User equipment, method, and program

Abstract

The present invention improves the efficiency of reporting of information relating to propagation characteristics to a network by a UE. A UE: acquires first information relating to the loss of a signal transmitted coherently from one or a plurality of transmission / reception points (TRPs) to the UE; receives, from a network, third information indicating a relationship between an allowable range of the loss and the resolution of information relating to propagation characteristics between the UE and the one or more TRPs reported from the UE to the network, the resolution becoming higher the narrower the allowable range of the loss; acquires a first allowable range of signal loss at the UE on the basis of the first information and second information indicating a relationship between the value of a factor affecting the signal loss and a first value relating to the loss that is allowed in accordance with the value of the factor; and determines the resolution to be applied to the UE on the basis of the first allowable range and the third information.

Description

User equipment, methods, and programs

[0001] This disclosure relates to wireless communication.

[0002] In wireless communications such as 5th Generation Mobile Communication Systems (5G), distributed MIMO (Multi-Input Multi-Output) has been proposed, which involves selecting one or more distributed stations near a mobile station from among multiple distributed stations distributed within the communication area of ​​a single base station to communicate with. According to distributed MIMO, by appropriately combining radio waves transmitted simultaneously from multiple distributed stations, the received signal power at the mobile station can be improved and throughput can be increased.

[0003] In coordinated transmission between multiple distributed base stations (mTRPs, hereinafter referred to as distributed stations), such as in distributed MIMO, the technique of improving received signal power by ensuring that the transmitted signals from each distributed station are received in phase at the User Equipment (UE) is called Coherent Joint Transmission (CJT). For example, in coordinated transmission by N distributed stations, assuming that the transmitted power of each distributed station is equal, theoretically, with CJT, the received signal power at the UE will be N squared times the received signal power of a signal from a single distributed station. By improving the received signal power through CJT, throughput can be improved and latency can be reduced.

[0004] When there is a phase offset in the carrier waves between multiple distributed stations performing coordinated transmission, a loss of received signal power occurs when the received signals are combined at the UE. This loss of received signal power is the difference between the theoretical value of the received signal power obtained by the CJT and the actual received signal. To compensate for the carrier wave phase offset of each distributed station, the UE measures the phase offset value for each distributed station and reports it to each station.

[0005] Regarding the resolution of the phase offset of UE, the phase offset Φ in the subband σ of distributed station n ｎ，σIt is disclosed that, for a resolution MΦ, it can take one of the following values: {0, 2π / (MΦ-1), 4π / (MΦ-1), ..., (MΦ-2)2π / (MΦ-1), "invalid"} (for example, Non-Patent Document 1). It is disclosed that the resolution MΦ of the phase offset is determined by the network and notified to each UE.

[0006] Qualcomm Incorporated, CSI enhancements for >32 ports and UE-assisted CJT, 3GPP TSG RAN WG1 #117, R1-2405149, May 24, 2024, pp.17

[0007] One aspect of the present disclosure is a UE comprising a control unit that performs: acquiring first information relating to the loss of a signal coordinately transmitted from one or more transmission / reception points (TRPs) to a user device (UE); receiving third information from a network indicating a relationship between the acceptable range of loss and the resolution, wherein the narrower the acceptable range of loss, the higher the resolution of the information regarding the propagation characteristics between the one or more TRPs and the UE reported from the UE to the network; acquiring a first acceptable range of signal loss in the UE based on the first information and second information indicating a relationship between the value of a factor affecting the signal loss and a first value relating to the loss that is acceptable depending on the value of the factor; and determining the resolution to be applied to the UE based on the first acceptable range and the third information.

[0008] Another aspect of the present disclosure is a method for a computer to perform the following: acquire first information relating to the loss of a signal coordinately transmitted from one or more transmission / reception points (TRPs) to a user device (UE); receive third information from a network indicating a relationship between the loss tolerance and the resolution, wherein the narrower the loss tolerance, the higher the resolution of the information regarding the propagation characteristics between the one or more TRPs and the UE reported from the UE to the network; acquire a first loss tolerance in the UE based on the first information and second information indicating a relationship between the value of a factor affecting the signal loss and a first value relating to the loss that is permissible depending on the value of the factor; and determine the resolution to be applied to the UE based on the first tolerance and the third information.

[0009] Another aspect of the present disclosure is a program for causing a computer to perform the following: acquire first information relating to the loss of a signal coordinately transmitted from one or more transmission / reception points (TRPs) to a user device (UE); receive third information from a network indicating a relationship between the loss tolerance and the resolution, wherein the narrower the loss tolerance, the higher the resolution of the information regarding the propagation characteristics between the one or more TRPs and the UE reported from the UE to the network; acquire a first loss tolerance in the UE based on the first information and second information indicating a relationship between the value of a factor affecting the signal loss and a first value relating to the loss tolerance depending on the value of the factor; and determine the resolution to be applied to the UE based on the first loss tolerance and the third information.

[0010] According to one aspect of this disclosure, an information processing device, method, and program can be provided that can improve the efficiency of reporting information on propagation characteristics by UE.

[0011] Figure 1 is a diagram showing an example of the system configuration of a communication system according to the first embodiment. Figure 2 is an example of the CJT sequence in the communication system according to the first embodiment. Figure 3 is a diagram illustrating the hardware configuration of the control device. Figure 4 is a diagram showing an example of the functional configuration of the control device. Figure 5 is an example of an MCS index table. Figure 6 is a graph showing an example of loss margin-resolution correspondence information. Figure 7 is an example of a flowchart of the resolution MΦ determination process according to the first embodiment. Figure 8 is an example of the CJT sequence in a communication system according to modification 1 of the first embodiment. Figure 9 is an example of a flowchart of the MCS index update process according to modification 2 of the first embodiment. Figure 10 is an example of a flowchart of the resolution MΦ determination process according to the second embodiment. Figure 11 is an example of a flowchart of the resolution MΦ determination process according to modification 1 of the second embodiment. Figure 12 is an example of the CJT sequence in a communication system according to the third embodiment. Figure 13 is a diagram showing an example of the hardware configuration of the UE. Figure 14 is a diagram showing an example of the functional configuration of the UE.

[0012] While a high resolution for the phase offset allows for precise adjustment, it increases the number of bits required to represent a single phase offset, thus increasing the data size reported by the UE to the network. When the measurement interval is relatively longer than the frequency fluctuation, resulting in low frequency stability, and when high gain is not required, there is no need to increase the resolution of the phase offset. Lowering the resolution can reduce the data size reported to the network.

[0013] The resolution of the phase offset is affected by gain and deviation. Gain and deviation influence each other with signal loss and the acceptable range of signal loss. For example, when high gain is required, it is necessary to keep signal loss low. For example, when communication quality stability is required, that is, when deviation must be kept low, it is necessary to keep signal loss low or have a wide acceptable range of signal loss. In one aspect of this disclosure, signal loss and the acceptable range of signal loss are used as values ​​that reflect fluctuations in gain and deviation, and the resolution of information regarding propagation characteristics is determined based on the acceptable range of signal loss in the current propagation environment.

[0014] More specifically, one aspect of the present disclosure is a UE comprising a control unit that performs the following: acquiring first information relating to the loss of a signal coordinately transmitted from one or more transmission / reception points (TRPs) to a user equipment (UE); receiving third information from a network; acquiring a first acceptable range of signal loss in the UE based on the first information and second information showing a relationship between the value of a factor affecting the signal loss and a first value relating to the loss that is permissible depending on the value of the factor; and determining the resolution of information relating to the propagation characteristics between the one or more TRPs and the UE, which is applied to the UE and reported from the UE to the network, based on the first acceptable range and the third information. The third information shows a relationship between the acceptable range of loss and the resolution, wherein the resolution is higher as the acceptable range of loss narrows.

[0015] A UE is, for example, a wireless communication device such as a smartphone, tablet, or in-vehicle device. However, it is not limited to these, and a UE may also be a stationary PC (Personal Computer) or a fixedly installed IoT device. The control unit is a processor such as a CPU (Central Processing Unit). A UE is also called a terminal station, or a mobile station if it is mobile. A TRP is, for example, an antenna and / or antenna port provided in a base station, a relay station, or a UE operating as a relay station. Forms of coordinated transmission from multiple TRPs to a UE include, for example, CJT, JT, CoMP (Coordinated Multi-Point), or distributed MIMO.

[0016] The first information and first value relating to signal loss are, for example, values ​​of communication quality indicators such as SNR (Signal-to-Noise Ratio), L1-RSRP (Reference Signal Received Power), and RSSI (Received Signal Strength Indicator). Also, for example, when a signal is transmitted from multiple TRPs to a UE via CJT, the signal loss indicated by the first information includes the difference between the received signal power in the case of an ideal CJT and the received signal power of the signal actually received. One of the factors contributing to signal loss in the case of CJT is phase offset.

[0017] Factors influencing signal loss include, for example, the Modulation and Coding Scheme (MCS) index, the application's required rate and transmission delay, carrier frequency, UE's speed (including Doppler frequency), the distance between the UE and the TRP (including propagation delay), and atmospheric conditions such as temperature and humidity. If the factor influencing signal loss is the MCS index, the first value is the value relating to the acceptable or minimum signal loss that occurs when that MCS index is applied. If the factor influencing signal loss is the application's required rate, the first value is the value relating to the acceptable signal loss when applying an MCS index that can achieve a rate that satisfies that required rate. The MCS index is an index that indicates the combination of modulation and coding.

[0018] The information regarding the propagation characteristics between the one or more TRPs and the UE reported from the UE to the network includes, for example, interference measurement information such as phase offset, L1-RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), RSSI (Received Signal Strength Indicator), SINR (Signal to Interference plus Noise Ratio), CSI (Channel State Information), and inter-cell interference, all measured by the UE.

[0019] According to one aspect of this disclosure, the resolution is determined based on an acceptable range of signal loss that reflects fluctuations in gain and deviation that affect the resolution of the propagation characteristics information reported from the UE to the network. This makes it possible to set the resolution of the propagation characteristics information reported from the UE to the network to an appropriate value. For example, when high gain is required, or when high frequency stability is required, and it is necessary to keep signal loss to a minimum or to allow for a wide range of loss, the resolution can be set to a high level, allowing for precise adjustment of phase offsets, etc. For example, when high gain is not required, or when low frequency stability is required, and it is not necessary to keep signal loss to a minimum or to allow for a wide range of loss, the resolution can be set to a low level, which can reduce the data size reported to the network.

[0020] In one aspect of the present disclosure, the control unit may further perform the following: first information, a second value relating to the signal loss at the UE based on measured values ​​relating to the propagation environment between the one or more TRPs and the UE. In this case, the control unit may obtain a first tolerance range based on the first information and, as second information, a correspondence between the MCS index and the first value for one or more first MCS indices. Since the first information is the signal loss at the UE obtained based on measured values, the first tolerance range of signal loss can be obtained as reflecting the current propagation environment.

[0021] Furthermore, the control unit may obtain the value indicating the smallest loss among the one or more first values ​​corresponding to each of the one or more first MCS indices, and subtract this value indicating the smallest loss from the second value to obtain the first tolerance range. This makes it possible to determine the first tolerance range of signal loss as wide as possible. By determining the first tolerance range of signal loss as wide as possible, it is possible to prevent the resolution of the information reported to the network from being determined to a value that affects the gain and the stability of the communication quality.

[0022] Furthermore, the control unit may acquire one or more MCS indices as the first MCS index, which are associated with a first value that indicates a loss greater than the loss indicated by the second value relating to the signal loss in the UE based on the measured value, among a plurality of associations between the MCS index and the first value. This makes it possible to acquire a first acceptable range of signal loss that reflects the current propagation environment.

[0023] Furthermore, the control unit may also receive from the network one or more MCS indices from among multiple associations of MCS index, spectral efficiency, and signal loss, which are associated with a spectral efficiency equal to or greater than the spectral efficiency required by the application's rate, as the one or more first MCS indices. This makes it possible to determine a first acceptable range of signal loss within the range permitted by the application's requirements.

[0024] Furthermore, the control unit may also obtain from the network, in a plurality of correspondences between MCS index, spectral efficiency, and signal loss, one or more second MCS indices that are associated with a spectral efficiency equal to or greater than the spectral efficiency corresponding to the application's required rate, and which are associated with a first value that indicates a loss greater than the loss indicated by the second value, as the one or more first MCS indices. This makes it possible to determine a first acceptable range of signal loss within a range that is acceptable according to the application requirements and within a range that is acceptable under the current propagation environment.

[0025] In this case, the control unit may further instruct the application to reduce the request rate if there is no MCS index among the one or more second MCS indices that corresponds to a first value that indicates a loss greater than the loss indicated by the second value. This can reduce the excessively high request rate from the application and suppress a deterioration in communication quality.

[0026] Furthermore, the control unit may, if the third MCS index used by the one or more TRPs and the UE is not included in the one or more first MCS indexes, determine one of the one or more first MCS indexes as the new third MCS index. This allows the MCS indexes used by the TRPs and UEs to be updated to suit the current propagation environment.

[0027] Furthermore, the control unit may determine the MCS index among the one or more first MCS indices that has the smallest loss indicated by the associated first value as a new third MCS index. This allows the MCS index used by the TRP and UE to be updated to one that is expected to have the smallest signal loss in the current propagation environment.

[0028] In one aspect of the present disclosure, the control unit may further perform the acquisition of the measurement value based on the downlink measurement signals received from the one or more TRPs. The downlink measurement signals may be downlink reference signals, SSS (Secondary Synchronization Signal), or downlink data signals. The reference signals used as downlink measurement signals may be, for example, CSI (Channel State Information)-RS, DM-RS, PT-RS, PRS (Positioning RS), or any other downlink reference signal.

[0029] In this case, since the propagation characteristics measured by the UE in the direction from one or more TRPs to UE are obtained, the resolution can be determined using more accurate information on the propagation characteristics in the direction from one or more TRPs to UE.

[0030] This disclosure can also be specified as, in another aspect, a method by which a computer performs the processing of the information processing apparatus described above. The method includes the computer obtaining first information relating to the loss of a signal coordinately transmitted from one or more transmission / reception points (TRPs) to a user device (UE); receiving third information from a network showing a relationship between the loss tolerance and the resolution, wherein the narrower the loss tolerance, the higher the resolution of the information regarding the propagation characteristics between the one or more TRPs and the UE reported from the UE to the network; obtaining a first loss tolerance at the UE based on the first information and second information showing a relationship between the value of a factor affecting the loss of the signal and a first value relating to the loss tolerance depending on the value of the factor; and determining the resolution applicable to the UE based on the first tolerance and the third information.

[0031] Another embodiment of the method can also be defined as a program for causing a computer to execute, and a computer-readable, non-temporary storage medium on which the program is recorded.

[0032] Embodiments of this disclosure will be described below with reference to the drawings. The configurations of the following embodiments are illustrative, and this disclosure is not limited to the configurations of these embodiments.

[0033] <First Embodiment> Figure 1 is a diagram showing an example of the system configuration of the communication system 100 according to the first embodiment. The communication system 100 is a distributed MIMO system including user equipment (UE) 2, a control device 1, and a plurality of distributed base stations. The communication system 100 is a wireless communication system of mobile communication methods such as 5G, LTE (Long Term Evolution), and 6G or later. The control device 1 is a device on the core network to which the distributed base stations are connected. However, it can also be considered that the control device 1 is the core network itself, or a system included in the core network. The core network includes, for example, an optical fiber network. The control device 1 controls the distributed base stations and the UE 2.

[0034] The distributed base stations, together with other distributed base stations within the same communication area, provide a wireless access network to UE 2 located within that communication area. The three distributed base stations shown in Figure 1 are assumed to be located within the same communication area. Each distributed base station is connected to the control device 1, for example, via a wired network.

[0035] A distributed base station is equipped with an antenna capable of forming multiple beam patterns. The antenna used in a distributed base station is, for example, an adaptive array antenna. An adaptive array antenna is an array antenna in which multiple antenna elements are arranged. The adaptive array antenna can electrically change the beam pattern by adaptively controlling the weighting of each antenna element according to the radio wave propagation environment. A beam pattern can also be described as the directivity of the beam formed by the adaptive array antenna. The beam pattern of a distributed base station is controlled by a control device 1. A distributed base station may have one antenna or multiple antennas. The beam formed at a distributed base station is identified by an antenna port.

[0036] A base station comprises a Radio Unit (RU), a Distributed Unit (DU), and a Centralized Unit (CU). While distributed base stations may also include RUs and CUs, the minimum configuration requires a DU; therefore, a distributed base station will hereafter be simply referred to as a DU.

[0037] UE 2 is a terminal station such as a smartphone, tablet, wearable device, or in-vehicle data communication device. However, it is not limited to this, and UE 2 may be a stationary terminal device. Alternatively, a relay station that relays wireless communication between a distributed base station and a terminal station can be used as a mobile station instead of UE 2. Relay stations include, for example, small base stations, mobile base stations, in-vehicle devices, and smartphones. In the first embodiment, UE 2 is equipped with one antenna. However, it is not limited to this, and UE 2 may be equipped with multiple antennas.

[0038] In the example shown in Figure 1, the communication system 100 includes three DUs: DU#1, DU#2, and DU#3. Each of DU#1, DU#2, and DU#3 is connected to and controlled by the control device 1. The connection between the control device 1 and each DU is, for example, via a dedicated line or a backbone network. The control device 1 and the UE 2 communicate via a wireless communication control channel through either DU#1, DU#2, or DU#3.

[0039] DU#1, DU#2, and DU#3 perform coordinated transmission to UE 2. In the first embodiment, it is assumed that the three DUs, DU#1, DU#2, and DU#3, perform CJT to UE 2. However, the coordinated transmission performed by DU#1, DU#2, and DU#3 to UE 2 is not limited to CJT, but may be CoMP, CJT, or distributed MIMO. Each of DU#1, DU#2, and DU#3 has two antenna ports. An example of an antenna port provided on a DU is a TRP.

[0040] UE 2 receives signals transmitted from each DU's TRP using each beam pattern. The CJT aims for the signals transmitted from each DU's TRP using each beam pattern to reach UE 2 in phase. To achieve this, it is required that each TRP transmits a carrier wave with phase correction equal to the offset from the received signal from the reference TRP. The reference TRP is selected by the control device 1 from among multiple TRPs that perform coordinated transmission to UE 2.

[0041] The phase offset of the target signal is measured by UE 2 and reported to control device 1. In the first embodiment, control device 1 determines the resolution of the phase offset reported by UE 2 based on the acceptable range of signal loss in UE 2 according to the propagation environment and notifies UE 2 of this. UE 2 reports the phase offset with the resolution determined by control device 1. The phase offset is obtained for each subband of the signal from each TRP. If the resolution is high, the number of bits representing a single phase offset increases, and the data size of the phase offset for each subband of the signal from each TRP reported by UE 2 may increase. In the first embodiment, since the resolution of the phase offset is determined to a value according to the propagation environment, it is possible to suppress the increase in the data size of the phase offset reported by UE 2.

[0042] Figure 2 shows an example of a CJT sequence in the communication system 100 according to the first embodiment. In Figure 2, for simplicity, one DU is shown representing multiple DUs. The processing for multiple DUs is the same. Also, as a premise of Figure 2, it is assumed that the distributed stations that will perform coordinated transmission to UE 2 have already been selected by the control device 1.

[0043] In S111, the control device 1 sends an instruction to the UE 2 to transmit the uplink reference signal. Along with this instruction, information regarding the resources allocated for the uplink reference signal to the UE 2 is also transmitted. Information regarding the resources allocated for measuring the uplink reference signal is also transmitted to each DU. Note that the instruction to transmit the reference signal in S111 may be an instruction for a periodic transmission, or it may be an instruction for a non-periodic transmission for the purpose of determining the resolution MΦ.

[0044] In S112, UE 2 transmits an uplink reference signal. In S113, each DU reports to the control device 1 the measured propagation characteristics with UE 2, which were measured based on the uplink reference signal transmitted from UE 2. The measured propagation characteristics reported in S113 may include, for example, RSRP or RSSI. However, the measured values ​​reported by each DU in S113 are not limited to these.

[0045] Furthermore, if UE 2 has multiple antenna ports, S112 transmits an uplink reference signal from each antenna port provided on UE 2. In S113, each DU acquires measurement values ​​based on the uplink reference signal received at each antenna port provided on each DU, and reports the measurement values ​​of the propagation characteristics between each antenna port provided on UE 2 and each antenna port provided on each DU. However, for simplicity, below we will simply say that UE 2 transmits or receives a reference signal or a data signal, and that DU transmits or receives a reference signal or a data signal.

[0046] In S114, the control device 1 performs a process to determine the resolution MΦ of the phase offset. In the first embodiment, the resolution MΦ is determined based on the measured values ​​reported from each DU. Details of the resolution MΦ determination process will be described later.

[0047] In S115, the control device 1 transmits to the UE 2 information regarding the resources allocated to the downlink reference signal for phase offset measurement, and the resolution MΦ. It also transmits an instruction to each DU to transmit the downlink reference signal for phase offset measurement. Along with this instruction, information regarding the resources allocated to the downlink reference signal is also transmitted to each DU.

[0048] In S116, each DU transmits a downlink reference signal. In S117, UE 2 receives the downlink reference signals from each DU and measures the phase offset from the reference signal for each subband of the received signals from each DU. In S118, UE 2 reports the measured phase offset results for each antenna port of each DU to the control device 1.

[0049] In S119, the control device 1 calculates the phase correction value for each subband relative to the carrier wave of each antenna port of each DU from the measurement results of the phase offset for each antenna port of each DU received from the UE 2. The phase correction value for each subband is obtained, for example, as the value obtained by inverting the sign of the phase offset in that subband. However, this is not limited to this, and the method of determining the phase correction value is not limited to a specific method.

[0050] In S120, the control device 1 notifies each DU of the phase correction values ​​for each subband acquired for each antenna port. In S121, each DU performs phase correction of the carrier wave for each DU port by shifting the phase by the notified phase correction value in each subband of the carrier wave frequency.

[0051] In S122, the control device 1 sends data signals to be transmitted via CJT to each DU, and each DU transmits data using a phase-corrected carrier wave in each subband. In UE 2, the phase-corrected signals received from each DU are combined and reception processing is performed.

[0052] In the example shown in Figure 2, the control device 1 notifies each DU of the phase correction value, and each DU performs the phase correction. However, this is not limited to this, and depending on the performance of the DU, the control device 1 may perform the phase correction of the carrier wave based on the phase correction value, notify the DU of information about the phase-corrected carrier wave, and the DU may transmit the data signal with the phase-corrected carrier wave according to that information.

[0053] Figure 3 illustrates the hardware configuration of the control device 1. The control device 1 includes a CPU 101, a main memory 102, an external memory 103, and a communication device 104. The CPU 101 is also called a processor. The CPU 101 is not limited to a single processor and may be a multi-processor configuration. In addition to the CPU 101, a Graphics Processing Unit (GPU), Digital Signal Processor (DSP), etc., may also be provided. Furthermore, the CPU 101 may be linked with hardware circuits such as a Field Programmable Gate Array (FPGA).

[0054] The CPU 101 executes a computer program that has been loaded into the main memory 102 in an executable format, and provides processing to the control device 1. The main memory 102 stores the computer program executed by the CPU 101, data processed by the CPU 101, etc. The main memory 102 is a Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), Read Only Memory (ROM), etc. Furthermore, the external storage device 103 is used as a storage area that assists the main memory 102, and stores the computer program executed by the CPU 101, data processed by the CPU 101, etc. The external storage device 103 is a hard disk drive, Solid State Drive (SSD), etc. Furthermore, a drive device for a removable storage medium may be connected to the control device 1. Removable storage mediums are, for example, Blu-ray discs, Digital Versatile Discs (DVDs), Compact Discs (CDs), flash memory cards, etc. The CPU 101 is an example of a "control unit" of an "information processing device".

[0055] The communication device 104 communicates with external networks such as distributed base stations and the Internet, for example, via optical fiber. The communication device 104 of the control device 1 may be a single device or a combination of multiple devices. The control device 1 is an example of an "information processing device". Note that the hardware configuration of the control device 1 is not limited to that shown in Figure 3.

[0056] Figure 4 shows an example of the functional configuration of the control device 1. The control device 1 comprises a control unit 11, an MCS index table 12, and loss margin-resolution correspondence information 13. The function of the control unit 11 is achieved by the CPU 101 executing a predetermined program.

[0057] In the first embodiment, the control unit 11 controls the CJT. More specifically, the control unit 11 selects distributed stations to perform coordinated transmission to the UE 2, allocates radio resources for reference signals for phase offset measurement, calculates phase correction values, and notifies the DU and UE 2 of control information and data signals.

[0058] In the resolution MΦ determination process, in the first embodiment, the control unit 11 determines the signal loss in the UE based on the measured values ​​reported from each DU, determines the signal loss margin recognized in the current propagation environment from that loss, and determines the resolution MΦ corresponding to that margin. Details of the resolution MΦ determination process will be described later. The control unit 11 notifies the UE 2 of the determined resolution MΦ.

[0059] The MCS index table 12 and the loss margin-resolution correspondence information 13 are stored in the external storage device of the control device 1. The MCS index table 12 and the loss margin-resolution correspondence information 13 are information used in the resolution MΦ determination process. Details of each will be described later.

[0060] Figure 5 shows an example of an MCS index table 12. The MCS index is an indicator that shows the combination of modulation and coding. The MCS index table shown in Figure 5 is based on the MCS index table shown in Table 5.1.3.1-1 in the 3GPP standard technical specification TS38.214.

[0061] The MCS index table 12 shown in Figure 5 contains MCS index I ＭＣＳ The modulation order, target coding rate, spectrum efficiency, and desired signal-to-noise power ratio are associated and included. The value of the modulation order corresponds to the modulation scheme. The MCS index contains the desired signal-to-noise power ratio Γ(I) when communication is performed using the modulation scheme and coding rate indicated by the MCS index. ＭＣＳ The desired signal-to-noise power ratio Γ(I) is associated with it. ＭＣＳThe value Γ(I) indicates the minimum signal-to-noise power ratio required for stable communication when communication is performed using the modulation scheme and coding rate indicated by the MCS index. ＭＣＳ ) is a theoretical value. In the MCS index table 12 shown in Figure 5, the desired signal-to-noise power ratio Γ(I ＭＣＳ The unit of ) is dB. Since the signal-to-noise power ratio indicates the quality of communication, in the first embodiment, the signal-to-noise power ratio is used as one of the indicators showing the magnitude of signal loss. Therefore, a smaller value of the signal-to-noise power ratio indicates greater loss.

[0062] The MCS index table 12 is used to determine a reference value when calculating the loss margin in the resolution MΦ determination process. The loss margin is also called the allowable range of loss. In the first embodiment, the loss margin is expressed using the signal-to-noise power ratio margin.

[0063] Figure 6 is a graph showing an example of loss margin-resolution correspondence information 13. In the first embodiment, the graph shown in Figure 6 is used as the loss margin-resolution correspondence information 13. In the graph shown in Figure 6, the horizontal axis represents the resolution MΦ, and the vertical axis represents the margin of the signal-to-noise power ratio. That is, the graph shown in Figure 6 shows the relationship between the resolution MΦ of the phase offset and the margin of signal loss for each number of distributed stations. Note that the values ​​in the graph shown in Figure 6 are 99th percentile values. The graph shown in Figure 6 may be obtained from a simulation, for example.

[0064] The loss margin-resolution correspondence information 13 is used in the resolution MΦ determination process to determine the resolution MΦ corresponding to the calculated loss margin. Note that the loss margin-resolution correspondence information 13 is not limited to the graph shown in Figure 6. For example, if the relationship between resolution and margin is expressed by a mathematical formula such as a function, the loss margin-resolution correspondence information 13 may be that function.

[0065] FIG. 7 is an example of a flowchart of the resolution MΦ determination process according to the first embodiment. The process shown in FIG. 7 is started, for example, when the start condition of CJT is satisfied. The start condition of CJT is, for example, that the deterioration of the communication quality of UE 2 is detected, that it is detected that UE 2 has moved to a position with a poor radio wave environment such as the cell edge, etc. These are detected, for example, based on the information regarding the propagation characteristics periodically reported from UE 2. The execution entity of the process shown in FIG. 7 is the CPU 101 of the control device 1, but for convenience, the functional components will be mainly described. The same applies to the following flowcharts. Also, in FIG. 7, for simplicity of explanation, it is assumed that both the DU and the UE have one antenna port each.

[0066] In OP101, the control unit 11 calculates the received signal power P between the UE and DU#n. ｎ [dB] to the received signal power P when ideal coherent combining is performed in UE 2. ＣＪＴ ＮＤＵ n is a variable for identifying the DU and takes values in the range from 1 to N. ＤＵ N ＤＵ indicates the number of DUs. The received signal power P ｎ is the measured value measured from the most recent reference signal reported from each DU in the first embodiment. The received signal power P ＣＪＴ ＮＤＵ is calculated by the following formula 1. δ in formula 1 ｎ indicates the difference between the transmission power of the reference signal and the transmission power of the data signal at the time of CJT in DU#n.

[0067] In OP102, the control unit 11 calculates the signal-to-noise power ratio Γ of the signal at the time of CJT in UE 2. ＣＪＴ ＮＤＵ The signal-to-noise power ratio Γ ＣＪＴ ＮＤＵ includes the difference between the received signal power obtained when ideal coherent combining is performed by CJT and the actually obtained received signal power. In the first embodiment, the signal-to-noise power ratio Γ ＣＪＴ ＮＤＵThis can be calculated as the SNR value using the following equation 2. Therefore, the signal-to-noise power ratio Γ ＣＪＴ ＮＤＵ The unit is dB. ＵＥ Ｎ This is the noise level at UE 2. ＵＥ Ｎ This may be, for example, measured and reported by UE 2 based on the downlink reference signal before the resolution MΦ determination process, or it may be a required specification value for UE 2.

[0068] In OP103, the control unit 11 retrieves the signal-to-noise power ratio Γ of the signal at CJT in UE 2 from the MCS index table 12. ＣＪＴ ＮＤＵ [dB] or less of the desired signal-to-noise power ratio Γ(I ＭＣＳ ) [dB], that is, the signal-to-noise power ratio Γ at CJT. ＣＪＴ ＮＤＵ The desired signal-to-noise power ratio Γ(I) shows a loss greater than the loss shown by ＭＣＳ The set of MCS indices I that are associated with ) ＭＣＳ Select this option.

[0069] In OP104, the control unit 11 controls the set of MCS indices I selected in OP103. ＭＣＳ From among these, select the desired signal-to-noise power ratio Γ(I ＭＣＳ The MCS index associated with the maximum value of ) is I^ ＭＣＳ Select as: MCS Index I^ ＭＣＳ This corresponds to the desired signal-to-noise power ratio Γ(I ＭＣＳ The value of ) is the maximum, but the set I of the MCS index ＭＣＳ Among these, the MCS index is shown to minimize losses.

[0070] In OP105, the control unit 11 calculates the loss margin Δ Ｍ The signal-to-noise power ratio Γ of the signal during CJT in UE 2 ＣＪＴ ＮＤＵ From the desired signal-to-noise power ratio Γ(I^ ＭＣＳSubtracting this, the loss margin Δ is obtained from the loss margin - resolution correspondence information 13. Ｍ The maximum MΦ value within the following region is determined as the resolution MΦ of the phase offset of UE 2. For example, if the graph shown in Figure 6 is used as the loss margin-resolution correspondence information 13, the number of DUs is 2, and the loss margin Δ Ｍ If the value is -4, then MΦ is determined to be 4. However, the method for determining the resolution MΦ from the loss margin-resolution correspondence information 13 is not limited to this. After that, the resolution MΦ determination process shown in Figure 7 is completed, and the resolution MΦ of the phase offset is notified to UE 2.

[0071] Note that the resolution MΦ determination process is not limited to the process shown in Figure 7. For example, in OP102, the signal-to-noise power ratio Γ at CJT is ＣＪＴ ＮＤＵ This can be determined using indicators other than SNR. For example, in OP104, I^ ＭＣＳ The MCS index selected is the set of MCS indexes I ＭＣＳ Any of the MCS indices included in it may be used.

[0072] In the example shown in Figure 7, it was explained assuming that each DU and UE 2 is equipped with one antenna port. When both the DU and UE are equipped with multiple antenna ports, the received signal power P in OP101 is... ＣＪＴ ＮＤＵ In the calculation, the received signal power P is calculated for all combinations of antenna port #m provided on UE 2 and antenna ports #n-kn on the DU side. ｍ ｎ，ｋｎ The calculation is performed according to Equation 1. m is a variable that indicates the antenna ports provided on UE 2, and takes values ​​in the range from 1 to M. M is the number of antenna ports provided on UE 2. kn is a variable that indicates the antenna ports provided on DU#n, and takes values ​​in the range from 1 to Kn. Kn is the number of antenna ports provided on DU#n.

[0073] <Effects of the First Embodiment> In the first embodiment, the resolution MΦ of the phase offset reported from UE 2 is equal to the loss margin Δ obtained based on the measured value. Ｍ This is determined based on the following. This allows for a resolution MΦ that is appropriate for the current propagation environment between UE 2 and each DU, and reduces overhead when reporting from UE 2.

[0074] <Modification 1 of the First Embodiment> In the first embodiment, the resolution MΦ is determined using measured values ​​based on the reference signal of the uplink from UE 2. Alternatively, measured values ​​measured by UE 2 based on the reference signal of the downlink from each DU may be used.

[0075] Figure 8 shows an example of the CJT sequence in the communication system 100 according to Modification 1 of the First Embodiment. The assumptions for the example shown in Figure 8 are the same as those for the example shown in Figure 2. In S211, the control device 1 transmits a transmission instruction for the downlink reference signal to each DU. Along with this instruction, information regarding the resources allocated for the downlink reference signal to each DU is also transmitted. Information regarding the resources allocated for measuring the downlink reference signal is also transmitted to the UE 2. Note that in S211, if it is the transmission timing for the SSS, the SSS may be used instead of the downlink reference signal.

[0076] In S212, each DU transmits a downlink reference signal. In S213, UE 2 generates an indicator showing the propagation characteristics with each DU, measured based on the downlink reference signals transmitted from each DU. The indicator may be, for example, RSRP, RSSI, CQI, or / or SNR. However, the indicator is not limited to these.

[0077] In S214, UE 2 reports the indicator to the control device 1. In S215, the control device 1 uses the indicator reported by UE 2 to perform a resolution MΦ determination process. Specifically, in a modified version of the first embodiment, for example, in OP101 of Figure 7, the received signal power P when ideal coherent synthesis is performed. ＣＪＴ ＮＤＵThe calculation involves the received signal power P between UE 2 and DU#n, which is included in the indicator reported by UE 2. ｎ This is used.

[0078] Thereafter, in the same manner as in the first embodiment, the resolution MΦ is notified to UE 2 (S216), the phase offset is measured by UE 2 based on the downlink reference signal (S217, S218), the phase offset is reported to the control device 1 (S219), and phase offset correction is performed. The resolution of the phase offset reported in S219 is MΦ.

[0079] In the first embodiment, modification 1, the resolution MΦ is determined using an indicator measured by UE, so the resolution MΦ can be determined based on a value that more accurately reflects the actual propagation environment.

[0080] <Modification 2 of the First Embodiment> In the resolution MΦ determination process of the first embodiment, the signal-to-noise power ratio Γ at CJT in UE 2 ＣＪＴ ＮＤＵ [dB] or less of the desired signal-to-noise power ratio Γ(I ＭＣＳ ) A set of MCS indices I that are associated with [dB] ＭＣＳ The following is selected. In the modified example 2 of the first embodiment, the set I of the MCS index is selected. ＭＣＳ You may use this to update the currently applied MCS index.

[0081] Figure 9 is an example of a flowchart of the MCS index update process according to Modification 2 of the First Embodiment. The process shown in Figure 9 is started, for example, when the resolution MΦ determination process shown in Figure 7 is completed.

[0082] In OP121, the control unit 11 determines that the MCS index currently applied to UE 2 and each DU is set to set I ＭＣＳ Determine whether or not it is included in set I. ＭＣＳ If it is included in (OP121: YES), the process shown in Figure 9 is terminated. The currently applied MCS index is set I ＭＣＳIf it is not included (OP122: NO), the process proceeds to OP122.

[0083] In OP122, the control unit 11 is set up I ＭＣＳ Among the MCS indices included, the signal-to-noise power ratio Γ(I ＭＣＳ The MCS index I^ is associated with the maximum value of ) ＭＣＳ The MCS index to be newly applied to UE 2 and each DU is determined. After that, the process shown in Figure 9 is completed. Then the control unit 11 updates the MCS index and the newly applied MCS index I^ for each DU and UE 2. ＭＣＳ To notify them of this.

[0084] Note that the process shown in Figure 9 is just one example, and the MCS index update process is not limited to the process shown in Figure 9. For example, in OP122, the newly applied MCS index is set I ＭＣＳ The MCS index included may be randomly selected.

[0085] In the resolution MΦ determination process of the first embodiment, the signal-to-noise power ratio Γ at CJT in UE 2 ＣＪＴ ＮＤＵ [dB] or less of the desired signal-to-noise power ratio Γ(I ＭＣＳ ) A set of MCS indices I that are associated with [dB] ＭＣＳ This is an MCS index that can satisfy the signal-to-noise power ratio required for stable communication in the current propagation environment between UE 2 and each DU. The set of MCS indices I ＭＣＳ By updating the MCS index included in the system, it becomes possible to ensure a signal-to-noise power ratio that satisfies the desired signal-to-noise power ratio associated with the updated MCS index, thereby stabilizing communication.

[0086] <Second Embodiment> In the second embodiment, the loss margin used to determine the resolution MΦ of the phase offset is determined based on the application's required rate. In the second embodiment, explanations common to the first embodiment are omitted. The hardware configuration (Figure 3) and functional configuration (Figure 4) of the control device 1 in the second embodiment, and the CJT sequence (see Figure 2) are the same as in the first embodiment.

[0087] Figure 10 is an example of a flowchart for determining the resolution MΦ according to the second embodiment. The process shown in Figure 10 is started, for example, when the CJT start condition is met. Also, for the sake of simplicity of explanation, Figure 10 assumes that both DU and UE are equipped with one antenna port each.

[0088] In OP201, the control unit 11 determines the spectral efficiency S according to the request rate from the application of the communication being performed by UE 2. ＲＥＱ Calculate the desired spectral efficiency S of the application. ＲＥＱ This is calculated using the following equation 3. R ＲＥＱ This is the application's request rate. ＲＢ This is the number of resource blocks available in the channel. ｆ This is the subcarrier interval of the channel in question. ｆ This represents the number of subcarriers.

[0089] In OP202, the control unit 11 obtains the desired spectral efficiency S of the application from the MCS index table 12. ＲＥＱ The above is a set of MCS indices I ＲＥＱ Obtain it.

[0090] In OP203, the control unit 11 receives the received signal power P between UE and DU#n. ｎ [dB] represents the received signal power P when ideal coherent synthesis is performed in UE 2. ＣＪＴ ＮＤＵ The received signal power P is calculated as follows. ｎ In the second embodiment, this is a measured value measured from the most recent reference signal reported by each DU. Received signal power P ＣＪＴＮＤＵ is calculated by the above formula (1). In OP204, the control unit 11 calculates the signal-to-noise power ratio Γ during CJT in UE 2 ＣＪＴ ＮＤＵ as shown in the above formula (2), subtracting the noise level P in UE 2 from the received signal power P calculated in OP203 ＣＪＴ ＮＤＵ from. ＵＥ Ｎ is calculated by subtracting.

[0091] In OP205, the control unit 11 selects, as I^, the MCS index associated with the minimum value of the desired signal-to-noise power ratio Γ(I) from the set I of MCS indexes selected in OP202. However, it is not limited to this, and I^ ＲＥＱ may be randomly selected from the MCS indexes included in the set I, or the MCS index associated with the median value of the desired signal-to-noise power ratio Γ(I) in the MCS indexes included in the set I ＲＥＱ may be selected. ＲＥＱ However, it is not limited to this. ＲＥＱ is the set I ＲＥＱ may be randomly selected from the MCS indexes included in, or the MCS index associated with the median value of the desired signal-to-noise power ratio Γ(I) in the MCS indexes included in the set I ＲＥＱ is selected. ＲＥＱ ).

[0092] In OP206, the control unit 11 obtains the loss margin Δ by subtracting the desired signal-to-noise power ratio Γ(I^) from the signal-to-noise power ratio Γ during CJT in UE 2, and determines the maximum value of MΦ within the region where the loss margin is less than or equal to Δ as the resolution MΦ of the phase offset of UE 2 from the loss margin-resolution correspondence information 13. After that, the determination process of the resolution MΦ shown in FIG. 10 ends, and the resolution MΦ of the phase offset is notified to UE 2. Ｍ＿ＲＥＱ is the signal-to-noise power ratio Γ during CJT in UE 2 ＣＪＴ ＮＤＵ [[ID=3F]]from the desired signal-to-noise power ratio Γ(I^) ＲＥＱ ), and determines the maximum value of MΦ within the region where the loss margin is less than or equal to Δ as the resolution MΦ of the phase offset of UE 2 from the loss margin-resolution correspondence information 13. After that, the determination process of the resolution MΦ shown in FIG. 10 ends, and the resolution MΦ of the phase offset is notified to UE 2. Ｍ＿ＲＥＱ ).

[0093] [[ID=4E]] When both the DU and the UE have a plurality of antenna ports, in the calculation of the received signal power P in OP203, similar to the first embodiment, for all combinations of the antenna ports provided in UE 2 and the antenna ports on the DU side, the received signal power P ＣＪＴ ＮＤＵ is calculated. ｍｎ，ｋｎ The calculation is performed according to Equation 1.

[0094] Furthermore, following the resolution MΦ determination process shown in Figure 10, set I ＲＥＱ Regarding this, the MCS index update process shown in Figure 9 may be performed. Set I ＲＥＱ When the MCS index update process shown in Figure 9 is performed, in OP122, the newly applied MCS index is set I. ＲＥＱ Among the MCS indices included, the desired signal-to-noise power ratio Γ(I ＲＥＱ The MCS index I^ is associated with the minimum value of ) ＲＥＱ This may be determined as the new MCS index to be applied to UE 2 and each DU. However, it is not limited to this.

[0095] <Effects of the Second Embodiment> In the second embodiment, the resolution MΦ of the phase offset reported from UE 2 is obtained based on the loss margin Δ obtained based on the application's required rate. Ｍ＿ＲＥＱ It is determined based on this. This allows the resolution MΦ to be set according to the MCS index such that the application's required rate is achieved. If the application's required rate is high, I^ ＲＥＱ The MCS index selected and the value indicating the desired signal-to-noise power ratio corresponding to that MCS index also increase, and the loss margin Δ Ｍ＿ＲＥＱ This also increases the resolution MΦ of the phase offset reported by the UE (Figure 6), allowing for finer adjustment of the signal phase error and maintaining communication quality. When the application's required rate is low, I^ ＲＥＱ The MCS index selected and the value indicating the desired signal-to-noise power ratio corresponding to that MCS index also become smaller, and the loss margin Δ Ｍ＿ＲＥＱ This also reduces the size. As a result, the resolution MΦ of the phase offset reported by the UE (Figure 6) can be set smaller, and the data size of the phase offset reported by UE 2 can also be kept small.

[0096] <Modification 1 of the Second Embodiment> In Modification 1 of the Second Embodiment, the loss margin used to determine the resolution MΦ of the phase offset is determined by considering not only the application's required rate but also the measured values ​​of the propagation characteristics between UE 2 and each DU.

[0097] Figure 11 is an example of a flowchart for determining the resolution MΦ according to Modification 1 of the second embodiment. The starting conditions and premises for the process shown in Figure 11 are the same as those in Figure 10. The processing from OP221 to OP224 is the same as the processing from OP201 to OP204 in Figure 10. The processing from OP221 to OP224 determines the spectral efficiency S according to the request rate from the application. ＲＥＱ The desired spectral efficiency S of the application is calculated (OP221). ＲＥＱ The above is a set of MCS indices I ＲＥＱ The received signal power P is obtained (OP222) when ideal coherent synthesis is performed. ＣＪＴ ＮＤＵ The following is calculated (OP223): the signal-to-noise power ratio Γ during CJT. ＣＪＴ ＮＤＵ This is calculated (OP224).

[0098] In OP225, the control unit 11 retrieves the signal-to-noise power ratio Γ at CJT in UE2 from the MCS index table 12. ＣＪＴ ＮＤＵ [dB] or less of the desired signal-to-noise power ratio Γ(I ＭＣＳ ) [dB] corresponds to the signal-to-noise power ratio Γ at CJT. ＣＪＴ ＮＤＵ The desired signal-to-noise power ratio Γ(I) shows a loss greater than the loss shown by ＭＣＳ The set of MCS indices I that are associated with ) ＭＣＳ Select this option.

[0099] In OP226, the control unit 11 is set up I ＲＥＱ and set I ＭＣＳ Determine whether there are any overlapping MCS indices in set I. ＲＥＱ and set I ＭＣＳIf there are overlapping MCS indices (OP226: YES), the process proceeds to OP227. In OP227, the control unit 11 processes set I ＭＣＳ Of these, set I ＲＥＱ From among the MCS indices that overlap, select the desired signal-to-noise power ratio Γ(I ＭＣＳ The MCS index associated with the maximum value of ) is I^ ＭＣＳ Select it as such.

[0100] In OP228, the control unit 11 controls the loss margin Δ Ｍ The signal-to-noise power ratio Γ of the signal during CJT in UE 2 ＣＪＴ ＮＤＵ From the desired signal-to-noise power ratio Γ(I^ ＭＣＳ Subtracting this, the loss margin Δ is obtained from the loss margin - resolution correspondence information 13. Ｍ The maximum MΦ value within the following region is determined as the resolution MΦ of the phase offset of UE 2. After that, the resolution MΦ determination process shown in Figure 11 is completed, and the resolution MΦ of the phase offset is notified to UE 2.

[0101] In OP226, set I ＲＥＱ and set I ＭＣＳ If there are no overlapping MCS indices (OP226: NO), the process proceeds to OP229. In OP229, the control unit 11 sends an instruction to the application to reduce the request rate. This instruction is sent, for example, to a server that controls the application. After that, the process shown in Figure 11 is completed. Note that following the resolution MΦ determination process shown in Figure 11, the MCS index update process shown in Figure 9 may be performed.

[0102] In the modified version 1 of the second embodiment, the loss margin is determined by considering not only the application's required rate but also the measured propagation characteristics between UE 2 and each DU. This allows the resolution MΦ to be set to a value that does not affect the achievement of a transmission speed that satisfies the application's required rate and maintains the stability of the current propagation environment.

[0103] Furthermore, in the modified example 1 of the second embodiment, set I ＲＥＱ and set I ＭＣＳIf there are no overlapping MCS indices, it indicates that the application's request rate is too high for the current propagation environment. If the application's request rate is too high, it can lead to a decrease in communication speed, packet loss, errors, and a decline in communication quality. According to Modification 1 of the Second Embodiment, if it is detected that the application's request rate is too high, an instruction is given to the application to reduce its request rate, thereby guiding the application's request rate to an appropriate rate for the current propagation environment.

[0104] Also, for example, set I ＲＥＱ and set I ＭＣＳ If there are no overlapping MCS indices, the control device 1 will set up set I ＭＣＳ The desired signal-to-noise power ratio Γ(I^) is the maximum value in this case. ＭＣＳ Based on this, the reduction in the request rate or the reduced request rate may be calculated and notified to the application along with an instruction to reduce the request rate.

[0105] <Modification 2 of the Second Embodiment> In the second embodiment, the resolution MΦ determination process (Figure 10) is performed using the measured values ​​of the propagation characteristics between UE 2 and each DU, acquired by each DU based on the uplink reference signal, in the CJT sequence shown in Figure 2. In Modification 2 of the second embodiment, instead, the resolution MΦ determination process (Figure 10) is performed using the measured values ​​(indicators) of the propagation characteristics between UE 2 and each DU, acquired by UE 2 based on the downlink reference signal, in the CJT sequence shown in Figure 8. Alternatively, in the CJT sequence shown in Figure 8, the resolution MΦ determination process in Modification 2 of the second embodiment shown in Figure 11 may be performed instead of the resolution MΦ determination process shown in Figure 10.

[0106] <Third Embodiment> In the third embodiment, UE 2 performs the resolution MΦ determination process (Figure 7) which is performed by the control device 1 in the first embodiment. In the third embodiment, explanations common to the first embodiment are omitted.

[0107] Figure 12 shows an example of the CJT sequence in the communication system 100 according to the third embodiment. The assumptions for the example shown in Figure 12 are the same as those for the example shown in Figure 2. In S311, the control device 1 sends a transmission instruction for the downlink reference signal to each DU. Along with this instruction, information regarding the resources allocated for the downlink reference signal to each DU is also transmitted. Information regarding the resources allocated for measuring the downlink reference signal is also transmitted to the UE 2. Furthermore, in the third embodiment, the control device 1 notifies the UE 2 of the loss margin-resolution correspondence information 13 as a calculation condition for the resolution MΦ. Note that in S311, if it is the transmission timing for the SSS, the SSS may be used instead of the downlink reference signal. The control device 1 notifies the UE 2 of the calculation condition for the resolution MΦ, for example, when the CJT start condition is met.

[0108] In S312, each DU transmits a downlink reference signal. In S313, UE 2 measures the propagation characteristics with each DU based on the downlink reference signals transmitted from each DU, and uses the measured value and the loss margin-resolution correspondence information 13 received from the control device 1 to perform a resolution MΦ determination process similar to the process shown in Figure 7. In S314, UE 2 reports to the control device 1 the phase offset MΦ obtained as a result of the resolution MΦ determination process performed in S313.

[0109] Thereafter, in the same manner as the CJT sequence of the first embodiment (Figure 2), each DU transmits a downlink reference signal according to instructions from the control device 1 (S315, 316), the UE 2 measures the downlink reference signal and measures the phase offset (S317), the phase offset is reported to the control device 1 (S318), and phase offset correction is performed.

[0110] Figure 13 shows an example of the hardware configuration of UE 2. UE 2 includes a CPU 201, main memory 202, external storage device 203, wireless communication device 204, and antenna 205. The CPU 201, main memory 202, and external storage device 203 are the same as those of CPU 101, main memory 102, and external storage device 103.

[0111] The wireless communication device 204 is connected to the antenna 205 and, through the antenna 205, connects to a wireless access network, for example, by a 5G or later mobile wireless communication system, and receives wireless signals from distributed base stations. The wireless communication device 204 is also connected to the control device 1 on the control plane. Note that the hardware configuration of UE 2 is not limited to that shown in Figure 13. Depending on the type, UE 2 may further include a touch panel display, microphone, speaker, and operation buttons in addition to the components shown in Figure 12.

[0112] Figure 14 shows an example of the functional configuration of UE 2. UE 2 comprises a control unit 21, a measurement unit 22, and an MCS index table 23. The functions of the control unit 21 and the measurement unit 22 are achieved by the CPU 201 executing a predetermined program.

[0113] The control unit 21 controls the measurement and reporting of periodic or aperiodic radio wave propagation characteristics in UE 2. The control unit 21 receives the allocation of radio resources for measuring radio wave propagation characteristics and the allocation of radio resources for reporting from the control device 1. The control unit 21 outputs the allocation of radio resources for measuring radio wave propagation characteristics to the measurement unit 22. The control unit 21 receives the measurement results of the radio wave propagation characteristics of the downlink reference signal (e.g., CSI-RS) transmitted from each DU from the measurement unit 22. The control unit 21 uses the reporting radio resources notified by the control device 1 to report information regarding radio wave propagation characteristics as measurement results to the control device 1.

[0114] In the third embodiment, the control unit 21 performs a resolution MΦ determination process using the measured values ​​of the propagation characteristics between each DU, measured based on the downlink reference signal transmitted from each DU, and the loss margin-resolution correspondence information 13 received from the control device 1 as a calculation condition for the resolution MΦ. The resolution MΦ determination process performed by the control unit 21 is the same as the process shown in Figure 7, except that it uses the measured values ​​of the propagation characteristics between each DU, measured based on the downlink reference signal transmitted from each DU, and the loss margin-resolution correspondence information 13 received from the control device 1 as a calculation condition.

[0115] The measurement unit 22 receives input from the control unit 21 regarding information about the distributed stations to be measured and the allocation of radio resources for measuring radio wave propagation characteristics, which are notified by the control device 1. The measurement unit 22 receives the downlink reference signal transmitted from each DU via the UE port according to the allocation of radio resources for measuring radio wave propagation characteristics. Each time the measurement unit 22 receives a downlink reference signal, it estimates the radio wave propagation characteristics of the downlink reference signal from each DU port and outputs the measurement result to the control unit 21 as one of the measurement results. The radio wave propagation characteristics of the downlink reference signal measured by the measurement unit 22 include, for example, propagation characteristics (channel response), phase offset, RSRP, RSSI, RSRQ, CSI, and SINR.

[0116] The MCS index table 23 is, for example, the MCS index table shown in Figure 5. Since the UE 2 also maintains a common MCS index table with the control device 1 and each DU, the applicable modulation scheme and coding rate can be identified by notifying only the MCS index. Note that the functional configuration of the UE 2 is not limited to the example shown in Figure 14.

[0117] <Effects of the Third Embodiment> In the third embodiment, UE 2 performs the resolution MΦ determination process. In this case, in the sequence related to the resolution MΦ determination process (for example, S311 to S314 in Figure 12), UE 2 transmits only when notifying the control device 1 of the determined resolution MΦ. Normally, transmitting a signal consumes more power than receiving a signal. Therefore, when UE 2 performs the resolution MΦ determination process as in the third embodiment, the power consumption of UE 2 can be kept low. In addition, by reducing the transmission of signals from UE 2, the amount of wireless resources allocated to data communication can be increased.

[0118] Furthermore, when UE 2 performs the resolution MΦ determination process, UE 2 may, for example, perform the MCS index update process shown in Figure 9. In this case, after the MCS index update process, UE 2 may notify the control device 1 of the MCS index that it has decided to apply.

[0119] <Fourth Embodiment> In the fourth embodiment, UE 2 determines the resolution MΦ in the same manner as in the second embodiment, which is performed by the control device 1. In the fourth embodiment, descriptions common to the first to third embodiments are omitted. In the fourth embodiment, the hardware configuration (Figure 13) and functional configuration (Figure 14) of UE 2, and the CJT sequence (Figure 12) are the same as in the third embodiment.

[0120] The difference between the resolution MΦ determination process performed by the control device 1 in the second embodiment (Figure 10) and the process in which the UE 2 determines the resolution MΦ in the fourth embodiment is that the UE 2 determines the resolution MΦ from a set of MCS indices I corresponding to the request rate from the application. ＲＥＱ The key difference is that the acquisition of this information (OP201-OP202 in Figure 10) is not performed. This is because information such as the request rate of the higher-layer application is basically handled on the network side and is therefore often notified to the control unit without being notified to UE 2.

[0121] In the fourth embodiment, the control device 1 controls a set of MCS indices I corresponding to the request rate from the application. ＲＥＱObtain set I ＲＥＱ The loss margin - resolution correspondence information 13 is sent to UE 2 as calculation conditions (S311 in Figure 12). UE 2 receives the set I from the control device 1. ＲＥＱ Using the loss margin-resolution correspondence information 13 and the measured value based on the downlink reference signal, for example, the processing from OP203 to OP206 in Figure 10 is performed. As a result, the resolution MΦ is also determined by UE 2 based on the application's requested rate. In addition, in UE 2, after determining the resolution MΦ, set I ＲＥＱ Regarding this, the MCS index update process shown in Figure 9 may be performed.

[0122] <Modification of the Fourth Embodiment> In the modification of the fourth embodiment, UE 2 determines the resolution MΦ in the same manner as performed by the control device 1 in Modification 1 of the second embodiment. The differences between the resolution MΦ determination process performed by the control device 1 in Modification 1 of the second embodiment (Figure 11) and the process in which UE 2 determines the resolution MΦ in the modification of the fourth embodiment are the same as in the fourth embodiment.

[0123] In a modified version of the fourth embodiment, the control device 1 controls a set of MCS indices I corresponding to the application's request rate. ＲＥＱ Obtain set I ＲＥＱ The loss margin - resolution correspondence information 13 is sent to UE 2 as calculation conditions (S311 in Figure 12). UE 2 receives the set I from the control device 1. ＲＥＱ Using the loss margin-resolution correspondence information 13 and the measured value based on the downlink reference signal, for example, the processing from OP223 to OP228 in Figure 11 is performed. In this way, UE 2 also determines the resolution MΦ by considering the measured value of the propagation characteristics between each DU in addition to the application's requested rate. Note that in UE 2 as well, the MCS index update processing shown in Figure 9 may be performed after the resolution MΦ has been determined.

[0124] Furthermore, in a modified example of the fourth embodiment, a set of MCS indices I corresponding to the application's request rate ＲＥＱ And the signal-to-noise power ratio Γ during CJT.ＣＪＴ ＮＤＵ The desired signal-to-noise ratio Γ(I) exhibits a loss greater than the loss shown by ＭＣＳ The set of MCS indices I that are associated with ) ＭＣＳ If there are no overlapping MCS indices (OP226: NO in Figure 11), UE 2 may send a suggestion to control unit 1 to reduce the application request rate.

[0125] <Other Embodiments> The embodiments described above are merely examples, and this disclosure may be modified as appropriate without departing from its essence.

[0126] The first to fourth embodiments described how to determine the resolution MΦ of the phase offset reported from the UE 2 to the control device 1. However, the process for determining the resolution MΦ described in the first to fourth embodiments is also applicable when reporting information on propagation characteristics other than phase offset, such as CSI, RSRP, RSRQ, and SINR. When applied to reporting information on propagation characteristics other than phase offset, loss margin-resolution correspondence information 13 measured for the information on such propagation characteristics may be used.

[0127] In the first to fourth embodiments, the propagation characteristics between UE 2 and each DU are measured using a reference signal, but are not limited to this, and signals other than the reference signal, such as data signals, may be used.

[0128] In the first to fourth embodiments, the explanation was based on the premise that CJT is performed in a distributed MIMO system. However, it is not limited to this, and the resolution MΦ determination process described in the first to fourth embodiments can also be applied to systems in which multiple base stations cooperate to increase the received signal power or received signal strength at the UE, such as CoMP, beamforming, and various MIMOs, and to systems in which multiple base stations cooperate to suppress the effects of interference at the UE, such as distributed null steering and interference null forming. In a broader sense, the resolution MΦ determination process described in the first to fourth embodiments can be applied to systems in which at least multiple antenna ports are provided on the base station side, and technologies are used to improve the communication quality of the UE through the interaction of signals transmitted from the multiple antenna ports to the UE. However, the method for determining the index indicating the magnitude of signal loss used in the resolution MΦ determination process may be appropriately changed depending on the system to which it is applied.

[0129] The processing of the control device 1 in the first or second embodiment, or the processing of the control device 1 in the third or fourth embodiment, may be performed by one of the relay stations if the signal to any of the base stations or UE 2 among the distributed stations is relayed by one or more relay stations.

[0130] Furthermore, the processes and means described in this disclosure can be freely combined and implemented, provided that no technical inconsistencies arise.

[0131] Furthermore, a process described as being performed by a single device may be divided and executed by multiple devices. Conversely, 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 implemented can be flexibly changed.

[0132] The present disclosure can also be realized by supplying a computer program implementing the functions described in the embodiments above 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 by a non-temporary computer-readable storage medium that can be connected to the computer's system bus, or it may be provided to the computer via a network. The non-temporary computer-readable storage medium includes any type of disk, such as magnetic disks (floppy disks, hard disk drives (HDDs), etc.), optical disks (CD-ROMs, DVDs, Blu-ray discs, etc.), read-only memory (ROM), random access memory (RAM), EPROM, EEPROM, magnetic cards, flash memory, or optical cards, and any type of medium suitable for storing electronic instructions.

[0133] 1. Control device 2. UE 11. Control unit 12. MCS index table 13. Loss margin - resolution correspondence information 23. MCS index table 100. Communication system 101. CPU 102. Main memory 103. External memory 104. Communication device

Claims

1. A UE comprising a control unit that performs: acquiring first information regarding the loss of a signal coordinately transmitted from one or more transmission / reception points (TRPs) to a user equipment (UE); receiving third information from a network indicating a relationship between the acceptable range of loss and the resolution, wherein the narrower the acceptable range of loss, the higher the resolution of the information regarding the propagation characteristics between the one or more TRPs and the UE reported from the UE to the network; acquiring a first acceptable range of signal loss in the UE based on the first information and second information indicating a relationship between the value of a factor affecting the signal loss and a first value regarding the loss that is allowed according to the value of the factor; and determining the resolution to be applied to the UE based on the first acceptable range and the third information.

2. The UE according to claim 1, further comprising: the control unit further obtaining a second value relating to the signal loss in the UE based on measured values ​​relating to the propagation environment between the one or more TRPs and the UE as first information; and obtaining a first tolerance range based on the first information and, as second information, the correspondence between the MCS index and the first value for one or more first MCS (Modulation and Coding Scheme) indices.

3. The UE according to claim 2, wherein the control unit obtains a value from among the one or more first values ​​corresponding to each of the one or more first MCS indices that indicates the smallest loss, and subtracts the value from among the one or more first values ​​that indicates the smallest loss from the second value to obtain the first tolerance range.

4. The UE according to claim 2, further comprising: the control unit acquiring one or more MCS indices, from among a plurality of correspondences between the MCS index and the first value, that are associated with a first value indicating a loss greater than the loss indicated by the second value, as the one or more first MCS indices.

5. The UE according to claim 2, further comprising: the control unit receiving from the network one or more MCS indices from among a plurality of associations between MCS index, spectral efficiency, and signal loss, which are associated with a spectral efficiency equal to or greater than the spectral efficiency corresponding to the application's required rate, as the one or more first MCS indices.

6. The UE according to claim 2, further comprising: the control unit receiving from the network, as the one or more first MCS indexes, one or more second MCS indices that are associated with a spectral efficiency greater than or equal to the spectral efficiency corresponding to the application's required rate, and which are associated with a first value that indicates a loss greater than the loss indicated by the second value.

7. The UE according to claim 6, wherein the control unit further proposes to the network a reduction in the request rate of the application if there is no MCS index among the one or more second MCS indices that is associated with a first value that indicates a loss greater than the loss indicated by the second value.

8. The UE according to claim 2, wherein the control unit further determines one of the one or more first MCS indexes as a new third MCS index if the one or more TRPs and the third MCS index used by the UE are not included in the one or more first MCS indexes.

9. The UE according to claim 8, wherein the control unit determines the MCS index among the one or more first MCS indices that has the smallest loss indicated by the associated first value as the new third MCS index.

10. The UE according to claim 2, further comprising the control unit acquiring the measured value based on the downlink measurement signals received from the one or more TRPs.

11. The UE according to claim 1, further comprising the control unit notifying the network of the resolution to be applied to the determined UE.

12. A method for a computer to perform the following: acquire first information relating to the loss of a signal coordinately transmitted from one or more transmission / reception points (TRPs) to a user device (UE); receive third information from a network indicating a relationship between the acceptable range of loss and the resolution, wherein the narrower the acceptable range of loss, the higher the resolution of the information regarding the propagation characteristics between the one or more TRPs and the UE reported from the UE to the network; acquire a first acceptable range of signal loss in the UE based on the first information and second information indicating a relationship between the value of a factor affecting the signal loss and a first value relating to the acceptable loss depending on the value of the factor; and determine the resolution to be applied to the UE based on the first acceptable range and the third information.

13. The method according to claim 12, wherein the computer further obtains, as first information, a second value relating to the signal loss in the UE based on measured values ​​relating to the propagation environment between the one or more TRPs and the UE, and obtains the first tolerance range based on the first information and, as second information, a correspondence between the MCS index and the first value for one or more first MCS (Modulation and Coding Scheme) indices.

14. The method according to claim 13, wherein the computer obtains a value from among the one or more first values ​​corresponding to each of the one or more first MCS indices that indicates the smallest loss, and obtains a first tolerance range by subtracting the value from the one or more first values ​​that indicates the smallest loss from the second value.

15. The method according to claim 13, further comprising the computer obtaining, as the one or more first MCS indexes, one or more MCS indexes among a plurality of correspondences between the MCS index and the first value that is associated with a first value that indicates a loss greater than the loss indicated by the second value.

16. The method according to claim 13, further comprising the computer receiving from the network one or more MCS indices from among a plurality of associations between MCS index, spectral efficiency, and signal loss, which are associated with a spectral efficiency equal to or greater than the spectral efficiency corresponding to the application's required rate, as the one or more first MCS indices.

17. The method according to claim 13, further comprising the computer receiving from the network, as the one or more first MCS indexes, one or more second MCS indices that, in a plurality of associations between MCS index, spectral efficiency and signal loss, are associated with a spectral efficiency equal to or greater than the spectral efficiency corresponding to the application's required rate, and which are associated with a first value that indicates a loss greater than the loss indicated by the second value.

18. The method of claim 17, further comprising the computer proposing to the network a reduction in the request rate of the application if there is no MCS index associated with a first value that indicates a loss greater than the loss indicated by the second value among the one or more second MCS indices.

19. The method according to claim 13, further comprising the computer acquiring the measured value based on the downlink measurement signals received from the one or more TRPs.

20. A program for causing a computer to perform the following: acquire first information regarding the loss of a signal transmitted in coordination from one or more transmission / reception points (TRPs) to a user device (UE); receive third information from a network showing a relationship between the acceptable range of loss and the resolution, wherein the narrower the acceptable range of loss, the higher the resolution of the information regarding the propagation characteristics between the one or more TRPs and the UE reported from the UE to the network; acquire a first acceptable range of signal loss in the UE based on the first information and second information showing a relationship between the value of a factor affecting the signal loss and a first value regarding the loss that is allowed depending on the value of the factor; and determine the resolution to be applied to the UE based on the first acceptable range and the third information.

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