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EP-4055972-B1 - METHOD AND APPARATUS FOR PRACH REPETITIONS

EP4055972B1EP 4055972 B1EP4055972 B1EP 4055972B1EP-4055972-B1

Inventors

  • LIU, HONGMEI
  • YAN, Zhi
  • LI, YINGYING
  • ZHANG, YUANTAO
  • LEI, HAIPENG

Dates

Publication Date
20260506
Application Date
20191108

Claims (13)

  1. A user equipment, UE, for wireless communication, comprising: at least one processor; and at least one memory coupled with at least one processor and configured to cause the UE to: receive (702) signaling information for indicating a synchronization signal block, SSB, group size; map (704) indices of a plurality of SSBs to a plurality of physical random access channel, PRACH, occasions 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, wherein the indices of the plurality of SSBs to the plurality of PRACH occasions are mapped in the following order: 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 determine (706) a set of PRACH occasions corresponding to one of the indices of the plurality of SSBs from the plurality of PRACH occasions based on the mapping.
  2. The UE according to Claim 1, wherein the plurality of PRACH occasions are valid PRACH occasions.
  3. The UE according to claim 1, wherein: the signaling information indicates the SSB group size with a value; or the signaling information implicitly indicates the SSB group size by indicating an amount of time domain PRACH occasions for each SSB group; or the signaling information implicitly indicates the SSB group size by indicating an amount of time and frequency domain PRACH occasions for each SSB group; or the signaling information implicitly indicates the SSB group size by indicating an amount of SSBs associated with one time domain PRACH occasion of the plurality of PRACH occasions; or the signaling information implicitly indicates the SSB group size by indicating an amount of SSBs associated with one time and frequency domain PRACH occasion of the plurality of PRACH occasions.
  4. The UE according to claim 1, wherein the mapping is periodically performed, and each mapping cycle is associated with the number of PRACH repetitions.
  5. The UE according to claim 4, wherein each mapping cycle starts from a configured or predefined time domain position, and a duration of each mapping cycle is a smallest value that all the indices of the plurality of SSBs can be mapped to the plurality of PRACH occasions for the number of PRACH repetitions.
  6. The UE according to Claim 4, wherein an index of a first mapped SSB group of the one or more SSB group within a first mapping cycle is predefined or configured, and optionally wherein an index of a first mapped SSB group of the one or more SSB group within each mapping cycle is the same.
  7. The UE according to Claim 6, wherein an index of a first continuously mapped SSB group of the one or more SSB group within a non-initial mapping cycle is increased by a relative offset with respect to that of a previous mapping cycle of the non-initial mapping cycle.
  8. The UE according to Claim 7, wherein: the relative offset with respect to that of a previous mapping cycle of the non-initial mapping cycle is an amount of time domain PRACH occasions per SSB group; or the relative offset with respect to that of a previous mapping cycle of the non-initial mapping cycle is an index step of the one or more SSB group.
  9. A base station for wireless communication, comprising: at least one processor; and at least one memory coupled with at least one processor and configured to cause the base station to: transmit (802) signaling information for indicating a synchronization signal block, SSB, group size; map (804) indices of a plurality of SSBs to a plurality of physical random access channel, PRACH, occasions 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 the indices of the plurality of SSBs to the plurality of PRACH occasions are mapped in the following order: 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 respond (806) to a PRACH preamble transmitted on a number of PRACH occasions corresponding to one of the indices of the plurality of SSBs based on the mapping.
  10. A method for wireless communication by a user equipment, comprising: receiving (702) signaling information for indicating a synchronization signal block, SSB, group size; mapping (704) indices of a plurality of SSBs to a plurality of physical random access channel, PRACH, occasions 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, wherein the indices of the plurality of SSBs to the plurality of PRACH occasions are mapped in the following order: 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 determining (706) a set of PRACH occasions corresponding to one of the indices of the plurality of SSBs from the plurality of PRACH occasions based on the mapping.
  11. A method for wireless communication by a base station, comprising: transmitting (802) signaling information for indicating a synchronization signal block, SSB, group size; mapping (804) indices of a plurality of SSBs to a plurality of physical random access channel, PRACH, occasions 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, wherein the indices of the plurality of SSBs to the plurality of PRACH occasions are mapped in the following order: 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 responding (806) to a PRACH preamble transmitted on a number of PRACH occasions corresponding to one of the indices of the plurality of SSBs based on the mapping.
  12. A processor for a user equipment comprising: at least one controller coupled with at least one memory and configured to cause the processor to: receive (702) signaling information for indicating a synchronization signal block, SSB, group size; map (704) indices of a plurality of SSBs to a plurality of physical random access channel, PRACH, occasions 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, wherein the indices of the plurality of SSBs to the plurality of PRACH occasions are mapped in the following order: 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 determine (706) a set of PRACH occasions corresponding to one of the indices of the plurality of SSBs from the plurality of PRACH occasions based on the mapping.
  13. A processor for a base station, comprising: at least one controller coupled with at least one memory and configured to cause the processor to: transmit (802) signaling information for indicating a synchronization signal block, SSB, group size; map (804) indices of a plurality of SSBs to a plurality of physical random access channel, PRACH, occasions 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, wherein the indices of the plurality of SSBs to the plurality of PRACH occasions are mapped in the following order: 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 respond (806) to a PRACH preamble transmitted on a number of PRACH occasions corresponding to one of the indices of the plurality of SSBs based on the mapping.

Description

TECHNICAL FIELD Embodiments of the present application generally relate to wireless communication technology, especially to a user equipment, base station, methods, and processors for physical random access channel (PRACH) repetitions. BACKGROUND In new radio (NR) light, due to the restrictions of uplink transmitting (Tx) antenna number and uplink transmission power, PRACH repetition in time domain, i.e., repeating the PRACH transmission for the same PRACH preamble in time domain is necessary to achieve the same uplink coverage as legacy technology, e.g., NR R15. However, to achieve the PRACH repetition, several problems have to be solved. For example, in the case of mapping synchronization signal blocks (SSBs) to PRACH occasions for PRACH repetition, when there are more than one time domain PRACH occasions mapped to the SSBs in a mapping cycle, whether to go through SSBs in order of indices first or to repeat PRACH transmissions first should be determined, so that both the network side and UE side have the same understanding of the mapping. Meanwhile, without any enhancement, the PRACH repetitions for a specific SSB will disperse in time domain, which will cause quite long time for random access. In addition, the maximum number of PRACH repetitions supported by PRACH occasions in time domain, and the coexistence with legacy technology etc. should also be considered. Thus, there is a need for further complementing and improving the technical solutions for PRACH repetition, e.g., mapping between SSBs and PRACH occasions. Panasonic: "NR-U PRACH resource enhancement", 3GPP draft; R1-1904595 describes PRACH resource enhancements in time domain and frequency domain. CN 109 041 593 A discloses a method and apparatus for configuring Random Access (RA), an RA method and apparatus, a base station, User Equipment (UE) and a computer-readable storage medium. The RA configuration method may include: grouping multiple Synchronization Signal Blocks (SSBs) and selecting a primary SSB from each SSB group; sending UE indication information indicating a primary SSB in a SSB group to be sent; sending at most one SSB in each SSB group to be sent to the UE; and sending the number of SSBs corresponding to preambles in each RA Channel (RACH) Occasion (RO) and the number of Ros under Frequency Division Multiplexing (FDM) to the UE. ZTE et al: "Remaining issues of msgA channel structure", 3GPP draft; R1-1910002 describes details on exact available values such as MCS and time-frequency resource size of PO, mapping design between RACH preambles and PUSCH resource units, and views on validation rules, hopping and repetition. Nokia et al: "Summary of Remaining Details on RACH Procedure", 3GPP draft; R1-1801097 describes a list of open issues relating to RACH procedures. SUMMARY One object of the embodiments of the present application is to provide technical solutions for PRACH repetitions, especially, a mapping mechanism between SSBs and PRACH occasions for PRACH repetitions. According to aspects of the present disclosure, there are provided a user equipment according to claim 1, a base station according to claim 9, methods according to claims 10 and 11, and processors according to claims 12 and 13. Any embodiment, aspect, example or implementation not being part of the claims, is only presented as information. Embodiments of the present application propose technical solutions for PRACH repetitions, especially for the mapping between SSBs and PRACH occasions for PRACH repetitions. Meanwhile, embodiments of the present application consider the coexistence with legacy technology. Thus, embodiments of the present application will great facilitate the implementation of 5G NR including NR light. BRIEF DESCRIPTION OF THE DRAWINGS In order to describe the manner in which advantages and features of the application can be obtained, a description of the application is rendered by reference to specific embodiments thereof, which are illustrated in the appended drawings. These drawings depict only example embodiments of the application and are not therefore to be considered limiting of its scope. FIGS. 1-4 illustrate exemplary embodiments of mapping between SSBs and PRACH occasions depending on the specific setting of "msg1-FDM" and "ssb-perRACH-Occasion AndCBPreamblesPerSSB";FIG. 5 illustrates an exemplary mapping between SSBs and PRACH occasions according to some embodiments of the present application;FIG. 6A and FIG. 6B respectively illustrate an exemplary mapping between SSBs and PRACH occasions according to some embodiments of the present application;FIG. 7 illustrates an exemplary method for PRACH repetitions according to some embodiments of the present application;FIG. 8 illustrates another exemplary method for PRACH repetitions according to some other embodiments of the present application;FIG. 9A illustrates an exemplary mapping between SSBs and PRACH occasions under the mechanism of PRACH repetition starting position cycling according to