Method and equipment for reducing transmission delay of PRACH (Physical Random Access Channel)

Abstract

The invention relates to a method and equipment for physical random access channel (PRACH) transmission delay reduction. One embodiment of the present disclosure provides a user equipment (UE) comprising: a transceiver; and a processor coupled with the transceiver and configured to: receive a first configuration associated with a PRACH repetition; and determining a random access channel occasion (RO) for PRACH repetition based on a first total number of PRACH repetition configured by the first configuration.

Description

Technical Field

[0001] The present disclosure relates to wireless communication, and in particular, to methods and devices for reducing the transmission delay of a Physical Random Access Channel (PRACH). Background Art

[0002] In a Time Division Duplex (TDD) system, which can be in Frequency Range 1 (FR1) or Frequency Range 2 (FR2), the UL time slots in a downlink (DL) or uplink (UL) configuration mode can be restricted. For example, for a configuration mode such as DDDSU, where D represents "DL", S represents "Special", and "U" represents "UL". It can be seen that only one UL time slot is configured in this mode.

[0003] In this scenario, PRACH repeated transmissions can be performed in the UL time slots of multiple DL / UL configuration modes, which may result in a high PRACH transmission delay.

[0004] Therefore, it is desirable to provide a solution for reducing the PRACH transmission delay. Summary of the Invention

[0005] An embodiment of the present disclosure provides a User Equipment (UE), which includes: a transceiver; and a processor, coupled to the transceiver and configured to: receive a first configuration associated with Physical Random Access Channel (PRACH) repetition; and determine a Random Access Channel Opportunity (RO) for PRACH repetition based on a first total number of PRACH repetitions configured by the first configuration.

[0006] In some embodiments, the RO for PRACH repetition is included in at least one RO bundle, and the RO bundle includes a set of ROs associated with a Synchronization Signal and Physical Broadcast Channel PBCH block SSB, and the processor is further configured to: determine a first RO in the RO bundle as the starting RO for PRACH repetition.

[0007] In some embodiments, the first RO bundle associated with the SSB starts from the first RO associated with the SSB in the first frame.

[0008] In some embodiments, the RO for PRACH repetition is included in one RO bundle, and the RO bundle includes the first total number of ROs associated with the SSB, and the processor is further configured to receive a second configuration indicating one of the following: a set of indices of candidate starting ROs of the RO bundle; an offset associated with the first RO in the RO bundle; or the total number of candidate starting ROs in the RO bundle.

[0009] In some embodiments, the processor is further configured to: determine a starting RO for the PRACH repetition among the ROs, wherein the starting RO among the RO bundle is one of the following: the first RO in the RO bundle; a candidate starting RO identified by an index in the set of indexes; or a candidate starting RO having an offset associated with the first RO in the RO bundle.

[0010] In some embodiments, the processor is further configured to receive a third configuration that indicates one of the following: the periodicity of candidate starting ROs associated with the SSB; or the periodicity of candidate starting ROs associated with the SSB and an offset associated with the first RO.

[0011] In some embodiments, the processor is further configured to: determine a set of candidate starting ROs based on the periodicity or based on the periodicity and the offset, wherein the first candidate starting RO is the first RO associated with the SSB in the first frame.

[0012] In some embodiments, the processor is further configured to determine a period based on the first total number of PRACH repetitions and a second total number of ROs associated with the SSB from a set of SSBs in a period, and wherein the second total number of ROs is equal to or greater than the first total number of ROs.

[0013] In some embodiments, the second total number is an integer multiple of the first total number.

[0014] In some embodiments, the period is an SSB-to-RO association period or an SSB-to-RO association pattern period, wherein the SSB-to-RO association pattern period includes at least one SSB-to-RO association period.

[0015] In some embodiments, the period includes a plurality of RO bundles, each RO bundle including a set of ROs associated with the SSB, and the number of ROs in the set is equal to or less than the first total number.

[0016] In some embodiments, the candidate starting RO for the PRACH repetition is the first RO in the RO bundle.

[0017] In some embodiments, each RO associated with the SSB in the period is indexed, and the first RO associated with the SSB in the period is a candidate starting RO, and an RO having an index value divisible by the first total number is a candidate starting RO.

[0018] In some embodiments, the candidate starting RO of the RO for the PRACH repetition is associated with a preamble group.

[0019] In some embodiments, the total number of preambles in the preamble group is determined by the first total number and the density of candidate starting ROs in a period determined based on the PRACH repetition.

[0020] In some embodiments, the processor is further configured to: determine the ROs other than the starting RO for PRACH repetition as ROs associated with the same SSB and after the starting RO in the time domain, where the starting RO is associated with the same SSB.

[0021] Another embodiment of the present disclosure provides a base station (BS) including: a transceiver; and a processor coupled to the transceiver and configured to: transmit a first configuration associated with PRACH repetition; and determine ROs for receiving PRACH repetition based on a first total number of PRACH repetitions.

[0022] In some embodiments, the ROs for PRACH repetition are included in at least one RO bundle, and the bundle includes a set of ROs associated with an SSB, and the processor is further configured to: determine a first RO in the RO bundle as the starting RO for PRACH repetition.

[0023] In some embodiments, the first RO bundle associated with the SSB starts from the first RO associated with the SSB in the first frame.

[0024] In some embodiments, the ROs for PRACH repetition are included in one RO bundle, and the RO bundle includes the first total number of ROs associated with the SSB, and the second configuration indicates one of the following: a set of indices of candidate starting ROs of the RO bundle; an offset associated with the first RO in the RO bundle; or the total number of candidate starting ROs in the RO bundle.

[0025] In some embodiments, the processor is further configured to: determine the starting RO of the ROs for PRACH repetition, where the starting RO in the RO bundle is one of the following: the first RO in the RO bundle; a candidate starting RO identified by an index in the set of indices; or a candidate starting RO having the offset associated with the first RO in the RO bundle.

[0026] In some embodiments, the third configuration indicates one of the following: the periodicity of candidate starting ROs associated with the SSB; or the periodicity of candidate starting ROs associated with the SSB and the offset associated with the first RO.

[0027] In some embodiments, the processor is further configured to: determine a set of candidate starting ROs based on the periodicity or based on the periodicity and the offset, wherein a first candidate starting RO is a first RO in a first frame associated with the SSB.

[0028] In some embodiments, a period is determined based on the first total number of PRACH repetitions, and wherein a second total number of ROs associated with an SSB from a set of SSBs in the period is equal to or greater than the first total number.

[0029] In some embodiments, the second total number is an integer multiple of the first total number.

[0030] In some embodiments, the period is an SSB-to-RO association period or an SSB-to-RO association pattern period, wherein the SSB-to-RO association pattern period includes at least one SSB-to-RO association period.

[0031] In some embodiments, the period includes a plurality of RO bundles, each RO bundle includes a set of ROs associated with the SSB, and the number of ROs in the set is equal to or less than the first total number.

[0032] In some embodiments, a candidate starting RO for PRACH repetition is a first RO in an RO bundle.

[0033] In some embodiments, each RO associated with the SSB in the period is indexed, and a first RO associated with the SSB in the period is a candidate starting RO, and an RO having an index value divisible by the first total number is a candidate starting RO.

[0034] In some embodiments, a candidate starting RO of the ROs for PRACH repetition is associated with a preamble group.

[0035] In some embodiments, the total number of preambles in the preamble group is determined by the first total number and the density of candidate starting ROs in a period determined based on the first total number of PRACH repetitions.

[0036] In some embodiments, the processor is further configured to: determine the ROs for PRACH repetition other than the starting RO as ROs associated with the same SSB and after the starting RO in the time domain, wherein the starting RO is associated with the same SSB.

[0037] Another embodiment of the present disclosure provides a method performed by a UE, including: receiving a first configuration associated with PRACH repetition; and determining ROs for PRACH repetition based on a first total number of PRACH repetitions configured by the first configuration.

[0038] Another embodiment of the present disclosure provides a method performed by a base station (BS), including: transmitting a first configuration associated with PRACH repetition; and determining an RO for receiving PRACH repetition based on a first total number of PRACH repetitions. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] To describe the manner in which the advantages and features of the present application can be obtained, a description of the present application is presented by referring to its specific embodiments illustrated in the drawings. These figures only depict example embodiments of the present application and should not be considered as a limitation of its scope.

[0040] Figure 1 Schematic diagram illustrating a wireless communication system according to some embodiments of the present disclosure.

[0041] Figure 2 Illustration of a random access procedure according to some embodiments of the present disclosure.

[0042] Figure 3 Illustration of the structure of the overall resources for PRACH transmission according to some embodiments of the present disclosure.

[0043] Figures 4A to 4C Illustration of some types of associations between RO and SSB according to some embodiments of the present disclosure.

[0044] Figure 5 Illustration of the SSB-to-RO association period according to some embodiments of the present disclosure.

[0045] Figure 6 Illustration of PRACH repeated transmission in an RO bundle according to some embodiments of the present disclosure.

[0046] Figure 7 Illustration of PRACH repeated transmission in an RO bundle according to some embodiments of the present disclosure.

[0047] Figure 8 Illustration of PRACH repeated transmission in an RO bundle according to some embodiments of the present disclosure.

[0048] Figure 9 Illustration of PRACH repeated transmission according to some embodiments of the present disclosure.

[0049] Figure 10 Illustration of the proposed SSB-to-RO association period according to some embodiments of the present disclosure.

[0050] Figure 11 Illustration of the proposed SSB-to-RO association period according to some embodiments of the present disclosure.

[0051] Figure 12Describe a preamble partitioning method for PRACH repetition according to some embodiments of the present disclosure.

[0052] Figure 13 Describe a method performed by a UE for wireless communication according to some embodiments of the present disclosure.

[0053] Figure 14 Describe a method performed by a BS for wireless communication according to some embodiments of the present disclosure.

[0054] Figure 15 Describe a simplified block diagram of a device according to some embodiments of the present disclosure. Detailed Description

[0055] The detailed description of the drawings is intended as a description of the currently preferred embodiments of the present invention and is not intended to represent the only form in which the present invention may be practiced. It should be understood that the same or equivalent functions may be achieved by different embodiments that are intended to be covered within the spirit and scope of the present invention.

[0056] Although the operations are depicted in the drawings in a particular order, those skilled in the art will readily recognize that such operations need not be performed in the particular order shown or in a sequential order, or that all of the illustrated operations are required to achieve the desired result; one or more operations may sometimes be skipped. Additionally, the drawings may schematically depict one or more example processes in the form of a flowchart. However, other operations not depicted may be incorporated into the example processes schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. In some cases, multitasking and parallel processing may be advantageous.

[0057] Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided in a specific network architecture and new service scenario, such as a cellular telephone network, a time division multiple access (TDMA)-based network, a code division multiple access (CDMA)-based network, an orthogonal frequency division multiple access (OFDMA)-based network, an LTE network, a third generation partnership project (3GPP)-based network, LTE, advanced LTE (LTE-A), 3GPP 4G, 3GPP 5GNR, 3GPP Release 16 and later versions, a satellite communication network, a high altitude platform network, etc. It is contemplated that as the network architecture and new service scenarios evolve, all embodiments in the present disclosure are also applicable to similar technical problems; and furthermore, the terms cited in the present disclosure may change, which should not affect the principles of the present disclosure.

[0058] Figure 1 Describe a schematic diagram of a wireless communication system according to some embodiments of the present disclosure.

[0059] AsFigure 1 As shown in Figure 1 , the wireless communication system 100 may include at least one UE (e.g., UE 101-A and UE 101-B, collectively referred to as UE 101) and at least one BS (e.g., BS 102). Although a specific number of UEs 101 and BSs 102 are depicted in Figure 1 , it is contemplated that any number of UEs and BSs may be included in the wireless communication system 100. Figure 1 As depicted in Figure 1 , although a specific number of UEs 101 and BSs 102 are shown, it is contemplated that any number of UEs and BSs may be included in the wireless communication system 100.

[0060] UE 101 may include a computing device such as a desktop computer, laptop computer, personal digital assistant (PDA), tablet computer, smart TV (e.g., a TV connected to the Internet), set-top box, gaming console, security system (including security cameras), in-vehicle computer, network device (e.g., router, switch, and modem), or the like. According to some embodiments of the present disclosure, UE 101 may include a portable wireless communication device, smartphone, cellular phone, flip phone, device with a subscriber identity module, personal computer, pager, or any other device capable of transmitting and receiving communication signals over a wireless network. In some embodiments of the present disclosure, UE 101 includes a wearable device such as a smartwatch, fitness band, optical head-mounted display, or the like. Additionally, UE 101 may be referred to as a subscriber unit, mobile device, mobile station, user, terminal, mobile terminal, wireless terminal, fixed terminal, subscriber station, user terminal, or device, or other terms used in the art to describe the same.

[0061] BS 102 may be distributed throughout a geographic area. In certain embodiments of the present disclosure, BS 102 may also be referred to as an access point, access terminal, base, base unit, macrocell, Node-B, evolved Node B (eNB), gNode B (gNB), home Node-B, relay node, or device, or other terms used in the art to describe the same. BS 102 is generally part of a radio access network that may include one or more controllers communicatively coupled to one or more corresponding BSs 102. BS 102 may communicate with UE 101 via the Uu interface. For example, BS 102 may transmit a downlink (DL) communication signal to UE 101 and may receive an uplink (UL) communication signal from UE 101.

[0062] The wireless communication system 100 may be compatible with any type of network capable of transmitting and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with wireless communication networks, cellular phone networks, time division multiple access (TDMA)-based networks, code division multiple access (CDMA)-based networks, orthogonal frequency division multiple access (OFDMA)-based networks, LTE networks, 3GPP-based networks, 3GPP 5G networks, satellite communication networks, high altitude platform networks, and / or other communication networks.

[0063] In some embodiments of the present disclosure, the wireless communication system 100 is compatible with 5G NR of the 3GPP protocol. For example, BS102 may use an orthogonal frequency division multiplexing (OFDM) modulation scheme to transmit data on the DL, and UE 101 may use a discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) or cyclic prefix OFDM (CP-OFDM) scheme to transmit data on the UL. However, more generally, the wireless communication system 100 may implement some other open or proprietary communication protocols, such as WiMAX, and other protocols.

[0064] In some embodiments of the present disclosure, BS102 and UE 101 may communicate using other communication protocols (such as wireless communication protocols of the IEEE

[0065] 802.11 series). In addition, in some embodiments of the present disclosure, BS102 and UE101 may communicate via the authorized spectrum via the Uu interface, while in some other embodiments, BS102 and UE 101 may communicate via the unlicensed spectrum. The present disclosure is not intended to be limited to any specific wireless implementation

[0066] Figure 2 Describe a random access procedure according to some embodiments of the present disclosure.

[0067] The random access procedure can be used for various purposes. It can be used by the UE in initial access to find a cell to camp on; or by a UE in the RRC idle state or in the RRC inactive state to switch to the RRC connection to start data transmission or reception; or by a UE in the RRC connected state to re-establish the lost UL synchronization, etc.

[0068] In operation 201, the UE may transmit a message, i.e., Msg1, which may include a preamble. In operation 202, the UE may receive Msg2 containing a random access response (RAR), which indicates the reception of the preamble and provides scheduling information for the transmission of Msg3. In operation 203, the UE may transmit Msg3 according to the scheduling information, and in operation 204, the UE may receive Msg4 from the BS. Msg3 and Msg4 are used to resolve potential conflicts caused by simultaneously transmitting the same preamble from different UEs.

[0069] The Physical Random Access Channel (PRACH) preamble (i.e., Msg1) transmission can be performed within a PRACH occasion (RO). Each RO can occupy multiple consecutive resource blocks in the frequency domain. The BS can configure one or more frequency-division multiplexed (FDM) ROs for a time instance. In the time domain, ROs can be configured within each PRACH configuration period, which can contain one or more radio frames. Within a PRACH configuration period, a set of subframes can be indicated as containing a set of PRACH time slots, and within each PRACH time slot, there can be a set of ROs available for PRACH preamble transmission.

[0070] Figure 3 Describe the structure of the overall resources for PRACH transmission according to some embodiments of the present disclosure.

[0071] Figure 3 Depict a PRACH configuration period, which can contain 1 radio frame in the time domain. The frame can contain 10 subframes, subframe #0, subframe #1, …, subframe #9. Subframe #0 and subframe #6 within the PRACH configuration period can be indicated as containing PRACH time slots. The PRACH time slots in subframe #0 or subframe #6 can contain 2 ROs in the time domain and 4 ROs in the frequency domain (i.e., a parameter (e.g., msg1-FDM) can indicate that there are 4 RO opportunities in the frequency domain, i.e., Msg1-FDM = 4).

[0072] An RO can be associated with a Synchronization Signal and Physical Broadcast Channel block (SSB). One SSB can be transmitted with a specific beam. The SSB can consist of a Primary Synchronization Signal (PSS) or a Secondary Synchronization Signal (SSS) and a PBCH to enable the UE to synchronize to the DL, obtain the cell ID, and acquire the primary system information. The UE can measure the channel state of each SSB, select the SSB with good (optimal) channel quality, and transmit the preamble in the RO associated with the SSB with good (optimal) channel quality. Thus, the preamble can be received at the BS through an appropriate receiving beam, which can correspond to the beam selected for SSB transmission.

[0073] Figures 4A to 4C Describe some types of associations between ROs and SSBs according to some embodiments of the present disclosure.

[0074] There can be different types of associations between SSBs (beams) and ROs. Depending on the network configuration, the association between an SSB and an RO can include: 1-to-1, 1-to-N, or N-to-1. The association can be determined by a parameter (e.g., SSB-PerRACH-Occasion).

[0075] Figure 4ADescribe the one-to-one association between SSB and RO. The parameter SSB-PerRACH-Occasion can be configured with the value 1, i.e., SSB-PerRACH-Occasion = 1. That is, one SSB can be associated with one RO. For example, SSB#0 can be associated with RO#0, SSB#1 can be associated with RO#1, and so on.

[0076] Figure 4B Describe the N-to-one association between SSB and RO. The parameter SSB-PerRACH-Occasion can be configured with the value 2, i.e., SSB-PerRACH-Occasion = 2. That is, two SSBs can be associated with one RO. For example, SSB#0 and SSB#1 can be associated with RO#0, SSB#2 and SSB#3 can be associated with RO#1, and so on.

[0077] Figure 4C Describe the one-to-N association between SSB and RO. The parameter SSB-PerRACH-Occasion can be configured with the value 1 / 2, i.e., SSB-PerRACH-Occasion = 1 / 2. That is, one SSB can be associated with two ROs. For example, SSB#0 can be associated with RO#0 and RO#1, and the two ROs can be FDM in the frequency domain. SSB#1 can be associated with RO#2 and RO#3, and so on.

[0078] The association between SSB and RO can be performed in the SSB-to-RO association period. The SSB-to-RO association period can be the number of times of the PRACH configuration period (e.g., the PRACH configuration period described in Figure 3 ), and can include one or more SSB-to-RO mapping cycles. The duration of the SSB-to-RO association period can be the minimum period such that within the SSB-to-RO association period, each SSB can be associated with at least one RO. In some embodiments, there may be some ROs within the association period that are not associated with any SSB, and these ROs are not used for PRACH transmission, and they can be referred to as unused ROs.

[0079] Figure 5 Describe the SSB-to-RO association period according to some embodiments of the present disclosure.

[0080] In Figure 5 There are two SSB-to-RO association periods. Each SSB-to-RO association period can include two SSB mapping cycles, and there are two unused ROs within each SSB-to-RO association period. More specifically, two ROs are associated with SSB#0, two ROs are associated with SSB#1, two ROs are associated with SSB#2, and two ROs are associated with SSB#3, as well as two unused ROs.

[0081] It should be noted that although in Figure 5 and other accompanying drawings (e.g., Figure 4A , 4B and 4C), the RO may be continuous, but in some other scenarios, such as in a TDD system where the RO is configured in discontinuous UL time slots, the RO may not be continuous. For these scenarios including continuous RO or discontinuous RO, the solutions of the present disclosure are still applicable.

[0082] The PRACH preamble can be transmitted without repetition. In some cases, for example, a short PRACH format (e.g., PRACH format B) can be used, and this format may be a bottleneck channel. Therefore, the PRACH coverage should be restored for at least some PRACH formats. PRACH repeated transmission can be used to restore the PRACH coverage.

[0083] However, PRACH repeated transmission may have a high transmission delay because it can be performed in the UL time slots of multiple DL / UL configuration modes in a TDD system.

[0084] In addition, for both TDD and frequency division duplex (FDD) systems, in order to use joint detection for PRACH repetition, the BS and the UE should know the time domain starting position for PRACH repetition (i.e., the starting RO position), otherwise the BS may not know which group of ROs is used for PRACH repetition. As a solution, an RO bundle is introduced and PRACH repetition is transmitted in the ROs within the RO bundle. Correspondingly, the starting RO of the RO bundle is the starting RO for PRACH repetition. Based on this structure, once the UE initiates a PRACH process, it may not start PRACH transmission until the starting RO of the RO bundle.

[0085] Figure 6 Describe the PRACH repeated transmission in the RO bundle according to some embodiments of the present disclosure.

[0086] In Figure 6 , there are four SSB-to-RO association periods. Each SSB-to-RO association period may include two ROs respectively associated with SSB#0, SSB#1, SSB#2, and SSB#3. The number of PRACH repetitions is 4. Correspondingly, 4 ROs are required for PRACH repetition. The RO bundle containing 4 ROs can be associated with the same SSB. For example, in Figure 6 , there are two RO bundles each containing 4 ROs associated with SSB#0, such as RO bundle #0 and RO bundle #1. The UE can select SSB#0 and can transmit PRACH repetition in the ROs associated with SSB#0. When an event triggers PRACH repetition, for example, the event may occur at the time of the RO associated with SSB#3 in the first SSB-to-RO association period, asFigure 6 As shown in Figure 6 , the UE may not perform PRACH transmission until the start position of the RO burst. That is, the UE may not perform PRACH repeated transmission in RO burst #0, and may perform PRACH repeated transmission in RO burst #1. It can be seen that this long waiting time may present a high PRACH transmission delay.

[0087] To reduce the PRACH transmission delay, the present disclosure proposes a denser starting RO for PRACH repetition. The UE (or BS) may determine a set of candidate starting ROs for PRACH repetition, where the time gap between two adjacent candidate starting ROs (in terms of the number of ROs associated with the same SSB) may be the same as or lower than the number of ROs for PRACH repetition. By having this denser set of candidate starting ROs, the UE may wait less time to start the RACH procedure. Therefore, the PRACH transmission delay can be reduced.

[0088] Solution 1

[0089] In Solution 1, the UE (or BS) may determine candidate starting ROs for PRACH repetition within an RO burst. The RO burst may contain a set of ROs associated with the same SSB. The first RO burst associated with a specific SSB may start from the first RO associated with the SSB in frame 0. Hereinafter, in the present disclosure, for clarity, the number of PRACH repetitions may be denoted as "N". PRACH repetition requires N ROs.

[0090] Solution 1-1:

[0091] In some embodiments, for an SSB (which may be any SSB configured for RO association), the number of ROs associated with the SSB (or any SSB configured for RO association) in one RO burst may be in the range from 1 to N-1. That is, one RO burst may contain at least one RO and may have a smaller number of ROs than the PRACH repetition. In this case, the candidate starting RO may be the first RO in each RO burst. Therefore, the UE (or BS) may select the starting RO from the candidate starting ROs (i.e., the first RO in each RO burst). On the UE side, the number of ROs in the RO burst may be determined based on the configuration from the base station or may be predefined.

[0092] Figure 7 Illustrate the PRACH repeated transmission in the RO burst according to some embodiments of the present disclosure.

[0093] In Figure 7There are four SSB-to-RO association periods. Each SSB-to-RO association period may include two ROs respectively associated with SSB#0, SSB#1, SSB#2, and SSB#3. Based on the BS configuration, a beam may include two ROs associated with the same SSB. For example, for SSB#0, there are four RO beams, namely RO beam

[0094] #0, RO beam #1, RO beam #2, and RO beam #3. Each RO beam includes two ROs associated with SSB#0. Each first RO in the RO beam is a candidate starting RO for PRACH repetition. That is, the UE can start PRACH repetition from the candidate starting RO.

[0095] The number of PRACH repetitions is 4. Correspondingly, 4 ROs are required for PRACH repetition. The UE can select SSB#0 and can transmit PRACH repetition in the ROs associated with SSB#0. When an event triggers PRACH repetition, for example, the event may occur at the time of the RO associated with SSB#3 in the first SSB-to-RO association period, as Figure 7 shown, the UE can select the nearest candidate starting RO (relative to the event), that is, the candidate starting RO closest to the event among all candidate starting ROs, which is the first RO in the RO beam closest to the event, to transmit PRACH repetition. In this case, one PRACH repetition is transmitted in two RO beams (i.e., RO beam #1 and RO beam #2).

[0096] Solution 1-2:

[0097] In some other embodiments, for an SSB (which can be any SSB), the number of ROs associated with the SSB (or any SSB) in one RO beam can be N. That is, one RO beam can have the same number of ROs as the number of PRACH repetitions. In this case, the candidate starting RO can be determined based on the configuration that can be received from the BS, and the configuration can indicate at least one of the following:

[0098] a) A set of candidate starting RO indices within the RO beam. This may require indexing the ROs within each RO beam;

[0099] b) At least one RO offset within the RO beam. The RO offset can indicate the number of ROs relative to the first RO in the RO beam; or

[0100] c) The number of candidate starting ROs in the RO beam.

[0101] The first RO in the RO beam can always be regarded as a candidate starting RO, and other candidate starting ROs can be determined based on the above indications in the configuration.

[0102] Figure 8 Describe the PRACH repeated transmission in the RO beam according to some embodiments of the present disclosure.

[0103] In Figure 8 there are four SSB-to-RO association periods. Each SSB-to-RO association period may include two ROs respectively associated with SSB#0, SSB#1, SSB#2, and SSB#3. One RO beam may include four ROs associated with the same SSB, and the four ROs in one beam may be the four ROs in two SSB-to-RO association periods. For example, for SSB#0, there are two RO beams, namely RO beam #0 and RO beam #1. Each first RO in the RO beam may be a candidate starting RO for PRACH repetition.

[0104] The configuration may indicate:

[0105] a) A set of candidate starting RO indices within the RO beam. For example, taking RO beam #0 as an example, the four ROs associated with SSB#0 may be indexed as RO#0, RO#1, RO#2, and RO#3 within RO beam #0. The set of candidate starting RO indices within the RO beam may include: {RO#0, RO#2}. Therefore, as shown in Figure 8 there are two candidate starting ROs in RO beam #0 and RO beam #1.

[0106] b) At least one RO offset within the RO beam. For example, the offset value may be 2. In this case, the first RO in the RO beam that can be indexed as RO#0 may be a candidate starting RO, and the third RO that can be indexed as candidate starting RO#2 has an offset value of 2 relative to candidate starting RO#0 and is also a candidate starting RO.

[0107] c) The total number of candidate starting ROs in the RO beam. For example, the number of candidate starting ROs in one RO beam may be 2. In this case, the first RO in the RO beam and the third RO in one RO beam may be regarded as two candidate starting ROs.

[0108] The number of PRACH repetitions is 4. Correspondingly, 4 ROs are required for PRACH repetition. The UE may select SSB#0 and transmit PRACH repetition in the RO associated with SSB#0. Based on the above configuration, the UE can determine two candidate starting ROs in each RO beam. When an event triggers the PRACH process, the UE can select the candidate starting RO closest to the event in the RO beam to transmit PRACH repetition. Therefore, the UE can select the second candidate starting RO in RO beam #0 and perform PRACH repeated transmission.

[0109] Solution 2

[0110] In this solution, the UE can receive a configuration indicating the configured time periodicity for candidate starting ROs, and the UE can determine candidate starting ROs for PRACH repetition based at least on the configured time periodicity of the candidate starting ROs. The periodicity is based on the number of ROs associated with the same SSB. For example, if SSB#0 is selected by the UE, the periodicity is based on the number of ROs associated with SSB#0.

[0111] To determine candidate starting ROs based on the periodicity, the ROs associated with the same SSB can be indexed. The indexing can start from the first RO associated with the SSB in frame 0. Hereinafter, in this disclosure, for clarity, the periodicity can be denoted as “K”. Assume that the ROs associated with an SSB (e.g., SSB#0) for PRACH repetition can be indexed as: RO#0, RO#1, RO#2, RO#1, RO#3… The candidate starting ROs associated with the SSB for PRACH repetition can include: RO#0, RO#(K−1), …, RO#(m×K−1), where K is the periodicity of the candidate starting ROs, and m is an integer equal to or greater than 2.

[0112] In some embodiments, the configuration can further indicate an RO offset, which can be denoted as “j” for clarity. In this case, the candidate starting ROs associated with the SSB for PRACH repetition will be RO#j, RO#(j+K−1), … RO#(j+m×K−1), …, where K is the periodicity of the candidate starting ROs, m is an integer equal to or greater than 2, and j is the RO offset.

[0113] Figure 9 Describe PRACH repetitive transmission according to some embodiments of the present disclosure.

[0114] In Figure 9 there are four SSB-to-RO association periods. Each SSB-to-RO association period can include two ROs associated with SSB#0, SSB#1, SSB#2, and SSB#3 respectively. Taking SSB#0 as an example, the ROs associated with SSB#0 can be indexed as: RO#0, RO#1, RO#2, …, RO#7. The number of PRACH repetitions can be 4, and the candidate starting RO periodicity can be indicated as 2.

[0115] Therefore, the candidate starting ROs associated with SSB#0 can include: RO#0, RO#2, RO#4, and RO#6. When an event triggers PRACH repetition, for example, the event can occur at the time of the RO associated with SSB#3 in the first SSB-to-RO association period, as shown in Figure 9 the UE can select the nearest candidate starting RO (i.e., RO#2) to transmit PRACH repetition.

[0116] Although such ROs associated with any SSB are not shown in Figures 6 to 9 (e.g., the "unused ROs" shown in Figure 5 ), those skilled in the art should understand that these figures are merely illustrative and do not represent limitations. More specifically, the SSB-to-RO association period may or may not include unused ROs, which does not affect the implementation of the above solutions.

[0117] Solution 3

[0118] In this solution, a period can be defined. The period can be referred to as the "PRACH repetition period", "new SSB-to-RO association period", "SSB-to-RO association period", "new SSB-to-RO association period for PRACH repetition", or "SSB-to-RO association period for PRACH repetition" or the like. Hereinafter, in this disclosure, the expression "proposed SSB-to-RO association period" can be used to describe the solution. It should be noted that the proposed SSB-to-RO association period is still a type of SSB-to-RO association period.

[0119] In some embodiments, the proposed SSB-to-RO association period may include one or more SSB-to-RO association periods. A candidate starting RO can be determined within each proposed SSB-to-RO association period.

[0120] In some embodiments, the proposed SSB-to-RO association period can be determined based on the number of PRACH repetitions. The association period for mapping SSB to RO for PRACH repetition starting from frame 0 may include at least one PRACH configuration period (e.g., the PRACH configuration period shown in Figure 3 ), and each SSB can be associated with at least N ROs within the proposed SSB-to-RO association period, where N is the number of PRACH repetitions.

[0121] In some embodiments, the proposed SSB-to-RO association period can be determined such that each SSB is associated with LxN ROs, where N is the number of PRACH repetitions and L is an integer with a value predefined or configured by the BS.

[0122] In some embodiments, after associating the SSB with the RO, there are some ROs in the proposed SSB-to-RO association period that are not associated with any SSB. These ROs may not be used for PRACH transmission and can be referred to as unused ROs.

[0123] Figure 10 Illustrate the proposed SSB-to-RO association period according to some embodiments of the present disclosure.

[0124] InFigure 10 In this case, the number of PRACH repetitions can be 4. In the SSB-to-RO association period, in one SSB-to-RO association period, one SSB is associated with two ROs, and there are two ROs that are not associated with any SSB. Therefore, there are two unused ROs in each SSB-to-RO association period. Assume that SSB#0 is selected, and for the PRACH repeated transmission, it involves two ROs associated with SSB#0 in one SSB-to-RO association period and another two ROs associated with SSB#0 in the next SSB-to-RO association period. The existence of the two unused ROs makes the PRACH repeated transmission delay larger.

[0125] In the proposed SSB-to-RO association period, one SSB is associated with four ROs (which is the same as the number of PRACH repetitions). It can be observed that, different from the PRACH repetition based on the SSB-to-RO association, there are no unused ROs during the PRACH repetition for the proposed SSB-to-RO association period. For example, there are no unused ROs among the four ROs associated with SSB#0. Therefore, compared with the PRACH repeated transmission delay of the SSB-to-RO association period, the PRACH transmission delay is reduced.

[0126] With the proposed SSB-to-RO association period, the PRACH repetition is always transmitted within a proposed SSB-to-RO association period. In some other embodiments, a proposed SSB-to-RO association mode period is proposed, which may include at least one proposed SSB-to-RO association period.

[0127] For each proposed SSB-to-RO association period, one or more candidate starting ROs can be determined. The number of candidate starting ROs can depend at least on the total number of ROs associated with the SSB in the association period and / or the configuration used for the candidate starting RO determination. Details are as follows:

[0128] Assume that a proposed SSB-to-RO association period can include L×N ROs associated with one SSB, where N is the number of PRACH repetitions, and L can be an integer equal to or greater than 1. Therefore, within the proposed SSB-to-RO association period, there are L candidate starting ROs for the PRACH repetition. The L candidate starting ROs can be determined by the following options:

[0129] Option 1:

[0130] One or more RO bundles can be defined within each proposed SSB-to-RO association period, where each RO bundle can contain N ROs associated with the same SSB. For an SSB, the first RO in the first RO bundle is the first RO associated with the SSB in the proposed association period. Since a proposed SSB-to-RO association period can contain L×N ROs associated with the SSB, correspondingly, L RO bundles can be determined within each proposed SSB-to-RO association period. The first RO in the RO bundle can be determined as the candidate starting RO for PRACH repetition.

[0131] Option 2:

[0132] The ROs associated with the same SSB within the proposed SSB-to-RO association period are indexed. The indexing can start from 0, so the ROs associated with the same SSB can include: RO#0, RO#1, RO#2, … RO#(L×N−1). The index of the candidate starting RO can be calculated as follows: mod(RO_index,N)=0, where N is the number of PRACH repetitions and RO_index is the RO index within the SSB-to-RO association period. Alternatively, the index of the candidate starting RO can be a value divisible by N. That is, the index of the candidate starting RO can include: RO#0, RO#N, RO#(2×N), … RO#((L−1)×N).

[0133] Alternatively, the candidate starting RO can include: RO#0, RO#1, RO#2, … RO#((L−1)×N). In the case where the determined starting RO is RO#0, PRACH repeated transmission can be performed from RO#0 to RO#(N−1); in the case where the determined starting RO is RO#1, PRACH repeated transmission can be performed from RO#1 to RO#N; and in the case where the determined starting RO is RO#((L−1)×N), PRACH repeated transmission can be performed from RO#((L−1)×N) to RO#(L×N−1).

[0134] Option 3:

[0135] The UE (or BS) can determine the candidate starting RO within the proposed SSB-to-RO association period based on the above Solution 1 or Solution 2. The difference is that the candidate starting RO is determined for each SSB-to-RO association period. For example, the candidate starting RO can be determined based on Solution 1 (e.g., Solution 1 to 2), but the RO bundles are determined within the proposed SSB-to-RO association period. Alternatively, the candidate starting RO can be determined based on Solution 2, but the RO index for candidate starting RO determination is within the proposed SSB-to-RO association period.

[0136] For example, L RO beams are determined within each proposed SSB-to-RO association period. Except for the first RO in the RO beam that is determined to be the candidate starting RO for PRACH repetition, the UE can determine another candidate starting RO in a RO beam in a similar manner to Solutions 1 to 2.

[0137] Figure 11 Describe the proposed SSB-to-RO association period according to some embodiments of the present disclosure.

[0138] The number of PRACH repetition times is 2, and a proposed SSB-to-RO association period may include 4 ROs associated with each SSB. Taking SSB#0 as an example, there are four ROs associated with SSB#0, which include: RO#0, RO#1, RO#2, and RO#3. The UE can determine at most 3 candidate starting ROs within the proposed SSB-to-RO association period, which may include: RO#0, RO#1, RO#2. In the case where the determined starting RO is RO#0, PRACH repeated transmissions can be performed in RO#0 and RO#1; in the case where the determined starting RO is RO#1, PRACH repeated transmissions can be performed in RO#1 and RO#2; and in the case where the determined starting RO is RO#2, PRACH repeated transmissions can be performed in RO#2 and RO#3.

[0139] In this way, the PRACH repetition is always transmitted within the proposed SSB-to-RO association period.

[0140] Based on the proposed denser candidate starting ROs for PRACH repetition, there may be overlapping ROs involving more than one PRACH repetition. For example, referring to Figure 11 , one UE can perform PRACH repeated transmissions in RO#1 and RO#2, and another UE can perform PRACH repeated transmissions in RO#2 and RO#3. RO#2 is involved in the PRACH repetition of two UEs.

[0141] In order to distinguish each PRACH repetition in the case of this overlapping RO and facilitate the BS to detect the PRACH preamble, it is proposed to partition the PRACH preamble for the candidate starting RO.

[0142] Specifically, a preamble group can be determined and associated with the candidate starting RO. Different candidate starting ROs can be associated with different preamble groups. On the UE side, if it decides to start PRACH repetition from a specific candidate starting RO, then it will select a preamble from the preamble group associated with the candidate starting RO, and can start preamble transmission from the candidate starting RO.

[0143] The total number of preamble groups can be determined by the number of PRACH repetitions (e.g., N) and the density of candidate starting ROs. The candidate starting RO density can be the candidate starting RO periodicity, or the maximum time gap (in terms of the number of ROs) between two adjacent candidate starting ROs for PRACH repetition. The number of preamble groups can be calculated as: N / N_density, where N is the number of PRACH repetitions and N_density is the density of candidate starting ROs. In some embodiments, for the determined preamble groups, the preambles can be equally divided.

[0144] Figure 12 Describe a preamble partitioning method for PRACH repetition according to some embodiments of the present disclosure.

[0145] In Figure 12 PRACH repetition is 4 and the candidate starting RO periodicity is 1. Correspondingly, the UE can determine 4 preamble groups, which can include preamble group #0, preamble group #1, preamble group #2, and preamble group #3, and each preamble group is associated with a candidate starting RO. For example, candidate starting RO #0 can be associated with preamble group #0; candidate starting RO #1 can be associated with preamble group #1; candidate starting RO #2 can be associated with preamble group #2; and candidate starting RO #3 can be associated with preamble group #3.

[0146] Figure 13 Describe a method performed by a UE for wireless communication according to some embodiments of the present disclosure.

[0147] In operation 1301, the UE can receive a first configuration associated with PRACH repetition. In operation 1302, the UE can determine ROs for PRACH repetition based on a first total number of PRACH repetitions configured by the first configuration.

[0148] Figure 14 Describe a method performed by a BS for wireless communication according to some embodiments of the present disclosure.

[0149] In operation 1401, the BS can transmit a first configuration associated with PRACH repetition; and in operation 1402, the BS can determine ROs for PRACH repetition based on the first total number of PRACH repetitions.

[0150] In some embodiments, the ROs for PRACH repetition are included in at least one RO bundle, and the bundle includes a set of ROs associated with an SSB, and the UE or the BS determines the first RO in the RO bundle as the starting RO for PRACH repetition.

[0151] In some embodiments, a first RO bundle associated with the SSB starts from a first RO associated with the SSB in a first frame. The first frame may be frame 0.

[0152] In some embodiments, the ROs for PRACH repetition are included in a RO bundle, and the RO bundle includes the first total number of ROs associated with the SSB, and the processor is further configured to receive a second configuration that indicates one of: a set of indices of candidate start ROs of the RO bundle; an offset associated with the first RO in the RO bundle; or the total number of candidate start ROs in the RO bundle.

[0153] In some embodiments, the UE or the BS may determine a start RO of the ROs for PRACH repetition, where the start RO in the RO bundle is one of: the first RO in the RO bundle; a candidate start RO identified by an index in the set of indices; or a candidate start RO having the offset associated with the first RO in the RO bundle. For example, in Figure 8 the set of candidate start RO indices within the RO bundle may include: {RO#0, RO#2}. Thus, as Figure 8 shown in there are two candidate start ROs in RO bundle #0 and RO bundle #1.

[0154] In some embodiments, the UE may receive a third configuration from the network (e.g., the BS) that indicates one of: the periodicity of candidate start ROs associated with the SSB; or the periodicity of candidate start ROs associated with the SSB and the offset associated with the first RO.

[0155] In some embodiments, the UE or the BS may determine a set of candidate start ROs based on the periodicity or based on the periodicity and the offset, where the first candidate start RO is the first RO associated with the SSB in the first frame. For example, in Figure 9 the periodicity may be 2, and the candidate start ROs associated with SSB#0 may include: RO#0, RO#2, RO#4, and RO#6.

[0156] In some embodiments, the UE or the BS may determine a period based on the first total number of PRACH repetitions and a second total number of ROs associated with the SSB from a set of SSBs in a period, and where the second total number of ROs is equal to or greater than the first total number of ROs. In some embodiments, the second total number is an integer multiple of the first total number.

[0157] In some embodiments, the period is an SSB-to-RO association period or an SSB-to-RO association pattern period, where the SSB-to-RO association pattern period includes at least one SSB-to-RO association period.

[0158] In some embodiments, the period includes a number of RO bundles, each RO bundle includes a set of ROs associated with the SSB, and the number of ROs in the set is equal to or less than the first total number.

[0159] In some embodiments, a candidate starting RO for PRACH repetition is the first RO in an RO bundle.

[0160] In some embodiments, each RO associated with the SSB in the period is indexed, and the first RO associated with the SSB in the period is a candidate starting RO, and an RO having an index value divisible by the first total number is a candidate starting RO. For example, if the index starts from 0, then the ROs associated with the same SSB may include: RO#0, RO#N, RO#(2×N), … RO#((L - 1)×N).

[0161] In some embodiments, the candidate starting RO of the RO for PRACH repetition is associated with a preamble group.

[0162] In some embodiments, the total number of preambles in the preamble group is determined by the first total number and the density of candidate starting ROs in a period determined based on the first total number of the PRACH repetition.

[0163] In some embodiments, the UE or the BS may determine an RO other than the starting RO for PRACH repetition as an RO associated with the same SSB and after the starting RO in the time domain, where it is associated with the same SSB in the starting RO. For example, in Figure 9 where the starting RO associated with SSB#0 is the RO with index 2, i.e., RO#2, and the other ROs for PRACH repetition include RO#3, RO#4, and RO#5.

[0164] Figure 15 Illustrate a simplified block diagram of a device according to some embodiments of the present disclosure.

[0165] As Figure 15 shown, an example of device 1500 may include at least one processor 1504 and at least one transceiver 1502 coupled to the processor 1504. Device 1500 may be a UE, a BS, or any other device with similar functions.

[0166] Although elements such as at least one transceiver 1502 and processor 1504 are described in the singular in this figure, the plural forms are contemplated unless expressly stated to be limited to the singular form. In some embodiments of the present disclosure, the transceiver 1502 may be divided into two devices, such as a receiving circuit system and a transmitting circuit system. In some embodiments of the present disclosure, the device 1500 may further include an input device, a memory, and / or other components.

[0167] According to some embodiments of the present disclosure, the device 1500 may be a UE. The transceiver 1502 and the processor 1504 may interact with each other to perform the operations of the UE described in any of Figures 1 to 14 According to some embodiments of the present disclosure, the device 1500 may be a BS. The transceiver 1502 and the processor 1504 may interact with each other to perform the operations of the BS described in any of Figures 1 to 14 In some embodiments of the present disclosure, the device 1500 may further include at least one non-transitory computer-readable medium.

[0168] For example, in some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 1504 to implement the method for the UE described above. For example, when the computer-executable instructions are executed, they cause the processor 1504 to interact with the transceiver 1502 to perform the operations of the UE described in any of

[0169] In some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 1504 to implement the method for the BS described above. For example, when the computer-executable instructions are executed, they cause the processor 1504 to interact with the transceiver 1502 to perform the operations of the BS described in any of Figures 1 to 14 In some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 1504 to implement the method for the BS described above. For example, when the computer-executable instructions are executed, they cause the processor 1504 to interact with the transceiver 1502 to perform the operations of the BS described in any of

[0170] In some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 1504 to implement the method for the BS described above. For example, when the computer-executable instructions are executed, they cause the processor 1504 to interact with the transceiver 1502 to perform the operations of the BS described in any of Figures 1 to 14 In some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 1504 to implement the method for the BS described above. For example, when the computer-executable instructions are executed, they cause the processor 1504 to interact with the transceiver 1502 to perform the operations of the BS described in any of

[0171] The methods of the present disclosure may be implemented on a programmed processor. However, the controller, flowchart, and module may also be implemented on a general-purpose or special-purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware electronic or logic circuit (such as a discrete element circuit), a programmable logic device, or the like. Generally, any device having a finite state machine capable of implementing the flowchart shown in the figures may be used to implement the processing functions of the present disclosure.

[0172] Although the present disclosure has been described with reference to specific embodiments thereof, it will be apparent that many alternatives, modifications and variations will be apparent to those skilled in the art. For example, the various components of the embodiments may be interchanged, added or substituted in other embodiments. Moreover, all of the elements shown in each figure are not necessary for the operation of the disclosed embodiments. For example, those skilled in the art of the disclosed embodiments will be able to make and use the teachings of the present disclosure by simply employing the elements of the independent claims. Accordingly, the embodiments of the present disclosure set forth herein are intended to be illustrative rather than limiting. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0173] In the present disclosure, relative terms such as "first", "second" and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The term "comprise / comprising" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article or apparatus. An element that begins with "a / an" or the like does not, without further limitation, preclude the presence of additional identical elements in the process, method, article or apparatus that includes the element. Moreover, the term "another" is defined as at least a second or more. As used herein, the terms "comprising", "having" and the like are defined as "including".

Claims

1. A user equipment (UE) comprising: a transceiver; and a processor coupled to the transceiver and configured to: receive a first configuration associated with physical random access channel (PRACH) repetitions; and determine a random access channel occasion (RO) for PRACH repetitions based on a first total number of PRACH repetitions configured by the first configuration.

2. The UE according to claim 1, wherein the RO for PRACH repetitions is included in at least one RO bundle, and wherein the RO bundle includes a set of ROs associated with a synchronization signal and a physical broadcast channel (PBCH) block (SSB), and the processor is further configured to: determine a first RO in the RO bundle as a starting RO for PRACH repetitions.

3. The UE according to claim 1, wherein the RO for PRACH repetitions is included in an RO bundle, and wherein the RO bundle includes the first total number of ROs associated with the SSB, and the processor is further configured to receive a second configuration indicating one of the following: a set of indices of candidate starting ROs in the RO bundle; an offset associated with a first RO in the RO bundle; or a total number of candidate starting ROs in the RO bundle.

4. The UE according to claim 3, wherein the processor is further configured to: determine a starting RO of the ROs for PRACH repetitions, wherein the starting RO in the RO bundle is one of the following: the first RO in the RO bundle; a candidate starting RO identified by an index in the set of indices; or a candidate starting RO having the offset associated with the first RO in the RO bundle.

5. The UE according to claim 1, wherein the processor is further configured to receive a third configuration indicating one of the following: a periodicity of candidate starting ROs associated with the SSB; or the periodicity of the candidate starting ROs associated with the SSB and an offset associated with the first RO.

6. The UE according to claim 5, wherein the processor is further configured to: determine a set of candidate starting ROs based on the periodicity or based on the periodicity and the offset, wherein a first candidate starting RO is the first RO associated with the SSB in a first frame.

7. The UE according to claim 1, wherein the processor is further configured to determine the period based on the first total number of PRACH repetitions and a second total number of ROs associated with the SSB from a set of SSBs in a period, and wherein the second total number of ROs is equal to or greater than the first total number of PRACH repetitions.

8. The UE according to claim 7, wherein the period is an SSB-to-RO association period or an SSB-to-RO association pattern period, and wherein the SSB-to-RO association pattern period includes at least one SSB-to-RO association period.

9. The UE according to claim 7, wherein the period includes a plurality of RO bundles, each RO bundle includes a group of ROs associated with the SSB, and the number of ROs in the group is equal to or less than the first total number.

10. The UE according to claim 9, wherein the candidate starting RO for PRACH repetition is the first RO in the RO bundle.

11. The UE according to claim 7, wherein each RO associated with the SSB in the period is indexed, and the first RO associated with the SSB in the period is the candidate starting RO, and the RO having an index value divisible by the first total number is the candidate starting RO.

12. The UE according to claim 1, wherein the candidate starting RO of the RO for PRACH repetition is associated with a preamble group.

13. The UE according to claim 12, wherein the total number of preambles in the preamble group is determined by the first total number and the density of candidate starting ROs in the period determined based on the first total number of PRACH repetitions.

14. A base station BS, comprising: a transceiver; and a processor coupled to the transceiver and configured to: transmit a first configuration associated with physical random access channel PRACH repetition; and determine a random access channel opportunity RO for receiving PRACH repetition based on a first total number of PRACH repetitions.

15. A method performed by a base station BS, comprising: transmitting a first configuration associated with physical random access channel PRACH repetition; and determining a random access channel opportunity RO for receiving PRACH repetition based on a first total number of PRACH repetitions.

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