Preamble distribution across random access channel occasion groups

Abstract

Preamble distribution across random access channel occasion groups is provided. A method for preamble distribution across random access channel occasion groups may include determining a set of contention-based preambles associated with a synchronization signal block index / physical broadcast channel block index per one or more valid physical random access channel occasions for multiple physical random access channel transmissions. The method may also include determining at least one preamble subset of the determined set of contention-based preambles and transmitting the multiple physical random access channel transmissions with a preamble from the determined preamble subset.

Description

PREAMBLE DISTRIBUTION ACROSS RANDOM ACCESS CHANNEL OCCASION GROUPSTECHNICAL FIELD:

[0001] Some example embodiments may generally relate to mobile or wireless telecommunication systems, such as Long Term Evolution (LTE) or fifth generation (5G) new radio (NR) access technology, or 5G beyond, or other communications systems. For example, certain example embodiments may relate to preamble distribution across random access channel occasion groups.BACKGROUND:

[0002] Examples of mobile or wireless telecommunication systems may include the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN), LTE-Advanced (LTE-A), MulteFire, LTE-A Pro, and / or fifth generation (5G) radio access technology or new radio (NR) access technology. Fifth generation (5G) wireless systems refer to the next generation (NG) of radio systems and network architecture. 5G network technology is mostly based on new radio (NR) technology, but the 5G (or NG) network can also build on E-UTRAN radio. It is estimated that NR may provide bitrates on the order of 10-20 Gbit / s or higher, and may support at least enhanced mobile broadband (eMBB) and ultra-reliable low-latency communication (URLLC) as well as massive machine-type communication (mMTC). NR is expected to deliver extreme broadband and ultra-robust, low-latency connectivity and massive networking to support the Internet of Things (loT).SUMMARY:

[0003] Various exemplary embodiments may provide an apparatus including at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to determine a set of contention-based preambles associated with a synchronization signal block index / physical broadcast channel block index per one or more valid physical randomaccess channel occasions for multiple physical random access channel transmissions. The apparatus may also be caused to determine at least one preamble subset of the determined set of contention-based preambles and transmit the multiple physical random access channel transmissions with a preamble from the determined preamble subset.

[0004] Certain exemplary embodiments may also provide an apparatus including at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to select a set of contentionbased preambles mapped to one or more groups of random access channel occasions for a plurality of transmissions. The apparatus may also be caused to partition the set of preambles into a plurality of preamble subsets.

[0005] Some exemplary embodiments may provide a method including determining a set of contention-based preambles associated with a synchronization signal block index / physical broadcast channel block index per one or more valid physical random access channel occasions for multiple physical random access channel transmissions. The method may also include determining at least one preamble subset of the determined set of contention-based preambles and transmitting the multiple physical random access channel transmissions with a preamble from the determined preamble subset.

[0006] Various exemplary embodiments may provide a method including selecting a set of contention-based preambles mapped to one or more groups of random access channel occasions for a plurality of transmissions. The method may also include partitioning the set of preambles into a plurality of preamble subsets.

[0007] Other example embodiments are provided or described for each of the example methods, including: means for performing any of the example methods; a non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause the at least one processor to perform any of the example methods; and an apparatus including at least one processor, and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform any of theexample methods.

[0008] The details of one or more examples of embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF THE DRAWINGS:

[0009] For proper understanding of example embodiments, reference should be made to the accompanying drawings, as follows:

[0010] FIG. 1 illustrates an example of a 4-step random access channel (RACH);

[0011] FIG. 2 illustrates an example of time-domain resource determination for RACH occasions;

[0012] FIG. 3 illustrates an example of synchronization signal block to RACH occasion mapping;

[0013] FIG. 4 illustrates an example associating preambles with valid RACH occasions (ROs) of RO groups for a different number of multiple PRACH transmissions, according to various exemplary embodiments;

[0014] FIG. 5 illustrates another example of associating preambles with valid ROs of RO groups for a different number of multiple PRACH transmissions, according to certain exemplary embodiments;

[0015] FIG. 6 illustrates an example of a flow diagram of a method, according to various exemplary embodiments;

[0016] FIG. 7 illustrates an example of a flow diagram of a method, according to some exemplary embodiments; and

[0017] FIG. 8 illustrates a set of apparatuses, according to various exemplary embodiments.DETAILED DESCRIPTION:

[0018] It will be readily understood that the components of certain example embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. The following is a detailed description of some exemplary embodiments of systems, methods,apparatuses, and non-transitory computer program products for preamble distribution across RACH occasion groups. Although the devices discussed below and shown in the figures refer to 5G or Next Generation NodeB (gNB) devices and user equipment (UE), this disclosure is not limited to only gNBs and UEs. For example, the following description may also apply to any type of network access node and UE.

[0019] In an NR network, a communication connection may be initiated between devices, such as a UE and a network device, such as a base station, gNB, etc., through a random access (RA) procedure by employing a physical random access channel (PRACH). One type of contention-based RACH is known as 4-step RACH. FIG. 1 illustrates an example of the 4-step RACH, in which a UE 101 may transmit a specific preamble to a gNB 102 via physical random-access channel (PRACH) using a specific resource called RACH occasion or PRACH occasion (RO). This specific preamble may be included in a message (Msgl).

[0020] The gNB 102 may reply with a random-access response (RAR) message (Msg2), which may include, for example, a detected preamble ID, a time-advance command, a temporary cell radio network temporary identifier (TC-RNTI), and / or and uplink (UL) grant for the transmission of a radio resource control (RRC) request, which may be included in a message (Msg3), on a physical uplink shared channel (PUSCH). The UE 101 may transmit, to the gNB 102, a response, as the Msg3, over the scheduled PUSCH with an ID for contention resolution. The gNB 102 may transmit the contention resolution message (Msg4) with the contention-resolution ID.

[0021] Upon reception of Msg4, the UE 101 may send an acknowledgement (ACK) on a physical uplink control channel (PUCCH) if a contention-resolution ID is carried by Msg4. Prior to Msgl, the gNB 102 may send, to the UE 101, a synchronization signal block (SSB). The SSB may be part of a DL beam sweeping procedure. The UE 101 may select an index of a preferred SSB beam and decode an associated physical broadcast channel (PBCH) for a master information block (MIB) and / or system information block (SIB). This index may be used by the UE 101 to identify a suitable RO for the preamble transmission (Msgl), according to the SSB-to-RO mapping implicitly conveyed by SIB1.

[0022] 2-step RACH may be similar to 4-step RACH, except that Msgl and Msg3 may be combined in a MsgA and sent by the UE to the gNB without waiting for feedback from the gNB. Similarly, the gNB may combine Msg2 and Msg4 into MsgB.

[0023] A time-domain resource for RACH occasions (ROs) may be RRC configured by, for example, prach-Configurationlndex in rach-ConfigGeneric. With the parameters indicated by prach-Configurationlndex, the UE may determine the preamble format for PRACH and apply a procedure to find the ROs in time-domain.

[0024] FIG. 2 illustrates an example of time-domain resource determination for RACH occasions. The prach-Configurationlndex may be, for example, a value of 251. A preamble format C2 may be used and ROs may be allocated at system frame numbers (SFN) (nSFW) that satisfy nSFNmod 1 = 0, such that all SFN numbers are valid. In the example of FIG. 2, ROs may be allocated at subframe numbers 2 and 7 within each of the determined SFNs. Within each of the determined subframes, the remaining parameters in the considered row may indicate that ROs will start at symbol numbers 0, 6, 14, 20. The symbol number may be continuously counted regardless of the number of slots within the subframe, which may depend on the subcarrier spacing configured for PRACH. The ROs duration may be, for example, 6 symbols or less. The validity of the ROs may be determined as valid if the RO is within UE symbols and / or if the RO has a sufficient gap after the last SSB / DE symbol when the RO is within flexible symbols.

[0025] In the frequency domain, parameters msgl -Frequency Start and msgl -FDM may be configured in RACH-ConfigGeneric to indicate an offset of the lowest RO in frequency domain from the start of an initial uplink bandwidth part (BWP) and the number of ROs multiplexed in frequency domain for each time instance, respectively. The ROs may be indexed as nRA= {0,1, ... , M — 1], where M equals a higher-layer parameter msgl -FDM, and the ROs may be numbered in increasing order within the initial UE BWP, starting from the lowest frequency.

[0026] FIG. 3 illustrates an example of SSB to RO mapping. The mapping of SSB indexes to the ROs may be used by a UE to determine which ROs are associated tothe SSB index selected before the start of the RACH procedure. The different SSB indexes may be beamformed in different directions in a cell, and selection of a wrong SSB index may result in a failure of the RACH procedure. A parameter ssb- perRACH-OccasionAndCB-PreamblesPerSSB may be configured in RACH- ConfigCommon and may indicate information, such as (i) the number of SSB indexes per RO and (ii) the number of contention-based preambles per SSB index. For Type- 1 random access (RA) procedure, the UE may be provided with a number N of SS / PBCH block indexes associated with at least one PRACH occasion and a number R of contention-based preambles per SS / PBCH block index per valid PRACH occasion by ssb-perRACH-OccasionAndCB-PreamblesPerSSB. The UE then may map the SSB indexes to the time-frequency grid of ROs in increasing order of frequency resource indices, time resource indices of the ROs within a PRACH slots, and the PRACH slots, sequentially.

[0027] FIG. 3 also illustrates an example of valid ROs in one frame determined in FIG. 2. The following additional configuration may be assumed: DDDSU slot structure (D - downlink slot, S - special slot, U - uplink slot.), Msgl-FDM = two, and ssb-perRACH-OccasionAndCB-PreamblesPerSSB is one -half. Based on the configuration, two ROs may be multiplexed in the frequency domain (Msgl -FDM = two) and any two frequency domain ROs may be mapped to the same SSB index (ssb-perRACH-OccasionAndCB-PreamblesPerSSB = 1 / 2).

[0028] In relation to the SSB-to-RO mapping, 3rdgeneration partnership project (3GPP) may define an association period, starting from frame 0, for mapping SSB indexes to PRACH occasions as the smallest value in the set determined by the PRACH configuration period. All of the SSB indexes may be mapped at least once to the PRACH occasions within the association period. The PRACH configuration period may be determined at the UE based on the configured PRACH configuration index. Table 1 provides an example of mapping between a PRACH configuration period and the association period, as follows:

[0029] The association period may be defined as a period of time in which all SSB indexes may be mapped to at least one RO. For example, in the examples of FIGs. 2 and 3, the configuration period may be 10ms, since ROs can be found in each SFN, and the association period may be a multiple of the configuration period, such as a multiple of 10ms.

[0030] The preambles for PRACH transmissions in ROs mapped to certain SSB indexes may be determined based on a network configuration of at least two parameters: ssb-perRACH-OccasionAndCB-PreamblesPerSSB and totalNumberOfRA-Preambles. For example, for Type-1 random access procedure, the UE may be provided with a total number of preambles Np°^mbleby totalNumberOfRA-Preambles. For Type-1 random access procedure, or for Type-2 random access procedure with separate configuration of PRACH occasions from Type 1 random access procedure, if TV < 1, one SS / PBCH block index may be mapped to 1 / / V consecutive valid PRACH occasions and R contention -based preambles with consecutive indexes associated with the SS / PBCH block index per valid PRACH occasion start from preamble index 0. If N > 1, R contention-based preambles with consecutive indexes associated with SS / PBCH block index n, 0 < n < N — 1, per valid PRACH occasion start from preamble index n ■ Np°g^mbie / N. ^-preamble may be an integer multiple of N. In some exemplary embodiments, the terms SSB and SS / PBCH block may be used interchangeably. Herein, N may refer to the value of the CHOICE part of the field ssb-perRACH-OccasionAndCB- PreamblesPerSSB, whereas R refers to the value of the ENUMERATED part of the field ssb-perRA CH- OccasionAndCB-PreamblesPerSSB.

[0031] For multiple PRACH transmissions with the same transmission (Tx) beam, an RO group for multiple PRACH transmissions may be formed on ROs shared with or separate from the ROs for single PRACH transmission. At least one RO group may include valid RO(s) for a specific number of multiple PRACH transmissions.RO groups may include multiple ROs in which a UE transmits multiple PRACH transmissions.

[0032] Multiple PRACH transmissions with different numbers (e.g., 2, 4 and 8 PRACH transmissions) may be transmitted on separate ROs or on shared ROs with separate preamble(s). When the PRACH transmissions are transmitted on shared ROs, two UEs transmitting different number of multiple PRACH transmissions (e.g., 2 and 8) may transmit the PRACH repetitions in shared ROs. The two UEs may have to use different preambles for the transmission to avoid cross-interference.

[0033] RO groups may allow a gNB to know which ROs the UE may be transmitting multiple PRACH transmissions and blindly combine the multiple PRACH transmissions. RO groups may have different sizes, such as different numbers of ROs within the group, based on the number of multiple PRACH transmissions used for the group. The ROs of RO groups of different sizes may be the same, as long as different preambles are being used for transmission of the PRACH in the different RO groups.

[0034] Various exemplary embodiments may provide advantages and / or improvements to the UE determining preambles associated (e.g., to be used) with RO groups for different values of the number of multiple PRACH transmissions, or to the UE determining preambles associated with different values of the number of multiple PRACH transmissions, when the RO groups share ROs with other RO groups of different sizes, or when RO groups may not share ROs between the different groups of different sizes, such as when the different values of the number of multiple PRACH transmissions are transmitted on shared or separate ROs.

[0035] Certain exemplary embodiments discussed herein may use the terms RO group of size N interchangeably with the term N ROs over which the UE can perform N PRACH transmissions. The use of these different terms is not intended to limit the scope of the embodiments and is used solely for ease of explanation.

[0036] Various exemplary embodiments may provide one or more procedures for a UE to determine contention-based preambles, for example, with consecutive indices associated with an SSB index and with RO groups or with RO(s) belonging to RO groups for a different number of multiple PRACH transmissions. The UE maydetermine the contention-based preambles for a number of multiple PRACH transmissions based on whether the ROs of an RO group for the number of multiple PRACH transmissions are shared with another RO group for a different number of multiple PRACH transmissions or based on the number of values configured by the network for the number of multiple PRACH transmissions. The association of the preamble to the RO may be independent of whether one or more SS / PBCH block indices are mapped to each RO of each RO group. The association of the contentionbased preambles with the one or more SS / PBCH block indices mapped to each RO of each RO group may be assumed to be carried out as per legacy procedure. Certain exemplary embodiments may provide that the preamble collision probability may be approximately equalized for different RO groups assuming that RO groups or RO group sizes are selected.

[0037] The exemplary embodiments herein may refer to contention-based preambles. However, the exemplary embodiments are not limited thereto, and may equally apply to contention-free preambles.

[0038] Certain exemplary embodiments may provide that the UE may determine a set / group of R contention-based preambles with consecutive indices, or a number of R contention-based preambles with consecutive indices, associated with each of the one or more SS / PBCH block indices mapped to valid ROs of RO groups for multiple PRACH transmissions. The UE may also determine M sub-set(s) of the R preambles and each sub-set may be associated to a number of multiple PRACH transmissions. Each sub-set associated to a number of multiple PRACH transmissions may refer to each sub-set that may be used for preamble selection for transmitting multiple PRACH transmissions over valid ROs of RO groups for the number of multiple PRACH transmissions.

[0039] Some exemplary embodiments may provide that the UE may divide / partition the R preambles associated with each of the one or more SS / PBCH block indices mapped to valid ROs of RO groups for multiple PRACH transmissions into M subsets, which may be referred toM may represent the number of different cell-specific values configured by network for the number of multiple PRACH transmissions and may associate the M sub-sets to the M numbers ofmultiple PRACH transmissions.

[0040] In certain exemplary embodiments, M may represent the number of RO groups of different sizes that each of the valid ROs belongs to, i.e., the number of multiple PRACH transmissions the corresponding valid RO may be used for. M may be different for different valid ROs. The UE may also associate the M sub-sets to the M RO groups of different sizes. In other words, M may be the number of values of multiple PRACH transmissions that the valid ROs may be used for. Some exemplary embodiments may provide that the UE may determine the number M of RO groups of different sizes that the starting / first RO of an RO group belongs to for each starting / first RO of each RO group and may divide / partition the R preambles into M sub-sets. The value of M may be different for starting / first RO of different RO groups. Each RO group size may be counted once, such that it may be assumed that two RO groups of the same size sharing ROs (i.e., constituted of the same ROs) may be considered as a single group.

[0041] As an example, when a valid or a starting / first RO belongs to RO groups of size 8 ROs, 4 ROs and 2 ROs, e.g., the valid or starting / first RO may be used for 8, 4, and 2 PRACH transmissions, then M may equal 3. As another example, when a valid or a starting / first RO belongs to RO groups of size 4 ROs and 2 RO, e.g., the valid or starting / first RO may be used for 4 and 2 PRACH transmissions, then M may equal 2. As a further example, when a valid or a starting / first RO belongs to an RO group of size 2 ROs, e.g., the valid or starting / first RO may be used for 2 PRACH transmissions, then M may equal 1.

[0042] For a number of multiple PRACH transmissions, only a subset of the R contention-based preambles per SS / PBCH block index per valid PRACH occasions may be available to the UE. The subset may start from index n - R / M, wherein 0 < n < M — 1.

[0043] Various exemplary embodiments may provide for M > 1 that the UE may associate preambles in Po, which may have the lowest index, to the RO groups of a largest size and preambles in other sub-sets (Pi and P2) to the RO groups of smaller size. For example, for M = 3 in which the gNB may configure sizes of RO groups (i.e., values of the number of multiple PRACH transmissions) {2, 4, 8} as thepossible values for numbers of multiple PRACH transmissions and R = 12. Pomay contain preambles from 0 to 3 and the UE may associate Poto the RO group(s) of size 8. Pi may contain preambles from 4 to 7 and the UE may associate Ptto the RO group(s) of size 4. P2may contain preambles from 8 to 11 and the UE may associate P2to the RO group(s) of size 2.

[0044] Some exemplary embodiments may provide for M > 1 that the UE may associate preambles in Po, which may have the lowest index, to the RO groups of a smallest size and preambles in other sub-sets (Pi and P2) to the RO groups of larger size. For example, for M = 3 in which the gNB may configure sizes of { 2, 4, 8 } as the possible values for numbers of multiple PRACH transmissions and R = 12. Pomay contain preambles from 0 to 3 and the UE may associate Poto the RO group(s) of size 2. Ptmay contain preambles from 4 to 7 and the UE may associate Ptto the RO group(s) of size 4. P2may contain preambles from 8 to 11 and the UE may associate P2to the RO group(s) of size 8.

[0045] The M sub-sets may have equal size, such that sub-sets Poto PM-i may be composed of preambles. The M portion of the preambles may be of equal sizeas long as R is a multiple of M. If the configured R is not a multiple of M, the subsets Poto PM-2, for example, may be composed of |^j preambles and sub-set PM-I (highest preamble indexes) contains R — (M — 1) ■ preambles.

[0046] Whether the UE may associate preambles in Poto the RO groups of a smallest size and preambles in other sub-sets to the RO groups of larger size or may associate preambles in Poto the RO groups of a larger size and preambles in other sub-sets to the RO groups of smaller size, may be based on the number of RO groups of a certain size in a reference time period and on M sub-sets with at least one subset of unequal size. For example, the sub-set with preambles at the highest index may have more preambles, and therefore the UE may associate the sub-set to the number of multiple PRACH transmissions with the lowest number of groups within a reference timer period to lower the preamble collision probability. For example, for R = 10 and M = 3, there may be two sub-sets (Po and Pi) of size 3 and one subset (P2) of size 4. If within a reference time period there is one RO group of size 8,two RO groups of size 4 and four RO groups of size 2, P2 may be associated to the RO group of size 8, Po may be associated to the RO group of size 2 and Pi may be associated to the RO group of size 4.

[0047] Various exemplary embodiments may provide for either or both of the UE associating preambles in Poto the RO groups of a smallest size and preambles in other sub-sets to the RO groups of larger size or associating preambles in Poto the RO groups of a largest size and preambles in other sub-sets to the RO groups of smaller size. The gNB may switch between the procedures for associating the preambles and may configure a cell accordingly. The cell may be configured using higher layer signaling. For example, a flag in SIB 1 may instruct the UE to follow a certain order of the preamble indices in the association of each of the M preamble sub-set(s) to RO groups sizes i.e., to different numbers of multiple PRACH transmissions. The certain order in the association may be, for example, a decreasing or increasing order or a mixed order. For example, in the case of mixed order and in case M = 3 having the set {2, 4, 8} PRACH transmissions, Pomay be associated to RO group(s) of size 4,may be associated to RO group(s) of size 2, and P2may be associated to RO group(s) of size 8.

[0048] The size of each of the M preamble sub-set(s) may be proportional or inversely proportional to the number of RO groups of a certain size, e.g., for a certain number of multiple PRACH transmissions, or to the number of starting / first ROs for a certain number of multiple PRACH transmissions in a reference time period. The reference time period may be a number of association pattern periods. The same, or substantially similar, RACH preamble collision probability may be provided for multiple PRACH transmissions in RO groups of different sizes. For example, if there are GsRO groups of size 8 ROs, G4RO groups of size 4 ROs and G2RO groups of size 2 ROs, the UE may determine the size of the M preamble sub-sets based on proportionality factors that are determined based on the number of RO groups of a certain size within the reference time period.

[0049] As an example, for M=3, where Rs, R4and R2refer to the size of the preamble sub-sets for each number of multiple PRACH transmissions, deriving the size of the preamble sub-sets may be performed by the UE calculating the size of thepreamble sub-set for the RO group of smallest size (e.g., 2) so that it satisfies Equation (2) or Equation (3):

[0050] For example, Equation (2) may be applicable for performing a flooring operation and Equation (3) may be application for performing a ceiling operation instead in some cases where the flooring operation would give a number of 0Q preambles. In Equation (2) or Equation (3) above, R8= — * R2and R4= G2 / G4* G8R2, such that the size of the preamble sub-set for RO groups of size 8 is G2 / G8times the size of the preamble sub-set for RO group of size 2 and that the size of the preamble sub-set for RO groups of size 4 is G2IG4times the size of the preamble sub-set for RO group of size 2. Once R2 is calculated based on Equation (2) or Equation (3), R8 and R4 may be directly derived.

[0051] According to some exemplary embodiments, Rs and R4 may not be derived directly based on R2 as discussed above, and instead the UE may calculate the size of the preamble sub-set for the RO group of medium size (e.g., 4), if any, so that it satisfies Equation (4):R4= [ R - R2) / G4 / G8+ 1)] (4)

[0052] The UE may then calculate the size of the preamble set for the RO group of largest size (e.g., 8) as: R8= (R — R2— R4). A ceiling operation instead of floor operation may be used in Equation (4) in some cases where the flooring operation would give a number of 0 preambles.

[0053] In some exemplary embodiments, the total number of RO groups (or of starting / first ROs) for all of the configured values of the number of multiple PRACH transmissions within the reference time period or the number of RO groups (or of starting / first ROs) for each of the configured values of the number of multiple PRACH transmissions within the reference time period may be configured by the network. The UE may determine the size of each of the M preamble sub-set(s) basedon the configuration. In one example, the UE may determine the size of each of the M sub-set(s) so that the sizes may be proportional or inversely proportional to the number of RO groups of a certain size, i.e., for a certain number of multiple PRACH transmissions, or to the number of starting / first ROs for a certain number of multiple PRACH transmissions in a reference time period.

[0054] In one example, the gNB may configure the number of RO groups for each of the configured values of number of multiple PRACH transmissions within the reference time period, as G2, G4and Gsfor 2, 4 and 8 multiple PRACH transmissions, respectively. In this case, the UE may determine the size of each of the M preamble sub-set(s) as by previous example above.

[0055] In certain exemplary embodiments, the size of each of the M preamble subset^) may be determined at the UE based on configured parameters. Each configured parameter may indicate a starting preamble and a number of preambles out of the R preambles to be associated with each of the M sub-set(s). The UE then may perform the transmission of a number of multiple PRACH transmissions with a preamble randomly chosen within the preamble sub-set associated to the number of multiple PRACH transmissions.

[0056] Various exemplary embodiments may provide that the size of each of the M preamble sub-set(s) may be configured. For example, for R = 12, the gNB may configure R2= 2, R4= 4 and Rs= 6. The configuration may be determined at the gNB based on the PRACH configuration and based on the number of RO groups within the reference time period.

[0057] FIG. 4 illustrates an example associating preambles with valid ROs of RO groups for different numbers of multiple PRACH transmissions, according to various exemplary embodiments. The UE may partition R preambles associated with each of the one or more SS / PBCH block indices mapped to the valid ROs of RO groups for multiple PRACH transmissions into M sub-sets. In the example shown in FIG. 4, M = 3 may be the number of configured values of number of multiple PRACH transmissions. The preambles in Po, with lowest index, may be associated with the RO groups of largest size. The M sub-sets may have equal size.

[0058] Various exemplary embodiments may provide one or more procedures forassociating preambles with part or all of the valid ROs of RO groups to result in the configuration shown in FIG. 4. Part of the valid ROs of RO groups may be the first / starting RO of the RO groups. For example, in a first process, the UE may be configured with three values of number of multiple PRACH transmissions (i.e. {2, 4, 8} PRACH transmissions) and corresponding SSB-RSRP thresholds for determination of the number of multiple PRACH transmissions at the UE. The UE may determine from the configuration that M = 3. In a second process, which may occur at the same time as the first process, the UE may be configured with a set of R = 12 preambles associated with an SSB index. In a third process, the UE may measure SSB-RSRP for different SSB indexes, may select an SSB index among the measured different SSB indexes, and compare the measured SSB-RSRP of the selected SSB index to the configured thresholds. The UE may therefore determine, as an example, that the UE may need to transmit a number of 4 PRACH transmissions.

[0059] In a fourth process, the UE may determine at least the RO groups of size 4 within a reference time period among the valid configured ROs mapped to the selected SSB index, e.g., the UE may determine at least the ROs that could be used for performing 4 PRACH transmissions. In the example of FIG. 4, the time period may extend over 8 consecutive valid ROs mapped to the selected SSB index, and the UE may determine two RO groups of size 4. In another example of the fourth process, the UE may determine the RO groups for all of the number of multiple PRACH transmissions and consider the RO groups of size 4 for the multiple PRACH transmissions.

[0060] In a fifth process, the UE may determine R preambles associated with the selected SSB index. The UE may then partition the R preambles into M sub-sets and associate — preambles to RO group(s) of size 4. In the example shown in FIG. 4, two RO groups of size 4 are shown sharing ROs with the group of 8 ROs and of 2 ROs. The UE may associate a second sub-set of — preambles, from a range of the -th, with RO groups for a number of 4 PRACHtransmissions, or with part or all of the valid ROs of such RO groups. The preambleused by the UE for the 4 PRACH transmissions may be randomly selected from the sub-set of — preambles. The preambles of the sub-set for 4 PRACH transmissions (i.e., for the RO groups of size 4) may be different from those of the sub-sets associated to RO groups, of size 8 and of size 2.

[0061] In a sixth process, the UE may select the next available RO group of size 4 and transmit the multiple, e.g., 4, PRACH transmissions with a preamble selected randomly within the second preamble sub-set.

[0062] FIG. 5 illustrates another example of associating preambles with valid ROs of RO groups for different numbers of multiple PRACH transmissions, according to certain exemplary embodiments. The UE may partition the R preambles into M subsets. M may not be fixed and may be determined at the UE based on the number of RO groups with different sizes that share one or more valid ROs. In the example of FIG. 5, 8 ROs may be within a reference time period for a first nRA, which may be an indicator of a center frequency of the ROs and may be set to nRA= 0, and only 4 ROs may be within the same reference period for a second nRA, which may be set tonRA=1- So, for the first nRA, all RO group sizes (e.g., for 2, 4 and 8 PRACH transmissions) may be possible, whereas for the second nRA, only two RO group sizes may be possible (e.g., for 2 and 4 PRACH transmissions). The preamble partitioning may depend on the number of overlapping RO groups of different size, which may be the number of RO groups of different sizes that each of the valid ROs belongs to, e.g., the number of values of the number of multiple PRACH transmissions the valid ROs may be used for. The R preambles may be partitioned into M=3 preamble sub-sets for the valid ROs in the first nRAand into M=2 preamble sub-sets for the valid ROs in the second nRA. This advantageously provides that the preamble partitioning may be optimized and the preamble collision probability may be reduced.

[0063] Certain exemplary embodiments may provide another one or more procedures for associating preambles with valid ROs of RO groups to result in the configuration shown in FIG. 5. For example, in a first process, the UE may be configured with three SSB-RSRP thresholds defining three different numbers of multiple PRACH transmissions, e.g., {2, 4, 8}. In a second process, which mayoccur at the same time as the first process, the UE may be configured with a set of R = 12 preambles associated with an SSB index. In a third process, the UE may measure SSB-RSRP for different SSB indexes, may select an SSB index among the measured different SSB indexes, and compare the measured SSB-RSRP of the selected SSB index to the configured thresholds. The UE may determine that the UE may need to transmit a number of 4 PRACH transmissions on valid ROs mapped to the selected SSB index.

[0064] In a fourth process, the UE may determine M for either all valid ROs for multiple PRACH transmissions or for the starting / first RO of each RO group. In the example shown in FIG. 5, the reference time period may extend over a number of 8 valid ROs mapped to the selected SSB index, and the UE may determine three RO groups of size 4 within the time period.

[0065] In a fifth process, the UE may determine R preambles associated with the selected SSB index. The UE may then partition the R preambles into M sub-sets and associate — preambles to RO group(s) of size 4. For the first nRA(i.e. nRA=0), M=3 may be set and the UE may associate the second sub-set of — preambles from the 0^) -th to the ^2 ■ — 1 -th to the RO groups for a number of 4 PRACH transmissions (or with part or all of the valid ROs of such RO groups). The preamble used by the UE for the determined number of 4 PRACH transmission may be randomly selected from the sub-set of — preambles associated to the RO groups for a number of 4 PRACH transmissions, or with part or all of the valid ROs of such RO groups. The selected preamble may be different from the preambles of the sub-sets associated to RO groups of size 8 and of size 2.

[0066] For the second nRA(nRA= 1), M=2 may be set and the UE may associate the first sub-set of — preambles Pofrom the (O)-th to the [— — 1 I -th to the RO groups for a number of 4 PRACH transmissions (or with part or all of the valid ROs of such RO groups). The preamble used by the UE may be randomly chosen from the sub-set of — preambles associated to the RO groups for a number of 4 PRACH transmissions, or with part or all of the valid ROs of such RO groups. The selectedpreamble may be different than the preambles in the sub-sets associated to the RO group of size 2.

[0067] In the sixth process, the UE may select the next available RO group of size 4 and may transmit the multiple, e.g., 4, PRACH transmissions with a preamble selected randomly within the associated preamble sub-set.

[0068] Various exemplary embodiments may provide advantages of preamble separation for multiple PRACH transmissions on a shared RO that may avoid crossinterference between different values of multiple PRACH transmissions. Preamble utilization may be optimized to allow the maximum number of preambles per value of the number of multiple PRACH transmissions.

[0069] FIG. 6 illustrates an example flow diagram of a method, according to certain exemplary embodiments. In an example embodiment, the method of FIG. 6 may be performed by a network element, or a group of multiple network elements in a 3 GPP system, such as ETE or 5G-NR. For instance, in an exemplary embodiment, the method of FIG. 6 may be performed by a user equipment similar to apparatus 810 illustrated in FIG. 8.

[0070] According to various exemplary embodiments, the method of FIG. 6 may include, at 610, determining a set of contention-based preambles associated with an SS / PBCH block index per one or more valid PRACH occasions for multiple PRACH transmissions. At 620, the method may also include determining at least one preamble subset of the determined set of contention-based preambles, and at 630, transmitting the multiple PRACH transmissions with a preamble from the determined preamble subset.

[0071] Certain exemplary embodiments may provide that the at least one preamble subset is determined by partitioning the set of preambles into one or more preamble subsets. The method may also include determining a number of the one or more preamble subsets based on a number of different cell-specific values configured by a network for a number of the multiple physical random access channel transmissions, and / or the number of the one or more preamble subsets based on a number of values of multiple physical random access channel transmissions the one or more valid physical random access channel occasions are to be used for. Themethod may further include determining, for a first random access channel occasion of each of a group of random access channel occasions, a number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped. A number of preamble subsets is set as the number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped.

[0072] Some exemplary embodiments may provide that a size of each of the preamble subset is inversely proportional to the number of groups of random access channel occasions for a number of multiple physical random access channel transmissions in a reference time period. The method may also include associating preambles in a preamble subset with a lowest index with groups of random access channel occasions for a largest value of the number of multiple physical random access channel transmissions and associate the remaining preambles with the remaining preamble subsets in decreasing order of value of the number of multiple physical random access channel transmissions. Alternatively, the method may include associating preambles in a preamble subset with a lowest index with groups of random access channel occasions for a smallest value of the number of multiple physical random access channel transmissions and associate the remaining preambles with the remaining preamble subsets in increasing order of value of the number of multiple physical random access channel transmissions. The one or more valid physical random access channel occasions may be mapped to the groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions.

[0073] FIG. 7 illustrates an example flow diagram of a method, according to certain exemplary embodiments. In an example embodiment, the method of FIG. 7 may be performed by a network element, or a group of multiple network elements in a 3 GPP system, such as LTE or 5G-NR. For instance, in an exemplary embodiment, the method of FIG. 7 may be performed by a base station or gNB similar to apparatus 820 illustrated in FIG. 8.

[0074] According to various exemplary embodiments, the method of FIG. 7 may include, at 710, selecting a set of contention-based preambles mapped to one or more groups of ROs for a plurality of transmissions. At 720, the method may include partitioning the set of preambles into a plurality of preamble subsets.

[0075] Some exemplary embodiments may provide that the method may also include partitioning the set of preambles into the plurality of preamble subsets based on a number of different cell-specific values configured for the plurality of transmissions. The method may include partitioning the set of preambles into the plurality of preamble subsets based on a number of groups of ROs which have different sizes.

[0076] Certain exemplary embodiments may provide that the method includes determining, for a first random access channel occasion of each of a group of random access channel occasions, a number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped. A number of preamble subsets is set as the number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped. A size of each of the preamble subset is inversely proportional to the number of groups of random access channel occasions of a specific size in a reference time period. The method may also include providing the plurality of preamble subsets to a user equipment.

[0077] FIG. 8 illustrates a set of apparatuses 810 and 820 according to various exemplary embodiments. In the various exemplary embodiments, the apparatus 810 may be may be an element in a communications network or associated with such a network, such as a UE, RedCap UE, SL UE, mobile equipment (ME), mobile station, mobile device, stationary device, loT device, or other device. For example, the UEs according to various exemplary embodiments as discussed above may be examples of apparatus 810. It should be noted that one of ordinary skill in the art would understand that apparatus 810 may include components or features not shown in FIG. 8. In addition, apparatus 820 may be a network, network entity, element of the corenetwork, or element in a communications network or associated with such a network, such as a base station, a network entity (NE), or a gNB. For example, the network and the gNB according to various exemplary embodiments discussed above may be examples of apparatus 820. It should be noted that one of ordinary skill in the art would understand that apparatus 820 may include components or features not shown in FIG. 8.

[0078] According to various exemplary embodiments, the apparatus 810 may include at least one processor, and at least one memory, as shown in FIG. 8. The memory may store instructions that, when executed by the processor, cause the apparatus 810 to determine a set of contention-based preambles associated with a synchronization signal block index / physical broadcast channel block index per one or more valid physical random access channel occasions for multiple physical random access channel transmissions. The apparatus 810 may also be caused to determine at least one preamble subset of the determined set of contention-based preambles and transmit the multiple physical random access channel transmissions with a preamble from the determined preamble subset.

[0079] According to various exemplary embodiments, the apparatus 820 may include at least one processor, and at least one memory, as shown in FIG. 8. The memory may store instructions that, when executed by the processor, cause the apparatus 820 to select a set of contention-based preambles mapped to one or more groups of random access channel occasions for a plurality of transmissions and partition the set of preambles into a plurality of preamble subsets.

[0080] Various exemplary embodiments described above may provide several technical improvements, enhancements, and / or advantages. For instance, some exemplary embodiments may provide advantages and / or improvements to the UE or gNB determining preambles associated with RO groups having a different number of multiple PRACH transmissions when the RO groups share ROs with other RO groups of different sizes, or when RO groups may not share ROs between the different groups.

[0081] In some example embodiments, apparatuses 810 and / or 820 may include one or more processors, one or more computer-readable storage medium (for example,memory, storage, or the like), one or more radio access components (for example, a modem, a transceiver, or the like), and / or a user interface. In some example embodiments, apparatuses 810 and / or 820 may be configured to operate using one or more radio access technologies, such as GSM, LTE, LTE-A, NR, 5G, WLAN, WiFi, NB-IoT, Bluetooth, NFC, MulteFire, and / or any other radio access technologies.

[0082] As illustrated in the example of FIG. 8, apparatuses 810 and / or 820 may include or be coupled to processors 812 and 822, respectively, for processing information and executing instructions or operations. Processors 812 and 822 may be any type of general or specific purpose processor. In fact, processors 812 and 822 may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), and processors based on a multi-core processor architecture, as examples. While a single processor 812 (and 822) for each of apparatuses 810 and / or 820 is shown in FIG. 8, multiple processors may be utilized according to other example embodiments. For example, it should be understood that, in certain example embodiments, apparatuses 810 and / or 820 may include two or more processors that may form a multiprocessor system (for example, in this case processors 812 and 822 may represent a multiprocessor) that may support multiprocessing. According to certain example embodiments, the multiprocessor system may be tightly coupled or loosely coupled to, for example, form a computer cluster).

[0083] Processors 812 and 822 may perform functions associated with the operation of apparatuses 810 and / or 820, respectively, including, as some examples, precoding of antenna gain / phase parameters, encoding and decoding of individual bits forming a communication message, formatting of information, and overall control of the apparatuses 810 and / or 820, including processes illustrated in FIGs. 4-7.

[0084] Apparatuses 810 and / or 820 may further include or be coupled to memory 814 and / or 824 (internal or external), respectively, which may be coupled to processors 812 and 822, respectively, for storing information and instructions that may be executed by processors 812 and 822. Memory 814 (and memory 824) maybe one or more memories and of any type suitable to the local application environment, and may be implemented using any suitable volatile or nonvolatile data storage technology such as a semiconductor-based memory device, a magnetic memory device and system, an optical memory device and system, fixed memory, and / or removable memory. For example, memory 814 (and memory 824) can be comprised of any combination of random access memory (RAM), read only memory (ROM), static storage such as a magnetic or optical disk, hard disk drive (HDD), or any other type of non-transitory machine or computer readable media. The instructions stored in memory 814 and memory 824 may include program instructions or computer program code that, when executed by processors 812 and 822, enable the apparatuses 810 and / or 820 to perform tasks as described herein.

[0085] In certain example embodiments, apparatuses 810 and / or 820 may further include or be coupled to (internal or external) a drive or port that is configured to accept and read an external computer readable storage medium, such as an optical disc, USB drive, flash drive, or any other storage medium. For example, the external computer readable storage medium may store a computer program or software for execution by processors 812 and 822 and / or apparatuses 810 and / or 820 to perform any of the methods illustrated in FIGs. 4-7.

[0086] In some exemplary embodiments, an apparatus (e.g., apparatus 810 and / or apparatus 820) may include means for performing a method, a process, or any of the variants discussed herein. Examples of the means may include one or more processors, memory, controllers, transmitters, receivers, and / or computer program code for causing the performance of the operations.

[0087] Various exemplary embodiments may be directed to an apparatus, such as apparatus 810, that includes means for determining a set of contention-based preambles associated with a synchronization signal block index / physical broadcast channel block index per one or more valid physical random access channel occasions for multiple physical random access channel transmissions. The apparatus 810 may also include means for determining at least one preamble subset of the determined set of contention-based preambles and means for transmitting the multiple physical random access channel transmissions with a preamble from the determined preamblesubset.

[0088] Certain exemplary embodiments may be directed to an apparatus, such as apparatus 820, that includes means for selecting a set of contention-based preambles mapped to one or more groups of random access channel occasions for a plurality of transmissions and means for partitioning the set of preambles into a plurality of preamble subsets.

[0089] In some exemplary embodiments, apparatus 810 may also include or be coupled to one or more antennas 815 for receiving a downlink signal and for transmitting via an uplink from apparatus 810. Apparatuses 810 and / or 820 may further include transceivers 816 and 826, respectively, configured to transmit and receive information. The transceiver 816 and 826 may also include a radio interface that may correspond to a plurality of radio access technologies including one or more of GSM, LTE, LTE-A, 5G, NR, WLAN, NB-IoT, Bluetooth, BT-LE, NFC, RFID, UWB, or the like. The radio interface may include other components, such as filters, converters (for example, digital-to-analog converters or the like), symbol demappers, signal shaping components, an Inverse Fast Fourier Transform (IFFT) module, or the like, to process symbols, such as OFDMA symbols, carried by a downlink or an uplink.

[0090] For instance, transceivers 816 and 826 may be respectively configured to modulate information on to a carrier waveform for transmission, and demodulate received information for further processing by other elements of apparatuses 810 and / or 820. In other example embodiments, transceivers 816 and 826 may be capable of transmitting and receiving signals or data directly. Additionally or alternatively, in some example embodiments, apparatuses 810 and / or 820 may include an input and / or output device (I / O device). In certain example embodiments, apparatuses 810 and / or 820 may further include a user interface, such as a graphical user interface or touchscreen.

[0091] In certain example embodiments, memory 814 and memory 824 store software modules that provide functionality when executed by processors 812 and 822, respectively. The modules may include, for example, an operating system that provides operating system functionality for apparatuses 810 and / or 820. The memorymay also store one or more functional modules, such as an application or program, to provide additional functionality for apparatuses 810 and / or 820. The components of apparatuses 810 and / or 820 may be implemented in hardware, or as any suitable combination of hardware and software. According to certain example embodiments, apparatus 810 may optionally be configured to communicate with apparatus 820 via a wireless or wired communications link 830 according to any radio access technology, such as NR.

[0092] According to certain example embodiments, processors 812 and 822, and memory 814 and 824 may be included in or may form a part of processing circuitry or control circuitry. In addition, in some example embodiments, transceivers 816 and 826 may be included in or may form a part of transceiving circuitry.

[0093] As used herein, the term “circuitry” may refer to hardware-only circuitry implementations (for example, analog and / or digital circuitry), combinations of hardware circuits and software, combinations of analog and / or digital hardware circuits with software / firmware, any portions of hardware processor(s) with software, including digital signal processors, that work together to cause an apparatus (for example, apparatus 810 and / or 820) to perform various functions, and / or hardware circuit(s) and / or processor(s), or portions thereof, that use software for operation but where the software may not be present when it is not needed for operation. As a further example, as used herein, the term “circuitry” may also cover an implementation of merely a hardware circuit or processor or multiple processors, or portion of a hardware circuit or processor, and the accompanying software and / or firmware. The term circuitry may also cover, for example, a baseband integrated circuit in a server, cellular network node or device, or other computing or network device.

[0094] A computer program product may include one or more computer-executable components which, when the program is run, are configured to carry out some example embodiments. The one or more computer-executable components may be at least one software code or portions of it. Modifications and configurations required for implementing functionality of certain example embodiments may be performed as routine(s), which may be implemented as added or updated software routine(s).Software routine(s) may be downloaded into the apparatus.

[0095] As an example, software or a computer program code or portions of it may be in a source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers may include a record medium, computer memory, read-only memory, photoelectrical and / or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers. The computer readable medium or computer readable storage medium may be a non-transitory medium.

[0096] In other example embodiments, the functionality may be performed by hardware or circuitry included in an apparatus (for example, apparatuses 810 and / or 820), for example through the use of an application specific integrated circuit (ASIC), a programmable gate array (PGA), a field programmable gate array (FPGA), or any other combination of hardware and software. In yet another example embodiment, the functionality may be implemented as a signal, a non-tangible means that can be carried by an electromagnetic signal downloaded from the Internet or other network.

[0097] According to certain example embodiments, an apparatus, such as a node, device, or a corresponding component, may be configured as circuitry, a computer or a microprocessor, such as single-chip computer element, or as a chipset, including at least a memory for providing storage capacity used for arithmetic operation and an operation processor for executing the arithmetic operation.

[0098] The features, structures, or characteristics of example embodiments described throughout this specification may be combined in any suitable manner in one or more example embodiments. For example, the usage of the phrases “certain embodiments,” “an example embodiment,” “some embodiments,” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with an embodiment may beincluded in at least one embodiment. Thus, appearances of the phrases “in certain embodiments,” “an example embodiment,” “in some embodiments,” “in other embodiments,” or other similar language, throughout this specification do not necessarily refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments. Further, the terms “cell”, “node”, “gNB”, or other similar language throughout this specification may be used interchangeably.

[0099] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of two or more elements are joined by “and” or “or,” mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0100] One having ordinary skill in the art will readily understand that the disclosure as discussed above may be practiced with procedures in a different order, and / or with hardware elements in configurations which are different than those which are disclosed. Therefore, although the disclosure has been described based upon these example embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of example embodiments. Although the above embodiments refer to 5G NR and LTE technology, the above embodiments may also apply to any other present or future 3GPP technology, such as LTE-advanced, and / or fourth generation (4G) technology.

[0101] Partial Glossary:

[0102] 3GPP 3rd Generation Partnership Project

[0103] 5G 5th Generation

[0104] ACK Acknowledgement

[0105] DL Downlink

[0106] EMBB Enhanced Mobile Broadband

[0107] FDM Frequency Domain Multiplexing

[0108] gNB 5G or Next Generation NodeB

[0109] LTE Long Term Evolution

[0110] Msg Message

[0111] NR New Radio

[0112] PBCH Physical Broadcast Channel

[0113] PRACH Physical Random Access Channel

[0114] PUCCH Physical Uplink Control Channel

[0115] PUSCH Physical Uplink Shared Channel

[0116] RA Random Access

[0117] RAN Radio Access Network

[0118] RACH Random Access Channel

[0119] RedCap Reduced Capability

[0120] RNTI Radio Network Temporary Identity

[0121] RO RACH Occasion

[0122] RRC Radio Resource Control

[0123] RSRP Reference Signal Received Power

[0124] SIB1 System Information Block 1

[0125] SS Synchronization Signal

[0126] SSB Synchronization Signal Block

[0127] UE User Equipment

[0128] UL Uplink

[0129] URLLC Ultra Reliable Low Latency Communication

Claims

WE CLAIM:

1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: determine a set of contention-based preambles associated with a synchronization signal block index / physical broadcast channel block index per one or more valid physical random access channel occasions for multiple physical random access channel transmissions; determine at least one preamble subset of the determined set of contentionbased preambles; and transmit the multiple physical random access channel transmissions with a preamble from the determined preamble subset.

2. The apparatus according to claim 1 , wherein the at least one preamble subset is determined by partitioning the set of preambles into one or more preamble subsets.

3. The apparatus according to claim 2, wherein the at least one memory and the instructions, when executed by the at least one processor, further cause the apparatus at least to: determine a number of the one or more preamble subsets based on a number of different cell-specific values configured by a network for a number of the multiple physical random access channel transmissions.

4. The apparatus according to claim 2, wherein the at least one memory and the instructions, when executed by the at least one processor, further cause the apparatus at least to: determine the number of the one or more preamble subsets based on a number of values of multiple physical random access channel transmissions the one or more valid physical random access channel occasions are to be used for.

5. The apparatus according to any one of claims 1-4, wherein the at least one memory and the instructions, when executed by the at least one processor, further cause the apparatus at least to: determine, for a first random access channel occasion of each of groups of random access channel occasions, a number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped, wherein a number of preamble subsets is set as the number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped.

6. The apparatus according to any one of claims 1-5, wherein a size of each of the preamble subset is inversely proportional to the number of groups of random access channel occasions for a number of multiple physical random access channel transmissions in a reference time period.

7. The apparatus according to any one of claims 1-6, wherein the at least one memory and the instructions, when executed by the at least one processor, further cause the apparatus at least to: associate preambles in a preamble subset with a lowest index with a group of random access channel occasions for a largest value of the number of multiple physical random access channel transmissions and associate the remaining preambles with the remaining preamble subsets in decreasing order of value of the number of multiple physical random access channel transmissions; or associate preambles in a preamble subset with a lowest index with a group of random access channel occasions for a smallest value of the number of multiple physical random access channel transmissions and associate the remaining preambles with the remaining preamble subsets in increasing order of value of the number of multiple physical random access channel transmissions.

8. The apparatus according to any one of claims 1-7, wherein the one or more valid physical random access channel occasions are mapped to the groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions.

9. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: select a set of contention-based preambles mapped to one or more groups of random access channel occasions for a plurality of transmissions; and partition the set of preambles into one or more preamble subsets.

10. The apparatus according to claim 9, wherein the at least one memory and the instructions, when executed by the at least one processor, further cause the apparatus at least to: partition the set of preambles into the one or more preamble subsets based on a number of different cell-specific values configured for the plurality of transmissions.

11. The apparatus according to claim 9, wherein the at least one memory and the instructions, when executed by the at least one processor, further cause the apparatus at least to: partition the set of preambles into the one or more preamble subsets based on a number of groups of random access channel occasions which have different sizes.

12. The apparatus according to any one of claims 9-11, wherein the at least one memory and the instructions, when executed by the at least one processor, further cause the apparatus at least to: determine, for a first random access channel occasion of each of the one ormore groups of random access channel occasions, a number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped, wherein a number of preamble subsets is set as the number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped.

13. The apparatus according to any one of claims 9-12, wherein a size of each of the preamble subset is inversely proportional to the number of groups of random access channel occasions of a specific size in a reference time period.

14. The apparatus according to any one of claims 9-13, wherein the at least one memory and the instructions, when executed by the at least one processor, further cause the apparatus at least to: provide the one or more preamble subsets to a user equipment.

15. A method, comprising: determining a set of contention-based preambles associated with a synchronization signal block index / physical broadcast channel block index per one or more valid physical random access channel occasions for multiple physical random access channel transmissions; determining at least one preamble subset of the determined set of contentionbased preambles; and transmitting the multiple physical random access channel transmissions with a preamble from the determined preamble subset.

16. The method according to claim 15, wherein the at least one preamble subset is determined by partitioning the set of preambles into one or more preamble subsets.

17. The method according to claim 16, further comprising: determining a number of the one or more preamble subsets based on a number of different cell-specific values configured by a network for a number of the multiple physical random access channel transmissions.

18. The method according to claim 16, further comprising: determining the number of the one or more preamble subsets based on a number of values of multiple physical random access channel transmissions the one or more valid physical random access channel occasions are to be used for.

19. The method according to any one of claims 15-18, further comprising: determining, for a first random access channel occasion of each of groups of random access channel occasions, a number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped, wherein a number of preamble subsets is set as the number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped.

20. The method according to any one of claims 15-19, wherein a size of each of the preamble subset is inversely proportional to the number of groups of random access channel occasions for a number of multiple physical random access channel transmissions in a reference time period.

21. The method according to any one of claims 15-20, further comprising: associating preambles in a preamble subset with a lowest index with a group of random access channel occasions for a largest value of the number of multiple physical random access channel transmissions and associate the remaining preambles with the remaining preamble subsets in decreasing order of value of the number of multiple physical random access channel transmissions; orassociating preambles in a preamble subset with a lowest index with groups of random access channel occasions for a smallest value of the number of multiple physical random access channel transmissions and associate the remaining preambles with the remaining preamble subsets in increasing order of value of the number of multiple physical random access channel transmissions.

22. The method according to any one of claims 15-21, wherein the one or more valid physical random access channel occasions are mapped to the groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions.

23. A method, comprising: selecting a set of contention-based preambles mapped to one or more groups of random access channel occasions for a plurality of transmissions; and partitioning the set of preambles into one or more preamble subsets.

24. The method according to claim 23, further comprising: partitioning the set of preambles into the one or more preamble subsets based on a number of different cell-specific values configured for the plurality of transmissions.

25. The method according to claim 23, further comprising: partitioning the set of preambles into the one or more preamble subsets based on a number of groups of random access channel occasions which have different sizes.

26. The method according to any one of claims 23-25, further comprising: determining, for a first random access channel occasion of a group groups of random access channel occasions, a number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped,wherein a number of preamble subsets is set as the number of groups of random access channel occasions for different values of the number of multiple physical random access channel transmissions to which the first random access channel occasion is mapped.

27. The method according to any one of claims 23-26, wherein a size of each of the preamble subset is inversely proportional to the number of groups of random access channel occasions of a specific size in a reference time period.

28. The method according to any one of claims 23-27, further comprising: providing the one or more preamble subsets to a user equipment.

29. An apparatus, comprising: means for determining a set of contention-based preambles associated with a synchronization signal block index / physical broadcast channel block index per one or more valid physical random access channel occasions for multiple physical random access channel transmissions; means for determining at least one preamble subset of the determined set of con tention -based preambles; and means for transmitting the multiple physical random access channel transmissions with a preamble from the determined preamble subset.

30. An apparatus, comprising: means for selecting a set of contention-based preambles mapped to one or more groups of random access channel occasions for a plurality of transmissions; and means for partitioning the set of preambles into one or more preamble subsets.

31. A computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause theat least one processor to: determine a set of contention-based preambles associated with a synchronization signal block index / physical broadcast channel block index per one or more valid physical random access channel occasions for multiple physical random access channel transmissions; determine at least one preamble subset of the determined set of contentionbased preambles; and transmit the multiple physical random access channel transmissions with a preamble from the determined preamble subset.

32. A computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause the at least one processor to: select a set of contention-based preambles mapped to one or more groups of random access channel occasions for a plurality of transmissions; and partition the set of preambles into one or more preamble subsets.

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