Non-volatile computer-readable medium and beam search method

Abstract

To provide non-volatile computer readable media and a method for beam searching.SOLUTION: A method for beam searching suitable for user equipment (UE) is provided. The UE stores a cell ID and a synchronization signal block (SSB) of a previous network connection with base station connected previously. The method includes the following steps. A reconnection to the base station is performed. The cell ID and the SSB of the previous network connection with the previously connected base station are read. Information of the cell ID and the SSB is transmitted to a first base station via a physical random access channel (PRACH). An initial access to the first base station is performed by the UE through the cell ID and the SSB in response to the cell ID in the PRACH received by the first base station matching a preset cell ID configured by the previously connected base station.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a beam management method, and particularly to a high-speed beam search method and its communication system.

Background Art

[0002] The beam management process is used to acquire and maintain a set of beams that can be used for transmission and reception at a transmission and reception point (TRxP) and / or a user equipment (UE) in the downlink (DL) and uplink (UL) of 5G New Radio (NR) Frequency Range 2 (FR2). The beam management process of 5G New Radio includes beam scanning, beam measurement, beam determination, and beam reporting. Beam scanning refers to covering a certain spatial area with a set of beams transmitted and received at a specified interval and direction. After the UE completes the processes of beam measurement, beam determination, and beam reporting, the base station (such as gNB) can set the uplink beam and downlink beam of the UE via a synchronization signal block (SSB) based on the reporting result from the UE.

[0003] However, when the UE is in initial access, the base station performs beam scanning from the first SSB to the last SSB to select the optimal beam for synchronizing the UE, but this process wastes the time and power of the TRxP and the UE.

Summary of the Invention

Problems to be Solved by the Invention

[0004] To solve the above problems, the present invention provides a method including storing an optimal SSB pattern in the UE, defining a reference signal received power (RSRP) for initial attachment, and changing the beam pattern sequence of the base station.

Means for Solving the Problems

[0005] One embodiment of the present invention provides a beam search method suitable for use by a user equipment (UE). The UE stores the cell identifier (ID) and synchronization signal block (SSB) from a previous network connection with a previously connected base station. The method comprises the following steps: First, a reconnection with the first base station is performed. Next, the cell ID and SSB from the previous network connection with the previously connected base station are read. The cell ID and SSB information is transmitted to the first base station via a physical random access channel (PRACH). Initial access to the first base station is performed by the UE using the cell ID and SSB in response to the cell ID in the PRACH received by the first base station matching a preset cell ID set by the previously connected base station.

[0006] One embodiment of the present invention further provides a beam search method. The method comprises the following steps: Multiple synchronization signal blocks (SSBs) transmitted by a base station are detected. Each SSB corresponds to a different beam direction, and their beam widths may all be the same or different. The received signal strength of each SSB is measured. At least one of the SSBs is selected according to the received signal strength, beam width, or both. A physical random access channel (PRACH) is used to transmit information about the SSBs to the base station. Initial access to the base station is performed via the SSBs.

[0007] One embodiment of the present invention further provides a non-temporary computer-readable medium for storing one or more instructions executed by one or more processors of a UE networked to a base station. One or more instructions have the following operations: First, the UE is reconnected to a first base station. The cell ID and SSB from the previous network connection with the previously connected base station are read. Next, the cell ID and SSB information is transmitted to the first base station via a physical random access channel (PRACH). Initial access to the first base station is performed by the UE using the cell ID and SSB in response to the cell ID in the PRACH received by the first base station matching a preset cell ID set by the previously connected base station. [Effects of the Invention]

[0008] This invention effectively saves time for the UE and base station to perform initial access, while also effectively reducing the power consumption of the UE. [Brief explanation of the drawing]

[0009] This disclosure can be better understood by reading the following detailed description with reference to the attached figures. The figures illustrate exemplary embodiments of this disclosure and, together with the description, help to illustrate the principles of this disclosure.

[0010] [Figure 1] This is a flowchart of a beam search method according to several embodiments of the present invention. [Figure 2] This is a flowchart of a beam search method according to several embodiments of the present invention. [Figure 3] This is a flowchart of a beam search method according to several embodiments of the present invention. [Figure 4] This figure shows a communication system 400 that performs the beam search method of Figure 2 according to some embodiments of the present invention. [Figure 5A] This figure shows a communication system 500 that performs the beam search method of Figure 3 according to some embodiments of the present invention. [Figure 5B] This figure shows a communication system 500 that performs the beam search method of Figure 3 according to some embodiments of the present invention. [Modes for carrying out the invention]

[0011] Figure 1 is a flowchart of a beam search method according to several embodiments of the present invention. The beam search method of the present invention is suitable for UEs. In some embodiments, the UE may be, for example, a laptop computer, a tablet, or a smartphone, but the present invention is not limited to these. In some embodiments of Figure 1, the UE stores the cell ID and synchronization signal block (SSB) from a previous network connection with a previously connected base station. In some embodiments, the previously connected base station may be, for example, a 5G base station such as a gNB, but the present invention is not limited to these. The beam search method has the following steps: First, reconnection with the first base station is performed (step S100). The cell ID and SSB from the previous network connection with the previously connected base station are read (step S102). The cell ID and SSB information are transmitted to the first base station via a physical random access channel (PRACH) (step S104). The first base station determines whether the cell ID in PRACH matches a preset cell ID set by the previously connected base station (step S106). Initial access to the first base station is performed by the UE using the cell ID and SSB in response to the cell ID matching a preset cell ID (step S108).

[0012] In steps S100 and S102, the cell ID and SSB from the previous network connection with the previously connected base station are stored in the UE's non-volatile memory. Therefore, even after the UE has completed its restart, the UE can read the cell ID and SSB used for the previous network connection with the previously connected base station. In some embodiments, if the UE does not perform a restart but simply turns its network function off and then on again, or moves from a location without network service to a location with network service, the cell ID and SSB from the UE's previous network connection with the previously connected base station can be stored in the UE's volatile memory, but the present invention is not limited to this.

[0013] In some embodiments, the SSB includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH), and a demodulated reference signal (DMRS). The DMRS associated with the PBCH is used to estimate the reference signal received power (RSRP). The RSRP is calculated in the beam measurement phase based on the SSB received by the UE, and in the beam determination phase, the optimal beam for the UE is selected.

[0014] In steps S104 and S106, in step S104, after the first base station receives the cell ID in PRACH and SSB information transmitted by the UE, the first base station determines whether the cell ID in PRACH matches a preset cell ID set by a previously connected base station. Since the UE transmits the cell ID and SSB information to all neighboring base stations via PRACH, only the first base station identifies that the cell ID from the UE matches a preset cell ID set by a previously connected base station (i.e., step S106: YES), and the first base station sets the UE so that the UE can perform step S108. In some embodiments of Figure 1, the beam search method of the present invention further includes the following steps: In response to the cell ID in PRACH not matching a preset cell ID (i.e., step S106: NO), the beam search method of the present invention performs step S2 in Figure 2 or step S3 in Figure 3 (step S110). Steps S100 to S108 in Figure 1 omit the beam scanning phase, allowing the UE's initial access to the base station to be completed quickly.

[0015] Figure 2 is a flowchart of a beam search method according to several embodiments of the present invention. The beam search method of the present invention has the following steps: In response to the cell ID in PRACH not matching a preset cell ID set by a previously connected base station, a plurality of updated SSBs transmitted by the second base station are detected, and the received signal strength of the updated SSBs is measured sequentially (step S200). It is determined whether the received signal strength of one of the multiple updated SSBs is higher than a threshold (step S202). If the received signal strength of one of the multiple updated SSBs is higher than the threshold (i.e., step S202: YES), the information of one of the multiple updated SSBs is transmitted to the second base station via PRACH (step S204). Initial access to the second base station is performed via one of the multiple updated SSBs (step S206). If the received signal strength of one of the multiple updated SSBs is not above a threshold (i.e., step S202: NO), the beam search method of the present invention repeats step S200. In step S200, the second base station transmits multiple updated SSBs at each time interval (e.g., 20 milliseconds). Each updated SSB corresponds to a different beam direction, and the SSBs have the same or different beam widths. The received signal strength may be, for example, RSRP, but is not limited to this of the present invention.

[0016] In step S202, the threshold may be, for example, -90 dBm, but the present invention is not limited to this. In some embodiments, the threshold may be equal to the minimum receiving sensitivity of the UE plus a defined threshold. Minimum receiving sensitivity means the minimum signal strength that the product antenna can receive from the network. Below this strength, the product does not receive a signal. The defined threshold is defined based on the RF performance of the product. In step S202, the UE selects the first updated SSB that exceeds the threshold. This approach avoids measuring all updated SSBs. Information on one of the multiple updated SSBs is transmitted to the second base station as long as one of the multiple updated SSBs exceeds the threshold during the sequential measurement period of the updated SSBs. After the beam search method (or UE) completes step S204, the second base station sets the UE according to the one updated SSB reported by the UE, so that the UE can perform step S206 accordingly.

[0017] In some embodiments of step S202, the received signal strength of one of the multiple updated SSBs is measured sequentially, and in response to determining that the received signal strength of one of the multiple updated SSBs is higher than a threshold, the UE immediately determines that the received signal strength of one of the multiple updated SSBs is higher than a threshold without measuring the remaining updated SSBs.

[0018] In some embodiments, steps S200-S206 in Figure 2 can be independent of steps S100-S108 in Figure 1. In other words, it is not necessary to respond to the mismatch between the cell ID and the preset cell ID in PRACH in step S106 of Figure 1. The beam search method can directly perform steps S200-S206 in Figure 2. In some embodiments, step S200 may correspond to the beam scanning phase and the beam measurement phase. Step S202 may correspond to the beam determination phase. Step S204 may correspond to the beam reporting phase.

[0019] Figure 3 is a flowchart of a beam search method according to several embodiments of the present invention. The beam search method of the present invention has the following steps: In response to the cell ID in PRACH not matching a preset cell ID set by a previously connected base station, a plurality of wide-beam SSBs transmitted by the second base station are detected, and the received signal strength of each wide-beam SSB is measured (step S300). Two wide-beam SSBs with the highest received signal strength are selected from the plurality of wide-beam SSBs, and information on the two wide-beam SSBs with the highest received signal strengths is transmitted to the second base station via PRACH (step S302). A plurality of narrow-beam SSBs transmitted by the second base station are detected. The beam directions of the plurality of narrow-beam SSBs are located between the beam directions of two wide-beam SSBs among the plurality of wide-beam SSBs, and the received signal strength of each narrow-beam SSB among the plurality of narrow-beam SSBs is measured (step S304). One narrow-beam SSB with the best received signal strength among multiple narrow-beam SSBs is selected, and information about the one narrow-beam SSB with the best received signal strength among multiple narrow-beam SSBs is transmitted to the second base station (step S306). Initial access to the second base station is performed via one narrow-beam SSB (step S308). In steps S300 and S304, the second base station transmits multiple wide-beam SSBs and multiple narrow-beam SSBs at each time interval (for example, 20 milliseconds).

[0020] In step S302, the beam search method of the present invention selects two widebeam SSBs having the highest received signal strength among a plurality of widebeam SSBs. Two widebeam SSBs having the highest received signal strength among the plurality of widebeam SSBs are used to determine a rough direction of the beam based on the relative position between the UE and the second base station. After the rough direction is determined, in step S304, the beam search method of the present invention measures the received signal strength of a plurality of narrowbeam SSBs. The beam directions of the plurality of narrowbeam SSBs are located between the beam directions of two widebeam SSBs among the plurality of widebeam SSBs. In step S306, the beam search method of the present invention selects one narrowbeam SSB having the highest received signal strength among the plurality of narrowbeam SSBs to determine an accurate direction. After the completion of step S306, the second base station configures the UE according to one narrowbeam SSB reported by the UE, and the UE can execute step S308 accordingly.

[0021] In some embodiments, steps S300 to S308 in FIG. 3 can be independent of steps S100 to S108 in FIG. 1. In other words, there is no need to respond to the mismatch between the cell ID and the preset cell ID during PRACH in step S106 in FIG. 1. The beam search method can directly execute steps S300 to S308 in FIG. 3. In some embodiments, step S300 and step S304 may correspond to a beam scanning phase and a beam measurement phase. Steps S302 and S306 may correspond to a beam determination phase. Steps S302 and S306 may also correspond to a beam reporting phase.

[0022] FIG. 4 is a diagram showing a communication system 400 that executes the beam search method of FIG. 2 according to some embodiments of the present invention. Some embodiments of FIG. 4 are scenarios applied to 5G New Radio (NR). As shown in FIG. 4, the communication system 400 includes a UE 402, a UE 404, and a base station 406. In some embodiments, the UE 402 and the UE 404 may be, for example, a notebook computer, a tablet, and a smartphone, but the present invention is not limited thereto. The base station 406 may be, for example, a 5G base station such as a gNB. The base station 406 transmits a plurality of SSBs to the UE 402 and the UE 404 every 20 milliseconds. As shown in FIG. 4, the base station 406 transmits four sets of SSBs to the UE 402 and the UE 404 within 80 milliseconds. Taking the third set of SSBs from left to right as an example, the third set of SSBs has eight SSBs within 5 milliseconds, and each corresponds to SSB indexes 0 to 7 in order. Each SSB in the third set of SSBs corresponds to a different beam direction.

[0023] When the UE 402 and the UE 404 receive the SSBs having the SSB indexes 0 to 7, the UE 402 and the UE 404 measure the received signal strengths of the SSBs having the SSB indexes 0 to 7 in order. In some embodiments, the received signal strength may be RSRP. For example, when the UE 402 measures that the received signal strength of the SSB having the SSB index 1 is higher than the threshold 410, the UE 402 does not need to continue measuring the received signal strengths of the subsequent SSB indexes 2 to 7. The UE 402 selects the SSB having the SSB index 1 and transmits the information of the SSB having the SSB index 1 to the base station 406 via the PRACH. After the base station 406 receives the information of the SSB having the SSB index 1, the base station 406 configures the UE 402, whereby the UE 402 executes initial access to the base station 406 via the SSB having the SSB index 1.

[0024] Similarly, after completing the measurement of the received SSB signal strength for SSBs with SSB indices 0 to 5, if UE404 measures that the received signal strength for the SSB with SSB index 6 is higher than threshold 410, UE404 does not need to continue measuring the received signal strength for the subsequent SSB with SSB index 7. UE404 selects the SSB with SSB index 6 and transmits information about the SSB with SSB index 6 to base station 406 via PRACH. After receiving the information about the SSB with SSB index 6, base station 406 configures UE404, thereby enabling UE404 to perform initial access to base station 406 via the SSB with SSB index 6. In some embodiments, threshold 410 may be, for example, -90 dBm, but the present invention is not limited to this. In some embodiments, the received signal strength of each SSB among a plurality of SSBs is measured sequentially, and in response to determining that the received signal strength of the SSB having SSB index 6 is higher than a threshold, the UE404 immediately determines that the received signal strength of the SSB having SSB index 6 is higher than a threshold without measuring the remaining SSBs among the plurality of SSBs.

[0025] Figures 5A and 5B show a communication system 500 of the beam search method of Figure 3 according to several embodiments of the present invention. Some embodiments of Figures 5A and 5B are scenarios applied to 5G nu-radio (NR). As shown in Figure 5B, the communication system 500 has a UE 502 and a base station 504. In some embodiments, the UE 502 may be, for example, a laptop computer, a tablet, and a smartphone, but the present invention is not limited to these. The base station 504 may be, for example, a 5G base station such as a gNB. In Figure 5A, the base station 504 transmits multiple SSBs to the UE 502 every 20 milliseconds. As shown in Figure 5A, the base station 504 transmits four sets of SSBs to the UE 502 within 80 milliseconds. Taking the third set of SSBs from left to right as an example, the third set of SSBs contains three SSBs within 2 milliseconds and two SSBs within the following 1 millisecond, which correspond to SSB indices 1, 4, 7, 2, and 3, respectively. In other words, each SSB in the third set of SSBs corresponds to a different beam direction. In some embodiments of Figure 5A, SSBs with SSB indices 1, 4, and 7 are wide-beam SSBs. SSBs with SSB indices 2 and 3 are narrow-beam SSBs.

[0026] In detail, UE502 detects SSBs with SSB indices 1, 4, and 7 from base station 504 and measures the received signal strength of the SSBs with SSB indices 1, 4, and 7. Subsequently, UE502 determines that the SSBs with SSB indices 1 and 4 have the highest received signal strength. As a result, UE502 selects the SSBs with SSB indices 1 and 4 and transmits information about the SSBs with SSB indices 1 and 4 to base station 504 via PRACH. In some embodiments, the received signal strength may be RSRP, but the present invention is not limited to this. The SSBs with SSB indices 1 and 4 may correspond, for example, to wide-beam SSB1 and wide-beam SSB4 in Figure 5B, respectively. The SSB with SSB index 7 may correspond, for example, to wide-beam SSB7 in Figure 5B.

[0027] When base station 504 receives SSB information having SSB indices 1 and 4, base station 504 transmits SSBs having SSB indices 2 and 3 to UE 502. The SSB having SSB index 2 corresponds to narrow-beam SSB2 in Figure 5B. The SSB having SSB index 3 corresponds to narrow-beam SSB3 in Figure 5B. In some embodiments of Figure 5B, the beam directions of narrow-beam SSB2 and SSB3 are between the beam directions of wide-beam SSB1 and SSB4. Subsequently, in Figure 5A, UE 502 detects the SSBs having SSB indices 2 and 3 and measures the received signal intensity of the SSBs having SSB indices 2 and 3.

[0028] Subsequently, UE502 determines that the SSB with SSB index 3 has the highest received signal strength, and therefore, UE502 selects the SSB with SSB index 3 and transmits information about the SSB with SSB index 3 to base station 504. After base station 504 receives information about the SSB with SSB index 3, base station 504 configures UE502, so UE502 performs initial access to base station 504 via the SSB with SSB index 3. In some embodiments, the threshold may be, for example, -90 dBm, but the present invention is not limited to this. In some embodiments of Figures 5A and 5B, UE502 only needs to measure the received signal strength of wide-beam SSB1 (SSB index 1), wide-beam SSB4 (SSB index 4), wide-beam SSB7 (SSB index 7), narrow-beam SSB2 (SSB index 2), and narrow-beam SSB3 (SSB index 3). Other SSBs transmitted by base station 504 (e.g., SSB index 5 and SSB index 6) are ignored, effectively saving time for UE 502 and base station 504 to perform initial access, and also effectively reducing the power consumption of UE 502.

[0029] Combining several embodiments of Figures 4, 5A, and 5B, the beam search method of the present invention comprises the following steps: Multiple SSBs transmitted by a base station are detected. Each SSB corresponds to a different beam direction, and the beam widths of each SSB are the same or different. The received signal strength of each SSB is measured. At least one SSB is selected according to at least one of the received signal strength and beam width. PRACH is used to transmit the SSB information to the base station. Initial access to the base station is performed via the SSB.

[0030] The present invention further provides a non-temporary computer-readable medium. The non-temporary computer-readable medium stores one or more instructions to be executed by one or more processors of a UE networked with a base station. One or more instructions have the following actions: Reconnection of the UE to the first base station is performed. The cell ID and SSB of the previous network connection with the previously connected base station are read. The cell ID and SSB information are transmitted to the first base station via PRACH. In response to the cell ID in the PRACH received by the first base station matching a preset cell ID set by the previously connected base station, initial access to the first base station is performed using the cell ID and SSB.

[0031] In some embodiments, in response to the cell ID in PRACH not matching a preset cell ID set by a previously connected base station, one or more instructions perform the following actions: Multiple updated SSBs transmitted by the second base station are detected. The received signal strengths of the updated SSBs are measured sequentially. The received signal strength of one of the multiple updated SSBs is determined to be higher than a threshold. Information about one updated SSB is transmitted to the second base station via PRACH. Initial access to the second base station is performed via one updated SSB.

[0032] In some embodiments, the received signal strength of one of several updated SSBs is measured sequentially, and in response to determining that the received signal strength of one updated SSB is higher than a threshold, one or more instructions have the following action: Without measuring the remaining updated SSBs among the several updated SSBs, it is immediately determined that the received signal strength of one updated SSB is higher than a threshold.

[0033] In some embodiments, in response to the cell ID in PRACH not matching a preset cell ID set by a previously connected base station, one or more instructions perform the following actions: Multiple wide-beam SSBs transmitted by the second base station are detected. The received signal strength of each wide-beam SSB is measured. Two wide-beam SSBs with the highest received signal strengths are selected. PRACH is used to transmit information about the two wide-beam SSBs with the highest received signal strengths to the second base station. Multiple narrow-beam SSBs transmitted by the second base station are detected. The beam direction corresponding to each narrow-beam SSB lies between the beam directions corresponding to two wide-beam SSBs. The received signal strength of each narrow-beam SSB is measured. One of the narrow-beam SSBs with the highest received signal strength is selected. PRACH is used to transmit information about the narrow-beam SSB with the highest received signal strength to the second base station. Initial access to the second base station is performed via the narrow-beam SSBs.

[0034] In some embodiments, the received signal strength has an RSRP. The threshold includes the minimum receive sensitivity of the UE. [Industrial applicability]

[0035] This disclosure applies to a UE in a communication system and applies to the UE by a non-temporary computer-readable medium storing one or more instructions to be executed by one or more processors of the UE. [Explanation of symbols]

[0036] S100, S102, S104, S106, S108, S110, S200, S202, S204, S206, S300, S302, S304, S306, S308 Process 400, 500 communication systems 402, 404, 502 User Equipment (UE) 406, 504 base station 410 threshold SSB1, SSB4, SSB7 Wide Beam SSB2, SSB3 Narrow Beam

Claims

1. A beam search method for user equipment (UE), wherein the UE stores cell identifiers (IDs) and synchronization signal blocks (SSBs) from a previous network connection with a previously connected base station, and the method is: The process of reconnecting with the first base station after the event that caused the aforementioned loss of network connectivity, The process of reading the cell ID and the SSB in the previous network connection with the previously connected base station, The process involves transmitting the cell ID and the SSB information to the first base station via a physical random access channel (PRACH), and In response to the cell ID in the PRACH received by the first base station matching a preset cell ID set by the previously connected base station, the UE performs an initial access to the first base station via the cell ID and the SSB. A beam search method characterized by having the following features.

2. A beam search method for user equipment (UE), wherein the UE stores cell identifiers (IDs) and synchronization signal blocks (SSBs) from a previous network connection with a previously connected base station, and the method is: The process of reconnecting with the first base station after the event that caused the aforementioned loss of network connectivity, The process of reading the cell ID and the SSB in the previous network connection with the previously connected base station, The process involves transmitting the cell ID and the SSB information to the first base station via a physical random access channel (PRACH), In response to the cell ID in the PRACH received by the first base station matching a preset cell ID set by the previously connected base station, the UE performs an initial access to the first base station via the cell ID and the SSB. The steps include detecting a plurality of updated SSBs transmitted by the second base station in response to the cell ID in the PRAC not matching the preset cell ID set by the previously connected base station, The process involves sequentially measuring the received signal strength of the multiple updated SSB signals, The process of determining that the received signal strength of one of the multiple updated SSBs is higher than a threshold, The process involves transmitting information about one of the multiple updated SSBs to the second base station via the PRACH, and The process of performing the initial access to the second base station via one of the multiple updated SSBs, A beam search method characterized by having the following features.

3. A beam search method for user equipment (UE), wherein the UE stores cell identifiers (IDs) and synchronization signal blocks (SSBs) from a previous network connection with a previously connected base station, and the method is: The process of reconnecting with the first base station, The process of reading the cell ID and the SSB in the previous network connection with the previously connected base station, The process involves transmitting the cell ID and the SSB information to the first base station via a physical random access channel (PRACH), In response to the cell ID in the PRACH received by the first base station matching a preset cell ID set by the previously connected base station, the UE performs an initial access to the first base station via the cell ID and the SSB. The steps include detecting a plurality of wide-beam SSBs transmitted by a second base station in response to the cell ID in the PRAC not matching the preset cell ID set by the previously connected base station, A step of measuring the received signal intensity of each wide-beam SSB among the plurality of wide-beam SSBs, The process of selecting two wide-beam SSBs having the highest received signal strength from among the plurality of wide-beam SSBs, The process of transmitting information about the two wide-beam SSBs having the highest received signal strength among the plurality of wide-beam SSBs via the PRACH to the second base station, A step of detecting a plurality of narrow-beam SSBs transmitted by the second base station, wherein the beam directions of the plurality of narrow-beam SSBs are located between the beam directions of two of the plurality of wide-beam SSBs. A step of measuring the received signal intensity of each of the multiple narrow beam SSBs, A step of selecting one narrow beam SSB having the highest received signal intensity among the plurality of narrow beam SSBs, The steps include transmitting information about the one narrow-beam SSB having the highest received signal strength among the plurality of narrow-beam SSBs via the PRACH to the second base station, The process of performing the initial access to the second base station via one of the multiple narrow-beam SSBs, A beam search method characterized by having the following features.

4. A non-temporary computer-readable medium for storing one or more instructions to be executed by one or more processors of a base station and a network-connected user device (UE), wherein the one or more instructions are: The process of reconnecting the UE to the first base station after an event that caused the loss of the previous network connection with the previously connected base station, The process involves reading the cell identifier (ID) and synchronization signal block (SSB) from the previous network connection with the previously connected base station, The process involves transmitting the cell ID and the SSB information to the first base station via a physical random access channel (PRACH), In response to the cell ID in the PRACH received by the first base station matching a preset cell ID set by the previously connected base station, the UE performs an initial access to the first base station via the cell ID and the SSB. It has, In response to the fact that the cell ID in the PRAC does not match the preset cell ID set by the previously connected base station, one or more commands: A process for detecting multiple updated SSBs transmitted by the second base station, The process involves sequentially measuring the received signal strength of the multiple updated SSB signals, The process of determining that the received signal strength of one of the multiple updated SSBs is higher than a threshold, The process of transmitting information about one of the multiple updated SSBs to the second base station via the PRACH, The process of performing the initial access to the second base station via one of the multiple updated SSBs. A non-temporary computer-readable medium characterized by having [a certain feature].

5. A non-temporary computer-readable medium for storing one or more instructions to be executed by one or more processors of a base station and a network-connected user device (UE), wherein the one or more instructions are: The process of reconnecting the UE to the first base station, The process involves reading the cell ID and synchronization signal block (SSB) from a previous network connection with a previously connected base station, The process involves transmitting the cell ID and the SSB information to the first base station via a physical random access channel (PRACH), In response to the cell ID in the PRACH received by the first base station matching a preset cell ID set by the previously connected base station, the UE performs an initial access to the first base station via the cell ID and the SSB. It has, In response to the fact that the cell ID in the PRAC does not match the preset cell ID set by the previously connected base station, one or more commands: A process for detecting multiple wide-beam SSBs transmitted by the second base station, A step of measuring the received signal intensity of each wide-beam SSB among the plurality of wide-beam SSBs, The process of selecting two wide-beam SSBs having the highest received signal strength from among the plurality of wide-beam SSBs, The process of transmitting information about the two wide-beam SSBs having the highest received signal strength among the plurality of wide-beam SSBs via the PRACH to the second base station, A step of detecting a plurality of narrow-beam SSBs transmitted by the second base station, wherein the beam directions of the plurality of narrow-beam SSBs are located between the beam directions of two of the plurality of wide-beam SSBs. A step of measuring the received signal intensity of each of the multiple narrow beam SSBs, A step of selecting one narrow beam SSB having the highest received signal intensity among the plurality of narrow beam SSBs, The steps include transmitting information about the one narrow-beam SSB having the highest received signal strength among the plurality of narrow-beam SSBs via the PRACH to the second base station, The process of performing the initial access to the second base station via one of the multiple narrow-beam SSBs, A non-temporary computer-readable medium characterized by having [a certain feature].

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