User equipment

Abstract

To make it possible to suppress a decrease in throughput.SOLUTION: User equipment 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, to the node, the physical uplink shared channel with the precoder applied.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a user device.

Background Art

[0002] In New Radio (NR), which is a 5th generation (5G) standard established by the 3rd Generation Partnership Project (3GPP (registered trademark; the same shall apply hereinafter)), which is a standardization project for mobile communication systems, as methods for transmitting a Physical Uplink Shared Channel (PUSCH), Codebook type and Non-codebook type transmission methods are defined. In the Non-codebook type, a precoder determined by a node is applied to the transmission of the PUSCH.

[0003] In the Non-codebook type transmission method, there is a problem that it takes a lot of time until the precoder is applied to the PUSCH. In the Non-codebook type transmission method, after a node in a mobile communication system network (simply also referred to as a "node") transmits CSI-RS to a user equipment (UE), communication between the node and the UE is performed two-way until a PUSCH to which a precoder is applied is received.

[0004] As a result, particularly in an environment where the propagation channel fluctuates violently, the propagation channel may fluctuate greatly from the time when the precoder is calculated until the precoder is applied, and the precoder may become suboptimal. An environment where the propagation channel fluctuates violently 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 wave or sub-terahertz wave is used. In the latter wireless communication using a high frequency band, since the beam becomes sharper compared to the low frequency band, a larger channel fluctuation can occur with a slight environmental change. When the precoder becomes suboptimal, inter-stream interference may increase in the received signal and the modulation accuracy may deteriorate, resulting in a decrease in throughput.

Prior Art Documents

Non-Patent Documents

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

[0006] The user equipment according to the 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, measures a resource of the first reference signal, calculates a precoder used for transmission of a physical uplink shared channel based on the measurement of the resource of the first reference signal, a control unit that applies the precoder to the physical uplink shared channel, and a transmitting unit that transmits the physical uplink shared channel to which the precoder is applied to the node. [Brief Description of the Drawings]

[0007]

Figure 1

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Figure 7

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Embodiments for Carrying Out the Invention

[0008] 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.

[0009] (1) First Embodiment The first embodiment will be described with reference to FIGS. 1 to 7.

[0010] (1.1) Example of System Configuration FIG. 1 is a diagram showing an example of the configuration of a mobile communication system according to an embodiment. The mobile communication system according to the embodiment is a system compliant with 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.

[0011] The mobile communication system includes a network (NW) 1 and a user equipment (UE) 100. The UE 100 is a movable communication device that performs wireless communication with the NW 1. The UE 100 may be any device used by a user, 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 the sensor, a vehicle or a device provided in the vehicle (Vehicle UE), or an aircraft or a device provided in the aircraft (Aerial UE).

[0012] The NW 1 includes a radio access network (RAN) 10 and a core network (CN) 20. When the mobile communication system is a fifth-generation system (5GS: 5th Generation System), the RAN 10 is referred to as an NG-RAN (Next Generation Radio Access Network), and the CN 20 is referred to as a 5GC (5G Core Network).

[0013] The RAN 10 includes a plurality of nodes 200 (in the illustrated example, nodes 200a to 200c). The nodes 200 are interconnected via an inter-node interface. The nodes 200 are also referred to as base stations. The nodes 200 are composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally split), and the two units may be connected by a fronthaul interface. When the mobile communication system is 5GS, the node 200 is referred to as a gNB, the inter-node interface is referred to as an Xn interface, and the fronthaul interface is referred to as an F1 interface.

[0014] 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, etc. 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").

[0015] The CN 20 includes a CN device 300. The CN device 300 may include a control plane (C-plane) device corresponding to the control plane and a user plane (U-plane) device corresponding to the user plane. The C-plane device performs various mobility controls and paging for the UE 100, etc. 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 referred to as an AMF (Access and Mobility Management Function), the U-plane device is referred to as a UPF (User Plane Function), and the interface between the node 200 and the CN device 300 is referred to as an NG interface.

[0016] FIG. 2 is a diagram showing a configuration example of a protocol stack of a wireless interface of the U-plane that handles data.

[0017] The wireless interface protocol of the U-plane has, for example, a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) layer.

[0018] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Between the PHY layer of UE100 and the PHY layer of Node 200, data and control information are transmitted via a physical channel. Note that the PHY layer of UE100 receives downlink control information (DCI) transmitted on the physical downlink control channel (PDCCH) from Node 200. Specifically, UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI), and obtains the DCI that has been successfully decoded as DCI addressed to its own UE. The DCI transmitted from Node 200 has CRC parity bits scrambled by the RNTI added thereto.

[0019] The MAC layer performs priority control of data and retransmission processing by hybrid automatic repeat request (HARQ), etc. Between the MAC layer of UE100 and the MAC layer of Node 200, data and control information are transmitted via a transport channel. The MAC layer of Node 200 includes a scheduler. The scheduler determines the uplink and downlink transport formats (transport block size, modulation and coding scheme (MCS)) and the allocated resources for UE100.

[0020] The RLC layer uses the functions of the MAC layer and the PHY layer to transmit data to the RLC layer on the receiving side. Between the RLC layer of UE100 and the RLC layer of Node 200, data and control information are transmitted via a logical channel.

[0021] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0022] The SDAP layer performs mapping between an IP flow, which is a unit for QoS control by CN20, and a radio bearer, which is a unit for QoS control by the access stratum (AS). Note that when the RAN is connected to the EPC, the SDAP may not be necessary.

[0023] FIG. 3 is a diagram showing a configuration example of a protocol stack of a radio interface of a C plane that handles signaling (control signals).

[0024] The protocol stack of the radio interface of the C plane has, for example, an RRC (Radio Resource Control) layer and an NAS (Non-Access Stratum) layer instead of the SDAP layer shown in FIG. 2.

[0025] Between the RRC layer of UE100 and the RRC layer of node 200, RRC signaling for various settings is transmitted. The RRC layer controls logical channels, transport channels, and physical channels in response to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of node 200, UE100 is in the RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of node 200, UE100 is in the RRC idle state. When the connection between the RRC of UE100 and the RRC of node 200 is suspended, UE100 is in the RRC inactive state.

[0026] 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 UE100 and the NAS layer of CN device 300. Note that UE100 has an application layer, etc. in addition to the protocol of the radio interface. Also, the layer below the NAS layer is referred to as the AS layer (also simply referred to as "AS").

[0027] FIG. 4 is a diagram showing a general procedure for transmitting a physical uplink shared channel (PUSCH) by the non-codebook type.

[0028] In step S10, node 200 transmits the resource configuration of the SRS (Sounding Reference Signal) to UE100. UE100 receives the resource configuration of the SRS. With this resource configuration, the resources of the SRS (frequency, time, antenna port) are configured.

[0029] In step S20, node 200 transmits CSI-RS to UE100. UE100 receives the CSI-RS.

[0030] In step S30, UE100 measures the resources of the CSI-RS transmitted in step S20. UE100 calculates the precoder used for transmitting the SRS based on the measurement of the resources of the CSI-RS.

[0031] In step S40, UE100 applies the calculated precoder and transmits up to four SRSs to node 200. For the transmission of these SRSs, the SRS resources configured by the resource configuration received in step S10 are used. Also, one SRS antenna port is configured for each SRS resource of the SRS.

[0032] In step S50, node 200 determines one or more SRIs (SRS Resource Indicators) corresponding to the precoder used for PUSCH transmission based on the received SRS.

[0033] In step S60, node 200 transmits the determined one or more SRIs to UE100. Here, the one or more SRIs are transmitted included in the downlink control information (DCI) transmitted on the physical downlink control channel (PDCCH). Here, the one or more SRIs are stored in the area of the SRS resource indicator among the areas included in the DCI. UE100 receives the one or more SRIs. Also, in the non-codebook type transmission method, the TRI (Transmit Rank Indicator) is not notified from node 200, but UE100 determines the TRI from the number of SRIs.

[0034] In step S70, UE100 transmits PUSCH to node 200 using the same antenna port as the SRS antenna port. The SRS antenna port is indicated by one or more received SRIs. As a result, for the transmission of PUSCH, the same precoder as the SRS of the SRS resource indicated by the received SRI is applied.

[0035] According to such a procedure, after node 200 transmits CSI-RS to UE100 and before receiving the PUSCH to which the precoder is applied, two round trips of communication are performed between node 200 and UE100. As a result, there is a problem that the precoder may become suboptimal, particularly in an environment where the propagation channel fluctuates violently. As a result, the throughput may decrease due to an increase in inter-stream interference and deterioration of modulation accuracy.

[0036] (1.2) Configuration example of user equipment FIG. 5 is a diagram showing a configuration example of UE100 (user equipment) according to an embodiment.

[0037] UE100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit 140 that performs wireless communication with node 200.

[0038] 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 the wireless signal received by the antenna into a baseband signal (received signal) and outputs it 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 the baseband signal (transmitted signal) output by the control unit 130 into a wireless signal and transmits it from the antenna.

[0039] The control unit 130 performs various controls and processes in the UE 100. The operations of the UE 100 described above and below 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 a program executed by the processor and information used for 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, etc. The CPU executes a program stored in the memory to perform various processes.

[0040] The UE 100 configured as described above performs wireless communication with the node 200 in the mobile communication system. The receiving unit 110 receives the first reference signal transmitted by the node 200. The control unit 130 measures the resources of the first reference signal, calculates a precoder used for the transmission of the PUSCH based on the measurement of the resources of the first reference signal, and applies the precoder to the PUSCH. The transmitting unit 120 transmits the PUSCH to which the precoder is applied to the node 200.

[0041] In this embodiment, the first reference signal is a downlink reference signal used to calculate a precoder applied to the transmission of the PUSCH. The first reference signal may be, for example, the CSI-RS in 3GPP, but may also be other reference signals such as DM-RS, PT-RS, and new reference signals introduced in the sixth generation. Hereinafter, an example in the case where the first reference signal is CSI-RS will be described.

[0042] Thereby, the UE 100 can transmit the PUSCH with a smaller number of communication round trips than the procedure in FIG. 4. Even in an environment where the propagation channel fluctuates violently, the UE 100 can suppress the throughput from decreasing due to an increase in inter-stream interference and deterioration of modulation accuracy caused by reducing the number of communication round trips.

[0043] Also, in this embodiment, the control unit 130 determines the number of layers of the PUSCH based on the measurement of the resources 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 resources 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, among the precoders applied to the transmission of the second reference signal, the portion used for the second reference signal of the selected antenna port is used for the transmission of the PUSCH.

[0044] 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. Hereinafter, an example in the case where the second reference signal is SRS will be described.

[0045] (1.3) Configuration example of the node FIG. 6 is a diagram showing a configuration example of the node 200 (base station, gNB) according to the embodiment.

[0046] The node 200 includes a transmission unit 210, a reception unit 220, a control unit 230, and an NW communication unit 240. The transmission unit 210 and the reception unit 220 constitute a wireless communication unit 250 that performs wireless communication with the UE 100.

[0047] The transmission unit 210 performs various transmissions under the control of the control unit 230. The transmission unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a wireless signal and transmits it from the antenna. The reception unit 220 performs various receptions under the control of the control unit 230. The reception unit 220 includes an antenna and a receiver. The receiver converts a wireless signal received by the antenna into a baseband signal (reception signal) and outputs it to the control unit 230.

[0048] 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 for 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, etc. The CPU executes programs stored in the memory to perform various processes.

[0049] The NW communication unit 240 is connected to an adjacent node via a node interface. The NW communication unit 240 is connected to the CN device 300 via an interface between the node and the CN.

[0050] The node 200 configured as described above performs wireless communication with the UE 100 in a mobile communication system. The transmission unit 210 transmits a first reference signal to the UE 100. The reception unit 220 receives a PUSCH from the UE 100. The PUSCH is a PUSCH transmitted by applying a precoder calculated by the UE 100 based on the measurement of the resource of the first reference signal.

[0051] (1.4) System operation example FIG. 7 is a diagram showing an example of 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 determination precoder is applied, that is, a method of transmitting a PUSCH to which a precoder determined by the UE 100 is applied. Note that redundant descriptions for operations similar to those in FIG. 4 are omitted.

[0052] In step S110, node 200 transmits the resource configuration of PUSCH and the resource configuration of SRS to UE100. For example, node 200 transmits the resource configuration to UE100 at the RRC layer. Note that node 200 may also transmit the resource configuration to UE100 at the MAC layer, or may include the resource configuration in DCI and transmit it to UE100. UE100 receives the resource configuration of PUSCH and the resource configuration of SRS.

[0053] In step S120, node 200 transmits CSI-RS to UE100. UE100 receives CSI-RS. Note that node 200 may transmit CSI-RS to UE100 before transmitting the above-mentioned resource configuration of PUSCH and the resource configuration of SRS. That is, the execution order of the process in step S120 and the process in step S110 may be reversed from the order shown in FIG. 7.

[0054] In step S130, UE100 measures the resources of the CSI-RS transmitted in step S120. Based on the measurement of the resources of the CSI-RS, UE100 calculates the precoder applied to the transmission of PUSCH and SRS. Based on the measurement of the resources of the CSI-RS, UE100 determines the number of layers of PUSCH.

[0055] The method by which UE100 calculates a precoder applied to PUSCH and SRS transmissions based on measurements of CSI-RS resources is, for example, a method based on singular value decomposition. UE100 represents the results of measurements of CSI-RS resources as a matrix having the number of rows equal to the number of antenna ports of node 200 and the number of columns equal to the number of antenna ports of UE100 (the maximum number of layers of PUSCH). UE100 performs singular value decomposition on the matrix. UE100 determines whether the magnitude of the singular value obtained by singular value decomposition is greater than a predetermined threshold. When the magnitude of the singular value is greater than the predetermined threshold, UE100 determines that it can transmit a beam. The eigenvector corresponding to the singular value determined to be transmittable corresponds to the weight of the precoder of the beam (layer) determined to be transmittable, and the number of such eigenvectors corresponds to the number of transmittable layers. Note that the method by which UE100 calculates a precoder applied to PUSCH transmission based on measurements of CSI-RS resources is not limited to the method based on singular value decomposition, and other methods may be used.

[0056] In step S140, UE100 transmits a PUSCH to which the calculated precoder is applied to node 200. Node 200 receives the PUSCH. Note that the timing at which UE100 transmits the PUSCH to node 200 is scheduled by, for example, DCI. Also, UE100 uses the resources set in the PUSCH resource setting received from node 200 in step S110 to transmit the PUSCH to node 200.

[0057] UE100 may transmit SRS to node 200 before transmitting the PUSCH to node 200. Note that UE100 transmits SRS to node 200 using at least the SRS resources corresponding to the above-mentioned number of layers. Also, UE100 selects the antenna ports corresponding to the number of layers of the determined PUSCH from the antenna ports of SRS and uses the selected antenna ports for PUSCH transmission. Thereby, the same precoder as the precoder used for SRS transmission of the selected antenna ports is applied, and the PUSCH of the above-mentioned number of layers is transmitted to node 200.

[0058] Note that the transmission of SRS and PUSCH from UE 100 to 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 transmissions of SRS and PUSCH may not match.

[0059] Here, in the present embodiment, TDD (Time Division Duplex) is also assumed in the PUSCH transmission method applying the UE determination precoder shown in FIG. 7, that is, the PUSCH transmission method applying the precoder determined by UE 100. UE 100 can measure the CSI-RS received from node 200 (that is, channel estimation can be performed). UE 100 uses the channel reciprocity of TDD to calculate the precoder used for PUSCH transmission based on the measurement of CSI-RS, and also determines the number of layers of PUSCH. That is, UE 100 has the ability to determine the precoder (beam) used for PUSCH transmission. The advantage of the PUSCH transmission method applying the UE determination precoder is that the precoder used for transmission can be calculated from the received signal by using the channel reciprocity of TDD. That is, by executing a series of controls for PUSCH transmission in UE 100 without communicating with node 200, the precoder can be determined in a shorter time compared to the conventional procedure shown in FIG. 4.

[0060] Note that 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 it is not limited to this. The number of layers of PUSCH may not be determined by UE 100. In that 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.

[0061] Also, in this embodiment, the UE 100 (control unit 130) calculates a precoder used for transmitting the second reference signal (SRS) based on the measurement of the resources of the first reference signal (CSI-RS), selects the antenna port of the determined number of layers of the PUSCH from the antenna ports of the second reference signal (SRS), and has described an example of transmitting the PUSCH using the selected antenna port, but it 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).

[0062] (1.5) Variation of the First Embodiment Referring to FIG. 8, the differences from the first embodiment will be mainly described for the variation of the first embodiment. In the variation of the first embodiment, when the receiving unit 110 receives the first information from the node 200, the transmitting unit 120 transmits the PUSCH by the PUSCH transmission method applying the UE-determined precoder. That is, when the receiving unit 110 receives the first information from the node 200, the transmitting unit 120 applies the precoder calculated by the control unit 130 based on the measurement of the resources of the first reference signal for the transmission of the PUSCH. The first information is information indicating that the PUSCH transmission method applying the UE-determined precoder is used for the transmission of the PUSCH.

[0063] FIG. 8 is a diagram showing an example of system operation according to the variation of the first embodiment. Since the processes of steps S210, S230, and S240 are the same as the processes of steps S110, S130, and S140 in FIG. 7, the description thereof will be omitted.

[0064] In step S220, node 200 transmits CSI-RS to UE100. The first information is included in the CSI-RS. Here, the fact that the first information is included in the CSI-RS means that the CSI-RS is transmitted based on a sequence corresponding to the use of the PUSCH transmission method applying the UE-determined precoder for PUSCH transmission. That is, there are two types of CSI-RS in the CSI-RS: one indicating the use of the PUSCH transmission method applying the UE-determined precoder for PUSCH transmission, and the other indicating the non-use of the PUSCH transmission method applying the UE-determined precoder for PUSCH transmission. These two types of CSI-RS have different sequences for generating the CSI-RS.

[0065] When UE100 receives the first type of CSI-RS, it determines to use the PUSCH transmission method applying the UE-determined precoder for PUSCH transmission, that is, to apply the precoder determined by UE100. On the other hand, when UE100 receives the second type of CSI-RS, it determines not to use the PUSCH transmission method applying the UE-determined precoder for PUSCH transmission, that is, to use the general non-codebook type transmission method as shown in FIG. 4.

[0066] When UE100 determines that the first information is included in the CSI-RS, it executes the processes of step S230 and step S240 respectively. On the other hand, when UE100 determines that the first information is not included in the CSI-RS, it executes based on the general procedure (the processes after step S30 in FIG. 4) in which the precoder determined in the non-codebook type is applied for PUSCH transmission.

[0067] Note that in the modification of the first embodiment, although an example in the case where the first information is included in the CSI-RS has been described, it is not limited thereto. The first information may be included in the DCI transmitted from node 200 to UE100, or may be transmitted in the RRC layer. Also, the first information may be transmitted for all PUSCH transmissions to be transmitted later, or may be transmitted for one PUSCH transmission.

[0068] Further, when the control unit 130 determines that the channel reciprocity between the uplink and the downlink is satisfied, it may use the transmission method of the PUSCH applied with the UE determination pre - coder. In that case, the control unit 130 determines whether the channel reciprocity is satisfied as follows, for example. The control unit 130 determines that the channel reciprocity is satisfied, for example, when using time - division duplex (TDD) as the communication method and the frequencies of the uplink and the downlink are the same or the difference is within a threshold. As another example, the control unit 130 determines that the channel reciprocity is satisfied when the moving speed of the UE100 is low enough to realize the channel model reciprocity.

[0069] Further, the control unit 130 may determine whether to use time - division duplex based on the frequency band (band) to which the component carrier used by the UE100 for communication with the node 200 belongs.

[0070] (2) Second Embodiment Referring to FIG. 9, the differences between the second embodiment and the first embodiment will be mainly described. In the first embodiment described above, 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 has to perform reception processing assuming the maximum value of the number of layers. In other words, the node 200 has to perform blind decoding. The node 200 knows the number of its own antenna ports, or the number of the UE 100's antenna ports, or the maximum number of layers in terms of the UE 100's capabilities. However, the node 200 does not know the number of layers determined by the UE 100. Therefore, the node 200 has to perform reception processing based on the number of its own antenna ports, or the number of the UE 100's antenna ports, or the maximum number of layers in terms of the UE 100's capabilities. For example, even when the number of layers is 1 and transmission is performed by the UE 100, the node 200 has to perform reception processing assuming the number of layers is 8. As a result, there is a problem that the power consumption may deteriorate compared to the case where the node 200 knows the number of layers.

[0071] 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 value of the 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.

[0072] (2.1) System operation example Referring to FIG. 9, the differences between the system operation example according to the second embodiment and the first embodiment will be mainly described. FIG. 9 is a diagram showing the system operation example according to the second embodiment. Since the processes of step S310, step S320, and step S350 are the same as the processes of step S110, step S120, and step S140 in FIG. 7, the description thereof will be omitted.

[0073] In step S330, node 200 transmits the maximum layer number information to UE100. 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 UE100 by including it in, for example, DCI. In 3GPP, in the case of the codebook-based transmission method, node 200 uses a predetermined area in a predetermined format of DCI to transmit the maximum layer number information to UE100. On the other hand, in 3GPP, in the non-codebook-based transmission method, this area is not used. Therefore, even in the PUSCH transmission method applying the UE-determined precoder, since the maximum layer number information is transmitted using this area, the resources of DCI are effectively utilized.

[0074] Also, the maximum layer number information may be transmitted at the MAC layer. The maximum layer number information may be transmitted at the RRC layer.

[0075] Note that in this embodiment, the maximum layer number information is transmitted after the CSI-RS is transmitted, but it is not limited to this. The maximum layer number information may be transmitted before the CSI-RS is transmitted. That is, the process of step S330 may be executed before the process of step S320.

[0076] Note that when the receiving unit 110 of UE100 receives the maximum layer number information from node 200, UE100 (control unit 130) may use the PUSCH transmission method applying the UE-determined precoder for PUSCH transmission. That is, UE100 may use the maximum layer number information as the first information described above.

[0077] In step S340, UE100 executes the process of step S130 described above while controlling the number of layers of PUSCH to be equal to or less than the maximum value indicated by the maximum layer number information.

[0078] UE100 controls the number of layers of the PUSCH to be equal to or less than the maximum value indicated by the maximum number of layers information as follows, for example. For example, when all four singular values obtained as a result of singular value decomposition are greater than a predetermined threshold value, the number of layers is 4. According to the result of singular value decomposition, the number of layers is 4, but when the maximum value indicated by the maximum number of layers information is 2, UE100 sets the number of layers to 2, selects two singular values from the larger ones among the four singular values, and selects the eigenvectors corresponding to the selected singular values.

[0079] In addition, when receiving the PUSCH in step S350, node 200 performs reception processing assuming the maximum value indicated by the maximum number of layers information as the number of layers.

[0080] (3) Third Embodiment Referring to FIG. 10, the differences between the third embodiment and the second embodiment will be mainly described. In the second embodiment described above, node 200 has been described in the case of reducing the deterioration of power consumption in reception processing by transmitting the maximum number of layers information to UE100. However, according to the control of the second embodiment, even when the data amount of the PUSCH that UE100 attempts to transmit increases or when the uplink channel state improves, the number of layers cannot be made larger than the maximum value indicated by the maximum number of layers information. For example, even in a situation where it is actually possible to transmit the PUSCH with the number of layers set to 6, when the maximum value indicated by the maximum number of layers information is 4, it can only be transmitted with the number of layers set to 4. As a result, the control of the second embodiment has a problem that the channel capacity cannot be utilized to the maximum extent.

[0081] In this embodiment, the transmission unit 120 transmits the desired number of layers information to node 200. The desired number of layers information is information indicating the desired number of layers, which is the maximum number of layers desired by UE100. In this embodiment, the transmission unit 120 transmits the desired number of layers information to node 200 when the desired number of layers is greater than the maximum value indicated by the maximum number of layers information.

[0082] (3.1) System Operation Example Referring to FIG. 10, the system operation example according to the third embodiment will be mainly described with differences from the second embodiment. In FIG. 10, steps that are not essential are indicated by broken lines. FIG. 10 is a diagram showing the system operation example according to the third embodiment. Note that since the processes of step S410, step S420, step S430, step S440, and step S450 are the same as the processes of step S310, step S320, step S330, step S340, and step S350 in FIG. 9, the description thereof will be omitted.

[0083] In step S460, UE100 transmits the 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. UE100 determines the desired number of layers as follows, for example.

[0084] When UE100 determines that the amount of data (buffer amount) transmitted using PUSCH is equal to or greater than a predetermined amount of data, it determines the desired number of layers as a number greater than the current number of layers. In another example, UE100 may determine the number of layers of PUSCH determined based on the measurement of the resources of CSI-RS as the desired number of layers. In another example, when UE100 determines that the amount of data (buffer amount) transmitted using PUSCH is equal to or greater than a predetermined amount of data, it may determine the number of layers of PUSCH determined based on the measurement of the resources of CSI-RS as the desired number of layers.

[0085] In step S470, node 200 transmits the maximum number of layers information to UE100 again. 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 UE100. Node 200 transmits the maximum number of layers information indicating the determined maximum number of layers to UE100. Note that instead of transmitting the maximum number of layers information to UE100 again, node 200 may transmit an acknowledgment (ACK) to UE100 indicating that it permits the desired number of layers indicated by the desired number of layers information as the maximum number of layers.

[0086] Note that in step S460, instead of transmitting the desired number of layers, UE100 may increase the maximum number of layers or transmit a request indicating the increase amount to node 200.

[0087] Note that the processes of step S460 and step S470 may be executed before the process of step S440 or may be executed before the process of step S450.

[0088] In step S480, UE100 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. When the maximum number of layers information is transmitted from node 200 to UE100 in step S470, UE100 determines the number of layers based on the maximum number of layers information. When a response indicating permission for the desired number of layers indicated by the desired number of layers information is transmitted from node 200 to UE100 in step S470, UE100 determines the desired number of layers as the maximum number of layers. Note that, similar to step S450 (step S140), UE100 transmits SRS to node 200 at a time before transmitting PUSCH to node 200.

[0089] Node 200 executes reception processing assuming the maximum value indicated by the retransmitted maximum number of layers information or the desired number of layers indicated by the desired number of layers information received from UE100 as the number of layers.

[0090] Note that at a time after step S450 and before step S460, node 200 may retransmit CSI-RS to UE100. When CSI-RS is retransmitted, in step S460, UE100 may determine the number of layers of PUSCH determined based on the measurement of the resources of the retransmitted CSI-RS as the desired number of layers.

[0091] (4) Fourth Embodiment Referring to FIG. 11, the fourth embodiment will be mainly described in terms of the differences from the second embodiment. In the above-described second embodiment, the case where the node 200 reduces the deterioration of power consumption in the reception process by transmitting the maximum number of layers information to the UE 100 was described. However, according to the control of the second embodiment, even when the data amount of the PUSCH that the UE 100 attempts to transmit decreases, or when the uplink channel state deteriorates, the node 200 has to perform the reception process assuming the maximum value indicated by the maximum number of layers information as the number of layers. As a result, there is a problem that unnecessary power consumption may occur in the control of the second embodiment.

[0092] In this embodiment, when the desired number of layers is smaller than the maximum value indicated by the maximum number of layers information, the transmission unit 120 transmits the desired number of layers information to the node 200.

[0093] (4.1) System operation example Referring to FIG. 11, the system operation example according to the fourth embodiment will be mainly described in terms of the differences from the second embodiment. In FIG. 11, steps that are not essential are indicated by dashed lines. FIG. 11 is a diagram showing a system operation example according to the fourth embodiment. Note that the processes of steps S510, S520, S530, S540, and S550 are the same as the processes of steps S310, S320, S330, S340, and S350 in FIG. 9, and thus the description thereof is omitted.

[0094] In step S560, the UE 100 transmits the desired number of layers information to the node 200. The desired number of layers indicated by the desired number of layers information is, for example, 1. The UE 100 determines the desired number of layers as follows, for example.

[0095] When the UE 100 determines that the amount of data (buffer amount) transmitted using the PUSCH is equal to or less than a predetermined amount of data, the UE 100 determines the desired number of layers to be a number smaller than the current number of layers. In another example, the UE 100 may determine the number of layers of the PUSCH determined based on the measurement of the CSI-RS resource as the desired number of layers. In another example, when the UE 100 determines that the amount of data (buffer amount) transmitted using the PUSCH is equal to or less than a predetermined amount of data, the UE 100 may determine the number of layers of the PUSCH determined based on the measurement of the CSI-RS resource as the desired number of layers.

[0096] In step S570, the node 200 re-transmits the maximum number of layers information to the UE 100. The maximum value of the number of layers indicated by the maximum number of layers information is, for example, 1. Here, the node 200 determines the maximum number of layers based on the desired number of layers information received from the UE 100. The node 200 transmits the maximum number of layers information indicating the determined maximum number of layers to the UE 100. Note that instead of re-transmitting the maximum number of layers information to the UE 100, the node 200 may transmit an acknowledgment (ACK) to the UE 100 indicating that the desired number of layers indicated by the desired number of layers information is permitted as the maximum number of layers.

[0097] Note that in step S560, instead of transmitting the desired number of layers, the UE 100 may transmit a request to the node 200 to reduce the maximum number of layers or indicate the amount of reduction.

[0098] Note that the processes of step S560 and step S570 may be executed before the process of step S540 or before the process of step S550.

[0099] In step S580, UE100 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. When the maximum number of layers information is transmitted from node 200 to UE100 in step S570, UE100 determines the number of layers based on the maximum number of layers information. When a response indicating permission of the desired number of layers indicated by the desired number of layers information is transmitted from node 200 to UE100 in step S570, UE100 determines the desired number of layers as the maximum number of layers. Similar to step S550 (step S140), UE100 transmits SRS to node 200 at a time before transmitting PUSCH to node 200.

[0100] Node 200 executes reception processing assuming, as the number of layers, the maximum value indicated by the retransmitted maximum number of layers information or the desired number of layers indicated by the desired number of layers information received from UE100.

[0101] Note that, at a time after step S550 and before step S560, node 200 may retransmit CSI-RS to UE100. When CSI-RS is retransmitted, in step S560, UE100 may determine the number of layers of PUSCH determined based on the measurement of the resources of the retransmitted CSI-RS as the desired number of layers.

[0102] (5) Fifth Embodiment Referring to FIG. 12, differences from the second embodiment will be mainly described for the fifth embodiment. In the above-described second embodiment, the case where node 200 reduces the deterioration of power consumption in reception processing by transmitting the maximum number of layers information to UE100 has been described. However, according to the control of the second embodiment, there is a problem that the number of layers cannot be dynamically changed.

[0103] In this embodiment, the transmission unit 120 transmits layer number information indicating the number of layers of PUSCH to node 200.

[0104] As a result, even when the channel state changes rapidly in an environment where wireless communication using a high-frequency band such as millimeter waves or sub-terahertz waves is used by dynamically changing the number of layers in UE100, the system capacity can be increased and the power consumption of node 200 can be suppressed.

[0105] (5.1) System operation example Referring to FIG. 12, the differences from the second embodiment will be mainly described for the system operation example according to the fifth embodiment. In FIG. 12, steps that are not essential are indicated by dashed lines. FIG. 12 is a diagram showing the system operation example according to the fifth embodiment. Note that the processes of step S610, step S620, step S630, and step S660 are the same as the processes of step S310, step S320, step S340, and step S350 in FIG. 9, respectively, and thus the description thereof is omitted.

[0106] In step S640, UE100 transmits layer number information to node 200. Node 200 receives the layer number information. Here, UE100 determines, for example, the number of layers of the PUSCH determined based on the measurement of the CSI-RS resource as the number of layers indicated by the layer number information.

[0107] In step S650, node 200 transmits a response (ACK) indicating that the layer number information has been received to UE100. Node 200 may include the response in DCI and transmit it, for example. Note that if node 200 does not receive the layer number information in step S640, it may be determined that the number of layers indicated by the layer number information last received from UE100 is continuously used for PUSCH transmission.

[0108] The processes of step S670, step S680, step S690, step S6100, and step S6110 are the same as the processes of step S620, step S630, step S640, step S650, and step S660, respectively, and thus the description thereof is omitted. Hereinafter, the processes of these step S670, step S680, step S690, step S6100, and step S6110 are repeatedly executed.

[0109] Note that in FIG. 12, an example in which the process consisting of step S640 and step S650 is executed once for one execution of step S660 has been described. That is, an example in which the transmission of PUSCH corresponds one-to-one to 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 has been described, but the present invention is not limited thereto. The process consisting of step S640 and step S650 may be executed once for a plurality of executions of step S660. That is, a plurality of 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.

[0110] Referring to FIG. 13, a modification of the fifth embodiment will be mainly described in terms of differences from the fifth embodiment. In the modification of the fifth embodiment, the transmission 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 time.

[0111] (5.2) Modification of the Fifth Embodiment FIG. 13 is a diagram showing an example of system operation according to a modification of the fifth embodiment. Note that the processes of step S710, step S720, step S730, step S750, and step S760 are the same as the processes of step S610, step S620, step S630, step S670, and step S680 in FIG. 12, respectively, and thus the description thereof is omitted.

[0112] In step S740, UE100 transmits to node 200 by including layer number information indicating the number of layers of the PUSCH to be transmitted next time in the transmission of the PUSCH. The PUSCH to be transmitted next time is the PUSCH transmitted by UE100 in step S770. Similar to step S550 (step S140), UE100 transmits the SRS to node 200 at a time before transmitting the PUSCH to node 200.

[0113] Since the process of step S770 is the same as the process of step S740, the description thereof is omitted. Thereafter, each of the processes of step S750, step S760, and step S770 described above is repeatedly executed.

[0114] In addition, in this modification example, although an example in the case where layer number information indicating the number of layers of the PUSCH to be transmitted next time is included in the transmission of the PUSCH has been described, the present invention is not limited thereto. UE100 may transmit to node 200 by including layer number information indicating the number of layers of the PUSCH to be transmitted next time in the transmission of the PUCCH.

[0115] A program for causing a computer (UE100, node 200) to execute the operations according to the above-described embodiment may be provided. The program may be recorded on a computer-readable medium. By using a 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-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0116] As described above, an embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the gist of the present invention.

Description of Reference Numerals

[0117] 1... Network 10…RAN 20…CN 100…UE 110…Receiving unit 120…Transmitting unit 130…Control unit 140…Wireless communication unit 200…Node 210…Transmitting unit 220…Receiving unit 230…Control unit 240…NW communication unit 250…Wireless communication unit 300…CN device

Claims

【Claim 1】 A user device that performs wireless communication with a node in a mobile communication system, 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 used for transmission of 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, a transmitting unit that transmits the physical uplink shared channel to which the precoder is applied to the node, and a user device comprising the same.

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