Base station and communication method

Abstract

To provide a base station capable of improving the efficiency of reception quality measurement, a terminal, and a communication method.SOLUTION: A base station 100 includes: a communication circuit 102 that transmits or receives a reference signal in multiple bands using some of the multiple antennas; and a control circuit 101 that determines which of multiple bands should be assigned to the terminal based on the measurement result using the reference signal.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present disclosure relates to a base station, a terminal, and a communication method. [Background technology]

[0002] As mobile traffic increases, methods to increase the system capacity are being considered. One method to achieve this is a distributed Multiple-Input Multiple-Output (MIMO) cooperative transmission system. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Dai Kimura, Hiroyuki Seki, “Inter-cell interference control (ICIC) technology” FUJITSU. 62, 4 (07 2011) Summary of the Invention [Problem to be solved by the invention]

[0004] In a distributed MIMO cooperative transmission system, in order to increase the capacity of the system, it is expected that, for example, interference within a cell or between cells should be reduced as much as possible. For example, reception quality measurement is used to reduce interference. However, a method for measuring reception quality in a wireless communication system such as a distributed MIMO cooperative transmission system has not been fully studied.

[0005] Non-limiting embodiments of the present disclosure contribute to providing a base station, a terminal, and a communication method that can improve the efficiency of reception quality measurement. [Means for solving the problem]

[0006] A base station according to one embodiment of the present disclosure includes a communication circuit that transmits or receives reference signals in multiple bands using some of multiple antennas, and a control circuit that determines which of the multiple bands to assign to a terminal based on a result of a measurement using the reference signals.

[0007] These comprehensive or specific aspects may be realized as a system, an apparatus, a method, an integrated circuit, a computer program, or a recording medium, or may be realized as any combination of a system, an apparatus, a method, an integrated circuit, a computer program, and a recording medium. Effect of the Invention

[0008] According to an embodiment of the present disclosure, it is possible to improve the efficiency of reception quality measurement in a wireless communication system.

[0009] Further advantages and benefits of an embodiment of the present disclosure will become apparent from the specification and drawings. Such advantages and / or benefits may be provided by some of the embodiments and features described in the specification and drawings, respectively, but not necessarily all of them may be provided to obtain one or more identical features. [Brief description of the drawings]

[0010] [Figure 1] A diagram showing an example of a distributed MIMO cooperative transmission system. [Diagram 2] FIG. 1 is a diagram showing an example of processing in a distributed MIMO cooperative transmission system. [Diagram 3] A diagram showing an example of scheduling [Figure 4] Diagram showing an example of Fractional Frequency Reuse (FFR) [Diagram 5] FIG. 1 is a block diagram showing a configuration example of a base station according to a first embodiment; [Figure 6] FIG. 1 is a block diagram showing a configuration example of a terminal according to a first embodiment; [Figure 7] A sequence diagram showing an example of the operation of a base station and a terminal according to the first embodiment. [Figure 8] FIG. 1 shows an example of a frame format according to the first embodiment. [Figure 9] FIG. 1 is a diagram showing an example of resource allocation for reference signals according to the first embodiment; [Figure 10] FIG. 1 is a diagram showing an example of resource allocation for reference signals according to the first embodiment; [Figure 11] FIG. 1 is a diagram showing an example of resource allocation for reference signals according to the first embodiment; [Figure 12] A sequence diagram showing an example of the operation of a base station and a terminal according to the second embodiment. [Figure 13] FIG. 13 is a diagram showing an example of resource allocation for reference signals according to the second embodiment; [Figure 14] A sequence diagram showing an example of the operation of a base station and a terminal according to a third embodiment. [Figure 15] A sequence diagram showing an example of the operation of a base station and a terminal according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings.

[0012] FIG. 1 is a diagram illustrating an example of the configuration of a distributed MIMO cooperative transmission system.

[0013] As shown in FIG. 1, the distributed MIMO cooperative transmission system may have a distributed antenna configuration including multiple antennas (e.g., referred to as "distributed antennas") distributed within a cell, and a base station (e.g., also referred to as a Base Station (BS), control station, eNB, or gNB) centrally controls the distributed antennas via a fronthaul.

[0014] Also, as shown in FIG. 1, one or more clusters (or small cells) each composed of multiple distributed antennas located near a terminal (e.g., User Equipment: UE) may be formed within a cell. For example, MIMO cooperative transmission may be performed individually for each cluster. Note that a cell formed by a base station may be called a macrocell, for example, in contrast to a small cell.

[0015] In a distributed MIMO cooperative transmission system, for example, interference between clusters (hereinafter referred to as "inter-cluster interference") or interference with neighboring cells (hereinafter referred to as "inter-cell interference") may occur. To address these interferences, for example, there is a method of classifying terminals into "intra-cell terminals" and "cell edge terminals" and reducing interference for each terminal by intra-cell interference control and inter-cell interference control, thereby increasing the system capacity.

[0016] The intra-cell terminal may be, for example, a cell located relatively close to the cell center where the interference from adjacent cells is small (for example, less than a threshold value), and the cell edge terminal may be, for example, a cell where the interference from adjacent cells is large (for example, greater than or equal to a threshold value).

[0017] FIG. 2 is a diagram showing an example of processing in a distributed MIMO cooperative transmission system using the above-described interference control.

[0018] 2, the terminal measures, for example, an interference level (for example, interference power) from another cell (S11). Information on the interference level may be transmitted (feedback) from the terminal to the base station, for example.

[0019] The base station classifies the terminal into either an "intra-cell terminal" or a "cell edge terminal" based on, for example, an interference level at the terminal (S12). For example, a terminal whose interference level is less than a threshold may be classified as an intra-cell terminal, and a terminal whose interference level is equal to or greater than the threshold may be classified as a cell edge terminal.

[0020] The base station may perform intra-cell interference control for the intra-cell terminal (S13). In the intra-cell interference control, the base station may perform control to form a cluster and reduce interference between clusters by linking distributed antennas located near the intra-cell terminal based on the location information of the intra-cell terminal. In addition, the base station may perform layering to assign clusters with large inter-cluster interference to another scheduling layer in order to reduce inter-cluster interference, and antenna selection to select nearby antennas based on the location information of the terminal, for example, in the intra-cell interference control.

[0021] Furthermore, the base station may perform inter-cell interference control for, for example, cell edge terminals (S14). In the inter-cell interference control, the base station may perform control to reduce inter-cell interference by, for example, allocating multiple bands (hereinafter referred to as "partial bands") obtained by dividing a communication band (for example, at least a part of a system band) so as to be orthogonal between adjacent cells based on reception quality. Note that the base station may form one cluster for cell edge terminals as well (in other words, select a distributed antenna near the terminal to form a small cell) in the same way as for in-cell terminals.

[0022] The process of S13 and the process of S14 may be performed in parallel, or one of the processes may be performed sequentially after the other process.

[0023] The base station performs, for example, scheduling for terminals (for example, allocation of radio resources) (S15). FIG. 3 is a diagram showing an example of scheduling for intra-cell terminals (also referred to as intra-cell users, for example) and cell-edge terminals (also referred to as cell-edge users, for example). As shown in FIG. 3, the base station may perform scheduling by dividing radio resources between intra-cell terminals and cell-edge terminals (time division in FIG. 3). As shown in FIG. 3, partial band W 1 , W 2 and W 3 Radio resources are allocated in the communication band including 1, W 2 and W 3 Radio resources may be allocated in either one of the above.

[0024] In Fig. 2, the base station and the terminal perform distributed MIMO cooperative transmission (e.g., transmission and reception) based on, for example, the scheduling result (S16). For example, the base station and the terminal may perform multi-user MIMO transmission (MU-MIMO) on a cluster basis using a transmission weight and a reception weight based on the reception quality. Note that the channel estimation value obtained in the distributed MIMO cooperative transmission may be used (e.g., fed back) for other processing such as interference level measurement (e.g., processing of S11) and scheduling (e.g., processing of S15).

[0025] In each process of the distributed MIMO cooperative transmission system described above, reception quality may be measured. However, in a system in which multiple distributed antennas are arranged, a method of assigning a reference signal for measuring reception quality to each distributed antenna has not been fully considered.

[0026] For example, in reception quality measurement at a base station having multiple (e.g., 128) distributed antennas within one cell, if orthogonal reference signals are assigned between the distributed antennas to measure the reception quality of each distributed antenna, the more distributed antennas there are, the more radio resources are used for the reference signals, which results in larger reference signal overhead and reduced utilization efficiency of radio resources.

[0027] One method of inter-cell interference control is fractional frequency reuse (FFR) (see, for example, Non-Patent Document 1). FIG. 4 is a diagram showing an example of FFR. As shown in FIG. 4, in FFR, each cell is divided into a central region of the cell (hereinafter referred to as an "intra-cell region") and an edge region (hereinafter referred to as a "cell edge region"). In the intra-cell region of each cell, multiple bands (for example, W 1 +W 2 +W3 ) is assigned to each cell, and in the cell edge region, a partial band (e.g., W 1 , W 2 , W 3 FFR allows different bands to be allocated to the cell edge regions of adjacent cells, reducing interference.

[0028] In FFR, in order to allocate different partial bands between adjacent cells, for example, the coverage of each cell may be surveyed in advance before operation, and then the partial bands may be allocated. However, this method is likely to complicate operation, since further surveys must be performed when, for example, the network configuration is changed (for example, a base station is added or removed).

[0029] Alternatively, the base stations (or cells) may exchange (e.g., periodically exchange) individual interference information for partial bands during operation, and a partial band with lower interference between adjacent cells may be selected. However, this method may increase traffic between base stations (or cells) during operation.

[0030] In this way, from the viewpoint of network scalability and traffic, it is desirable for each base station to autonomously select a partial band. In order for each base station to autonomously select a partial band, for example, it is desirable for the base station to acquire interference information by itself without relying on information from surrounding base stations. Furthermore, in a distributed antenna configuration, there is room for consideration regarding a method of transmitting and receiving a reference signal in a plurality of distributed antennas for measuring interference in a partial band.

[0031] In one embodiment of the present disclosure, a method for improving the efficiency of reception quality measurements in a distributed antenna configuration is described.

[0032] (Embodiment 1) [Wireless communication system configuration] The wireless communication system according to this embodiment includes at least base station 100 and terminal 200, for example.

[0033] FIG. 5 is a block diagram showing an example of the configuration of base station 100 according to the present embodiment.

[0034] The base station 100 shown in FIG. 5 may include, for example, a control unit 101 (corresponding to, for example, a control circuit), a communication unit 102 (corresponding to, for example, a communication circuit), and a measurement unit 103.

[0035] Note that each component of base station 100 shown in Fig. 5 may be functionally distributed to the base station and distributed antenna shown in Fig. 1. For example, control unit 101 shown in Fig. 5 corresponds to the "base station" performing centralized control in Fig. 1, and communication unit 102 may include multiple distributed antennas shown in Fig. 1. Also, for example, measurement unit 103 shown in Fig. 5 may be provided in the "base station" shown in Fig. 1 or in each distributed antenna. Alternatively, the configuration of base station 100 shown in Fig. 5 may be provided in, for example, the distributed antenna shown in Fig. 1.

[0036] The control unit 101 may, for example, perform scheduling for the terminal 200. For example, the control unit 101 may determine a communication band (for example, a partial band) that the base station 100 (for example, a cell corresponding to the base station 100) uses for communication with the terminal 200 within the cell. Furthermore, the control unit 101 may, for example, allocate radio resources to the terminal 200 in the band used by the base station 100.

[0037] Furthermore, the control unit 101 may determine, for example, information on configuration of a reference signal for the terminal 200. The information on configuration of a reference signal may include, for example, information on resources to which downlink reference signals are allocated.

[0038] Also, the control unit 101 may classify the terminal 200 into, for example, an intra-cell terminal or a cell edge terminal. Also, the control unit 101 may perform interference control (for example, either intra-cell interference control or inter-cell interference control) for the terminal 200 according to the classification of the terminal 200.

[0039] Furthermore, the control unit 101 may control, for example, cooperative transmission and reception control (for example, MIMO cooperative transmission). For example, the control unit 101 may control the setting of a cluster for the terminal 200 and the generation of downlink and uplink transmission and reception weights.

[0040] The control unit 101 may control the above-mentioned processing based on, for example, information input from the communication unit 102 (for example, information fed back from the terminal 200) and information on the reception quality of each terminal 200 input from the measurement unit 103. For example, in this embodiment, the control unit 101 may perform inter-cell interference control based on interference power or a signal to interference ratio (SIR) included in the information on the reception quality fed back from the terminal 200. Also, for example, in this embodiment, the control unit 101 may generate a downlink transmission weight based on interference power or a channel estimation value included in the information on the reception quality fed back from the terminal 200. Also, the control unit 101 may output the control information obtained by the above-mentioned processing to the communication unit 102.

[0041] The communication unit 102 may, for example, perform wireless communication with the terminal 200. The communication unit 102 may, for example, transmit control information input from the control unit 101 to the terminal 200. In addition, the communication unit 102 may, for example, receive a signal transmitted from the terminal 200 and output the received signal to the control unit 101 and the measurement unit 103.

[0042] The measurement unit 103 may measure (or estimate channel) reception quality (e.g., interference power or SIR) between the base station 100 and the terminal 200, for example, based on a reference signal included in a signal input from the communication unit 102. In this embodiment, for example, the measurement unit 103 may measure reception quality (e.g., interference power or channel estimation value) used for generating uplink reception weights, based on a reference signal transmitted from the terminal 200. The measurement unit 103 may output information on the measured reception quality to the control unit 101, for example.

[0043] FIG. 6 is a block diagram showing an example of the configuration of terminal 200 according to this embodiment.

[0044] The terminal 200 shown in FIG. 6 may include, for example, a control unit 201, a communication unit 202, and a measurement unit 203.

[0045] The control unit 201 may control wireless communication based on, for example, control information input from the communication unit 202. For example, the control unit 201 may determine resources for data to be assigned to the terminal 200 based on the control information. Also, the control unit 201 may determine resources for a reference signal configured for the terminal 200 based on, for example, the control information.

[0046] Furthermore, the control unit 201 may control, for example, cooperative transmission and reception (for example, MIMO cooperative transmission). For example, the control unit 201 may control generation of transmission and reception weights for downlink and uplink based on information on reception quality input from the measurement unit 203.

[0047] The control unit 201 outputs to the communication unit 202, for example, information on reception quality such as interference power or a channel estimation value (for example, information on transmission and reception weights) input from the measurement unit 203.

[0048] The communication unit 202 may perform wireless communication with the base station 100, for example. For example, the communication unit 202 may transmit control information input from the control unit 201 to the base station 100. For example, the control information related to interference control may include information on reception quality such as interference power or SIR. Furthermore, for example, the control information related to control of cooperative transmission and reception may include information on reception quality such as interference power or a channel estimation value. Furthermore, the communication unit 202 may receive a signal transmitted from the base station 100, and output the received signal to the control unit 201 and the measurement unit 203.

[0049] The measurement unit 203 may measure (or estimate a channel) a reception quality (e.g., interference power or SIR) between the base station 100 and the terminal 200 based on, for example, a reference signal included in a signal input from the communication unit 202. In this embodiment, for example, the measurement unit 203 may measure a reception quality used for inter-cell interference control and a reception quality used for generating a downlink transmission weight. The measurement unit 203 may output information related to the measured reception quality to the control unit 201, for example.

[0050] [Example of Operation of Base Station 100 and Terminal 200] An example of the operation of base station 100 and terminal 200 described above will be explained.

[0051] FIG. 7 is a sequence diagram showing an example of the operation of base station 100 (for example, a distributed antenna) and terminal 200. As shown in FIG.

[0052] 7, base station 100 transmits, for example, information related to the configuration of a downlink reference signal (DL-RS) to terminal 200 (S101). The DL-RS may be, for example, a Channel State Information Reference Signal (CSI-RS) defined in the 3GPP specifications. Configuration information of the DL-RS may be notified (or configured) from base station 100 to terminal 200 by, for example, higher layer signaling (also called Radio Resource Control (RRC) signaling or higher layer parameters).

[0053] The base station 100 transmits, for example, a DL-RS (for example, a CSI-RS) to the terminal 200 (S102-1). The terminal 200 may receive, for example, a DL-RS (for example, a CSI-RS) from a base station of another cell (for example, a distributed antenna) in addition to the DL-RS from the base station 100 (S102-2).

[0054] Terminal 200 measures, for example, a downlink interference level (for example, interference power) (S103). For example, terminal 200 may measure the interference power based on the CSI-RS transmitted from each cell.

[0055] Fig. 8 is a diagram showing an example of a frame format used in base station 100 and terminal 200. As shown in Fig. 8, resources related to CSI-RS allocation may include, for example, resources to which no transmission power is allocated and CSI-RS is muted (for example, referred to as "Zero Power CSI-RS (ZP-CSI-RS)" or "ZP-CSI-RS resources"), and resources to which transmission power is allocated (for example, referred to as "Non-Zero Power CSI-RS (NZP-CSI-RS)" or "NZP-CSI-RS resources").

[0056] Fig. 9 is a diagram showing an example of CSI-RS resource allocation using the frame format shown in Fig. 8. For example, as shown in Fig. 9, the positions of ZP-CSI-RS allocated resources (for example, the positions of resource elements (REs)) may be different between adjacent cells. Also, for example, as shown in Fig. 9, the positions of ZP-CSI-RS resources in each cell may be set to the same positions as the positions of NZP-CSI-RS resources in other cells. Also, for example, ZP-CSI-RS resources and NZP-CSI-RS resources may be allocated in common to multiple distributed antennas in the same cell.

[0057] Terminal 200 may measure interference power from other cells, for example, in the ZP-CSI-RS resource of each cell (in other words, the NZP-CSI-RS resource of other cells). As an example, terminal 200 in cell #1 shown in FIG. 9 may measure interference power from other cells (for example, cell #2 and cell #3) in the ZP-CSI-RS resource of cell #1. By measuring the interference power in the ZP-CSI-RS resource of each cell, the measurement accuracy of the interference power in terminal 200 can be improved.

[0058] In FIG. 7, terminal 200 notifies base station 100 of information on the measured interference power (for example, DL interference power) (S104).

[0059] The base station 100 classifies (for example, also referred to as user classification) into intra-cell terminals and cell-edge terminals (S105). The base station 100 may perform user classification based on, for example, information on interference power notified from each terminal 200. For example, the base station 100 may classify a specified number of terminals 200 with the highest interference power (in other words, a specified percentage of the highest) as cell-edge terminals, and classify other terminals as intra-cell terminals. Alternatively, the base station 100 may classify, for example, terminals with interference power equal to or greater than a specified threshold as cell-edge terminals, and terminals with interference power less than the threshold as intra-cell terminals.

[0060] Next, the base station 100 may perform intra-cell interference control for, for example, the in-cell terminal (S106).

[0061] Furthermore, base station 100 may perform inter-cell interference control for, for example, cell edge terminals (S107 to S111). In the inter-cell interference control, for example, in order to select a communication band (for example, a partial band) to be used in FFR in each base station (or each cell), individual reception quality measurement may be performed on the partial band.

[0062] For example, in inter-cell interference control, the base station 100 may select a distributed antenna (for example, called a distributed antenna for cell-edge terminal) to be assigned to the cell-edge terminal (S107). For example, the base station 100 may set a distributed antenna located near the cell-edge terminal as the distributed antenna for the cell-edge terminal based on the location information of the cell-edge terminal.

[0063] Base station 100 transmits DL-RS (e.g., CSI-RS) to terminal 200 from, for example, a distributed antenna for cell edge terminals (S108-1). Terminal 200 may receive DL-RS (e.g., CSI-RS) from base stations of other cells (e.g., distributed antennas) in addition to CSI-RS from base station 100 (S108-2). Terminal 200 measures, for example, downlink interference levels (e.g., interference power) individually for partial bands (S109). For example, terminal 200 may measure interference power (e.g., average interference power) based on CSI-RS from each cell.

[0064] Here, the base station 100 may allocate the NZP-CSI-RS to the partial bands individually for the distributed antennas for the cell edge terminals, for example. In other words, the base station 100 may not allocate the NZP-CSI-RS to the distributed antennas different from the distributed antennas for the cell edge terminals, for example. In addition, the NZP-CSI-RS for measuring the reception quality individually for the partial bands may be a resource different from the CSI-RS used for the above-mentioned user classification, for example.

[0065] 10 is a diagram illustrating an example of CSI-RS resource allocation in a distributed antenna for a cell edge terminal. In the example of FIG. 10, in FFR, partial bands W 1 , W 2 and W 3 As shown in Fig. 10, NZP-CSI-RS resources may be set to different positions (e.g., different REs) between adjacent cells. In this way, signals (e.g., data channels) of other cells are allocated in the NZP-CSI-RS resources of each cell, and therefore it is possible to improve the accuracy of measuring interference power by terminal 200 in the NZP-CSI-RS resources of each cell.

[0066] Also in FIG. 7, terminal 200 may measure the interference power and SIR between each distributed antenna, for example, based on the CSI-RS (S109).

[0067] Terminal 200 may measure reception quality (for example, at least one of interference power and SIR) using ZP-CSI-RS or both ZP-CSI-RS and NZP-CSI-RS instead of NZP-CSI-RS. This can improve the measurement accuracy of interference from other cells.

[0068] The terminal 200 notifies the base station 100 of at least one of information on the measured interference power and information on the SIR (S110).

[0069] Base station 100, for example, selects (in other words, sets or determines) a communication band (e.g., a partial band) for communicating with terminal 200 in each cell (S111). For example, base station 100 may determine the partial band to be assigned to each cell based on interference power measured individually in the partial band. For example, base station 100 may determine, among multiple partial bands in each cell, a partial band with lower interference power (e.g., the smallest partial band) as the partial band of that cell (hereinafter referred to as the "highest partial band").

[0070] In addition, the base station 100 may select a partial band (hereinafter, referred to as an "additional partial band") that is individually set for the cell edge terminal in addition to the highest partial band that is individually set for the cell (S111). By allocating the additional partial band, the system capacity can be further increased.

[0071] For example, the additional partial band may be selected using an SIR based on the NZP-CSI-RS used in selecting the highest partial band (in other words, a DL-RS different from the CSI-RS used in user classification). For example, the base station 100 may allocate a partial band having an SIR equal to or greater than a specified threshold, among partial bands different from the highest partial band of each cell, as an additional partial band to a cell-edge terminal. In other words, the base station 100 does not need to allocate a partial band having an SIR less than a specified threshold, among partial bands different from the highest partial band of each cell, as an additional partial band to a cell-edge terminal.

[0072] 7, the base station 100, for example, performs scheduling of the terminal 200 (S112). For example, the base station 100 may perform resource allocation to the cell edge terminal based on the highest partial band of each cell and the additional partial band of each cell edge terminal. The base station 100 may also perform resource allocation to the in-cell terminal based on, for example, intra-cell interference control.

[0073] Next, base station 100 and terminal 200 may perform cooperative transmission and reception (for example, MU-MIMO) processing (for example, S113 to S125). In the cooperative transmission and reception, for example, reception quality measurement may be performed to generate transmission weights and reception weights used in cluster-based MU-MIMO transmission.

[0074] For example, base station 100 transmits DL-RS to terminal 200 (S113-1). DL-RS may be, for example, CSI-RS defined in the 3GPP specifications. Terminal 200 may receive DL-RS (for example, CSI-RS) from base stations of other cells (for example, distributed antennas) in addition to CSI-RS from base station 100 (S113-2).

[0075] The terminal 200 measures, for example, interference levels (e.g., DL interference power) from other clusters in the downlink (S114). The terminal 200 also performs, for example, channel estimation between each base station 100 (e.g., each distributed antenna) (S115). The measurement of interference power and channel estimation in the terminal 200 may be based on, for example, CSI-RS transmitted from each cell. The terminal 200 transmits, for example, channel information and information related to DL transmission weights, such as interference power, to the base station 100 (S116).

[0076] Here, in DL channel estimation (e.g., the process of S115), for example, NZP-CSI-RS resources may be orthogonalized between distributed antennas in the same cluster. This allows terminal 200 to separate signals from each distributed antenna in the cluster. Meanwhile, NZP-CSI-RS resources of distributed antennas in different clusters may be shared.

[0077] In this way, in DL channel estimation, by orthogonalizing the resources of reference signals (e.g., NZP-CSI-RS used for channel estimation) within a cluster and sharing the resources of reference signals between clusters, it is not necessary to orthogonalize the resources of reference signals between all distributed antennas within a cell, thereby reducing the overhead caused by reference signals.

[0078] In addition, between clusters where there is a possibility of large inter-cluster interference, for example, when the distance between the clusters is equal to or less than a threshold, the NZP-CSI-RS resources may be orthogonalized. For example, the NZP-CSI-RS resources may be different from the resources used for partial band selection.

[0079] Furthermore, in DL interference measurement from other clusters (for example, the process of S114), for example, ZP-CSI-RS resources of distributed antennas between clusters may be made orthogonal as shown in Fig. 11. This can improve the measurement accuracy of interference power from distributed antennas of other clusters in a cluster configured in terminal 200. On the other hand, ZP-CSI-RS may be shared between distributed antennas in the same cluster.

[0080] In this way, in DL interference measurement, by orthogonalizing the resources of reference signals (e.g., ZP-CSI-RS used for DL ​​interference measurement) of distributed antennas between clusters and sharing the resources of reference signals within a cluster, it is not necessary to orthogonalize the resources of reference signals between all distributed antennas in a cell, for example, and therefore the overhead due to reference signals can be reduced.

[0081] 7, base station 100 generates DL transmission weights (S117) based on, for example, information on DL transmission weights transmitted from terminal 200. Base station 100 may generate DL transmission weights based on, for example, a Minimum Mean Square Error (MMSE) criterion.

[0082] The base station 100 transmits, for example, a reference signal for DL ​​demodulation (for example, a Demodulation Reference Signal (DMRS)) (S118). Note that the base station 100 may multiply the DMRS by a DL transmission weight.

[0083] Terminal 200 may perform channel estimation based on the DL DMRS (S119), and generate DL receiving weights based on the channel estimation value (S120). Terminal 200 may also generate UL transmitting weights based on the channel estimation value (S121).

[0084] Terminal 200 transmits, for example, a reference signal for UL demodulation (for example, DMRS) (S122). Note that terminal 200 may multiply the DMRS by a UL transmission weight, for example.

[0085] The base station 100 may measure UL interference power based on, for example, the UL DMRS (S123), perform channel estimation (S124), and generate UL receiving weights based on the UL interference power and the channel estimation value (S125). The base station 100 may generate UL receiving weights based on, for example, the MMSE standard.

[0086] Thus, in this embodiment, base station 100 transmits reference signals (e.g., CSI-RS) in multiple communication bands (e.g., partial bands) using some of the multiple distributed antennas (e.g., distributed antennas for cell edge terminals) and determines which of the multiple communication bands to assign to terminal 200 based on the results of measurements using the reference antennas. For example, base station 100 may receive the results (e.g., information on DL interference power) measured by terminal 200 using reference signals transmitted from the selected portion of the distributed antennas and determine the partial band for terminal 200 based on the received results.

[0087] In this way, when selecting a partial band in inter-cell interference control, CSI-RS for measuring individual reception quality in the partial band is transmitted from a distributed antenna for a cell-edge terminal, so that, for example, CSI-RS resources do not need to be allocated to a distributed antenna other than the distributed antenna for the cell-edge terminal, thereby reducing the overhead of reference signals.

[0088] In inter-cell interference control, the base station 100 autonomously selects a partial band based on, for example, information on interference power notified from the terminal 200 in the cell. This eliminates the need for the base station 100 to exchange interference information on partial bands between base stations (or between cells), for example, and thus makes it possible to suppress an increase in traffic between base stations.

[0089] In addition, in this embodiment, base station 100 controls the generation of transmission weights based on a result of measurement using a reference signal (e.g., a first reference signal) to which orthogonal resources are allocated within an antenna group constituting a cluster formed in a cell, and a reference signal (e.g., a second reference signal) to which orthogonal resources are allocated between a plurality of antenna groups. For example, the result of measurement may include a channel estimation value based on the first reference signal, and an interference power to terminal 200 based on the second reference signal. For example, in this embodiment, the first reference signal may be a downlink reference signal (e.g., NZP-CSI-RS), and the second reference signal may be a downlink reference signal (e.g., ZP-CSI-RS).

[0090] In this way, when generating transmission weights for cooperative transmission and reception, the CSI-RS resources for measuring channel estimation values ​​are orthogonal within a cluster and shared between clusters, or the CSI-RS resources for measuring interference power are orthogonal between clusters and shared within a cluster, so that it is not necessary to orthogonalize all reference signal resources within a cell, thereby reducing reference signal overhead.

[0091] (Embodiment 2) The configurations of the base station and terminal according to the present embodiment may be similar to those of the first embodiment.

[0092] In the first embodiment, the reception quality measurement using CSI-RS that is a downlink reference signal (DL-RS) has been described. For example, in the first embodiment, information on the reception quality is fed back from terminal 200 to base station 100.

[0093] In this embodiment, for example, a case where reception quality measurement using an uplink reference signal (UL-RS) is performed for DL ​​reception quality measurement performed in each of partial band selection in inter-cell interference control and DL transmission weight generation in distributed MIMO cooperative transmission and reception will be described. For example, by utilizing the reciprocity of a propagation path assuming Time Division Duplex (TDD), DL reception quality such as interference from other cells may be replaced by UL reception quality using a Sounding Reference Signal (SRS), which is an uplink reference signal (UL-RS). As a result, since the reception quality is measured in the base station 100, information on the reception quality does not need to be fed back, and the amount of signaling can be reduced.

[0094] In this embodiment, in base station 100 shown in FIG. 5, control unit 101 may determine information regarding the configuration of uplink reference signals in addition to information regarding the configuration of downlink reference signals, for example, as in embodiment 1.

[0095] Also, for example, in the first embodiment, the control unit 101 performs inter-cell interference control based on information on reception quality fed back from the terminal 200, whereas in this embodiment, the control unit 101 may perform inter-cell interference control based on a measurement result of reception quality using a reference signal transmitted from the terminal 200 (for example, the output of the measurement unit 103). Also, for example, in the first embodiment, the control unit 101 generates downlink transmission weights based on information on reception quality fed back from the terminal 200, whereas in this embodiment, the control unit 101 may generate downlink transmission weights based on a measurement result of reception quality using a reference signal transmitted from the terminal 200 (for example, the output of the measurement unit 103).

[0096] For example, in addition to the operation of the first embodiment, the measurement unit 103 may measure the reception quality (for example, interference power or channel estimation value) used to generate the downlink transmission weight based on the reference signal transmitted from the terminal 200.

[0097] In addition, in the present embodiment, in the terminal 200 shown in Fig. 6, for example, the measurement unit 203 does not need to measure the reception quality used for inter-cell interference control and the reception quality used for generating the downlink transmission weight. In other words, for example, the control information transmitted from the communication unit 202 does not need to include information on the reception quality such as channel information, interference power, or SIR.

[0098] Fig. 12 is a sequence diagram showing an example of the operation of base station 100 (for example, a distributed antenna) and terminal 200. Note that in Fig. 12, the same operations as those in Fig. 7 are denoted by the same reference numerals.

[0099] 12, base station 100 transmits, for example, information on the configuration of DL-RS and information on the configuration of UL-RS to terminal 200 (S201). The configuration information of DL-RS and UL-RS may be notified (or configured) from base station 100 to terminal 200 by, for example, higher layer signaling. For example, DL-RS may be CSI-RS, and UL-RS may be SRS.

[0100] In addition, in the inter-cell interference control, as in the first embodiment, the reception quality measurement may be performed individually for the partial band. In this embodiment, the partial band in the inter-cell interference control may be selected based on the interference power measured individually for the partial band. Also, for example, the interference power may be measured using the SRS from the terminal of another cell received by the distributed antenna for the cell edge terminal.

[0101] For example, in inter-cell interference control, terminal 200 transmits UL-RS (for example, SRS) (S208-1). Base station 100 may receive UL-RS (for example, SRS) from terminals of other cells in addition to SRS from terminal 200 (S208-2).

[0102] The base station 100, for example, measures the uplink interference level (for example, interference power) for each partial band individually (S209). For example, the base station 100 may receive the SRS transmitted from each terminal at a distributed antenna assigned for the cell edge terminal, and measure the interference power (for example, average interference power) based on the received SRS.

[0103] Here, in measuring interference power, since the SRS from terminal 200 in the cell corresponding to base station 100 is a known reference signal, base station 100 can cancel the SRS from terminal 200. Thus, base station 100 may, for example, exclude an SRS from terminal 200 in the cell of base station 100 that is received simultaneously with an SRS from a terminal in another cell. Alternatively, base station 100 may exclude an SRS from terminal 200 in the cell by not scheduling an SRS for terminal 200 in the cell when measuring interference power. This can improve the accuracy of measuring interference power based on an SRS from a terminal in another cell in base station 100.

[0104] Furthermore, the base station 100 may measure the SIR between itself and each cell edge terminal, for example, based on the SRS.

[0105] FIG. 13 is a diagram illustrating an example of resource allocation for SRS. In the example of FIG. 13, in FFR, a partial band W 1 , W 2 and W 3 As shown in Fig. 13, the SRS is transmitted in a partial band allocated to the cell edge terminal of each cell, and does not need to be transmitted in a partial band different from the partial band allocated to the cell edge terminal of each cell.

[0106] 13, for example, base station 100 of cell #1 may measure interference power of partial band W2 and partial band W3 using SRS transmitted from terminals in cell #2 and cell #3. Also, for example, base station 100 of cell #1 may measure interference power of partial band W1, excluding SRS transmitted from terminal 200 in cell #1. Then, base station 100 of cell #1 may set (or re-set) a partial band (for example, the highest partial band) to be assigned to cell edge terminals of cell #1 based on the interference power of each partial band.

[0107] Also, the base station 100 of the cell #1 may determine an additional partial band for each cell edge terminal in addition to the highest partial band. For example, the SIR measured for each partial band using the SRS may be used to set the additional partial band.

[0108] Similarly to cell #1, partial bands may be set for cell #2 and cell #3.

[0109] In this manner, in this embodiment, base station 100 may estimate DL reception quality based on uplink reception quality based on SRS transmitted from terminal 200, and select partial bands to be set for cell edge terminals of each cell. This eliminates the need for base station 100 to transmit DL-RS, and for terminal 200 to measure and notify reception quality, for example, and therefore reduces the amount of processing related to partial band selection.

[0110] Next, base station 100 and terminal 200 may perform cooperative transmission and reception (e.g., MU-MIMO) processing. In the cooperative transmission and reception, for example, reception quality measurement may be performed to generate transmission weights and reception weights used in cluster-based MU-MIMO transmission.

[0111] In this embodiment, DL transmission weights in cooperative transmission and reception may be generated based on, for example, channel estimation values ​​and interference power measured by base station 100 using SRS transmitted from terminals in each cell.

[0112] For example, terminal 200 transmits a UL-RS (for example, an SRS) (S213-1). Base station 100 may receive, for example, an SRS from terminal 200 as well as a UL-RS (for example, an SRS) from terminals of other cells (S213-2). For example, the resource for the SRS may be a resource different from the resource for the SRS used for partial band selection.

[0113] The base station 100 measures, for example, an interference level (e.g., interference power) from other clusters in the uplink (S214). The base station 100 also performs, for example, channel estimation between each distributed antenna and the terminal 200 (S215). The measurement of interference power and channel estimation in the base station 100 may be based on, for example, an SRS transmitted from each terminal. In this way, the base station 100 may estimate the DL reception quality by measuring the UL reception quality.

[0114] Here, in DL channel estimation (e.g., the process of S215), for example, SRS resources may be orthogonalized between terminals in the same cluster. For example, the SRS may be orthogonalized by a code. This allows base station 100 to separate signals from terminals in the cluster. Meanwhile, SRS resources (e.g., codes used for SRS) of terminals in different clusters may be shared.

[0115] In this way, in DL channel estimation, by orthogonalizing the reference signal resources among terminals within a cluster and sharing the reference signal resources among terminals between clusters, it is not necessary to orthogonalize the reference signal resources among all distributed antennas within a cell, and therefore the overhead caused by the reference signals can be reduced.

[0116] For example, between clusters where there is a possibility of large inter-cluster interference, such as when the distance between the clusters is equal to or less than a threshold, SRS resources may be orthogonalized between terminals.

[0117] Furthermore, in measuring UL interference from other clusters in DL (for example, the process of S214), SRS resources of terminals between clusters may be orthogonalized. The SRS resources may be different from the SRS resources used for channel estimation, for example. This can improve the measurement accuracy of interference power from other clusters to terminal 200 in base station 100. On the other hand, SRS may be shared between terminals in the same cluster.

[0118] In this way, in DL interference measurement, by orthogonalizing the reference signal (e.g., SRS) resources of terminals between clusters and sharing the reference signal resources of terminals within a cluster, it is not necessary to orthogonalize the reference signal resources between all terminals within a cell, thereby reducing the overhead caused by reference signals.

[0119] In this manner, in this embodiment, base station 100 may estimate DL reception quality and generate DL transmission weights based on uplink reception quality based on SRS transmitted from terminal 200. This eliminates the need for base station 100 to transmit DL-RS and for terminal 200 to measure and notify reception quality, for example, and therefore reduces processing related to partial band selection.

[0120] It is not necessary to perform high-precision measurement of interference power from other cells. Therefore, for example, the processing load of base station 100 may be reduced by omitting measurement of interference power from other cells.

[0121] An example of the operation of base station 100 and terminal 200 according to this embodiment has been described above.

[0122] In this embodiment, in the selection of partial bands in inter-cell interference control, for example, base station 100 may receive reference signals (e.g., SRS) in multiple bands (e.g., partial bands) using some distributed antennas (e.g., distributed antennas for cell edge terminals) among multiple distributed antennas, and may determine which of the multiple bands to assign to terminal 200 based on the result of measurement using the reference signals. This eliminates the need to feed back information related to reception quality from terminal 200 to base station 100, for example, and thus can reduce overhead in the uplink.

[0123] In addition, in inter-cell interference control, the base station 100 autonomously selects a partial band based on, for example, interference power measured based on an uplink reference signal. This eliminates the need for the base station 100 to exchange interference information related to partial bands between base stations (or between cells), thereby suppressing an increase in traffic between base stations.

[0124] Furthermore, in this embodiment, base station 100 performs channel estimation based on an SRS that allocates orthogonal resources within a cluster (in other words, an antenna group) formed within a cell, performs interference measurement based on SRSs allocated to orthogonal resources in multiple clusters, and controls the generation of transmission weights based on the results of the channel estimation and interference measurement.

[0125] In this way, when generating transmission weights for cooperative transmission and reception, the SRS resources for measuring channel estimation values ​​are orthogonal within a cluster and shared between clusters, or the SRS resources for measuring interference power are orthogonal between clusters and shared within a cluster, so that it is not necessary to orthogonalize all reference signal resources within a cell, thereby reducing reference signal overhead.

[0126] (Embodiment 3) The configurations of the base station and terminal according to the present embodiment may be similar to those of the first embodiment.

[0127] In the second embodiment, a case has been described in which SRS, which is a UL reference signal, is used for measuring (or channel estimation) DL interference power used for generating DL transmission weights in distributed MIMO cooperative transmission and reception. In this case, an error may occur between the measured UL interference power and the DL interference power to terminal 200. When an error occurs, the accuracy of transmission weight generation may be reduced.

[0128] Therefore, in this embodiment, a case will be described in which a method of using CSI-RS, which is a DL reference signal in embodiment 1, is applied to the measurement of interference power from other clusters when generating transmission weights in embodiment 2. This method can improve the measurement accuracy of interference power in distributed MIMO cooperative transmission and reception.

[0129] In this embodiment, the processes related to inter-cell interference control in the control unit 101, the communication unit 102, and the measurement unit 103 of the base station 100 shown in Fig. 5 may be the same as those in embodiment 2. Also, the processes related to generation of transmit and receive weights in the control unit 101, the communication unit 102, and the measurement unit 103 of the base station 100 shown in Fig. 5 may be the same as those in embodiment 1.

[0130] Similarly, in this embodiment, the processes related to inter-cell interference control in control unit 201, communication unit 202 and measurement unit 203 of terminal 200 shown in Fig. 6 may be the same as those in embodiment 2. Also, the processes related to generation of transmit and receive weights in control unit 201, communication unit 202 and measurement unit 203 of terminal 200 shown in Fig. 6 may be the same as those in embodiment 1.

[0131] Fig. 14 is a sequence diagram showing an example of the operation of base station 100 (for example, a distributed antenna) and terminal 200. In Fig. 14, the same operations as those in the first embodiment (Fig. 7) and the second embodiment (Fig. 12) are denoted by the same reference numerals.

[0132] As shown in FIG. 14, in the inter-cell interference control process, for example, similarly to the second embodiment, the partial band may be selected based on interference power measurement using the UL-RS (for example, SRS).

[0133] Also, as shown in FIG. 14, in the process of cooperative transmission and reception control, DL interference power may be measured based on DL-RS (e.g., CSI-RS) as in embodiment 1, and DL channel estimation may be performed based on UL-RS (SRS) as in embodiment 2.

[0134] For example, in cooperative transmission and reception control, the period (or frequency) of interference power measurement can be low compared to the update period (or update frequency) of DL transmission weight. Therefore, for example, the amount of feedback of information on interference power from terminal 200 to base station 100 by CSI-RS measurement can be reduced compared to the first embodiment.

[0135] In this way, in cooperative transmission and reception control (e.g., generation of DL transmission weights), for example, an uplink reference signal is used as a reference signal for channel estimation, and a downlink reference signal is used as a reference signal for measuring interference power. This allows base station 100 to generate DL transmission weights based on interference power according to the actual downlink situation, thereby improving the accuracy of transmission weight generation.

[0136] Note that base station 100 may estimate DL interference power by, for example, acquiring information on the positions of distributed antennas including other cells in advance and calculating path loss based on the position information of each terminal 200 in the cell corresponding to base station 100 and the position information of the distributed antennas. This makes it possible to omit DL interference power measurement by DL CSI-RS and reduce overhead due to CSI-RS.

[0137] In this embodiment, the DL-RS (e.g., CSI-RS) and the UL-RS (e.g., SRS) may be allocated in the same slot as shown in Fig. 8, or may be allocated in different slots. Also, for example, the transmission period of the DL-RS and the UL-RS may be different.

[0138] (Embodiment 4) The configurations of the base station and terminal according to the present embodiment may be similar to those of the first embodiment.

[0139] In the first to third embodiments, an example has been described in which, in generating transmission weights in distributed MIMO cooperative transmission and reception, DL transmission weights are generated first, and then UL transmission weights are generated.

[0140] In this embodiment, an example will be described in which, in generating transmission weights in distributed MIMO cooperative transmission and reception, UL transmission weights are generated first, and then DL transmission weights are generated.

[0141] In this embodiment, the processing related to inter-cell interference control in the control unit 101, the communication unit 102 and the measurement unit 103 of the base station 100 shown in Fig. 5 may be the same as that in the first embodiment or may be the same as that in the second embodiment. Also, the order of processing related to generation of transmission and reception weights in the control unit 101, the communication unit 102 and the measurement unit 103 of the base station 100 shown in Fig. 5 is different from the order of processing in the first embodiment. For example, the control unit 101 may generate the UL reception weight first, and then generate the DL transmission weight.

[0142] Similarly, in this embodiment, the processing related to inter-cell interference control in control section 201, communication section 202 and measurement section 203 of terminal 200 shown in Fig. 6 may be the same as that in embodiment 1 or may be the same as that in embodiment 2. Also, the order of processing related to generation of transmission and reception weights in control section 201, communication section 202 and measurement section 203 of terminal 200 shown in Fig. 6 is different from the order of processing in embodiment 1. For example, control section 201 may generate UL transmission weights first, and then generate DL reception weights.

[0143] Fig. 15 is a sequence diagram showing an example of the operation of base station 100 (for example, a distributed antenna) and terminal 200. In Fig. 15, the same operations as those in the first embodiment (Fig. 7) and the second embodiment (Fig. 12) are denoted by the same reference numerals.

[0144] For example, in the inter-cell interference control shown in Fig. 15, base station 100 and terminal 200 may perform the same operation as in embodiment 2. Note that the inter-cell interference control is not limited to this, and for example, the same inter-cell interference control as in embodiment 1 may be applied.

[0145] Also, in the cooperative transmission / reception control shown in Fig. 15, for example, base station 100 transmits DL-RS (for example, CSI-RS) (S113-1) as in the first and third embodiments. Terminal 200 measures DL interference power using CSI-RS (for example, ZP-CSI-RS) (S114) and performs channel estimation using CSI-RS (for example, NZP-CSI-RS) (S115). Then, terminal 200 generates UL transmission weights based on at least the channel estimation value, for example (S315).

[0146] Terminal 200 transmits information on DL interference power and a UL-RS (for example, a DMRS) to base station 100 (S316). Note that the UL-RS may be multiplied by, for example, a UL transmission weight.

[0147] Base station 100 may use, for example, UL DM-RS to measure UL interference power (S123) and perform channel estimation (S124), and generate UL receiving weights based on the MMSE norm (S125). Note that the UL interference power used when generating the UL receiving weights in base station 100 may be calculated by the UL-RS (SRS) transmitted from terminal 200.

[0148] Furthermore, base station 100 generates DL transmission weights based on the DL interference power information received from terminal 200 and the channel estimation result using the UL DM-RS (S317).

[0149] Base station 100 transmits a DL-RS (for example, a DMRS) to terminal 200 (S118). Note that the DL-RS may be multiplied by, for example, a DL transmission weight.

[0150] Terminal 200 performs channel estimation based on, for example, the DL DM-RS (S119) and generates DL receiving weights (S120).

[0151] In this way, in the coordinated transmission and reception control, for example, the downlink CSI-RS is used as a reference signal for channel estimation and interference power measurement. This allows terminal 200 to generate UL transmission weights based on, for example, a channel estimation value using CSI-RS. Furthermore, terminal 200 feeds back, for example, information related to interference power using CSI-RS, and base station 100 can generate UL reception weights and DL transmission weights based on the information related to the fed back interference power. This allows the amount of information (for example, DL channel estimation value) fed back from terminal 200 to base station 100 to be reduced compared to, for example, the first embodiment (for example, FIG. 7), and therefore signaling overhead can be reduced.

[0152] Furthermore, according to this embodiment, base station 100 can generate UL receiving weights together with DL transmission weights based on information on DL interference power measured by CSI-RS and UL DM-RS. As a result, for example, base station 100 does not need to receive UL-DM-RS and generate UL receiving weights after transmitting DL DM-RS (for example, DM-RS multiplied by DL transmission weight) as in the first embodiment (for example, FIG. 7), and therefore can simplify the process of generating transmission and reception weights.

[0153] The embodiments of the present disclosure have been described above.

[0154] In the above-described embodiments, as an example, the case where both interference control (e.g., inter-cell interference control) and cooperative transmission / reception control are performed has been described, but inter-cell interference control and cooperative MIMO transmission / reception can be controlled independently. For example, the base station 100 and the terminal 200 may separately combine the inter-cell interference control of each embodiment and the cooperative transmission / reception control of each embodiment. Furthermore, the base station 100 and the terminal 200 may apply, for example, either the inter-cell interference control or the cooperative transmission / reception control, without applying the other.

[0155] Also, for example, in cooperative MIMO transmission and reception, the reference signal used for each of the interference power measurement and the channel estimation may be DL-RS (for example, CSI-RS) or UL-RS (SRS).

[0156] In addition, in each of the above-mentioned embodiments, CSI-RS is described as an example of a downlink reference signal, and SRS is described as an example of an uplink reference signal, but the reference signals are not limited to CSI-RS and SRS, and may be other reference signals.

[0157] Furthermore, in each of the above-described embodiments, the frame format shown in FIG. 8 has been described as an example, but the present invention is not limited to this and other frame formats may be used.

[0158] Moreover, the settings of each parameter in each of the above-mentioned embodiments are merely examples and are not limited thereto. For example, the number of cells and the number of partial bands are not limited to three, and may be other values. Also, for example, the bandwidth of each partial band may be the same or different. Also, for example, the number of highest partial bands (number of partial bands) set in each cell may be different. Also, for example, as shown in FIG. 8, resources to which reference signals (for example, CSI-RS in FIG. 8) are assigned are not limited to multiple resources in the frequency domain, and may be, for example, resources in the time domain.

[0159] Furthermore, the functions of the base station 100 may be separated into functional modules such as a Central Unit (CU), a Distributed Unit (DU), and a Radio Unit (RU). For example, the control unit 101 of the base station 100 may be included in the CU or the DU, and the communication unit 102 (including, for example, a distributed antenna) may be included in the RU. Note that the distribution of the functions (each component) of the base station 100 is not limited to this, and other functional distributions may also be used. For example, the DU may have a Radio Link Control (RLC) function, a MAC function, and a High-PHY function, and the RU may have a Low-PHY function and an RF function. Alternatively, for example, the DU may have an RLC function and a MAC function, and the RU may have a PHY (including, for example, a High-PHY function and a Low-PHY function) and an RF function.

[0160] In the above-mentioned embodiment, the unit of the time resource may be a time resource unit such as a subframe, a slot, or a symbol, or may be another time resource unit. In the above-mentioned embodiment, the unit of the frequency resource may be a frequency resource unit such as a BWP, an RB, or a PRB, or may be another frequency resource unit.

[0161] In addition, the notation "... part" in the above-mentioned embodiments may be replaced with other notations such as "... circuitry," "... device," "... unit," or "... module."

[0162] (Control signal) In the present disclosure, a downlink control signal (or downlink control information) related to an embodiment of the present disclosure may be, for example, a signal (or information) transmitted in a Physical Downlink Control Channel (PDCCH) in a physical layer, or a signal (or information) transmitted in a Medium Access Control Control Element (MAC CE) or Radio Resource Control (RRC) in a higher layer. In addition, the signal (or information) is not limited to being notified by a downlink control signal, and may be predefined in a specification (or standard), or may be preconfigured in a base station and a terminal.

[0163] In the present disclosure, an uplink control signal (or uplink control information) related to an embodiment of the present disclosure may be, for example, a signal (or information) transmitted in a PUCCH of a physical layer, or a signal (or information) transmitted in a MAC CE or RRC of a higher layer. Furthermore, the signal (or information) is not limited to being notified by an uplink control signal, and may be predefined in a specification (or standard), or may be preconfigured in a base station and a terminal. Furthermore, the uplink control signal may be replaced with, for example, uplink control information (UCI), 1st stage sidelink control information (SCI), or 2nd stage SCI.

[0164] (base station) In an embodiment of the present disclosure, the base station may be a Transmission Reception Point (TRP), a cluster head, an access point, a Remote Radio Head (RRH), an eNodeB (eNB), a gNodeB (gNB), a Base Station (BS), a Base Transceiver Station (BTS), a parent device, a gateway, or the like. In addition, in sidelink communication, the base station may be replaced by a terminal. In addition, the base station may be replaced by a relay device that relays communication between an upper node and a terminal. In addition, the base station may be replaced by a roadside unit.

[0165] (Uplink / Downlink / Sidelink) An embodiment of the present disclosure may be applied to, for example, any of an uplink, a downlink, and a sidelink. For example, an embodiment of the present disclosure may be applied to a Physical Uplink Shared Channel (PUSCH), a Physical Uplink Control Channel (PUCCH), a Physical Random Access Channel (PRACH) of an uplink, a Physical Downlink Shared Channel (PDSCH), a PDCCH, a Physical Broadcast Channel (PBCH) of a downlink, or a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Broadcast Channel (PSBCH) of a sidelink.

[0166] The PDCCH, PDSCH, PUSCH, and PUCCH are examples of a downlink control channel, a downlink data channel, an uplink data channel, and an uplink control channel, respectively. The PSCCH and PSSCH are examples of a sidelink control channel and a sidelink data channel, respectively. The PBCH and PSBCH are examples of a broadcast channel, and the PRACH is an example of a random access channel.

[0167] (Data Channel / Control Channel) An embodiment of the present disclosure may be applied to, for example, any of a data channel and a control channel. For example, the channel in an embodiment of the present disclosure may be replaced with any of the data channels PDSCH, PUSCH, and PSSCH, or the control channels PDCCH, PUCCH, PBCH, PSCCH, and PSBCH.

[0168] (reference signal) In one embodiment of the present disclosure, the reference signal is, for example, a signal known by both the base station and the mobile station, and may be called a Reference Signal (RS) or a pilot signal. The reference signal may be any of a Demodulation Reference Signal (DMRS), a Channel State Information - Reference Signal (CSI-RS), a Tracking Reference Signal (TRS), a Phase Tracking Reference Signal (PTRS), a Cell-specific Reference Signal (CRS), or a Sounding Reference Signal (SRS).

[0169] (Time Interval) In an embodiment of the present disclosure, the unit of time resource is not limited to one or a combination of slots and symbols, but may be, for example, a time resource unit such as a frame, a superframe, a subframe, a slot, a time slot subslot, a minislot, or a symbol, an Orthogonal Frequency Division Multiplexing (OFDM) symbol, a Single Carrier-Frequency Division Multiplexing (SC-FDMA) symbol, or another time resource unit. Also, the number of symbols included in one slot is not limited to the number of symbols exemplified in the above embodiment, and may be another number of symbols.

[0170] (Frequency band) An embodiment of the present disclosure may be applied to either a licensed band or an unlicensed band.

[0171] (communication) An embodiment of the present disclosure may be applied to any of communication between a base station and a terminal (Uu link communication), communication between terminals (Sidelink communication), and Vehicle to Everything (V2X) communication. For example, the channel in an embodiment of the present disclosure may be replaced with any of PSCCH, PSSCH, Physical Sidelink Feedback Channel (PSFCH), PSBCH, PDCCH, PUCCH, PDSCH, PUSCH, and PBCH.

[0172] Moreover, an embodiment of the present disclosure may be applied to any of terrestrial networks, non-terrestrial networks (NTNs) using satellites or High Altitude Pseudo Satellites (HAPSs), etc. Furthermore, an embodiment of the present disclosure may be applied to terrestrial networks in which the transmission delay is large compared to the symbol length or slot length, such as networks with large cell sizes and ultra-wideband transmission networks.

[0173] (Antenna port) In one embodiment of the present disclosure, an antenna port refers to a logical antenna (antenna group) consisting of one or more physical antennas. For example, an antenna port does not necessarily refer to one physical antenna, but may refer to an array antenna consisting of multiple antennas. For example, the number of physical antennas that an antenna port is composed of is not specified, and the antenna port may be specified as the minimum unit by which a terminal station can transmit a reference signal. In addition, an antenna port may be specified as the minimum unit for multiplying a weight of a precoding vector.

[0174] The present disclosure can be realized by software, hardware, or software in cooperation with hardware. Each functional block used in the description of the above embodiment may be realized partially or entirely as an LSI, which is an integrated circuit, and each process described in the above embodiment may be controlled partially or entirely by one LSI or a combination of LSIs. The LSI may be composed of individual chips, or may be composed of one chip so as to include some or all of the functional blocks. The LSI may have input and output of data. Depending on the degree of integration, the LSI may be called an IC, a system LSI, a super LSI, or an ultra LSI.

[0175] The method of integration is not limited to LSI, and may be realized by a dedicated circuit, a general-purpose processor, or a dedicated processor. Also, after LSI manufacturing, a programmable FPGA (Field Programmable Gate Array) or a reconfigurable processor that can reconfigure the connections and settings of circuit cells inside the LSI may be used. The present disclosure may be realized as digital processing or analog processing.

[0176] Furthermore, if a new integrated circuit technology that can replace LSI appears due to the progress of semiconductor technology or a derivative technology, it is possible to integrate the functional blocks using that technology. The application of biotechnology is also a possibility.

[0177] In this disclosure, a terminal (UE) communicating with a base station includes any type of apparatus, device, or system having a communication function (collectively referred to as a communication apparatus). The communication apparatus may include a radio transceiver and a processing / control circuit. The radio transceiver may include a receiver and a transmitter, or both as functions. The radio transceiver (transmitter and receiver) may include a radio frequency (RF) module and one or more antennas. The RF module may include an amplifier, an RF modulator / demodulator, or the like. Non-limiting examples of communication devices include telephones (e.g., cell phones, smartphones, etc.), tablets, personal computers (PCs) (e.g., laptops, desktops, notebooks, etc.), cameras (e.g., digital still / video cameras), digital players (e.g., digital audio / video players), wearable devices (e.g., wearable cameras, smart watches, tracking devices, etc.), game consoles, digital book readers, telehealth and telemedicine devices, communication-enabled vehicles or mobile conveyances (e.g., cars, airplanes, boats, etc.), and combinations of the above devices.

[0178] Communications Equipment includes, but is not limited to portable or mobile equipment, non-portable or fixed equipment, devices and systems of any kind, such as smart home devices (appliances, lighting equipment, smart meters or metering devices, control panels, etc.), vending machines and any other "Things" that may exist on an Internet of Things (IoT) network.

[0179] Communications include data communications via cellular systems, wireless LAN systems, communications satellite systems, etc., as well as data communications via combinations of these.

[0180] A communications apparatus also includes devices, such as controllers and sensors, connected or coupled to a communications device that performs the communications functions described in this disclosure, such as controllers and sensors that generate control and data signals used by the communications device to perform the communications functions of the communications apparatus.

[0181] The present disclosure also includes infrastructure facilities, such as base stations, access points, and any other apparatus, devices, or systems that communicate with or control the various apparatuses listed above, but are not limited thereto.

[0182] A base station according to one embodiment of the present disclosure includes a communication circuit that transmits or receives reference signals in multiple bands using some of multiple antennas, and a control circuit that determines which of the multiple bands to assign to a terminal based on a result of a measurement using the reference signals.

[0183] In one embodiment of the present disclosure, the communication circuit receives from the terminal a result of measurement made by the terminal using the transmitted downlink reference signal.

[0184] In one embodiment of the present disclosure, the communication circuit receives the uplink reference signal transmitted from the terminal, and the control circuit performs the measurement using the uplink reference signal.

[0185] In one embodiment of the present disclosure, the allocated resources of the reference signals are different among a plurality of cells.

[0186] A base station according to one embodiment of the present disclosure includes a control circuit that controls generation of transmission weights based on results of measurements using a first reference signal to which orthogonal resources are assigned within an antenna group that constitutes a cluster formed within a cell, and a second reference signal to which orthogonal resources are assigned between a plurality of the antenna groups, and a communication circuit that performs communication using the transmission weights.

[0187] In one embodiment of the present disclosure, the measurement result includes a channel estimate based on the first reference signal and an interference power to the terminal based on the second reference signal.

[0188] In one embodiment of the present disclosure, the first reference signal and the second reference signal are downlink reference signals, and the transmission weights are downlink transmission weights.

[0189] In one embodiment of the present disclosure, the first reference signal and the second reference signal are uplink reference signals, and the transmission weights are downlink transmission weights.

[0190] In one embodiment of the present disclosure, the first reference signal is an uplink reference signal, the second reference signal is a downlink reference signal, and the transmission weight is a downlink transmission weight.

[0191] In one embodiment of the present disclosure, the first reference signal and the second reference signal are downlink reference signals, and the transmission weights are uplink transmission weights.

[0192] A terminal according to one embodiment of the present disclosure includes a control circuit that controls generation of a transmission weight based on a result of a measurement using a first reference signal in which orthogonal resources are allocated within an antenna group that constitutes a cluster formed within a cell, and a second reference signal in which orthogonal resources are allocated between a plurality of the antenna groups, and a communication circuit that performs communication using the transmission weight.

[0193] In a communication method according to one embodiment of the present disclosure, a base station transmits or receives reference signals in multiple bands using some of multiple antennas, and determines which of the multiple bands to assign to a terminal based on the results of measurements using the reference signals.

[0194] In a communication method according to one embodiment of the present disclosure, a base station controls generation of transmission weights based on results of measurements using a first reference signal to which orthogonal resources are assigned within an antenna group constituting a cluster formed within a cell, and a second reference signal to which orthogonal resources are assigned between a plurality of the antenna groups, and performs communication using the transmission weights.

[0195] In a communication method according to one embodiment of the present disclosure, a terminal controls generation of transmission weights based on the results of measurements using a first reference signal to which orthogonal resources are assigned within an antenna group constituting a cluster formed within a cell, and a second reference signal to which orthogonal resources are assigned among a plurality of the antenna groups, and performs communication using the transmission weights. [Industrial Applicability]

[0196] One embodiment of the present disclosure is useful in wireless communication systems. [Explanation of symbols]

[0197] 100 base stations 200 terminals 101,201 Control section 102,202 Communications Department 103,203 Measuring part

Claims

1. a communication circuit that transmits or receives reference signals in a plurality of bands using some of a plurality of antennas; A control circuit that determines which of the plurality of bands to assign to a terminal based on a result of measurement using the reference signal, the reference signals include a first reference signal and a second reference signal; The antenna group configures a cluster by some of the plurality of antennas, and the cluster is formed within a cell; the control circuit controls generation of a transmission weight based on a result of measurement using the first reference signal to which orthogonal resources are assigned within the antenna group and the second reference signal to which orthogonal resources are assigned between a plurality of the antenna groups; The communication circuit performs communication using the transmission weight. Base station.

2. The communication circuit receives, from the terminal, a result of measurement made by the terminal using the transmitted downlink reference signal. The base station according to claim 1 .

3. The communication circuit receives the uplink reference signal transmitted from the terminal; The control circuit performs the measurement using the uplink reference signal. The base station according to claim 1 .

4. The allocated resources of the reference signals are different among the plurality of cells. The base station according to claim 1 .

5. The measurement result includes a channel estimate based on the first reference signal and an interference power to the terminal based on the second reference signal. The base station according to claim 1 .

6. the first reference signal and the second reference signal are downlink reference signals; The transmission weight is a transmission weight of the downlink. The base station according to claim 1 .

7. the first reference signal and the second reference signal are uplink reference signals; The transmission weights are downlink transmission weights. The base station according to claim 1 .

8. the first reference signal is an uplink reference signal, and the second reference signal is a downlink reference signal; The transmission weights are downlink transmission weights. The base station according to claim 1 .

9. the first reference signal and the second reference signal are downlink reference signals; The transmission weight is an uplink transmission weight. The base station according to claim 1 .

10. The base station is Transmitting or receiving reference signals in a plurality of bands using some of the plurality of antennas; determining which of the plurality of bands to assign to a terminal based on a result of the measurement using the reference signal; the reference signals include a first reference signal and a second reference signal; The antenna group configures a cluster by some of the plurality of antennas, and the cluster is formed within a cell; controlling generation of transmission weights based on a result of measurement using the first reference signal to which orthogonal resources are assigned within the antenna group and the second reference signal to which orthogonal resources are assigned between a plurality of the antenna groups; performing communication using the transmission weight; Communication methods.

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