Apparatus and method for controlling access to a cell

Abstract

The present disclosure provides a new solution (technology) capable of minimizing data interruption time occurring on the user equipment side while performing a normal access procedure during access between the user equipment and a cell (eg, a target cell) in a MIMO system.

Description

Technical Field

[0001] The present disclosure claims priority based on Korean Patent Application No. 10-2019-0048686, filed on Apr. 25, 2019, the entire contents of which are hereby incorporated by reference for all purposes.

[0002] The present disclosure relates to a technology for minimizing data interruption time on a User Equipment (UE) side when the UE accesses a cell in a communication system using a beamforming technology. Background Art

[0003] When communication is performed based on beamforming technology under the condition that both the transmitting device and the receiving device are equipped with multiple antennas, there are various technologies in which a gain in transmission capacity can be expected in proportion to the number of transmitting antennas and the number of receiving antennas. A representative technology thereof is multiple-input multiple-output (MIMO) technology.

[0004] In a MIMO technology communication system (hereinafter referred to as a "MIMO system"), a transmitting / receiving device that communicates based on beamforming technology transmits (sends / receives) data through the best antenna beam with the best signal quality among various directions / forms of antenna beams that can be formed by the transmitting device and the receiving device.

[0005] In addition, when there is a neighboring cell whose signal quality measured by a user equipment (UE) is higher than that of a source cell due to the movement of the UE in a mobile communication system, a handover technique is performed to cause the UE to access a target cell, thereby handing over the UE's access from the source cell to the target cell.

[0006] To briefly describe the existing handover scheme, when handover of a UE to a target cell is determined based on information reported from the UE, the source cell transmits an RRC connection reconfiguration message for performing an access procedure based on the target cell to the UE.

[0007] After receiving the RRC connection reconfiguration message, the UE interrupts the data transmission operation based on the source cell and performs an access procedure based on the target cell, starting from the random access procedure of attempting to access the target cell.

[0008] When the access procedure based on the target cell is completed, the UE may perform a data transmission operation based on the target cell.

[0009] When the existing handover scheme is applied to a MIMO system, it may take a long time for the target cell to receive a random access preamble (random access procedure starting signal) transmitted by the UE through a specific beam of the target cell by performing RX beam scanning for receiving the random access preamble based on the beamforming technology.

[0010] However, the existing handover scheme does not take into account the considerable time required for the target cell to receive the random access preamble (random access procedure start signal) of the UE.

[0011] Therefore, when the existing handover scheme is applied to the MIMO system, in the UE, the data interruption time for stopping the data transmission operation from the time when the RRC connection reconfiguration message is received to the time when the access procedure based on the target cell is completed becomes longer. Summary of the invention

[0012] Technical issues

[0013] The present disclosure aims to provide a technology capable of minimizing data interruption time on a User Equipment (UE) side while enabling a normal access procedure to be performed when connecting between the UE and a cell (eg, a target cell) in a MIMO system.

[0014] Technical Solutions

[0015] According to an embodiment of the present disclosure, a cell access control device may include: a cell inspection unit, which is configured to identify a second cell that a user equipment (UE) will access based on a measurement report received from the UE accessing a first cell; a time determination unit, which is configured to determine a sending time of a specific message, wherein the specific message is used to induce an attempt to access the second cell; and a message sending unit, which is configured to delay sending the specific message to the UE when generating the specific message, and send the specific message at the determined sending time.

[0016] Specifically, the specific message may be an RRC connection reconfiguration message which, when received by the UE, causes the UE to stop a data transmission operation based on the first cell and attempt to access the second cell, thereby performing an access procedure.

[0017] Specifically, the measurement report may include information about a specific beam having the best signal quality measured by the UE among multiple beams formed in different directions in the second cell, and the time determination unit may be configured to determine the transmission time based on physical random access channel (PRACH) configuration information identified for the second cell and information about the specific beam.

[0018] Specifically, the time determination unit can be configured to: predict a specific time at which an attempt to access the second cell is received from the UE through the specific beam based on the PRACH configuration information and information about the specific beam; and determine the sending time based on the predicted specific time.

[0019] Specifically, the predicted specific time may be a PRACH timeslot position to which resources allocated to the specific beam identified from the PRACH configuration information and a RACH opportunity (RO) previously allocated to the UE are mapped.

[0020] Specifically, the time determination unit can be configured to: after receiving the specific message, predict the processing time required to process the specific message, and send a message for attempting to access the second cell based on the performance information of the UE; and determine a time that is earlier than the predicted specific time as the sending time.

[0021] Specifically, the message sending unit may be configured to immediately send the specific message without regard to the sending time when a specific event that the signal quality of the first cell is lower than a threshold is reported from the UE while the sending of the specific message is delayed.

[0022] A cell access control method according to an embodiment of the present disclosure may include: a cell inspection step, which identifies a second cell that a user equipment (UE) will access based on a measurement report received from the UE accessing a first cell; a time determination step, which determines a sending time of a specific message based on the measurement report, wherein the specific message is generated to induce an attempt to access the second cell; and a message sending step, which delays sending the specific message to the UE when generating the specific message, and sends the specific message at the determined sending time.

[0023] Specifically, the measurement report may include information about a specific beam having the best signal quality measured by the UE among multiple beams formed in different directions in the second cell, and the time determination step may include determining the transmission time based on physical random access channel (PRACH) configuration information identified for the second cell and information about the specific beam.

[0024] Specifically, the time determination step may include: predicting a specific time at which an attempt to access the second cell is received from the UE through the specific beam based on the PRACH configuration information and information about the specific beam; and determining the sending time based on the predicted specific time.

[0025] Specifically, the predicted specific time may be a PRACH timeslot position to which resources allocated to the specific beam identified from the PRACH configuration information and a RACH opportunity (RO) previously allocated to the UE are mapped.

[0026] Specifically, the time determination step may include: after receiving the specific message, predicting the processing time required to process the specific message, and sending a message for attempting to access the second cell based on the performance information of the UE; and determining a time that is earlier than the predicted specific time as the sending time.

[0027] Specifically, the message sending step may include immediately sending the specific message without regard to the sending time when a specific event that the signal quality of the first cell is lower than a threshold is reported from the UE while the sending of the specific message is delayed.

[0028] Beneficial effects

[0029] According to an embodiment of the present disclosure, it is possible to provide an effect of minimizing the data interruption time on the UE side while performing a normal access procedure when enabling connection between a UE and a cell (eg, a target cell) in a MIMO system. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a diagram illustrating an example of a communication system environment to which the present disclosure is applied.

[0031] Figure 2 is a flow chart illustrating an embodiment in which an existing handover scheme is applied to a communication system to which the present disclosure is applied.

[0032] Figure 3 is a diagram illustrating a configuration of a cell access control apparatus according to an embodiment of the present disclosure.

[0033] Figure 4 is a flowchart illustrating an example of applying a cell access control method (scheme) according to an embodiment of the present disclosure.

[0034] Figure 5 is a flowchart illustrating an example of applying a cell access control method (scheme) according to another embodiment of the present disclosure.

[0035] Figure 6 is a control flow chart illustrating a cell access control method according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0037] Figure 1 A communication system environment to which the present disclosure is applied is shown.

[0038] The present disclosure is based on a transmission device equipped with multiple antennas and a reception device equipped with multiple antennas, and based on a Multiple Input Multiple Output (MIMO) technology for performing communication based on a beamforming technology.

[0039] In a MIMO technology communication system (hereinafter referred to as a "MIMO system"), the greatest transmission capacity gain is a diversity gain and a multiplexing gain by beamforming.

[0040] For this purpose, the beamforming technology used in the MIMO system can be divided into digital beamforming, analog beamforming, hybrid beamforming, etc.

[0041] In the case of digital beamforming, the number of formable beams is determined by the number of RF chains.

[0042] Multiple beams formed by digital beamforming can be used as a means to increase signal quality (Signal to Interference and Noise Ratio, SINR) by improving diversity at the receiving end, and can also be used for multiplexing by separating multiple receiving ends into different beams to respectively receive different signals.

[0043] Multiple beams formed by analog beamforming may be used only as a means of increasing signal quality (SINR) by improving diversity at the receiving end.

[0044] The disadvantages of digital beamforming technology, in which installation cost increases because as many RF chains as the number of antennas are required, and the disadvantages of analog beamforming technology, in which performance gain is limited, lead to the use of hybrid beamforming technology using a combination of the two beamforming technologies in MIMO systems.

[0045] In particular, a 5G mobile communication network using a high frequency band (hereinafter referred to as a "5G MIMO system") uses analog beamforming technology (single or hybrid) due to the high straightness of frequency characteristics.

[0046] In a MIMO system, a transmitting / receiving device that communicates based on beamforming technology transmits (sends / receives) data through an optimal beam with the best signal quality among various directional / form antenna beams that can be formed by the transmitting device and various directional / form antenna beams that can be formed by the receiving device.

[0047] Furthermore, in a mobile communication system, if there is a neighboring cell whose signal quality measured by the user equipment (UE) is higher than that of the source cell due to movement of the user equipment (UE), etc., a handover technique is used to switch the connection of the UE from the source cell to the target cell by allowing the UE to access the target cell.

[0048] Figure 1Handover due to movement of the UE in a MIMO system is shown.

[0049] As an exemplary embodiment only, Figure 1 A base station form (hereinafter referred to as a separate type base station) in which a base station module (eg, a central unit) and a wireless module (eg, a distributed unit) are separated and installed at a long distance among various forms of base stations is illustrated.

[0050] If UE 1, which stays in the cell of wireless module 10 (i.e., DU 10) and uses a data service through base station module 100 (i.e., CU 100) based on the cell of DU 10, moves to the cell of DU 20, there may be a time when the signal quality measured for the cell of DU 20 becomes better than the signal quality measured for the cell of DU 10 which is the source cell.

[0051] In this case, the CU 100 may enable the UE 1 to access the target cell (ie, the cell of the DU 20 ) through a series of signaling operations for handover, thereby handing over the connection of the UE 1 from the source cell to the target cell.

[0052] Figure 2 An example of applying an existing switching scheme to a MIMO communication system is shown.

[0053] For reference Figure 2 Briefly describing the existing handover scheme, the UE can use data services through the CU based on the source cell (ie, the cell of the source DU).

[0054] In addition, each DU performs TX beam scanning for transmitting a specific signal (e.g., SSB, CSI-RS, etc.) including a beam identifier of each of a plurality of beams formed by the DU based on the beamforming technology in the MIMO communication system.

[0055] Figure 2 An example is shown in which each DU (source DU or target DU) performs TX beam scanning for transmitting an SSB signal (SSB#1, #2, ... #n) including a beam identifier (e.g., SSB index) of each of a plurality of beams formed by the DU (①).

[0056] In addition, the UE measures the received specific signals (e.g., SSB, CSI-RS, etc.) and sends a measurement report MR (②) for reporting the signal quality of each beam of the neighboring cell (e.g., SINR, RSRP, PSRQ, etc.).

[0057] in this case, Figure 2A case is shown in which, as a result of the UE measuring the signal qualities of respective beams of neighboring cells (source DU and target DU), the signal quality measured for a specific beam in which the signal SSB#i of the target DU is transmitted is best.

[0058] The CU receives the measurement report MR of the UE through the source DU, and if there is a neighboring cell whose signal quality is equal to the signal quality of the source DU or higher than the signal quality of the source DU by a specific value based on the measurement report, it determines to switch so that the corresponding neighboring cell becomes the target cell (target DU) of the UE. In addition, the CU can perform a switching preparation process (③) with the target DU through signaling (target cell AU establishment request and target cell AU establishment response).

[0059] After performing the handover preparation process, the CU sends an RRC connection reconfiguration message (④) to the UE for performing an access process based on the target cell, i.e., the target DU.

[0060] In addition, the CU is allocated with resources (RACH opportunity, RO) capable of sending a random access preamble code for each UE in a wireless resource (physical random access channel, PRACH) designated for performing RX beam scanning in a physical random access channel (PRACH) period predefined for the corresponding DU connected thereto.

[0061] Therefore, the UE that receives the RRC connection reconfiguration message stops the data sending operation based on the source cell (i.e., the source DU) and sends a random access preamble code (⑥) in the RO allocated to it to start a random access procedure to attempt to access the target DU, thereby performing the access procedure based on the target DU.

[0062] In addition, in the MIMO communication system, each DU performs RX beam scanning based on the beamforming technology to receive a random access preamble.

[0063] Therefore, if Figure 2 As shown in the figure, the target DU of the target cell currently switched can allocate multiple beams to each unit resource in each PRACH time slot according to the beam mapping rules based on the physical random access channel (PRACH) configuration defined therein, and can perform RX beam scanning in units of PRACH time slots (PRACH#1, #2, ...#n).

[0064] After receiving the RRC connection reconfiguration message, the UE sends a random access preamble (random access procedure start signal) through a specific beam (e.g., a beam of SSB#i) of a target DU measured to have the best signal quality in the RO allocated thereto.

[0065] Therefore, the target DU can receive a random access preamble code (⑥) in a PRACH time slot (e.g., PRACH#j) mapped to the RO of the UE while performing RX beam scanning in units of PRACH time slots (PRACH#1, #2, ...#n), and can perform a random access process (⑦) through a random access response thereto and a series of signaling operations.

[0066] Thereafter, an access process based on the target DU can be performed through a series of signaling operations between the UE, the target DU and the CU, and if the UE sends an RRC reconfiguration completion message to the CU through the target DU, the access process can be completed so that the UE can use data services through the CU based on the target cell (i.e., the cell of the target DU).

[0067] That is to say, on the UE side, there is a data interruption time (⑤) in which the data transmission operation is interrupted from the time when the RRC connection reconfiguration message is received to the time when the access process based on the target cell is completed by sending the RRC reconfiguration completion message.

[0068] As described above, it takes a long time for a target DU, which is a target cell of handover, to receive a random access preamble (random access procedure start signal) transmitted by a UE while performing RX beam scanning.

[0069] In particular, in the case of a 5G MIMO system using analog beamforming technology (single or hybrid), the RACH period (⑧) may be longer, which prolongs the time taken to receive the random access preamble (random access process start signal) sent from the UE.

[0070] In addition, if Figure 2 As seen in , the data interruption time is the sum of the time between the UE receiving the RRC connection reconfiguration message and sending the RRC reconfiguration complete message and the time 2α caused by the delay (α) between DU and CU.

[0071] In this case, since the delay (α) between DU and CU is negligible, the data interruption time in the UE can be defined as the time between the UE receiving the RRC connection reconfiguration message and sending the RRC reconfiguration complete message.

[0072] However, the existing handover scheme does not take into account the long time required for the target cell to receive the random access preamble (random access process start signal) of the UE, so that the data interruption time of stopping the data transmission operation in the UE may be prolonged.

[0073] Therefore, the present disclosure proposes a new technical solution (hereinafter referred to as a cell access control solution) that can minimize the data interruption time on the UE side while enabling a normal access process to be performed when connecting between a UE and a cell (e.g., a target cell) in a MIMO system.

[0074] Specifically, the new cell access control solution proposed in the present disclosure can be implemented by the cell access control device described below.

[0075] Before describing it in detail, the cell access control device of the present disclosure can be implemented in a base station, and more specifically, in the case of a separate base station, can be implemented in a wireless module (e.g., DU) or a base station module (e.g., CU), or can be implemented so that the functions of the cell access control device are distributed to the wireless module (e.g., DU) and the base station module (e.g., CU).

[0076] Figure 3 The configuration of a cell access control device according to an embodiment of the present disclosure is shown.

[0077] like Figure 3 As shown in , the cell access control device 200 according to an embodiment of the present disclosure may include a cell checking unit 210 , a time determining unit 220 and a message sending unit 230 .

[0078] All or at least some of the elements of the cell access control apparatus 200 may be implemented in the form of a hardware module, a software module, or a combination of a hardware module and a software module.

[0079] Here, the software module may be understood as, for example, instructions executed by a processor that controls operations in the cell access control apparatus 200 , and these instructions may be installed into a memory in the cell access control apparatus 200 .

[0080] As a result, the cell access control device 200 according to the embodiment of the present disclosure can implement the new cell access control scheme proposed in the present disclosure through the above configuration.

[0081] Hereinafter, each element in the cell access control device 200 for implementing the solution of the present disclosure will be described in more detail.

[0082] The cell checking unit 210 may identify a second cell to be accessed by a UE having accessed a first cell based on a measurement report received from the UE.

[0083] The new cell access control scheme proposed in the present disclosure may be applicable to a dual connectivity technology supporting simultaneous connection to two or more cells and the above-mentioned handover technology.

[0084] Therefore, assuming a handover technology, the cell check unit 210 may identify a second cell (ie, a target cell) to be accessed by a UE having accessed a first cell as a source cell based on a measurement report received from the UE.

[0085] Alternatively, in the case where the dual connectivity technology is assumed, the cell check unit 210 may identify a second cell (ie, a secondary cell) to be accessed by a UE having accessed the first cell as the primary cell based on a measurement report received from the UE.

[0086] In addition, the new cell access control scheme proposed in the present disclosure can be applicable to both independent network structures and non-independent network structures.

[0087] However, hereinafter, for convenience of description, description will be made based on application of the switching technology in the same manner as the above description.

[0088] In a MIMO communication system, each DU may perform TX beam scanning for transmitting a specific signal (eg, SSB, CSI-RS, etc.) including a beam identifier of each of a plurality of beams formed by the DU based on a beamforming technology.

[0089] exist Figure 1 , each of the DUs 10 and 20 performs TX beam scanning for transmitting an SSB signal (SSB #1, #2, . . . #6) including a beam identifier (e.g., an SSB index) of each of a plurality of beams formed by the DU.

[0090] UE 1 measures corresponding specific signals (eg, SSB, CSI-RS, etc.) received from neighboring cells, and sends a measurement report MR for reporting signal quality (eg, SINR, RSRP, PSRQ, etc.) of corresponding beams of neighboring cells.

[0091] CU 100 receives a measurement report MR of UE 1 through a source DU (e.g., a cell of DU 10), and if, based on the measurement report MR, there is a neighboring cell whose signal quality is equal to or higher than that of DU 10 by a specific value (A3 event), it determines to switch so that the corresponding neighboring cell becomes the target cell of UE 1.

[0092] That is, as described above, the cell check unit 210 may identify a target cell, for example, a cell of the DU 20 to which the CU 100 has determined the handover of the UE 1.

[0093] The time determination unit 220 performs a function of determining a transmission time for a specific message for inducing an attempt to access a second cell, ie, a target cell (eg, a cell of the DU 20 ), based on the UE 1 measurement report MR.

[0094] Here, the specific message may be an RRC connection reconfiguration message which, when received by UE 1, causes the UE to stop a data transmission operation based on a first cell (eg, source cell) and attempt to access a second cell (eg, target cell) to perform an access procedure.

[0095] More specifically, if handover to a target cell (eg, a cell of DU 20) of UE 1 is determined as described above, CU 100 generates an RRC connection reconfiguration message enabling an attempt to access the target cell (eg, DU 20) thereby performing an access procedure.

[0096] The time determination unit 220 determines the transmission time of the RRC connection reconfiguration message for UE1 generated by the CU 100 as described above based on the measurement report MR of UE1.

[0097] When the above-mentioned specific message is generated, the message sending unit 230 waits to send the message to the UE 1 and then sends the message to the UE 1 at the sending time determined by the time determining unit 220 .

[0098] That is, the message sending unit 230 waits to send the RRC connection reconfiguration message generated by the CU 100 for the UE 1 as described above until the sending time determined by the time determining unit 220, and then sends the RRC connection reconfiguration message to the UE 1 at the sending time.

[0099] Hereinafter, a process of determining a transmission time of an RRC connection reconfiguration message generated for UE 1 will be described in detail.

[0100] First, the measurement report MR sent from UE 1 includes information about a specific beam having the best signal quality (e.g., SINR, RSRP, PSRQ, etc.) measured by UE 1 among multiple beams formed in different directions in the second cell, i.e., the target cell (e.g., the cell of DU20).

[0101] Specifically, UE 1 measures corresponding specific signals (eg, SSB, CSI-RS, etc.) received from neighboring cells, and sends a measurement report MR for reporting the signal quality (eg, SINR, RSRP, PSRQ, etc.) of each beam of the neighboring cells.

[0102] Therefore, the measurement report MR sent from UE 1 includes the signal quality of each beam of the neighboring cell measured by UE 1 (e.g., SINR, RSRP, PSRQ, etc.), and also includes information about a specific beam measured to have the best signal quality (e.g., SINR, RSRP, PSRQ, etc.) (e.g., SSB index or SINR / RSRP / PSRQ).

[0103] The time determination unit 220 can determine the transmission time based on the physical random access channel (PRACH) configuration information identified for the second cell (i.e., the target cell of the current handover) and the information about the specific beam identified in the measurement report MR of UE 1 (i.e., the specific beam of the target cell).

[0104] To this end, in the present disclosure, the cell access control apparatus 200 is required to learn the information of the neighboring cells (eg, SSB information and PRACH configuration information) based on the first cell (eg, DU 10).

[0105] According to an embodiment, when all or some functions of the cell access control device 200 are implemented in DUs 10 and 20, the cell access control device 200 can learn information about neighboring cells based on the first cell (e.g., DU 10), such as SSB information and PRACH configuration information, by sharing SSB information and PRACH configuration information between DUs (cells).

[0106] According to another embodiment, when the cell access control device 200 is implemented in CU 100, CU 100 can obtain information about neighboring cells, such as SSB information and PRACH configuration information, based on the first cell (e.g., DU 10) by pre-having SSB information and PRACH configuration information of the corresponding DUs 10 and 20 connected thereto.

[0107] More specifically, the time determination unit 220 can predict the specific time of receiving an access attempt from UE 1 through a specific beam in the second cell (i.e., DU 20) based on the PRACH configuration information identified for the second cell (i.e., the target cell of the current switching) and the information about the specific beam identified in the measurement report MR of UE 1 (i.e., the specific beam of DU 20).

[0108] In this case, the predicted specific time may be a PRACH slot position to which resources allocated to a specific beam identified from the PRACH configuration information of the DU 20 and a RACH opportunity (RO) previously allocated to the UE1 are mapped.

[0109] For example, if the PRACH configuration information of the target cell (i.e., DU 20) is identified, the time determination unit 220 can identify the structure of the PRACH time slot for performing RX beam scanning in units of PRACH time slots (PRACH #1, #2, ... #n) in DU 20, the beam mapping rules, and the RACH period.

[0110] Therefore, if UE 1 identifies information (eg, SSB index) about a specific beam of DU 20 having the best signal quality, the time determination unit 220 can identify a PRACH slot during which DU 20 within a RACH period can receive a random access preamble through the specific beam.

[0111] In this case, the time determination unit 220 can predict the time of the access attempt, i.e., the time of receiving the random access preamble code from UE 1 (that is, the PRACH time slot position mapped to the RACH opportunity (RO) previously allocated to UE 1 among the PRACH time slots during which DU 20 can receive the random access preamble code through a specific beam within the RACH period) as a specific time S_1.

[0112] In addition, the time determination unit 220 may determine the transmission time based on the specific time S_1 predicted as described above.

[0113] According to an embodiment, the time determination unit 220 may also determine the specific time S_1 predicted as described above as the transmission time.

[0114] According to a more detailed embodiment, in addition to predicting the specific time S_1 as described above, when a specific message (i.e., an RRC connection reconfiguration message) is received, the time determination unit 220 can predict the processing time S_2 required to process the RRC connection reconfiguration message and send a random access preamble message to the target cell (i.e., DU 20) based on the performance information of UE 1.

[0115] The CU 100 may possess the performance information of the UE through the UE capability information transmitted from the UE in a connection process with the new UE.

[0116] Therefore, since the time determination unit 220 can identify the performance information of the UE 1 from the CU 100 , the time determination unit 220 can predict the processing time S_2 of the UE 1 based thereon.

[0117] Therefore, the time determination unit 220 may determine, as the transmission time, a time that is earlier than the specific time S_1 predicted as described above by the processing time S_2 of the UE 1 predicted as described above.

[0118] The message transmission unit 230 waits for the RRC connection reconfiguration message generated by the transmission CU 100 for UE1 until the transmission time determined by predicting the specific time S_1 and the processing time S_2 in the time determination unit 220 , and then transmits the RRC connection reconfiguration message to UE1 .

[0119] Figure 4An example of applying the cell access control scheme according to an embodiment of the present disclosure to a MIMO communication system is shown.

[0120] refer to Figure 4 , UE 1 can use data services through CU 100 based on the source cell (ie, the cell of source DU 10).

[0121] In addition, in the MIMO communication system, each DU (e.g., 10 and 20) performs TX beam scanning for sending a specific signal (e.g., SSB, CSI-RS, etc.) including a beam identifier for each of the multiple beams formed therein based on the beamforming technology.

[0122] Figure 4 It is shown that each of the DUs 10 and 20 performs TX beam scanning (①) for transmitting an SSB signal (SSB #1, #2, . . . #n) including a beam identifier (eg, SSB index) for each of a plurality of beams formed therein.

[0123] In addition, UE 1 measures the received specific signals (e.g., SSB, CSI-RS, etc.) and sends a measurement report MR (②) for reporting the signal quality (e.g., SINR, RSRP, PSRQ, etc.) of the corresponding beam of the neighboring cell.

[0124] CU 100 receives the measurement report MR of UE 1, and if there is a neighboring cell (e.g., DU 20) whose signal quality is equal to or higher by a specific value than that of source DU 10 based on the measurement report (A3 event), it determines handover so that the corresponding DU 20 becomes the target cell of UE 1. In addition, CU 100 can perform a handover preparation process (③) with the target DU through signaling (target cell AU setup request and target cell AU setup response).

[0125] After performing the handover preparation procedure, CU 100 generates an RRC connection reconfiguration message to enable a target DU-based access procedure to UE 1, determines a sending time based on the specific time S_1 and processing time S_2 predicted as described above, and waits to send the RRC connection reconfiguration message until the sending time (S1).

[0126] While waiting to send the RRC connection reconfiguration message generated to be sent to the UE 1, the UE 1 may continue the data transmission operation based on the source DU 10.

[0127] In addition, the target DU 20 can allocate multiple beams to each unit resource in each PRACH time slot according to the beam mapping rule based on the PRACH configuration defined therein, and can perform RX beam scanning in units of PRACH time slots (PRACH#1, #2, ... #n).

[0128] At the sending time, CU 100 sends the RRC connection reconfiguration message waiting to be sent to UE 1 (④, S2).

[0129] In this case, since the transmission time is determined in step S1 based on the time when the random access preamble code is received from UE 1 (i.e., the specific time S_1 mapped to the RACH opportunity (RO) previously allocated to UE 1 and predicted as the position of the PRACH time slot of the target DU 20), the transmission time can be the time immediately before the RACH opportunity (RO) of UE 1, or it can be a time earlier than but very close to it.

[0130] In addition, despite the Figure 4 , it is illustrated that the CU 100 waits to send the RRC connection reconfiguration message, but the CU 100 may send the RRC connection reconfiguration message to the source DU 10 when generating it, and the source DU 10 may wait to send the RRC connection reconfiguration message.

[0131] In this case, at the transmission time, the source DU 10 sends the RRC connection reconfiguration message waiting to be sent to the UE 1.

[0132] Therefore, the UE 1 that receives the RRC connection reconfiguration message can stop the data transmission operation based on the source DU 10, and soon after, can send a random access preamble code (⑥) in the RO assigned to it to start a random access procedure for attempting to access the target DU 20, thereby performing an access procedure based on the target DU 20.

[0133] The target DU 20 can receive a random access preamble (⑥) in a PRACH time slot (e.g., PRACH #j) mapped to the RO of UE 1 while performing RX beam scanning in units of PRACH time slots (PRACH #1, #2, ... #n), can send a random access response (⑦) thereto, and can perform a random access procedure through a series of signaling operations.

[0134] Thereafter, an access procedure based on the target DU 20 may be performed through a series of signaling operations between UE 1, the target DU 20 and CU 100, and if UE 1 sends an RRC reconfiguration completion message to CU 100 through the target DU 20, the access procedure may be completed so that UE 1 may use data services through CU 100 based on the cell of the target DU 20.

[0135] UE 1 has a data interruption time (⑤) in which the data transmission operation is interrupted from when the RRC connection reconfiguration message is received to when the access procedure based on the target cell is completed by sending the RRC reconfiguration complete message.

[0136] like Figure 4 As shown in , according to the embodiments of the present disclosure, compared with the prior art of sending the RRC connection reconfiguration message immediately after the message is generated, the data interruption time in UE 1 is reduced by the time T1.

[0137] As described above, according to an embodiment of the present disclosure, a cell access control scheme is implemented so that when a connection is made between a UE and a cell (e.g., a target cell) in a MIMO system, the sending time of the RRC connection reconfiguration message sent to the UE is adjusted (maintained) taking into account the large amount of time required to receive the UE's random access preamble code (random access process start signal) through the cell's RX beam scanning.

[0138] In addition, according to a more detailed embodiment, if a specific event (e.g., an A2 event) in which the signal quality of the first cell, i.e., the source cell (e.g., the cell of DU 10) becomes lower than a threshold is reported from UE 1 while waiting to send a specific message (i.e., an RRC connection reconfiguration message), the message sending unit 230 can immediately send the RRC connection reconfiguration message to UE 1 without regard to the sending time determined by the time determination unit 220.

[0139] In the case where the channel environment between UE 1 and the source cell (eg, the cell of DU 10) rapidly deteriorates, an A2 event is reported / generated.

[0140] In the case where the channel environment between UE1 and the source cell (e.g., the cell of DU 10) deteriorates rapidly as described above, if the RRC connection reconfiguration message waits to be sent and is then sent at the sending time, the message cannot be sent to UE1 normally and the access procedure cannot be performed normally.

[0141] Therefore, in the present disclosure, if an A2 event indicating that the channel environment between UE 1 and the source cell (e.g., the cell of DU 10) is rapidly deteriorating is reported from UE 1 even while waiting to send an RRC connection reconfiguration message, the RRC connection reconfiguration message can be immediately sent to UE 1 regardless of the sending time, so that the message can be sent to UE 1 normally.

[0142] Figure 5 An example of applying a cell access control scheme according to another embodiment of the present disclosure to a MIMO system is shown.

[0143] For the sake of simplicity, the Figure 4 The description includes scanning of SSB signals (①), sending of measurement report MR of UE1 (②), execution of switching preparation procedure (③), determination of sending time of RRC connection reconfiguration message and waiting for sending (S1).

[0144] UE 1 continues the data transmission operation based on source DU 10 while waiting for the transmission of the generated RRC connection reconfiguration message to be transmitted to UE 1.

[0145] In addition, the target DU 20 allocates multiple beams to each unit resource in each PRACH time slot according to the beam mapping rule based on the PRACH configuration defined therein, and can perform RX beam scanning in units of PRACH time slots (PRACH#1, #2, ... #n).

[0146] Furthermore, the UE 1 repeats the operation of measuring each received specific signal (eg, SSB, CSI-RS, etc.) and transmitting a measurement report MR indicating the signal quality of each beam of the neighboring cell (S3).

[0147] If an A2 event report indicating that the signal quality of the source DU 10 is lower than the threshold is identified based on the measurement report, the CU 100 receiving the measurement report MR of the UE 1 immediately sends the RRC connection reconfiguration message waiting to be sent to the UE 1 even before the sending time (④, S4).

[0148] In this case, the transmission time in step S4 may be earlier than the transmission time determined in step S1.

[0149] Therefore, UE 1 receiving the RRC connection reconfiguration message can stop the data transmission operation based on the source DU 10, and can send a random access preamble code (⑥) in the RO allocated thereto to start a random access procedure for attempting to access the target DU 20, thereby performing an access procedure based on the target DU 20.

[0150] The target DU 20 can receive a random access preamble (⑥) in a PRACH time slot (e.g., PRACH #j) mapped to the RO of UE 1 while performing RX beam scanning in units of PRACH time slots (PRACH #1, #2, ... #n), can send a random access response (⑦) thereto, and can perform a random access procedure through a series of signaling operations.

[0151] Thereafter, an access procedure based on the target DU 20 may be performed through a series of signaling operations between UE 1, the target DU 20 and CU 100, and if UE 1 sends an RRC reconfiguration completion message to CU 100 through the target DU 20, the access procedure may be completed so that UE 1 may use data services through CU 100 based on the cell of the target DU 20.

[0152] UE 1 has a data interruption time (⑤) in which the data transmission operation is interrupted from when the RRC connection reconfiguration message is received to when the access procedure based on the target cell is completed by sending the RRC reconfiguration complete message.

[0153] like Figure 5 As shown in FIG. 1 , according to an embodiment of the present disclosure, compared with the prior art of sending the message immediately after generating the RRC connection reconfiguration message, the data interruption time in UE 1 is reduced by a time T2 ( <T1)。

[0154] As described above, according to an embodiment of the present disclosure, a cell access control scheme is implemented so that when a connection is made between a UE and a cell (e.g., a target cell) in a MIMO system, the sending time of the RRC connection reconfiguration message sent to the UE is adjusted (maintained) taking into account the large amount of time required to receive the UE's random access preamble code (random access process start signal) through the cell's RX beam scanning.

[0155] Therefore, according to the embodiments of the present disclosure, since the data interruption time on the UE side can be reduced by the adjustment amount of the transmission time of the RRC connection reconfiguration message, an effect of minimizing the data interruption time can be provided.

[0156] In particular, according to an embodiment of the present disclosure, when the sending time of the RRC connection reconfiguration message sent to the UE is adjusted, the processing time S_2 depending on the performance of the UE is reflected, thereby achieving the effect of being able to perform the normal access process while minimizing the data interruption time on the UE side.

[0157] In addition, according to an embodiment of the present disclosure, if the channel environment between the UE and the source cell deteriorates rapidly while maintaining the sending time of the RRC connection reconfiguration message sent to the UE, the RRC connection reconfiguration message is sent immediately, thereby achieving the effect of being able to perform a normal access process while minimizing the data interruption time on the UE side.

[0158] In the following, reference will be made to Figure 6 A cell access control method according to an embodiment of the present disclosure is described.

[0159] According to the cell access control method according to an embodiment of the present disclosure, the cell access control apparatus 200 may learn information of each cell (eg, SSB information and PRACH configuration information) by sharing information between cells or by having information of a corresponding cell (S100).

[0160] Hereinafter, for convenience of description, description will be made assuming that handover of the UE is performed.

[0161] According to the cell access control method according to an embodiment of the present disclosure, the cell access control device 200 (or CU100) determines whether an A3 event occurs based on a measurement report MR received from the UE indicating the presence of a neighboring cell whose signal quality is equal to or higher than a signal quality of a source cell of the UE (e.g., DU 10) by a specific value (S110).

[0162] According to the cell access control method according to an embodiment of the present disclosure, if it is determined that an A3 event has occurred for UE1 ("Yes" in S110), the cell access control device 200 (or CU 100) determines the handover for UE 1 and determines the target cell for performing the handover based on the measurement report MR (S120).

[0163] On the other hand, if the A3 event does not occur for UE1 ("No" in S110), or if it is impossible to determine the target cell on which switching will be performed even if the A3 event occurs ("No" in S120), the cell access control device 200 (or CU 100) cannot initiate switching of UE1, and UE1 can maintain data transmission based on the source cell (i.e., DU 10) (S115).

[0164] According to the cell access control method according to an embodiment of the present disclosure, if a target cell for switching (e.g., DU 20) is determined ("Yes" in S120), the cell access control device 200 can predict the specific time of receiving an access attempt from UE 1 through a specific beam in the second cell (i.e., DU 20) based on the PRACH configuration information identified for the target cell (i.e., DU20) and information about a specific beam identified in a measurement report MR of UE 1 (i.e., a specific beam of DU 20) (S130).

[0165] For example, if the PRACH configuration information of the target cell (i.e., DU 20) is identified, the cell access control device 200 can identify the structure of the PRACH time slot, RACH period and beam mapping rules for performing RX beam scanning in units of PRACH time slots (PRACH#1, #2, ... #n) in DU 20.

[0166] Therefore, if UE 1 identifies information (eg, SSB index) about a specific beam of DU 20 having the best signal quality, cell access control apparatus 200 may identify a PRACH slot in which DU 20 within a RACH period can receive a random access preamble through the specific beam.

[0167] In this case, the cell access control device 200 can predict the time of the access attempt, that is, the time of receiving the random access preamble code from UE 1 (that is, the PRACH time slot position mapped to the RACH opportunity (RO) previously allocated to UE 1 among the PRACH time slots during which DU 20 within the RACH period is able to receive the random access preamble code through a specific beam) as a specific time S_1.

[0168] In addition, according to the cell access control method according to an embodiment of the present disclosure, when an RRC connection reconfiguration message is received, the cell access control device 200 can predict the processing time S_2 (S140) required to process the RRC connection reconfiguration message and send a random access preamble message to the target cell (i.e., DU 20) based on the performance information of UE 1.

[0169] The CU 100 may possess the performance information of the UE through the UE capability information transmitted from the UE in a connection process with the new UE.

[0170] Therefore, since the cell access control apparatus 200 can identify the performance information of the UE 1 from the CU 100 , the cell access control apparatus 200 can predict the processing time S_2 of the UE 1 based thereon.

[0171] According to the cell access control method according to an embodiment of the present disclosure, the cell access control device 200 may determine a time earlier than the specific time S_1 predicted in step S130 by the processing time S_2 of UE1 predicted in step S140 as the sending time (S_1-S_2) (S150).

[0172] According to the cell access control method according to an embodiment of the present disclosure, the cell access control device 200 waits to send the RRC connection reconfiguration message generated by the CU 100 immediately after step S120 of determining the target cell for switching (e.g., DU 20) to the UE1 until the transmission time determined in step S150, and then sends the message to the UE1 thereafter ("Yes" in S160 and S170).

[0173] While the cell access control apparatus 200 waits for sending the generated RRC connection reconfiguration message to be sent to the UE 1, the UE may maintain data transmission based on the source cell (ie, the DU 10) (S190).

[0174] In addition, according to the cell access control method according to an embodiment of the present disclosure, if it is determined that the A2 event has occurred even before the transmission time determined in step S150 ("No" in S160), indicating that the channel environment between UE 1 and the source cell (i.e., the cell of DU 10) has rapidly deteriorated ("Yes" in S180), the cell access control device 200 immediately sends an RRC connection reconfiguration message to UE 1 regardless of the transmission time (S170).

[0175] Then, UE 1 that has received the RRC connection reconfiguration message may stop the data transmission operation based on the source cell (i.e., DU 10), and soon after, may send a random access preamble in the RO assigned thereto to start a random access procedure for attempting to access the target cell (i.e., DU 20), thereby performing an access procedure based on the target DU 20.

[0176] Thereafter, an access process based on the target DU 20 can be performed through a series of signaling operations between UE 1, the target cell (i.e., DU 20) and CU 100, and if UE 1 sends an RRC reconfiguration completion message to CU 100 through DU 20, the access process can be completed so that UE 1 can use data services through CU 100 based on the cell of DU 20.

[0177] As described above, according to an embodiment of the present disclosure, when a connection is established between a UE and a cell (e.g., a target cell) in a MIMO system, a new cell access control scheme can be implemented by adjusting the sending time of the RRC connection reconfiguration message to an optimal time that can minimize the data interruption time on the UE side.

[0178] Therefore, according to an embodiment of the present disclosure, it is possible to provide an effect of minimizing the data interruption time on the UE side while enabling a normal access procedure to be performed when a connection is made between the UE and a cell (eg, a target cell) in a MIMO system.

[0179] The cell access control method according to the embodiment of the present disclosure can be implemented in the form of program commands executed by various computer devices, and can be recorded in a computer-readable medium. The computer-readable medium may include program commands, data files, data structures, or a combination thereof. The program commands recorded on the medium may be specially designed and configured for the present disclosure, or may be known and available to technicians in the field of computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and tapes, optical media such as CD-ROMs and DVDs, magneto-optical media such as optical floppy disks, and hardware devices such as ROMs, RAMs, and flash memories that are specially configured to store and execute program instructions. Examples of program commands include high-level language codes that can be executed by a computer using an interpreter, etc., and machine language codes such as machine language codes generated by a compiler. The above-mentioned hardware devices may be configured to operate as one or more software modules to perform the operations of the present disclosure, and vice versa.

[0180] Although the present disclosure has been described in detail with reference to the above various embodiments, the present disclosure is not limited to the above embodiments, and it should be understood that the technical spirit of the present disclosure extends to the scope that any technician in the field to which the present disclosure belongs can make various changes or modifications without departing from the scope of the present disclosure claimed for protection in the appended claims.

Claims

1. A device for controlling access to a cell, the device comprising: a cell checking unit configured to identify a second cell to be accessed by a user equipment UE based on a measurement report received from the UE accessing the first cell; a time determination unit, configured to determine a sending time of a specific message, wherein the specific message is used to induce an attempt to access the second cell; as well as a message sending unit, configured to, when generating the specific message, delay sending the specific message to the UE, and send the specific message at the determined sending time, Wherein, the time determination unit is configured as follows: predicting a specific time at which an attempt to access the second cell is received from the UE through a specific beam based on physical random access channel PRACH configuration information identified for the second cell and information about a specific beam; and determining the transmission time based on the predicted specific time; When receiving the specific message, predicting the processing time required to process the specific message and sending a message for attempting to access the second cell; and determining a time earlier than the predicted specific time by the processing time as the sending time, While waiting to send the specific message, the second cell allocates multiple beams to each unit resource in each physical random access channel PRACH time slot, and performs RX beam scanning in units of PRACH time slots.

2. The device according to claim 1, wherein: The specific message is an RRC connection reconfiguration message causing the UE to stop a data transmission operation based on the first cell and attempt to access the second cell to perform an access procedure.

3. The device according to claim 1, wherein: The measurement report includes information on the specific beam having the best signal quality measured by the UE among a plurality of beams formed in different directions in the second cell.

4. The device according to claim 1, wherein: The predicted specific time is a PRACH timeslot position to which the resources allocated to the specific beam and the RACH opportunity RO allocated to the UE identified from the PRACH configuration information are mapped.

5. The device according to claim 1, wherein: The time determination unit is configured to: A message for attempting to access the second cell is sent based on the capability information of the UE.

6. The device according to claim 1, wherein: The message sending unit is configured to, when a specific event that the signal quality of the first cell is lower than a threshold is reported from the UE while the sending of the specific message is delayed, immediately send the specific message without regard to the sending time.

7. A method for controlling access to a cell in a base station, wherein: The method comprises the following steps: identifying, based on a measurement report received from a user equipment UE accessing a first cell, a second cell to be accessed by the UE; determining a time to send a specific message, the specific message being used to induce an attempt to access the second cell; and When the specific message is generated, sending the specific message to the UE is delayed, and the specific message is sent at the determined sending time, The step of determining the sending time of the specific message includes the following steps: predicting a specific time at which an attempt to access the second cell is received from the UE through a specific beam based on physical random access channel PRACH configuration information identified for the second cell and information about a specific beam, and determining the transmission time based on the predicted specific time; and When the specific message is received, predicting a processing time required to process the specific message and sending a message for attempting to access the second cell, and determining a time earlier than the predicted specific time by the processing time as the sending time, While waiting to send the specific message, the second cell allocates multiple beams to each unit resource in each physical random access channel PRACH time slot, and performs RX beam scanning in units of PRACH time slots.

8. The method according to claim 7, wherein: The measurement report includes information on the specific beam having the best signal quality measured by the UE among a plurality of beams formed in different directions in the second cell.

9. The method according to claim 7, wherein: The predicted specific time is a PRACH timeslot position to which the resources allocated to the specific beam and the RACH opportunity RO allocated to the UE identified from the PRACH configuration information are mapped.

10. The method according to claim 7, wherein: The determination includes: A message for attempting to access the second cell is sent based on the capability information of the UE.

11. The method according to claim 7, wherein: The sending includes immediately sending the specific message without regard to the sending time when a specific event in which the signal quality of the first cell is lower than a threshold is reported from the UE while the sending of the specific message is delayed.

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