Coverage enhancement method and related equipment

Abstract

The invention discloses a coverage enhancement method and related equipment. The method is performed by a user equipment (UE), and includes transmitting a plurality of Physical Random Access Channel (PRACH) transmissions at a Random Access Channel (RACH) opportunity (RO), in which a Synchronization Signal Block (SSB) is mapped to one or more contiguous or non-contiguous ROs (Reverse Orientation), and transmitting a plurality of Physical Random Access Channel (PRACH) transmissions at a Random Access Channel (RACH) opportunities (RO), in which the SSB is mapped to the one or more contiguous or non-contiguous ROs (Reverse Orientation). Through the method, better coverage performance can be realized, and a mapping relation between a plurality of SSBs and a plurality of PRACH transmissions is realized.

Description

Technical Field

[0001] This application relates to wireless communication technologies. Specifically, it relates to a method for coverage enhancement and related devices, such as user equipment (UE) and base stations (BS) (such as gNB). Background Art

[0002] Wireless communication systems, such as third-generation (3G) mobile phone standards and technologies, are well known. Such 3G standards and technologies are developed by the Third Generation Partnership Project (3GPP). The third-generation wireless communication technologies were mainly developed to support mobile phone communication in macro cells. Communication systems and networks are gradually evolving towards broadband and mobile. In a cellular wireless communication system, a user equipment (UE) is connected to a radio access network (RAN) through a wireless link. The radio access network includes a group of base stations (BS), which provide wireless links for user equipment located within their covered cells and also provide an interface to the core network (CN), which is responsible for the overall control of the entire network. The radio access network and the core network each undertake functions related to the overall network.

[0003] 3GPP has developed the so-called Long-Term Evolution (LTE) system, i.e., the Evolved Universal Mobile Telecommunication System Terrestrial Radio Access Network (E-UTRAN), for mobile access networks, where one or more macro cells are supported by base stations called eNodeB or eNB (evolved Node B). LTE is further evolving to the so-called fifth-generation (5G) or new radio (NR) system, in which one or more cells are supported by base stations called next-generation Node B gNodeB (gNB).

[0004] The fifth-generation new radio (5G NR) standard will support a variety of services with very different requirements. These services include: Enhanced Mobile Broadband (eMBB) for high data rate transmission, Ultra-Reliable Low Latency Communication (URLLC) for devices with low latency and high link reliability, and Massive Machine-Type Communication (mMTC) that supports a large number of low-power devices, requires energy-efficient communication capabilities, and has a long life cycle.

[0005] The UE connects to the gNB through a random access (RA) procedure, which can be divided into two types: Contention Free Random Access (CFRA) and Contention-based Random Access (CBRA). For CFRA, the preamble is allocated by the gNB, and this preamble is called a dedicated random access preamble. The dedicated preamble can be provided to the UE through RRC signaling (the allocation of the preamble can be configured in the RRC message). Therefore, the UE can send this dedicated preamble without contention. For CBRA, the UE randomly selects a preamble from a preamble group shared with other UEs. This means that the UE may select the same preamble as other UEs, thus there is a risk of collision. The gNB uses a contention resolution mechanism to handle access requests. In this procedure, the access result is random, and not all random access requests can succeed.

[0006] The contention-free or contention-based RA procedure can adopt a four-step or two-step procedure. Taking the four-step contention-based random access procedure as an example, the UE first sends a contention-based PRACH preamble, also known as MSG1. After detecting this preamble, the gNB responds with a random-access response (RAR), also known as MSG2. The RAR contains an uplink grant for scheduling the UE to send a PUSCH transmission, that is, MSG3. In response to the RAR, the UE sends MSG3 containing the identifier (ID) for contention resolution. After receiving MSG3, the network sends a contention resolution message, also known as MSG4, which contains the contention resolution ID. The UE receives MSG4. If it finds that its own contention resolution ID is included, it will send an acknowledgment on the PUCCH, thus completing the four-step random access procedure.

[0007] The two-step random access procedure aims to reduce latency and control signaling overhead by reducing the round-trip period between the UE and the base station. This mechanism is achieved by combining the preamble (MSG1) with the scheduled PUSCH transmission (MSG3) into a single message (MSGA) sent by the UE to the gNB; at the same time, combining the random access response (MSG2) with the contention resolution message (MSG4) into a single message (MSGB) sent by the gNB to the UE. In the case where a dedicated preamble is allocated to the UE, both the two-step procedure and the four-step procedure can be applied to the CFRA scenario.

[0008] Before performing the four-step or two-step RA procedure, the UE reads one or more synchronization signal blocks (SSBs) broadcast by the gNB. In the NR system, each beam sent by the gNB corresponds to a different SSB, and the UE selects a specific beam for communication with the gNB. Based on the SSB of the selected beam, the UE can further read the system information block type 1 (SIB1), which carries information related to cell access and provides scheduling information for other system information blocks transmitted on that beam. When the UE sends the first message in the random access procedure to the gNB, it sends a specific pattern called the "preamble" (also known as the "RACH preamble", "PRACH preamble", or "sequence"). At the same time, the UE also needs to provide its identity to the gNB so that the gNB can address it in the next step. This identity is called the random access radio network temporary identity (RA-RNTI), which is determined according to the time slot when the preamble is sent.

[0009] Coverage is one of the key factors considered by operators when deploying commercial cellular communication networks, as it directly affects the quality of service, as well as capital expenditure (CAPEX) and operating expenses (OPEX). Although coverage is of great significance in the commercial success of NR, the coverage performance of NR has not been comprehensively evaluated, nor has it been systematically compared with traditional radio access technologies (RATs) considering all the details of NR specifications.

[0010] Compared with LTE, NR is designed for higher frequency ranges, such as 28 GHz or 39 GHz in FR2. In addition, more spectrum has been opened in the FR1 band in many countries, such as 3.5 GHz, which is generally higher than the frequencies used by LTE or 3G. Due to the higher frequencies, the wireless channel will inevitably face greater path loss, making it more challenging to maintain the requirement of not less than the quality of service of traditional RAT. One particularly important mobile application is voice service, for which ordinary users usually expect seamless coverage regardless of their location.

[0011] For FR1, NR can be deployed on newly allocated spectrum, such as 3.5 GHz, or on spectrum reclaimed from traditional networks (such as 3G and 4G). In both cases, the coverage issue will be a key consideration, especially considering that these bands are likely to carry critical mobile services such as voice and low-rate data. For FR2, during the self-assessment phase in the submission of IMT-2020, its coverage performance was not fully evaluated, and it was not included in the key considerations in the enhanced specifications of Rel-16. Therefore, it is particularly necessary to have a comprehensive and in-depth understanding of the NR coverage performance under the premise of supporting the latest NR specifications.

[0012] In Rel-17, PRACH is considered a bottleneck channel, and some companies have proposed solutions for multiple PRACH transmissions using the same transmission beam or different beams in the system information (SI), such as: mechanisms for triggering / initiating multiple PRACH transmissions, determination of the number of transmissions and transmission modes, differentiation between enhanced UEs and traditional UEs, and collision handling mechanisms that may occur with and without multiple PRACH transmissions. Unfortunately, due to time constraints, PRACH enhancements were not finally standardized. Some companies and function leaders have proposed potential methods for PRACH enhancement, but have not discussed them in detail. In previous RAN1 meetings, the issue of multiple PRACH transmissions using the same beam or different beams was discussed, and several consensuses were reached, such as: multiple PRACH transmissions using the same PRACH preamble and the same beam in one PRACH attempt; multiple PRACH transmissions are based on the time-domain resources of the RACH occasion (RO) for the same beam case; one or more RAR windows can be used; but the specific details are not clear. The following are the specific contents of the reached consensus.

[0013] Consensus:

[0014] For multiple PRACH transmissions using the same beam, at least the support for multiple PRACH transmissions using the same PRACH preamble in one random access attempt should be provided.

[0015] For Further Study (FFS): Whether different preambles can be used in multiple PRACH transmissions within a single random access attempt.

[0016] Consensus:

[0017] For multiple PRACH transmissions using the same beam, transmission on ROs at different time points should be supported at least.

[0018] FFS: Whether / how the starting RB (resource block) of the RO can be different in multiple PRACH transmissions at different time points.

[0019] FFS: Whether / how it is feasible to perform multiple PRACH transmissions within the same time point (e.g., for a UE with multiple transmit chains).

[0020] Consensus:

[0021] For multiple PRACH transmissions using the same beam, consider the following options for RAR monitoring:

[0022] Option 1: One RAR window corresponds to each PRACH transmission, and the RAR window follows the traditional design.

[0023] FFS: The allocation of RA-RNTI.

[0024] Option 2: All multiple PRACH transmissions share one RAR window.

[0025] FFS: The starting position of the RAR window.

[0026] FFS: The allocation of RA-RNTI.

[0027] In RAN meeting #94, a new Rel-18 work item on NR coverage enhancement was officially approved. The objective of this work item is to study potential coverage enhancement solutions for PRACH and waveforms applicable to FR1 and FR2 frequency bands, with the following specific objectives:

[0028] Specify the following PRACH coverage enhancement items (by RAN1 and RAN2):

[0029] Use the same beam for multiple PRACH transmissions for the four-step random access procedure.

[0030] Study and, where reasonable, specify the use of different beams for PRACH transmissions for the four-step random access procedure.

[0031] Note 1: PRACH enhancement is mainly for FR2, but can also be used for FR1 where applicable.

[0032] Note 2: The PRACH enhancement mainly targets short format PRACH and can also be extended to other formats when applicable.

[0033] Study and, if necessary, standardize the following power domain enhancement items:

[0034] Based on the results of the RAN4 work on "UE power ceiling increase for carrier aggregation (CA) and dual connectivity (DC)" in Rel-17, perform enhancements to achieve an increase in the UE power ceiling, provided that relevant regulations are complied with.

[0035] Note 1: This study will start after the RAN4 work on "UE power ceiling increase for CA and DC" is completed, depending on the conclusions of RAN4.

[0036] Note 2: This objective will be re-examined and further clarified in the RAN plenary session after the RAN4 work is completed, and discussions in the relevant working group (WG) will not be initiated until the scope of the objective is clear.

[0037] Note 3: It is expected that both RAN1 and RAN4 will participate in this work, and whether RAN4 or RAN1 will start first remains to be determined later.

[0038] Study enhancement techniques for reducing MPR (maximum power ratio) / PAR (peak-to-average power ratio), including using frequency domain spectrum shaping (with or without spectrum spreading) and DFT-S-OFDM and tone reservation techniques.

[0039] Standardize the enhanced support for dynamic switching between DFT-S-OFDM and CP-OFDM.

[0040] In previous RAN1 meetings, some potential coverage enhancement methods have been discussed; however, there are still some issues that need to be further improved. The present invention relates to a wireless communication system, especially for coverage enhancement in the uplink (UL) transmission. Summary of the Invention

[0041] The objective of this application is to provide a method and related device for coverage enhancement to achieve better coverage performance.

[0042] In a first aspect, an embodiment of this application provides a method for coverage enhancement, which is executed by a user equipment (UE). The method includes: transmitting multiple Physical Random Access Channel (PRACH) transmissions at a Random Access CHannel occasion (RO), where a Synchronization Signal Block (SSB) is mapped to one or more consecutive or non-consecutive ROs.

[0043] In a second aspect, an embodiment of the present application provides a method for coverage enhancement, which is executed by a base station (BS). The method includes: receiving, from a user equipment (UE), a plurality of Physical Random Access Channel (PRACH) transmissions on a Random Access CHannel occasion (RO), where a Synchronization Signal Block (SSB) is mapped to one or more consecutive or non-consecutive ROs.

[0044] In a third aspect, an embodiment of the present application provides a UE, including a processor configured to call and run program instructions stored in a memory to execute the method described in the first aspect.

[0045] In a fourth aspect, an embodiment of the present application provides a BS, including a processor configured to call and run program instructions stored in a memory to execute the method described in the second aspect.

[0046] In a fifth aspect, an embodiment of the present application provides a computer-readable storage medium for storing a computer program, which enables a computer to execute the method described in the first aspect or the second aspect.

[0047] In a sixth aspect, an embodiment of the present application provides a computer program product, which includes computer program instructions for enabling a computer to execute the method described in the first aspect or the second aspect.

[0048] In a seventh aspect, an embodiment of the present application provides a computer program, which, when running on a computer, enables the computer to execute the method described in the first aspect or the second aspect. Description of the Drawings

[0049] To more clearly illustrate the embodiments of the present application or related technologies, the drawings to be described in the embodiments are briefly introduced below. Obviously, the drawings are only some embodiments of the present application, and those of ordinary skill in the art can obtain other drawings based on these drawings without any cost.

[0050] Figure 1 is a block diagram of a user equipment and a base station in a communication control system according to an embodiment of the present application.

[0051] Figure 2 is a schematic diagram showing the radio protocol architecture in a gNB and a UE.

[0052] Figure 3It is a schematic diagram showing that the gNB further includes a centralized unit (CU) and multiple distributed units (DUs).

[0053] Figure 4 It is a flowchart of the coverage enhancement method according to the first embodiment of the present application.

[0054] Figure 5 It is a schematic diagram showing an exemplary mapping relationship between the time-based SSB and RO according to an embodiment of the present application.

[0055] Figure 6 It is a schematic diagram showing an exemplary mapping relationship between the SSB and RO based on time and frequency according to an embodiment of the present application.

[0056] Figure 7 It is a schematic diagram showing another exemplary mapping relationship between the SSB and RO based on time and frequency according to an embodiment of the present application.

[0057] Figure 8 It is a flowchart of the coverage enhancement method according to the second embodiment of the present application.

[0058] Figure 9 It is a flowchart of the coverage enhancement method according to the third embodiment of the present application. Detailed implementation manners

[0059] The technical content, structural features, achieved objectives and effects of the present application will be described in detail below with reference to the accompanying drawings. Specifically, the terms in the embodiments of the present application are only used for the purpose of describing specific embodiments, and are not intended to limit the present application.

[0060] In 3GPP Rel-17, although the PRACH has been identified as one of the bottleneck channels in related research, the coverage enhancement problem of the PRACH has not been solved. PRACH transmission is very critical in multiple processes, such as initial access and beam failure recovery. To achieve better coverage performance, some enhancement methods need to be introduced. This specification proposes some coverage enhancement methods for the PRACH channel. Through these methods, better coverage effects can be achieved.

[0061] In the 94th meeting of 3GPP RAN, multiple PRACH transmissions using the same beam for the four-step random access procedure have been approved. However, in the current 3GPP specifications, the random access channel (RACH) occasion (RO) is indicated by system information block 1 (SIB1), and a RACH sequence occupies only one RACH occasion for one transmission and does not repeat. Therefore, how to indicate the PRACH transmission mode with repetition still needs to be further determined. In addition, the relationship between the RACH repetition transmission occasion and the beam index also needs to be clarified.

[0062] Most importantly, how is the SSB mapped to the RO? In addition, the relationship between the SSB and the RACH preamble should also be determined (i.e., when the SSB is mapped to the RO, the index of the RO should be determined).

[0063] Similar to the triggering mechanism for Msg3 repeated transmission, in order to prevent the UE from overusing the PRACH repetition function (which may cause serious resource congestion), it is very important to establish the triggering conditions for using PRACH repeated transmission. Since the requirement for PRACH repetition is closely related to the coverage of the UE, the conditions used to trigger Msg3 repeated transmission (such as the configuration threshold based on SS-RSRP) can be borrowed to trigger PRACH repetition. These triggering conditions can also be associated with the power level of the UE because the final received power of the PRACH depends not only on the path loss (related to SS-RSRP) but also on the uplink transmit power (UL Txpower). Therefore, a connection can be established between the number of Msg3 repetitions and multiple PRACHs. In addition, in the current 5G NR specifications, whether to use the DFT-S-OFDM waveform is indicated by an RRC parameter called transformPrecoder. If a switch is to be made between the DFT-S-OFDM and CP-OFDM schemes, RRC reconfiguration of the relevant parameters is required. In the specification, there are 4 different RRC parameters related to or associated with enabling / disabling transform precoding (for different modes / types of PUSCH scheduling):

[0064] transformPrecoder in pusch-Config.

[0065] transformPrecoder in configuredGrantConfig.

[0066] msg3-transformPrecoder.

[0067] msgA-TransformPrecoder-r16。

[0068] However, compared with the CP-OFDM waveform, the DFT-S-OFDM waveform has a lower Peak-to-Average Power Ratio (PAPR), so it has more advantages in the scenario where the uplink coverage is limited. Currently, the uplink waveform is configured through RRC, and this limitation poses a significant obstacle to the cell-edge UEs switching to the DFT-S-OFDM waveform in practical applications.

[0069] Most importantly, what will be the relationship between Msg3 transmission and multiple PRACH transmissions? In addition, is it possible to implicitly determine the waveform used for Msg3 through multiple PRACH transmissions?

[0070] In the current 3GPP specification, after the transmission of the Random Access Preamble is completed, the UE starts the ra-ResponseWindow from the first PDCCH occasion (i.e., the first symbol of the earliest CORESET for which the UE is configured to receive the Type1-PDCCH CSS set), and its configuration is sourced from RACH-ConfigCommon. When PRACH retransmission is enabled, if the ra-ResponseWindow starts from the first PDCCH occasion after the end of the first PRACH retransmission occasion, it means that the UE needs to receive the RAR during the PRACH retransmission. In addition, the end of the ra-ResponseWindow also needs to be determined, for example, it can be based on the length of the ra-ResponseWindow, or based on both the length of the ra-ResponseWindow and the number of PRACH retransmissions. Therefore, how to determine the ra-ResponseWindow (including its start time and length) still needs further research.

[0071] Most importantly, the related issues regarding the RAR also need to be determined, such as the size of the RAR window, the start time of the RAR, the calculation method of the RA-RNTI, etc.

[0072] This application can be summarized as follows:

[0073] This application proposes a method for determining the relationship between an SSB and multiple PRACH transmission occasions, where one SSB can be mapped to multiple consecutive / non-consecutive ROs based on the time domain or frequency domain.

[0074] A time-based mechanism can be adopted to map an SSB to consecutive or non-consecutive ROs. An SSB can be associated with multiple ROs. When the UE transmits a PRACH on these ROs, the corresponding SSB will be indicated.

[0075] A mechanism based on the combination of time and frequency can be adopted to map an SSB to consecutive or non-consecutive ROs. First, it is a set of time-domain resources (this set of resources can be configured or predefined), then the combination of this set of time resources and different frequency resources, and finally the remaining set of time-domain resources.

[0076] This application proposes a method for determining the relationship between multiple PRACH transmissions and other transmissions (such as HARQ-ACK of Msg3 or Msg4).

[0077] When multiple PRACH transmissions are enabled, the repeated transmission of HARQ-ACK of Msg3 or Msg4 will be triggered simultaneously. The number of repetitions of HARQ-ACK of Msg3 or Msg4 is related to the number of multiple PRACH transmissions.

[0078] When multiple PRACH transmissions are enabled, the increase in the transmission power of the repeated transmission of HARQ-ACK of Msg3 or Msg4 will also be triggered simultaneously. The power increase value of the repeated transmission of HARQ-ACK of Msg3 or Msg4 is related to the number of multiple PRACH transmissions.

[0079] The waveform used for Msg3 transmission is related to multiple PRACH transmissions.

[0080] This application proposes a method for determining the RAR window and RA-RNTI when multiple PRACH transmissions using the same or multiple beams are enabled. One or more RAR windows and one or more RA-RNTIs can be determined.

[0081] Multiple RAR windows can be configured. The number of RAR windows is related to the number of beams used for multiple PRACH transmissions. In other words, when multiple PRACH transmissions using multiple beams are enabled, one RAR window is triggered after each beam. Each beam can correspond to one or more PRACH transmissions.

[0082] Multiple RAR windows can be determined. The number of RAR windows is related to a set of ROs for multiple PRACH transmissions. In other words, when multiple PRACH transmissions using the same or multiple beams are enabled, one RAR window is triggered after each set of ROs.

[0083] A single RAR window can also be determined. For multiple PRACH transmissions, only one RAR window is triggered.

[0084] Figure 1An embodiment according to the present application is shown for one or more user equipments (UEs) 10 and a base station (such as a gNB or eNB) 20 in a communication network system 30 to achieve wireless communication. The communication network system 30 includes one or more UEs 10 and the base station 20. One or more UEs 10 may include a memory 12, a transceiver 13, and a processor 11 connected to the memory 12 and the transceiver 13. The base station 20 may include a memory 22, a transceiver 23, and a processor 21 connected to the memory 22 and the transceiver 23. The processor 11 or 21 may be configured to execute the functions, processes, and / or methods described in this specification. Each layer of the radio interface protocol may be implemented in the processor 11 or 21. The memory 12 or 22 is operatively connected to the processor 11 or 21 for storing various information required to drive the operation of the processor 11 or 21. The transceiver 13 or 23 is operatively connected to the processor 11 or 21 for transmitting and / or receiving wireless signals.

[0085] The processor 11 or 21 may include an application-specific integrated circuit (ASIC), other chip sets, logic circuits, and / or data processing devices. The memory 12 or 22 may include a read-only memory (ROM), a random access memory (RAM), a flash memory, a memory card, a storage medium, and / or other storage devices. The transceiver 13 or 23 may include a baseband circuit for processing radio frequency signals. When these embodiments are implemented in software, the technologies described herein may be implemented by modules (such as procedures, functions, etc.) that perform the functions described herein. The above modules may be stored in the memory 12 or 22 and executed by the processor 11 or 21. The memory 12 or 22 may be implemented as an internal component of the processor 11 or 21, or may be located outside the processor 11 or 21, in which case they may be communicatively connected to the processor 11 or 21 in various ways known in the art. The user plane radio protocol architecture in the gNB and the UE is as Figure 2 shown, including an optional Service Data Adaptation Protocol (SDAP), a Packet Data Convergence Protocol (PDCP), a Radio Link Control (RLC), and a Medium Access Control (MAC) layer. In a radio access network (RAN) function separation architecture, as Figure 3As shown, the gNB further includes a centralized unit (CU) and multiple distributed units (DUs). The protocol stack of the CU includes the RRC layer, an optional SDAP layer, and the PDCP layer, while the protocol stack of the DU includes the RLC layer, the MAC layer, and the physical layer (PHY). The CU and the DU are connected through the F1 interface, which is located between the PDCP layer and the RLC layer.

[0086] This application proposes a method for determining the relationship between a synchronization signal block (SSB) and multiple PRACH transmission opportunities. An SSB can be mapped to multiple consecutive / non-consecutive random access opportunities (ROs) based on the time domain or frequency domain. In the current 3GPP specifications, for the random access procedure, beam information is carried by the RACH opportunity, and there are one-to-one, one-to-many, many-to-one, etc. relationships between the SSB and the ROs. Similarly, when PRACH retransmission is enabled, the existing relationship between the SSB and the ROs needs to be adjusted. The basic principle for determining the relationship between the SSB and the ROs is that all PRACH retransmissions use the same beam index; in some cases, multiple SSBs can also be mapped to PRACH retransmissions, and each SSB is associated with multiple ROs. In addition, the index of the RO can be determined based on one of the following mechanisms: a time-priority mechanism; a mechanism combining time and frequency; a mechanism combining time, frequency, and the RACH combination sequence. The following is a method that can be used to determine the relationship between the SSB and multiple PRACH retransmission opportunities:

[0087] Figure 4 Schematically shows a method for coverage enhancement according to the first embodiment of this application. In combination with Figure 1 Referring to Figure 4 , method 100 includes the following steps: In step 110, the UE sends multiple Physical Random Access Channel (PRACH) transmissions (i.e., PRACH retransmissions) on a random access opportunity (RO), where the Synchronization Signal Block (SSB) is mapped to one or more consecutive or non-consecutive ROs. The consecutive or non-consecutive ROs can span one or more time slots or subframes. The so-called "consecutive ROs" can mean that these ROs are at different time points and all ROs are in a valid or available state. Through this method, not only can better coverage performance be achieved, but also the mapping relationship between multiple SSBs and multiple PRACH transmissions can be realized.

[0088] In one embodiment, a time-based mechanism is adopted to map the SSB to consecutive or non-consecutive ROs, and the SSB is associated with multiple ROs in the time domain. More specifically, the SSB is mapped to ROs with the same frequency resources but different time-domain resources, and covers all the time-domain resources within a PRACH cycle. In another embodiment, a time- and frequency-based mechanism is adopted to map the SSB to consecutive or non-consecutive ROs in the following order: first, a set of time-domain resources, then different frequency resources corresponding to this set of time-domain resources, and finally the remaining set of time-domain resources. 6. The method according to claim 1, wherein the RO index is determined by a mechanism based on one of the following: a time-first mechanism, a time-and-frequency combination mechanism, or a combination mechanism based on time, frequency, and RACH sequence.

[0089] In one embodiment, the sorting of the RO index conforms to at least one of the following: sorting in ascending order according to the time resources within a PRACH time slot; sorting in ascending order according to multiple PRACH time slots; sorting in ascending order according to the RACH opportunities of frequency reuse; sorting in ascending order according to the time resources within a set of PRACH time slots; sorting in ascending order according to the frequency corresponding to a set of time resources within a set of PRACH time slots; sorting in ascending order according to the time resources within the remaining set of PRACH time slots; or sorting in ascending order according to the frequency corresponding to the remaining time resources within the remaining set of PRACH time slots.

[0090] In one embodiment, every consecutive number N of preamble indices is assigned to an RO in a PRACH time slot or a set of PRACH time slots. These ROs have at least one of the following characteristics: within a single RACH opportunity, the preamble indices are arranged in ascending order; within a PRACH time slot, the time-resource indices of the time-multiplexed ROs are arranged in ascending order; among multiple PRACH time slots, the time-resource indices of the time-multiplexed ROs are arranged in ascending order; within a set of PRACH time slots, the time-resource indices of the time-multiplexed ROs are arranged in ascending order; within the remaining set of PRACH time slots, the time-resource indices of the time-multiplexed ROs are arranged in ascending order; the frequency-resource indices of the frequency-multiplexed ROs are arranged in ascending order; within a set of PRACH time slots, the frequency-resource indices of the frequency-multiplexed ROs are arranged in ascending order; or within the remaining set of PRACH time slots, the frequency-resource indices of the frequency-multiplexed ROs are arranged in ascending order.

[0091] The following is a further detailed description of how to determine the relationship between the SSB and multiple PRACH retransmission opportunities:

[0092] For a scenario where the ROs for multiple PRACH transmissions are independent of single PRACH transmissions (traditional PRACH), this means that the ROs for multiple PRACH transmissions are specifically configured and these ROs are only used for performing PRACH transmissions more than once (i.e., repeated transmissions).

[0093] In the first possible implementation, a time-based mechanism can be adopted to map an SSB to consecutive or non-consecutive ROs. One SSB is associated with multiple ROs. When the UE transmits a PRACH on these ROs, it indicates the corresponding SSB. For example, as Figure 5 shown, assume there are two SSBs in total, denoted as SSB1 and SSB2 respectively, and the total number of ROs configured for multiple PRACH transmissions is 8, which are {RO1, RO2, RO3, RO4, RO5, RO6, RO7, RO8}. Then SSB1 is mapped to {RO1, RO2, RO3, RO4}, where this group of ROs is distributed at different time points; while SSB2 is mapped to {RO5, RO6, RO7, RO8}, and this group of ROs is also distributed at different time points. In some embodiments, the so-called "consecutive ROs" means that these ROs are at different time points and all ROs in this group are valid or available. In other embodiments, consecutive ROs can span one or more time slots or sub-frames. The mapping of ROs can be a consecutive mapping (i.e., one-to-one correspondence) or a non-consecutive mapping (i.e., non-one-to-one correspondence). In certain embodiments, the SSB with the smallest index is mapped to ROs with the same frequency resources but different time domain resources, and covers all time domain resources within the PRACH period.

[0094] In some embodiments, the arrangement order of RO indices can conform to the following rules:

[0095] The first one: The order increases according to the time resources within a PRACH time slot.

[0096] The second one: The order increases according to multiple PRACH time slots.

[0097] The third one: The order increases according to the RACH opportunities of frequency reuse.

[0098] In some embodiments, every consecutive N preamble indices are assigned to the ROs in a PRACH time slot:

[0099] The first one: Within a single RACH opportunity, the preamble indices are arranged in ascending order.

[0100] The second one: Within a PRACH time slot, the time resource indices of the time-multiplexed ROs are arranged in ascending order.

[0101] The third type: The frequency resource indices of the frequency - multiplexed ROs are arranged in ascending order.

[0102] In some other embodiments, every consecutive N preamble indices are assigned to the ROs in a set of PRACH time slots:

[0103] The first type: Within a single RACH occasion, the preamble indices are arranged in ascending order.

[0104] The second type: Within a PRACH time slot, the time resource indices of the time - multiplexed ROs are arranged in ascending order.

[0105] The third type: In multiple PRACH time slots, the time resource indices of the time - multiplexed ROs are arranged in ascending order.

[0106] The fourth type: The frequency resource indices of the frequency - multiplexed ROs are arranged in ascending order.

[0107] In some cases, the mapping relationship (one - to - one correspondence) between the SSB and the RO is one - to - one, that is, one SSB corresponds to one RO. In this case, among the ROs used for multiple PRACH transmissions, the first RO indicates the corresponding SSB information.

[0108] In some cases, the mapping relationship between the SSB and the RO is many - to - one, that is, multiple SSBs correspond to one RO. In this case, the first RACH sequence in multiple PRACH transmissions is used to indicate the SSB information.

[0109] In the second possible implementation manner, a mechanism based on the combination of time and frequency can be adopted to map one SSB to consecutive or non - consecutive ROs. The mapping order is: first, a set of time - domain resources (this set of resources can be configured or predefined), then the different frequency resources corresponding to this set of time resources, and finally the remaining set of time - domain resources. For example, as Figure 6 shown, assume that there are a total of two SSBs, denoted as SSB1 and SSB2 respectively, and the total number of ROs configured for multiple PRACH transmissions is 8, which are {RO1, RO2, RO3, RO4, RO5, RO6, RO7, RO8}. Then, SSB1 is mapped to {RO1, RO2, RO5, RO6}, and this set of ROs is distributed at different time points; while SSB2 is mapped to {RO3, RO4, RO7, RO8}, and this set of ROs is also distributed at different time points.

[0110] Another example is Figure 7As shown, assume that there are a total of 2 SSBs, namely SSB1 and SSB2, and the total number of ROs configured for multiple PRACH transmissions is 8, denoted as {RO1, RO2, RO3, RO4, RO5, RO6, RO7, RO8}. Then, SSB1 is mapped to {RO1, RO2, RO5, RO6}, where this set of ROs is at different time points; SSB2 is mapped to {RO3, RO4, RO7, RO8}, and this set of ROs is also at different time points.

[0111] In some embodiments, the so-called "consecutive ROs" means that these ROs are at different time points, and all ROs in this set are valid or available. In some other embodiments, consecutive ROs can span one or more time slots or sub-frames. The mapping of ROs can be consecutive (i.e., one-to-one correspondence) or non-consecutive (i.e., not one-to-one correspondence).

[0112] In some cases, the mapping relationship (association) between an SSB and an RO is one-to-one, that is, one SSB corresponds to one RO. In this case, among the ROs used for multiple PRACH transmissions, the first RO is used to indicate the corresponding SSB information.

[0113] In some cases, the mapping relationship (association) between an SSB and an RO is many-to-one, that is, multiple SSBs correspond to one RO. In this case, the first RACH sequence among multiple PRACH transmissions is used to indicate the SSB information.

[0114] In some embodiments, the arrangement order of RO indices can conform to the following rules:

[0115] The first one: increasing according to the time resources within a PRACH time slot.

[0116] The second one: increasing according to multiple PRACH time slots.

[0117] The third one: increasing according to the RACH opportunities of frequency reuse.

[0118] In some embodiments, every consecutive N preamble indices are assigned to the ROs in a PRACH time slot:

[0119] The first one: within a single RACH opportunity, the preamble indices are arranged in ascending order.

[0120] The second one: within a PRACH time slot, the time resource indices of time-multiplexed ROs are arranged in ascending order.

[0121] The third one: the frequency resource indices of frequency-multiplexed ROs are arranged in ascending order.

[0122] In some other embodiments, every consecutive N preamble indices are assigned to the ROs in a set of PRACH time slots:

[0123] The first one: within a single RACH occasion, the preamble indices are arranged in ascending order.

[0124] The second one: within a PRACH time slot, the time resource indices of the time-multiplexed ROs are arranged in ascending order.

[0125] The third one: among multiple PRACH time slots, the time resource indices of the time-multiplexed ROs are arranged in ascending order.

[0126] The fourth one: the frequency resource indices of the frequency-multiplexed ROs are arranged in ascending order.

[0127] In some embodiments, the sorting of the RO indices may comply with the following rules:

[0128] The first one: sort in ascending order according to the time resources within a set of PRACH time slots.

[0129] The second one: sort in ascending order according to the frequency corresponding to the set of time resources, where the set of time resources is determined based on the first step.

[0130] The third one: sort in ascending order according to the time resources within the remaining set of PRACH time slots.

[0131] The fourth one: sort in ascending order according to the frequency corresponding to the remaining set of time resources, where the set of time resources is determined based on the first step.

[0132] In some embodiments, when every consecutive N preamble indices are assigned to the ROs in a PRACH time slot, the following rules may be complied with:

[0133] The first one: within a single RACH occasion, the preamble indices are arranged in ascending order.

[0134] The second one: within a set of PRACH time slots, the time resource indices of the time-multiplexed ROs are arranged in ascending order.

[0135] The third one: within the set of PRACH time slots, the frequency resource indices of the frequency-multiplexed ROs are arranged in ascending order.

[0136] The fourth one: within the remaining set of PRACH time slots, the time resource indices of the time-multiplexed ROs are arranged in ascending order.

[0137] The fifth one: within the remaining set of PRACH time slots, the frequency resource indices of the frequency-multiplexed ROs are arranged in ascending order.

[0138] If the set of PRACH time slots is more than two, the sorting of the RO indexes will be determined in a cyclic manner based on the above step 3 and / or step 4 and / or step 5.

[0139] This application proposes a method for determining the relationship between multiple PRACH transmissions and other transmissions (such as HARQ-ACK of Msg3 or Msg4). Similar to the triggering mechanism of Msg3 retransmission, in order to prevent the UE from overusing the PRACH retransmission function (which may cause resource congestion), it is very important to establish the triggering conditions for PRACH reuse. Since whether PRACH retransmission is required is closely related to the coverage of the UE, when a UE enables multiple PRACH transmissions, it means that the UE is in a link environment with poor coverage. Similarly, the HARQ-ACK transmissions of Msg3 and Msg4 are also in a link with poor coverage. Therefore, when multiple PRACH transmissions are enabled, some parameters or mechanisms for PRACH retransmission can also be applied to the HARQ-ACK transmissions of Msg3 and Msg4. The following methods can be considered:

[0140] Figure 8 Shows a method for coverage enhancement according to the second embodiment of the present application. Combining Figure 1 Referring to Figure 8 , method 200 includes the following: In step 210, when multiple PRACH transmissions are enabled, the UE sends a retransmission of the Hybrid Automatic Repeat reQuest Acknowledgement (HARQ-ACK) of Msg3, MsgA, or Msg4. By this method, not only can better coverage performance be achieved, but also the relationship between multiple PRACH transmissions and other transmissions (such as HARQ-ACK of Msg3 or Msg4) can be clarified.

[0141] In one embodiment, the number of retransmissions of the HARQ-ACK of Msg3 or Msg4 is related to the number of multiple PRACH transmissions. In one example, the number of retransmissions of the HARQ-ACK of Msg3 or Msg4 is equal to the number of multiple PRACH transmissions. In another example, the number of retransmissions of the HARQ-ACK of Msg3 or Msg4 is equal to the number of multiple PRACH transmissions plus a delta value. In yet another example, the relationship between the number of retransmissions of the HARQ-ACK of Msg3 or Msg4 and the number of multiple PRACH transmissions is determined by a table. More specifically, for a certain specific PRACH format, the actual number of retransmissions of the HARQ-ACK of Msg3 or Msg4 is equal to the number of multiple PRACH transmissions plus a corresponding delta value.

[0142] In one embodiment, when multiple PRACH transmissions are enabled, the transmission power boost for the HARQ-ACK retransmission of Msg3 or Msg4 is triggered, and the value of this transmission power boost is related to the number of multiple PRACH transmissions.

[0143] In one embodiment, the waveform used for Msg3 or MsgA transmission is related to multiple PRACH transmissions. For example, when the number of multiple PRACH transmissions is greater than 1, the waveform used for subsequent Msg3 or MsgA transmission is DFT-S-OFDM; while when the number of multiple PRACH transmissions is equal to 1, the waveform of subsequent Msg3 transmission is determined based on the configuration.

[0144] The following are further details on how to determine the relationship between multiple PRACH transmissions and other transmissions (such as HARQ-ACK of Msg3 or Msg4):

[0145] In the first possible implementation, when multiple PRACH transmissions are enabled, the HARQ-ACK retransmission of Msg3 or Msg4 is also triggered simultaneously, and the number of retransmissions is related to the number of multiple PRACH transmissions.

[0146] For the HARQ-ACK retransmission of Msg3 or Msg4, the number of retransmissions can be determined according to any one of the following methods or a combination of the following methods:

[0147] The number of retransmissions of HARQ-ACK of Msg3 or Msg4 is equal to the number of multiple PRACH transmissions.

[0148] The number of retransmissions of HARQ-ACK of Msg3 or Msg4 is equal to the number of multiple PRACH transmissions plus a delta value, and this delta value can be predefined or configurable.

[0149] The number of retransmissions of HARQ-ACK of Msg3 or Msg4 is related to the number of multiple PRACH transmissions. The relationship between HARQ-ACK of Msg3 or Msg4 and multiple PRACH transmissions can be determined by a table, and this table can be predefined or configurable, as shown in Table 1. For a certain PRACH transmission with a specific PRACH format, the actual number of retransmissions of its HARQ-ACK of Msg3 or Msg4 is equal to: the number of multiple PRACH transmissions + the corresponding delta value.

[0150] Table 1: Relationship between multiple PRACH transmissions and HARQ-ACK of Msg3 or Msg4.

[0151]

[0152] In a second possible implementation, when multiple PRACH transmissions are enabled, it also simultaneously triggers an increase in the transmission power of HARQ-ACK retransmissions for Msg3 or Msg4. The value of the increased transmission power for HARQ-ACK retransmissions of Msg3 or Msg4 is related to the number of multiple PRACH transmissions.

[0153] In a third possible implementation, the waveform used for Msg3 / MsgA transmission is related to multiple PRACH transmissions. When the number of multiple PRACH transmissions is greater than 1, the waveform of subsequent Msg3 transmissions is DFT-S-OFDM, and the UE ignores the configuration of the msg3-transformPrecoder parameter. When the number of multiple PRACH transmissions is equal to 1, the waveform of subsequent Msg3 transmissions is determined according to the configuration of the msg3-transformPrecoder parameter. In some embodiments, the same mechanism and / or parameter values can also be reused for the transmission of MsgA. When the number of multiple PRACH transmissions is greater than 1, the waveform of subsequent MsgA transmissions is DFT-S-OFDM, and the UE ignores the configuration of the msgA-transformPrecoder parameter; when the number of multiple PRACH transmissions is equal to 1, the waveform of subsequent MsgA transmissions is determined according to the configuration of the msgA-transformPrecoder parameter.

[0154] This application proposes a method for determining the RAR window and RA-RNTI when the same or multiple beams are enabled for multiple PRACH transmissions. One or more RAR windows and one or more RA-RNTIs can be determined. In the current 3GPP specification, the UE starts the ra-ResponseWindow configured in RACH-ConfigCommon from the first PDCCH occasion (i.e., the first symbol of the earliest CORESET for which the UE is configured to receive the Type1-PDCCH CSS set) after the random access preamble transmission ends. When PRACH retransmission is enabled, if the ra-ResponseWindow starts from the first PDCCH occasion after the end of the first PRACH retransmission occasion, then the UE may need to receive the RAR during the PRACH retransmission. In addition, the end time of the ra-ResponseWindow also needs to be determined, for example, it can be based on the duration of the ra-ResponseWindow, or simultaneously based on the duration of the ra-ResponseWindow and the number of PRACH retransmissions. Therefore, how to determine the ra-ResponseWindow (including its start time and duration) requires further study. The following method can be considered.

[0155] Figure 9 shows a method for coverage enhancement according to the third embodiment of the present application. In combination with Figure 1 refer to Figure 9 , method 300 includes the following steps: In step 310, when enabling multiple PRACH transmissions using the same or multiple beams for RACH, the UE is configured by the base station (BS) with one or more random access response (RAR) windows (such as ra-ResponseWindow) to monitor RAR messages based on one or more random access radio network temporary identifiers (RA-RNTIs) from the base station. Through this method, not only better coverage performance is achieved, but also the determination of the start time and duration of the random access response window is realized.

[0156] In one embodiment, multiple RAR windows are configured, and the number of RAR windows is related to the number of beams used in multiple PRACH transmissions. In one example, one RAR window is triggered after the last RO of each beam. In another embodiment, multiple RAR windows are determined, and the number of RAR windows is related to the number of sets of random access occasions (ROs) in multiple PRACH transmissions. In one example, one RAR window is triggered after each set of ROs. For the case of configuring multiple RAR windows, the starting point of each RAR window can be based on the first RO or the first actual RO for PRACH transmission. In yet another embodiment, multiple PRACH transmissions trigger only one RAR window. For the case of a single RAR window, its starting point can be based on the first RO, the last RO, the first actual RO, the last actual RO, or any one RO in multiple PRACH transmissions.

[0157] In one embodiment, the RA-RNTI is determined based on the first RO in multiple PRACH transmissions. In another embodiment, the RA-RNTI is determined based on the last RO in multiple PRACH transmissions. In yet another embodiment, the RA-RNTI is determined based on a combination of all ROs, all actual ROs, a set of ROs, or a set of actual ROs in multiple PRACH transmissions.

[0158] The following is a further description of how to determine the RAR window and RA-RNTI when enabling the same or multiple beams for multiple PRACH transmissions:

[0159] In a first possible implementation, multiple RAR windows can be configured. The number of RAR windows is related to the number of beams used for multiple PRACH transmissions. In other words, when multiple PRACH transmissions with multiple beams are enabled, a RAR window is triggered after each beam. Each beam may be associated with one or more PRACH transmissions. In some embodiments, the starting point of each RAR window can be based on the first RO or the first RO that actually performs a PRACH transmission. Additionally, the size of the RAR window can be directly indicated by the gNB, or can be jointly determined based on the size of ra-ResponseWindow and a variable value, where the variable value is determined according to the RO situation in multiple PRACH transmissions.

[0160] In a second possible implementation, multiple RAR windows can be determined. The number of RAR windows is related to the set of ROs in multiple PRACH transmissions. In other words, when multiple PRACH transmissions with the same or multiple beams are enabled, a RAR window is triggered after each set of ROs. In some embodiments, the starting point of each RAR window can be based on the first RO or the first RO that actually performs a PRACH transmission. Additionally, the size of the RAR window can be directly indicated by the gNB, or can be jointly determined based on the size of ra-ResponseWindow and a variable value, where the variable value is determined according to the RO situation in multiple PRACH transmissions.

[0161] In a third possible implementation, a single RAR window can be determined. For multiple PRACH transmissions, only one RAR window is triggered. In some embodiments, the starting point of the RAR window can be based on the first RO, the last RO, the first actual RO, the last actual RO, or any one RO in multiple PRACH transmissions. Additionally, the size of the RAR window can be directly indicated by the gNB, or can be jointly determined based on the size of ra-ResponseWindow and a variable value (e.g., the size of ra-ResponseWindow plus the variable value), where the variable value is determined according to the RO situation in multiple PRACH transmissions. In some examples, the RO is a "remaining RO", which is the RO between the reference RO used to determine the starting point of the RAR window and the last RO in multiple PRACH transmissions.

[0162] In some embodiments, the RA-RNTI is determined based on the first RO in multiple PRACH transmissions. In some embodiments, the RA-RNTI is determined based on the last RO in multiple PRACH transmissions. In some embodiments, the RA-RNTI is determined based on the RO at the middle position in multiple PRACH transmissions. In some embodiments, the RA-RNTI is determined based on a combination of all ROs in multiple PRACH transmissions. In some embodiments, the RA-RNTI is determined based on a combination of all actual ROs in multiple PRACH transmissions. In some embodiments, the RA-RNTI is determined based on a combination of the first RO and the last RO in multiple PRACH transmissions. In some embodiments, the RA-RNTI is determined based on a combination of the first actual RO and the last actual RO in multiple PRACH transmissions. In some embodiments, the RA-RNTI is determined based on a combination of a set of ROs and a PRACH preamble sequence. In some embodiments, multiple RA-RNTIs may be determined based on multiple ROs, where each RO can be used to determine one RA-RNTI.

[0163] The commercial benefits of some embodiments are as follows: 1. Solve the problems in the prior art; 2. Achieve coverage enhancement; 3. Achieve better coverage performance; 4. Achieve the mapping relationship between multiple SSBs and multiple PRACH transmissions; 5. Determine the relationship between multiple PRACH transmissions and other transmissions (such as HARQ-ACK of Msg3 or Msg4); 6. Determine the start point and window size of the random access response window; 7. Provide good communication performance. Some embodiments of this application can be used in the following fields: 5G NR chipset suppliers; V2X communication system developers; various vehicle manufacturers, including cars, trains, trucks, buses, bicycles, motorcycles, safety helmets, etc.; unmanned aerial vehicles (UAVs); smartphone manufacturers; public safety communication devices; AR / VR device manufacturers (such as for gaming, conferences / seminars, education, etc.). Some embodiments of this application belong to the "technology / process" combination that can be adopted into the 3GPP specification for developing final products. Some embodiments of this application can also be applied to 5GNR unlicensed band communication. Some embodiments of this application propose specific technical mechanisms.

[0164] Embodiments of this application also provide a computer-readable storage medium for storing a computer program. The computer-readable storage medium enables a computer to execute the corresponding processing procedures in each method implemented by the UE / BS in the embodiments of this application. For the sake of brevity, the specific details are not described herein again.

[0165] Embodiments of the present application also provide a computer program product, including computer program instructions. The computer program product enables a computer to execute corresponding processing procedures in each of the methods implemented by the UE / BS in the embodiments of the present application. For the sake of brevity, specific details are not elaborated herein.

[0166] Embodiments of the present application also provide a computer program. The computer program enables a computer to execute corresponding processing procedures in each of the methods implemented by the UE / BS in the embodiments of the present application. For the sake of brevity, specific details are not elaborated herein.

[0167] The non-volatile computer-readable medium may include at least one of the following groups: hard disk, CD-ROM, optical storage device, magnetic storage device, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), and flash memory. In some embodiments, if each component is implemented by software, the software may be stored in a computer-readable medium and loaded into a computing system through a removable storage device. When a control module (e.g., software instructions or executable computer program code) is executed by a processor in a computer system, it causes the processor to execute the various functions described in the present invention.

[0168] In addition, the inventive concept can be applied to any circuit that performs signal processing functions in a network element. For example, it can be foreseen that semiconductor manufacturers may adopt the inventive concept in the design of stand-alone devices (such as microcontrollers or application-specific integrated circuits (ASICs) of digital signal processors (DSPs)) and / or any other subsystem components.

[0169] Those skilled in the art should understand that, in combination with the examples described in the embodiments disclosed in this specification, functional units and algorithm steps can be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are executed by hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions according to each specific application, but this should not be regarded as exceeding the protection scope of the present application.

[0170] Although the present disclosure has been described in connection with what are considered to be the most practical and preferred embodiments, it is to be understood that the disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements without departing from the scope of the broadest interpretation of the appended claims.

Claims

1. A method for coverage enhancement, performed by a user equipment (UE), characterized in that, it includes: sending multiple Physical Random Access Channel (PRACH) transmissions at a Random Access Opportunity (RO), where a Synchronization Signal Block (SSB) is mapped to one or more consecutive or non - consecutive ROs.

2. The method according to claim 1, characterized in that, the SSB is mapped to consecutive or non - consecutive ROs, and the SSB is associated with one or more ROs in the time domain.

3. The method according to claim 2, characterized in that, the SSB is mapped to the ROs with the same frequency domain resources and different time domain resources, and spans all time domain resources within a PRACH period.

4. The method according to claim 1, characterized in that, the SSB is mapped to consecutive or non - consecutive ROs in the following order: first, a set of time domain resources, then different frequency domain resources corresponding to the set of time domain resources, and then the remaining set of time domain resources.

5. The method according to claim 1, characterized in that, the consecutive ROs refer to the ROs at different time points, and all ROs are valid or available.

6. The method according to claim 1, characterized in that, the RO index is determined based on a time - first mechanism, or a time - and - frequency mechanism, or a time - frequency - and - RACH - sequence mechanism.

7. The method according to claim 1, characterized in that, the order of the RO index conforms to at least one of the following: the order increases based on the time resources within a single PRACH slot; the order increases based on multiple PRACH slots; the order increases based on the RACH opportunities with frequency reuse; the order increases based on the time resources within a set of PRACH slots; the order increases based on the frequency corresponding to a set of time resources within a set of PRACH slots; the order increases based on the time resources within the remaining set of PRACH slots; or the order increases based on the frequency corresponding to the remaining time resources within the remaining set of PRACH slots.

8. The method according to claim 1, characterized in that, the ROs have characteristics conforming to at least one of the following: within a single RACH opportunity, the preamble index increases; for ROs time - multiplexed within a PRACH slot, the time resource index increases; for ROs time - multiplexed in multiple PRACH slots, the time resource index increases; for ROs time - multiplexed within a set of PRACH slots, the time resource index increases; for ROs time - multiplexed within the remaining set of PRACH slots, the time resource index increases; for ROs with frequency reuse, the frequency resource index increases; for ROs with frequency reuse within a set of PRACH slots, the frequency resource index increases; or for ROs with frequency reuse within the remaining set of PRACH slots, the frequency resource index increases.

9. The method according to claim 1, characterized in that, it further includes: when multiple PRACH transmissions are enabled, sending a repeated transmission of a Hybrid Automatic Repeat reQuest - Acknowledgement (HARQ - ACK) for Msg3, MsgA, or Msg4.

10. The method according to claim 9, It is characterized in that the repetition times of the HARQ-ACK of the Msg3 or the Msg4 are related to the number of multiple PRACH transmissions.

11. The method according to claim 9, It is characterized in that the repetition times of the HARQ-ACK of the Msg3 or the Msg4 are determined by at least one of the following: the repetition times of the HARQ-ACK of the Msg3 or the Msg4 are equal to the number of multiple PRACH transmissions; the repetition times of the HARQ-ACK of the Msg3 or the Msg4 are equal to the number of the multiple PRACH transmissions plus an offset value; or the relationship between the repetition times of the HARQ-ACK of the Msg3 or the Msg4 and the number of the multiple PRACH transmissions is determined by a table.

12. The method according to claim 9, It is characterized in that for a specific PRACH format, the actual repetition times of the HARQ-ACK of the Msg3 or the Msg4 are equal to the number of the multiple PRACH transmissions plus the corresponding offset value.

13. The method according to claim 9, It is characterized in that it will trigger a transmission power boost for the HARQ-ACK retransmission of the Msg3 or the Msg4, and the boost value of the transmission power is related to the number of the multiple PRACH transmissions.

14. The method according to claim 9, It is characterized in that the waveform used for Msg3 or MsgA transmission is related to the multiple PRACH transmissions.

15. The method according to claim 9, It is characterized in that when the number of the multiple PRACH transmissions is greater than 1, the waveform used for subsequent Msg3 or MsgA transmission is DFT-S-OFDM; when the number of the multiple PRACH transmissions is equal to 1, the waveform used for subsequent Msg3 transmission is determined based on the configuration.

16. The method according to claim 1, It is characterized in that further comprising: when enabling the multiple PRACH transmissions using the same or multiple beams for RACH, configuring one or more random access response (RAR) windows to monitor RAR messages according to one or more random access radio network temporary identifiers (RA-RNTIs) from the base station.

17. The method according to claim 16, It is characterized in that multiple RAR windows are configured, and the number of the RAR windows is related to the number of beams used for the multiple PRACH transmissions.

18. The method according to claim 17, It is characterized in that one RAR window is triggered after the last RO of each beam.

19. The method according to claim 16, It is characterized in that multiple RAR windows are determined, and the number of the RAR windows is related to the number of sets of RACH opportunities (ROs) in the multiple PRACH transmissions.

20. The method according to claim 16, It is characterized in that the start of each RAR window is based on the first RO or the first actual RO for performing PRACH transmission.

21. The method according to claim 16, wherein, the start of the RAR window is based on the first RO, the last RO, the first actual RO, the last actual RO, or any one RO among the plurality of PRACH transmissions.

22. The method according to claim 16, wherein, the RA-RNTI is determined based on the first RO, the first actual RO, the last RO, or the last actual RO among the plurality of PRACH transmissions.

23. The method according to claim 16, wherein, the RA-RNTI is determined based on a combination of all ROs, all actual ROs, a set of ROs, or a set of actual ROs among the plurality of PRACH transmissions.

24. A method for coverage enhancement, performed by a base station BS, wherein, comprising: receiving, at a random access occasion RO, a plurality of physical random access channel PRACH transmissions from a user equipment UE, wherein a synchronization signal block SSB is mapped to one or more consecutive or non-consecutive ROs.

25. The method according to claim 24, wherein, the SSB is mapped to consecutive or non-consecutive ROs, and the SSB is associated with one or more ROs in the time domain.

26. The method according to claim 25, wherein, the SSB is mapped to the ROs with the same frequency domain resources and different time domain resources, and spans all time domain resources within a PRACH period.

27. The method according to claim 24, wherein, the SSB is mapped to consecutive or non-consecutive ROs in the following order: first a set of time domain resources, then different frequency domain resources corresponding to the set of time domain resources, and then the remaining set of time domain resources.

28. The method according to claim 24, wherein, the consecutive ROs refer to the ROs at different time points, and all ROs are valid or available.

29. The method according to claim 24, wherein, the RO index is determined based on a time-first mechanism, or a time-and-frequency mechanism, or a time-frequency-and-RACH sequence mechanism.

30. The method according to claim 24, wherein, the order of the RO index conforms to at least one of the following: the order increases based on time resources within a single PRACH time slot; the order increases based on multiple PRACH time slots; the order increases based on RACH occasions with frequency reuse; the order increases based on time resources within a set of PRACH time slots; the order increases based on the frequency corresponding to a set of time resources within a set of PRACH time slots; the order increases based on time resources within the remaining set of PRACH time slots; or the order increases based on the frequency corresponding to the remaining time resources within the remaining set of PRACH time slots.

31. The method according to claim 24, wherein, the ROs conform to at least one of the following: within a single RACH occasion, the preamble index increases; for ROs time-division multiplexed within a PRACH time slot, the time resource index increases; ROs time - multiplexed in multiple PRACH time slots, with the time resource index incrementing; ROs time - multiplexed within a set of PRACH time slots, with the time resource index incrementing; ROs time - multiplexed within the remaining set of PRACH time slots, with the time resource index incrementing; Frequency - multiplexed ROs, with the frequency resource index incrementing; Frequency - multiplexed ROs within a set of PRACH time slots, with the frequency resource index incrementing; or Frequency - multiplexed ROs within the remaining set of PRACH time slots, with the frequency resource index incrementing.

32. The method according to claim 24, wherein, further comprising: When multiple PRACH transmissions are enabled, receiving repeated transmissions of hybrid automatic repeat request acknowledgments (HARQ - ACKs) for Msg3, MsgA, or Msg4.

33. The method according to claim 32, wherein, The number of repetitions of the HARQ - ACK for Msg3 or Msg4 is related to the number of multiple PRACH transmissions.

34. The method according to claim 32, wherein, The number of repetitions of the HARQ - ACK for Msg3 or Msg4 is determined by at least one of the following: The number of repetitions of the HARQ - ACK for Msg3 or Msg4 is equal to the number of multiple PRACH transmissions; The number of repetitions of the HARQ - ACK for Msg3 or Msg4 is equal to the number of multiple PRACH transmissions plus an offset value; or The relationship between the number of repetitions of the HARQ - ACK for Msg3 or Msg4 and the number of multiple PRACH transmissions is determined by a table.

35. The method according to claim 32, wherein, For a specific PRACH format, the actual number of repetitions of the HARQ - ACK for Msg3 or Msg4 is equal to the number of multiple PRACH transmissions plus the corresponding offset value.

36. The method according to claim 32, wherein, It triggers a transmission power boost for the repeated transmission of the HARQ - ACK for Msg3 or Msg4, and the boost value of the transmission power is related to the number of multiple PRACH transmissions.

37. The method according to claim 32, wherein, The waveform used for Msg3 or MsgA transmission is related to the multiple PRACH transmissions.

38. The method according to claim 32, wherein, When the number of multiple PRACH transmissions is greater than 1, the waveform used for subsequent Msg3 or MsgA transmission is DFT - S - OFDM; when the number of multiple PRACH transmissions is equal to 1, the waveform used for subsequent Msg3 transmission is determined based on the configuration.

39. The method according to claim 24, wherein, further comprising: When the multiple PRACH transmissions using the same or multiple beams are enabled, the UE is configured with one or more random access response (RAR) windows for monitoring RAR messages based on one or more random access radio network temporary identifiers (RA-RNTIs).

40. The method according to claim 39, wherein, a plurality of RAR windows are configured, and the number of the RAR windows is related to the number of beams used for the multiple PRACH transmissions.

41. The method according to claim 40, wherein, a RAR window is triggered after the last RO of each beam.

42. The method according to claim 39, wherein, a plurality of RAR windows are determined, and the number of the RAR windows is related to the number of sets of random access occasions (ROs) in the multiple PRACH transmissions.

43. The method according to claim 39, wherein, the start of each RAR window is based on the first RO or the first actual RO for which the PRACH transmission is performed.

44. The method according to claim 39, wherein, the start of the RAR window is based on the first RO, the last RO, the first actual RO, the last actual RO, or any one RO in the multiple PRACH transmissions.

45. The method according to claim 39, wherein, the RA-RNTI is determined based on the first RO, the first actual RO, the last RO, or the last actual RO in the multiple PRACH transmissions.

46. The method according to claim 39, wherein, the RA-RNTI is determined based on a combination of all ROs, all actual ROs, a set of ROs, or a set of actual ROs in the multiple PRACH transmissions.

47. A user equipment (UE), wherein, comprising a processor configured to call and run program instructions stored in a memory to perform the method according to any one of claims 1 to 23.

48. A base station (BS), wherein, comprising a processor configured to call and run program instructions stored in a memory to perform the method according to any one of claims 24 to 46.

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