Information processing device and method

Abstract

The present invention improves the efficiency with which information about radio wave propagation characteristics between antenna ports of a UE and antenna ports of base stations is reported to a network. According to the present invention, one or more base stations have a total of K first antenna ports. A UE has N second antenna ports and receives signals that have been simultaneously transmitted from the K first antenna ports on the base station side. The N second antenna ports of the UE are sorted into G second antenna port groups of two or more second antenna ports that have radio wave propagation characteristics that have a high correlation. Information about radio wave propagation characteristics is reported by the UE to a network for K×G one-to-one combinations of each of the K first antenna ports and each of G second antenna ports that are respective representatives of the G second antenna port groups.

Description

Information processing apparatus and method

[0001] This disclosure relates to wireless communication.

[0002] In wireless communication 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 the 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. In addition, with distributed MIMO, since the base stations are distributed, dead spots for radio waves can be reduced and the effects of obstacles can be mitigated.

[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 the received signal power when signals from each distributed station are combined is called Coherent Joint Transmission (CJT). This is achieved by ensuring that the transmitted signals from each distributed station are received in phase at the User Equipment (UE). For example, in coordinated transmission by N distributed stations, assuming that the transmitted power of each distributed station is equal, CJT theoretically makes the received signal power at the UE N squared times the received signal power of a single distributed station. By improving the received signal power through CJT, throughput is improved and latency is 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 the network.

[0005] When the UE has a plurality of antenna ports, the UE is required to report to the network the phase offset of the carrier wave from each antenna port provided in each distributed station for each antenna port. Therefore, the phase offset for the number obtained by multiplying the number of antenna ports of the UE by the total number of antenna ports provided in the distributed station is reported from the UE to the network. Therefore, as the number of antenna ports of the UE increases, the overhead of the network increases.

[0006] When the UE has a plurality of antenna ports, it is permitted to select one from the plurality of antenna ports and report the phase offset of the carrier wave from the plurality of antenna ports provided in each distributed station for the selected one antenna port (for example, Non-Patent Document 1). The antenna port for which the phase offset is reported representing the plurality of antenna ports provided in the UE is referred to as a reference UE antenna port.

[0007] Google, CSI Enhancement for NR MIMO, 3GPP TSG RAN WG1 #119, R1-2410154, November 18, 2024, pp.3

[0008] However, Non-Patent Document 1 does not disclose how to select the reference UE antenna port from among the plurality of antenna ports provided in the UE. One aspect of the present disclosure is to provide an information processing apparatus and a method capable of improving the efficiency of reporting information regarding radio wave propagation characteristics between the antenna ports provided in the UE and the antenna ports provided in the base station from the UE to the network.

[0009] One aspect of this disclosure is, for at least one of the following: one or more base stations having one or more antenna ports, or a user device (UE) that receives signals simultaneously transmitted from the one or more antenna ports of the one or more base stations through one or more antenna ports, classifying the one or more antenna ports into one or more antenna port groups by grouping two or more antenna ports whose correlation value for radio wave propagation characteristics is equal to or greater than a first value; and a combination of antenna ports between the one or more base stations and the UE for reporting information on radio wave propagation characteristics to the network, which is a combination of one or more representative ports selected one from each of the one or more antenna port groups for either the one or more base stations or the UE, and one or more antenna ports provided on the other of the one or more base stations or the UE, or This is an information processing device comprising a control unit that determines a combination of one or more representative ports selected one by one from each of the one or more antenna port groups for the one or more base stations and one or more representative ports selected one by one from each of the one or more antenna port groups for the UE, and performs the following:

[0010] Another aspect of the present disclosure is a UE having N second antenna ports that receive signals simultaneously transmitted from a total of K first antenna ports of one or more base stations, wherein the N second antenna ports are classified into G second antenna port groups, each containing one or more second antenna ports, by grouping two or more second antenna ports whose correlation value with respect to one of the K first antenna ports on the base station side is greater than or equal to a first value; and a control unit that performs the following: K is a positive integer of 1 or more, and N is a positive integer of 2 or more. G is an integer that takes values ​​in the range of 1 to N, and is an information processing device.

[0011] One aspect of the present disclosure is that, in a UE including N second antenna ports that receive signals simultaneously transmitted from a total of K first antenna ports of one or more base stations, the N second antenna ports are grouped into G second antenna port groups including one or more second antenna ports by grouping two or more second antenna ports for which a value indicating the height of the correlation of radio wave propagation characteristics with respect to one of the K first antenna ports on the base station side is equal to or greater than a first value, and for each of the K×G pairs of the first antenna ports on the base station side and the second antenna ports provided in the UE, which are one-to-one combinations of each of the K first antenna ports and each of the G second antenna ports respectively selected as representatives from each of the G second antenna port groups, determining that the UE reports information on the radio wave propagation characteristics to the network. K is a positive integer of 1 or more, N is a positive integer of 2 or more, and G is an integer taking a value in the range of 1 or more and N or less.

[0012] According to one aspect of the present disclosure, it is possible to provide an information processing apparatus, method, and program capable of improving the efficiency of reporting information on radio wave propagation characteristics from a UE including a plurality of antenna ports to a network.

[0013] Figure 1 is a diagram illustrating an example of the system configuration of a communication system. Figure 2A is a diagram illustrating step 1 of the reporting port selection process according to the first embodiment. Figure 2B is a diagram illustrating step 1 of the reporting port selection process according to the first embodiment. Figure 2C is a diagram illustrating step 1 of the reporting port selection process according to the first embodiment. Figure 3 is a diagram illustrating an example of the sequence in step 1 of the reporting port selection process. Figure 4 is a diagram illustrating an example of the hardware configuration of the control device. Figure 5 is a diagram illustrating an example of the functional configuration of the control device. Figure 6 is an example of the hardware configuration of the UE. Figure 7 is a diagram illustrating an example of the functional configuration of the UE. Figure 8 is an example of the flowchart of the control device processing related to step 1 of the reporting port selection process. Figure 9 is a diagram illustrating the processing of step 1A of the reporting port selection process according to a modified example of the first embodiment. Figure 10 is a diagram illustrating an example of the sequence in step 1A of the reporting port selection process. Figure 11 is an example of the flowchart of the control device processing related to step 1A of the reporting port selection process. Figure 12A is a diagram illustrating step 2 of the reporting port selection process according to the second embodiment. Figure 12B is a diagram illustrating step 2 of the reporting port selection process according to the second embodiment. Figure 13 is a diagram illustrating an example of the sequence in step 2 of the reporting port selection process. Figure 14 is an example of a flowchart of the control device processing related to step 2 of the reporting port selection process. Figure 15A is a diagram illustrating the processing of step 2A of the reporting port selection process according to a modified example of the second embodiment. Figure 15A is a diagram illustrating the processing of step 2A of the reporting port selection process according to a modified example of the second embodiment. Figure 16 is a diagram illustrating an example of the sequence in step 2A of the reporting port selection process. Figure 17 is an example of a flowchart of the control device processing related to step 2A of the reporting port selection process. Figure 18A is a diagram illustrating step 3 of the reporting port selection process according to the third embodiment. Figure 18B is a diagram illustrating step 3 of the reporting port selection process according to the third embodiment. Figure 19 is a diagram illustrating an example of the sequence in step 3 of the reporting port selection process.Figure 20 is an example of a flowchart of the UE processing related to step 3 of the port selection process for reporting. Figure 21 is a diagram showing the processing of step 3A of the port selection process for reporting according to modification 1 of the third embodiment. Figure 22 is a diagram showing an example of the sequence in step 3A of the port selection process for reporting. Figure 23 is an example of a flowchart of the UE processing related to step 3A of the port selection process for reporting.

[0014] In one aspect of this disclosure, when signals are simultaneously transmitted from multiple antenna ports of one or more base stations to a user equipment (UE) equipped with multiple antenna ports, two or more antenna ports with high correlation in radio wave propagation characteristics are grouped together from among the multiple antenna ports provided on the UE or base station side, and information regarding the radio wave propagation characteristics of the antenna port representing the group is reported to the network, thereby reducing the overhead of such reporting from the UE to the network.

[0015] More specifically, one aspect of the present disclosure is an information processing device comprising a control unit. The control unit classifies one or more antenna ports into one or more antenna port groups, which include one or more antenna ports, for at least one of the following: one or more base stations having one or more antenna ports, or a user device (UE) that receives signals simultaneously transmitted from one or more antenna ports of the one or more base stations through one or more antenna ports. The control unit also determines the combination of antenna ports between the one or more base stations and the UE for which the UE reports information regarding radio wave propagation characteristics to the network, to be one of the following combinations. One such combination is a combination of one or more representative ports selected one from each of the one or more antenna port groups for either the one or more base stations or the UE, and one or more antenna ports provided on the other of the one or more base stations or the UE. One such combination is a combination of one or more representative ports selected from each of the one or more antenna port groups for the one or more base stations, and one or more representative ports selected from each of the one or more antenna port groups for the UE.

[0016] More specifically, one aspect of the present disclosure is an information processing device comprising a control unit. The control unit performs the following actions in a UE having N second antenna ports that receive signals simultaneously transmitted from a total of K first antenna ports of one or more base stations: classifying the N second antenna ports into G second antenna port groups, each containing one or more second antenna ports, by grouping two or more second antenna ports whose correlation value with respect to one of the K first antenna ports on the base station side is equal to or greater than a first value; and deciding whether the UE should report information regarding radio wave propagation characteristics to the network for each of the K first antenna ports and each of the G second antenna ports selected as representatives from each of the G second antenna port groups, resulting in K × G one-to-one combinations of first antenna ports on the base station side and second antenna ports provided in the UE. K is a positive integer of 1 or more. N is a positive integer greater than or equal to 2. G is an integer that takes a value between 1 and N, inclusive.

[0017] The information processing device is, for example, a control device that controls a system including one or more base stations and the UE. However, it is not limited to this, and the information processing device may also be a UE, a base station, or a relay station. The control unit provided in the information processing device is, for example, a processor such as a CPU (Central Processing Unit). The UE is, for example, a wireless communication device such as a smartphone, a tablet terminal, and an in-vehicle device. However, it is not limited to this, and the UE may also be a stationary PC (Personal Computer) and a fixedly installed IoT device. Even when the information processing device is a UE, the control unit is a processor such as a CPU.

[0018] An antenna port is a logical interface in a wireless communication system. When multiple beams of multiple physical antennas or array antennas are used in a single device, the antenna port is an identifier used to logically distinguish the beams of the physical antennas or array antennas. For example, if a base station has an array antenna, the first antenna port provided on the base station corresponds to one or more of the beams formed by the array antenna. Since the array antenna is provided on the DU (Distributed Unit), which is a component of the base station, it can also be said that the first antenna port is provided on the DU. If a UE has multiple physical antennas such as monopole antennas or dipole antennas, the second antenna port provided on the UE corresponds to one physical antenna.

[0019] If a single base station has multiple antenna ports, signals are transmitted and received between the base station and the UE using MIMO. If there are multiple base stations, signals are transmitted in a coordinated manner from the multiple base stations to the UE through multiple antenna ports. Examples of coordinated transmission from multiple base stations to a UE include CJT, JT, CoMP (Coordinated Multi-Point), or distributed MIMO.

[0020] The information reported from the UE to the network regarding the radio wave propagation characteristics between the first antenna port on the base station side and the second antenna port provided on the UE 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.

[0021] Values ​​that indicate the degree of correlation between the radio wave propagation characteristics of two or more antenna ports include, for example, the correlation coefficient, correlation matrix, covariance, spectral correlation, correlation length between antenna ports, or diversity gain. Any one or a combination of these values ​​may be used to indicate the degree of correlation between the radio wave propagation characteristics of two or more antenna ports.

[0022] In one aspect of this disclosure, in a UE, two or more second antenna ports with high correlation of radio wave propagation characteristics are grouped together as a second antenna port group. Two or more antenna ports with high correlation of radio wave propagation characteristics can be considered to have the same radio wave propagation characteristics. Therefore, information regarding the radio wave propagation characteristics of a representative second antenna port can be shared, repurposed, or substituted among two or more second antenna ports included in the second antenna port group. Accordingly, according to one aspect of this disclosure, in a UE, antenna port groups can be formed based on the degree of correlation of radio wave propagation characteristics between antenna ports, and a representative antenna port (for example, a reference UE antenna port) can be selected for each antenna port group.

[0023] Furthermore, in one aspect of this disclosure, the N second antenna ports provided on the UE are classified into G second antenna port groups, and information regarding radio wave propagation characteristics is reported from the UE to the network for each combination of the G representative second antenna ports in each second antenna port group and each of the K first antenna ports on the base station side. As a result, the information regarding radio wave propagation characteristics between the first antenna ports on the base station side and the second antenna ports provided on the UE, reported from the UE to the network, is K × G. Normally, when coordinated transmission is performed to the UE from one or more base stations, each equipped with a total of K first antenna ports, the UE reports K × N information regarding radio wave propagation characteristics, which is the number of combinations between the first antenna ports on the base station side and the second antenna ports provided on the UE. Therefore, according to one aspect of this disclosure, the amount of information regarding radio wave propagation characteristics reported from the UE to the network can be reduced by K × (N - G) combinations compared to normal, thereby reducing overhead.

[0024] In one aspect of the present disclosure, the control unit may further classify the K first antenna ports on the base station side into T first antenna port groups, each containing one or more first antenna ports, by grouping two or more first antenna ports whose correlation value between the radio wave propagation characteristics and one of the N second antenna ports provided in the UE is equal to or greater than a second value. In this case, K is an integer of 2 or more. The control unit may decide that for each of the T first antenna ports selected as representatives from each of the T first antenna port groups in the UE, the UE should report T × G ways of information regarding the radio wave propagation characteristics between each of the G second antenna ports on the base station side to the network. T takes a value between 1 and K.

[0025] According to one aspect of this disclosure, at the base station, two or more first antenna ports with high correlation of radio wave propagation characteristics are grouped together as a first antenna port group. Among the two or more first antenna ports included in the first antenna port group, information regarding the radio wave propagation characteristics of a representative first antenna port can be shared, reused, or substituted. Therefore, according to one aspect of this disclosure, antenna port groups can also be formed at the base station based on the high correlation of radio wave propagation characteristics between antenna ports on the base station side.

[0026] Furthermore, since base stations are distributed and their physical locations differ between antenna ports on different base stations, the correlation of radio wave propagation characteristics is low. Therefore, if the base stations group the first antenna ports based on their high correlation of radio wave propagation characteristics, groups will be formed between two or more first antenna ports on the same base station, and it is highly unlikely that groups will be formed between two or more first antenna ports on different base stations.

[0027] Furthermore, in one aspect of this disclosure, the K first antenna ports on the base station side are classified into T first antenna port groups, and information regarding the radio wave propagation characteristics between the T first antenna ports representing the T first antenna port groups and the G second antenna ports representing the G second antenna port groups in the UE is reported from the UE to the network. As a result, the information regarding the radio wave propagation characteristics between the first antenna ports on the base station side and the second antenna ports provided in the UE, reported from the UE to the network, is T × G. In one aspect of this disclosure, the reporting of information regarding radio wave propagation characteristics can be reduced by (K × N) - (T × G) ways compared to normal, thereby further reducing network overhead.

[0028] In one aspect of the present disclosure, the control unit may further perform the following: for each of the G second antenna port groups in the UE, which include two or more second antenna ports, select as a representative second antenna port from among the two or more second antenna ports included in the second antenna port group, the second antenna port having the highest quality of received signals transmitted and received with one first antenna port on the base station side. The control unit may further perform the following: for each of the T first antenna port groups in the base station, which include two or more first antenna ports, select as a representative first antenna port from among the two or more first antenna ports included in the first antenna port group, the first antenna port having the highest quality of received signals transmitted and received with one second antenna port provided in the UE. The quality of the received signal may be determined by, for example, RSRP, RSSI, RSRQ, or SINR.

[0029] In one aspect of this disclosure, a representative antenna port can be selected for each of the first antenna port group on the base station side and the second antenna port group at the UE, based on the quality of the received signal.

[0030] Furthermore, the control unit may further select one representative second antenna port from each of the G second antenna port groups for each of the K first antenna ports on the base station side. Alternatively, the control unit may further select one representative second antenna port from each of the G second antenna port groups for each of the T first antenna ports selected as representatives of each of the T first antenna port groups on the base station side.

[0031] By selecting a second antenna port representing a second antenna port group on the UE side for each first antenna port on the base station side, or for each first port representing a first antenna port group, it is possible to prevent the concentration of the second antenna ports on the UE side, where information regarding radio wave propagation characteristics is reported, into a single second antenna port on the UE side.

[0032] In one aspect of the present disclosure, the control unit may further notify the UE of one or more such combinations for which reporting has been decided. In this case, the information processing device may be, for example, the control unit, base station, or relay station. This allows the UE to be notified of the combinations to be reported, and the information on radio wave propagation characteristics that the UE reports to the network to be limited to the combinations that have been decided to be reported.

[0033] In one aspect of the present disclosure, the control unit may further instruct the UE to transmit an uplink measurement signal from each of the N second antenna ports, and receive from one or more base stations the radio wave propagation characteristics between each of the N second antenna ports provided on the UE and each of the K first antenna ports on the base station side, based on the uplink measurement signals transmitted from each of the N second antenna ports provided on the UE. In this case, the information processing device may be, for example, the control device or one or more of the base stations. The uplink measurement signal may be an uplink reference signal or an uplink data signal. The reference signal used as the uplink measurement signal may be, for example, an SRS (Sounding Reference Signal), a DM (DeMmodulation)-RS, a PT (Phase Tracking)-RS, or any other uplink reference signal.

[0034] In one aspect of this disclosure, information regarding the radio wave propagation characteristics between the UE and the base station's antenna ports is obtained by transmitting N uplink measurement signals from each of the N second antenna ports provided on the UE. Typically, the number of antenna ports provided on a UE is fewer than the number of antenna ports on the base station. Therefore, according to one aspect of this disclosure, the overhead associated with obtaining information regarding the radio wave propagation characteristics between the UE and the base station's antenna ports can be reduced.

[0035] In one aspect of the present disclosure, the control unit may further instruct one or more base stations to transmit downlink measurement signals from each of the K first antenna ports, and receive from the UE radio wave propagation characteristics between each of the K first antenna ports on the base station side and each of the N second antenna ports provided on the UE, based on the downlink measurement signals transmitted from each of the K first antenna ports on the base station side. In this case, the information processing device may be, for example, the control device or one or more of the one or more base stations. The downlink measurement signals may be downlink reference signals 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 signals.

[0036] In one aspect of this disclosure, information regarding the radio wave propagation characteristics between the UE and the base station's antenna ports is obtained by the UE receiving and measuring downlink measurement signals from each of the K first antenna ports on the base station. Typically, the UE consumes less power receiving signals than transmitting them. Therefore, according to one aspect of this disclosure, the power consumption of the UE related to obtaining information regarding the radio wave propagation characteristics between the UE and the base station's antenna ports can be reduced.

[0037] In one aspect of this disclosure, the information processing device may be the UE. In this case, the control unit may further perform the following: obtain information on the radio wave propagation characteristics between each of the K first antenna ports on the base station side and each of the N second antenna ports provided in the UE, based on the downlink measurement signals transmitted from each of the K first antenna ports on the base station side. When the information processing device is the UE, the UE determines the combination of antenna ports on the base station side to report the information on the radio wave propagation characteristics, so it is not necessary to transmit the information on the radio wave propagation characteristics between each antenna port on the UE and the base station side, obtained from the downlink measurement signals, to the network side. This reduces the overhead associated with reporting the information on the radio wave propagation characteristics between each antenna port on the UE and the base station side to the network, as well as the power consumption of the UE.

[0038] Furthermore, the control unit may also notify the network of one or more such combinations for which reporting of radio wave propagation characteristics has been decided. This allows the UE and the network to share one or more such combinations for which reporting of radio wave propagation characteristics has been decided.

[0039] Another aspect of the present disclosure can be identified as a method by which a computer performs the processing of the information processing device. The method includes the computer performing the following: In a UE having N second antenna ports that receive signals simultaneously transmitted from a total of K first antenna ports of one or more base stations, classifying the N second antenna ports into G second antenna port groups, each containing one or more second antenna ports, by grouping two or more second antenna ports whose correlation value with respect to one of the K first antenna ports on the base station side is greater than or equal to a first value; and deciding to have the UE report information regarding radio wave propagation characteristics to the network for each of the K first antenna ports and each of the G second antenna ports selected as representatives from each of the G second antenna port groups, for K × G one-to-one combinations of first antenna ports on the base station side and second antenna ports provided in the UE.

[0040] Another aspect of the present disclosure may also specify the method as a program for causing a computer to execute, and a computer-readable, non-temporary storage medium on which the program is recorded.

[0041] 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.

[0042] <First Embodiment> Figure 1 shows an example of the system configuration of the communication system 100. 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, for example, 5G, LTE (Long Term Evolution), and mobile communication methods of 5G 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.

[0043] 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 unit 1.

[0044] A distributed base station is equipped with an antenna capable of forming multiple beam patterns. The antenna 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 adaptively control each antenna element to electrically form one or more beams and change their respective beam patterns. The beams and beam patterns of the distributed base station are controlled by a control device 1. The beams formed at the distributed base station are identified by antenna ports.

[0045] A base station comprises a Radio Unit (RU), a Distributed Unit (DU), and a Centralized Unit (CU). While a distributed base station may also include a RU and a CU, the minimum configuration requires a DU; therefore, a distributed base station will hereafter be simply referred to as a DU. Hereafter, an antenna port provided on a DU will be referred to as a DU antenna port or a DU port. A DU antenna port is an example of a "first antenna port."

[0046] 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 these, and UE 2 may be a stationary terminal device such as an IoT 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 small base stations, mobile base stations, in-vehicle devices, and smartphones. In the first embodiment, UE 2 is equipped with multiple antennas such as monopole antennas and dipole antennas, and these multiple antennas can form one or more beams. The beams formed in UE 2 are identified by antenna ports. Hereinafter, the antenna ports provided in UE 2 will be referred to as UE antenna ports or UE ports. The UE antenna port is an example of a "second antenna port".

[0047] 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.

[0048] 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 DU antenna ports.

[0049] In the first embodiment, the k-th DU antenna port provided on DU#m is denoted as DU port #m-k, or simply DU port #m-k. The number of DU antenna ports provided on DU#m is represented by Km. The number of DUs included in the communication system 100 is represented by M. The number of DU antenna ports present in the communication system 100, i.e., the number of DU antenna ports on the base station side, is represented by K. The value of K is the sum of K1, K2, ..., Km-1, and Km. M, K, and Km are integers of 1 or more. The variable m takes values ​​in the range from 1 to M. The variable k takes values ​​in the range from 1 to Km.

[0050] In the first embodiment, UE 2 comprises a plurality of UE antenna ports. In the first embodiment, the nth UE antenna port provided in UE 2 is denoted as UE port #n, or simply UE#n. The number of UE antenna ports provided in UE 2 is represented by N. In the first embodiment, N is an integer greater than or equal to 2. The variable n takes values ​​in the range from 1 to N.

[0051] UE 2 periodically or irregularly measures the radio wave propagation characteristics between UE antenna port #n and DU antenna ports #m-k at predetermined intervals and reports information regarding these propagation characteristics to control device 1. The information regarding radio wave propagation characteristics reported to control device 1 includes, for example, phase offset, L1-RSRP, RSRQ, RSSI, SINR, CSI, and interference measurement information such as inter-cell interference. The reported information regarding radio wave propagation characteristics is used, for example, to control coordinated transmission between DUs.

[0052] Since there is symmetry between the radio wave propagation characteristics in the uplink direction from UE antenna port #n to DU antenna ports #m-k and the radio wave propagation characteristics in the uplink direction from DU antenna ports #m-k to UE antenna port #n, it is sufficient to obtain the radio wave propagation characteristics in either direction. Therefore, UE 2 transmits information on radio wave propagation characteristics equal to the product of the number of UE antenna ports N and the number of DU antenna ports K to the control device 1. Reporting to the control device 1 is also referred to as reporting to the network.

[0053] In this case, if UE 2 is a small device such as a smartphone, the N UE antenna ports provided on UE 2 are physically located in very close proximity to each other, to the point where they can be considered to be in almost the same position. In such a case, there is a high probability that the radio wave propagation characteristics of the N UE antenna ports provided on UE 2 to a given DU antenna port will be highly correlated. If the radio wave propagation characteristics of the N UE antenna ports provided on UE 2 to a given DU antenna port are highly correlated, then the radio wave propagation characteristics of each of the N UE antenna ports to that given DU antenna port can be considered to be the same.

[0054] In the first embodiment, the control device 1 classifies the N UE antenna ports provided on the UE 2 into G UE antenna groups by grouping two or more UE antenna ports with high correlation in radio wave propagation characteristics. A UE antenna group includes one or more UE antenna ports. If a single UE antenna port contains only one UE antenna port, that single UE antenna port is a UE antenna port that does not have a high correlation in radio wave propagation characteristics with any other UE antenna ports for a given DU antenna port. Hereinafter, radio wave propagation characteristics will be simply referred to as propagation characteristics.

[0055] The control device 1 selects one representative UE port from each of the G UE antenna port groups, for a total of G representative UE ports, and determines that each of the combinations of these G representative UE ports and each of the K DU antenna ports will be the target for UE 2 to report propagation characteristic information. This reduces the amount of propagation characteristic information reported from UE 2 to the control device 1 to the number obtained by multiplying the number of UE antenna port groups G by the number of DU antenna ports K. A UE antenna port group is an example of a "second antenna port group". The representative UE port of a UE antenna port group is also called a reference UE antenna port.

[0056] Figures 2A, 2B, and 2C are diagrams illustrating step 1 of the reporting port selection process according to the first embodiment. The reporting port selection process is the process of selecting a one-to-one combination of UE antenna ports and DU antenna ports for which UE 2 will report propagation characteristics information to the control device 1. Figures 2A to 2C are explained based on the communication system 100 shown in Figure 1. Therefore, in Figures 2A to 2C, the number of UE ports N = 2, the number of DUs M = 3, and the number of DU ports K = 6. Hereinafter, the one-to-one combination of UE antenna ports and DU antenna ports for which propagation characteristics information will be reported will be referred to as the reporting port combination or reporting combination.

[0057] Figure 2A shows the process performed in step 1 of procedure 1. In step 1 of procedure 1, an uplink reference signal is transmitted from UE port #1 of UE 2. The uplink reference signal used in step 1 of procedure 1 is, for example, SRS. However, it is not limited to this, and DM-RS, PT-RS, or other uplink reference signals may be used, or an uplink data signal may be used. The uplink reference signal or data signal used in step 1 of procedure 1 is an example of an "uplink measurement signal".

[0058] DU#1 measures the propagation characteristics in the uplink direction from UE port #1 to DU port #1-1 and from UE port #1 to DU port #1-2. DU#2 measures the propagation characteristics in the uplink direction from UE port #1 to DU port #2-1 and from UE port #2 to DU port #2-2. DU#3 measures the propagation characteristics in the uplink direction from UE port #1 to DU port #3-1 and from UE port #1 to DU port #3-2. The propagation characteristic in the uplink direction from UE port #n to DU port #m-k is h ＵＥ＝ｎ ＤＵ＝ｍ，ｋ It is expressed as h ＵＥ＝ｎ ＤＵ＝ｍ，ｋ This is also called the channel response. Furthermore, the propagation characteristics obtained in step 1 are h ＵＥ＝ｎ ＤＵ＝ｍ，ｋIt is denoted as (1).

[0059] In FIG. 2B, the process performed in step 2 of procedure 1 is shown. In step 2 of procedure 1, a uplink reference signal is transmitted from UE port #2 of UE 2. By DU#1, the propagation characteristics h ＵＥ＝２ ＤＵ＝１，１ (2), h ＵＥ＝２ ＤＵ＝１，２ (2), are measured. By DU#2, the propagation characteristics h ＵＥ＝２ ＤＵ＝２，１ (2), h ＵＥ＝２ ＤＵ＝２，２ (2), are measured. By DU#3, the propagation characteristics h ＵＥ＝２ ＤＵ＝３，１ (2), h ＵＥ＝２ ＤＵ＝３，２ (2), are measured. Note that the transmission of the uplink reference signal in steps 1 and 2 is performed within a time period in which the propagation characteristics can be considered the same (also referred to as a time period in which the propagation environment does not change). Note that it is also possible to transmit uplink reference signals from UE port #1 and UE port #2 at the same time using a cyclic sequence, that is, to perform steps 1 and 2 simultaneously.

[0060] In FIG. 2C, the processes performed in steps 3 and 4 of procedure 1 are shown. In step 3 of procedure 1, for each of the DU ports #m - k, when the correlation between the propagation characteristics h ＵＥ＝１ ＤＵ＝ｍ，ｋ (1) and h ＵＥ＝２ ＤＵ＝ｍ，ｋ (2) is high, UE port #1 and UE port #2 are grouped. As a result, for the DU port #m - k, one UE antenna port group including UE port #1 and UE port #2 is formed. The UE antenna port group is also referred to as a UE port group. Grouping two or more antenna ports with high correlation of propagation characteristics as in step 3 of procedure 1 and classifying a plurality of antenna ports into one or more groups is referred to as antenna port grouping. For UE ports, it is referred to as UE port grouping. For DU ports, it is referred to as DU port grouping.

[0061] The degree of correlation between the propagation characteristics h1 and h2 of two antenna ports is determined, for example, based on the correlation coefficient of the two propagation characteristics h1 and h2. The method for calculating the correlation coefficient is well known. The correlation coefficient takes a value in the range of -1 to +1. A correlation coefficient value closer to -1 indicates a high negative correlation. A correlation coefficient value closer to +1 indicates a high positive correlation. A correlation coefficient closer to 0 indicates a low correlation. In the first embodiment, a high correlation between propagation characteristics h1 and h2 is determined when the absolute value of the correlation coefficient is greater than or equal to a first threshold. The first threshold is, for example, 0.7. However, the value of the first threshold is not limited to this. Furthermore, the method for determining the degree of correlation is not limited to the method described above. A high correlation between propagation characteristics h1 and h2 may also be determined when the correlation coefficient of propagation characteristics h1 and h2 is greater than or equal to the first threshold and close to -1, or when the correlation coefficient of propagation characteristics h1 and h2 is greater than or equal to the first threshold and close to +1.

[0062] The degree of correlation between the propagation characteristics of three or more antenna ports is also determined based on the correlation coefficient of the propagation characteristics of pairs of antenna ports. For example, if there are three antenna ports A, B, and C, and the absolute value of the correlation coefficient between the pair of antenna ports A and B, and the absolute value of the correlation coefficient between the pair of antenna ports A and C are both greater than or equal to a first threshold, then the propagation characteristics of the three antenna ports A, B, and C are determined to be highly correlated. The absolute value of the correlation coefficient is just one example of a value that indicates the degree of correlation of radio wave propagation characteristics. Note that the criteria for determining the degree of correlation of propagation characteristics between multiple antenna ports are not limited to the correlation coefficient; covariance or other methods may also be used.

[0063] In step 4 of procedure 1, a representative UE port is selected from the UE antenna port group for DU port #m-k. The representative UE port may be selected from among the UE ports included in the UE antenna port group, for example, the UE port with the best received signal quality. The received signal quality may be determined based on, for example, RSRP, RSSI, RSRQ, or SINR. For example, the received signal strength can be determined by the absolute value of the propagation characteristic h. However, the representative UE port is not limited to being selected based on the received signal quality, but may be selected by other criteria, or may be randomly selected from the UE ports included in the UE antenna port group. If there is only one UE port in the UE port group, that one UE port becomes the representative UE port of that UE port group.

[0064] Step 5 of Procedure 1 creates a combination of DU port #m-k and the representative UE port corresponding to DU port #m-k. Steps 3 through 5 of Procedure 1 are performed for each DU port. The combination created in Step 5 of Procedure 1 becomes the combination of UE port and DU port to be reported. That is, when Procedure 1 of the port selection process is executed, the combination of UE port and DU port to be reported becomes the combination of each DU port and the representative UE port corresponding to each DU port. Therefore, the information on propagation characteristics reported from UE 2 to control device 1 is the number obtained by multiplying the number of UE antenna groups G by the number of DU ports K.

[0065] In the example shown in Figure 2C, it is assumed that for every DU port, one UE antenna port group is formed, including UE port #1 and UE port #2. In Figure 2C, the number of UE antenna port groups G = 1. UE port #2 is selected as the representative UE port corresponding to DU port #1-1. UE port #2 is selected as the representative UE port corresponding to DU port #1-2. UE port #2 is selected as the representative UE port corresponding to DU port #1. UE port #1 is selected as the representative UE port corresponding to DU port #2-1. UE port #1 is selected as the representative UE port corresponding to DU port #2-2. UE port #2 is selected as the representative UE port corresponding to DU port #3-1. UE port #2 is selected as the representative UE port corresponding to DU port #3-2.

[0066] Therefore, as a result of the execution of procedure 1 for selecting the reporting target ports, the information regarding propagation characteristics reported from UE 2 to control device 1 is reduced from the number obtained by multiplying the number of UE ports (N=2) by the number of DU ports (K=6) (N×K=2×6=12) to the number obtained by multiplying the number of UE antenna port groups (G=1) by the number of DU ports (K=6) (G×K=1×6=6), in the example shown in Figure 2C.

[0067] Furthermore, if there is a high correlation in the propagation characteristics of one DU port among the UE ports provided in UE 2, it is highly likely that the propagation characteristics of all other DU ports will also be highly correlated. Therefore, the result of grouping UE ports for each DU port is likely to be the same for all DU ports. For this reason, in step 3 of procedure 1, UE ports are grouped for each DU port, but in Figure 2C, the grouping of UE ports is the same for all DU ports.

[0068] Furthermore, in step 3 of procedure 1, UE ports are grouped for each DU port, but it is highly likely that the result of the UE port grouping will be the same for all DU ports. Therefore, in step 3 of procedure 1, UE port grouping may be performed for one DU port and the result applied to the other DU ports.

[0069] Furthermore, in step 5 of procedure 1, the combination of each DU port and the representative UE port selected for each DU port is determined to be reported. However, if the results of the UE port grouping for one DU port are to be applied to other DU ports, the representative UE port selected for that one DU port may be used as the representative UE port corresponding to the other DU ports. In this case, in the example shown in Figure 2C, if UE port #1 is selected as the representative UE port, the combinations to be reported would be, for example, UE port #1 and DU port #1-1, UE port #1 and DU port #1-2, UE port #1 and DU port #2-1, UE port #1 and DU port #2-2, UE port #1 and DU port #3-1, and UE port #1 and DU port #3-2.

[0070] Figure 3 shows an example of the sequence in step 1 of the process for selecting the reporting target ports. In Figure 3, one DU is shown representing M units of DUs. The processing for all M units of DU is the same. Also, in Figure 3, it is assumed that each DU has multiple DU ports. However, a DU may have only one port.

[0071] In S111, the control device 1 sends an instruction to UE 2 to transmit the uplink reference signal. Along with this instruction, it transmits information about the resources allocated for the uplink reference signal to UE 2. It also transmits information about the resources allocated for measuring the uplink reference signal to each DU.

[0072] In S112, UE 2 transmits an uplink reference signal from each UE port. In S113, each DU receives the uplink reference signal transmitted from each UE port of UE 2 through its respective DU port and calculates the propagation characteristics between each DU port and each UE port based on the uplink reference signal. The processes in S112 and S113 correspond to the processes in steps 1 and 2 of procedure 1 of the port selection process for reporting.

[0073] In S114, each DU reports the propagation characteristics between each DU port and each UE port to the control device 1. In addition to propagation characteristics, each DU may also transmit values ​​that serve as indicators of the quality of the received signal, such as RSRP.

[0074] In S115, the control device 1 classifies the N UE ports for each DU port into G UE port groups by grouping two or more UE ports with high correlation in propagation characteristics, and selects a representative UE port from each of the G UE port groups. The process in S115 corresponds to the processes in steps 3 and 4 of procedure 1 of the process for selecting the reporting target ports.

[0075] In S116, the control device 1 determines the combination of each of the K DU ports and the representative UE port selected for each DU port as the combination of ports to be reported. The process in S116 corresponds to the process in step 5 of procedure 1 of the process for selecting the ports to be reported. In S117, the control device 1 notifies UE 2 of the combination of ports to be reported. Subsequently, UE 2 performs measurements for each UE port and transmits information regarding the radio wave propagation characteristics of the combination of ports to be reported to the control device 1 as a measurement result. Information indicating whether the report to which the combination of ports to be reported applies is a periodic report or a non-periodic report may also be transmitted to UE 2 along with the notification of the combination of ports to be reported.

[0076] Figure 4 illustrates the hardware configuration of the control device 1. The control device 1 comprises 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).

[0077] 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".

[0078] 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 a "computer" and an "information processing device". Note that the hardware configuration of the control device 1 is not limited to that shown in Figure 4.

[0079] Figure 5 shows an example of the functional configuration of the control device 1. The control device 1 includes a control unit 11 as part of its functional configuration. The function of the control unit 11 is achieved by the CPU 101 executing a predetermined program.

[0080] In the first embodiment, the control unit 11 controls CJT as one of the coordinated transmissions from M base stations to UE 2. More specifically, the control unit 11 selects the distributed base stations that will perform coordinated transmission to UE 2, allocates radio resources for measuring propagation characteristics, allocates radio resources for reporting by UE 2, performs phase offset compensation, etc. In addition, as one of the controls for coordinated transmission, the control unit 11 performs the following in the selection process of reporting target ports: sending a reference signal for the uplink to UE 2 (S115 in Figure 3), grouping of UE ports (step 3 of procedure 1, S115 in Figure 3), and determining the combination of reporting target ports and notifying UE 2 (step 4 of procedure 1, S116 and S117 in Figure 3). Details of the processing of the control unit 11 will be described later. Note that the functional configuration of the control device 1 is not limited to that shown in Figure 5.

[0081] Figure 6 shows an example of the hardware configuration of UE 2. UE 2 includes a CPU 201, main memory 202, external storage 203, wireless communication device 204, and antenna 205. The CPU 201, main memory 202, and external storage 203 are the same as those of CPU 101, main memory 102, and external storage 103.

[0082] 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 6. 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 6.

[0083] Figure 7 shows an example of the functional configuration of UE 2. UE 2 comprises a control unit 21 and a measurement unit 22. The functions of the control unit 21 and the measurement unit 22 are achieved by the CPU 201 executing a predetermined program.

[0084] 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.

[0085] In the first embodiment, the control unit 21 receives notification from the control device 1 of the combination of ports to be reported (e.g., S117 in Figure 3). When the control unit 21 reports information on radio wave propagation characteristics as measurement results to the control device 1, it transmits information on radio wave propagation characteristics for the combination of ports to be reported notified by the control device 1. Also in the first embodiment, when the control unit 21 receives an instruction from the control device 1 to transmit an uplink reference signal (e.g., S111 in Figure 3), it transmits an uplink reference signal through each UE port (e.g., S112 in Figure 3).

[0086] 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. Each DU transmits a downlink reference signal through its respective DU port according to the allocation of radio resources for measuring radio wave propagation characteristics. The measurement unit 22 receives the downlink reference signals transmitted through each DU port of 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. Note that the functional configuration of UE 2 is not limited to the example shown in Figure 7.

[0087] Figure 8 is an example of a flowchart of the processing of the control device 1 related to step 1 of the process of selecting the reporting target port. The processing shown in Figure 8 is started, for example, when predetermined conditions are met for the start of cooperative transmission such as CJT or transmission using MIMO, or when instructions are received from a higher-layer application. The main entity executing the processing shown in Figure 8 is the CPU 101 of the control device 1, but for convenience, the explanation will mainly focus on the functional components. The same applies to the explanation of the flowcharts from Figure 8 onward.

[0088] In OP111, the control unit 11 sends an instruction to UE 2 to transmit an uplink reference signal. The processing of OP111 corresponds, for example, to the processing of S111 in Figure 3. In OP112, the control unit 11 determines whether or not it has received a report of radio wave propagation characteristics (channel response) from each DU. Each DU may receive information regarding radio wave propagation characteristics that includes the same type of information as the report from the UE. If a report of radio wave propagation characteristics (channel response) is received from each DU (OP112: YES), the process proceeds to OP113. The control unit 11 waits until a report of radio wave propagation characteristics (channel response) is received from each DU (OP112: NO). The processing of OP112 corresponds, for example, to the process in S114 in Figure 3 where the control device 1 receives a report from the DU.

[0089] The processing from OP113 to OP115 is performed for each DU port. The DU ports that are subject to processing from OP113 to OP115 are designated as DU ports #m-k. In OP113, the control unit 11 groups the UE ports for DU ports #m-k. Specifically, the control unit 11 groups two or more UE ports with high correlation in propagation characteristics into one group, classifying N UE ports into G UE port groups and grouping them.

[0090] In OP114, the control unit 11 selects one representative UE port from each of the G UE port groups. The representative UE port is, for example, the port with the best quality of received signal at DU ports #m-k among the UE ports included in the UE port group. If there is only one UE port in the UE port group, that single UE port becomes the representative UE port of that UE port group. The processing in OP113 and OP114 corresponds, for example, to the processing in S115 of Figure 3.

[0091] In OP115, the control unit 11 determines the combination of the representative UE port selected in OP114 and DU port #m-k to be reported. The processing in OP115 corresponds, for example, to the processing in S116 in Figure 3. Once the processing from OP113 to OP115 is executed for each DP port, the combination of each DU port and the representative UE port corresponding to each DU port is determined as the combination to be reported.

[0092] In OP116, the control unit 11 notifies the UE 2 of the combination of ports to be reported. The processing in OP116 corresponds, for example, to the processing in S117 in Figure 3. After that, the processing shown in Figure 8 is completed.

[0093] Note that the process shown in Figure 8 is an example, and the processing of the control device 1 related to step 1 of the process for selecting the reporting target ports is not limited to the process shown in Figure 8. If the result of grouping UE ports for one DU port is also applicable to other DU ports, the UE port grouping process of OP 113 is executed for that one DU port, and the representative UE port selection process of OP 114 and the determination of the reporting target combination of OP 115 are executed for each DU port. Also, if the result of grouping UE ports and the representative UE port for one DU port are also applicable to other DU ports, the UE port grouping process of OP 113 and the representative UE port selection process of OP 114 are executed for that one DU port, and the determination of the reporting target combination of OP 115 is executed for each DU port. The one DU port on which the UE port grouping process and / or the representative UE port selection process are performed may be any of the K DU ports.

[0094] <Effects of the First Embodiment> In the first embodiment, UE antenna ports are grouped together by two or more UE antenna ports with high correlation of propagation characteristics, a representative UE port is selected, and K x G combinations of DU ports and representative UE ports are determined to be the subject of reporting. This reduces the amount of information on radio wave propagation characteristics that UE 2 reports to the control device 1, thereby reducing the overhead of the wireless network.

[0095] Furthermore, in step 1 of the reporting port selection process according to the first embodiment, the reference signals used to acquire the propagation characteristics between each UE port and each DU port are the reference signals of the N uplinks transmitted from each of the N UE ports. Therefore, in step 1 of the reporting port selection process according to the first embodiment, the number of reference signals used to acquire the propagation characteristics between each UE port and each DU port can be kept to a minimum.

[0096] <Modification 1 of the First Embodiment> The same applies to the K DU antenna ports as to the N UE antenna ports provided in UE 2. That is, if there is a high correlation between the radio wave propagation characteristics of two or more DU antenna ports with respect to a certain UE antenna port, then the radio wave propagation characteristics of each of those two or more DU antenna ports with respect to that UE antenna port can be considered to be the same. Therefore, the K DU antenna ports can be grouped in the same way as the N UE antenna ports. In the modification of the First Embodiment, in addition to step 1 of the selection process for the reporting target port according to the First Embodiment, the K DU ports are also grouped.

[0097] Figure 9 shows the processing of procedure 1A of the reporting target port selection process according to a modified example of the first embodiment. Figure 9 is explained based on the communication system 100 shown in Figure 1, similar to Figures 2A to 2C. Steps 1 to 4 of procedure 1A of the reporting target port selection process are the same as steps 1 to 4 of procedure 1.

[0098] In step 5 of procedure 1A, the DU ports are grouped for each DU#m. In the example shown in Figure 9, the propagation characteristics h are grouped for each of DU#1 to DU#3. ＵＥ＝１ ＤＵ＝ｍ，１ (1) and h ＵＥ＝１ ＤＵ＝ｍ，２ (1), and propagation characteristics h ＵＥ＝２ ＤＵ＝ｍ，１ (2) and h ＵＥ＝２ ＤＵ＝ｍ，２(2) If there is a high correlation between each of the above, DU port #m-1 and DU port #m-2 are grouped together. This forms one DU antenna port group that includes DU port #m-1 and DU port #m-2. A DU antenna port group is also called a DU port group. When step 5 of procedure 1A is performed, T DU port groups are formed from K DU ports.

[0099] In the example shown in Figure 9, four DU port groups are formed: a group including DU port #1-1 and DU port #1-2, a group including DU port #2-1 and DU port #2-2, a group including DU port #3-1, and a group including DU port #3-2. In the example shown in Figure 9, the number of DU port groups T = 4. Note that the propagation characteristics h ＵＥ＝１ ＤＵ＝ｍ，１ (1) and h ＵＥ＝１ ＤＵ＝ｍ，２ (1), and propagation characteristics h ＵＥ＝２ ＤＵ＝ｍ，１ (2) and h ＵＥ＝２ ＤＵ＝ｍ，２ (2) Instead of determining the correlation for both, you may determine the correlation for either one and group DU port #m-1 and DU port #m-2.

[0100] In step 6 of procedure 1A, one representative DU port is selected for each of the T DU antenna port groups. The representative DU port, like the representative UE port, may be selected from among the DU ports included in the DU antenna port group, for example, the DU port with the best received signal quality. However, it is not limited to this, and the representative DU port may be selected by other criteria or randomly selected from the DU ports included in the DU antenna port group. If there is only one DU port in a DU port group, that one DU port becomes the representative DU port for that DU port group. In the example shown in Figure 9, the representative UE ports for each DU port group are shown in black. In the example shown in Figure 9, DU port #1-2, DU port #2-2, DU port #3-1, and DU port #3-2 are selected as representative DU ports.

[0101] In step 7 of procedure 1A, a combination is created between the representative DU port of each DU antenna port group and the representative UE port corresponding to that representative DU port. The combination created in step 7 of procedure 1A becomes the combination to be reported. Therefore, the information on propagation characteristics reported from UE 2 to control device 1 will be the number obtained by multiplying the number of UE antenna groups G by the number of DU antenna port groups T. In the example shown in Figure 2C, the four combinations to be reported are UE port #2 and DU port #1-2, UE port #1 and DU port #2-2, UE port #2 and DU port #3-1, and UE port #2 and DU port #3-2.

[0102] Therefore, as a result of the execution of procedure 1A for selecting the reporting target ports, the information regarding propagation characteristics reported from UE 2 to control device 1 is reduced from the number obtained by multiplying the number of UE ports (N=2) by the number of DU ports (K=6) (N×K=2×6=12) to the number obtained by multiplying the number of UE antenna port groups (G=1) by the number of DU antenna port groups (T=4) (G×T=1×4=4), in the example shown in Figure 9.

[0103] In the example shown in Figure 9, DU grouping is performed for each DU, but DU port grouping may also be performed for all DU ports. Since DUs are distributed, the likelihood of high correlation in propagation characteristics between DU ports on different DUs is very low. Therefore, even if DU ports are grouped for all K DU ports without distinguishing between DUs, the likelihood of DU port groups being formed across DUs is very low, and the DU ports included in a DU port group are likely to be ports on the same DU. Therefore, even if DU ports are grouped for all DU ports, the grouping results are likely to be the same as when DU grouping is performed for each DU.

[0104] Figure 10 shows an example sequence in procedure 1A of the process for selecting the reporting target ports. The assumptions in Figure 10 are the same as in Figure 3. Steps S111 to S115 are the same as in Figure 3. Based on the uplink reference signal from UE 2 (S111, S112), the propagation characteristics between each DU port and each UE port are acquired for each DU port (S113, S114), the N UE ports are classified into G UE port groups, and a representative UE port is selected from each of the G UE port groups (S115).

[0105] In S121, the control device 1 groups the DU ports for each DU, classifying the K DU ports into T DU port groups, and selects a representative DU port from each of the T DU port groups. The process in S121 corresponds to the processes in steps 5 and 6 of procedure 1A of the process for selecting the ports to be reported.

[0106] In S122, the control device 1 determines the combination of each of the T representative DU ports and the representative UE port corresponding to each representative DU port as the combination of ports to be reported. The process in S122 corresponds to the process in step 7 of procedure 1A of the process for selecting ports to be reported. In S123, the control device 1 notifies UE 2 of the combination of ports to be reported.

[0107] Figure 11 is an example of a flowchart of the process of the control device 1 related to procedure 1A of the process of selecting the reporting target port. The start conditions for the process shown in Figure 11 are the same as those for the process shown in Figure 8. The processes from OP121 to OP124 are the same as those for OP111 to OP114 in Figure 8. The control unit 11 sends an instruction to UE 2 to transmit the uplink reference signal (OP121), and when it receives propagation characteristics (channel response) reports from each DU (OP122: YES), it groups the UE ports for each DU port (OP123) and selects a representative UE port (OP124).

[0108] In OP125, the control unit 11 groups the DU ports. Specifically, the control unit 11 groups two or more DU ports with high correlation in propagation characteristics for each DU into one group, and classifies the K DU ports into T DU port groups and groups them. Alternatively, instead of searching for two or more DU ports with high correlation in propagation characteristics for all DU ports, the control unit 11 may search for them.

[0109] In OP126, the control unit 11 selects one representative DU port from each of the T DU port groups. The representative DU port is selected, for example, from among the DU ports included in the DU port group, which has the best quality of received signals from any of the UE ports. If there is only one DU port in the DU port group, that single DU port becomes the representative DU port for that DU port group. The processing of OP125 and OP126 corresponds, for example, to the processing of S121 in Figure 10.

[0110] In OP127, the control unit 11 determines the combinations of each of the T representative DU ports selected in OP126 and the representative UE port corresponding to that representative DU port to be reported. The processing in OP127 corresponds, for example, to the processing in S122 of Figure 10. In OP128, the control unit 11 notifies UE 2 of the combinations of ports to be reported. The processing in OP128 corresponds, for example, to the processing in S123 of Figure 10. After that, the processing shown in Figure 11 is completed.

[0111] Note that the process shown in Figure 11 is just one example, and the processing of the control device 1 related to procedure 1A of the process for selecting the reporting target port is not limited to the processing shown in Figure 11. For example, if the result of grouping UE ports for one DU port is also applicable to other DU ports, the processing of OP123 may be performed for that one DU port. For example, if the result of grouping UE ports for one DU port and the representative UE port are also applicable to other DU ports, the processing of OP123 and OP124 may be performed for that one DU port.

[0112] In a modified version of the first embodiment, in addition to grouping the UE antenna ports, DU ports are also grouped, and T x G combinations of representative DU ports and representative UE ports are determined to be the subject of reporting. This further reduces the amount of information on radio wave propagation characteristics that UE 2 reports to the control device 1, and further reduces the overhead of the wireless network.

[0113] <Modification 2 of the First Embodiment> In the first embodiment, the control device 1 instructs the UE 2 to transmit an uplink reference signal, the UE 2 transmits an uplink reference signal, and each DU measures and transmits the propagation characteristics between each UE port and each DU port based on the uplink reference signal, thereby receiving the propagation characteristics between each UE port and each DU port from each DU (S112-S114 in Figure 3). Alternatively, the control device 1 may instruct each DU to transmit a downlink reference signal, each DU transmits a downlink reference signal, the UE 2 measures and transmits the propagation characteristics between each UE port and each DU port based on the downlink reference signal, thereby receiving the propagation characteristics between each UE port and each DU port from each DU.

[0114] <Second Embodiment> In the first embodiment, the UE ports are grouped, but in the second embodiment, the DU ports are grouped. In the second embodiment, explanations common to the first embodiment are omitted. In the second embodiment, the hardware configuration and functional configuration of the control device 1 and UE 2 are the same as in the first embodiment.

[0115] Figures 12A and 12B are diagrams illustrating step 2 of the selection process for reporting target ports according to the second embodiment. The assumptions for Figures 12A and 12B are the same as those for Figure 2A. Figure 12A shows the processes performed in steps 1 and 2 of step 2. In step 1 of step 2, an uplink reference signal is transmitted from UE port #1 of UE 2, and each DU determines the propagation characteristics h in the uplink direction from UE port #1 to each DU port. ＵＥ＝１ ＤＵ＝ｍ，ｋ (1) is measured.

[0116] In step 2 of procedure 2, DU ports are grouped within each DU. Specifically, within each DU, one DU antenna port is formed from two or more DU ports with high correlation of propagation characteristics h obtained in step 1 of procedure 2. In the example shown in Figure 12A, propagation characteristics h are grouped within each of DU#1 to DU#3. ＵＥ＝１ ＤＵ＝ｍ，１ (1) and h ＵＥ＝１ ＤＵ＝ｍ，２ If there is a high correlation with (1), DU port #m-1 and DU port #m-2 are grouped together. When step 2 of procedure 2 is performed, T DU port groups are formed from K DU ports. In the example shown in Figure 12A, four DU port groups are formed: a group containing DU port #1-1 and DU port #1-2, a group containing DU port #2-1 and DU port #2-2, a group containing DU port #3-1, and a group containing DU port #3-2. In the example shown in Figure 12A, the number of DU port groups T = 4. Note that in step 2 of procedure 2, DU port grouping may be performed on all K DU ports together, rather than on a per-DU basis.

[0117] Figure 12B shows the processes performed in steps 3 and 4 of procedure 2. In step 3 of procedure 2, one representative DU port is selected for each of the T DU antenna port groups. In the example shown in Figure 12B, the representative UE ports for each DU port group are shown in black. In the example shown in Figure 12B, DU port #1-2, DU port #2-2, DU port #3-1, and DU port #3-2 are selected as representative DU ports.

[0118] In step 4 of procedure 2, combinations are created for each of the N UE ports and each of the T representative DU ports. Therefore, the information on propagation characteristics reported from UE 2 to control device 1 will be the number obtained by multiplying the number of UE ports N by the number of DU antenna port groups T. In the example shown in Figure 12B, the eight combinations to be reported are UE port #1 and DU port #1-2, UE port #2 and DU port #1-2, UE port #1 and DU port #2-2, UE port #1 and DU port #3-1, UE port #2 and DU port #3-2, and UE port #2 and DU port #3-2.

[0119] Therefore, as a result of the execution of step 2 for selecting the ports to be reported, the information regarding propagation characteristics reported from UE 2 to control device 1 is reduced from the number obtained by multiplying the number of UE ports (N=2) by the number of DU ports (K=6) (N×K=2×6=12) to the number obtained by multiplying the number of UE ports (N=2) by the number of DU antenna port groups (T=4) (N×T=2×4=8), in the example shown in Figure 12B.

[0120] Figure 13 shows an example sequence in step 2 of the process for selecting the reporting target port. The assumptions in Figure 10 are the same as in Figure 3. In S211, the control device 1 sends an instruction to UE 2 to transmit an uplink reference signal through any one of the UE ports. In S212, UE 2 transmits an uplink reference signal from one of the UE ports. The UE port from which the uplink reference signal is transmitted may be randomly selected by UE 2, or it may be specified by the control device 1 along with the instruction to transmit the uplink reference signal.

[0121] In S213, each DU receives an uplink reference signal transmitted from one UE port of UE 2 through its respective DU port, and calculates the propagation characteristics between each DU port and that UE port based on the uplink reference signal. The processes in S212 and S213 correspond to the process in step 1 of procedure 2 of the process for selecting the reporting target port.

[0122] In S214, each DU reports the propagation characteristics between each DU port and the corresponding UE port to the control device 1. In addition to propagation characteristics, each DU may also transmit values ​​that serve as indicators of the quality of the received signal, such as RSRP.

[0123] In S215, the control device 1 classifies the K DU ports into T DU port groups by grouping two or more DU ports with high correlation in propagation characteristics, and selects a representative DU port from each of the T DU port groups. The process in S215 corresponds to the processes in steps 2 and 3 of procedure 2 of the process for selecting the ports to be reported.

[0124] In S216, the control device 1 determines the combination of each of the N UE ports and each of the T representative DU ports as the combination of ports to be reported. The process in S216 corresponds to the process in step 4 of procedure 2 of the process for selecting the ports to be reported. In S217, the control device 1 notifies UE 2 of the combination of ports to be reported.

[0125] Figure 14 is an example of a flowchart of the process of the control device 1 related to step 2 of the process of selecting the reporting target port. The start conditions for the process shown in Figure 14 are the same as those for the process shown in Figure 8.

[0126] In OP211, the control unit 11 sends an instruction to UE 2 to transmit an uplink reference signal from one UE port. The processing of OP211 corresponds, for example, to the processing of S211 in Figure 13. In OP212, the control unit 11 determines whether or not it has received a report of radio wave propagation characteristics (channel response) from each DU. If a report of radio wave propagation characteristics (channel response) is received from each DU (OP212: YES), the process proceeds to OP213. The control unit 11 waits until a report of radio wave propagation characteristics (channel response) is received from each DU (OP212: NO). The processing of OP212 corresponds, for example, to the process in S214 in Figure 13 where the control device 1 receives a report from the DU.

[0127] OP213 and OP214 are executed for each DU. The DU that is the target of processing OP213 and OP214 is denoted as DU#m. In OP213, the control unit 11 groups the DU ports in DU#m. Specifically, in DU#m, the control unit 11 groups two or more DU ports with high correlation in propagation characteristics into one group. In OP214, the control unit 11 selects one representative DU port from each of the DU port groups in DU#m. The processing of OP213 and OP214 corresponds, for example, to the processing in S215 of Figure 13. After processing OP213 and OP214 for each DU, K DU ports are classified into T DU port groups.

[0128] In OP215, the control unit 11 determines the combinations of each UE port and each of the T representative DU ports to be reported. The processing in OP215 corresponds, for example, to the processing in S216 in Figure 13. In OP216, the control unit 11 notifies UE 2 of the combinations of ports to be reported. The processing in OP216 corresponds, for example, to the processing in S217 in Figure 13. After that, the processing shown in Figure 14 is completed.

[0129] Note that the process shown in Figure 14 is just one example, and the processing of the control device 1 related to step 2 of the process for selecting the reporting target ports is not limited to the process shown in Figure 14. If, instead of grouping DU ports for each DU, DU ports are grouped for the entire DU port, then the processing of OP213 and OP214 is executed once for the entire DU port, rather than for each DU.

[0130] In the second embodiment, DU ports are grouped, and N × G combinations of each UE port and each representative DU port are determined to be the subject of reporting. This reduces the amount of information on radio wave propagation characteristics that UE 2 reports to the control device 1, thereby reducing the overhead of the wireless network.

[0131] Furthermore, in step 2 of the port selection process according to the second embodiment, the reference signal used to acquire the propagation characteristics between each UE port and each DU port is a single uplink reference signal transmitted from one UE port. Therefore, in step 2 of the port selection process according to the second embodiment, the number of reference signals used to acquire the propagation characteristics between each UE port and each DU port can be reduced.

[0132] <Modification 1 of the Second Embodiment> Figures 15A and 15B show the processing of step 2A of the reporting target port selection process according to a modification of the second embodiment. In the modification of the second embodiment, in addition to step 2 of the reporting target port selection process according to the second embodiment, N UE ports are also grouped. Figures 15A and 15B will be explained assuming the communication system 100 shown in Figure 1, similar to Figures 2A to 2C. Steps 1 to 3 of step 2A of the reporting target port selection process are the same as steps 1 to 3 of step 2.

[0133] Figure 15A shows the process performed in step 4 of procedure 2A. In step 4 of procedure 2A, a downlink reference signal is transmitted from each representative DU port #m-k. The downlink reference signal used in step 4 of procedure 2A is, for example, CSI-RS. However, it is not limited to this, and DM-RS, PT-RS, or other downlink reference signals may be used, or downlink data signals may be used. The downlink reference signal or data signal transmitted in step 4 of procedure 2A is an example of a "downlink measurement signal".

[0134] UE 2 is the propagation characteristic h^ from each representative DU port #m-k to each UE port #n in the downlink direction. ＵＥ＝ｎ ＤＵ＝ｍ，ｋ (2) is measured. h^ indicates the propagation characteristics in the downlink direction. Note that the transmission of the downlink reference signal in step 4 of procedure 2A is performed within the time after the transmission of the uplink reference signal transmitted in step 1 of procedure 2A, during which the propagation characteristics can be considered to be the same.

[0135] Figure 15B shows the processes performed in steps 5 through 7 of procedure 2A. In step 5 of procedure 2A, the propagation characteristics h^ are determined for each of the T representative DU ports. ＵＥ＝１ ＤＵ＝ｍ，ｋ (2) and h^ ＵＥ＝２ ＤＵ＝ｍ，ｋ If the correlation in (2) is high, UE port #1 and UE port #2 are grouped together. When step 5 of procedure 2A is performed, G UE port groups are formed from N UE ports. In the example shown in Figure 15B, a group is formed that includes UE port #1 and UE port #2. The number of UE port groups G = 1.

[0136] In step 6 of procedure 2A, a representative UE port is selected for each of the T representative DU ports, corresponding to each of the G UE antenna port groups. In step 7 of procedure 2A, combinations are created between the representative DU port of each DU antenna port group and the representative UE port corresponding to that representative DU port. The combinations created in step 7 of procedure 2A are the combinations to be reported.

[0137] Therefore, the information regarding propagation characteristics reported from UE 2 to control device 1 is the product of the number of UE antenna groups G and the number of DU antenna port groups T. In the example shown in Figure 15B, the four combinations to be reported are UE port #1 and DU port #1-2, UE port #1 and DU port #3-1, UE port #2 and DU port #2-2, and UE port #2 and DU port #3-2.

[0138] Therefore, as a result of the execution of procedure 2A for selecting the reporting target ports, the information regarding propagation characteristics reported from UE 2 to control device 1 is reduced from the number obtained by multiplying the number of UE ports (N=2) by the number of DU ports (K=6) (N×K=2×6=12) to the number obtained by multiplying the number of UE antenna port groups (G=1) by the number of DU antenna port groups (T=4) (G×T=1×4=4), in the example shown in Figure 15B.

[0139] Figure 16 shows an example sequence in procedure 2A of the process for selecting the reporting target ports. The assumptions in Figure 16 are the same as in Figure 13. Steps S211 to S215 are the same as in Figure 13. Based on the uplink reference signal from UE 2 (S211, S212), the propagation characteristics between each DU port and one UE port are acquired (S213, S214), the K DU ports are classified into T DU port groups, and a representative DU port is selected from each of the T DU port groups (S215).

[0140] In S221, the control device 1 sends an instruction to each DU to transmit a downlink reference signal from the representative DU port of each DU port group. Along with this instruction, it transmits information about the resources allocated to each DU for the downlink reference signal. It also transmits information about the resources allocated for measuring the downlink reference signal to the UE 2. In S222, each DU transmits a downlink reference signal from the representative DU port of each DU port group.

[0141] In S223, UE 2 receives the downlink reference signal transmitted from the representative DU port of each DU port group through each UE port, and calculates the propagation characteristics between each UE port and each representative DU port of the DU port group based on the downlink reference signal. The processes in S222 and S223 correspond to the process in step 4 of procedure 2A of the port selection process for reporting. In S224, UE 2 reports the propagation characteristics between each UE port and the representative DU port of each DU port group to the control device 1.

[0142] In S225, the control device 1 classifies the N UE ports of the representative DU port of each DU port group into G UE port groups, and selects a representative UE port from each of the G UE port groups. The process in S225 corresponds to the processes in steps 5 and 6 of procedure 2A of the process for selecting the reporting target ports.

[0143] In S226, the control device 1 determines the combination of each of the T representative DU ports and the representative UE port selected for each representative DU port as the combination of ports to be reported. The process in S226 corresponds to the process in step 7 of procedure 2A of the process for selecting ports to be reported. In S227, the control device 1 notifies UE 2 of the combination of ports to be reported.

[0144] Figure 17 is an example of a flowchart of the process of the control device 1 related to procedure 2A of the process of selecting the reporting target port. The start conditions for the process shown in Figure 17 are the same as those for the process shown in Figure 14. The processes from OP221 to OP224 are the same as those for OP211 to OP214 in Figure 14. The control unit 11 sends an instruction to UE 2 to transmit an uplink reference signal from one UE port (OP221), and when it receives propagation characteristics (channel response) reports from each DU (OP222: YES), it groups the DU ports in each DU (OP223) and selects a representative DU port (OP224).

[0145] In OP225, the control unit 11 sends an instruction to each DU to transmit a downlink reference signal from the representative DU port. The processing of OP225 corresponds, for example, to the processing of S221 in Figure 16. In OP226, the control unit 11 determines whether or not it has received a report of radio wave propagation characteristics (channel response) from UE 2. If a report of radio wave propagation characteristics (channel response) is received from UE 2 (OP226: YES), the process proceeds to OP227. The control unit 11 waits until a report of radio wave propagation characteristics (channel response) is received from UE 2 (OP226: NO). The processing of OP226 corresponds, for example, to the process in S224 in Figure 16 where the control device 1 receives a report from UE 2.

[0146] The processes from OP227 to OP228 are executed for each representative DU port. The representative DU ports targeted by the processes from OP227 to OP228 are designated as representative DU ports #m-k. In OP227, the control unit 11 groups the UE ports for representative DU ports #m-k, classifying N UE ports into G UE port groups. In OP228, the control unit 11 selects one representative UE port from each of the G UE port groups. The processes of OP227 and OP228 correspond, for example, to the process in S225 of Figure 16.

[0147] In OP229, the control unit 11 determines the combinations of each of the T representative DU ports and the representative UE port corresponding to each representative DU port to be reported. The processing in OP229 corresponds, for example, to the processing in S226 of Figure 16. In OP229, the control unit 11 notifies UE 2 of the combinations of ports to be reported. The processing in OP229 corresponds, for example, to the processing in S227 of Figure 16. After that, the processing shown in Figure 8 is completed.

[0148] In a modified version of the second embodiment, in addition to grouping the DU antenna ports, UE ports are also grouped, and the T x G combinations of representative DU ports and representative UE ports are determined to be the subject of reporting. This further reduces the amount of information on radio wave propagation characteristics that UE 2 reports to the control device 1, and further reduces the overhead of the wireless network.

[0149] In a modified version of the second embodiment, UE 2 transmits the uplink reference signal once from one port. Transmitting a signal consumes more power than receiving one. In a modified version of the second embodiment, the number of reference signal transmissions by UE 2 can be reduced, thereby reducing the power consumption of UE 2.

[0150] <Modification 2 of the Second Embodiment> In the second embodiment, the control device 1 instructs the UE 2 to transmit an uplink reference signal, the UE 2 transmits an uplink reference signal, and each DU measures and transmits the propagation characteristics between at least one UE port and each DU port based on the uplink reference signal, thereby receiving the propagation characteristics between each UE port and each DU port from each DU (S212-S214 in Figure 13). Alternatively, the control device 1 may instruct each DU to transmit a downlink reference signal, each DU transmits a downlink reference signal, the UE 2 measures and transmits the propagation characteristics between each UE port and each DU port based on the downlink reference signal, thereby receiving the propagation characteristics between at least one UE port and each DU port from each DU.

[0151] <Third Embodiment> In the third embodiment, UE 2 determines the combination of ports to be reported. In the third embodiment, explanations common to the first and second embodiments are omitted.

[0152] Figures 18A and 18B are diagrams illustrating step 3 of the process for selecting the reporting target port according to the third embodiment. The assumptions for Figures 18A and 18B are the same as those for Figure 2A.

[0153] Figure 18A shows the process performed in step 1 of procedure 1. In step 1 of procedure 3, a downlink reference signal is transmitted from each DU port. UE 2 is the propagation characteristic h^ in the downlink direction from each DU port to each UE port. ＵＥ＝ｎ ＤＵ＝ｍ，ｋ Measure it.

[0154] Figure 18B shows the process performed in step 2 of procedure 3. In step 2 of procedure 3, the propagation characteristics h^ are determined for each of the DU ports #m-k. ＵＥ＝１ ＤＵ＝ｍ，ｋ (1) and h^ ＵＥ＝２ ＤＵ＝ｍ，ｋIf the correlation in (1) is high, UE port #1 and UE port #2 are grouped together. In step 3 of procedure 3, a representative UE port is selected from the UE antenna port group for DU port #m-k. In step 4 of procedure 3, a combination of DU port #m-k and the representative UE port corresponding to DU port #m-k is created.

[0155] When step 3 of the process for selecting the reporting target ports is executed, the combination of UE ports and DU ports to be reported will be the combination of each DU port and the representative UE port corresponding to each DU port. Therefore, the information on propagation characteristics reported from UE 2 to control device 1 will be the number obtained by multiplying the number of UE antenna groups G by the number of DU ports K. Steps 2 to 4 of step 3 may be performed for each DU port.

[0156] Therefore, as a result of the execution of procedure 1 for selecting the reporting target ports, the information regarding propagation characteristics reported from UE 2 to control device 1 is reduced from the number obtained by multiplying the number of UE ports (N=2) by the number of DU ports (K=6) (N×K=2×6=12) to the number obtained by multiplying the number of UE antenna port groups (G=1) by the number of DU ports (K=6) (G×K=1×6=6), in the example shown in Figure 18B.

[0157] Alternatively, step 2 of procedure 3 may be performed for any one DU port, and steps 3 and 4 may be performed for each DU port, with the result of grouping UE ports for that one DU port being applied to the other DU ports.

[0158] Figure 19 shows an example of the sequence in step 3 of the process for selecting the reporting target port. The assumptions for Figure 19 are the same as those for Figure 3. In S311, the control device 1 sends an instruction to each DU to transmit the downlink reference signal from each DU port. Information regarding the resources allocated for measuring the downlink reference signal is also sent to the UE 2.

[0159] In S312, each DU transmits a downlink reference signal from each DU port. In S313, UE 2 receives the downlink reference signals transmitted from each DU port of each DU through each UE port, and calculates the propagation characteristics between each UE port and each DU port based on the downlink reference signals. The processes in S312 and S313 correspond to the process in step 1 of procedure 3 of the process for selecting the reporting target ports.

[0160] In S314, UE 2 groups the UE ports, classifies them into G UE port groups, and selects a representative UE port from each of the G UE port groups for each DU port. The process in S315 corresponds to the processes in steps 2 and 3 of procedure 3 of the process for selecting the ports to be reported.

[0161] In S315, UE 2 determines the combination of each of the K DU ports and the representative UE port selected for each DU port as the combination of ports to be reported. The process in S315 corresponds to the process in step 4 of procedure 3 of the process for selecting the ports to be reported. In S316, UE 2 notifies the control device 1 of the combination of ports to be reported. Subsequently, UE 2 performs measurements for each UE port and transmits information regarding the radio wave propagation characteristics of the combination of ports to be reported to the control device 1 as a result of the measurements.

[0162] In the third embodiment, the functional configuration of UE 2 is the same as in the first embodiment, but the processing of the control unit 21 of UE 2 is different. In the third embodiment, the control unit 21 of UE 2 performs the following in the process of selecting the reporting target ports: grouping of UE ports (steps 2 and 3 of procedure 3, S314 in Figure 19), determining the combination of reporting target ports (step 4 of procedure 3, S315 in Figure 19), and notifying the control device 1 (S316 in Figure 3).

[0163] Figure 20 is an example of a flowchart of the UE2 process related to step 3 of the process for selecting the reporting target port. The process shown in Figure 20 is executed repeatedly, for example, at a predetermined interval.

[0164] In OP311, the control unit 21 determines whether or not it has received information from the control device 1 regarding the resources allocated for measuring the downlink reference signal. Information regarding the resources allocated for measuring the downlink reference signal is transmitted from the control device 1 to the UE 2, for example, when the control device 1 determines that predetermined conditions for initiating coordinated transmission such as CJT or transmission using MIMO have been met, or when it receives instructions from a higher-layer application.

[0165] If information regarding the resource is received from the control device 1 (OP311: YES), the process proceeds to OP312. If information regarding the resource is not received from the control device 1 (OP311: NO), the process shown in Figure 20 ends. When OP311 is affirmative, for example, the process in S311 of Figure 19 is performed.

[0166] In OP312, the control unit 21 receives downlink reference signals from each DU and measures the radio wave propagation characteristics (channel response) for each UE port. The processing in OP312 corresponds, for example, to the processing in S312 and S313 in Figure 19.

[0167] The processing from OP313 to OP315 is performed for each DU port. The DU ports that are subject to processing from OP313 to OP315 are designated as DU ports #m-k. In OP313, the control unit 21 groups the UE ports for DU ports #m-k, classifying N UE ports into G UE port groups and grouping them.

[0168] In OP314, the control unit 21 selects one representative UE port from each of the G UE port groups for DU ports #m-k. The processes in OP313 and OP314 correspond, for example, to the process in S314 of Figure 19.

[0169] In OP315, the control unit 21 determines the combination of the representative UE port selected in OP314 and DU port #m-k to be reported. The processing in OP315 corresponds, for example, to the processing in S315 in Figure 19. Once the processing from OP313 to OP315 is executed for each DP port, the combination of each DU port and the representative UE port corresponding to each DU port is determined as the combination to be reported.

[0170] In OP316, the control unit 21 notifies the control device 1 of the combination of ports to be reported. The processing in OP316 corresponds, for example, to the processing in S316 in Figure 19. After that, the processing shown in Figure 20 is completed.

[0171] Note that the process shown in Figure 20 is an example, and the processing of UE 2 related to step 3 of the process for selecting the reporting target ports is not limited to the process shown in Figure 20. If the result of grouping UE ports for one DU port is applicable to other DU ports, the UE port grouping process of OP 313 is executed for that one DU port, and the representative UE port selection process of OP 314 and the determination of the reporting target combination of OP 315 are executed for each DU port. Furthermore, if the result of grouping UE ports and the representative UE port for one DU port are applicable to other DU ports, the UE port grouping process of OP 313 and the representative UE port selection process of OP 314 are executed for that one DU port, and the determination of the reporting target combination of OP 315 is executed for each DU port.

[0172] In the third embodiment, UE 2 groups the UE antenna ports and determines the combination of ports to be reported. In step 3 of the port selection process according to the third embodiment, UE 2 receives the downlink reference signal without transmitting the uplink reference signal, thus further reducing the power consumption of UE 2.

[0173] Furthermore, if the grouping results of UE ports for one DU port and the representative UE port are also applied to other DU ports, the downlink reference signal in step 1 of procedure 3 (S312 in Figures 18A and 19) may be transmitted from only one of the K DU ports. The one DU port from which the downlink reference signal is transmitted may be randomly selected by, for example, the control device 1 and notified to UE 2. This further reduces the number of downlink reference signals transmitted in step 3 of the reporting port selection process.

[0174] <Modification 1 of the Third Embodiment> Figure 21 is a diagram showing the process of step 3A of the reporting target port selection process according to Modification 1 of the Third Embodiment. In Modification 1 of the Third Embodiment, in addition to step 3 of the reporting target port selection process according to the Third Embodiment, K DU ports are also grouped. Figure 21 will be explained assuming the communication system 100 shown in Figure 1, similar to Figures 2A to 2C. Steps 1 to 4 of step 3A of the reporting target port selection process are the same as steps 1 to 4 of step 3.

[0175] In step 5 of procedure 3A, the DU ports are grouped for each DU#m. In the example shown in Figure 21, the propagation characteristics h^ are grouped for each of DU#1 to DU#3. ＵＥ＝１ ＤＵ＝ｍ，１ (1) and h^ ＵＥ＝１ ＤＵ＝ｍ，２ (1), and propagation characteristics h^ ＵＥ＝２ ＤＵ＝ｍ，１ (2) and h^ ＵＥ＝２ ＤＵ＝ｍ，２ (2) If there is a high correlation between each of the above, DU port #m-1 and DU port #m-2 are grouped together. When step 5 of procedure 3A is performed, T DU port groups are formed from K DU ports.

[0176] In the example shown in Figure 21, four DU port groups are formed: a group including DU port #1-1 and DU port #1-2, a group including DU port #2-1 and DU port #2-2, a group including DU port #3-1, and a group including DU port #3-2. In the example shown in Figure 21, the number of DU port groups T = 4. Note that the propagation characteristics h^ ＵＥ＝１ ＤＵ＝ｍ，１ (1) and h^ ＵＥ＝１ ＤＵ＝ｍ，２ (1), and propagation characteristics h^ ＵＥ＝２ ＤＵ＝ｍ，１ (1) and h^ ＵＥ＝２ ＤＵ＝ｍ，２(1) Instead of determining the correlation for both, the correlation can be determined for either one, and DU port #m-1 and DU port #m-2 can be grouped. Alternatively, the grouping of DU ports can be performed for all K DU ports, rather than for each individual DU.

[0177] In step 6 of procedure 3A, one representative DU port is selected for each of the T DU antenna port groups. In the example shown in Figure 21, DU port #1-2, DU port #2-2, DU port #3-1, and DU port #3-2 are selected as representative DU ports.

[0178] In step 7 of procedure 3A, a combination is created between the representative DU port of each DU antenna port group and the representative UE port corresponding to that representative DU port. Therefore, the information regarding propagation characteristics reported from UE 2 to control device 1 will be the product of the number of UE antenna groups G and the number of DU antenna port groups T.

[0179] Therefore, as a result of the execution of procedure 3A for selecting the reporting target ports, the information regarding propagation characteristics reported from UE 2 to control device 1 is reduced from the number obtained by multiplying the number of UE ports (N=2) by the number of DU ports (K=6) (N×K=2×6=12) to the number obtained by multiplying the number of UE antenna port groups (G=1) by the number of DU antenna port groups (T=4) (G×T=1×4=4), in the example shown in Figure 21.

[0180] Figure 22 shows an example of the sequence in step 3A of the process for selecting the reporting target ports. The assumptions in Figure 22 are the same as in Figure 3. Steps S311 to S314 are the same as in Figure 19. Based on the downlink reference signals from each DU (S311, S312), the propagation characteristics between each UE port and each DU port are acquired for each UE port (S313), the N UE ports are classified into G UE port groups, and a representative UE port is selected from each of the G UE port groups (S314).

[0181] In S321, UE 2 groups the DU ports for each DU or for all K DU ports, classifies the K DU ports into T DU port groups, and selects a representative DU port from each of the T DU port groups. The process in S321 corresponds to the processes in steps 5 and 6 of procedure 3A of the process for selecting the ports to be reported.

[0182] In S322, UE 2 determines the combination of each of the T representative DU ports and the representative UE port corresponding to each representative DU port as the combination of ports to be reported. The process in S322 corresponds to the process in step 7 of procedure 3A of the port selection process to be reported. In S323, UE 2 notifies the control device 1 of the combination of ports to be reported.

[0183] Figure 23 is an example of a flowchart of the UE 2 process related to step 3A of the process for selecting the reporting target port. The start conditions for the process shown in Figure 23 are the same as those for the process shown in Figure 20. The processes from OP321 to OP324 are the same as those from OP311 to OP314 in Figure 20. The control unit 21 of UE 2 receives information from the control device 1 regarding the resources allocated for measuring the downlink reference signal (OP311), receives the downlink reference signal from each DU, measures the radio wave propagation characteristics (channel response) for each UE port (OP312), groups the UE ports for each DU port (OP323), and selects a representative UE port (OP324).

[0184] In OP325, the control unit 21 groups the DU ports, classifying the K DU ports into T DU port groups and grouping them. Alternatively, instead of grouping each DU individually, it may search for two or more DU ports with high correlation in propagation characteristics across all DU ports.

[0185] In OP326, the control unit 21 selects one representative DU port from each of the T DU port groups. The processes of OP325 and OP326 correspond, for example, to the process in S321 of Figure 22.

[0186] In OP327, the control unit 21 determines that each of the T representative DU ports selected in OP326 and the representative UE port corresponding to that representative DU port will be reported. The processing in OP327 corresponds, for example, to the processing in S322 of Figure 22. In OP328, the control unit 21 notifies the control device 1 of the combinations of ports to be reported. The processing in OP328 corresponds, for example, to the processing in S323 of Figure 22. After that, the processing shown in Figure 23 is completed. Note that the processing shown in Figure 22 is just one example, and the processing of UE 2 related to procedure 3A of the processing of selecting ports to be reported is not limited to the processing shown in Figure 22.

[0187] In the third embodiment, modification 1, UE 2 performs grouping of DU ports in addition to grouping of UE antenna ports, and T x G combinations of representative DU ports and representative UE ports are determined to be reported. This further reduces the amount of information on radio wave propagation characteristics that UE 2 reports to the control device 1, and further reduces the overhead of the wireless network.

[0188] <Modification 2 of the Third Embodiment> In the third embodiment, UE 2 groups the UE ports (for example, S314 in Figure 19), but in Modification 2 of the third embodiment, instead, UE 2 may group the DU ports.

[0189] More specifically, UE 2 measures the propagation characteristics of each UE port based on the downlink reference signal from each DU port (for example, S313 in Figure 19, OP312 in Figure 20), and then, for each DU or for K DUs, groups together two or more DU ports with high correlation of propagation characteristics, classifying the K DU ports into T DU port groups. UE 2 selects a representative DU port for each of the T DU port groups. The selection criteria for the representative DU port are the same as those for the representative UE port. UE 2 determines T × N combinations of each of the T representative DU ports and each of the N UE ports as the combinations to be reported. This reduces the amount of information on radio wave propagation characteristics that UE 2 reports to the control device 1, thereby reducing the overhead of the wireless network.

[0190] <Modification 3 of the Third Embodiment> In Modification 3 of the Third Embodiment, following the grouping of DU ports by UE 2 in Modification 2 of the Third Embodiment, UE ports are grouped by UE 2. In Modification 3 of the Third Embodiment, for example, in the flowchart of Figure 23 in Modification 1 of the Third Embodiment, the execution order of the grouping of UE ports OP323 and OP324 and the grouping of DU ports OP325 and OP326 is reversed, and after the grouping of DU ports OP325 and OP326, the grouping of UE ports OP323 and OP324 is performed for each representative DU port of each DU port group.

[0191] <Other Embodiments> The embodiments described above are merely examples, and this disclosure may be modified as appropriate without departing from its essence.

[0192] In the first and second embodiments, the control device 1 performs the grouping of UE ports or DU ports, but each distributed base station may perform these actions. The distributed base station includes, either within or in addition to the DU, a CPU, main memory, external memory, a communication device which is an interface with the control device, and an antenna.

[0193] For example, in the first embodiment, each distributed base station measures the propagation characteristics between each DU port and each UE port based on the uplink reference signal from each UE port of UE 2 (S113 in Figure 3), then groups the UE ports and selects a representative UE port for each of the one or more DU ports provided at each distributed base station (corresponding to the processing in S115 performed by the control device in Figure 3), notifies the control device 1 of the results, and the control device 1 may determine the combination to be reported based on the results of the UE port grouping and representative UE port selection from each distributed base station (S116 in Figure 3). Furthermore, each distributed base station may determine the combination to be reported for the DU ports provided at its own station (corresponding to the processing in S116 performed by the control device 1 in Figure 3), and notify the control device 1.

[0194] For example, in a modified version of the first embodiment, each distributed base station measures the propagation characteristics between each DU port and each UE port based on the uplink reference signal from each UE port of UE 2 (S113 in Figure 10). Then, for each of the one or more DU ports provided at each distributed base station, it performs grouping of UE ports and selection of a representative UE port (corresponding to S115 performed by the control device in Figure 10), and grouping of DU ports and selection of a representative DU port (corresponding to the processing in S121 performed by the control device 1 in Figure 10). The distributed base station then notifies the control device 1 of the results, and the control device 1 may determine the combination to be reported based on the received results (S122 in Figure 10). Furthermore, each distributed base station may determine the combination to be reported for the DU ports provided at its own station (corresponding to the processing in S122 performed by the control device 1 in Figure 10) and notify the control device 1.

[0195] For example, in the second embodiment, each distributed base station measures the propagation characteristics between each DU port and the one UE port based on the uplink reference signal from one UE port of UE 2 (S213 in Figure 13), then groups the UE ports and selects a representative UE port for each of the one or more DU ports provided at each distributed base station (corresponding to the processing in S215 performed by the control device in Figure 13), notifies the control device 1 of the results, and the control device 1 may determine the combination to be reported based on the results of the UE port grouping and representative UE port selection from each distributed base station (S216 in Figure 13). Furthermore, each distributed base station may determine the combination to be reported for the DU ports provided at its own station (corresponding to S216 performed by the control device 1 in Figure 31) and notify the control device 1.

[0196] In the first to third embodiments, the description was based on the premise that CJT is performed in a distributed MIMO system. However, it is not limited to this, and the reporting port selection process described in the first to third 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, distributed 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 reporting port selection process described in the first to third embodiments can also be applied to systems in which at least multiple antenna ports are provided on the base station side, and a technology is performed to improve the communication quality of the UE through the interaction of signals transmitted from the multiple antenna ports to the UE.

[0197] Furthermore, the processes and means described in this disclosure can be freely combined and implemented, provided that no technical inconsistencies arise.

[0198] 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.

[0199] 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.

[0200] 1...Control unit 2...UE 11...Control unit 21...Control unit 22...Measurement unit 100...Communication system 101...CPU 102...Main memory 103...External memory 104...Communication device

Claims

1. For at least one of the following: one or more base stations having one or more antenna ports, or a user device (UE) that receives signals simultaneously transmitted from the one or more antenna ports of the one or more base stations through one or more antenna ports, the one or more antenna ports are classified into one or more antenna port groups by grouping two or more antenna ports whose correlation value for radio wave propagation characteristics is equal to or greater than a first value; and the antenna port combination between the one or more base stations and the UE, for which the UE reports information regarding radio wave propagation characteristics to the network, is a combination of one or more representative ports selected one by one from each of the one or more antenna port groups for either the one or more base stations or the UE, and one or more antenna ports provided on the other of the one or more base stations or the UE, or An information processing device comprising a control unit that determines a combination of one or more representative ports selected one by one from each of the one or more antenna port groups for the one or more base stations and one or more representative ports selected one by one from each of the one or more antenna port groups for the UE, and performs the following:

2. A UE having N second antenna ports that receive signals simultaneously transmitted from a total of K first antenna ports of one or more base stations, the UE comprises a control unit that performs the following: classifying the N second antenna ports into G second antenna port groups, each containing one or more second antenna ports, by grouping two or more second antenna ports whose correlation value with respect to one of the K first antenna ports on the base station side is equal to or greater than a first value; and deciding whether the UE should report information regarding radio wave propagation characteristics to the network for each of the K first antenna ports and each of the G second antenna ports selected as representatives from each of the G second antenna port groups, for a total of K × G one-to-one combinations of the first antenna ports on the base station side and the second antenna ports provided in the UE, wherein K is a positive integer of 1 or more, and N is a positive integer of 2 or more. G is an integer that takes a value between 1 and N, and is an information processing device.

3. The control unit further classifies the K first antenna ports on the base station side into T first antenna port groups, each containing one or more first antenna ports, by grouping two or more first antenna ports whose correlation value with respect to one of the N second antenna ports provided in the UE is equal to or greater than the second value; and decides to perform the report for T × G combinations of each of the T first antenna ports selected as representatives from each of the T first antenna port groups and each of the G second antenna ports, wherein K is a positive integer of 2 or more, and T is an integer whose value is in the range of 1 or more and less than or equal to K.

4. The information processing apparatus according to claim 2, wherein the control unit further performs the following: for each of the G second antenna port groups in the UE that includes two or more second antenna ports, the control unit selects as a representative second antenna port from among the two or more second antenna ports included in the second antenna port group that has the highest quality of received signals transmitted and received between it and the one first antenna port on the base station side.

5. The information processing apparatus according to claim 2, wherein the control unit further performs the following: for each of the K first antenna ports on the base station side, select one representative second antenna port from each of the G second antenna port groups.

6. The information processing apparatus according to claim 3, wherein the control unit further performs the following: for each of the T first antenna ports selected as representatives of each of the T first antenna port groups on the base station side, select one second antenna port from each of the G second antenna port groups as a representative.

7. The information processing apparatus according to claim 3, further comprising the control unit selecting, for each of the T first antenna port groups on the base station side that includes two or more first antenna ports, the first antenna port that has the highest quality of received signals transmitted and received between the first antenna port and the one second antenna port provided on the UE, as a representative of the two or more first antenna ports included in the first antenna port group.

8. The information processing apparatus according to claim 2, further comprising: the control unit notifying the UE of one or more combinations for which the reporting has been decided.

9. The information processing apparatus according to claim 2, further comprising: the control unit instructing the UE to transmit an uplink measurement signal from each of the N second antenna ports; and receiving from one or more base stations the radio wave propagation characteristics between each of the N second antenna ports provided in the UE and each of the K first antenna ports on the base station side, which are obtained based on the uplink measurement signals transmitted from each of the N second antenna ports provided in the UE.

10. The information processing apparatus according to claim 2, further comprising: the control unit instructing one or more base stations to transmit a downlink measurement signal from each of the K first antenna ports; and receiving the radio wave propagation characteristics between each of the K first antenna ports on the base station side and each of the at least one second antenna port provided on the UE, based on the downlink measurement signals transmitted from each of the K first antenna ports on the base station side.

11. The information processing device is the UE, and the control unit further performs the following: acquiring the radio wave propagation characteristics between each of the K first antenna ports on the base station side and each of the N second antenna ports provided in the UE, based on the downlink measurement signals transmitted from each of the K first antenna ports on the base station side.

12. The information processing apparatus according to claim 11, further comprising: the control unit notifying the network of one or more combinations for which the reporting has been decided.

13. A computer, in a UE having N second antenna ports that receive signals simultaneously transmitted from a total of K first antenna ports of one or more base stations, classifies the N second antenna ports into G second antenna port groups, each containing one or more second antenna ports, by grouping two or more second antenna ports whose correlation value with respect to one of the K first antenna ports on the base station side is greater than or equal to a first value; and decides to have the UE report information regarding radio wave propagation characteristics to the network for K × G one-to-one combinations of the first antenna ports on the base station side and the second antenna ports provided in the UE, where K is a positive integer of 1 or more, and N is a positive integer of 2 or more. G is an integer that takes a value between 1 and N, and the method is as follows.

14. The method according to claim 13, further comprising: the computer classifying the K first antenna ports on the base station side into T first antenna port groups, each containing one or more first antenna ports, by grouping two or more first antenna ports whose correlation value with respect to one of the N second antenna ports provided in the UE is equal to or greater than a second value; the computer then decides to perform the report for T × G combinations of each of the T first antenna ports, one of which is selected as a representative from each of the T first antenna port groups, and each of the G second antenna ports, wherein K is a positive integer of 2 or more, and T is an integer whose value is in the range of 1 or more and K or less.

15. The method according to claim 13, further comprising the computer selecting, for each of the G second antenna port groups in the UE that includes two or more second antenna ports, the second antenna port that has the highest quality of received signals transmitted and received between the two or more second antenna ports included in the second antenna port group and the one first antenna port on the base station side, as a representative of the G second antenna port groups.

16. The method according to claim 13, further comprising the computer selecting one representative second antenna port from each of the G second antenna port groups for each of the K first antenna ports on the base station side.

17. The method according to claim 14, further comprising the computer selecting, for each of the T first antenna ports selected as representatives of each of the T first antenna port groups on the base station side, one second antenna port from each of the G second antenna port groups as a representative.

18. The method according to claim 13, further comprising: the computer instructing the UE to transmit an uplink measurement signal from each of the N second antenna ports; and the one or more base stations receiving the radio wave propagation characteristics between each of the N second antenna ports provided in the UE and each of the K first antenna ports on the base station side, obtained based on the uplink measurement signals transmitted from each of the N second antenna ports provided in the UE.

19. The method according to claim 13, further comprising: the computer instructing one or more base stations to transmit a downlink measurement signal from each of the K first antenna ports; and the UE receiving the radio wave propagation characteristics between each of the K first antenna ports on the base station side and each of the N second antenna ports provided on the UE, based on the downlink measurement signals transmitted from each of the K first antenna ports on the base station side.

20. The method according to claim 13, wherein the computer is provided in the UE, and the computer acquires the radio wave propagation characteristics between each of the K first antenna ports on the base station side and each of the N second antenna ports provided in the UE, based on the downlink measurement signals transmitted from each of the K first antenna ports on the base station side.

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