Method for executing random access resource selection and user equipment

Abstract

The invention provides a method for performing random access resource selection and user equipment (UE). The method includes: detecting a synchronization signal block (SSB) transmitted by a non-terrestrial network (NTN) cell based on predefined communication resources associated with the SSB; determining an identifier associated with the detected SSB; maintaining auxiliary information, wherein the auxiliary information comprises at least one of the following: first information associated with the detected occurrence order of the SSBs; and second information associated with the available service time of the random access resource associated with the detected SSB; when a plurality of SSBs are detected, selecting one of the detected SSBs as a first SSB based on the auxiliary information; and performing a random access procedure by applying the random access resource associated with the first SSB.

Description

Technical Field

[0001] The present invention relates to a communication technology, and in particular to a method and user equipment for performing random access resource selection. Background Art

[0002] Non-Terrestrial Networks (NTN) refer to communication systems that use non-terrestrial platforms such as satellites, high-altitude platforms (HAPs) and unmanned aerial vehicles (UAVs) to provide network coverage.

[0003] Unlike traditional terrestrial networks that rely on ground infrastructure such as base stations, NTNs can provide communications services to remote, rural or underserved areas where deploying traditional networks may be impractical or cost-prohibitive.

[0004] Reference Figure 1 , which illustrates a schematic diagram of a deployed multi-beam NTN cell. Figure 1 As shown, in a multi-beam NTN cell 100 (which exemplarily provides beams 0 to 6), a synchronization signal PBCH block (SSB) can be transmitted between adjacent beams of the NTN cell using time division multiplexing (TDM) to prevent inter-beam interference. Each beam of the NTN cell is associated with a specific SSB index to ensure that the signal is correctly identified and managed in the network.

[0005] For example, SSB 0 of cell 1 (e.g., multi-beam NTN cell 100) may be transmitted on frequency f1 using symbols 2 to 5 in time slot 0, SSB 1 of cell 1 may be transmitted on frequency f1 using symbols 8 to 11 in time slot 0, and SSB 2 of cell 1 may be transmitted on frequency f1 using symbols 2 to 5 in time slot 1, where the associated subcarrier spacing (SCS) may be 15 kHz and the maximum number of SSB indexes in the cell may be L (e.g., 4).

[0006] In some cases, a single geographical area may be served by multiple beams of an NTN cell. When UEs in RRC_IDLE or RRC_INACTIVE state detect multiple beams within these areas, they select a SSB based on predefined criteria and then proceed with a random access procedure.

[0007] by Figure 1For example, for UEs located in area 111 (covered by beam 0 and beam 1), these UEs can detect beam 0 and beam 1 provided by cell 1. Similarly, for UEs located in area 112 (covered by beam 1 and beam 2), these UEs can detect beam 1 and beam 2 provided by cell 1.

[0008] For these UEs, one of the detected beams (and / or SSBs) may be selected for the subsequent random access procedure. However, if the UEs in the NTN cannot correctly perform the beam (and / or SSB) selection, significant delays may be derived, which may seriously affect the performance of the NTN cell. Summary of the invention

[0009] In view of this, an embodiment of the present invention proposes a method for performing random access resource selection and a user equipment, which can be used to solve the above technical problems.

[0010] The present invention provides a method for performing random access resource selection in a UE served by an NTN. The method includes: the UE detects an SSB transmitted by an NTN cell based on a predefined communication resource associated with the SSB; the UE determines an identifier (ID) associated with the detected SSB; the UE maintains auxiliary information, wherein the auxiliary information includes at least one of the following: first information related to the order in which the detected SSBs appear; and second information related to the available service time of the random access resource associated with the detected SSB; when multiple SSBs are detected, the UE selects one of the detected SSBs as the first SSB based on the auxiliary information; and the UE applies the random access resource associated with the first SSB to perform a random access procedure.

[0011] The present invention provides a UE, comprising a transceiver and a processor. The processor is coupled to the transceiver and configured to perform: controlling the transceiver to detect an SSB transmitted by an NTN cell based on a predefined communication resource associated with the SSB; determining an ID associated with the detected SSB; maintaining auxiliary information, wherein the auxiliary information includes at least one of the following: first information related to an appearance order of the detected SSBs, and second information related to an available service time of a random access resource associated with the detected SSB; when multiple SSBs are detected, selecting one of the detected SSBs as a first SSB based on the auxiliary information; and applying the random access resource associated with the first SSB to perform a random access procedure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram showing a deployed multi-beam NTN cell.

[0013] Figure 2A A schematic diagram of a quasi-earth fixed multi-beam NTN cell is shown.

[0014] Figure 2B The figure shows a schematic diagram of a seismic multi-beam NTN cell.

[0015] Figure 3A A schematic diagram illustrating resource selection in a terrestrial network (TN).

[0016] Figure 3B Schematic diagram illustrating resource selection in NTN.

[0017] Figure 4 FIG. 4 is a functional block diagram of a UE according to an embodiment of the present invention.

[0018] Figure 5 The figure shows a flow chart of a method for selecting a random access resource according to an embodiment of the present invention.

[0019] Figure 6 A schematic diagram according to a first embodiment of the present invention is shown.

[0020] FIG. 7A to FIG. 7C Several schematic diagrams are shown for determining whether SSB is detected according to an embodiment of the present invention.

[0021] Figure 8 A schematic diagram according to an embodiment of the present invention is shown.

[0022] Fig. 9 A schematic diagram illustrating providing a distance indicator as second information according to a second embodiment of the present invention is shown.

[0023] Fig.10 The figure illustrates a flow chart of a UE organizing a detection order list according to an embodiment of the present invention.

[0024] Fig.11 FIG. 1 is a schematic diagram illustrating removing SSB from a detection order list according to an embodiment of the present invention.

[0025] Fig.12 FIG. 1 is a schematic diagram illustrating removing SSB from a detection order list according to an embodiment of the present invention.

[0026] Description of Reference Numerals DETAILED DESCRIPTION

[0027] Reference Figure 2A , which shows a schematic diagram of a quasi-earth-fixed multi-beam NTN cell. Figure 2AIn the figure, the satellite 20a can move in the direction shown, so that the satellite 20a is at different positions at different time points T1 to T3. In this case, the satellite 20a can provide a quasi-geostationary beam (e.g., beam 0 to beam 2) to cover a specific geographical area for a limited time, and then switch to another different geographical area in another cycle. This is common in non-geostationary orbit (NGSO) satellites that generate steerable beams.

[0028] exist Figure 2A In this case, UEs located in or moving into a geographic area served by multiple beams of a cell will observe multiple SSB IDs. In addition, as these UEs move through the coverage of different beams within the cell, they will observe changes in the SSB ID.

[0029] For example, for UE 21 located in geographic area 1 (corresponding to NTN tracking area (TA) 1), UE 21 may first detect the SSB ID of beam 0 corresponding to cell 1. Figure 2A As the satellite moves in the direction shown, UE 21 may determine that the detected SSB ID has changed from corresponding to beam 0 to beam 1 corresponding to cell 1.

[0030] In addition, when UE 21 is connected to Figure 2A As the satellite movement direction shown moves further into geographic area 2 (corresponding to NTN tracking area 2 ), UE 21 may determine that the detected SSB ID has changed from corresponding to beam 1 to beam 2 corresponding to cell 1 .

[0031] Reference Figure 2B , which shows a schematic diagram of an Earth-moving multi-beam NTN cell. Figure 2B In FIG. 1 , satellite 20b can move in the direction shown, so that satellite 20b is at different positions at different time points T1 to T3. Satellite 20b can provide a geostationary beam whose coverage slides on the surface of the earth, which can be understood as the case of an NGSO satellite that produces a fixed or non-steerable beam.

[0032] exist Figure 2B In the case of multiple SSB IDs, a UE located in or moving into a geographic area served by multiple beams of a cell will observe multiple SSB IDs. When the serving beam changes with satellite movement or when the UE moves in the coverage area of ​​different beams within the cell, the UE will observe changes in the SSB ID.

[0033] For example, for UE 21 located in geographic area 1 (corresponding to NTN tracking area 1), UE 21 can detect the SSB ID corresponding to beam 0 of cell 1 at time point T1. At time point T2, since satellite 20b has moved to another location, the beam serving UE 21 may become beam 1 of cell 1, so that UE 21 can determine that the detected SSB ID has changed from corresponding to beam 0 to beam 1 corresponding to cell 1. At time point T3, since satellite 20b has moved further, the beam serving UE 21 may become beam 2 of cell 1, so that UE 21 can determine that the detected SSB ID has changed from corresponding to beam 1 to beam 2 corresponding to cell 1.

[0034] For a UE in the RRC_IDLE or RRC_INACTIVE state, when the UE detects multiple SSB IDs at the same time, the UE may select one of the beams corresponding to these SSB IDs as the beam for performing the random access procedure. However, since the beams corresponding to the detected SSB IDs may have different service times for the UE, if the UE selects a beam with a shorter available service time to perform the random access procedure, the available service time of the beam may not be sufficient to complete the random access procedure, so the UE may need to select other beams in a short time to perform the random access procedure, which may introduce additional delays.

[0035] Reference Figure 3A , which illustrates a schematic diagram of resource selection in a terrestrial network (TN). Figure 3A In the example, it can be assumed that UE 31 is located within the coverage of beam 1 and beam 2 at time point T1, so that UE 31 can detect SSB 1 and SSB 2 corresponding to beam 1 and beam 2, respectively, at time point T1. In addition, it can be further assumed that UE 31 is located within the coverage of beam 1 and beam 2 at time point T1. Figure 3A The satellite moves in the direction shown.

[0036] from Figure 3A It can be seen that, based on the moving direction of UE 31, beam 2 has a longer available service time relative to UE 31 than beam 1. However, since UE 31 can detect SSB 1 and SSB 2, UE 31 can select SSB 1 at time point T2 and perform random access accordingly.

[0037] Specifically, at time point T3, UE 31 may transmit a preamble through a random access occasion (RO) associated with the selected SSB 1.

[0038] exist Figure 3AIn the example, UE 31 can transmit the preamble code through beam 1 corresponding to SSB 1, so gNB 30a providing beam 0 to beam 2 can receive the preamble code from UE 31 through beam 1.

[0039] Afterwards, gNB 30a may transmit a random access response (RAR) to UE 31 using beam 1. At the same time, UE 31 may determine whether it has received the RAR from gNB 30a via beam 1 within a predetermined time window (called "ra-ResponseWindow") after time point T3.

[0040] However, it is assumed that UE 31 has left the coverage of beam 1 at time point T4, which makes UE 31 unable to receive the RAR from gNB 30a through beam 1 within a predetermined time window (e.g., 0.5 to 9 milliseconds). In this case, at time point T5, UE 31 can select SSB 2 and transmit another preamble through a random access opportunity associated with the selected SSB 2. For example, UE 31 can transmit a preamble through beam 2 corresponding to SSB 2, so gNB 30a can receive the preamble from UE 31 through beam 2.

[0041] Afterwards, gNB 30a may transmit a RAR to UE 31 using beam 2. If the available service time of beam 2 is sufficient to perform the random access procedure, UE 31 will be able to receive this RAR and perform subsequent steps of the random access procedure accordingly to successfully complete the random access procedure.

[0042] exist Figure 3A In the example, since this is a terrestrial network scenario, the delay introduced by improper selection of SSB may be negligible. However, in a non-terrestrial network scenario, the delay introduced by improper selection of SSB may have an impact.

[0043] See also Figure 3B , which illustrates a schematic diagram of resource selection in NTN. Figure 3B In the example, it can be assumed that UE 31 is located within the coverage of beam 1 and beam 2 at time point T1, so that UE 31 can detect SSB 1 and SSB 2 corresponding to beam 1 and beam 2 respectively at time point T1. Figure 3A Different, it can be assumed that UE 31 is non-mobile or semi-static, but it is assumed that satellite 30b is along Figure 3B The satellite moves in the direction shown.

[0044] from Figure 3BIt can be seen that, based on the moving direction of satellite 30b, beam 2 has a longer available service time than beam 1 relative to UE 31. However, since UE 31 can detect SSB 1 and SSB 2, UE 31 can select SSB 1 at time point T2 and perform random access using the random access resources associated with SSB 1 accordingly.

[0045] Specifically, at time point T3, UE 31 may transmit a preamble through a random access opportunity associated with the selected SSB 1.

[0046] exist Figure 3B In the example, UE 31 can transmit the preamble via beam 1 corresponding to SSB 1, so gNB 30a providing beams 0 to 2 can receive the preamble from UE 31 via beam 1. However, since the preamble needs to be forwarded to gNB 30a by satellite 30b, the transmission path and propagation delay of the preamble will be longer than that of gNB 30a. Figure 3A The situation in is longer.

[0047] Afterwards, gNB 30a may transmit RAR to UE 31 using beam 1. At the same time, UE 31 may determine whether RAR is received from gNB 30a via beam 1 within a predetermined time window after time point T3. However, considering that the transmission path and propagation delay between UE 31 and gNB 30a are significantly greater than Figure 3A The situation in is longer, Figure 3B The predetermined time window used in may be designed to be Figure 3A The scheduled time window used in is longer.

[0048] Based on parameters such as the speed of satellite 30b, the size of NTN cell coverage, etc., the NTN round trip time (RTT) between UE 31 and gNB 30a can range from a few milliseconds to hundreds of milliseconds. Figure 3B The predetermined time window used in can be designed as the sum of NTN RTT and "ra-ResponseWindow".

[0049] At time point T4, UE 31 may have left the coverage of beam 1, which makes UE 31 unable to Figure 3B In this case, at time point T5, UE 31 may be located within the coverage of beam 2, and may select SSB 2 and transmit another preamble through a random access opportunity associated with the selected SSB 2. For example, UE 31 may transmit a preamble through beam 2 corresponding to SSB 2, and thus gNB 30a may receive the preamble from UE 31 through beam 2.

[0050] Afterwards, gNB 30a may transmit the RAR to UE 31 using beam 2. If the available service time of beam 2 is sufficient to perform the random access procedure, UE 31 will be able to receive the RAR and perform subsequent steps of the random access procedure accordingly to successfully complete the random access procedure.

[0051] from Figure 3B It can be seen that if UE 31 selects an SSB associated with a beam that does not have sufficient available service time to perform the random access procedure, the introduced delay will be greater than Figure 3A The situation is much more serious.

[0052] More specifically, due to the long propagation delay between UE and gNB, in non-terrestrial network scenarios, the time required for UE to discover RAR reception failure is not negligible. It is necessary to prevent RAR reception failure caused by insufficient beam available service time.

[0053] Therefore, embodiments of the present invention provide solutions to the above problems, which will be discussed below.

[0054] See also Figure 4 , which illustrates a functional block diagram of a UE according to an embodiment of the present invention.

[0055] exist Figure 4 In the embodiment, UE 400 includes a transceiver 402 and a processor 404. The transceiver 402 can be configured to transmit and receive signals from other devices within its coverage. The transceiver 402 can perform analog to digital signal conversion (ADC), digital to analog signal conversion (DAC), modulation, demodulation, signal amplification, low-pass filtering, and band-pass filtering. For example, the transceiver 402 is configured to provide information about the received signal to the processor 404, modulate the data received from the processor 404 into a modulated signal, and transmit the modulated signal to other devices.

[0056] In some embodiments, the UE 400 may further include other components, such as an antenna module for implementing the above functions of the transceiver 402 and the processor 404 .

[0057] The processor 404 may be coupled to the transceiver 402 and may be, for example, a general purpose processor, a special purpose processor, a conventional processor, a digital signal processor (DSP), a plurality of microprocessors, one or more microprocessors associated with a DSP core, a controller, a microcontroller, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), any other type of integrated circuit (IC), a state machine, etc.

[0058] In the embodiment of the present invention, the transmission / reception of the UE may be performed by the processor of the UE controlling the transceiver of the UE.

[0059] See also Figure 5 , which illustrates a flow chart of a method for performing random access resource selection according to an embodiment of the present invention. The method of this embodiment may be performed by Figure 4 UE 400 executes, Figure 5 The details of each step will be combined Figure 4 The components shown are described.

[0060] In step S510, UE 400 detects an SSB transmitted by an NTN cell based on predefined communication resources associated with the SSB.

[0061] In the embodiment of the present invention, the NTN cell may be a serving cell of the UE 400, and the NTN cell may provide a plurality of beams, wherein each of the plurality of beams may correspond to a predetermined SSB.

[0062] For example, UE 400 may be Figure 2A and / or Figure 2B UE 21 in the NTN cell can be Figure 2A and / or Figure 2B In this case, beam 0 to beam 2 of cell 1 may be regarded as corresponding predetermined beams, but the present invention is not limited thereto.

[0063] In an embodiment of the present invention, a predetermined SSB may be transmitted on a corresponding predefined communication resource, and the UE 400 may detect one or more predetermined SSBs based on the corresponding predefined communication resources.

[0064] by Figure 1 For example, the predetermined SSB may include SSB 0 to SSB 2, wherein the predefined communication resources corresponding to SSB 0 may include frequency f1 and symbols 2 to 5 in time slot 0, the predefined communication resources corresponding to SSB 1 may include frequency f1 and symbols 8 to 11 in time slot 0, and the predefined communication resources corresponding to SSB 2 may include frequency f1 and symbols 2 to 5 in time slot 1, but the present invention is not limited to this.

[0065] In step S520, UE 400 determines an identifier associated with the detected SSB.

[0066] In one embodiment, the detected SSB may be one of the predetermined SSBs. For example, if the location of UE 400 is only in a specific beam of the predetermined beam (e.g. Figure 1 In the case where the UE 400 is within the coverage of beam 0 in step S520, the SSB detected by the UE 400 will be the SSB corresponding to the specific beam (e.g., SSB 0). In this case, the UE 400 may determine the identifier of SSB 0 as the identifier to be considered in step S520.

[0067] In some embodiments, if multiple predetermined SSBs are detected, UE 400 may determine that multiple SSBs are detected. For example, if the location of UE 400 is within the coverage of multiple specific beams of the predetermined beams, the SSBs detected by UE 400 will be the SSBs corresponding to these multiple specific beams.

[0068] In the first example, if UE 400 is located at Figure 1 In the area 111 covered by beam 0 and beam 1 in common, beam 0 and beam 1 can be regarded as specific beams to be considered. In this case, UE 400 will be able to detect SSB0 and SSB 1 after time slot 0 passes, so SSB 0 and SSB 1 will be regarded as multiple detected SSBs. In this case, because SSB 0 is detected, UE 400 can determine the identifier of SSB 0 as the identifier to be considered in step S520, and can also determine the identifier of SSB 1 as the identifier to be considered in step S520 due to the detection of SSB 1.

[0069] In addition, UE 400 located in area 111 will not be able to detect SSB 2 in time slot 1 because UE 400 is not within the coverage of beam 2, but the present invention is not limited thereto.

[0070] In some embodiments, the detected SSB may also be understood / considered as an available SSB, but the present invention is not limited thereto.

[0071] In step S530, UE 400 maintains assistance information.

[0072] In various embodiments, the auxiliary information includes at least one of first information and second information. In the first embodiment, the first information is associated with the order of occurrence of the detected SSBs. In the second embodiment, the second information is associated with the available service time of the random access resource associated with the detected SSBs. The details of the first information and the second information will be further discussed in other embodiments below.

[0073] In step S540, when a plurality of SSBs are detected, the UE 400 selects one of the detected SSBs as a first SSB based on the auxiliary information.

[0074] In step S550, UE 400 applies the random access resources associated with the first SSB to perform a random access procedure.

[0075] In the above first example, since UE 400 has detected multiple SSBs (e.g., SSB 0 and SSB 1), UE 400 may select one of the detected SSB 0 and SSB 1 as the first SSB based on the auxiliary information. Next, UE 400 may determine the beam corresponding to the first SSB and the random access resource associated with the first SSB (wherein this random access resource may be referred to as the first random access resource), and apply the random access resource associated with the first SSB to perform a random access procedure.

[0076] For example, if UE 400 located in area 111 selects SSB 0 as the first SSB based on the auxiliary information, UE 400 can determine the corresponding random access resource associated with beam 0 as the first random access resource and apply the random access resource associated with beam 0 to perform a random access procedure.

[0077] For another example, if UE 400 located in area 111 selects SSB 1 as the first SSB based on auxiliary information, UE 400 may determine the corresponding random access resource associated with beam 1 as the first random access resource, and apply the random access resource associated with beam 1 to perform a random access procedure, but the present invention is not limited to this.

[0078] See also Figure 6 , which shows a schematic diagram according to a first embodiment of the present invention.

[0079] exist Figure 6 In the figure, the considered NTN cell 60 (referred to as "cell 1") is assumed to broadcast SSBs based on the broadcast mode 611. In the broadcast mode 611, SSBs numbered 0 to 6 (referred to as SSB 0 to SSB 6) will be transmitted sequentially on the frequency f1 in a time division multiplexing manner, and SSB 0 to SSB 6 may correspond to beams 0 to beams 6 provided by the NTN cell 60, respectively.

[0080] also, Figure 6 UE 61 in FIG. 6 is assumed to be located in an area where the coverage of beam 0, beam 1, and beam 6 overlap (i.e., the location of UE 61 is covered by beam 0, beam 1, and beam 6). In this case, UE 61 may determine SSB 0, SSB 1, and SSB 6 as detected SSBs in sequence based on broadcast mode 611, and UE 61 may determine the first information based on identifiers of these detected SSBs.

[0081] For better understanding, the identifiers of SSB 0, SSB 1, and SSB 6 may be represented as 0, 1, and 6, respectively, but the present invention is not limited thereto. In this case, the order of occurrence of the detected SSBs may be determined as {0, 1, 6}, but the present invention is not limited thereto.

[0082] exist Figure 6 In the figure, it is assumed that the satellite providing the NTN cell 60 can move at a specific speed in the direction DI1, and the network entity (e.g., gNB) can provide this information together with the broadcast mode of beam 0 to beam 6 to UE 61, so that UE 61 can deduce the order of occurrence of SSB 0 to SSB 6 based on this.

[0083] In other embodiments, the network may directly provide the order of occurrence of SSB 0 to SSB 6 after deriving the order of occurrence of SSB 0 to SSB 6 based on direction DI1, a specific speed of the satellite, and beam patterns of beam 0 to beam 6, but the present invention is not limited thereto.

[0084] In this embodiment, the order of appearance of SSB 0 to SSB 6 can be understood as the order in which beam 0 to beam 6 are used to serve the coverage of the NTN cell.

[0085] As the satellite moves, the order of appearance of the SSBs represents the view of the geographical area in which the SSB IDs of the NTN cells can be detected in time order in the geographical area. For example, the order of appearance of SSB 0 to SSB 6 can be assumed to be {6, 5, 1, 0, 4, 2, 3}, which means that beam 6, beam 5, beam 1, beam 0, beam 4, beam 2 and beam 3 will sequentially cover / serve the location of UE 61 as the satellite moves.

[0086] In this embodiment, the order of appearance of SSB 0 to SSB 6 can be regarded as one or more reference SSBID lists of the NTN cell 60, where each reference SSB ID can be associated with a corresponding SSB of a beam transmission of the NTN cell 60, and the order of each reference SSB ID in the list reflects the order of appearance of the corresponding SSB.

[0087] In this case, the elements in the order of appearance (e.g., {6, 5, 1, 0, 4, 2, 3}) can be understood as reference SSB IDs in the list, corresponding to SSB 6, SSB 5, SSB 1, SSB 0, SSB 4, SSB 2, and SSB 3, respectively. Based on the list, it can be observed that the order of appearance of SSB 6, SSB 5, SSB 1, SSB 0, SSB 4, SSB 2, and SSB 3 is 1 to 7, respectively.

[0088] In this embodiment, the above list may be included in the first information. Based on the first information (eg, the occurrence order and list of the detected SSBs), the UE 61 may perform step S540 to determine the first SSB.

[0089] In one embodiment, the first SSB may be a specific SSB having the latest appearance order among the plurality of detected SSBs.

[0090] For example, multiple detected SSBs can be interpreted as Figure 6 According to the list and / or the order of appearance (e.g., {6, 5, 1, 0, 4, 2, 3}), SSB 0 has the latest order of appearance among SSB 0, SSB 1, and SSB 6. In this case, UE 61 may select SSB 0 as the first SSB considered in step S540, and perform step S550 accordingly.

[0091] In this embodiment, a specific SSB having the latest appearance order among multiple detected SSBs means that the beam corresponding to the specific SSB can serve / cover UE 61 for the longest time. In other words, if UE 61 selects the specific SSB as the first SSB, it means that UE 61 selects the beam with the longest available service time among all beams covering / serving the position of UE 61, which can increase the possibility that UE 61 successfully performs the random access procedure.

[0092] In an embodiment of the present invention, if the SSB meets a predetermined condition, it can be regarded as being detected by the UE.

[0093] In one embodiment, in response to determining that the received signal strength of the SSB exceeds a predetermined threshold, the UE may determine that the SSB is a detected SSB. On the other hand, in response to determining that the received signal strength of the SSB does not exceed the predetermined threshold, the UE may determine that the SSB is not a detected SSB.

[0094] From another perspective, in response to determining that the received signal strength of a specific SSB exceeds a predetermined threshold, the UE may determine that the specific SSB has been detected (for example, the specific SSB may be determined to belong to multiple detected SSBs). On the other hand, in response to determining that the received signal strength of the specific SSB does not exceed the predetermined threshold, the UE may determine that the specific SSB has not been detected.

[0095] In addition, in response to determining that the received signal strength of the SSB exceeds a predetermined threshold, the UE may determine that a positive indication of the SSB is detected (e.g., the SSB is available). On the other hand, in response to determining that the received signal strength of the SSB does not exceed the predetermined threshold, the UE may determine that a negative indication of the SSB is detected (e.g., the SSB is unavailable).

[0096] In some embodiments, a positive indication of an SSB may be used to determine whether the SSB may be considered detected.

[0097] See also FIG. 7A to FIG. 7C , which illustrates several schematic diagrams for determining whether SSB is detected according to an embodiment of the present invention.

[0098] In one embodiment, the UE may determine that the SSB is a detected SSB in response to determining that a positive indication of the SSB has been identified a predetermined number of times in succession. From another perspective, the UE may determine that a particular SSB has been detected in response to determining that a positive indication of the SSB has been identified a predetermined number of times in succession.

[0099] exist Fig. 7A In the diagram, each arrow may be used to indicate a positive indication of a particular SSB, and each cross symbol (i.e., "x" symbol) may be used to indicate that a positive indication of the particular SSB was not detected as expected, but the present invention is not limited thereto. Therefore, when the UE determines that a positive indication of the particular SSB has been identified consecutively for a predetermined number of times, the UE may determine that the particular SSB has been detected.

[0100] In another embodiment, in response to determining that a positive indication of an SSB has been identified a predetermined number of times within a predefined observation window, the UE may determine that the SSB is a detected SSB. From another perspective, in response to determining that a positive indication of a particular SSB has been identified a predetermined number of times within a predefined observation window, the UE may determine that the particular SSB has been detected.

[0101] exist Figure 7B In case 1, when a positive indication 711 is detected, the UE may accordingly determine a predefined observation window 712, wherein the start time of the predefined observation window 712 may correspond to the time point of the positive indication 711, and the length of the predefined observation window 712 may be a predetermined time length, but the present invention is not limited thereto.

[0102] For example, the predetermined number may be assumed to be n. In this case, since three positive indications of a particular SSB have been identified within the predefined observation window 712, the UE may determine that the particular SSB has been detected.

[0103] Similarly, in Figure 7B In case 2, since three positive indications of a specific SSB have been identified within the predefined observation window 712, the UE may determine that the specific SSB has been detected, but the present invention is not limited thereto.

[0104] In one embodiment, the predefined observation window may be a sliding window, and the UE may perform the above determination based on positive indications covered by the sliding window at different times.

[0105] For example, in Figure 7C In case 1, the UE may determine that three positive indications of a particular SSB have been identified within the sliding window 721, and thus the UE may determine that the particular SSB has been detected.

[0106] exist Figure 7CIn case 2, the UE may determine that only two positive indications of a particular SSB are identified within the sliding window 722, and therefore the UE may determine that the particular SSB is not detected. On the other hand, if a positive indication of a particular SSB is not identified within the expected time, and then a positive indication of the particular SSB is identified at a subsequent expected time within the sliding window, the UE may adjust the start time of the sliding window to the sliding window 723 (for example, by adjusting the start time of the sliding window 722 to the time when the positive indication was previously identified), and the UE may determine that three positive indications of a particular SSB have been identified within the adjusted sliding window 723, and therefore the UE may determine that the particular SSB has been detected, but the present invention is not limited thereto.

[0107] In one embodiment, each entry in the SSB ID list may be further associated with an available service time of a corresponding random access resource.

[0108] In one embodiment, the NTN cell provides the UE with the average diameter of the NTN cell beam and the moving speed of the satellite serving the NTN cell (for example, the average diameter of the beam and the moving speed of the satellite are provided by system information), and the UE can estimate the service duration of random access resources (for example, random access resources provided by the beam associated with the SSB ID) based on information such as the average diameter of the beam and / or the moving speed of the satellite, but the present invention is not limited to this.

[0109] by Figure 6 For example, since the list is assumed to be {6, 5, 1, 0, 4, 2, 3}, the associated entities may be SSB 6, SSB 5, SSB1, SSB 0, SSB 4, SSB 2, and SSB 3. In this case, the UE may estimate the service duration of the random access resources corresponding to SSB 6, SSB 5, SSB 1, SSB0, SSB 4, SSB 2, and SSB 3. That is, the UE may estimate the service duration of beam 6, beam 5, beam 1, beam 0, beam 4, beam 2, and beam 3, but the present invention is not limited thereto.

[0110] In one embodiment, the UE may perform step S540 when initiating a random access procedure or when multiple detected SSBs are determined.

[0111] For example, in Figure 6 In the scenario, UE 61 may continuously append the SSB ID of the detected SSB to the SSB ID list, and accordingly perform the selection of the first SSB when the UE initiates the random access procedure. In addition or as an alternative, UE 61 may perform the selection of the first SSB when the list contains multiple SSB IDs, but the present invention is not limited thereto.

[0112] See also Figure 8 , which illustrates a schematic diagram according to an embodiment of the present invention. As described above, the second information may be associated with the available service time of the random access resource associated with the detected SSB ID.

[0113] exist Figure 8 In the example, it is assumed that one satellite provides beam 1 and beam 2 of the NTN cell. The moving speed (e.g., direction and speed) of the satellite is known to UE 81. In addition, it is assumed that the diameters of beam 1 and beam 2 are also known to UE 81, so UE 81 can deduce the average service duration of beam 1 and beam 2, respectively.

[0114] exist Figure 8 , UE 81 first detects SSB 1 at time point T0 (i.e., the time point when UE 81 enters the coverage of beam 1). UE 81 adds SSB 1 and time point T0 to the SSB ID list. Afterwards, UE 81 first detects SSB 2 at time point T1. UE 81 adds SSB 2 and time point T1 to the SSB ID list. Therefore, each entry in the SSB ID list includes the SSB ID information of the detected SSB and the first detection time.

[0115] In one embodiment, if the satellite moving speed is v, and the diameters of beam 1 and beam 2 are D1 and D2 respectively, UE 81 may determine that the service duration of beam 1 is D1 / v and the service duration of beam 2 is D2 / v.

[0116] In an example scenario, UE 81 starts a random access procedure at time point T2, when UE 81 is covered by beam 1 and beam 2. UE 81 determines that the available service time 821 of the random access resources of beam 1 may be (D1 / v–(T2-T0)), and the available service time 822 of the random access resources of beam 2 may be (D2 / v–(T2-T1)). If the available service time 822 of the random access resources of beam 2 is greater than the available service time 821 of the random access resources of beam 1, UE 81 determines that SSB2 is the first SSB, and performs the random access procedure using the random access resources associated with SSB 2.

[0117] In one embodiment, if the satellite moving speed is v and the average diameter of the NTN cell beam is D_average, UE 81 may determine that the service duration of beam 1 and beam 2 is (D_average / v), but the present invention is not limited thereto. In some embodiments, the value of (D_average / v) may be provided to UE 81 by the network through system information, but the present invention is not limited thereto.

[0118] exist Figure 8In the scenario, it is assumed that UE 81 first detects beam 1 at time point T0 (i.e., the time point when UE 81 enters the coverage of beam 1), and UE 81 first detects beam 2 at time point T1. UE 81 starts the random access procedure at time point T2, at which time UE 81 is covered by beam 1 and beam 2. UE 81 determines that the available service time 821 of the random access resources of beam 1 may be (D_average / v–(T2-T0)), and the available service time 822 of the random access resources of beam 2 may be (D_average / v–(T2-T1)). If the available service time 822 of the random access resources of beam 2 is greater than the available service time 821 of the random access resources of beam 1, UE 81 determines that SSB 2 is the first SSB, and performs the random access procedure using the random access resources associated with SSB 2.

[0119] In this embodiment, the first SSB may be an SSB corresponding to the longest available service time among the detected SSBs.

[0120] In one embodiment, the second information may include one or more reference SSB IDs of the NTN cell, and each reference SSB ID is associated with a distance value for indicating an available service time of a random access resource associated with the reference SSB ID.

[0121] In another embodiment, the second information may include one or more reference SSB IDs of the NTN cell, and each reference SSB ID is associated with a distance indicator, wherein each distance indicator indicates the distance between a first reference position associated with the corresponding reference SSB ID (e.g., the first reference position is within the coverage of the beam associated with the SSB ID) and a second reference position associated with the NTN cell (i.e., the second reference position is a position within the coverage of the NTN cell, and the position is not limited to the coverage of a specific beam of the NTN cell).

[0122] See also Fig. 9 , which is a schematic diagram illustrating providing a distance indicator as second information according to a second embodiment of the present invention.

[0123] exist Fig. 9 In the figure, the considered NTN cell 90 (referred to as "cell 1") may provide beams 0 to 6, which may correspond to SSB 0 to SSB 6, respectively.

[0124] In this embodiment, each beam may have a corresponding first reference position, cell 1 may have a second reference position 910, and the distance indicator associated with the SSB ID may be determined accordingly. For better understanding, it may be assumed that the position of the second reference position 910 is 0, but the present invention is not limited thereto.

[0125] For example, beam 0 may have a first reference position 920 that is 3 units away in the direction of satellite movement (which may be a position within the coverage area of ​​beam 0, such as the center). In this case, the distance indicator associated with SSB 0 (i.e., the SSB ID corresponding to beam 0) may be determined to be +3, where the positive sign indicates a positive value, i.e., the second reference position 910 is after the first reference position 920 along the direction of satellite movement.

[0126] For example, beam 1 may have a first reference position 921 that is 1 unit away in the direction of satellite movement (which may be a position within the coverage area of ​​beam 1, such as the center). In this case, the distance indicator associated with SSB 1 may be determined to be +1, where the positive sign indicates that the second reference position 910 is after the first reference position 921 in the direction of satellite movement.

[0127] As another example, beam 2 may have a first reference position 922 at a distance of 2 units in the opposite direction of the satellite movement direction (which may be a position within the coverage area of ​​beam 2, such as the center). In this case, the distance indicator associated with SSB 2 may be determined to be -2, where the negative sign indicates a negative value, i.e., the second reference position 910 is ahead of the first reference position 922 along the direction of satellite movement.

[0128] For beams 3 to 6, the relevant distance indicators may be determined based on the above teachings, which will not be further elaborated below.

[0129] In different embodiments, the distance indicator associated with the reference SSB ID may be determined by the UE and / or the network as an indication of the available service time, but the present invention is not limited thereto.

[0130] In a second embodiment, the UE may select a first SSB based on a distance indicator. In one embodiment, the first SSB may correspond to the smallest distance indicator among the detected SSBs. A distance indicator having a negative value is a value smaller than a distance indicator having a positive value or a zero value. A distance indicator having a zero value is smaller than a distance indicator having a positive value.

[0131] For example, in Fig. 9 In the scenario, if the UE is covered by beam 0 and beam 1, the UE may determine that SSB 0 and SSB 1 are detected SSBs. In this case, since SSB 1 corresponds to the smallest distance indicator (i.e., +1) among the detected SSBs (i.e., +3 associated with SSB 0 and +1 associated with SSB 1), the UE may determine that SSB 1 is the first SSB and perform the random access procedure accordingly.

[0132] To take another example, in Fig. 9In the scenario, if the UE is covered by beam 1 and beam 2, the UE may determine that SSB 1 and SSB 2 are detected SSBs. In this case, since SSB 2 corresponds to the smallest distance indicator (i.e., -2) among the detected SSBs, the UE may determine that SSB 2 is the first SSB and perform a random access procedure accordingly, but the present invention is not limited thereto.

[0133] In one embodiment, the assistance information may further include a detection order list of multiple SSB IDs, the identifiers belonging to (at least a portion of) the multiple SSBs, wherein the detection order list is organized by the UE according to the order in which each SSB is determined to be detected. The order of the entities in the detection order list can be used as an indication of the available service time.

[0134] See also Fig.10 , which illustrates a flowchart of a UE organizing a detection order list according to an embodiment of the present invention.

[0135] In step S1010 , the UE performs cell selection or cell reselection and camps on a cell.

[0136] In step S1020, the UE clears the detection order list after camping on the (re)selected cell.

[0137] In step S1030, the UE monitors the SSB. For example, the UE may monitor the SSB according to FIG. 7A to FIG. 7C The discussion of determining whether any SSB is detected is not repeated here.

[0138] In step S1040, the UE determines whether any new SSB associated with the current camping cell or serving cell is detected. If not, the UE executes step S1030. If yes, the UE executes step S1050 to append the newly detected SSB ID to the detection order list. Figure 6 For example, since UE 61 is assumed to detect SSB 0, SSB 1 and SSB 6 in sequence, UE 61 may be configured to perform: when it is determined that SSB 0 is detected, append the identifier of SSB 0 to the detection order list; when it is determined that SSB 1 is detected, append the identifier of SSB 1 to the detection order list; and when it is determined that SSB 6 is detected, append the identifier of SSB 6 to the detection order list, but the present invention is not limited to this.

[0139] In one embodiment, when the UE executes step S540, the UE may determine the first SSB according to the detection order list. In this embodiment, the first SSB may be the last SSB ID in the detection order list.

[0140] For example, if the detection order list is {0, 1, 6}, the UE may determine that SSB 6 is the first SSB, and accordingly perform a random access procedure using random access resources associated with SSB 6. For another example, if the detection order list is {0, 3, 4}, the UE may determine that SSB 4 is the first SSB, and accordingly perform a random access procedure using random access resources associated with SSB 4, but the present invention is not limited thereto.

[0141] In an embodiment of the present invention, the UE may determine whether to remove a specific SSB from the detection order list.

[0142] See also Fig.11 , which illustrates a schematic diagram of removing SSB from a detection order list according to an embodiment of the present invention.

[0143] In this embodiment, a specific SSB is an SSB detected by the UE, and the specific SSB is considered valid for the UE. When the UE determines that a positive indication of the specific SSB is detected, the UE may (re)start a timer associated with the specific SSB, which may be configured to a specific time length (configurable by radio resource control (RRC) signaling) and start counting down.

[0144] Next, the UE may determine whether another positive indication of the particular SSB is detected before the timer expires. If so, the UE may determine that the particular SSB is valid, such as Fig.11 As shown in case 1 of , and (re)start the timer accordingly. If no positive indication for this particular SSB is detected before the timer expires, the UE may determine that this particular SSB is invalid, such as Fig.11 As shown in Case 2, the specific SSB is removed from the detection order list accordingly.

[0145] See also Fig.12 , which illustrates a schematic diagram of removing SSB from a detection order list according to an embodiment of the present invention.

[0146] In one embodiment, in response to determining that a negative indication of a particular SSB has been identified a predetermined number of times within a predefined observation window, the UE may determine that the particular SSB has been invalidated.

[0147] exist Fig.12In the example, each solid arrow may be used to represent a positive indication of the specific SSB, and each dotted arrow may be used to represent a negative indication of the specific SSB (for example, when the positive indication of the specific SSB is not detected at the expected time, the UE regards it as detecting a negative indication of the specific SSB). Therefore, when the UE determines that the negative indication of the specific SSB has been identified for a predetermined number of times within the predefined time period, the UE may determine that the specific SSB has been invalidated.

[0148] exist Fig.12 In case 1, when a negative indication 1211 is detected, the UE may accordingly determine a predefined observation window 1212, wherein the start time of the predefined observation window 1212 may correspond to the time point of the negative indication 1211, and the length of the predefined observation window 1212 may be a predetermined time length, but the present invention is not limited thereto.

[0149] In this embodiment, the predetermined number may be assumed to be 3. In this case, since 3 consecutive negative indications of a specific SSB have been identified within the predefined observation window 1212, the UE may determine that the specific SSB is invalid and remove the specific SSB from the detection order list accordingly.

[0150] exist Fig.12 In situation 2, although the UE has not continuously identified three negative indications of a specific SSB, it has identified three negative indications of the specific SSB within the predefined observation window 1212, and the total number of negative indications is identified within the predefined observation window. The UE can determine that the specific SSB is invalid and remove the specific SSB from the detection order list accordingly, but the present invention is not limited to this.

[0151] exist Fig.12 If the number of negative indications for a particular SSB identified within the predefined observation window 1212 does not exceed a predetermined number of times, the UE may not remove the particular SSB from the detection order list.

[0152] In summary, the present invention provides a solution for UE served by NTN cell to better select random access resources to perform random access procedure. Therefore, the frequency of UE changing random access resources can be reduced, which can prevent time waste caused by selecting inappropriate SSB.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for performing random access resource selection by a user equipment (UE) in a non-terrestrial network (NTN) service, characterized in that: The method for performing random access resource selection by a user equipment (UE) under a non-terrestrial network (NTN) service includes: Detecting, by the UE, a synchronization signal block (SSB) transmitted by an NTN cell based on predefined communication resources associated with the SSB; determining, by the UE, an identifier (ID) associated with the detected SSB; The UE maintains assistance information, wherein the assistance information includes at least one of the following: first information associated with the detected order of occurrence of the SSBs; and second information associated with the detected available service time of the random access resource associated with the SSB; When a plurality of SSBs are detected, selecting, by the UE, one of the detected SSBs as a first SSB based on the auxiliary information; and The UE applies the random access resources associated with the first SSB to perform a random access procedure.

2. The method for performing random access resource selection by a user equipment (UE) under a non-terrestrial network (NTN) service according to claim 1, characterized in that: The first information associated with the detected order of occurrence of the SSBs comprises: A list of one or more reference SSB IDs of the NTN cell, each reference SSB ID being associated with a corresponding SSB transmitted by the NTN cell, wherein the order of each reference SSB ID in the list reflects the order of appearance of the corresponding SSB.

3. The method for performing random access resource selection by a user equipment (UE) under a non-terrestrial network (NTN) service according to claim 2, characterized in that: The list also includes one or more entities associated with the one or more reference SSBIDs, each of the entities being associated with an available service time of a corresponding random access resource.

4. The method for performing random access resource selection by a user equipment (UE) under a non-terrestrial network (NTN) service according to claim 1, wherein the second information comprises at least one of the following information: One or more reference SSB IDs of the NTN cell, each of the reference SSB IDs being associated with an available service time; One or more reference SSB IDs of the NTN cell, each of the reference SSB IDs being associated with a distance value; One or more reference SSB IDs of the NTN cell, and each of the reference SSB IDs is associated with a distance indicator, wherein each of the distance indicators indicates a distance between a first reference position associated with the corresponding reference SSB ID and a second reference position associated with the NTN cell.

5. The method for performing random access resource selection by a user equipment (UE) under a non-terrestrial network (NTN) service according to claim 1, characterized in that: Also includes: In response to determining that the received signal strength of the SSB exceeds a predefined threshold, determining that the SSB is a detected SSB; In response to determining that a positive indication of the SSB has been identified a predetermined number of times in succession, determining that the SSB is a detected SSB; or In response to determining that a positive indication of the SSB has been identified a predetermined number of times within a predefined observation window, the SSB is determined to be a detected SSB.

6. The method for performing random access resource selection by a user equipment (UE) under a non-terrestrial network (NTN) service according to claim 1, characterized in that: The selecting, by the UE based on the auxiliary information, one of the multiple detected SSBs as the first SSB includes: When starting a random access procedure, or when determining the multiple detected SSBs, the UE selects one from the multiple detected SSBs as the first SSB based on the auxiliary information.

7. The method for performing random access resource selection by a user equipment (UE) under a non-terrestrial network (NTN) service according to claim 1, characterized in that: The auxiliary information also includes: A detection order list of multiple SSB IDs of the multiple SSBs, wherein the detection order list is organized by the UE based on the order in which each of the SSBs is detected.

8. The method for performing random access resource selection by a user equipment (UE) under a non-terrestrial network (NTN) service according to claim 1, characterized in that: The selected SSB corresponds to a random access resource associated with an SSB having a longest available service time among the plurality of detected SSBs; or The selected SSB is a most recently detected SSB among the plurality of detected SSBs.

9. A user equipment (UE) for operating in a non-terrestrial network (NTN), characterized in that The user equipment (UE) includes: transceiver; and A processor, coupled to the transceiver, configured to execute: controlling the transceiver to detect a synchronization signal block (SSB) transmitted by an NTN cell based on a predefined communication resource associated with the SSB; determining an identifier (ID) associated with the detected SSB; Maintain auxiliary information, wherein the auxiliary information includes at least one of the following: first information associated with an order of occurrence of said detected SSBs; and second information associated with an available service time of a random access resource associated with the detected SSB; When a plurality of SSBs are detected, selecting one of the detected SSBs as a first SSB based on the auxiliary information; and Apply random access resources associated with the first SSB to perform a random access procedure.

10. The user equipment (UE) according to claim 9, characterized in that The first information associated with the order of occurrence of the detected SSBs includes: A list of one or more reference SSB IDs of the NTN cell, each reference SSB ID being associated with a corresponding SSB transmitted by the NTN cell, wherein the order of each reference SSB ID in the list reflects the order of appearance of the corresponding SSB.

11. The user equipment (UE) of claim 10, wherein the list further comprises one or more entities associated with the one or more reference SSB IDs, each of the entities being associated with an available service time of a corresponding random access resource.

12. The user equipment (UE) according to claim 9, characterized in that The second information includes at least one of the following information: one or more reference SSB IDs of the NTN cell, each of the one or more reference SSB IDs being associated with an available service time; one or more reference SSB IDs of the NTN cell, each of the one or more reference SSB IDs being associated with a distance value for indicating an available service time of a reference random access resource associated with the reference SSB ID; One or more reference SSB IDs of the NTN cell, and each of the one or more reference SSB IDs is associated with a distance indicator, wherein each of the distance indicators indicates a distance between a first reference position associated with the corresponding reference SSB ID and a second reference position associated with the NTN cell.

13. The user equipment (UE) according to claim 9, characterized in that Also included is the processor configured to execute: In response to determining that the received signal strength of the SSB exceeds a predefined threshold, determining that the SSB is a detected SSB; In response to determining that a positive indication of the SSB has been identified continuously for a predetermined number of times, determining that the SSB is a detected SSB; or In response to determining that a positive indication of the SSB has been identified a predetermined number of times within a predefined observation window, the SSB is determined to be a detected SSB.

14. The user equipment (UE) according to claim 9, characterized in that Also included is the processor configured to execute: When starting a random access procedure, or when determining the multiple detected SSBs, the UE selects one from the multiple detected SSBs as the first SSB based on the auxiliary information.

15. The user equipment (UE) according to claim 9, characterized in that The auxiliary information also includes: A detection order list of multiple SSB IDs of the multiple SSBs, wherein the detection order list is organized by the UE based on determining the order in which each of the multiple SSBs is detected.

16. The user equipment (UE) according to claim 9, characterized in that The selected SSB corresponds to a random access resource associated with the SSB, the random access resource having a longest available service time among the plurality of detected SSBs; or The selected SSB is a most recently detected SSB among the plurality of detected SSBs.

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