is allocated, based on a reception quality indicator.

[0009] Another aspect of the present disclosure is an information processing device including a control unit. In the information processing device, the control unit performs the following processing for a plurality of transmitting stations that utilize non-orthogonal multiple access with a receiving station of a wireless communication target and can transmit the same signal to the receiving station a predetermined number of times continuously at a common predetermined period through retransmission: calculating initial values ​​of transmission power to be allocated to each of the plurality of transmitting stations, the initial values ​​of transmission power increasing as the reception quality at the receiving station improves while ensuring a required reception power difference between the transmitting stations; and calculating the number of retransmissions for a first transmitting station to which the largest initial value of transmission power is allocated among the plurality of transmitting stations based on a reception quality index value.

[0010] One of the other aspects of the present disclosure is a transmission control method for a first transmitting station, wherein the first transmitting station is included in a plurality of transmitting stations that perform non-orthogonal multiple access with a receiving station as a wireless communication target, and wherein the plurality of transmitting stations are capable of transmitting the same signal to the receiving station a predetermined number of times continuously at a common predetermined period through retransmission. This transmission control method includes: the first transmitting station receiving information including the number of retransmissions to the receiving station and the transmit power used in each retransmission, and performing retransmissions based on the information. The information further includes a first value as an initial transmit power value allocated to the first transmitting station, and a second value greater than the first value, the second value being the transmit power used after retransmission ceases for the transmitting station to which the maximum transmit power value is allocated, if the first value is not the maximum of the initial transmit power values ​​allocated to the plurality of transmitting stations.

[0011] One of the other aspects of the present disclosure is a first transmitting station included in a plurality of transmitting stations that perform non-orthogonal multiple access with a receiving station as a wireless communication target, wherein the plurality of transmitting stations are capable of transmitting the same signal to the receiving station a predetermined number of times continuously at a common predetermined period through retransmission. The first transmitting station includes: a communication unit that receives information including the number of retransmissions to the receiving station and the transmit power used in each retransmission; and a control unit that uses the communication unit to control retransmission based on the information. The information includes a first value as an initial value of the transmit power allocated to the first transmitting station, and a second value greater than the first value, the second value being the transmit power used for retransmissions after retransmissions by the transmitting station assigned the maximum value have ceased, if the first value is not the maximum value of the initial values ​​of the transmit power allocated to the plurality of transmitting stations.

[0012] Other aspects of the present disclosure may include: a wireless communication system including the above-mentioned multiple sending sites and receiving sites; a program that enables a computer to act as the above-mentioned sending site, receiving site or information processing device; a non-temporary storage medium recording the program, etc.

[0013] According to the present disclosure, it is possible to enable appropriate retransmission by multiple transmitting stations that perform non-orthogonal multiple access with respect to a receiving station. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 (A) is a diagram showing a first configuration example of a wireless communication system. Figure 1 (B) is a diagram showing a second configuration example of a wireless communication system.

[0015] Figure 2 This is a diagram showing an example of a radio frame applied to a wireless communication system.

[0016] Figure 3 This diagram explains multi-power and interference suppression and cancellation techniques.

[0017] Figure 4 This is a diagram showing an example of retransmission in a wireless communication system.

[0018] Figure 5 This is a diagram showing an example of the hardware configuration of a base station and a terminal.

[0019] Figure 6 This is a block diagram showing an example of the configuration of a terminal.

[0020] Figure 7 This is a block diagram showing an example of the configuration of a base station.

[0021] Figure 8 This is a flowchart showing an example of processing (calculation of the number of retransmissions and the transmission power used in each retransmission) in the base station.

[0022] Figure 9 This is an example Figure 8 Flowchart of the details of step S001 in (first example).

[0023] Figure 10 This is an example Figure 8 Flowchart of the details of step S001 in (second example).

[0024] Figure 11 This is an example Figure 8 Flowchart of the detailed contents of step S002 in .

[0025] Figure 12 This is an example Figure 8 Flowchart of the detailed contents of step S003 in .

[0026] Figure 13 It is an explanatory diagram of the calculation formula of SINR.

[0027] Figure 14 This is a diagram showing an example of improved retransmission performed in a wireless communication system.

[0028] Figure 15 This is a diagram showing an experimental example related to retransmission. DETAILED DESCRIPTION

[0029] <Wireless Communication System Configuration>

[0030] Figure 1 (A) is a diagram showing a first configuration example of a wireless communication system according to an embodiment. Figure 1 (B) is a diagram illustrating a second configuration example of a wireless communication system. The wireless communication system according to the first configuration example includes a base station 1 and multiple terminals 2 (#0 to #K-1, where K is a natural number including 0) that wirelessly communicate with the base station 1. The base station 1 is an example of a receiving station, and the multiple terminals 2 are an example of multiple transmitting stations.

[0031] Each of the multiple terminals 2 is referred to as a UE (User Equipment). Each of the multiple terminals 2 includes an antenna 20, a wireless device 2a connected to the antenna 20, and a control device 2b connected to the wireless device 2a. The control device 2b acquires (receives) data from a sensor 3, etc. Furthermore, the control device 2b controls the wireless device 2a to transmit data signals or control signals to the base station 1, or to receive control signals from the base station 1. The wireless device 2a converts the target signal, including the data signal and the control signal, into a wireless signal and transmits it from the antenna 20. Furthermore, the wireless device 2a converts the wireless signal received from the antenna 20 into a signal format that can be processed by the control device 2b. The number of antennas 20 may be one or two or more. The terminal 2 may also have two or more antennas to perform MIMO (multiple-input and multiple-output) communication with the base station 1.

[0032] The base station 1 includes one or more antennas 10, a wireless device 1a connected to the antenna 10, and a control device 1b connected to the wireless device 1a. The wireless device 1a and the control device 1b have the same functions as the wireless device 2a and the control device 2b. The control device 2b can transmit data received from the terminal 2 to the server 4, etc. The control device 1b is an example of an information processing device (computer). In addition, the information processing device can be included in the base station 1, or it can be a terminal device (server, etc.) different from the base station 1 (independent of the base station 1). That is, the terminal device such as the server can also have the following configuration: the number of retransmissions and the transmission power used in each retransmission are calculated for multiple terminals 2, and the transmission is sent to each terminal 2.

[0033] According to the wireless communication system, for example, data (such as IoT (Internet of Things) data) acquired by multiple terminals 2 from sensors 3 can be stored in a server 4 via a base station 1. Furthermore, data from the server 4 can be transmitted to each of the multiple terminals 2 via the base station 1. The terminal 2 can be a fixed terminal or a mobile terminal. A mobile terminal can be a portable terminal or an in-vehicle terminal. An in-vehicle terminal can be a terminal mounted on or placed in a vehicle.

[0034] In addition, if Figure 1As shown in the second configuration example (B), a base station 1A having two or more distributed base stations and a control device 1b can be used instead of base station 1. A distributed base station includes an antenna 10 and a wireless device 1a and is called an RRH (Remote Radio Head). The control device 1b to which the two or more distributed base stations are connected is called a BBU (BaseBand Unit). The following description will describe the base station 1 having the first configuration example.

[0035] In the first and second configuration examples, base station 1 and multiple terminals 2 communicate (transmit / receive signals) using downlinks (DL) and uplinks (UL), respectively. DL is a link from base station 1 to terminal 2, and includes a control channel (control CH) used for transmitting (notifying) control signals. On the other hand, UL is a link from terminal 2 to base station 1, and includes a shared channel (shared CH) used for transmitting control CHs and data (user data). The shared CH is also called a data channel.

[0036] <Wireless Frame>

[0037] The UL signal and the DL signal are transmitted using the time domain allocated by time division multiplexing. Figure 2 FIG is a diagram showing an example of a radio frame used in a wireless communication system. Figure 2 In 5G, the wireless frame has a specified duration. The wireless frame length is 10ms in 5G, but it can be shorter or longer than 10ms. In addition, the wireless frame is divided into multiple subframes. In 5G, the subframe length is specified as 1ms, and the wireless frame is divided into 10 subframes. However, the subframe length and the number of divisions are not limited to the 5G example. The subframe can also be further divided into 2 or more time slots (time slot length: 500μm). As Figure 2 As shown, each subframe of a radio frame is allocated to DL or UL. Figure 2 In the example above, DL and UL are allocated in a pattern of one DL followed by four ULs. However, this allocation can be changed. Furthermore, the time slots in the subframe allocated to the UL are equally divided, with the first half mapped to the reference signal (RS) and the second half mapped to the data signal (DS). However, the arrangement of the reference signal and data signal in a single time slot can be changed as appropriate.

[0038] The reference signal is a signal known to the receiving station (base station 1) and is used to estimate the channel (called transmission path or communication path) of the wireless signal. The data signal is a signal obtained by modulating and encoding user data according to a specified MCS (Modulation and Coding Scheme).

[0039] <Characteristics of wireless communication systems>

[0040] In a wireless communication system, the uplink communication of data signals has the following features. First, the wireless communication system in this embodiment adopts configuration grant (CG). Figure 2 As shown, in UL communications, terminal 2 is notified in advance of the frequency channels and time slots available for CG, and a different reference signal is prepared for each terminal 2. This reference signal is then transmitted along with the data signal as the payload, thereby achieving CG. CG eliminates the communication delays associated with the communication permission (authorization) procedure for a terminal to obtain from the base station.

[0041] Second, in a wireless communication system, non-orthogonal multiple access is used to transmit wireless signals (reference signals and data signals) from multiple terminals 2 using the same frequency domain and the same time domain (time slot). At this time, in the base station 1, each terminal 2 transmits a wireless signal using the transmit power specified by the base station 1 in such a way as to generate a desired difference in received power between the terminals 2. NOMA can reduce the waiting time for signal transmission. However, the base station 1 needs to suppress and eliminate the inter-terminal interference from each terminal 2.

[0042] Figure 3 This diagram explains multi-power and interference suppression and cancellation technology. Figure 3 The left-hand diagram in FIG schematically illustrates the received power at base station 1 of wireless signals transmitted from terminal A, terminal B, and terminal C, serving as examples of multiple terminals 2. In this example, the data signals received from terminals A, B, and C are superimposed at the received power of base station 1 (superimposed signals). Furthermore, the power difference D1 between the received power of terminal A and terminal B, and the power difference D2 between the received power of terminal B and terminal C, are both greater than the received power difference (required power difference ΔP) required between terminals 2 in base station 1 for proper interference suppression and cancellation.

[0043] Base station 1 can determine the transmission path characteristics based on the reference signal, and use the transmission path characteristics to demodulate and decode the superimposed signal, thereby obtaining data from terminal A. In addition, the applicant of the present invention refers to a wireless communication system that includes the above-mentioned CG, UL communication using NOMA, and interference suppression and cancellation technology (SIC, etc.) as STABLE (Simultaneous Transmission Access Boosting Low-latEncy). However, the transmission (retransmission) control method involved in this application can be applied to wireless communication systems other than STABLE that apply NOMA.

[0044] As an algorithm for suppressing and eliminating interference of the signal of terminal A from the superimposed signal, the Successive Interference Cancellation (SIC) algorithm is used. SIC is an algorithm that serially determines signals from each terminal in descending order of received signal strength (Received Signal Strength Indicator: RSSI) and removes these signals one by one. The SIC algorithm uses an estimated value of the characteristics of the communication path (transmission path) between terminal 2 and base station 1 using a reference signal inherent to terminal 2. That is, the SIC algorithm uses the estimated value of the transmission path characteristic to reproduce (generate) the signal (called a replica signal) sent from terminal 2 (terminal A) with the largest received signal strength in the superimposed signal, and removes the replica from the superimposed signal. In this way, the interference caused by the data signal from terminal A is eliminated from the superimposed signal (refer to Figure 3 center picture).

[0045] The superimposed signal after the data signal from terminal A is eliminated can be demodulated and decoded using the transmission path characteristics based on the reference signal from terminal B to obtain the data from terminal B. Then, a replica signal of the data signal sent from terminal B is generated using the SIC algorithm, and the replica is removed from the superimposed signal. This eliminates the interference caused by the data signal from terminal B, and the remaining data signal sent from terminal C (refer to Figure 3 By demodulating and decoding the signal using the transmission path characteristics of the reference signal from terminal C, data from terminal C can be obtained.

[0046] Repetition

[0047] Furthermore, in wireless communication systems, multiple terminals 2 can each perform retransmissions. Retransmission refers to the continuous and repeated transmission of the same signal at a predetermined period (e.g., time slot). The signals transmitted by terminal 2 through retransmission are received and integrated by base station 1. By summing the received signals through integration, the signal-to-noise ratio (SNR) can be increased, improving reception quality (transmission loss).

[0048] When multiple terminals 2 performing UL communication using the same frequency domain and time domain perform retransmissions, the number of retransmissions (number of times the same signal is transmitted, number of time slots in which the same signal is transmitted) N is determined for the terminal 2 with the lowest received power (highest transmission loss) among the multiple terminals 2. N is a natural number.

[0049] Figure 4 is a diagram showing an example of retransmission. Figure 4In the example, it is assumed that there are 5 terminals 2 (K=5) performing UL communication based on NOMA. The identification information (user ID) of each of the 5 terminals 2 is "1", "2", "3", "4" and "5". The numbering order of terminals "1" to "5" is from large to small in terms of the received power at the base station 1. The received power of the signal from terminal "5" is the smallest, and the transmission loss is large. Therefore, the number of retransmissions N of terminal "5" is set to 6 times (N=6). In this case, the number of retransmissions N for the remaining terminals "1" to "4" is also set to the same number as that of terminal "5" (6 times).

[0050] However, considering that, for example, terminal "1" has the highest received power among the five terminals "2," the number of retransmissions required to achieve the desired reception quality (SINR or error rate) through integration is less than that for terminal "5." If terminal "5" were to continue transmitting with the same number of retransmissions as terminal "5," unnecessary power consumption would result, and retransmissions would not be considered appropriate. The following description details a wireless communication system that at least addresses the aforementioned issues.

[0051] <Hardware Configuration>

[0052] Figure 5 1 is a diagram showing an example of the hardware configuration of the base station 1 and the terminal 2. Figure 5 In the example, base station 1 has Figure 1 The M antennas 10 (10-1 to 10-M (M is a natural number)) shown in (A) are wireless devices (wireless processing devices) 1a and control devices 1b. Control devices 1b include a processor 11, a storage device (memory) 12, an internal interface 13, and a network interface 14 for communicating with other base stations and the like.

[0053] The processor 11 is also called a Central Processing Unit (CPU) or a Microprocessor Unit (MPU). The processor 11 is not limited to a single processor, but may also be a multi-processor structure. In addition, the processor 11 may also be a single physical CPU connected through a single socket with a multi-core structure. In addition, the processor 11 may also contain a computing device composed of various circuits such as a Digital Signal Processor (DSP) and a Graphics Processing Unit (GPU). In addition, the processor 11 may also cooperate with an integrated circuit (IC), other digital circuits, and analog circuits. Integrated circuits are, for example, LSIs, Application Specific Integrated Circuits (ASICs), or programmable logic devices (PLDs). PLDs are, for example, Field-Programmable Gate Arrays (FPGAs). The processor 11 may also be a component called, for example, a microcontroller (MCU), a SoC (System-on-a-chip), a system LSI, or a chipset. The processor 11 is an example of a control unit.

[0054] The storage device 12 stores a sequence of instructions (computer program) executed by the processor 11 or data processed by the processor 11. The internal interface (internal IF) 13 is a circuit that connects the processor 11 to various peripheral devices.

[0055] The network interface (NW-IF) 14 is a communication device for allowing the base station 1 to access a network connected to other base stations. The network connected to other base stations is also called a backhaul. The backhaul is, for example, a wired network based on optical communication.

[0056] Wireless device 1a includes a transmitter for sending wireless signals and a receiver for receiving wireless signals, and is connected to antennas 10 (10-1, ..., 10-M). Wireless device 1a may also have M systems of transmitters and receivers, the same number as the number of antennas.

[0057] exist Figure 5 In the example, terminal 2 includes an antenna 20, a wireless device (wireless processing unit) 2a, and a control unit 2b. Control unit 2b includes a processor 21, a storage device (memory) 22, an internal interface (internal IF) 23, and a network interface (NW-IF) 24 for communicating with other base stations, etc. Processor 21 is an example of a "control unit," and NW-IF 24 is an example of a "communication unit."

[0058] The processor 21 , the storage device 22 , the internal IF 23 , the NW-IF 24 , and the wireless device 2 a have the same functions as those of the processor 11 , the storage device 12 , the internal IF 13 , the NW-IF 14 , and the wireless device 1 a .

[0059] Terminal Configuration

[0060] Figure 6 This is a block diagram showing an example of the configuration of a terminal. Figure 5 The processor 21 shown executes a program stored in the storage device 22, and the terminal 2 operates as a device including an RS unit 210 and a DS unit 220. The RS unit 210 includes an RS generator 211. The RS generator 211 generates a reference signal.

[0061] DS unit 220 includes encoding unit 221 and modulation unit 222. Encoding unit 221 performs predetermined error correction coding on the input data (user data). Error correction coding is, for example, TURBO coding, but other coding formats are also possible. Furthermore, CRC (Cyclic Redundancy Check) coding, for example, may be performed before TURBO coding.

[0062] The modulation unit 222 performs digital modulation on the coded data to generate a data signal. Examples of digital modulation methods include Quadrature Amplitude Modulation (QAM) and Phase Shift Keying (PSK). The coding and modulation methods are based on the MCS set in the terminal 2.

[0063] Terminal 2 also includes a multiplexer (multiplexing unit) 202. The output of multiplexer 202 is connected to antenna 20. Multiplexer 202 switches to outputting a data signal after outputting a reference signal, thereby transmitting a reference signal and data signal corresponding to one time slot to antenna 20. Furthermore, a signal interval called a cyclic prefix (CP) may be provided at the beginning of each reference signal and data signal to compensate for the effects of delayed waves. During retransmission, the data signal is generated so that the same data signal is transmitted a number of times (N) specified by base station 1. Alternatively, the generated data signal may be copied and transmitted a number of times (N).

[0064] Base Station Configuration

[0065] Figure 7 1 is a diagram showing an example of the configuration of the base station 1. The processor 11 of the base station 1 executes the program stored in the storage device 12, so that the base station 1 functions as a Figure 7 The blocks shown in FIG. Figure 7As shown, base station 1 includes antenna 10, demultiplexer (separator) 101, RS unit 110, and DS unit 120. Demultiplexer 101 switches the signal received from antenna 10, sending the reference signal to integration unit 111 of RS unit 110 and the data signal to integration unit 121 of DS unit 120. At this time, the CP added to the reference signal and data signal is removed.

[0066] The integration unit 111 combines the reference signals received through retransmission to obtain a reference signal with sufficient received signal power. The communication path estimation unit 112 uses the integrated reference signals to calculate an estimated value of the communication path characteristics (channel vector). This estimated value is used for demodulation processing and replica signal generation in the demodulation unit 123.

[0067] The DS unit 120 includes an integration unit 121, a replica elimination unit 122, a demodulation unit 123, a decoding unit 124, and a replica generation unit 126. The integration unit 121 calculates the number of retransmissions N allocated to the target terminal 2 (terminal k). k The data signals of (N time slots) are combined to achieve an improvement in SNR.

[0068] The replica canceller 122 subtracts the replica signal generated by the replica generator 126 from the integrated received signal (superimposed signal). The demodulator 123 uses the estimated communication path characteristics from the communication path estimator 112 to separate the data signal from target terminal 2 (terminal 2 with the highest transmission power value among the terminals that transmitted the superimposed signal) and demodulates the separated data signals. The decoder 124 decodes the data corresponding to the encoding performed by the encoder 221 of terminal 2 and outputs the original data.

[0069] Replica generation unit 126 includes encoding unit 127, modulation unit 128, and multiplication unit 129. Encoding unit 127 and modulation unit 128 perform the encoding and digital modulation performed at terminal 2 on the data output from decoding unit 124. Multiplication unit 129 multiplies the modulated data by an estimated value of the communication path characteristics between target terminal 2 (terminal 2, the source of the decoded data) and base station 1. This generates a replica signal, which is supplied to replica elimination unit 122.

[0070] Calculating the number of retransmissions and transmission power

[0071] Figure 8 This is a flowchart showing an example of processing in a base station (calculation of the number of retransmissions and the transmission power used in each retransmission and retransmission). Figure 8The processing shown is performed, for example, by processor 11 of base station 1. This processing is initiated, for example, when multiple terminals 2 are transmitting data to base station 1 and base station 1 receives a data signal transmission request from a terminal 2 via a UL control channel. However, the start trigger is not limited to the above case. The input parameters to processor 11 are as follows.

[0072] Terminal ID (user ID) k: k is set to a value ranging from a minimum value of "0" to a maximum value of "K-1".

[0073] Maximum number of retransmissions N max The maximum number of retransmissions that can be used by a wireless communication system. For example, a 32-retransmission limit is being considered for 5G. The maximum number of retransmissions can be set appropriately and can be 32, greater, or less than 32.

[0074] BLER (Block Error Rate) characteristic S(γ) relative to SINR and MCS

[0075] BLER target value S target

[0076] Maximum transmit power P max,UE : The maximum transmission power allowed to be used by terminal 2

[0077] Base station noise power P N

[0078] Required power difference ΔP: The received power difference between the base station and the terminal that is required to implement appropriate interference suppression and eliminate

[0079] The input parameters are stored in, for example, storage device 12. The BLER characteristic versus SINR is prepared in storage device 12 as a correspondence table, for example, and the BLER characteristic versus the input SINR is retrieved. The input parameters may be stored somewhere other than storage device 12. Alternatively, processor 11 may obtain some or all of the input parameters from the network.

[0080] In step S001, the processor 11 calculates the transmission loss L between the base station 1 and the terminal 2 for a plurality of (K) terminals 2 performing UL communication based on NOMA. k In addition, the processor 11 sends K terminals 2 with a transmission loss of L k Arrange in ascending order (reception quality from best to worst).

[0081] In step S002, the processor 11 assigns an initial value of transmission power (initial power value P) to each of the K terminals 2. k,0 ).

[0082] In step S003, the processor 11 performs retransmission number N for each of the K terminals 2. k The designation and transmit power value P k,n The output parameters from the processor 11 at the end of step S003 are as follows.

[0083] The number of retransmissions N is specified for each of K terminals 2 (terminals with terminal IDs: k=0 to k-1). k

[0084] The transmission power value P used in each retransmission performed by each of the K terminals 2 k,n (n=1~maximum retransmission times max(N k ))

[0085] In step S004, the base station 1 notifies (transmits) information including output parameters via the DL control channel to each of the plurality of terminals 2. At this time, the base station 1 may include information indicating the retransmission start time slot and the frequency channel to be used in the notified information.

[0086] Figure 9 This is an example Figure 8 Flowchart showing the details of step S001 in FIG. 1 (first example). In step S011, the processor 11 instructs each terminal 2 to set the transmission power to the transmission power value P. k,UE The content of the control signal is sent, for example, via a DL control channel.

[0087] In step S012, the processor 11 measures the received signal strength r of the control signal transmitted from each terminal 2 to the base station 1 via the UL control channel. k,BS .

[0088] In step S013, the processor 11 calculates the transmission power value P k,UE Subtract the received signal strength r k,BS , thus calculating the transmission loss L between terminal 2 and base station 1 k In step S013, when the base station 1 has a plurality of antennas 10, for example, the average value of the transmission loss associated with the received signal of each antenna 10 may be used as the transmission loss L. k .

[0089] Figure 10 This is an example Figure 8 In step S021, the processor 11 instructs each terminal 2 to measure and report the received signal strength of the transmission signal (designated transmission signal) to the terminal 2 designated by the base station 1 via the DL control channel.

[0090] In step S022, the received signal strength r of the designated transmission signal transmitted from the base station 1 is measured at each terminal 2. k,UE Each terminal 2 sends a signal including the received signal strength r to the base station 1 via the UL control channel. k,UE Report of the measurement results.

[0091] In step S023, the processor 11 of the base station 1 receives the report from each terminal 2, and determines the transmission power value p of the designated transmission signal from the base station 1. k,BS Subtract the received signal strength r contained in the report k,UE , thereby calculating the transmission loss L associated with each terminal 2 k When calculating the transmission loss L k When using the .sup.th method, you can use either the first or second example.

[0092] Figure 11 This is an example Figure 8 Flowchart of the details of step S002 in FIG. In step S031, the processor 11 sets the value of the serial number k of one of the K terminals 2 (terminals #0 to #K-1) to 0. For the K terminals 2, the terminal ID, i.e., the value of k=0 to K-1, is set to 0 with a transmission loss L. k The terminal 2 with k=0 indicates a transmission loss of L. k The smallest terminal is 2.

[0093] In step S032 , the processor 11 determines whether the current k value is the minimum k value, ie, 0. If it is determined that the k value is 0, the process proceeds to step S033 , and otherwise, the process proceeds to step S034 .

[0094] In step S033, the processor 11 sets the initial power value P to the terminal 2 with k=0. 0,0 Set to the maximum transmission power P max,UE But it can also be replaced by the maximum transmission power P max,UE And use less than P max,UE Then, the process proceeds to step S035.

[0095] When the process proceeds to step S034, the processor 11 sets the initial power value P of the terminal 2 to k,0 The smaller value between the first value and the second value shown below is determined.

[0096] First value: Maximum transmit power P of terminal 2 max,UE

[0097] Second value: Power value P from terminal 2 (terminal k-1) at k-1 k-1,0 Subtract the transmission loss L of terminal 2 (terminal k) from kk Transmission loss L with terminal k-1 k-1 The difference between the required power difference ΔP and the value after deducting the required power difference ΔP

[0098] The second value is smaller than the first value. The second value is equal to or greater than the required power difference ΔP, so that a sufficient power difference can be obtained between the terminals 2 .

[0099] In step S035, the processor 11 determines whether the current k value is K-1 (the maximum value of k). If it is determined that the k value is K-1, Figure 11 The process ends. If not, the process proceeds to step S036. In step S036, the k value is incremented (the current k value is added by 1), and the process returns to step S032.

[0100] Figure 12 This is an example Figure 8 In step S041, the processor 11 sets the value of the terminal k to 0 and the value of the number of retransmissions n to 1.

[0101] In step S042, the SINRγ corresponding to the number of retransmissions n is calculated. k,n γ k,n The value can be Figure 13 Calculate using the formula shown. That is, γ k,n The value of P is obtained by subtracting the value of B from the value of A in the formula N The value of A in the formula is the power value (integrated value) after the terminal 2 with terminal ID = k has retransmitted n times. In addition, B in the formula is the interference power received from the terminal 2 other than the terminal ID = k. N As shown above, this is the noise power of base station 1.

[0102] In step S043, the processor 11 calculates the expected number of retransmissions N k As the expected number of retransmissions N k , for example, set the following value to N k That is, the BLER characteristic S(γ) relative to the SINR calculated in step S042 is obtained so that the BLER characteristic S(γ) is less than the target BLER value S target The value of N when it becomes the minimum value is set as N k This means that the current value of k at terminal 2 is N k After the retransmission, retransmission is stopped (no retransmission is performed in the next time slot). Then, the process proceeds to step S044.

[0103] However, the value of N obtained in step S043 is the maximum number of retransmissions N. maxIn the above case, the process proceeds to step S046. In step S046, the processor 11 sets N k The value is set to N max .Then, Figure 12 The process ends.

[0104] In step S044, the power value P 从k+1起,n+1 That is, the processor 11 performs the retransmission number N=N calculated in step S043 for the terminal 2 starting from k+1 with respect to the current k value. k The calculation of the transmission power value can be performed by the same process as step S002 ( Figure 11 The same process as the process of S031 to S036 shown in FIG. 1 is performed. However, this process is performed on all the data except the set expected number of retransmissions N. k The remaining terminals 2 except the terminal 2 (the terminal 2 that does not retransmit in the next time slot n+1) have a transmission loss of L k This is done in a state where terminal IDs 0 to K-1 are assigned in ascending order.

[0105] In step S045, the processor 11 determines whether the current value of k is K-1. If it is determined that the value of k is K-1, Figure 12 The process ends. If not, the process proceeds to step S047. In step S047, the processor 11 increments the k value and the process returns to step S042.

[0106] Figure 14 FIG. 1 is a diagram showing an example of improved retransmission performed in a wireless communication system. Figure 4 The terminal 2 of the terminal ID "1" to "5" shown in the figure performs Figures 8 to 12 After the processing involved in the flow shown, the following situation occurs. That is, with the transmission loss L k Arrange the terminals "1" to "5" in ascending order (step S001), and assign initial power values ​​to each of them (step S002). k The maximum transmission power is allocated to the smallest terminal "1", and initial power values ​​are set for terminals "2" to "5" so that the received power at the base station 1 has a power difference greater than the required power difference ΔP.

[0107] Then, in step S003 Figure 12 In the process of k is set to 2 (step S043), the retransmission of terminal "1" becomes the following state: Figure 14 It is performed in the first (n=1) and second (n=2) time slots in the time slot and stops at the time slot n=2.

[0108] At this time, for the next time slot n = 3, the transmission power values ​​allocated to terminals "2" through "5" (excluding terminal "1") are updated (step S044). The transmission power value of terminal "2" is updated to the maximum transmission power, and the transmission power of terminals "3" through "5" is set to a value that sets a power difference greater than the required power difference ΔP in the received power at base station 1. As a result, the received power of terminals "2" through "5" at time slot n = 3 increases.

[0109] If in the subsequent step S043, the number of retransmissions N associated with terminal "2" k If it is set to 3, the retransmission of terminal "2" stops at time slot n = 3. Therefore, the transmission power values ​​of the remaining terminals "3" to "5" in the next time slot n = 4 are updated to increased values ​​(step S044), and the reception power at base station 1 increases.

[0110] If in the subsequent step S043, the number of retransmissions N associated with terminal "3" k If the power is set to 4, the retransmission of terminal "3" stops at time slot n = 4. Therefore, the transmission power values ​​of the remaining terminals "4" and "5" in the next time slot n = 5 are updated to increased values ​​(step S044), and the reception power at base station 1 increases.

[0111] If in the subsequent step S043, the number of retransmissions N associated with terminal "4" k is set to 5, the retransmission of terminal "4" stops at time slot n=5. Therefore, the transmission power value of the remaining terminal "5" in the next time slot n=6 is updated to a higher value (step S044). However, in the present embodiment, in the subsequent step S043, the retransmission number N for terminal "5" is set to 5. k It is set to 5. In this case, the retransmission of the terminal "5" stops at the time slot n=5, and therefore the base station 1 does not notify the terminal "5" of the transmission power value used at the time slot n=6.

[0112] Therefore, in Figure 13 In the example shown, signals related to retransmissions at time slot n = 6 are not transmitted. This allows time slot n = 6 to be effectively used for other purposes. Furthermore, since the number of retransmissions for each of terminals "1" through "5" is reduced, power consumption can be reduced. Furthermore, since the transmission power values ​​for terminals "2" through "5" are updated to increase, received power is increased, improving reception quality. In this way, terminals "1" through "5," representing multiple terminals 2, can perform appropriate retransmissions.

[0113] Figure 15FIG1 is a diagram showing an experimental example related to retransmission performed using a wireless communication system according to an embodiment. The environment in the experimental example is as follows.

[0114] ISD (Inter-Site Distance): 1732m

[0115] NLOS (Non Line Of Sight) environment

[0116] Maximum transmit power: 23dBm

[0117] Number of antennas for base station 1: 2

[0118] MCS = 1

[0119] exist Figure 15 In the graph on the left, multiple user IDs (terminals 2) "1" to "6" are arranged in order of transmission loss from small to large. The vertical axis of the graph is the number of retransmissions. When the number of retransmissions between multiple terminals 2 is the same, the minimum, maximum, and average values ​​of the number of retransmissions for user IDs "1" to "6" are fixed and have nothing to do with the value of transmission loss. In contrast, as shown in the graph on the right, for user IDs "1" to "6", the minimum, maximum, and average values ​​of the number of retransmissions are fixed. Figures 8 to 12 After this processing, the lower the transmission loss, the lower the expected number of retransmissions. The graph on the right shows a maximum reduction of approximately 1 / 4 of the number of retransmissions compared to the graph on the left. Furthermore, the average number of retransmissions also decreases, demonstrating improvement.

[0120] <Effects of the Implementation Method>

[0121] The wireless communication system according to the embodiment includes a plurality of transmitting stations (terminals 2) that are non-orthogonal to the receiving station (base station 1) of the wireless communication target ( Figure 1 (A), Figure 1 (B)). Multiple terminals 2 can each transmit the same signal to the base station 1 a predetermined number of times in a common predetermined period (time slot) through retransmission. ( Figure 4 ).

[0122] The information processing device included in the base station 1, that is, the control device 1b including the processor 11, calculates the initial value of the transmission power to be allocated to each of the plurality of terminals 2 in the following manner: the initial value of the transmission power increases as the reception quality at the base station 1 becomes better (the transmission loss becomes smaller), and the reception power difference at the base station 1 required between the terminals 2 (required power difference ΔP) is ensured ( Figure 8 S002, Figure 11). In addition, the control device 1b performs the following processing: based on the reception quality index value (SINR) at the base station 1, calculates the number of retransmissions ( Figure 12 S043).

[0123] With the above configuration, compared to a case where the number of retransmissions for multiple terminals is matched to the number of retransmissions for terminal 2 with the greatest transmission loss among multiple terminals 2, the number of retransmissions for terminal 2 with the smallest transmission loss (to which the initial value of the largest transmission power is allocated) can be reduced. This reduces the power consumption of that terminal 2. In other words, appropriate retransmissions can be performed.

[0124] In addition, in the embodiment, the control device 1b or the processor 11 can further perform the following processing: for the remaining terminals 2 after excluding the terminal 2 (equivalent to the first transmission station) for which the desired number of retransmissions is set from the plurality of terminals 2, the number of retransmissions and the transmission power used after excluding the terminal 2 for which the desired number of retransmissions is set are calculated ( Figure 12 S044). This can reduce the number of retransmissions by the remaining terminals 2. In addition, by reducing the number of retransmissions, the number of cycles (time slots) used for retransmission can be reduced, thereby achieving efficient use of resources.

[0125] In addition, in the embodiment, the control device 1b or the processor 11 can allocate a larger transmission power to each of the remaining terminals 2 than the transmission power allocated before the terminal 2 for which the desired number of retransmissions is set is removed. By increasing the transmission power, the reception quality (SINR or error rate) at the base station 1 can be improved ( Figure 12 S044, Figure 11 S033).

[0126] In addition, in the embodiment, the control device 1b or the processor 11 can calculate the transmission loss ( Figure 9 ).

[0127] In addition, in the embodiment, the control device 1b or the processor 11 can calculate the transmission loss ( Figure 10 ).

[0128] In addition, in the embodiment, the control device 1b or the processor 11 allocates the maximum allocable transmission power to the transmission site with the best reception quality (the terminal 2 with the smallest transmission loss) among the multiple terminals 2 in the transmission power allocation. In addition, the control device 1b or the processor 11 calculates the transmission power ( ) to be allocated to the remaining transmission sites (terminals 2) except the transmission site with the best reception quality in a manner that is lower than the maximum transmission power and ensures the required power difference ΔP. Figure 11 S034).

[0129] In addition, in the embodiment, the control device 1b or the processor 11 calculates the reception quality (S(γ)) at different retransmission times n when calculating the retransmission times of the terminal 2 to which the maximum transmission power is allocated among the plurality of terminals 2. And the control device 1b or the processor 11 determines whether the reception quality obtained by the calculation satisfies the expected reception quality (S target ) is determined as the minimum number of retransmissions of the terminal 2 ( Figure 12 S043).

[0130] In addition, in the embodiment, the base station 1, which is the receiving station, can transmit information including the number of retransmissions allocated to each of the terminals 2 and the transmission power used in each retransmission to each of the terminals 2 via the downlink control channel ( Figure 8 Thus, the plurality of terminals 2 can each retransmit using a transmission power according to the information.

[0131] As long as no technical contradictions arise, the processes and units described in this disclosure can be freely combined and implemented. In addition, a process described as being performed by one device can also be shared and executed by multiple devices. Alternatively, a process described as being performed by different devices can also be performed by a single device. In a computer system, the hardware configuration (server configuration) that implements each function can be flexibly changed.

[0132] The present disclosure can also be implemented in the following manner, that is, a computer program having the functions described in the above embodiment is provided to a computer, and one or more processors possessed by the computer read and execute the computer program to achieve the above. Such a computer program can be provided to the computer via a non-temporary computer-readable storage medium that can be connected to the system bus of the computer, or it can be provided to the computer via a network. Non-temporary computer-readable storage media include, for example, any type of disk (floppy disk (registered trademark), hard disk drive (HDD)), optical disk (CD-ROM, DVD disk, Blu-ray disk, etc.), read-only memory (ROM), random access memory (RAM), EPROM, EEPROM, magnetic card, flash memory, optical card, and any type of medium suitable for storing electronic instructions.

[0133] Description of the label

[0134] 1…base station

[0135] 1a, 2a…Wireless equipment (wireless processing device)

[0136] 1b, 2b…control device

[0137] 2…Terminal

[0138] 10, 20...antenna

[0139] 11, 21…Processor

[0140] 12, 22… Storage device

[0141] 13, 23…Internal interface

[0142] 14, 24... network interface

[0143] 101…Demultiplexer

[0144] 110, 210…RS department

[0145] 111, 121…Integral

[0146] 112 ...Communication path estimation unit

[0147] 120, 220…DS Department

[0148] 122…Copy Elimination Department

[0149] 123…Demodulation unit

[0150] 124…Decoding unit

[0151] 126…Copy Generation Department

[0152] 127…Encoding Department

[0153] 128…Modulation unit

[0154] 129…Multiplication unit

[0155] 202…Multiplexer

[0156] 220…DS Department

[0157] 221…Coding Department

[0158] 222…Modulation Department

Claims

1. A transmission control method, as a transmission control method for multiple transmission stations using non-orthogonal multiple access with a receiving station of a wireless communication target, wherein the multiple transmission stations can each transmit the same signal to the receiving station continuously a predetermined number of times with a common predetermined period by retransmission, wherein: The transmission control method causes the information processing device to perform the following processing: calculating initial values ​​of transmission power to be allocated to each of the plurality of transmission sites, the initial values ​​of the transmission power being higher as the reception quality at the receiving site is better, and being able to ensure a required reception power difference between the transmission sites; and The number of retransmissions of a first transmission site to which the initial value of the largest transmission power is assigned among the plurality of transmission sites is calculated based on the index value of the reception quality.

2. The transmission control method according to claim 1, wherein: The information processing device further performs the following processing: removing the first sending site from the plurality of sending sites; and For the remaining sending sites after removing the first sending site, the number of retransmissions and the sending power used after removing the first sending site are calculated respectively.

3. The transmission control method according to claim 2, wherein: The information processing device allocates, to the remaining transmission sites, a transmission power greater than the transmission power allocated before the first transmission site is removed.

4. The transmission control method according to any one of claims 1 to 3, wherein: The reception quality is the transmission loss between the receiving site and each of the plurality of sending sites.

5. The transmission control method according to claim 4, wherein: The information processing device calculates the transmission loss using received signal strength at the receiving site when each of the plurality of transmitting sites transmits a signal to the receiving site at a predetermined transmission power. The transmission control method according to claim 4 , wherein: The information processing device calculates the transmission loss using received signal strengths at each of the plurality of transmission sites when the receiving site transmits a signal to each of the plurality of transmission sites at a predetermined transmission power.

7. The transmission control method according to any one of claims 1 to 3, wherein: In allocating transmission power, the information processing device allocates the maximum allocable transmission power to the transmission site with the best reception quality among the multiple transmission sites, and calculates the transmission power allocated to the remaining transmission sites except the transmission site with the best reception quality within a power range lower than the maximum transmission power and in a manner that ensures the required reception power difference between the transmission sites.

8. The transmission control method according to any one of claims 1 to 3, wherein: When calculating the number of retransmissions of the first sending site, the information processing device calculates the reception quality under different retransmission numbers, and determines the minimum number of retransmissions at which the calculated reception quality meets the expected reception quality as the number of retransmissions of the first sending site.

9. The transmission control method according to any one of claims 1 to 3, wherein: The receiving station transmits information including the number of retransmissions allocated to each of the plurality of transmitting stations and the transmission power used in each retransmission to each of the plurality of transmitting stations via a downlink control channel.

10. An information processing device, It includes a control unit, The control unit performs the following processing on a plurality of transmitting stations that are non-orthogonal to a receiving station of a wireless communication target and can transmit the same signal to the receiving station continuously a predetermined number of times in a common predetermined period by retransmission: calculating initial values ​​of transmission power to be allocated to each of the plurality of transmission sites, the initial values ​​of the transmission power being higher as the reception quality at the receiving site is better, and being able to ensure a required reception power difference between the transmission sites; and The number of retransmissions of a first transmission site to which the initial value of the largest transmission power is assigned among the plurality of transmission sites is calculated based on the index value of the reception quality. The information processing apparatus according to claim 10 , wherein: The control unit also performs the following processing: removing the first sending site from the plurality of sending sites; and For the remaining sending sites after removing the first sending site, the number of retransmissions and the sending power used after removing the first sending site are calculated respectively.

12. The information processing apparatus according to claim 11, wherein: The control unit allocates, to each of the remaining transmission sites, a transmission power greater than the transmission power allocated before the first transmission site is removed.

13. The information processing apparatus according to any one of claims 10 to 12, wherein: The reception quality is the transmission loss between the receiving site and each of the plurality of sending sites. The information processing apparatus according to claim 13 , wherein: The control unit calculates the transmission loss using reception signal strength at the receiving site when each of the plurality of transmission sites transmits a signal to the receiving site at a predetermined transmission power.

15. The information processing apparatus according to claim 13, wherein: The control unit calculates the transmission loss using received signal strengths at each of the plurality of transmission sites when the reception site transmits a signal to each of the plurality of transmission sites at a predetermined transmission power.

16. The information processing apparatus according to any one of claims 10 to 12, wherein: In the allocation of the transmission power, the control unit allocates the maximum allocable transmission power to the transmission site with the best reception quality among the multiple transmission sites, and calculates the transmission powers allocated to the remaining transmission sites except the transmission site with the best reception quality within a power range lower than the maximum transmission power and in a manner that ensures the required reception power difference between the transmission sites.

17. The information processing apparatus according to any one of claims 10 to 12, wherein: The control unit calculates the reception quality under different retransmission times when calculating the retransmission times of the first sending site, and determines the minimum retransmission time at which the reception quality obtained by calculation meets the expected reception quality as the retransmission time of the first sending site.

18. The information processing apparatus according to any one of claims 10 to 12, wherein: The receiving station transmits the number of retransmissions allocated to each of the plurality of transmitting stations and the transmission power used in each retransmission to each of the plurality of transmitting stations via a downlink control channel.

19. A transmission control method for a first transmitting station included in a plurality of transmitting stations that perform non-orthogonal multiple access with a receiving station of a wireless communication target, wherein the plurality of transmitting stations are capable of transmitting the same signal to the receiving station continuously a predetermined number of times with a common predetermined period by retransmission. The transmission control method includes causing the first transmission site to perform the following processing: receiving information including the number of retransmissions to the receiving station and the transmission power used in each retransmission, wherein calculating initial values ​​of transmission power to be allocated to each of the plurality of transmission sites, the initial values ​​of the transmission power being higher as the reception quality at the receiving site becomes better while ensuring a required reception power difference between the transmission sites, and calculating, based on an index value of the reception quality, the number of retransmissions for a first transmission site to which the largest initial value of transmission power is allocated among the plurality of transmission sites; and Resending based on the information, The information includes a first value as the initial value of the transmission power assigned to the first transmitting site as the transmission power, and also includes a second value greater than the first value, wherein the second value is the transmission power used after the retransmission of the transmitting site assigned the maximum value is stopped when the first value is not the maximum value of the initial values ​​of the transmission power assigned to the multiple transmitting sites.

20. The transmission control method according to claim 19, wherein: The first sending station receives the information from the receiving station via a downlink control channel.

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