Method and apparatus for PRACH repetition

Abstract

Embodiments of the present application relate to methods and devices for physical random access channel (PRACH) repetition. The method according to an embodiment of the present application includes: receiving signaling information for indicating a synchronization signal block (SSB) group size; mapping indices of a plurality of SSBs to a plurality of PRACH opportunities for performing a plurality of physical random access channel (PRACH) repetitions, wherein the plurality of SSBs are divided into one or more SSB groups based on the indicated SSB group size; and determining a set of PRACH opportunities corresponding to one of the indices of the plurality of SSBs from the plurality of PRACH opportunities based on the mapping.

Description

Technical Field

[0001] Embodiments of the present application generally relate to wireless communication technology, and more particularly, to a method and apparatus for physical random access channel (PRACH) repetition. Background Art

[0002] Under New Radio (NR) light, due to the constraints of the number of uplink transmission (Tx) antennas and the uplink transmission power, PRACH repetition in the time domain, i.e., repeating PRACH transmission for the same PRACH preamble in the time domain is necessary to achieve the same uplink coverage as legacy technologies such as NR R15.

[0003] However, in order to implement PRACH repetition, several issues need to be addressed. For example, in the case of mapping a synchronization signal block (SSB) to a PRACH opportunity for PRACH repetition, when there are more than one time domain PRACH opportunities mapped to an SSB in a mapping cycle, it should be determined whether to first traverse the SSB in the order of the index or to repeat the PRACH transmission first, so that both the network side and the UE side have the same understanding of the mapping. At the same time, without any enhancement, the PRACH repetitions for a specific SSB will be scattered in the time domain, which will result in a considerable amount of random access. In addition, the maximum number of PRACH repetitions supported by a PRACH opportunity in the time domain, and coexistence with legacy technologies, etc. should also be considered.

[0004] Therefore, there is a need to further supplement and improve the technical solutions for PRACH repetition, for example, the mapping between SSB and PRACH opportunities. Summary of the invention

[0005] One objective of an embodiment of the present application is to provide a technical solution for PRACH repetition, in particular, a mapping mechanism between SSB and PRACH opportunities for PRACH repetition.

[0006] Some embodiments of the present application provide a method, which includes: receiving signaling information for indicating a synchronization signal block (SSD) group size; mapping indices of multiple SSBs to multiple RACH opportunities for performing several physical random access channel (PRACH) P repetitions, wherein the multiple SSBs are divided into one or more SSB groups based on the indicated SSB group size; and based on the mapping, determining a group of PRACH opportunities corresponding to one of the indices of the multiple SSBs from the multiple PRACH opportunities.

[0007] Some other embodiments of the present application provide a method, which includes: transmitting signaling information for indicating a synchronization signal block (SSD) group size; mapping indices of multiple SSBs to multiple physical random access channel (PRACH) opportunities for performing multiple PRACH repetitions, wherein the multiple SSBs are divided into one or more SSB groups based on the SSB group size; and based on the mapping, responding to PRACH preamble codes transmitted on multiple PRACH opportunities corresponding to one of the indices of the multiple SSBs.

[0008] Some other embodiments of the present application provide an apparatus. The apparatus includes: a non-transitory computer-readable medium having computer-executable instructions stored thereon; a receiving circuit system; a transmitting circuit system; and a processor coupled to the non-transitory computer-readable medium, the receiving circuit system, and the transmitting circuit system, wherein the computer-executable instructions cause the processor to implement any of the above-mentioned methods.

[0009] The embodiments of the present application propose a technical solution for PRACH repetition, in particular, for mapping between SSB and PRACH opportunities for PRACH repetition. At the same time, the embodiments of the present application consider coexistence with traditional technologies. Therefore, the embodiments of the present application will greatly promote the implementation of 5G NR including NR light. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to describe the manner in which the advantages and features of the present application can be obtained, the description of the present application is presented by reference to specific embodiments thereof which are illustrated in the accompanying drawings. These drawings depict only example embodiments of the present application and therefore should not be considered limiting of its scope.

[0011] Figures 1 to 4 An exemplary embodiment of mapping between SSBs and PRACH opportunities depending on a specific setting of "msg1-FDM" and "ssb-perRACH-OccasionAndCBPreamblesPerSSB" is described;

[0012] Figure 5 Describe an exemplary mapping between SSB and PRACH opportunities according to some embodiments of the present application;

[0013] Fig. 6A and Figure 6B Exemplary mappings between SSB and PRACH opportunities according to some embodiments of the present application are respectively described;

[0014] Figure 7 An exemplary method for performing PRACH repetition according to some embodiments of the present application is described;

[0015] Figure 8Another exemplary method for performing PRACH repetition according to some other embodiments of the present application is described;

[0016] FIG. 9A illustrates an exemplary mapping between SSB and PRACH opportunities under the mechanism of PRACH repetition start position cycling according to some embodiments of the present application, further comprising FIG. 9A-1 corresponding to a first mapping cycle, FIG. 9A-2 corresponding to a second mapping cycle, and FIG. 9A-3 corresponding to a third mapping cycle;

[0017] FIG. 9B illustrates an exemplary mapping between SSB and PRACH opportunities under the mechanism of PRACH repetition start position cycling according to some other embodiments of the present application, further comprising FIG. 9B-1 corresponding to a first mapping cycle, FIG. 9B-2 corresponding to a second mapping cycle, and FIG. 9B-3 corresponding to a third mapping cycle; and

[0018] Fig.10 A block diagram illustrating an exemplary apparatus according to some embodiments of the present application. DETAILED DESCRIPTION

[0019] The detailed description of the accompanying drawings is intended as a description of the preferred embodiments of the present application, and is not intended to represent the only form in which the present application can be practiced. It should be understood that the same or equivalent functions can be accomplished by different embodiments that are intended to be included in the spirit and scope of the present application.

[0020] Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architectures and new service scenarios (e.g., 3GPP 5G, 3GPP LTE Release 8, etc.). It is considered that, with the development of network architectures and new service scenarios, all embodiments in the present application are also applicable to similar technical problems; and in addition, the terms cited in the present application may be changed, which should not affect the principles of the present application.

[0021] PRACH evolved from the Random Access Channel (RACH) and has very important functionality especially in NR and Long Term Evolution (LTE) (and also in Wideband Code Division Multiple Access (WCDMA)). The main purpose of PRACH / RACH can be described as: i) achieving uplink synchronization between a user equipment (UE) such as a mobile phone and a base station (BS) such as an eNB; and (ii) obtaining resources for Message 3 (Msg3). There are several different types of Msg3 depending on the situation, for example, a Radio Resource Control (RRC) connection request.

[0022] In an exemplary scenario, when the UE is turned on, the UE will transmit a PRACH signal to the network side (e.g., BS). The PRACH signal is also called a "PRACH preamble" (preamble). A PRACH opportunity (RO) is a specified area in the time domain and frequency domain that can be used to transmit a PRACH preamble, and the time domain PRACH opportunity is the minimum time domain resource unit for PRACH preamble transmission. In LTE, all possible PRACH preambles share the same PRACH opportunity specified by an RRC message (e.g., SIB2), but it becomes more complicated in the NR case. In NR, different SSBs are associated with different beams, and the UE can select a specific beam (downlink spatial domain filter) and use that beam to send the PRACH preamble on the PRACH opportunity. NR R15 has defined a specific mapping relationship between SSBs (or SSB indexes for identifying SSBs) and PRACH opportunities, so that the network side can calculate which SSB or beam the UE has selected by detecting on which RO the UE sends the PRACH preamble. In other words, a PRACH opportunity is associated with an SSB or an SSB index to implicitly indicate the beam selected for downlink transmission and, if applicable, for uplink transmission.

[0023] Specifically, the mapping between SSB and PRACH opportunities may be defined by two RRC parameters defined in TS 38.331 f60, namely, “msg1-FDM” and “ssb-perRACH-OccasionAndCB-PreamblesPerSSB”, wherein although the parameter “ssb-perRACH-OccasionAndCB-PreamblesPerSSB” is expressed in a single manner, it may simultaneously express two sub-parameter values, namely, the value of “ssb-perRACH-Occasion” and the value of “CB-PreamblesPerSSB”. According to TS38.331 f60, "msg1-FDM" describes the number of PRACH transmission opportunities of frequency division multiplexing (FDM) in one moment, that is, "msg1-FDM" specifies how many ROs are allocated in the frequency domain (at the same position in the time domain); "ssb-perRACH-Occasion" describes the number of SSBs per RACH opportunity (time and frequency), and "CB-PreamblesPerSSB" describes the number of contention-based PRACH preambles per SSB, that is, "ssb-perRACH-OccasionAndCB-PreamblesPerSSB" specifies how many SSBs can be mapped to one RO and how many PRACH preambles can be mapped to a single SSB.

[0024] TS 38.213 f60 also describes the overall mapping logic as follows.

[0025] First, in increasing order of preamble index within a single PRACH opportunity

[0026] Secondly, in the increasing order of frequency resource index for PRACH opportunities used for frequency multiplexing

[0027] Third, in increasing order of time resource index of PRACH opportunities used for time multiplexing within a PRACH slot

[0028] Fourth, in increasing order of index within the PRACH time slot

[0029] The mapping between SSBs and PRACH opportunities is performed periodically. Depending on the specific settings of the two parameters "msg1-FDM" and "ssb-perRACH-OccasionAndCBPreamblesPerSSB", the number of time domain PRACH opportunities for all available SSBs in a mapping cycle can be one or more. According to NR R15, the total number of available SSBs is 64. That is, there are 64 available SSBs indexed from 0 to 63, i.e., SSB 0 to SSB 63. In each mapping cycle, the PRACH opportunities, also called "valid PRACH opportunities", will be mapped to the 64 available SSBs. In the future, the total number of available SSBs may change, which will not affect the principles of the present application.

[0030] Figures 1 to 4 An exemplary embodiment of the mapping between SSBs and PRACH opportunities depending on the specific settings of “msg1-FDM” and “ssb-perRACH-OccasionAndCBPreamblesPerSSB” is described.

[0031] Specifically, in Figure 1 In the embodiment shown in , both "msg1-FDM" and "ssb-perRACH-OccasionAndCBPreamblesPerSSB" are set to "1". That is, only one RO is allocated in the frequency domain at the same position in the time domain, and only one SSB (or SSB index) can be mapped to one RO. For example, RO#0, RO#1, RO#2, ..., RO#63 are respectively allocated in different positions in the time domain, and in the same position in the time domain, only one RO (e.g., RO#0, RO#1, RO#2, ..., or RO#63) is allocated in the frequency domain. Only SSB 0 can be mapped to RO#0, only SSB 1 can be mapped to RO#1, only SSB 2 can be mapped to RO#2, ..., only SSB 63 can be mapped to RO#63.

[0032] exist Figure 2In the embodiment shown in , "msg1-FDM" is set to "2", and "ssb-perRACH-OccasionAndCBPreamblesPerSSB" is set to "1". That is, two ROs are allocated at different positions in the frequency domain and at the same position in the time domain, and only one SSB (or SSB index) can be mapped to one RO. For example, RO#0 and RO#1 are allocated at different positions in the frequency domain and at the same position in the time domain, RO#2 and RO#3 are allocated in different positions in the frequency domain and in the same position in the time domain, which is similar to the following every two ROs, for example, RO#4 and RO#5, ..., and RO#62 and RO#63. Only SSB 0 can be mapped to RO#0, and only SSB 1 can be mapped to RO#1, which is similar to the following SSBs, for example, SSB 2, SSB 3, SSB 4, SSB 5, ..., SSB 62 and SSB 63.

[0033] exist Figure 3 In the embodiment shown in , "msg1-FDM" is set to "2", and "ssb-perRACH-OccasionAndCBPreamblesPerSSB" is set to "8". That is, two ROs are allocated at different positions in the frequency domain and at the same position in the time domain, and 8 SSBs (or SSB indexes) can be mapped to one RO. For example, RO#0 and RO#1 are allocated at different positions in the frequency domain and at the same position in the time domain, RO#2 and RO#3 are allocated in different positions in the frequency domain and in the same position in the time domain, and this is similar to every two ROs below, for example, RO#4 and RO#5, and RO#6 and RO#7. SSB 0 to 7 can be mapped to RO#0, SSB 8 to 15 can be mapped to RO#1, SSB 16 to 23 can be mapped to RO#2, SSB 24 to 31 can be mapped to RO#3, SSB 32 to 39 can be mapped to RO#4, SSB 40 to 47 can be mapped to RO#5, SSB 48 to 55 can be mapped to RO#6, and SSB 56 to 63 can be mapped to RO#7.

[0034] exist Figure 4In the embodiment shown in , "msg1-FDM" is still set to "2", and "ssb-perRACH-OccasionAndCBPreamblesPerSSB" is set to "1 / 2". That is, two ROs are allocated at different positions in the frequency domain and at the same position in the time domain, and one SSB (or SSB index) can be mapped to two ROs. Therefore, for 64 SSBs, there are 128 ROs to be mapped. For example, RO#0 and RO#1 are allocated at different positions in the frequency domain and at the same position in the time domain, RO#2 and RO#3 are allocated in different positions in the frequency domain and at the same position in the time domain, which is similar to every two ROs below, for example, RO#4 and RO#5, ..., RO#126 and RO#127. Each SSB can be mapped to two ROs in the same time domain, for example, SSB 0 can be mapped to RO#0 and RO#1, SSB 1 can be mapped to RO#2 and RO#3, SSB 2 can be mapped to RO#4 and RO#5, ..., SSB 63 can be mapped to RO#126 and RO#127.

[0035] Considering the constraints of the number of uplink transmission (Tx) antennas and uplink transmission power, PRACH repetition, i.e., repeating PRACH transmission for the same PRACH preamble code, is introduced into NR optical based on traditional technologies such as NR R15 to achieve the same uplink coverage as traditional technologies.

[0036] According to some embodiments of the present application, for several PRACH repetitions, multiple SSBs may be configured or predefined and divided into one or more SSB groups. The PRACH repetition number means that the PRACH transmission associated with the same PRACH preamble is repeated one or more times. The amount of multiple SSBs may be the same as or less than the amount of total available SSBs in NR R15, that is, 64 SSBs. The mapping between SSBs (or the index of SSBs, the same below) and PRACH opportunities (or valid PRACH opportunities, the same below) is performed based on SSB groups. At the same time, the mapping is performed periodically, and each mapping cycle is associated with the PRACH repetition number. Each mapping cycle may start from a configured or predefined time domain position (e.g., frame 0). For several PRACH repetitions, the duration of each mapping cycle is the minimum value of all indexes of multiple SSBs that can be mapped to multiple PRACH opportunities for several PRACH repetitions. During each mapping cycle, the overall mapping logic specified in TS 38.213 f60 is also adaptive. The amount of multiple PRACH opportunities depends on the amount of PRACH opportunities in each SSB group, the amount of SSB groups, and the number of PRACH repetitions.

[0037] Typically, mapping the indexes of multiple SSBs to multiple PRACH opportunities is performed in the following order:

[0038] First, in increasing order of SSB index within the SSB group;

[0039] · Next, in increasing order of PRACH repetition index; and

[0040] Next, in increasing order of SSB group index.

[0041] In addition, regarding how to index the PRACH resources in the time domain, frequency domain, and code domain, the overall mapping logic in TS 38.331 f60 is also adaptive, that is,

[0042] First, in increasing order of preamble index within a single PRACH opportunity

[0043] Secondly, in the increasing order of frequency resource index for PRACH opportunities used for frequency multiplexing

[0044] Third, in increasing order of time resource index of PRACH opportunities used for time multiplexing within a PRACH slot

[0045] Fourth, in increasing order of index within the PRACH time slot

[0046] In order to obtain a complete mapping pattern between multiple SSBs and multiple PRACH opportunities, more mapping parameters are required in addition to the above. More specific embodiments of the mapping between SSBs and PRACH opportunities will be described below.

[0047] According to some embodiments of the present application, the SSB group size (i.e., "SSB-group-size") used to divide multiple SSBs into one or more SSB groups means how many SSBs can be included in the SSB group at most, which can also be configured or predefined. The number of PRACH repetitions (i.e., "PRACH-repetition-times") means how many times the PRACH transmission for the same PRACH preamble is repeated, which can also be configured or predefined. In addition, in addition to the overall mapping logic in TS 38.331 f60, the two traditional RRC parameters defined in TS 38.331 f60 (i.e., "msg1-FDM" and "ssb-perRACH-OccasionAndCB-PreamblesPerSSB") are also adaptive. Specifically, "msg1-FDM" describes the number of PRACH opportunities of frequency division multiplexing (FDM) in one moment, that is, "msg1-FDM" specifies how many ROs are allocated in the frequency domain (at the same position in the time domain); "ssb-perRACH-Occasion" describes the number of SSBs per PRACH opportunity (time and frequency), and "CB-PreamblesPerSSB" describes the number of contention-based PRACH preambles per SSB.

[0048] Based on the above mapping parameters, the mapping pattern between multiple SSBs and multiple PRACH opportunities can be determined. Specifically, the amount of SSB groups (i.e., "SSB-group-amount") can be calculated as: SSB-group-amount = ceil (SSB-total / SSB-group-size). The amount of time-domain PRACH opportunities for each SSB group (i.e., "time-RO-perSSBgroup") can be determined as follows: time-RO-perSSBgroup = ceil (SSB-group-size / (msg1-FDM*ssb-perRACH-Occasion)). The amount of PRACH opportunities for each SSB group (i.e., "RO-perSSBgroup") can be calculated as: RO-perSSBgroup = ceil (SSB-group-size / ssb-perRACH-Occasion). The amount of multiple PRACH opportunities for mapping all multiple SSBs (i.e., RO-total) is calculated as: RO-total = RO-perSSBgroup*PRACH-repetition-times*SSB-group-amount. The amount of time-domain PRACH opportunities among the multiple PRACH opportunities for mapping all multiple SSBs (i.e., time-RO-total) is calculated as: time-RO-total = time-RO-perSSBgroup*PRACH-repetition-times*SSB-group-amount.

[0049] Therefore, based on the determined mapping mode, for example, SSB-total is ST, and SSB-group-size is k, that is, there are st / k SSB groups, such as G0 to G(st / k-1). "RO-perSSBgroup" is h, that is, there are at most h PRACH opportunities per SSB group, and PRACH-repetition-times is x. Then, based on the above mapping order, that is, first, in the increasing order of SSB index within the SSB group; then, in the increasing order of PRACH repetition index; and then, in the increasing order of SSB group index; mapping will start from the first SSB group in the mapping cycle. Specifically, the mapping between SSBs and PRACH opportunities for a number of PRACH repetitions x will start from G0 at a configured or predefined position in the time domain (e.g., frame 0). The mapping within G0 will be associated with SSBs 0 to k-1, and will be repeated x times from PRACH opportunity 0 to PRACH opportunity (h*x-1). The mapping for G1 will start from PRACH opportunity h*x, will be associated with SSB k to 2k-1, and will be repeated x times from PRACH opportunity h*x to PRACH opportunity (h*2x-1). Then, the mapping for G3 to G(st / k-1) will be performed in the same way until all ST SSBs are mapped.

[0050] Figure 5 An exemplary mapping between SSB and PRACH opportunities according to some embodiments of the present application is described.

[0051] exist Figure 5In the exemplary embodiment shown in , the SSB group size (i.e., "SSB-group-size") is 4. The amount of multiple SSBs to be mapped (i.e., "SSB-Total") is 16. "msg1-FDM" is 2 and "SSBPerRACHOccasion" is 2. The number of PRACH repetitions (i.e., "PRACH-repetition-times") is 4, each of which corresponds to R1, R2, R3, and R4. Then, the amount of SSB groups "SSB-group-amount" is: SSB-group-amount = ceil (SSB-total / SSB-group-size) = ceil (16 / 4) = 4. That is, there are 4 SSB groups, for example, G0, G1, G2, and G3. The amount of time-domain PRACH opportunities per SSB group (i.e., "time-RO-per-SSBgroup") is determined by: time-RO-per-SSBgroup = ceil(SSB-group-size / (msg1-FDM*ssb-perRACH-Occasion)) = ceil(4 / (2*2)) = 1. That is, for each repetition of one SSB group, there is one time-domain PRACH opportunity. For example, for the first repetition with respect to G0, i.e., R1 with respect to G0, there is a time-domain PRACH opportunity associated with RO 0; for the second repetition with respect to G1, i.e., R2 with respect to G1, there is a time-domain PRACH opportunity associated with RO 10; for the third repetition with respect to G2, i.e., R3 with respect to G2, there is a time-domain PRACH opportunity associated with RO 20; and for the fourth repetition with respect to G3, i.e., R4 with respect to G3, there is a time-domain PRACH opportunity associated with RO 30. The amount of PRACH opportunities per SSB group (ie, "RO-per-SSBgroup") is calculated as: RO-per-SSBgroup = ceil(SSB-group-size / ssb-perRACH-Occasion) = ceil(4 / 2) = 2. That is, for each repetition of an SSB group, there are 2 PRACH opportunities.For example, for the first repetition regarding G0, there are RO 0 and RO 1 (also called "TRO 0", i.e., the first RO set in the time domain and frequency domain) in the time domain and frequency domain (without considering the code domain); for the second repetition regarding G1, there are RO 10 and RO 11 (also called "TRO 5", i.e., the sixth RO set in the time domain and frequency domain) in the time domain and frequency domain (without considering the code domain); for the third repetition regarding G2, there are RO20 and RO 21 (also called "TRO 10", i.e., the eleventh RO set in the time domain and frequency domain) in the time domain and frequency domain (without considering the code domain); and for the fourth repetition regarding G3, there are RO 30 and RO 31 (also called "TRO 15", i.e., the sixteenth RO set in the time domain and frequency domain) in the time domain and frequency domain (without considering the code domain). The amount of multiple PRACH opportunities for all multiple SSBs is calculated as: RO-total-amount = RO-per-SSBgroup*PRACH-repetition-times*SSB-group-amount = 2*4*4 = 32. That is, for 4 PRACH repetitions, there are a total of 32 PRACH opportunities for mapping of 16 SSBs, i.e., RO 0 to RO 31. The amount of multiple time-domain PRACH opportunities for all multiple SSBs is calculated as: time-RO-total-amount = time-RO-per-SSBgroup*PRACH-repetition-times*SSB-group-amount = 1*4*4 = 16. That is, for 4 PRACH repetitions, there are a total of 16 time-domain PRACH opportunities for mapping of 16 SSBs, i.e., TRO 0, TRO 1, TRO 2, ..., TRO 15.

[0052] According to some embodiments of the present application, since the mapping between SSB and PRACH opportunities depends on several ceil (round up) operations, for example, to obtain the amount of SSB groups, etc., the calculated amount of PRACH opportunities may be more than what is required for mapping. That is, for several PRACH repetitions, there may be one or more PRACH opportunities without any mapped SSBs in the last SSB group. In this regard, a solution according to some embodiments of the present application is to perform mapping based on the actual amount of SSBs in the last SSB group until all SSBs are mapped and the subsequent PRACH opportunities are not used for this SSB group. Unused PRACH opportunities can be further used for the next cycle by mapping. That is, in this solution, the amount of SSBs in each PRACH repetition in the last SSB group is different from the configured or predefined SSB group size. Another solution according to some embodiments of the present application is to perform mapping based on the configured or predefined SSB group size, and the PRACH opportunity in each PRACH repetition without a corresponding SSB in the last SSB group is not used. In this case, the unused PRACH opportunities cannot be reused by other mapping cycles.

[0053] Fig. 6A and Figure 6B The exemplary mapping between SSB and PRACH opportunities according to some embodiments of the present application is described respectively. Fig. 6A and Figure 6B The difference between them lies in the mapping of the last SSB group due to redundant PRACH opportunities.

[0054] exist Fig. 6A and 6BIn the exemplary embodiment shown in , the SSB group size (i.e., "SSB-group-size") is 8. The amount of multiple SSBs to be mapped (i.e., "SSB-Total") is 18. "msg1-FDM" is 2 and "SSBPerRACHOccasion" is 2. The number of PRACH repetitions (i.e., "PRACH-repetition-times") is 4, each of which corresponds to R1, R2, R3, and R4. Then, the amount of SSB groups "SSB-group-amount" is: SSB-group-amount = ceil (SSB-total / SSB-group-size) = ceil (18 / 8) = 3. That is, there are 3 SSB groups, for example, G0, G1, and G2. The amount of time-domain PRACH opportunities per SSB group (i.e., "time-RO-per-SSBgroup") is determined by: time-RO-per-SSBgroup = ceil(SSB-group-size / (msg1-FDM*ssb-perRACH-Occasion)) = ceil(8 / (2*2)) = 2. That is, for each repetition of an SSB group, there are two time-domain PRACH opportunities. For example, in Fig. 6A and 6B In both cases, for the first repetition about G0, that is, R1 about G0, there are time domain PRACH opportunities associated with RO 0 and RO 2; for the second repetition about G1, that is, R2 about G1, there are time domain PRACH opportunities associated with RO 20 and RO 22. For the third repetition about G2, that is, R3 about G2, in Fig. 6A There is a time domain PRACH opportunity associated with RO 36 in Figure 6B There are time domain PRACH opportunities associated with RO 40 and RO 42 in . The amount of PRACH opportunities per SSB group (i.e., "RO-per-SSBgroup") is calculated as: RO-per-SSBgroup = ceil(SSB-group-size / ssb-perRACH-Occasion) = ceil(8 / 2) = 4. That is, for each repetition within an SSB group, there are 4 PRACH opportunities. For example, in Fig. 6A and 6BIn both, for the first repetition about G0, there are RO 0, RO 1, RO2, and RO 3 (i.e., TRO 0 and TRO 1) in the time domain and frequency domain (not considering the code domain). For the second repetition about G1, there are RO 20, RO 21, RO 22, and RO 23 (i.e., TRO 10 and TRO 11) in the time domain and frequency domain (not considering the code domain); and for the third repetition about G2, there are RO 20, RO 21, RO 22, and RO 23 (i.e., TRO 10 and TRO 11) in the time domain and frequency domain (not considering the code domain); Fig. 6A In the time domain and frequency domain (not considering the code domain), there are RO 36 and RO 37 (not used) (TRO 18), and in Figure 6B In the time domain and frequency domain (code domain is not considered), there are RO 40, RO 41 (unused), RO 42 and RO 43 (unused) (TRO 20 and TRO 21). The amount of multiple PRACH opportunities for all multiple SSBs is calculated as: RO-total-amount = RO-per-SSBgroup*PRACH-repetition-times*SSB-group-amount = 4*4*3 = 48. That is, for 4 PRACH repetitions, there are a total of 48 PRACH opportunities for mapping 18 SSBs, that is, RO 0 to RO 47. The amount of multiple time-domain PRACH opportunities for all multiple SSBs is calculated as: time-RO-total-amount = time-RO-per-SSBgroup*PRACH-repetition-times*SSB-group-amount = 2*4*3 = 24. That is, for 4 PRACH repetitions, in Figure 6B There are a total of 24 time domain PRACH opportunities for mapping 18 SSBs in , i.e., TRO 0, TRO 1, ..., TRO 23, each TRO includes two ROs in the time domain and frequency domain, where msg1-FDM is configured as 2. However, due to the last SSB group, i.e., G3, which uses only one time domain PRACH opportunity, for four PRACH repetitions, Fig. 6A There are a total of 20 time-domain PRACH opportunities for mapping of 18 SSBs, i.e., TRO 0, TRO 1, ..., TRO 19, each TRO for G0 to G1 includes two ROs in both the time domain and the frequency domain, and each TRO for G3 includes one used RO in both the time domain and the frequency domain (the other RO is not used).

[0055] However, if Fig. 6A and 6B As shown in FIG, since only 18 SSBs are used for mapping, the 48 PRACH opportunities counted are more than required by the mapping. Fig. 6A, the mapping for the 4 PRACH repetitions is performed in the last SSB group based on the actual amount of SSBs in the same way as the other SSB groups until all SSBs are mapped, and the following PRACH opportunities are not used. That is, in each PRACH repetition, only the ROs in the time domain corresponding to SSB 16 and SSB 17, i.e., RO 32, RO 34, RO 36, and RO 38, can be used, and RO 33, RO 35, RO 37, RO 39, and RO 40 to 47 are not used. Figure 6B In the example, mapping for 4 PRACH repetitions is performed based on the configured or predefined SSB group size (i.e., 8 SSBs), and the PRACH opportunities in each PRACH repetition without a corresponding SSB in the last SSB group are not used. That is, in each PRACH repetition, two ROs in the time domain are supported except for the ROs for SSB 16 and SSB 17, and only one RO is used for mapping, e.g., the first RO in the time domain for each PRACH repetition. Figure 6B As shown in FIG. , RO 32, RO 36, RO 40 and RO 44 can be used, while RO 33 to 35, 37 to 39, 41 to 43 and 45 to 47 are not used.

[0056] Figure 7 An exemplary method for performing PRACH repetition according to some embodiments of the present application is described. The exemplary method may be performed in a UE. A UE may also be referred to as a subscriber unit, a mobile device, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, or a device, or described using other terms used in the art.

[0057] Figure 8 Another exemplary method for performing PRACH repetition according to some other embodiments of the present application is described. Another exemplary method may be performed in a BS. The BS may be referred to as an access point, an access terminal, a base station, a basic unit, a macro cell, a node-B, an evolved node B (eNB), a gNB, a home node-B, a relay node, or a device, or described using other terms used in the art. According to some embodiments of the present application, Figure 7 The method presented in this paper can be used at the system level with Figure 8 They may also cooperate with the methods shown in the text; at the same time, they may also cooperate with other methods according to some other embodiments of the present application.

[0058] The SSB group size for mapping between multiple SSBs and multiple PRACH opportunities with several PRACH repetitions may be configured or predefined. Figure 7 and 8, the SSB group size may be configured by a network side such as a BS and indicated to a remote side such as a UE. For example, in step 802, signaling information indicating the SSB group size may be transmitted to the UE, such as by the BS. In step 702, signaling information indicating the SSB group size may be received from the BS, such as by the UE.

[0059] In some embodiments of the present application, the signaling information may indicate the SSB group size in an explicit manner, for example, indicating the value of the SSB group size. The value of the SSB group size is equal to or less than the total number of multiple SSBs. In some other embodiments of the present application, the signaling information may indicate the SSB group size in an implicit manner, for example, indicating the amount of time domain PRACH opportunities for each SSB group, or indicating the amount of time domain and frequency domain PRACH opportunities for each SSB group. In some other embodiments of the present application, the signaling information may also indicate the SSB group size implicitly by indicating the amount of SSBs associated with one time domain PRACH opportunity among multiple PRACH opportunities for mapping, or by indicating the amount of SSBs associated with one time domain and frequency domain PRACH opportunity among multiple PRACH opportunities for mapping. The SSB group size may be calculated based on the associated signaling information.

[0060] For example, in the case where the amount of time-domain PRACH opportunities associated with an SSB group, for example, time-RO-per-SSBgroup is indicated, the SSB group size may be calculated as: SSB-group-size = msg1-FDM*ssb-perRACH-Occasion*time-RO-per-SSBgroup. In some embodiments of the present application, the signaling information may only indicate the amount of SSBs associated with one time-domain PRACH opportunity. Since msg1-FDM*ssb-perRACH-Occasion is the amount of SSBs associated with one time-domain PRACH opportunity, this approach actually indicates that all SSBs within one SSB group are associated with the same time-domain PRACH opportunity. That is, time-RO-per-SSBgroup is implicitly indicated as 1. SSB-group-size is actually implicitly indicated as the same as the amount of SSBs associated with one time-domain PRACH opportunity.

[0061] In addition to the above-mentioned signaling information, the BS may also configure other mapping parameters, such as the amount of multiple SSBs used for PRACH repetition, "msg1-FDM" and "ssb-perRACH-OccasionAndCB-PreamblesPerSSB". According to some embodiments of the present application, the BS may also indicate the configured number of PRACH repetitions to the UE. The configured number of PRACH repetitions is at least one of a cell-specific configured number (i.e., the number of times configured for a cell (shared by all UEs or a group of UEs in a specific cell)) and a UE-specific configured number (i.e., the number of times configured for a specific UE). The configured number of PRACH repetitions may be the same as or different from the actual number of PRACH repetitions, which may be determined by the UE itself. The cell-specific configured number may be the same as or different from the UE-specific configured number. That is, even if multiple UEs are in the same cell, they may have different actual numbers of repetitions.

[0062] According to some embodiments of the present application, the configured PRACH repetition number can be indicated to the UE through at least one of the frequency domain resources and the code domain resources. For example, different frequency domain PRACH opportunities are associated with different repetition numbers, and the frequency domain resources can be associated with frequency domain PRACH opportunity indexes of different repetition numbers. Different PRACH preambles are associated with different repetition numbers, and the code domain resources can be associated with the PRACH preamble index. In some embodiments of the present application, the indicated at least one of the frequency domain resources and the code domain resources can also adapt to the scenario in which the UE determines the PRACH repetition number by itself. In this case, the PRACH repetition number means the actual PRACH repetition number, and the PRACH repetition number means the actual PRACH repetition number.

[0063] Based on the SSB group size, the UE and the BS may divide the plurality of SSBs into one or more SSB groups, and perform mapping for a number of PRACH repetitions with other mapping parameters based on the SSB groups. In step 704, the UE may map the indexes of the plurality of SSBs to the plurality of PRACH opportunities based on the divided SSB groups. Similarly, in step 804, the BS may map the indexes of the plurality of SSBs to the plurality of PRACH opportunities based on the divided SSB groups. The specific mapping process has been described above, and therefore will not be described in detail here.

[0064] Based on the mapping between the SSB and the PRACH opportunity, in step 706, the UE may determine a set of PRACH opportunities for a number of PRACH repetitions from the plurality of PRACH opportunities based on the mapping at step 704, and the PRACH repetition number corresponds to one of the indexes of the plurality of SSBs. The UE may transmit the same PRACH preamble corresponding to the SSB on a set of determined PRACH opportunities to the network side. That is, the same PRACH preamble may be repeatedly transmitted to the network side. In step 806, the BS may respond to the received PRACH preambles transmitted on a number of PRACH opportunities corresponding to one of the indexes of the plurality of SSBs based on the mapping at step 704.

[0065] According to the above-mentioned embodiment of the present application, all SSB groups are repeated continuously, that is, each SSB group for several PRACH repetitions is continuously distributed in the time domain. In other words, several PRACH repetitions for the same SSB group are continuous. However, since the mapping between SSB and PRACH opportunities according to the embodiment of the present application is novel than the conventional technology, the conventional UE using the conventional technology and the new UE using the novel technology have different understandings for performing mapping with the same mapping parameters, except for the first PRACH repetition (e.g., R1) for the first SSB group (e.g., G0). "The first PRACH repetition for the first SSB group" means the first PRACH transmission for the first SSB group in one or more SSB groups for several PRACH repetitions. For example, both the conventional UE and the new UE transmit the PRACH preamble at the same time, and the BS such as the gNB can receive the PRACH preamble only based on the conventional mapping between the SSB and the PRACH opportunity, or based on the new mapping between the SSB and the PRACH opportunity. That is, in any way, one PRACH preamble from a legacy UE or from a new UE will be lost. Therefore, the UE that lost the PRACH preamble cannot access the network and the BS cannot recognize the SSB or beam associated with the lost PRACH preamble. Therefore, coexistence with NR legacy technology should be seriously considered.

[0066] According to some embodiments of the present application, a mechanism of PRACH repetition start position cycling is introduced to ensure that both legacy UEs and new UEs have the same understanding of all SSBs. Therefore, the impact of misunderstanding between legacy and new mapping techniques can be balanced for legacy UEs and new UEs.

[0067] Under the mechanism of PRACH repetition start position cycle, each mapping cycle starts with the first repetition of the first SSB group in one or more SSB groups for PRACH repetition, and the first continuously distributed SSB groups mapped for several PRACH repetitions within each mapping cycle are different. That is, within the mapping cycle, the index of the first continuously distributed SSB group mapped for several PRACH repetitions is different. For example, the index of the first continuously distributed SSB group within a non-initial mapping cycle may increase in the order of the SSB group index of the previous mapping cycle with respect to the non-initial mapping cycle. If the index of the first continuously distributed SSB group for the mapping cycle is the last SSB group index, then the index of the first continuously distributed SSB group for the next mapping cycle is the first SSB group index when the offset is 1, and the second SSB group index when the offset is 2, etc. The complete PRACH repetition start position cycle period is defined so that all SSB groups for several PRACH repetitions are used as the first continuously distributed SSB groups within the corresponding mapping cycle. The index of the first continuously distributed SSB group for the mapping cycle can be configured or predefined. The SSB group index of the first continuous distribution may increase the relative offset relative to the index of the previous mapping cycle. The relative offset relative to the index of the previous mapping cycle of the non-initial mapping cycle may be the amount of time domain PRACH opportunities per SSB group. In some embodiments of the present application, the relative offset relative to the index of the previous mapping cycle of the non-initial mapping cycle is the index step size of one or more SSB groups.

[0068] Assuming that the index of the previous mapping cycle is i_p, the offset is i_o, and the total number of SSB groups, i.e., "SSB-group-amount" is N, then the index of the current mapping cycle can be determined by the function mod((i_p+i_o), N). The starting position in the time domain of the first mapping cycle (or initial mapping cycle) can be configured or predefined. The starting position in the time domain of the first continuously distributed SSB group mapped in a non-initial mapping cycle can increase the relative offset relative to the starting position of the previous mapping cycle of the non-initial mapping cycle. According to some embodiments of the present application, the offset relative to the starting position of the previous mapping cycle of the non-initial mapping cycle is the amount of time domain PRACH opportunities within the SSB group, i.e., "time-RO-perSSBgroup" or a multiple of "time-RO-perSSBgroup". Since the two relative starting positions in the time domain are compared relative to the start of the mapping cycle, the offset is relative. For the remaining SSB groups corresponding to the remaining repetitions in non-contiguous PRACH repetitions that need to be mapped, they will be moved in the time domain to the end of the PRACH opportunity in the order of SSB group index within each mapping cycle.

[0069] FIG. 9A illustrates an exemplary mapping between SSB and PRACH opportunities under the mechanism of PRACH repetition start position cycling according to some embodiments of the present application, which further includes FIG. 9A-1 corresponding to the first mapping cycle, FIG. 9A-2 corresponding to the second mapping cycle, and FIG. 9A-3 corresponding to the third mapping cycle. Without considering the cyclic PRACH repetition start position, the mapping parameters and mapping principle in FIG. 9A are the same as those in FIG. Fig. 6A The mapping parameters and mapping principles are the same. There are 3 SSB groups, namely, G0, G1 and G3, and each SSB group is used for 4 PRACH repetitions, namely, R1, R2, R3 and R4.

[0070] In the embodiment shown in FIG. 9A-1, in the first mapping cycle, the first continuously distributed AAB group (which is G0) mapped for a number of consecutive PRACH repetitions and thus the start position in the time domain of the first continuously distributed SSB group in the first mapping cycle is the same as the start position of the first mapping cycle, which may be configured or defined as frame 0 or other position in the time domain. Therefore, in the first mapping cycle, the mapping pattern shown in FIG. 9A is the same as Fig. 6A The mapping patterns shown in are basically the same.

[0071] For the second mapping cycle shown in FIG. 9A-2 , the index of the first continuously distributed SSB group mapped for several consecutive PRACH repetitions increases in the order of the SSB group index, i.e., the second SSB group G1. The starting position in the time domain of the second mapping cycle corresponds to RO 40. The starting position in the time domain of the first continuously distributed SSB group (i.e., G1) within the second mapping cycle may be offset relative to the starting position of the first continuously distributed SSB group in the first mapping cycle. The offset is the amount of the time domain PRACH opportunity for one SSB group, i.e., 2 time domain PRACH opportunities. Therefore, the starting position in the time domain of G1 may be offset by two time domain PRACH opportunities in the time domain relative to the starting position of G0 (i.e., RO 40). That is, the starting position in the time domain of G1 corresponds to RO 44. For the remaining non-continuous PRACH repetitions corresponding to a specific SSB group, i.e., the second to fourth repetitions regarding the first SSB group, they will be moved in the time domain to the end of the PRACH opportunity sequence, i.e., after the PRACH opportunity, i.e., RO 66 is used for the last repetition regarding the third SSB group G2 (R4 regarding G2).

[0072] For the third mapping cycle shown in FIG. 9A-3 , the index of the first continuously distributed SSB group mapped for several PRACH repetitions increases in the order of the SSB group index, i.e., the third SSB group G2. The starting position in the time domain of the third mapping cycle corresponds to RO 80. The starting position in the time domain of G2 within the third mapping cycle may be offset relative to the starting position of the second SSB group G1. The offset is the amount of the time domain PRACH opportunity within one SSB group, i.e., 2 time domain PRACH opportunities. Therefore, the starting position in the time domain of G2 within the third mapping cycle may be offset by two time domain PRACH opportunities relative to the starting position of G1, i.e., RO 84. That is, the starting position in the time domain of G2 corresponds to RO 88. For the remaining non-continuous PRACH repetitions corresponding to a specific SSB group, i.e., the second to fourth repetitions with respect to the first and second SSB groups, they will be moved to the end of the PRACH opportunity sequence in the time domain in the order of the SSB group index. Specifically, the second to fourth repetitions regarding the first SSB group (i.e., R2 regarding G0, R3 regarding G0, and R4 regarding G0) are after RO 94 in the time domain of the last repetition regarding the third SSB group G2; and the second to fourth repetitions regarding the second SSB group (i.e., R2 regarding G1, R3 regarding G1, and R4 regarding G1) are after RO106 in the time domain of the last repetition regarding the first SSB group G0.

[0073] FIG. 9B illustrates an exemplary mapping between SSB and PRACH opportunities under the mechanism of PRACH repetition start position cycling according to some other embodiments of the present application, which further includes FIG. 9B-1 corresponding to the first mapping cycle, FIG. 9B-2 corresponding to the second mapping cycle, and FIG. 9B-3 corresponding to the third mapping cycle. Similar to FIG. 9A, without considering the cyclic PRACH repetition start position, the mapping parameters and mapping principle in FIG. 9B are the same as those in FIG. Fig. 6A The mapping parameters and mapping principles are the same, but FIG. 9A and FIG. 9B have different first continuously distributed SSB groups.

[0074] In the embodiment shown in FIG. 9B-1, the first continuously distributed SSB group is configured or defined as the second SSB group G1 in the first mapping cycle, and the first SSB group G0 is not used for continuous repetition. The starting position in the time domain of the first mapping cycle may be configured or predefined as frame 0 or other position in the time domain. The starting position in the time domain of the first continuously distributed SSB group (i.e., G1) may be frame 0 plus 2 time domain PRACH opportunities based on the starting position in the time domain of the first mapping cycle. The first repetition with respect to the first SSB group G0 (i.e., R1 with respect to G0) occupies the time domain PRACH opportunities RO 0 / 1 and RO 2 / 3; and the remaining repetitions with respect to the first SSB group G0 (i.e., the second to fourth repetitions with respect to the first SSB group G0) are moved to the end of the PRACH opportunity sequence in the time domain, i.e., after RO 26 in the time domain of the last repetition with respect to the third SSB group G2. The mapping pattern in FIG. 9B-1 is substantially the same as the mapping pattern shown in FIG. 9A-2.

[0075] For the second mapping cycle shown in FIG. 9B-2 , the index of the first continuously distributed SSB group mapped for several PRACH repetitions increases in the order of the SSB group index, i.e., the third SSB group G2. The starting position in the time domain of the second mapping cycle is RO 40. The starting position in the time domain of G2 within the second mapping cycle may be offset relative to the starting position of the second SSB group G1. The offset is the amount of the time domain PRACH opportunity for one repetition of one SSB group, i.e., 2 time domain PRACH opportunities. Therefore, the starting position in the time domain of G2 within the second mapping cycle may be offset by two time domain PRACH opportunities relative to the starting position of G1 (i.e., RO 44). That is, the starting position in the time domain of G2 corresponds to RO 48. For the remaining non-continuous PRACH repetitions corresponding to specific SSB groups, respectively, i.e., the second to fourth repetitions with respect to the first and second SSB groups, they will be moved to the end of the PRACH opportunity sequence in the time domain. Specifically, the second to fourth repetitions regarding the first SSB group (i.e., R2 regarding G0, R3 regarding G0, and R4 regarding G0) are after RO 54 in the time domain of the last repetition regarding the third SSB group G2; and the second to fourth repetitions regarding the second SSB group (i.e., R2 regarding G1, R3 regarding G1, and R4 regarding G1) are after RO 66 in the time domain of the last repetition regarding the first SSB group G0.

[0076] For the third mapping cycle shown in FIG. 9B-3, the index of the first SSB group mapped for several PRACH repetitions increases in the order of the SSB group index in the PRACH repetition start position cycle, i.e., back to the first SSB group G0. Therefore, the mapping pattern will be the same as Fig. 6A The mapping mode is basically the same as that shown in Figure 9A-1.

[0077] Fig.10 A block diagram illustrating an exemplary apparatus according to some embodiments of the present application.

[0078] like Fig.10 , the apparatus 1000 may include a receiving circuit system 1001, a transmitting circuit system 1003, a processor 1005, and a non-transitory computer-readable medium 1007. The non-transitory computer-readable medium 1007 has stored therein computer-executable instructions that cause the processor to implement the method according to an embodiment of the present application. The processor 1005 is configured to be coupled to the non-transitory computer-readable medium 1007, the receiving circuit system 1001, and the transmitting circuit system 1003. It is considered that in some other embodiments of the present application, according to actual requirements, the apparatus 1000 may include more computer-readable media, receiving circuit systems, transmitting circuit systems, and processors. In some embodiments of the present application, the receiving circuit system 1001 and the transmitting circuit system 1003 are integrated into a single device, such as a transceiver. In a specific embodiment, the apparatus 1000 may further include an input device, a memory, and / or other components.

[0079] In some embodiments of the present application, the non-transitory computer-readable medium 1007 may store computer-executable instructions thereon, and the computer-executable instructions are used to cause the processor to implement the operations described above with respect to (several) UEs, such as Figure 7 The method shown in the embodiment includes: receiving signaling information for indicating an SSB group size; mapping the indexes of multiple SSBs to multiple PRACH opportunities for performing several PRACH repetitions, wherein the multiple SSBs are divided into one or more SSB groups based on the indicated SSB group size; and determining a set of PRACH opportunities corresponding to one of the indices of the multiple SSBs from the multiple PRACH opportunities based on the mapping.

[0080] In some other embodiments of the present application, the non-transitory computer-readable medium 1007 may store thereon computer-executable instructions for causing the processor to implement the operations performed in (several) BSs as described above, such as Figure 8 The method shown in the embodiment includes: transmitting signaling information for indicating the size of an SSD group; mapping the indexes of multiple SSBs to multiple PRACH opportunities for performing multiple PRACH repetitions, wherein the multiple SSBs are divided into one or more SSB groups based on the SSB group size; and responding to PRACH preamble codes transmitted on multiple PRACH opportunities corresponding to one of the indices of the multiple SSBs based on the mapping.

[0081] The method of the present application can be implemented on a programmed processor. However, the controller, flow chart and module can also be implemented on a general or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit components, an integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device or the like. In general, any device on which a finite state machine capable of implementing the flow chart shown in the figure resides can be used to implement the processor functions of the present application.

[0082] It will be appreciated by those of ordinary skill in the art that the steps of the methods described in conjunction with the aspects disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the steps of the methods may reside as one or any combination or set of codes and / or instructions on a non-transitory computer-readable medium, which may be incorporated into a computer program product.

[0083] Although the present disclosure has been described with specific embodiments of the present disclosure, it is apparent that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or replaced in other embodiments. In addition, all elements of each figure are not necessary for the operation of the disclosed embodiments. For example, a person skilled in the art of the disclosed embodiments will be able to make and use the teachings of the present disclosure by simply adopting the elements of the independent claims. Therefore, the embodiments of the present disclosure as set forth herein are intended to be illustrative, rather than restrictive. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0084] In this document, the term "includes", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment comprising a series of elements not only comprises the elements, but also may comprise other elements that are not clearly listed or inherent to the process, method, article or equipment. The element beginning with "one", "one" or the like does not exclude the existence of additional identical elements in the process, method, article or equipment comprising the elements without more restrictions. In addition, the term "another" is defined as at least the second or more. The terms "include", "have" and the like as used herein are defined as "include".

Claims

1. A method comprising: receiving signaling information indicating a synchronization signal block (SSB) group size; mapping indices of a plurality of SSBs to a plurality of physical random access channel (PRACH) opportunities for a number of PRACH repetitions, wherein the plurality of SSBs are divided into one or more SSB groups based on the indicated SSB group size and mapping the indices of the plurality of SSBs to the plurality of PRACH opportunities in the following manner: first, in increasing order of SSB indices within an SSB group, second, in increasing order of PRACH repetition indices, and third, in increasing order of SSB group indices; and Based on the mapping, a set of PRACH opportunities corresponding to one of the indices of the plurality of SSBs is determined from the plurality of PRACH opportunities.

2. The method of claim 1, wherein the plurality of PRACH opportunities are valid PRACH opportunities.

3. The method according to claim 1, wherein the signaling information indicates the SSB group size with a value.

4. The method of claim 1, wherein the signaling information implicitly indicates the SSB group size by indicating an amount of time-domain PRACH opportunities used for each SSB group.

5. The method of claim 1, wherein the signaling information implicitly indicates the SSB group size by indicating an amount of time domain and frequency domain PRACH opportunities used for each SSB group.

6. The method of claim 1, wherein the signaling information implicitly indicates the SSB group size by indicating an amount of SSBs associated with one time-domain PRACH opportunity among the plurality of PRACH opportunities.

7. The method of claim 1, wherein the signaling information implicitly indicates the SSB group size by indicating an amount of SSBs associated with one time-domain and frequency-domain PRACH opportunity among the plurality of PRACH opportunities.

8. The method of claim 1, wherein the mapping is performed periodically and each mapping cycle is associated with the number of PRACH repetitions.

9. The method according to claim 8, wherein each mapping cycle starts from a configured or predefined time domain position, and the duration of each mapping cycle is a minimum value that enables all of the indices of the multiple SSBs to be mapped to the multiple PRACH opportunities for the number of PRACH repetitions.

10. The method of claim 8, wherein an index of a first mapped SSB group among the one or more SSB groups within a first mapping cycle is predefined or configured.

11. The method of claim 10, wherein an index of a first mapped SSB group in the one or more SSB groups within each mapping cycle is the same.

12. The method of claim 10, wherein an index of a first consecutive mapped SSB group of the one or more SSB groups within a non-initial mapping cycle is increased by a relative offset relative to an index of a previous mapping cycle of the non-initial mapping cycle.

13. The method of claim 12, wherein the relative offset relative to the index of a previous mapping cycle of the non-initial mapping cycle is an amount of time-domain PRACH opportunities per SSB group.

14. The method of claim 12, wherein the relative offset with respect to an index of a previous mapping cycle of the non-initial mapping cycle is an index step size of the one or more SSB groups.

15. The method of claim 1, comprising receiving a configured number of PRACH repetitions.

16. The method of claim 15, wherein the configured PRACH repetition number is at least one of a cell-specific configured number and a UE-specific configured number.

17. The method of claim 15, wherein the configured PRACH repetition number is the same as a repetition number of the number of PRACH repetitions.

18. The method of claim 15, wherein the configured PRACH repetition number is different from a repetition number of the number of PRACH repetitions.

19. The method of claim 16, wherein the UE-specific configured number of times is indicated by at least one of frequency domain resources and code domain resources.

20. The method of claim 19, wherein the frequency domain resource is associated with a frequency domain PRACH opportunity index.

21. The method of claim 19, wherein the code domain resource is associated with a PRACH preamble index.

22. A method comprising: Transmitting signaling information for indicating a synchronization signal block (SSB) group size; Mapping indices of a plurality of SSBs to a plurality of physical random access channel (PRACH) opportunities for a number of PRACH repetitions, wherein the plurality of SSBs are divided into one or more SSB groups based on the SSB group size and mapping the indices of the plurality of SSBs to the plurality of PRACH opportunities in the following manner: first, in increasing order of SSB indices within an SSB group, second, in increasing order of PRACH repetition indices, and third, in increasing order of SSB group indices; and Based on the mapping, respond to a PRACH preamble code transmitted on a number of PRACH opportunities corresponding to one of the indices of the plurality of SSBs.

23. The method of claim 22, wherein the plurality of PRACH opportunities are valid PRACH opportunities.

24. The method of claim 22, wherein the signaling information indicates the SSB group size with a value.

25. The method of claim 22, wherein the signaling information implicitly indicates the SSB group size by indicating an amount of time-domain PRACH opportunities used for each SSB group.

26. The method of claim 22, wherein the signaling information implicitly indicates the SSB group size by indicating an amount of time domain and frequency domain PRACH opportunities used for each SSB group.

27. The method of claim 22, wherein the signaling information implicitly indicates the SSB group size by indicating an amount of SSBs associated with one time-domain PRACH opportunity among the plurality of PRACH opportunities.

28. The method of claim 22, wherein the signaling information implicitly indicates the SSB group size by indicating an amount of SSBs associated with one time-domain and frequency-domain PRACH opportunity among the plurality of PRACH opportunities.

29. The method of claim 22, wherein the mapping is performed periodically and each mapping cycle is associated with the number of PRACH repetitions.

30. The method of claim 29, wherein each mapping cycle starts from a configured or predefined time domain position, and the duration of each mapping cycle is a minimum value that enables all of the indices of the plurality of SSBs to be mapped to the plurality of PRACH opportunities for the plurality of PRACH repetitions.

31. The method of claim 29, wherein an index of a first mapped SSB group among the one or more SSB groups within a first mapping cycle is predefined or configured.

32. The method of claim 31, wherein an index of a first mapped SSB group in the one or more SSB groups within each mapping cycle is the same.

33. The method of claim 31, wherein the index of a first consecutive distribution of the one or more SSB groups within a non-initial mapping cycle is increased by a relative offset relative to the index of a previous mapping cycle of the non-initial mapping cycle.

34. The method of claim 33, wherein the relative offset relative to the index of a previous mapping cycle of the non-initial mapping cycle is an amount of time-domain PRACH opportunities per SSB group.

35. The method of claim 33, wherein the relative offset of an index relative to a previous mapping cycle of the non-initial mapping cycle is an index step size of the one or more SSB groups.

36. The method of claim 22, comprising receiving a configured number of PRACH repetitions.

37. The method of claim 36, wherein the configured PRACH repetition number is at least one of a cell-specific configured number and a UE-specific configured number.

38. The method of claim 37, wherein the configured PRACH repetition number is the same as a repetition number of the number of PRACH repetitions.

39. The method of claim 37, wherein the configured PRACH repetition number is different from a repetition number of the number of PRACH repetitions.

40. The method of claim 38, wherein the UE-specific configured number of times is indicated by at least one of frequency domain resources and code domain resources to implicitly indicate an actual total number of the number of PRACH repetitions.

41. The method of claim 40, wherein the frequency domain resources are associated with frequency domain PRACH opportunity indexes.

42. The method of claim 40, wherein the code domain resource is associated with a PRACH preamble index.

43. An apparatus comprising: a non-transitory computer-readable medium having computer-executable instructions stored thereon; Receiving circuit system; Transmission circuit system; and a processor coupled to the non-transitory computer-readable medium, the receiving circuitry, and the transmitting circuitry, Wherein the computer-executable instructions cause the processor to implement the method of any one of claims 1-21.

44. An apparatus comprising: a non-transitory computer-readable medium having computer-executable instructions stored thereon; Receiving circuit system; Transmission circuit system; and a processor coupled to the non-transitory computer-readable medium, the receiving circuitry, and the transmitting circuitry, Wherein the computer-executable instructions cause the processor to implement the method of any one of claims 22-42.

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