User equipment, node, and communication method

Abstract

To suppress a decrease in throughput. [Solution] The user equipment is a user equipment that performs wireless communication with a node in a mobile communication system, and includes: a receiving unit that receives a first reference signal transmitted by the node; a control unit that measures a resource of the first reference signal and calculates a precoder to be used for transmitting a physical uplink shared channel based on the measurement of the resource of the first reference signal and applies the precoder to the physical uplink shared channel; and a transmitting unit that transmits the physical uplink shared channel with the precoder applied to the node.

Description

[Technical field]

[0001] The present invention relates to a user equipment, a node, and a communication method. [Background technology]

[0002] In the 5th generation (5G) standard NR (New Radio) established by the 3rd Generation Partnership Project (3GPP (registered trademark), hereinafter the same) which is a standardization project for mobile communication systems, codebook type and non-codebook type transmission methods are specified as a method of transmitting the physical uplink shared channel (PUSCH). In the non-codebook type, a precoder determined by a node is applied to the transmission of the PUSCH.

[0003] A problem with the non-codebook transmission method is that it takes a long time before a precoder is applied to a PUSCH. In the non-codebook transmission method, communication between a node (also simply referred to as a "node") in a network of a mobile communication system transmits a CSI-RS to a user equipment (UE) and then receives a PUSCH to which a precoder is applied, and two round trips of communication are made between the node and the UE.

[0004] As a result, especially in an environment where the propagation channel fluctuates drastically, the propagation channel may fluctuate significantly between the time when the precoder is calculated and the time when the precoder is applied, and the precoder may become suboptimal. An environment where the propagation channel fluctuates drastically is, for example, an environment where the UE moves at high speed, or an environment where wireless communication using a high frequency band such as millimeter waves or sub-terahertz waves is used. In the latter wireless communication using a high frequency band, the beam is sharper than in a low frequency band, so that a slight change in the environment may cause a larger channel fluctuation. If the precoder becomes suboptimal, the inter-stream interference in the received signal increases, and the modulation accuracy deteriorates, which may result in a decrease in throughput. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] 3GPP Technical Specification: TS 38.214 V18.0.0 (2023-09) Summary of the Invention

[0006] A user equipment according to a first aspect is a user equipment that performs wireless communication with a node in a mobile communication system, and includes: a receiving unit that receives a first reference signal transmitted by the node; a control unit that measures a resource of the first reference signal, calculates a precoder to be used for transmitting a physical uplink shared channel based on the measurement of the resource of the first reference signal, and applies the precoder to the physical uplink shared channel; and a transmitting unit that transmits the physical uplink shared channel with the precoder applied to the node.

[0007] A node according to a second aspect is a node that performs wireless communication with a user equipment in a mobile communication system, and includes a transmitting unit that transmits a first reference signal to the user equipment, and a receiving unit that receives from the user equipment the physical uplink shared channel that has been transmitted by the user equipment and to which a precoder calculated based on measurement of a resource of the first reference signal has been applied.

[0008] A communication method according to a third aspect is a communication method used by a user equipment that performs wireless communication with a node in a mobile communication system, and includes the steps of receiving a first reference signal transmitted by the node, measuring a resource of the first reference signal, calculating a precoder to be used for transmitting a physical uplink shared channel based on the measurement of the resource of the first reference signal, applying the precoder to the physical uplink shared channel, and transmitting the physical uplink shared channel with the precoder applied to the node.

[0009] A communication method according to a fourth aspect is a communication method used in a node that performs wireless communication with a user equipment in a mobile communication system, and includes a step of transmitting a first reference signal to the user equipment, and a step of receiving from the user equipment the physical uplink shared channel transmitted with a precoder calculated based on measurement of a resource of the first reference signal. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a configuration example of a mobile communication system according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of a protocol stack of a U-plane radio interface that handles data. [Diagram 3] FIG. 2 is a diagram illustrating an example of the configuration of a protocol stack of a C-plane wireless interface that handles signaling (control signals). [Figure 4] FIG. 13 is a diagram showing a general procedure in which a precoder determined in a non-codebook manner is applied to transmit a physical uplink shared channel. [Diagram 5] FIG. 2 is a diagram illustrating a configuration example of a UE (user equipment) according to the embodiment. [Figure 6] FIG. 2 is a diagram illustrating an example of the configuration of a node according to the embodiment. [Figure 7] FIG. 2 is a diagram illustrating an example of a system operation according to the first embodiment. [Figure 8] FIG. 11 is a diagram illustrating an example of a system operation according to a modified example of the first embodiment. [Figure 9] FIG. 11 is a diagram illustrating an example of a system operation according to the second embodiment. [Figure 10] FIG. 11 is a diagram illustrating an example of a system operation according to the third embodiment. [Figure 11] FIG. 13 is a diagram illustrating an example of a system operation according to the fourth embodiment. [Figure 12] FIG. 13 is a diagram illustrating an example of a system operation according to the fifth embodiment. [Figure 13] FIG. 13 is a diagram illustrating an example of a system operation according to a modified example of the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0012] (1) First embodiment The first embodiment will be described with reference to FIGS.

[0013] (1.1) System configuration example 1 is a diagram showing a configuration example of a mobile communication system according to an embodiment. The mobile communication system according to the embodiment is a system conforming to the 3GPP standard. For example, the mobile communication system according to the embodiment may be a fifth generation (5G) system or a sixth generation (6G) system.

[0014] The mobile communication system includes a network (NW) 1 and a user equipment (UE) 100. The UE 100 is a mobile communication device that performs wireless communication with the NW 1. The UE 100 may be any device used by a user, and may be, for example, a mobile phone terminal (including a smartphone), a tablet terminal, a notebook PC (Personal Computer), a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0015] The NW1 includes a radio access network (RAN) 10 and a core network (CN) 20. When the mobile communication system is a 5th generation system (5GS: 5th Generation System), the RAN 10 is referred to as a Next Generation Radio Access Network (NG-RAN), and the CN 20 is referred to as a 5G Core Network (5GC).

[0016] The RAN 10 includes a plurality of nodes 200 (nodes 200a to 200c in the illustrated example). The nodes 200 are connected to each other via inter-node interfaces. The nodes 200 are also referred to as base stations. The nodes 200 are configured (i.e., functionally divided) with a CU (Central Unit) and a DU (Distributed Unit), and both units may be connected by a fronthaul interface. When the mobile communication system is 5GS, the nodes 200 are referred to as gNBs, the inter-node interface is referred to as an Xn interface, and the fronthaul interface is referred to as an F1 interface.

[0017] Each node 200 manages one or more cells. The node 200 performs wireless communication with the UE 100 that has established a connection with its own cell. Each node 200 has a radio resource management (RRM) function, a routing function for user data (also simply referred to as "data"), a measurement control function for mobility control and scheduling, and the like. Note that "cell" is used as a term indicating the smallest unit of a wireless communication area. "Cell" is also used as a term indicating a function or resource for performing wireless communication with the UE 100. One cell belongs to one carrier frequency (also simply referred to as "frequency").

[0018] The CN 20 includes a CN device 300. The CN device 300 may include a C-plane device corresponding to a control plane (C-plane) and a U-plane device corresponding to a user plane (U-plane). The C-plane device performs various mobility controls and paging for the UE 100. The C-plane device communicates with the UE 100 using NAS (Non-Access Stratum) signaling. The U-plane device performs data transfer control. When the mobile communication system is 5GS, the C-plane device is called an AMF (Access and Mobility Management Function), the U-plane device is called a UPF (User Plane Function), and the interface between the node 200 and the CN device 300 is called an NG interface.

[0019] FIG. 2 is a diagram showing an example of the configuration of a protocol stack of a U-plane radio interface that handles data.

[0020] The U-plane radio interface protocol includes, for example, a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0021] The PHY layer performs coding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the node 200 via a physical channel. The PHY layer of the UE 100 receives downlink control information (DCI) transmitted from the node 200 on a physical downlink control channel (PDCCH). Specifically, the UE 100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires the successfully decoded DCI as the DCI addressed to the UE. The DCI transmitted from the node 200 has CRC parity bits scrambled by the RNTI added thereto.

[0022] The MAC layer performs data priority control and retransmission processing using hybrid ARQ (HARQ), etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the node 200 via a transport channel. The MAC layer of the node 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resources to be allocated to the UE 100.

[0023] The RLC layer transmits data to the RLC layer on the receiving side by using the functions of the MAC layer and the PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the node 200 via logical channels.

[0024] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0025] The SDAP layer performs mapping between an IP flow, which is a unit for QoS control by the CN 20, and a radio bearer, which is a unit for QoS control by an AS (Access Stratum). Note that if the RAN is connected to the EPC, the SDAP is not necessary.

[0026] FIG. 3 is a diagram showing an example of the configuration of a protocol stack of a C-plane wireless interface that handles signaling (control signals).

[0027] The protocol stack of the C-plane radio interface has, for example, a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) layer instead of the SDAP layer shown in FIG.

[0028] Between the RRC layer of the UE 100 and the RRC layer of the node 200, RRC signaling for various settings is transmitted. The RRC layer controls logical channels, transport channels, and physical channels in response to establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of the UE 100 and the RRC of the node 200, the UE 100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of the UE 100 and the RRC of the node 200, the UE 100 is in an RRC idle state. When the connection between the RRC of the UE 100 and the RRC of the node 200 is suspended, the UE 100 is in an RRC inactive state.

[0029] The NAS layer (also simply referred to as "NAS") located above the RRC layer performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of UE 100 and the NAS layer of CN device 300. Note that UE 100 has an application layer and the like in addition to the radio interface protocol. Also, the layer below the NAS layer is referred to as the AS layer (also simply referred to as "AS").

[0030] FIG. 4 is a diagram showing a general procedure for transmitting a Physical Uplink Shared Channel (PUSCH) in a non-codebook manner.

[0031] In step S10, the node 200 transmits a resource configuration of an SRS (sounding reference signal) to the UE 100. The UE 100 receives the resource configuration of the SRS. The resource configuration sets resources (frequency, time, antenna port) of the SRS.

[0032] In step S20, the node 200 transmits the CSI-RS to the UE 100. The UE 100 receives the CSI-RS.

[0033] In step S30, the UE 100 measures the resource of the CSI-RS transmitted in step S20. The UE 100 calculates a precoder to be used for transmitting the SRS based on the measurement of the resource of the CSI-RS.

[0034] In step S40, UE 100 applies the calculated precoder and transmits up to four SRSs to node 200. The SRS resources set by the resource configuration received in step S10 are used for transmitting these SRSs. In addition, one SRS antenna port is set for the SRS resources of each SRS.

[0035] In step S50, the node 200 determines, based on the received SRS, one or more SRS Resource Indicators (SRIs) corresponding to a precoder to be used for transmitting the PUSCH.

[0036] In step S60, the node 200 transmits the determined one or more SRIs to the UE 100. Here, the one or more SRIs are transmitted by being included in downlink control information (DCI) transmitted on a physical downlink control channel (PDCCH). Here, the one or more SRIs are stored in an SRS resource indicator area included in the DCI. The UE 100 receives the one or more SRIs. In addition, in the non-codebook type transmission method, the node 200 does not notify a TRI (Transmit Rank Indicator), but the UE 100 determines the TRI from the number of SRIs.

[0037] In step S70, the UE 100 transmits the PUSCH to the node 200 using the same antenna port as the antenna port of the SRS. The antenna port of the SRS is indicated by one or more received SRIs. As a result, the same precoder as that of the SRS of the SRS resource indicated by the received SRI is applied to the transmission of the PUSCH.

[0038] According to such a procedure, two round trips of communication are made between the node 200 and the UE 100 from when the node 200 transmits the CSI-RS to the UE 100 until the node 200 receives the PUSCH to which the precoder is applied. This causes a problem that the precoder may not be optimal, especially in an environment where the propagation channel fluctuates drastically. As a result, the throughput may decrease due to increased inter-stream interference and deterioration in modulation accuracy.

[0039] (1.2) Example of user device configuration FIG. 5 is a diagram illustrating a configuration example of a UE 100 (user equipment) according to the embodiment.

[0040] The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 configure a wireless communication unit 140 that performs wireless communication with the node 200.

[0041] The receiving unit 110 performs various receptions under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the signal to the control unit 130. The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmitted signal) output by the control unit 130 into a radio signal and transmits the signal from the antenna.

[0042] The control unit 130 performs various controls and processes in the UE 100. The above and below described operations of the UE 100 may be operations under the control of the control unit 130. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0043] The UE 100 configured in this manner performs wireless communication with the node 200 in the mobile communication system. The receiver 110 receives a first reference signal transmitted by the node 200. The controller 130 measures a resource of the first reference signal, calculates a precoder to be used for transmitting the PUSCH based on the measurement of the resource of the first reference signal, and applies the precoder to the PUSCH. The transmitter 120 transmits the PUSCH to which the precoder has been applied to the node 200.

[0044] In this embodiment, the first reference signal is a downlink reference signal used to calculate a precoder to be applied to the transmission of the PUSCH. The first reference signal is, for example, the CSI-RS in 3GPP, but may be other reference signals such as DM-RS, PT-RS, and a new reference signal introduced in the sixth generation. In the following, an example in which the first reference signal is the CSI-RS will be described.

[0045] This allows UE 100 to transmit the PUSCH with fewer round trips in communication than in the procedure of Fig. 4. By reducing the number of round trips in communication, UE 100 can suppress a decrease in throughput due to an increase in inter-stream interference and a deterioration in modulation accuracy, even in an environment in which the propagation channel fluctuates drastically.

[0046] Also, in this embodiment, the control unit 130 determines the number of layers of the PUSCH based on the measurement of the resource of the first reference signal. Also, in this embodiment, the control unit 130 calculates a precoder used for transmitting the second reference signal based on the measurement of the resource of the first reference signal, selects an antenna port of the determined number of layers of the PUSCH from the antenna ports of the second reference signal, and uses the selected antenna port of the number of layers for transmitting the PUSCH. As a result, a part of the precoder applied to the transmission of the second reference signal, which is used for the second reference signal of the selected antenna port, is used for transmitting the PUSCH.

[0047] In this embodiment, the second reference signal is an uplink reference signal used by the node 200 to receive the PUSCH. The second reference signal is, for example, a sounding reference signal (SRS) in 3GPP, but may be other reference signals such as DM-RS, PT-RS, and new reference signals introduced in the sixth generation. In the following, an example in which the second reference signal is an SRS will be described.

[0048] (1.3) Node configuration example FIG. 6 is a diagram illustrating a configuration example of a node 200 (base station, gNB) according to the embodiment.

[0049] The node 200 includes a transmitting unit 210, a receiving unit 220, a control unit 230, and a NW communication unit 240. The transmitting unit 210 and the receiving unit 220 configure a wireless communication unit 250 that performs wireless communication with the UE 100.

[0050] The transmitting unit 210 performs various transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna. The receiving unit 220 performs various receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (reception signal) and outputs it to the control unit 230.

[0051] The control unit 230 performs various controls and processes in the node 200. The operations of the node 200 described above and below may be operations under the control of the control unit 230. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0052] The NW communication unit 240 is connected to adjacent nodes via an inter-node interface. The NW communication unit 240 is connected to the CN device 300 via a node-CN interface.

[0053] Node 200 configured in this manner performs wireless communication with UE 100 in a mobile communication system. Transmitting unit 210 transmits a first reference signal to UE 100. Receiving unit 220 receives a PUSCH from UE 100. The PUSCH is a PUSCH transmitted by UE 100 by applying a precoder calculated based on measurement of a resource of the first reference signal.

[0054] (1.4) System operation example Fig. 7 is a diagram showing an example of a system operation according to the first embodiment. The system operation according to the first embodiment is a method of transmitting a PUSCH to which a UE-determined precoder is applied, that is, a method of transmitting a PUSCH to which a precoder determined by a UE 100 is applied. Note that a duplicated description of the same operation as in Fig. 4 will be omitted.

[0055] In step S110, node 200 transmits a PUSCH resource configuration and an SRS resource configuration to UE 100. Node 200 transmits the resource configuration to UE 100, for example, in an RRC layer. Note that node 200 may transmit the resource configuration to UE 100 in a MAC layer, or may transmit the resource configuration to UE 100 by including it in DCI. UE 100 receives the PUSCH resource configuration and the SRS resource configuration.

[0056] In step S120, the node 200 transmits the CSI-RS to the UE 100. The UE 100 receives the CSI-RS. Note that node 200 may transmit CSI-RS to UE 100 before transmitting the above-described PUSCH resource configuration and SRS resource configuration. That is, the order in which the process of step S120 and the process of step S110 are performed may be reversed from the order shown in FIG.

[0057] In step S130, the UE 100 measures the resource of the CSI-RS transmitted in step S120. The UE 100 calculates a precoder to be applied to the transmission of the PUSCH and the SRS based on the measurement of the resource of the CSI-RS. The UE 100 determines the number of layers of the PUSCH based on the measurement of the resource of the CSI-RS.

[0058] The method by which UE 100 calculates the precoder to be applied to the transmission of PUSCH and SRS based on the measurement of the CSI-RS resource is, for example, a method based on singular value decomposition. UE 100 expresses the result of the measurement of the CSI-RS resource as a matrix having rows of the number of antenna ports of node 200 and columns of the number of antenna ports of UE 100 (maximum number of layers of PUSCH). UE 100 performs singular value decomposition on the matrix. UE 100 determines whether the magnitude of a singular value obtained by the singular value decomposition is greater than a predetermined threshold. UE 100 determines that a beam is transmittable when the magnitude of the singular value is greater than a predetermined threshold. An eigenvector corresponding to a singular value determined to be transmittable corresponds to a precoder weight of a beam (layer) determined to be transmittable, and the number of the eigenvectors corresponds to the number of transmittable layers. Note that the method by which UE 100 calculates a precoder to be applied to transmission of PUSCH based on the measurement of the resource of CSI-RS is not limited to the method based on singular value decomposition, and other methods may be used.

[0059] In step S140, UE 100 transmits the PUSCH to which the calculated precoder has been applied, to node 200. Node 200 receives the PUSCH. Note that the time when UE 100 transmits the PUSCH to node 200 is scheduled, for example, by DCI. Also, UE 100 transmits the PUSCH to node 200 by using the resource set in the resource configuration of the PUSCH received from node 200 in step S110.

[0060] The UE 100 may transmit the SRS to the node 200 before transmitting the PUSCH to the node 200. The UE 100 transmits the SRS to the node 200 using SRS resources for at least the number of layers described above. The UE 100 selects an antenna port for the determined number of layers of the PUSCH from the antenna ports of the SRS, and uses the selected antenna port for transmitting the PUSCH. As a result, the PUSCH for the above number of layers is transmitted to the node 200 by applying the same precoder as the precoder used for transmitting the SRS from the selected antenna port.

[0061] Note that the transmission of the SRS and the PUSCH from the UE 100 to the node 200 in step S140 may be executed multiple times before the processing from step S110 to step S130 is executed next time. Also, the number of times that the SRS and the PUSCH are transmitted may not be the same.

[0062] Here, in this embodiment, TDD (Time Division Duplex) is assumed in the PUSCH transmission method to which the UE-determined precoder shown in FIG. 7 is applied, that is, the PUSCH transmission method to which the precoder determined by the UE 100 is applied. The UE 100 can measure the CSI-RS received from the node 200 (i.e., can perform channel estimation). The UE 100 uses the channel reciprocity due to TDD to calculate the precoder to be used for the PUSCH transmission based on the measurement of the CSI-RS, and also determines the number of layers of the PUSCH. That is, the UE 100 has the ability to determine the precoder (beam) to be used for the PUSCH transmission. The advantage of the PUSCH transmission method to which the UE-determined precoder is applied is that the precoder to be used for the transmission can be calculated from the received signal by using the channel reciprocity due to TDD. That is, by executing a series of controls for the PUSCH transmission in the UE 100 without communicating with the node 200, the precoder can be determined in a shorter time than the conventional procedure shown in FIG. 4.

[0063] In the present embodiment, an example in which UE 100 (control unit 130) determines the number of layers of PUSCH based on the measurement of the resource of the first reference signal (CSI-RS) has been described, but the present invention is not limited to this. The number of layers of PUSCH does not have to be determined by UE 100. In this case, for example, node 200 determines the number of layers of PUSCH, and node 200 notifies UE 100 of the determined number of layers. As another example, the number of layers of PUSCH may be determined in advance, and UE 100 may store the number of layers in advance.

[0064] In the present embodiment, the UE 100 (control unit 130) calculates a precoder used for transmitting the second reference signal (SRS) based on the measurement of the resource of the first reference signal (CSI-RS), selects an antenna port for the determined number of layers of the PUSCH from the antenna ports of the second reference signal (SRS), and transmits the PUSCH using the selected antenna port, but is not limited thereto. The UE 100 may transmit the PUSCH using an antenna port other than the antenna port of the second reference signal (SRS).

[0065] (1.5) Modification of the First Embodiment With reference to Fig. 8, the modified example of the first embodiment will be described, focusing mainly on differences from the first embodiment. In the modified example of the first embodiment, when the receiver 110 receives the first information from the node 200, the transmitter 120 transmits the PUSCH by a PUSCH transmission method to which a UE-determined precoder is applied. That is, when the receiver 110 receives the first information from the node 200, the transmitter 120 applies a precoder calculated by the controller 130 based on measurement of the resource of the first reference signal to the transmission of the PUSCH. The first information is information indicating that a PUSCH transmission method to which a UE-determined precoder is applied is used to transmit the PUSCH.

[0066] Fig. 8 is a diagram showing an example of a system operation according to a modified example of the first embodiment. Note that the processes of steps S210, S230, and S240 are similar to the processes of steps S110, S130, and S140 in Fig. 7, and therefore descriptions thereof will be omitted.

[0067] In step S220, node 200 transmits CSI-RS to UE 100. The first information is included in CSI-RS. Here, the first information is included in CSI-RS means that CSI-RS based on a sequence corresponding to using a PUSCH transmission method to which a UE-determined precoder is applied for transmitting PUSCH is transmitted. That is, there are two types of CSI-RS: CSI-RS indicating that a PUSCH transmission method to which a UE-determined precoder is applied is used, and CSI-RS indicating that a PUSCH transmission method to which a UE-determined precoder is applied is not used. These two types of CSI-RS have different sequences for generating CSI-RS.

[0068] When UE 100 receives the first type of CSI-RS, it determines to use a PUSCH transmission method to which a UE-determined precoder is applied for transmitting the PUSCH, i.e., to apply a precoder determined by UE 100. On the other hand, when UE 100 receives the second type of CSI-RS, it determines not to use a PUSCH transmission method to which a UE-determined precoder is applied for transmitting the PUSCH, i.e., to use a general non-codebook type transmission method as shown in FIG.

[0069] When UE 100 determines that the first information is included in the CSI-RS, it executes the processes of steps S230 and S240. On the other hand, when UE 100 determines that the first information is not included in the CSI-RS, it executes the subsequent processes based on a general procedure (the processes after step S30 in FIG. 4) in which a precoder determined in a non-codebook type is applied and a PUSCH is transmitted.

[0070] In the modification of the first embodiment, an example of the case where the first information is included in the CSI-RS has been described, but the present invention is not limited to this. The first information may be included in the DCI transmitted from the node 200 to the UE 100, or may be transmitted in the RRC layer. In addition, the first information may be transmitted for all PUSCH transmissions transmitted thereafter, or may be transmitted for one PUSCH transmission.

[0071] Furthermore, when it is determined that the channel reciprocity between the uplink and the downlink is satisfied, the control unit 130 may use a PUSCH transmission method to which a UE-determined precoder is applied. In this case, the control unit 130 determines whether the channel reciprocity is satisfied, for example, as follows. For example, when Time Division Duplex (TDD) is used as a communication method and the frequencies of the uplink and the downlink are the same or the difference is within a threshold, the control unit 130 determines that the channel reciprocity is satisfied. As another example, the control unit 130 determines that the channel reciprocity is satisfied when the moving speed of the UE 100 is slow enough to realize the channel model reciprocity.

[0072] Furthermore, the control unit 130 may determine whether to use time division duplexing based on a frequency band to which a component carrier used by the UE 100 for communication with the node 200 belongs.

[0073] (2) Second embodiment With reference to FIG. 9, the second embodiment will be described mainly with respect to differences from the first embodiment. In the above-described first embodiment, the number of layers of the PUSCH transmitted by the UE 100 is not shared between the node 200 and the UE 100. Therefore, the node 200 must perform reception processing assuming the maximum number of layers. In other words, the node 200 must perform blind decoding. The node 200 knows the number of antenna ports of the node 200 itself, or the number of antenna ports of the UE 100, or the maximum number of layers in the capacity of the UE 100. However, the node 200 does not know the number of layers determined by the UE 100. Therefore, the node 200 must perform reception processing based on the number of antenna ports of the node 200 itself, or the number of antenna ports of the UE 100, or the maximum number of layers in the capacity of the UE 100. For example, even if the number of layers is 1 and transmission is performed by the UE 100, the node 200 must perform reception processing assuming the number of layers to be 8. This poses a problem that power consumption may worsen compared to when the node 200 knows the number of layers.

[0074] In this embodiment, the receiving unit 110 receives maximum layer number information from the node 200. The maximum layer number information is information indicating the maximum number of layers of the PUSCH transmitted by the transmitting unit 120. The control unit 130 controls the number of layers of the PUSCH to be equal to or less than the maximum value indicated by the maximum layer number information.

[0075] (2.1) System operation example With reference to Fig. 9, an example of system operation according to the second embodiment will be described, focusing mainly on differences from the first embodiment. Fig. 9 is a diagram showing an example of system operation according to the second embodiment. Note that the processes of steps S310, S320, and S350 are similar to the processes of steps S110, S120, and S140 in Fig. 7, and therefore descriptions thereof will be omitted.

[0076] In step S330, node 200 transmits maximum layer number information to UE 100. The maximum value of the number of layers indicated by the maximum layer number information is, for example, 2. Node 200 transmits the maximum layer number information to UE 100, for example, by including it in DCI. In 3GPP, in the case of a Codebook-type transmission method, node 200 transmits the maximum layer number information to UE 100 using a predetermined area in a predetermined format of DCI. On the other hand, in 3GPP, in a Non-codebook-type transmission method, the area is not used. Therefore, even in the transmission method of PUSCH to which a UE-determined precoder is applied, the maximum layer number information is transmitted using the area, so that DCI resources are effectively utilized.

[0077] Furthermore, the maximum number of layers information may be transmitted in the MAC layer.The maximum number of layers information may be transmitted in the RRC layer.

[0078] In the present embodiment, the maximum number of layers information is transmitted after the CSI-RS is transmitted, but is not limited to this. The maximum number of layers information may be transmitted before the CSI-RS is transmitted. That is, the process of step S330 may be performed before the process of step S320.

[0079] In addition, UE 100 (control unit 130) may use a PUSCH transmission method to which a UE-determined precoder is applied, for transmitting a PUSCH, when receiving unit 110 receives maximum layer number information from node 200. That is, UE 100 may use the maximum layer number information as the above-mentioned first information.

[0080] In step S340, UE 100 executes the process of step S130 described above while controlling the number of layers of the PUSCH to be equal to or less than the maximum value indicated by the maximum layer number information.

[0081] UE 100 controls the number of layers of PUSCH to be equal to or less than the maximum value indicated by the maximum layer number information, for example, as follows. For example, when all four singular values ​​obtained as a result of singular value decomposition are greater than a predetermined threshold, the number of layers is 4. When the number of layers is 4 according to the result of singular value decomposition, but the maximum value indicated by the maximum layer number information is 2, UE 100 sets the number of layers to 2, selects the two largest singular values ​​out of the four singular values, and selects eigenvectors corresponding to the selected singular values.

[0082] When receiving the PUSCH in step S350, node 200 performs the reception process assuming the maximum value indicated by the maximum layer number information as the number of layers.

[0083] (3) Third embodiment With reference to FIG. 10, the third embodiment will be described mainly with respect to differences from the second embodiment. In the above-mentioned second embodiment, the case where the node 200 reduces deterioration of power consumption in reception processing by transmitting maximum layer number information to the UE 100 has been described. However, according to the control of the second embodiment, even if the amount of data of the PUSCH that the UE 100 is to transmit increases and the uplink channel state improves, the number of layers cannot be made larger than the maximum value indicated by the maximum layer number information. For example, even in a situation in which the number of layers is actually 6 and PUSCH can be transmitted, if the maximum value indicated by the maximum layer number information is 4, the number of layers can only be transmitted as 4. As a result, the control of the second embodiment has a problem that the channel capacity cannot be fully utilized.

[0084] In this embodiment, the transmitting unit 120 transmits desired number of layers information to the node 200. The desired number of layers information is information indicating a desired number of layers, which is a maximum number of layers desired by the UE 100. In this embodiment, the transmitting unit 120 transmits the desired number of layers information to the node 200 when the desired number of layers is greater than the maximum value indicated by the maximum number of layers information.

[0085] (3.1) System operation example With reference to Fig. 10, an example of system operation according to the third embodiment will be described, focusing mainly on differences from the second embodiment. In Fig. 10, non-essential steps are indicated by dashed lines. Fig. 10 is a diagram showing an example of system operation according to the third embodiment. Note that the processes of steps S410, S420, S430, S440, and S450 are similar to the processes of steps S310, S320, S330, S340, and S350 in Fig. 9, and therefore descriptions thereof will be omitted.

[0086] In step S460, UE 100 transmits desired number of layers information to node 200. The desired number of layers indicated by the desired number of layers information is, for example, 4. UE 100 determines the desired number of layers, for example, as follows.

[0087] When UE 100 determines that the amount of data (buffer amount) to be transmitted using PUSCH is equal to or greater than a predetermined amount of data, UE 100 determines the desired number of layers to be a number greater than the current number of layers. In another example, UE 100 may determine the number of layers of PUSCH determined based on measurement of CSI-RS resources as the desired number of layers. In another example, UE 100 may determine the number of layers of PUSCH determined based on measurement of CSI-RS resources as the desired number of layers when UE 100 determines that the amount of data (buffer amount) to be transmitted using PUSCH is equal to or greater than a predetermined amount of data.

[0088] In step S470, node 200 again transmits the maximum number of layers information to UE 100. The maximum value of the number of layers indicated by the maximum number of layers information is, for example, 4. Here, node 200 determines the maximum number of layers based on the desired number of layers information received from UE 100. Node 200 transmits maximum number of layers information indicating the determined maximum number of layers to UE 100. Note that, instead of transmitting the maximum number of layers information again to UE 100, node 200 may transmit to UE 100 a response (ACK) indicating that the desired number of layers indicated by the desired number of layers information is permitted as the maximum number of layers.

[0089] Note that in step S460, instead of transmitting the desired number of layers, the UE 100 may transmit to the node 200 a request to increase the maximum number of layers or a request indicating the amount of increase.

[0090] The processes of steps S460 and S470 may be executed before the process of step S440, or before the process of step S450.

[0091] In step S480, UE 100 determines the number of layers based on the maximum number of layers information retransmitted from node 200 or the desired number of layers, and transmits PUSCH and SRS to node 200. If the maximum number of layers information is transmitted from node 200 to UE 100 in step S470, UE 100 determines the number of layers based on the maximum number of layers information. If a response indicating that the desired number of layers indicated by the desired number of layers information is permitted is transmitted to UE 100 in step S470, UE 100 determines the desired number of layers as the maximum number of layers. Note that, similarly to step S450 (step S140), UE 100 transmits SRS to node 200 before transmitting PUSCH to node 200.

[0092] Node 200 performs reception processing assuming the maximum value indicated by the retransmitted maximum layer number information or the desired layer number indicated by the desired layer number information received from UE 100 as the number of layers.

[0093] Note that, after step S450 and before step S460, node 200 may retransmit CSI-RS to UE 100. When CSI-RS is retransmitted, in step S460, UE 100 may determine the number of layers of PUSCH determined based on measurement of resources of the retransmitted CSI-RS as the desired number of layers.

[0094] (4) Fourth embodiment With reference to FIG. 11, the fourth embodiment will be described mainly with respect to differences from the second embodiment. In the above-mentioned second embodiment, the case where the node 200 reduces deterioration of power consumption in the reception process by transmitting maximum layer number information to the UE 100 has been described. However, according to the control of the second embodiment, even if the amount of data of the PUSCH that the UE 100 is to transmit is reduced, or the channel state of the uplink is deteriorated, the node 200 must perform the reception process assuming the maximum value indicated by the maximum layer number information as the number of layers. As a result, the control of the second embodiment has a problem that unnecessary power consumption may occur.

[0095] In this embodiment, the transmitting unit 120 transmits the desired number of layers information to the node 200 when the desired number of layers is smaller than the maximum value indicated by the maximum number of layers information.

[0096] (4.1) System operation example With reference to Fig. 11, an example of system operation according to the fourth embodiment will be described, focusing mainly on differences from the second embodiment. In Fig. 11, non-essential steps are indicated by dashed lines. Fig. 11 is a diagram showing an example of system operation according to the fourth embodiment. Note that the processes of steps S510, S520, S530, S540, and S550 are similar to the processes of steps S310, S320, S330, S340, and S350 in Fig. 9, and therefore descriptions thereof will be omitted.

[0097] In step S560, UE 100 transmits desired number of layers information to node 200. The desired number of layers indicated by the desired number of layers information is, for example, 1. UE 100 determines the desired number of layers, for example, as follows.

[0098] When UE 100 determines that the amount of data (buffer amount) to be transmitted using PUSCH is equal to or less than a predetermined amount of data, UE 100 determines the desired number of layers to be a number smaller than the current number of layers. In another example, UE 100 may determine the number of layers of PUSCH determined based on the measurement of CSI-RS resources as the desired number of layers. In another example, UE 100 may determine the number of layers of PUSCH determined based on the measurement of CSI-RS resources as the desired number of layers when UE 100 determines that the amount of data (buffer amount) to be transmitted using PUSCH is equal to or less than a predetermined amount of data.

[0099] In step S570, node 200 again transmits the maximum number of layers information to UE 100. The maximum value of the number of layers indicated by the maximum number of layers information is, for example, 1. Here, node 200 determines the maximum number of layers based on the desired number of layers information received from UE 100. Node 200 transmits maximum number of layers information indicating the determined maximum number of layers to UE 100. Note that, instead of transmitting the maximum number of layers information again to UE 100, node 200 may transmit to UE 100 a response (ACK) indicating that the desired number of layers indicated by the desired number of layers information is permitted as the maximum number of layers.

[0100] Note that in step S560, instead of transmitting the desired number of layers, the UE 100 may transmit to the node 200 a request to reduce the maximum number of layers or a request indicating the amount of reduction.

[0101] The processes of steps S560 and S570 may be executed before the process of step S540, or before the process of step S550.

[0102] In step S580, UE 100 determines the number of layers based on the maximum number of layers information retransmitted from node 200 or the desired number of layers, and transmits PUSCH and SRS to node 200. If the maximum number of layers information is transmitted from node 200 to UE 100 in step S570, UE 100 determines the number of layers based on the maximum number of layers information. If a response indicating that the desired number of layers indicated by the desired number of layers information is permitted is transmitted to UE 100 in step S570, UE 100 determines the desired number of layers as the maximum number of layers. Note that, similarly to step S550 (step S140), UE 100 transmits SRS to node 200 before transmitting PUSCH to node 200.

[0103] Node 200 performs reception processing assuming the maximum value indicated by the retransmitted maximum layer number information or the desired layer number indicated by the desired layer number information received from UE 100 as the number of layers.

[0104] Note that, after step S550 and before step S560, node 200 may retransmit CSI-RS to UE 100. When CSI-RS is retransmitted, in step S560, UE 100 may determine the number of layers of PUSCH determined based on measurement of resources of the retransmitted CSI-RS as the desired number of layers.

[0105] (5) Fifth embodiment The fifth embodiment will be described mainly with reference to Fig. 12, focusing on differences from the second embodiment. In the above-mentioned second embodiment, the node 200 reduces deterioration of power consumption in reception processing by transmitting maximum layer number information to the UE 100. However, according to the control of the second embodiment, there is a problem that the number of layers cannot be dynamically changed.

[0106] In this embodiment, the transmitting unit 120 transmits, to the node 200, layer number information indicating the number of layers of the PUSCH.

[0107] As a result, by UE 100 dynamically changing the number of layers, it is possible to increase system capacity and reduce power consumption of node 200 even when channel conditions change rapidly in an environment where wireless communication using high frequency bands such as millimeter waves or sub-terahertz waves is used.

[0108] (5.1) System operation example With reference to Fig. 12, an example of system operation according to the fifth embodiment will be described, focusing mainly on differences from the second embodiment. In Fig. 12, non-essential steps are indicated by dashed lines. Fig. 12 is a diagram showing an example of system operation according to the fifth embodiment. Note that the processes of steps S610, S620, S630, and S660 are similar to the processes of steps S310, S320, S340, and S350 in Fig. 9, and therefore descriptions thereof will be omitted.

[0109] In step S640, UE 100 transmits layer number information to node 200. Node 200 receives the layer number information. Here, UE 100 determines the number of layers of PUSCH determined based on measurement of CSI-RS resources, for example, as the number of layers indicated by the layer number information.

[0110] In step S650, node 200 transmits a response (ACK) indicating that the layer number information has been received to UE 100. For example, node 200 may transmit the response by including it in DCI. Note that, when node 200 has not received the layer number information in step S640, node 200 may determine that the layer number indicated by the layer number information last received from UE 100 continues to be used for transmitting the PUSCH.

[0111] The processes of steps S670, S680, S690, S6100, and S6110 are similar to those of steps S620, S630, S640, S650, and S660, and therefore will not be described. Thereafter, the processes of steps S670, S680, S690, S6100, and S6110 are repeatedly executed.

[0112] In FIG. 12, an example of a case where the process consisting of step S640 and step S650 is executed once for one process of step S660 has been described. That is, an example of a case where the transmission of PUSCH and the process consisting of the transmission of layer number information and the transmission of a response indicating that the layer number information has been received correspond one-to-one has been described, but this is not limited to the above. The process consisting of step S640 and step S650 may be executed once for multiple processes of step S660. That is, multiple transmissions of PUSCH may correspond to one process consisting of the transmission of layer number information and the transmission of a response indicating that the layer number information has been received.

[0113] A modification of the fifth embodiment will be described mainly with reference to Fig. 13, focusing on differences from the fifth embodiment. In the modification of the fifth embodiment, the transmitting unit 120 transmits, to the node 200, a PUSCH including layer number information indicating the number of layers of the PUSCH to be transmitted next.

[0114] (5.2) Modification of the fifth embodiment Fig. 13 is a diagram showing an example of a system operation according to a modified example of the fifth embodiment. Note that the processes of steps S710, S720, S730, S750, and S760 are similar to the processes of steps S610, S620, S630, S670, and S680 in Fig. 12, and therefore descriptions thereof will be omitted.

[0115] In step S740, UE 100 transmits layer number information indicating the number of layers of the PUSCH to be transmitted next, to node 200, including the PUSCH to be transmitted next. The PUSCH to be transmitted next is the PUSCH transmitted by UE 100 in step S770. Similarly to step S550 (step S140), the UE 100 transmits the SRS to the node 200 before transmitting the PUSCH to the node 200.

[0116] The process of step S770 is similar to the process of step S740, and therefore the description thereof will be omitted. After that, the processes of steps S750, S760, and S770 described above are repeatedly executed.

[0117] In this modification, an example of a case where the layer number information indicating the number of layers of the PUSCH to be transmitted next is included in the transmission of the PUSCH has been described, but this is not limited thereto. The UE 100 may transmit the layer number information indicating the number of layers of the PUSCH to be transmitted next to the node 200 by including it in the transmission of the PUCCH.

[0118] A program may be provided that causes a computer (UE 100, node 200) to execute the operations according to the above-described embodiment. The program may be recorded in a computer-readable medium. Using the computer-readable medium, it is possible to install the program in a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0119] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes, etc. are possible within the scope that does not deviate from the gist of the present invention. [Explanation of symbols]

[0120] 1. Network 10…RAN 20…CN 100…UE 110...Receiving unit 120...Transmitter 130...Control unit 140...Wireless communication unit 200…node 210...Transmitter 220...Receiving unit 230...Control unit 240…Network Communications Department 250…Wireless communication section 300…CN device

Claims

1. A user equipment that performs wireless communication with a node in a mobile communication system, A receiver for receiving a first reference signal transmitted by the node; a controller configured to measure a resource of the first reference signal, calculate a precoder to be used for transmitting a physical uplink shared channel based on the measurement of the resource of the first reference signal, and apply the precoder to the physical uplink shared channel; a transmitter for transmitting the physical uplink shared channel to which the precoder has been applied, to the node; Equipped with the transmitter uses the precoder for transmitting the physical uplink shared channel when the receiver receives, from the node, first information indicating that the precoder is to be used for transmitting the physical uplink shared channel; The first information is included in the first reference signal. User equipment.

2. The control unit determines a number of layers of the physical uplink shared channel based on a measurement of a resource of the first reference signal. The user device of claim 1.

3. the control unit calculates a precoder to be used for transmitting a second reference signal based on the measurement of a resource of the first reference signal, selects an antenna port for the number of layers from the antenna ports of the second reference signal, and uses the selected antenna port for the number of layers for transmitting the physical uplink shared channel.

3. A user device according to claim 2.

4. When the control unit determines that channel reciprocity between an uplink and a downlink is satisfied, the control unit uses the precoder for transmitting the physical uplink shared channel. The user device of claim 1.

5. The receiving unit receives maximum layer number information indicating a maximum value of the number of layers to be transmitted by the transmitting unit from the node, The control unit controls the number of layers to be equal to or less than a maximum value indicated by the maximum layer number information.

3. A user device according to claim 2.

6. The control unit uses the precoder for transmission of the physical uplink shared channel when the receiving unit receives the maximum layer number information from the node. A user device according to claim 5.

7. The transmitting unit transmits to the node desired layer number information indicating a desired layer number, which is a desired maximum number of layers. A user device according to claim 5.

8. The transmission unit transmits the desired number of layers information to the node when the desired number of layers is greater than the maximum value indicated by the maximum number of layers information.

8. A user device according to claim 7.

9. The transmission unit transmits the desired number of layers information to the node when the desired number of layers is smaller than the maximum value indicated by the maximum number of layers information.

8. A user device according to claim 7.

10. The transmission unit transmits layer number information indicating the number of layers to the node.

3. A user device according to claim 2.

11. The transmitting unit transmits, to the node, the layer number information indicating the number of layers of the physical uplink shared channel to be transmitted next, including the layer number information in the physical uplink shared channel.

11. A user device according to claim 10.

12. A node that performs wireless communication with a user device in a mobile communication system, A transmitter that transmits a first reference signal to the user equipment; a receiving unit configured to receive, from the user equipment, a physical uplink shared channel transmitted by applying a precoder calculated based on measurement of a resource of the first reference signal; Equipped with The first information indicating that the precoder is used for transmitting the physical uplink shared channel is included in the first reference signal. node.

13. A communication method for use in a user equipment that performs wireless communication with a node in a mobile communication system, comprising: receiving a first reference signal transmitted by the node; measuring a resource of the first reference signal, calculating a precoder for use in transmitting a physical uplink shared channel based on the measurement of the resource of the first reference signal, and applying the precoder to the physical uplink shared channel; transmitting the precoded physical uplink shared channel to the node; having the transmitting step includes, when first information indicating that the precoder is to be used for transmitting the physical uplink shared channel is received from the node in the receiving step, using the precoder for transmitting the physical uplink shared channel; The first information is included in the first reference signal. Communication methods.

14. A communication method used in a node that performs wireless communication with a user device in a mobile communication system, comprising: transmitting a first reference signal to the user equipment; receiving, from the user equipment, a physical uplink shared channel to which a precoder calculated based on measurement of a resource of the first reference signal is applied; having The first information indicating that the precoder is used for transmitting the physical uplink shared channel is included in the first reference signal. Communication methods.

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