Radio communication system and control method therefor

Abstract

To reduce a processing time of beam management in an environment where communications are performed with a plurality of base station antennas.SOLUTION: In a radio communication system, user equipment (UE) is configured connectable with a base station (BS) via a plurality of base station antennas (APs). Each of the plurality of APs transmits a downlink reference signal (DL_RS) periodically. In a case where it is determined that a signal quality of a received DL_RS is lower than a predetermined quality, the UE transmits a beam management (BM) implementation instruction with the UE to a first AP that transmits the DL_RS. Each of the plurality of APs other than the first AP transmits a non-periodic DL_RS based on transmitting the BM implementation instruction from the UE to the first AP. In a case where it is determined that a signal quality of the received non-periodic DL_RS is lower than the predetermined quality, the UE transmits the BM implementation instruction with the UE to a second AP that transmits the non-periodic DL_RS.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] The present invention relates to beam control in wireless communication systems. [Background technology]

[0002] Currently, the Third Generation Partnership Project (3GPP (registered trademark)) is continuing to develop 5G, and Beyond5G and 6G (B5G / 6G) are being studied. In 5G communication, control for optimizing beams called beam management (BM) is performed between the base station (gNB) and the user equipment (UE). However, since BM is performed using a reference signal periodically transmitted from the base station, there is an issue that processing delay occurs when massive MIMO (mMIMO) is used. Non-Patent Document 1 proposes "UE-initiated BM" as a method for shortening the time required for BM, in which the UE triggers the operation of BM. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] MediaTek Inc., "MIMO Enhancements", 3GPP TSG RAN Rel19 Workshop RWS-230117, June 2023 Summary of the Invention [Problem to be solved by the invention]

[0004] In B5G / 6G, the application of mMIMO, which links multiple base station antennas (APs) to each UE, is being considered in order to achieve more comfortable wireless communication. In this case, the UE needs to perform BM with each of the multiple APs, and it is expected that further processing delays will occur. In addition, when the technology described in Non-Patent Document 1 is applied to BM with each of the multiple APs, there is a problem that it takes a long time to complete BM with multiple APs when recovering from beam failure (Beam Failure Recovery).

[0005] The present invention has been made in consideration of such problems, and aims to provide a technique for reducing the processing time of beam management in an environment in which communication is performed with multiple base station antennas. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, a wireless communication system according to the present invention has the following configuration. That is, in a wireless communication system configured so that a user equipment (UE) can be connected to a base station (BS) via a plurality of base station antennas (APs), Each of the plurality of APs is configured to periodically transmit a downlink reference signal (DL_RS); The UE is configured to, when determining that a signal quality of the received DL_RS is lower than a predetermined quality, transmit a beam management (BM) execution instruction between the UE and a first AP that transmitted the DL_RS; Each of the plurality of APs other than the first AP is configured to transmit a non-periodic DL_RS based on the BM implementation instruction being transmitted from the UE to the first AP; The UE is configured to, when it determines that the signal quality of the received non-periodic DL_RS is lower than the specified quality, send a BM implementation instruction between the UE and a second AP that sent the non-periodic DL_RS. Effect of the Invention

[0007] According to the present invention, it is possible to provide a technique for reducing the processing time of beam management in an environment in which communication is performed with a plurality of base station antennas. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the configuration of a radio access network. [Diagram 2] FIG. 2 is a diagram illustrating a hardware configuration and a functional configuration of a central station. [Diagram 3] A diagram showing the hardware configuration and functional configuration of a UE. [Figure 4] 11 is a diagram for explaining the processing time of the BM when connected to a plurality of APs. FIG. [Diagram 5] FIG. 2 is a diagram illustrating an example of the operation of each device in the embodiment. [Figure 6] FIG. 2 is a signaling diagram according to an embodiment. [Figure 7] FIG. 11 is a signaling diagram in a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0010] (First embodiment) As a first embodiment of the wireless communication device according to the present invention, a user equipment (UE) configured to be capable of simultaneous communication with a plurality of base station antennas will be described below. Note that the base station antennas are called access points (AP) or transmission / reception points (TRP), but will be referred to as APs below.

[0011] <Radio access network configuration> 1 is a diagram illustrating an example of the configuration of a radio access network (RAN) 100 in a wireless communication system. This wireless communication system is a cellular communication system configured in compliance with a cellular communication standard such as the fifth generation (5G). In FIG. 1, only the RAN 100 is illustrated, and one base station (BS, gNB) 110 and multiple user equipments (UE) 120 are illustrated in a simplified manner.

[0012] The RAN 100 includes a base station 110 and one or more UEs 120. The base station 110 includes a plurality of base station antennas (APs) 112 and an aggregation station 111, and the aggregation station 111 controls the plurality of APs 112 to control communication with each UE 120. Here, each AP 112 includes an antenna with a multiple-input multiple-output (MIMO) configuration, and is capable of communication using massive MIMO (mMIMO).

[0013] The central station 111 corresponds to a CU (Central Unit) and is configured to integrally control a plurality of APs 112. Each AP 112 corresponds to a DU (Distributed Unit) and a RU (Radio Unit) and is configured to perform beam management (including control of MIMO, beamforming, etc.) according to control from the central station 111. However, the central station 111 may be configured to have some or all of the functions of the DU. As described above, the UE 120 is configured to be able to simultaneously communicate with a plurality of APs 112 and to communicate with each AP 112 using mMIMO.

[0014] <Hardware and functional configuration of the aggregation station 111> Fig. 2(a) is a diagram showing a hardware configuration of the central station 111. As described above, the central station 111 is a component of the BS 110, and corresponds to a CU. Note that Fig. 2(a) shows only the configuration particularly related to this embodiment, and other various configurations that the central station 111 may have are omitted from the illustration.

[0015] In one example, the aggregation station 111 includes a processor 201, a ROM 202, a RAM 203, a storage device 204, a first communication circuit 205, and a second communication circuit 206. The processor 201 is a computer including one or more processing circuits such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and reads and executes programs stored in the ROM 202 or the storage device 204 to perform the overall processing of the device and each process described below.

[0016] The ROM 202 is a read-only memory that stores information such as programs and various parameters related to the processes executed by the central station 111. The RAM 203 functions as a workspace when the processor 201 executes the programs, and is a random access memory that stores temporary information. The storage device 204 is, for example, a removable external storage device.

[0017] The first communication circuit 205 is a communication circuit for controlling the AP 112 and communicating with the UE 120. A part of the first communication circuit 205 may be configured as a DU and a RU. The communication between the aggregation station 111 and the UE 120 includes control plane and user plane communication, and the control plane communication includes non-access stratum (NAS) protocol and radio resource control (RRC) protocol communication. On the other hand, the second communication circuit 206 is a communication circuit for communicating with a core network (CN) (not shown). The communication between the aggregation station 111 and the CN includes control plane and user plane communication, and the control plane communication includes NAS protocol communication.

[0018] FIG. 2(b) is a diagram showing the functional configuration of the central station 111. The central station 111 has, for example, a first communication control unit 211, a second communication control unit 212, a control unit 213, and a storage unit 214 as its functions. Note that FIG. 2(b) shows only the configuration particularly related to this embodiment, and other various functions that the central station 111 may have are omitted. The functional blocks in FIG. 2(b) are shown in a schematic manner, and each functional block may be integrated and realized, or may be further subdivided. Each function in FIG. 2(b) may be realized, for example, by the processor 201 executing a program stored in the ROM 202 or the storage unit 204. Each function may be realized, for example, by a processor present inside the first communication circuit 205 or the second communication circuit 206 executing predetermined software.

[0019] The first communication control unit 401 controls wireless communication via the first communication circuit 205. Specifically, it controls the AP 112 to communicate with the UE 120, and controls the execution of control plane and user plane communications with the UE. The second communication control unit 402 controls communication via the second communication circuit 206. That is, it executes control plane and user plane communications with the CN.

[0020] Each AP 112 performs control plane and user plane communication with the UE 120 based on control via the first communication control unit 401. In particular, this embodiment is characterized in that the above-mentioned BM (including control of MIMO, beamforming, etc.) is performed by communication of the RRC protocol, which is control plane communication in the RAN section. The details will be described later with reference to Figs. 6 and 7, but the AP 112 is configured to transmit a downlink reference signal (DL_RS) periodically. In addition, when a BM request (BM_Request) is received from the UE 120 or a downlink reference signal request (DL_RS_Request) is received from the aggregation station 111, the AP 112 is configured to transmit a downlink reference signal (DL_RS) aperiodic.

[0021] The control unit 403 comprehensively controls the operation of the entire aggregation station 111 (or the entire BS 110). The storage unit 404 stores various information used when the first communication control unit 401, the second communication control unit 402, and the control unit 403 perform operations.

[0022] <Hardware Configuration and Functional Configuration of UE120> Figure 3(a) is a diagram showing the hardware configuration of UE120. Here, a smartphone is assumed as UE120, but other forms of devices (e.g., IoT devices) may also be used. Note that in Figure 3(a), only the configurations particularly related to this embodiment are shown, and other various configurations that UE120 may have are omitted from the illustration.

[0023] In one example, UE120 includes a processor 301, a ROM 302, a RAM 303, a storage device 304, a communication circuit 305, and a touch screen 306. The processor 301 is a computer including one or more processing circuits such as a general-purpose CPU (Central Processing Unit) or an ASIC (Application Specific Integrated Circuit), and reads and executes programs stored in the ROM 302 and the storage device 304 to execute the overall processing of the device and each of the processes described later.

[0024] The ROM 302 is a read-only memory that stores information such as programs and various parameters related to the processing executed by UE120. The RAM 303 functions as a workspace when the processor 301 executes a program and is a random access memory that stores temporary information. The storage device 304 is constituted by, for example, a removable external storage device or the like.

[0025] The communication circuit 305 is constituted by a circuit for wireless communication conforming to a predetermined communication standard. In the following description, as the predetermined communication standard, the 5G standard, particularly mMIMO, is taken as an example for explanation, but any communication standard used in the system configuration as shown in Figure 1 can be applied.

[0026] The touch screen 306 is, for example, a touch panel display, and is a component that combines a display unit for providing information to the user and a reception unit for receiving instructions from the user through touch operations.

[0027] Fig. 3(b) is a diagram showing a functional configuration of the UE 120. The UE 120 has, as its functions, for example, a communication control unit 311, an information processing unit 312, a control unit 313, and a storage unit 314. Note that Fig. 3(b) shows only the configuration particularly related to the present embodiment, and various other functions that the UE 120 may have are omitted from the illustration. For example, if the UE 120 is a smartphone, it naturally has other functions such as various input functions (touch panel, GPS receiver, camera, microphone) and various output functions (display, vibration, speaker, etc.).

[0028] Moreover, the functional blocks in Fig. 3(b) are shown in a schematic manner, and each functional block may be realized as an integrated unit, or may be further subdivided. Each function in Fig. 3(b) may be realized, for example, by the processor 301 executing a program stored in the ROM 302 or the storage device 304. Each function may also be realized, for example, by a processor present in the communication circuit 305 executing predetermined software.

[0029] The communication control unit 311 controls wireless communication via the communication circuit 305. Specifically, it controls the execution of control plane and user plane communication with the BS 110 (the aggregation station 111 and one or more APs 112). In particular, this embodiment is characterized in that the above-mentioned BM is performed by RRC protocol communication, which is control plane communication in the RAN section. In addition, when the information processing unit 312 determines that the quality of the wireless connection with one or more currently connected APs 112 has deteriorated, it transmits a BM request (BM_Request) to the AP to trigger the execution of BM. Furthermore, although not described in detail here, the communication control unit 311 performs initial access to connect (attach) to the BS 110 and executes handover to another BS 110 according to a standard.

[0030] The information processing unit 312 executes various processes based on requests from the communication control unit 311. For example, it generates a measurement (reception result) report for DL_RS received from AP112 by the communication control unit 311 and transmits it to the AP via the communication control unit 311. Also, it determines whether to transmit a BM request (BM_Request) to AP112 based on the reception result of DL_RS and notifies the communication control unit 311.

[0031] The control unit 313 comprehensively controls the operations of the entire UE120. The storage unit 314 stores various information used when the communication control unit 311, the information processing unit 312, and the control unit 313 perform operations.

[0032] <System Operation> First, with reference to FIG. 4, the processing time of BM in an environment where a plurality of base station antennas (APs) communicate will be described. Then, with reference to FIGS. 5 to 7, implementation examples for reducing the processing time of BM will be described. In FIGS. 4 to 7, a case where one UE is connected to four APs (AP#0 to AP#3) is shown, but a configuration where it is connected to other numbers of APs may also be used. Also, the number of APs connected per UE can vary.

[0033] <Processing Time of BM (Conventional Example)> FIG. 4 shows a conventional example of performing BM when a UE moves in a situation where one UE is connected to four APs. One UE and four APs are geographically arranged as shown in FIG. 4(a), and assume that the UE moves in the direction of AP#1. In this case, in AP#1 and AP#2, the direction of the UE with respect to the self-AP does not change and beam change is not necessary. On the other hand, in AP#0 and AP#3, since the direction of the UE with respect to the self-AP changes, beam change (= BM implementation is necessary) is required.

[0034] Each AP periodically transmits a downlink reference signal (DL_RS), and the UE controls the beams (BM) formed by each AP by feeding back information about the received DL_RS. Figure 4(b) shows a situation in which the UE receives the DL_RS periodically transmitted from each AP and performs BM individually. The following three points can be understood from Figures 4(a) and 4(b): · The BM cannot be triggered until the target AP (AP#0 in Fig. 4) transmits the DL_RS periodically. When multiple APs are affected (such as when the UE moves), it is not necessary to perform BM for all APs (in Figure 4, only AP#0 and AP#3 are required). · Must wait for periodic DL_RS from other APs.

[0035] As described above, in FIG. 4(b), in the end, BM is only required for two of the four APs (AP#0 and AP#3). However, in order to complete the BM process, a long time is required from when it is determined that BM needs to be performed (when DL_RS from AP#0 is received and it is determined that the reception state has deteriorated) until the BM is performed or completed (when Confirm is received from AP#3). Most of that time is spent waiting for DL_RS to be received from each of the remaining three APs (AP#1 to AP#3).

[0036] <Outline of this embodiment> Therefore, in this embodiment, in order to shorten the waiting time for receiving DL_RS, the control shown in FIG. (S501). When the UE determines that the quality of the (periodic) DL_RS of a certain AP (AP #0 in Figure 5) has deteriorated due to the movement of the UE, for example (e.g., the signal quality is lower than a specified quality), the UE instructs the AP (AP #0 in Figure 5) to perform BM (beam update). (S502) The AP (AP#0 in FIG. 5) that has received an instruction to perform BM (beam update) from the UE performs BM with the UE. (S503). The AP (AP#0 in FIG. 5) that has received the instruction to perform BM (beam update) instructs the other APs (AP#1 to AP#3 in FIG. 5) to transmit (non-periodic) DL_RS. (S504) The other APs (AP#1 to AP#3 in FIG. 5) that have received the instruction to transmit the DL_RS transmit the (non-periodic) DL_RS while beam sweeping. (S505) The UE measures (non-periodic) DL_RS received from other APs (AP#1 to AP#3 in FIG. 5) and determines the respective reception results. (S506) The UE instructs the AP (AP#3 in FIG. 5) for which quality degradation has been determined to occur to perform BM. If there is no problem with the reception result, the UE does not instruct the AP to perform BM (=maintain the current beam).

[0037] <Sequence example> An example of a sequence in the present embodiment will be described below with reference to Fig. 6. Also, an example of a sequence in a modified example will be described with reference to Fig. 7. Note that in the explanations of Fig. 6 and Fig. 7, the operation performed by the AP means that it is performed by the aggregate station 111 or an AP controlled by the aggregate station 111.

[0038] 6 is a signaling diagram according to the present embodiment. A UE is connected to four APs (AP#0 to AP#3), and each AP periodically transmits a DL_RS (Periodic).

[0039] In S501, when the UE determines that the quality of DL_RS (Periodic) from AP#0 has deteriorated due to the movement of the UE, the UE transmits a measurement report (Report) to AP#0 and instructs the AP#0 to perform BM (BM_Request). In S502, the AP#0 performs BM with the UE.

[0040] In S503, (triggered by receipt of the above-mentioned BM implementation instruction) AP#0 instructs AP#1 to AP#3 to transmit DL_RS (Aperiodic).

[0041] In S504, AP#1 to AP#3 each transmit DL_RS (Aperiodic) while beam sweeping. Note that resources for transmitting DL_RS (Aperiodic) are configured in advance (determined and shared between the UE and APs). In S505, the UE measures the DL_RS (Aperiodic) received from AP#1 to AP#3 and determines the reception results of each.

[0042] In S506, the UE transmits a measurement report (Report) to each of AP#1 to AP#3. At this time, the UE also instructs AP#3, which has been determined to have a quality degradation, to perform BM (BM_Request). In other words, only the measurement report (Report) is transmitted to AP#1 to AP#2, which have no problems with the reception results.

[0043] Fig. 7 is a signaling diagram in the modified example. The UE is connected to four APs (AP#0 to AP#3), and each AP periodically transmits DL_RS (Periodic). The difference from Fig. 6 above is mainly in S503.

[0044] First, when a UE connects to four APs (AP#0 to AP#3), one of the APs (AP#0 in FIG. 7) notifies the UE and the other APs (AP#1 to AP#3) in advance of information regarding the physical uplink control channel (PUCCH) resources used to transmit a BM implementation instruction (BM_Request), which is then shared between the devices. Then, AP#0 to AP#3 each start monitoring the BM implementation instruction (BM_Request) transmitted from the UE.

[0045] In S501, when the UE determines that the quality of DL_RS (Periodic) from AP#0 has deteriorated due to the movement of the UE, the UE transmits a measurement report (Report) to AP#0 and instructs the AP#0 to perform BM (BM_Request). In S502, the AP#0 performs BM with the UE.

[0046] In S503-2, AP#1 to AP#3 detect the transmission of the BM implementation instruction in S501. That is, as described above, AP#1 to AP#3 know and monitor the information of the PUCCH resource used by the UE to transmit the BM implementation instruction (BM_Request), and therefore detect the transmission of the BM implementation instruction in S501.

[0047] In S504, AP#1 to AP#3 each transmit DL_RS(Aperiodic) while beam sweeping. That is, the detection in S503-2 is used as a trigger to transmit DL_RS(Aperiodic). Note that resources for transmitting DL_RS(Aperiodic) are configured in advance. In S505, the UE measures the DL_RS(Aperiodic) received from AP#1 to AP#3 and determines the reception results of each.

[0048] In S506, the UE transmits a measurement report (Report) to each of AP#1 to AP#3. At this time, the UE also instructs AP#3, which has been determined to have a quality degradation, to perform BM (BM_Request). In other words, only the measurement report (Report) is transmitted to AP#1 to AP#2, which have no problems with the reception results.

[0049] <Effects> By performing the above-mentioned control, the transmission of a BM execution instruction (BM_Request) by the UE is used as a trigger to transmit DL_RS (Aperiodic) from each AP, so there is no need to wait for DL_RS (Periodic) from each AP. In addition, it is possible to reduce the number of BM executions that do not require beam changes. As a result, the following advantages are obtained. The processing time required to check DL_RS for all APs connected to the UE and to execute BM can be reduced. -Unnecessary signaling / measurements due to unnecessary BM implementation can be prevented.

[0050] As described above, according to the first embodiment, each AP transmits DL_RS (Aperiodic) when a UE transmits a BM execution instruction (BM_Request). This makes it possible to efficiently reduce the BM processing time in an environment in which communication with multiple APs is performed.

[0051] Furthermore, the present invention will make it possible to provide, for example, a more comfortable wireless communication environment, thereby contributing to Goal 9 of the United Nations' Sustainable Development Goals (SDGs), which is to "build resilient infrastructure, promote industry, innovation and infrastructure."

[0052] The invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention. [Explanation of symbols]

[0053] 100 Radio Access Network (RAN); 110 Base Station (BS); 120 User Equipment (UE); 111 Aggregation Station; 112 Base Station Antenna (AP)

Claims

1. A wireless communication system in which a user equipment (UE) can be connected to a base station (BS) via a plurality of base station antennas (APs), Each of the plurality of APs is configured to periodically transmit a downlink reference signal (DL_RS); The UE is configured to transmit a beam management (BM) execution instruction between the UE and a first AP that transmitted the DL_RS when the UE determines that the signal quality of the DL_RS received is lower than a predetermined quality, Each of the plurality of APs other than the first AP is configured to transmit a non-periodic DL_RS based on the BM implementation instruction being transmitted from the UE to the first AP; When the UE determines that the signal quality of the received non-periodic DL_RS is lower than the predetermined quality, the UE is configured to transmit a BM implementation instruction between the UE and a second AP that transmitted the non-periodic DL_RS.

1. A wireless communication system comprising:

2. When the UE determines that the signal quality of the received non-periodic DL_RS is equal to or higher than the predetermined quality, the UE is configured not to transmit a BM implementation instruction between the UE and a third AP that transmitted the non-periodic DL_RS.

2. The wireless communication system according to claim 1 .

3. Information regarding resources used for transmitting the non-periodic DL_RS is shared between the UE and each AP.

2. The wireless communication system according to claim 1 .

4. Each of the plurality of APs other than the first AP transmits the non-periodic DL_RS while beam sweeping.

2. The wireless communication system according to claim 1 .

5. The first AP is configured to notify the plurality of APs other than the first AP that the BM implementation instruction has been transmitted from the UE to the first AP; Each of the plurality of APs other than the first AP transmits the non-periodic DL_RS based on the notification from the first AP.

2. The wireless communication system according to claim 1 .

6. Information regarding a physical uplink control channel (PUCCH) resource used for transmitting the BM implementation instruction is shared between the UE and each AP, Each of the plurality of APs is configured to monitor the PUCCH resource.

2. The wireless communication system according to claim 1 .

7. Each of the plurality of APs other than the first AP transmits the non-periodic DL_RS based on detection of the transmission of the BM implementation instruction by monitoring the PUCCH resource.

7. The wireless communication system according to claim 6.

8. Each of the multiple APs is configured as a multiple-input multiple-output (MIMO) antenna.

2. The wireless communication system according to claim 1 .

9. The plurality of APs are configured to be controlled by a central station that operates as a central unit (CU) of the BS.

2. The wireless communication system according to claim 1 .

10. A method for controlling a wireless communication system in which a user equipment (UE) is configured to be able to connect to a base station (BS) via a plurality of base station antennas (APs), comprising: A first transmission step in which each of the plurality of APs periodically transmits a downlink reference signal (DL_RS); A first reception step in which the UE receives DL_RSs transmitted from the plurality of APs; A second transmission step in which the UE transmits a beam management (BM) execution instruction between the UE and a first AP that has transmitted a DL_RS whose signal quality is determined to be lower than a predetermined quality; A third transmission step in which, based on the BM implementation instruction being transmitted from the UE to the first AP, each of one or more APs other than the first AP included in the plurality of APs transmits a non-periodic DL_RS; A second transmission step in which the UE transmits a BM implementation instruction between the UE and a second AP that has transmitted a non-periodic DL_RS whose signal quality is determined to be lower than the predetermined quality; Includes A control method comprising:

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