Patent Publication Number: US-2022231806-A1

Title: Methods and apparatuses for a random access channel (rach) structure

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority under 35 U.S.C. § 120 as a continuation of PCT Patent Application No. PCT/CN2019/085404, filed on May 2, 2019, the disclosure of which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The disclosure relates generally to wireless communications and, more particularly, to methods and apparatuses for a random access channel (RACH) structure. 
     BACKGROUND 
     In the 3 rd  Generation Partnership Project (3GPP) standard (e.g., both the 4th Generation (4G) and the 5th Generation (5G) new radio (NR) mobile networks), before a wireless communication device (e.g., a user equipment (UE)) can send data to a base station (BS), the wireless communication device needs to perform uplink synchronization and downlink synchronization with the BS. The uplink timing synchronization can be achieved by performing a random access procedure via a suitable RACH structure. 
     SUMMARY 
     The example embodiments disclosed herein are directed to solving the issues relating to one or more of the problems presented in the prior art, as well as providing additional features that will become readily apparent by reference to the following detailed description when taken in conjunction with the accompany drawings. In accordance with various embodiments, example systems, methods, devices and computer program products are disclosed herein. It is understood, however, that these embodiments are presented by way of example and are not limiting, and it will be apparent to those of ordinary skill in the art who read the present disclosure that various modifications to the disclosed embodiments can be made while remaining within the scope of this disclosure. 
     In some embodiments, a method includes determining a mapping that associates a plurality of preambles to a plurality of channel resource units used to carry a plurality of payloads associated with the plurality of preambles by: determining that the plurality of channel resource units is carrying the plurality of payloads, determining that a set of preambles of the plurality of preambles is associated with a same beam, and prioritizing mapping the set of preambles to reference signals of the plurality of channel resource units corresponding to different code division multiplexing (CDM) groups. 
     In some embodiments, an apparatus including at least one processor and a memory, the at least one processor is configured to read code from the memory and implement a method that includes determining a mapping that associates a plurality of preambles to a plurality of channel resource units used to carry a plurality of payloads associated with the plurality of preambles by: determining that the plurality of channel resource units is carrying the plurality of payloads, determining that a set of preambles of the plurality of preambles is associated with a same beam, and prioritizing mapping the set of preambles to reference signals of the plurality of channel resource units corresponding to different CDM groups. 
     In some embodiments, a computer program product comprising a computer-readable program medium code stored thereupon, the code, when executed by at least one processor, causing the at least one processor to implement a method that includes determining a mapping that associates a plurality of preambles to a plurality of channel resource units used to carry a plurality of payloads associated with the plurality of preambles by: determining that the plurality of channel resource units is carrying the plurality of payloads, determining that a set of preambles of the plurality of preambles is associated with a same beam, and prioritizing mapping the set of preambles to reference signals of the plurality of channel resource units corresponding to different CDM groups. 
     In some embodiments, a method includes receiving, by a base station from a wireless communication device, data comprising a preamble of a plurality of preambles, a payload of a plurality of payloads, and a mapping that associates the plurality of preambles to a plurality of channel resource units used to carry the plurality of payloads associated with the plurality of preambles, and identifying a channel resource unit of the plurality of channel resource units based on the mapping. The channel resource unit is used to carry payload. A set of preambles of the plurality of preambles is associated with a same beam. The set of preambles is prioritized to be mapped to reference signals of the plurality of channel resource units corresponding to different CDM groups. 
     In some embodiments, an apparatus including at least one processor and a memory, the at least one processor is configured to read code from the memory and implement a method that includes receiving, by a base station from a wireless communication device, data comprising a preamble of a plurality of preambles, a payload of a plurality of payloads, and a mapping that associates the plurality of preambles to a plurality of channel resource units used to carry the plurality of payloads associated with the plurality of preambles, and identifying a channel resource unit of the plurality of channel resource units based on the mapping. The channel resource unit is used to carry payload. A set of preambles of the plurality of preambles is associated with a same beam. The set of preambles is prioritized to be mapped to reference signals of the plurality of channel resource units corresponding to different CDM groups. 
     In some embodiments, a computer program product comprising a computer-readable program medium code stored thereupon, the code, when executed by at least one processor, causing the at least one processor to implement a method that includes receiving, by a base station from a wireless communication device, data comprising a preamble of a plurality of preambles, a payload of a plurality of payloads, and a mapping that associates the plurality of preambles to a plurality of channel resource units used to carry the plurality of payloads associated with the plurality of preambles, and identifying a channel resource unit of the plurality of channel resource units based on the mapping. The channel resource unit is used to carry payload. A set of preambles of the plurality of preambles is associated with a same beam. The set of preambles is prioritized to be mapped to reference signals of the plurality of channel resource units corresponding to different CDM groups. 
     The above and other aspects and their implementations are described in greater detail in the drawings, the descriptions, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various example embodiments of the present solution are described in detail below with reference to the following figures or drawings. The drawings are provided for purposes of illustration only and merely depict example embodiments of the present solution to facilitate the reader&#39;s understanding of the present solution. Therefore, the drawings should not be considered limiting of the breadth, scope, or applicability of the present solution. It should be noted that for clarity and ease of illustration, these drawings are not necessarily drawn to scale. 
         FIG. 1A  is a signaling diagram illustrating an example 4-step RACH procedure, in accordance with an embodiment of the present disclosure. 
         FIG. 1B  is a signaling diagram illustrating an example 2-step RACH procedure, in accordance with an embodiment of the present disclosure. 
         FIG. 1C  is a signaling diagram illustrating an example uplink grant-free uplink data transmission procedure, in accordance with an embodiment of the present disclosure. 
         FIG. 2  illustrates a block diagram of a base station (BS), in accordance with some embodiments of the present disclosure. 
         FIG. 3  illustrates a block diagram of a wireless communication device, in accordance with some embodiments of the present disclosure. 
         FIG. 4  illustrates a flow chart for a method for managing data transmission (including a preamble and a payload) between a wireless communication device and a BS, in accordance with some embodiments of the present disclosure. 
         FIG. 5A  illustrates an evenly divided scenario of an example mapping scheme, in accordance with some embodiments of the present disclosure. 
         FIG. 5B  illustrates an evenly divided scenario of an example mapping scheme, in accordance with some embodiments of the present disclosure. 
         FIG. 5C  illustrates an unevenly divided scenario of an example mapping scheme, in accordance with some embodiments of the present disclosure. 
         FIG. 5CB  illustrates an unevenly divided scenario of an example mapping scheme, in accordance with some embodiments of the present disclosure. 
         FIG. 5D  is a diagram  500   d  illustrating the correspondence between an RO and beams, in accordance with some embodiments of the present disclosure. 
         FIG. 5E  is a diagram illustrating the correspondence between multiple ROs (RO group) and beams, in accordance with some embodiments of the present disclosure. 
         FIG. 5F  is a diagram illustrating association of a preamble index with POs based on CDM groups (with respect to the second and third example mapping scheme), in accordance with some embodiments of the present disclosure. 
         FIG. 5G  is a diagram illustrating association of a SSB set with POs based on CDM groups (with respect to the second and third example mapping scheme), in accordance with some embodiments of the present disclosure. 
         FIG. 6A  is a diagram illustrating FDM (frequency domain multiplexed) POs occupying consecutive time and frequency resources, in accordance with some embodiments of the present disclosure. 
         FIG. 6B  is a diagram illustrating TDM (time domain multiplexed) and FDM (frequency domain multiplexed) POs, in accordance with some embodiments of the present disclosure. 
         FIG. 6C  is a diagram illustrating POs occupying non-consecutive time and frequency resources, in accordance with some embodiments of the present disclosure. 
         FIG. 6D  is a diagram illustrating POs occupying time/frequency resources indicated by starting offsets and ending offsets of a boundary of non-consecutive time/frequency resources, in accordance with some embodiments of the present disclosure. 
         FIG. 6E  is a diagram illustrating POs occupying time/frequency resources indicated by starting offsets together with a number of the POs, in accordance with some embodiments of the present disclosure. 
         FIG. 7  illustrates a flow chart for a method for managing data transmission (including a preamble and a payload) between a wireless communication device and a BS, in accordance with some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS 
     Various example embodiments of the present solution are described below with reference to the accompanying figures to enable a person of ordinary skill in the art to make and use the present solution. As would be apparent to those of ordinary skill in the art, after reading the present disclosure, various changes or modifications to the examples described herein can be made without departing from the scope of the present solution. Thus, the present solution is not limited to the example embodiments and applications described and illustrated herein. Additionally, the specific order or hierarchy of steps in the methods disclosed herein are merely example approaches. Based upon design preferences, the specific order or hierarchy of steps of the disclosed methods or processes can be re-arranged while remaining within the scope of the present solution. Thus, those of ordinary skill in the art will understand that the methods and techniques disclosed herein present various steps or acts in a sample order, and the present solution is not limited to the specific order or hierarchy presented unless expressly stated otherwise. 
     In the 3GPP standard, a RACH procedure is used to obtain uplink timing synchronization between a wireless communication device (e.g., a UE) and a BS. The random access procedure can involve a 4-step RACH or a 2-step RACH. 
       FIG. 1A  is a signaling diagram illustrating an example 4-step RACH procedure  100   a , in accordance with an embodiment of the present disclosure. In the 4-step RACH procedure  100   a , a BS  120  performs downlink synchronization for a wireless communication device  110 , at  130   a . The wireless communication device  110  transmits a RACH preamble in Message  1  (“msg 1 ”) to the BS  120 , at  140   a . Responsive to the RACH preamble being received by the BS  120 , the BS  120  sends Message  2  (“msg 2 ”) back to the wireless communication device  110 , at  150   a . The msg 2  includes at least a medium access control (MAC) random access response (RAR) as a response to the RACH preamble. Responsive to the MAC RAR with corresponding random access preamble (RAP) identifier (ID) being received by the wireless communication device  110 , the wireless communication device  110  transmits Message  3  (“msg 3 ”) to the BS  120 , at  160   a . The msg 3  includes at least the grant carried in the MAC RAR, an identifier of the wireless communication device  110  (e.g., a UE ID), control information, and so on. Responsive to the BS  120  receiving the msg 3 , the BS  120  sends Message  4  (“msg 4 ”) back to the wireless communication device  110 , at  170   a . The msg 4  includes at least a radio resource control (RRC) established message, contention resolution ID for the purpose of contention resolution, and so on. 
     The 2-step RACH can be regarded as a simplified RACH process.  FIG. 1B  is a signaling diagram illustrating an example 2-step RACH procedure  100   b , in accordance with an embodiment of the present disclosure. In the 2-step RACH procedure  100   b , the BS  120  performs downlink synchronization for the wireless communication device  110 , at  130   b . The wireless communication device  110  transmits Message A (“msgA”) to the BS  120 , at  145   b . The msgA includes at least the msg 1  and the msg 3  of the 4-step RACH procedure  100   a . The msg 1  includes at least the preamble, which is carried on the physical RACH (PRACH). The msg 3  (e.g., including one or more of the grant, the identifier of the wireless communication device  110 , control information, and so on) can be regarded as a payload that is carried on physical uplink shared channel (PUSCH). Responsive to the RACH preamble being received by the BS  120 , the BS  120  sends Message B (“msgB”) back to the wireless communication device  110 , at  155   b . The msgB includes at least the msg 2  (e.g., MAC RAR) and/or the msg 4  (e.g., the RRC established message, the contention resolution ID, and so on) of the 4-step RACH procedure  100   a . As such, instead of two interactions (each interaction includes transmission of two messages or steps) as called for by the 4-step RACH procedure  100   a , the 2-step RACH procedure  100   b  needs one interaction between the BS  120  and the wireless communication device  110  to establish RRC connection. Accordingly, comparing to the 4-step RACH procedure  100   a , the 2-step RACH procedure  100   b  simplifies the RACH procedure, saves signaling overhead, reduces power consumption, and so on. 
     Each PUSCH resource unit corresponds to resources used to carry a payload. Each PUSCH resource unit can be defined based on time, frequency, and demodulation reference signal (DMRS). In some examples, a PUSCH resource unit encompasses a DMRS port and/or a DMRS sequence. The DMRS can be embedded in the payload transmission. 
     In the 2-step RACH procedure  100   b , the msgA includes a mapping between the preamble (carried on the PRACH) and the PUSCH resource unit (used to carry the payload such as but not limited to, the msg 3 ). The BS  120  can use the mapping included in the msgA to identify the PUSCH resource unit mapped to the preamble, in response to successfully receiving and decoding the preamble. 
     Principles and detailed mapping formula are disclosed for mapping M preambles to PUSCH resource units associated with the M preambles. The specification further provides association methods of M preambles and the PUSCH resource units as part of the mapping. The specification specifies mapping relationship/association method by formula explicitly or by descriptions of certain principle. 
     For each RACH occasion (RO), a certain number of preambles dedicated for the 2-step RACH procedure  100   b  are specified. The RO refers to the location of preamble transmission resource in time and frequency domains. The certain number of preambles are identified using preamble index numbers arranged in increasing order. For example, M preambles (from one or more ROs) can be arranged or ordered according an index-first, frequency-second, and time-third principle. The PUSCH resource units can also be arranged or ordered according to suitable criteria. Then, the mapping between the M preambles and the PUSCH resource units corresponds to associating/mapping the ordered preambles with/to the ordered PUSCH resource units. Depending on a mapping ratio (e.g., a ratio between M and a number of PUSCH resource units), the association/mapping between the preambles in each RO and associated PUSCH resource unit(s) can be one-to-one or multiple-to-one. 
     To avoid the timing offset impact on the orthogonal cover code (OCC) pattern and demodulation reference signal (DMRS) sequence division among different wireless communication devices during the RACH procedures, the PUSCH resource units associated with the same beam are assigned to different code division multiplexing (CDM) groups. For the 2-step RACH procedure  100   b , the preambles associated with the same beam are ordered consecutively, in increasing indexes. Following the aforementioned ordering principle, the PUSCH resource units associated with the same beam are more likely to be OCC pattern/DMRS sequence divided because a number of the CDM groups is smaller than a number of OCC patterns/DMRS sequences. Systems and methods are described herein for addressing such deficiencies in conventional systems. 
     In some examples, the channel structure of “preamble+payload” can be also implemented for uplink grant-free uplink data transmission.  FIG. 1C  is a signaling diagram illustrating an example uplink grant-free uplink data transmission procedure  100   c , in accordance with an embodiment of the present disclosure. In the uplink grant-free uplink data transmission procedure  100   c , the BS  120  performs downlink synchronization for the wireless communication device  110 , at  130   c . The wireless communication device  110  sends a message to the BS  120  in uplink, at  145   c . The message includes a preamble and a payload. The BS  120  sends a response at  155   c  back to the wireless communication device  155   c  in downlink, where the response includes an acknowledgement (ACK) or negative-acknowledgement (NACK). The payload of msgA of the 2-step RACH procedure  100   b  carries only control plane (CP) data. On the other hand, the content of the payload (e.g., of the message sent at  145   c ) for the grant-free uplink data transmission procedure  100   c  can include some user plane (UP) data. In the uplink grant-free uplink data transmission procedure  100   c , an RRC connection does not need to be established if the UP data is successfully decoded. Responsive to the preamble of the message of  145   c  being detected, the BS  120  is to identify the PUSCH resource unit carrying the payload of the message of  145   c . Therefore, also with respect to the uplink grant-free uplink data transmission procedure  100   c , a mapping between the preamble(s) and PUSCH resource unit(s) is needed. Accordingly, mapping scheme described herein can be likewise implemented for the message (which uses the “preamble+payload” configuration) communicated at  145   c.    
       FIG. 2  illustrates a block diagram of a BS  200 , in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1A-2 , the BS  200  is an example implementation of the BS  120 . In some examples, the BS  200  is an example of a node that can be configured to implement the various methods described herein. As shown in  FIG. 2 , the BS  200  includes a housing  240  containing a processor  204 , a memory  206 , a transceiver  210  including a transmitter  212  and a receiver  214 , a power module  208 , a communication module  216  including a mapping module  218 , and so on. 
     The processor  204  controls the general operation of the BS  200  and can include one or more processing circuits or modules such as a central processing unit (CPU) and/or any combination of general-purpose microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate array (FPGAs), programmable logic devices (PLDs), controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable circuits, devices and/or structures that can perform calculations or other manipulations of data. 
     The memory  206 , which can include both read-only memory (ROM) and random access memory (RAM), can provide instructions and data to the processor  204 . A portion of the memory  206  can also include non-volatile random access memory (NVRAM). The processor  204  typically performs logical and arithmetic operations based on program instructions stored within the memory  206 . The instructions (e.g., software) stored in the memory  206  can be executed by the processor  204  to perform the methods described herein. The processor  204  and memory  206  together form a processing system that stores and executes software. As used herein, “software” means any type of instructions, whether referred to as software, firmware, middleware, microcode, etc. which can configure a machine or device to perform one or more desired functions or processes. Instructions can include code (e.g., in source code format, binary code format, executable code format, or any other suitable format of code). The instructions, when executed by the one or more processors, cause the processing system to perform the various functions described herein. 
     The transceiver  210 , which includes the transmitter  212  and receiver  214 , allows the BS  200  to transmit and receive data to and from a remote device (e.g., another BS or a wireless communication device). An antenna  250  is typically attached to the housing  240  and electrically coupled to the transceiver  210 . In various embodiments, the BS  200  includes (not shown) multiple transmitters, multiple receivers, and multiple transceivers. In one embodiment, the antenna  250  is replaced with a multi-antenna array that can form a plurality of beams each of which points in a distinct direction. The transmitter  212  can be configured to wirelessly transmit packets having different packet types or functions, such packets being generated by the processor  204 . Similarly, the receiver  214  is configured to receive packets having different packet types or functions, and the processor  204  is configured to process packets of a plurality of different packet types. For example, the processor  204  can be configured to determine the type of packet and to process the packet and/or fields of the packet accordingly. 
     The communication module  216  can be implemented with the processor  204  and the memory  206  and is configured to perform communications between the BS  200  and a wireless communication device (e.g., the wireless communication device  110  of  FIGS. 1A-1C  and the wireless communication device  300  of  FIG. 3 ). For example, the communication module  216  is configured to perform BS-side operations in connection with at least the 4-step RACH procedure  100   a , the 2-step RACH procedure  100   b , and the uplink grant-free uplink data transmission procedure  100   c  as described herein. 
     In a communication system including the BS  200  that can serve one or more wireless communication devices, the BS  200  may receive a random access request or message (e.g., in the processes  100   a  or  100   b ) from a wireless communication device for access to the BS  200 . The BS  200  may also receive grant-free uplink data transmission from a wireless communication device (e.g., in the process  100   c ). 
     In one embodiment, the communication module  216  may generate messages responsive to the data transmission received from the wireless communication device and transmit the message via the transmitter  212  to the wireless communication device. 
     In connection with the 2-step RACH procedure  100   b  and the uplink grant-free uplink data transmission procedure  100   c  in which the “preamble+payload” configuration is used, the communication module  216  may receive, via the receiver  214  from the wireless communication device, data transmission including a preamble and a payload. The mapping module  218  is used to determine/identify locations of PUSCH resource units carrying the payload based on information (e.g., mapping information) in the preamble. 
     The power module  208  can include a power source such as one or more batteries, and a power regulator, to provide regulated power to each of the above-described modules of the BS  200 . In some embodiments, if the BS  200  is coupled to a dedicated external power source (e.g., a wall electrical outlet), the power module  208  can include a transformer and a power regulator. 
     The various modules discussed above are coupled together by a bus system  230 . The bus system  230  can include a data bus and, for example, a power bus, a control signal bus, and/or a status signal bus in addition to the data bus. It is understood that the modules of the BS  200  can be operatively coupled to one another using any suitable techniques and mediums. 
     Although a number of separate modules or components are illustrated in  FIG. 2 , persons of ordinary skill in the art will understand that one or more of the modules can be combined or commonly implemented. Conversely, each of the modules illustrated in  FIG. 2  can be implemented using a plurality of separate components or elements. 
       FIG. 3  illustrates a block diagram of a wireless communication device  300 , in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1A-3 , the wireless communication device  300  is an example implementation of the wireless communication device  110 . The wireless communication device  300  is an example of a device that can be configured to implement the various methods described herein. As shown in  FIG. 3 , the wireless communication device  300  includes a housing  340  containing a processor  304 , a memory  306 , a transceiver  310  including a transmitter  312  and a receiver  314 , a power module  308 , a communication module  316  including a mapping module  318 , and so on. 
     The processor  304  controls the general operation of the wireless communication device  300  and can include one or more processing circuits or modules such as a CPU and/or any combination of general-purpose microprocessors, microcontrollers, DSPs, FPGAs, PLDs, controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable circuits, devices and/or structures that can perform calculations or other manipulations of data. 
     The memory  306 , which can include both ROM and RAM, can provide instructions and data to the processor  304 . A portion of the memory  306  can also include NVRAM. The processor  304  typically performs logical and arithmetic operations based on program instructions stored within the memory  306 . The instructions (e.g., software) stored in the memory  306  can be executed by the processor  304  to perform the methods described herein. The processor  304  and memory  306  together form a processing system that stores and executes software. 
     The transceiver  310 , which includes the transmitter  312  and receiver  314 , allows the wireless communication device  300  to transmit and receive data to and from a remote device (e.g., a BS). An antenna  350  or a multi-antenna array is attached to the housing  340  and electrically coupled to the transceiver  310 . In various embodiments, the wireless communication device  300  includes (not shown) multiple transmitters, multiple receivers, and multiple transceivers. In one embodiment, the antenna  350  is replaced with a multi-antenna array that can form a plurality of beams each of which points in a distinct direction. The transmitter  312  can be configured to wirelessly transmit packets having different packet types or functions, such packets being generated by the processor  304 . Similarly, the receiver  314  is configured to receive packets having different packet types or functions, and the processor  304  is configured to process packets of a plurality of different packet types. For example, the processor  304  can be configured to determine the type of packet and to process the packet and/or fields of the packet accordingly. 
     The communication module  316  can be implemented with the processor  304  and the memory  306  and is configured to perform communications between the wireless communication device  300  and a BS (e.g., the BSs  120  and  200 ). For example, the communication module  316  is configured to perform UE-side operations in connection with at least the 4-step RACH procedure  100   a , the 2-step RACH procedure  100   b , and the uplink grant-free uplink data transmission procedure  100   c  as described herein. 
     In a communication system, the wireless communication device  300  may attempt to access a BS for data transfer. In one embodiment, the communication module  316  can generate a message including a preamble and a payload (e.g., in the 2-step RACH procedure  100   b  and the uplink grant-free uplink data transmission procedure  100   c ). 
     The communication module  316  can transmit messages (e.g., those in the 2-step RACH procedure  100   b  and the uplink grant-free uplink data transmission procedure  100   c ) via the transmitter  312  to the BS. The communication module  316  can receive, via the receiver  314  from the BS, a message in response to any message sent by the wireless communication device  300 . 
     In connection with the 2-step RACH procedure  100   b  and the uplink grant-free uplink data transmission procedure  100   c  in which the “preamble+payload” configuration is used, the communication module  316  may send, via the transmitter  312  to the BS, data transmission including a preamble and a payload. The mapping module  318  maps the PUSCH resource units carrying the payload to the preamble in the manner described. 
     The power module  308  can include a power source such as one or more batteries, and a power regulator, to provide regulated power to each of the above-described modules of the wireless communication device  300 . In some embodiments, if the wireless communication device  300  is coupled to a dedicated external power source (e.g., a wall electrical outlet), the power module  308  can include a transformer and a power regulator. 
     The various modules discussed above are coupled together by a bus system  330 . The bus system  330  can include a data bus and, for example, a power bus, a control signal bus, and/or a status signal bus in addition to the data bus. It is understood that the modules of the wireless communication device  300  can be operatively coupled to one another using any suitable techniques and mediums. 
     Although a number of separate modules or components are illustrated in  FIG. 3 , persons of ordinary skill in the art will understand that one or more of the modules can be combined or commonly implemented. Conversely, each of the modules illustrated in  FIG. 3  can be implemented using a plurality of separate components or elements. 
       FIG. 4  illustrates a flow chart for a method  400  for managing data transmission (including a preamble and a payload) between the wireless communication device  300  and the BS  200 , in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-4 , the method  400  is performed by the wireless communication device  300 . The method  400  involves prioritizing the preambles associated with the same Synchronization Signal Block (SSB) or beam to be associated with DMRS from different CDM groups. The remaining preambles and the remaining PUSCH resource units can be associated based on an increasing order of index, frequency, and time. 
     At  405 , the wireless communication device  300  (e.g., the mapping module  318 ) determines a mapping that associates a plurality of preambles to a plurality of channel resource units used to carry a plurality of payloads associated with the plurality of preambles. Examples of the channel resource units include but are not limited to, the PUSCH resource units. 
     In some examples, the mapping module  318  can determine information about the channel resource units based on configured values in system information block  2  (SIB 2 ) or RRC messages. The SIB 2  and the RRC messages may be broadcasted or otherwise sent by the BS  200 . The wireless communication device  200  receives the SIB 2  and the RRC messages from the BS  200 . 
     Examples of the configured values include but are not limited to, one or more of a number of frequency domain multiplexing PUSCH occasions (Nfdm), number of time domain multiplexing PUSCH occasions (Ntdm), a number of physical uplink shared channel (PUSCH) occasions (POs) Ni of a given time resources and frequency resources, a number of n demodulation reference signal (nDMRS) resources, a preamble to PUSCH resource unit mapping ratio X, offsets to associated RO, offsets configured for the POs following new radio (NR) configured grant principle, time frequency resource size of the POs, or synchronization signal block (SSB) associated with the PUSCH resource unit. As described, Ni stands for a number of POs of a given resource size. 
     The information about the set of channel resource units comprise at least one of a number of demodulation reference signal (DMRS) ports, a number of DMRS sequences, or a number of physical uplink shared channel (PUSCH) occasions (POs) within the set of channel resource units. 
     Block  405  includes at least blocks  408 ,  410 , and  420 . At  408 , the mapping module  318  determines that the plurality of channel resource units is carrying the plurality of payloads. At  410 , the mapping module  318  determines that a set of preambles (including one or more preambles) of the plurality of preambles is associated with a same beam. Beams are defined based on the SSB. Therefore, determining that the set of preambles of the plurality of preambles is associated with a same beam includes determining that the set of preambles of the plurality of preambles is associated with a same SSB. 
     At  420 , the mapping module  318  prioritizes mapping the set of preambles (associated with the same beam) to reference signals of the plurality of channel resource units corresponding to different CDM groups. Examples of the reference signals include but are not limited to, the DMRS. In some examples, prioritizing mapping the set of preambles to the reference signals of the plurality of channel resource units corresponding to the different CDM groups includes determining the reference signals corresponding to the different CDM groups based on a number of beams. In some examples, prioritizing mapping the set of preambles to the reference signals of the plurality of channel resource units corresponding to the different CDM groups includes converting first preamble indexes that identify the plurality of preambles into second preamble indexes that identify the plurality of preambles based on a number of beams, determining a CDM group indexes, and mapping the set of preambles to the reference signals of the plurality of channel resource units corresponding to the different CDM groups based on the second preamble indexes and the CDM group indexes. The mapping is described in further detail with respect to  FIGS. 5A-5C . 
     In some examples, prioritizing mapping the set of preambles to the reference signals of the plurality of channel resource units corresponding to the different CDM groups is referring to performing the mapping based the different CDM groups before performing the mapping based on one or more additional criteria. In some examples, the one or more additional criteria include, for example, indexes, frequencies, and time. After the priority mapping based on the CDM groups, additional preambles and channel resource units can be mapped according to the additional criteria. Thus, the method  400  further includes mapping additional preambles to additional channel resource units based on one or more of indexes, frequencies, and time, at  430 .  430  is performed after determining the additional preambles of the plurality of preambles other than the mapped set of preambles, and after determining the additional channel resource units of the plurality of channel resource units other than mapped channel resource units. 
     At  440 , the communication module  318  configures the transmitter  312  to send to the BS  200 , data that includes a preamble of the plurality of preambles, a payload of the plurality of payloads, and the mapping. 
     In some examples, the data corresponds to msgA of the 2-step RACH procedure  100   b . The msgA is sent by the wireless communication device  300  to the BS  200 . The preamble corresponds to a RACH preamble. The payload includes CP data. In some examples, the payload includes a grant, an identifier of the wireless communication device  300 , and control information. 
     In some examples, the data corresponds to a message of the uplink grant-free uplink data transmission procedure  100   c . The message is sent by the wireless communication device  300  to the BS  200 . The payload includes UP data. 
     At  450 , the communication module  318  configures the receiver  314  to receive from the BS  200 , a response. 
     Various example mapping schemes are presented as non-limiting approaches for performing the mapping, for example, at block  405 . The example mapping schemes are described in detail with reference to  FIGS. 5A-5F  and tables  1  and  2 . 
     For instance, a first example mapping scheme relate to the configuration mapping ratio being, for example, greater than 1, and with conventional ordering.  FIGS. 5A-5C  illustrate scenarios (evenly divided and unevenly divided) for the first example mapping scheme. “PUSCH resource unit” or “PUSCH unit” refers to a channel resource that carries a payload. 
       FIG. 5A  illustrates an evenly divided scenario  500   a  of the first example mapping scheme, in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-5A , in the evenly divided scenario  500   a , preambles with order indexes  0 - 3   511   a - 514   a  are mapped to or otherwise associated with PUSCH resource unit with ordering index  0   531   a . Preambles with order indexes  4 - 7   515   a - 518   a  are mapped to or otherwise associated with PUSCH resource unit with ordering index  1   532   a . Preambles with order indexes  8 - 11   519   a - 522   a  are mapped to or otherwise associated with PUSCH resource unit with ordering index  2   533   a . Preambles with order indexes  12 - 15   523   a - 526   a  are mapped to or otherwise associated with PUSCH resource unit with ordering index  3   534   a . Accordingly, each of the PUSCH resource units  531   a - 534   a  is mapped to 4 preambles. An example expression describing the evenly divided scenario  500   a  is: 
     PUSCH_unit_ordering_index=floor (preamble_ordering_index/X);
 
where PUSCH_unit_ordering_index refers to the ordering index of the PUSCH resource units  531   a - 534   a , preamble_ordering_index refers to the ordering index of the preambles  511   a - 526   a , and X corresponds to a mapping ratio (greater than 1). Here, X is 4.
 
       FIG. 5B  illustrates an evenly divided scenario  500   b  of the first example mapping scheme, in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-5B , in the evenly divided scenario  500   b , preambles with order index  0   511   b , order index  4   515   b , order index  8   519   b , and order index  12   523   b  are mapped to or otherwise associated with the PUSCH resource units with ordering index  0   531   b . The preambles with order index  1   512   b , order index  5   516   b , order index  9   520   b , and order index  13   524   b  are mapped to or otherwise associated with the PUSCH resource units with ordering index  1   532   b . The preambles with order index  2   513   b , order index  6   517   b , order index  10   521   b , and order index  14   525   b  are mapped to or otherwise associated with the PUSCH resource units with ordering index  2   533   b . The preambles with order index  3   514   b , order index  7   518   b , order index  11   522   b , and order index  15   526   b  are mapped to or otherwise associated with the PUSCH resource units with ordering index  3   534   b . Accordingly, each of the PUSCH resource units  531   b - 534   b  is mapped to 4 preambles. An example expression describing the evenly divided scenario  500   b  is: 
     PUSCH_unit_ordering_index=mod (preamble_ordering_index, Q);
 
where PUSCH_unit_ordering_index refers to the ordering index of the PUSCH resource units  531   b - 534   b , preamble_ordering_index refers to the ordering index of the preambles  511   b - 526   b , and Q corresponds to a total number of POs within a PO group (e.g., multiple POs) associated with the preambles. In an example, Q=12.
 
       FIG. 5C  illustrates an unevenly divided scenario  500   c  of the first example mapping scheme, in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-5C , in the unevenly divided scenario  500   c , preambles with order indexes  0 - 1   511   c - 512   c  are mapped to or otherwise associated with PUSCH resource unit with ordering index  0   531   c . Preambles with order indexes  2 - 3   513   c - 514   c  are mapped to or otherwise associated with PUSCH resource unit with ordering index  1   532   c . Preambles with order indexes  2 - 3   513   c - 514   c  are mapped to or otherwise associated with PUSCH resource unit with ordering index  1   532   c . Preambles with order indexes  4 - 5   515   c - 516   c  are mapped to or otherwise associated with PUSCH resource unit with ordering index  2   533   c . Preambles with order indexes  6 - 7   517   c - 518   c  are mapped to or otherwise associated with PUSCH resource unit with ordering index  3   534   c . Preambles with order indexes  8 - 9   519   c - 520   c  are mapped to or otherwise associated with PUSCH resource unit with ordering index  4   535   c . Preambles with order indexes  10 - 11   521   c - 522   c  are mapped to or otherwise associated with PUSCH resource unit with ordering index  5   536   c . Preambles with order indexes  12 - 13   523   c - 524   c  are mapped to or otherwise associated with PUSCH resource unit with ordering index  6   537   c . Preambles with order indexes  13 - 14   524   c - 525   c  are mapped to or otherwise associated with PUSCH resource unit with ordering index  7   538   c . None of the preambles  511   c - 526   c  are mapped to the PUSCH resource units with ordering indexes  8 - 11   539   c - 542   c , resulting in uneven mapping. These PUSCH resource units will not be used with the preambles for 2-step RACH transmission. An example expression describing the unevenly divided scenario  500   c  is: 
     PUSCH_unit_ordering_index=floor (preamble_ordering_index, X);
 
where PUSCH_unit_ordering_index refers to the ordering index of the PUSCH resource units  531   c - 542   c , preamble_ordering_index refers to the ordering index of the preambles  511   c - 526   c , and X corresponds to a mapping ratio (greater than 1). In one example, X is 2.
 
       FIG. 5CB  illustrates an unevenly divided scenario  500   cb  of the first example mapping scheme, in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-5CB , in the unevenly divided scenario  500   cb , a preamble with order index  0   511   cb  and a preamble with order index  12   523   cb  are mapped to or otherwise associated with a PUSCH resource unit with ordering index  0   531   cb . A preamble with an order index  1   512   cb  and a preamble with an order index  13   524   cb  are mapped to or otherwise associated with a PUSCH resource unit with ordering index  1   532   cb . A preamble with an order index  2   513   cb  and a preamble with an order index  14   525   cb  are mapped to or otherwise associated with a PUSCH resource unit with ordering index  2   533   cb . A preamble with an order index  3   514   cb  and a preamble with an order index  15   526   cb  are mapped to or otherwise associated with a PUSCH resource unit with an ordering index  3   534   cb . Preambles with order indexes  4 - 11   515   cb - 522   cb  are mapped to or otherwise associated with PUSCH resource units with ordering indexes  4 - 11   535   cb - 542   cb . An example expression describing the unevenly divided scenario  500   cb  is: PUSCH_unit_ordering_index=mod (preamble_ordering_index, Q); 
     where PUSCH_unit_ordering_index refers to the ordering index of the PUSCH resource units  531   cb - 542   cb , preamble_ordering_index refers to the ordering index of the preambles  511   cb - 526   cb , and X corresponds to a mapping ratio (greater than 1). In one example, Q is 12. 
     In the first example mapping scheme, the preamble ordering indexes and PUSCH resource unit ordering indexes can be obtained with the following principles: 
     In some examples, the preamble_ordering_index is obtained by rearranging the preambles from an RO or an RO group (containing multiple ROs) following an order principle such as: 
     (1) in increasing order of preamble indexes within a single RO; 
     (2) next, in increasing order of frequency resource indexes for frequency multiplexed ROs; 
     (3) next, in increasing order of time resource indexes for time multiplexed ROs. 
     In some examples, the PUSCH_unit_ordering_index is obtained by rearranging the PUSCH resource units following an order principle such as” 
     (1) in increasing order of DMRS indexes within a single PO; 
     (2) next, in increasing order of frequency resource indexes for frequency multiplexed POs; 
     (3) next, in increasing order of time resource indexes for time multiplexed POs; where the DMRS indexes are a linear transformation of DMRS port/sequence indexes. 
       FIG. 5D  illustrates a second example mapping scheme, in accordance with some embodiments of the present disclosure.  FIG. 5D  is a diagram  500   d  illustrating the correspondence between an RO and beams, in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-5D , each of SSBs  501   d - 504   d  corresponds to a respective one of beams  511   d - 514   d . The beams  511   d - 514   d  may differ from each other with respect to directions, as shown (the beams  511   d - 514   d  refer to the shaded beams). For instance, the direction of the beam  511   d  corresponds to SSB 0   501   d . The direction of the beam  512   d  corresponds to SSB 1   502   d . The direction of the beam  513   d  corresponds to SSB 2   503   d . The direction of the beam  514   d  corresponds to SSB 3   504   d . For an RO  520   d , a certain number (e.g., M) of preambles dedicated for the 2-step RACH procedure  100   b  are specified. In the diagram  500   d , a certain number (e.g., 4) SSBs (e.g., the SSBs  501   d - 504   d ) is assigned for the RO  520   d , e.g., SSBperRO=4. As such, the M preambles can be divided into 4 sets, where the preambles in each set have consecutive preamble indexes. The indexes between different preamble sets may not be consecutive. In one example in which M is 48, the preamble index numbers for a first preamble set may be 0-11, the preamble index numbers for a second preamble set may be 16-27, the preamble index numbers for a third preamble set may be 32-43, and the preamble index numbers for a fourth preamble set may be 48-59. 
       FIG. 5E  illustrates a third example mapping scheme.  FIG. 5E  is a diagram  500   e  illustrating the correspondence between an RO group (including multiple ROs) and beams, in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-5E , each of SSBs  501   e - 504   e  corresponds to a respective one of beams  511   e - 514   e . The beams  511   e - 514   e  may differ from each other with respect to directions, as shown (the beams  511   e - 514   e  refer to the shaded beams). For instance, the direction of the beam  511   e  corresponds to SSB 0   501   e . The direction of the beam  512   e  corresponds to SSB 1   502   e . The direction of the beam  513   e  corresponds to SSB 2   503   e . The direction of the beam  514   e  corresponds to SSB 3   504   e . For an RO group  530   e , a certain number (e.g., M) of preambles dedicated for the 2-step RACH procedure  100   b  are specified, where the preambles are from multiple ROs  520   e - 521   e  within the RO group  530   e . In the diagram  500   e , a certain number (e.g., 4) SSBs (e.g., the SSBs  501   e - 504   e ) is assigned for the RO group  530   e , e.g., SSBperRO=4. As such, the M preambles can be divided into 4 sets, where the preambles in each set have consecutive preamble indexes. The indexes between different preamble sets may not be consecutive and may come from different ROs. Therefore the indexes may be the same for the preamble set corresponding to different beams In one example in which Q is 48 and there are 2 ROs associated with, the preamble index numbers for a first preamble set may be 0-5, the preamble index numbers for a second preamble set may be 16-21, the preamble index numbers for a third preamble set may be 32-37, and the preamble index numbers for a fourth preamble set may be 48-53. 
     The wireless communication device  300  can use the preamble index to determine corresponding PUSCH resource units, which can be used by the BS  200  to determine the payload corresponding to the preamble. Each PUSCH resource unit can be determined based on time, frequency, DMRS. DMRS can be determined based on DMRS sequence, OCC, and CDM group. The PUSCH resource unit can be arranged to prioritize CDM groups, such that DMRSs from different CDM groups are assigned for the preambles allocated to the same beam or SSB. In one example in which 16 preambles are assigned to a given beam, and 18 CDM groups are present, the DMRSs from the 18 CDM are assigned to the PUSCH resource units corresponding to the 16 preambles. In another example in which 16 preambles are assigned to a given beam, and 12 CDM groups are present, the DMRSs from the 12 CDM are assigned to the PUSCH resource units corresponding to 12 of the 16 preambles. The remaining 4 preambles can be associated with remaining PUSCH resource units, for example, according to additional criteria such as time or frequency. 
       FIG. 5F  is a diagram  500   f  illustrating association of a preamble set  510   f  with POs  520   f  based on CDM groups (with respect to the second and third example mapping scheme), in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-5F , the POs  520   f  as shown form a PO group. As described, the POs  520   f  can be defined or otherwise determined based on frequency, time, and DMRS, and DMRS can be defined or otherwise determined based on OCC, CDM groups, and DMRS sequence. For example, the POs  520   f  as shown can be defined based on subblocks A-D on the frequency axis, where the subblocks are defined for frequency granularity. The POs  520   f  as shown are defined based on slots A and B in the time axis. Furthermore, all shaded components of the POs  520   f  correspond to DMRS of a first CDM group, and all empty components of the POs  520   f  correspond to DMRS of a second CDM group. Accordingly, the POs  520   f  can be defined based on DMRS of two CDM groups. 
     The preamble set  510   f  include the preamble index numbers of the RO  520   d  or the RO group  530   e . As shown in the diagram  500   f , the preamble set  510   f  for each SSB (e.g., for each i) is mapped to the POs  520   f  having different CDM groups. The mapping or association of a preamble set  510   f  with POs  520   f  can be based on a configurable mapping ratio. 
     With regard to the second example mapping scheme ( FIG. 5D ), the configuration mapping ratio can be, for example, 1, without sequence with re-shuffled DMRS index prioritizing CDM group followed by OCC pattern only. The association is fabricated beam-by-beam. The preamble ordering index can be obtained by rearranging the 2-step RACH preambles corresponding to a given beam following an example order principle such as: 
     (1) in increasing order of preamble indexes within a single RACH occasion; 
     (2) next, in increasing order of frequency resource indexes for frequency multiplexed PUSCH occasions; and 
     (3) next, in increasing order of time resource indexes for time multiplexed RACH occasions; 
     where DMRS indexes correspond to a linear transformation of DMRS port/sequence indexes. 
     In some examples, the PUSCH resource unit ordering index is obtained by rearranging the PUSCH resource units corresponding to a given beam following an example order principle such as a first example order principle, second example order principle, and third example order principle. 
     In the first example order principle: 
     (1) in increasing CDM group indexes of the DMRS of the POs within the PO group; and 
     (2) next, in increasing OCC pattern and/or DMRS sequences related indexes of the DMRS of the POs within the PO group. The POs are arranged first in increasing order of frequency resource indexes for frequency multiplexed POs. Next, the POs are arranged in an increasing order of time resource indexes for time multiplexed POs. 
     In the second example order principle: 
     (1) in increasing CDM group indexes of the DMRS of the POs within the PO group; 
     (2) next, in increasing order of frequency resource indexes for frequency multiplexed POs; 
     (3) next, in increasing order of time resource indexes for time multiplexed ROs; and 
     (4) next, in increasing OCC pattern and/or DMRS sequences related indexes of the DMRS of the POs within the PO group. 
     The third example order principle is used for OCC pattern and/or DMRS sequences available for 2 step RACH msgA transmission. In the third example order principle: 
     (1) in increasing CDM group indexes of the DMRS of the POs within the PO group; 
     (2) next, in increasing order of frequency resource indexes for frequency multiplexed POs; and 
     (3) next, in increasing order of time resource indexes for time multiplexed ROs. 
     For remaining preambles and DMRS (not associated per the principles above), the association can be performed following the order principle of the first example mapping scheme. 
     The DMRS index from  1  or multiple POs could be re-shuffled prioritizing CDM group from different POs followed by OCC pattern and/or DMRS sequences from different POs. With regard to the third example mapping scheme ( FIG. 5E,5F ), the PUSCH units could be associated with the preambles using the configured mapping ratio including e.g.{1,2,3}. 
       FIG. 5G  is a diagram  500   g  illustrating association of a SSB set  510   g  with POs  520   g  based on CDM groups (with respect to the second and third example mapping scheme), in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-5G , the diagram illustrates an embodiment in which the POs  520   g  are configured based on the SSB independently, such that the SSB (e.g., the SSB set  510   g ) is mapped directly to the PUSCH resource units (e.g., the POs  520   g ). The preamble to PUSCH resource unit mapping is based on the criterion of using the same beam, e.g., preambles and the PUSCH resource units that have been mapped to the same beam are mapped together. The POs  520   g  as shown form a PO group. As described, the POs  520   g  can be defined or otherwise determined based on frequency, time, and DMRS, and DMRS can be defined or otherwise determined based on OCC, CDM groups, and DMRS sequence. For example, the POs  520   g  as shown can be defined based on subblocks A-D on the frequency axis, where the subblocks are defined for frequency granularity. The POs  520   g  as shown are defined based on slots A and B in the time axis. Furthermore, all shaded components of the POs  520   g  correspond to DMRS of a first CDM group, and all empty components of the POs  520   g  correspond to DMRS of a second CDM group. Accordingly, the POs  520   g  can be defined based on DMRS of two CDM groups. 
     The SSB set  510   g  includes SSBs and can be mapped to the POs  520   g  based on the beam index i. As shown in the diagram  500   g , the SSB set  510   g  (e.g., for each beam i) is mapped to different CDM groups of the POs  520   g.    
     In a fourth example mapping scheme, suppose SSBperRO=4, and R preambles (e.g., M/4=R) are associated with each SSB  501   a - 504   a  or  501   b - 504   b . The R preambles are mapped to the DMRS from different CMD groups first with the increase of preamble index. An example formulation for the mapping may be based on the following: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 (SSB, preamble) 
                 (PO, DMRS pattern, CDM Group) 
               
               
                   
                   
               
             
            
               
                   
                 (k, r) 
                 (n, l, g) 
               
               
                   
                   
               
            
           
         
       
     
     The preamble index (preambleIdx) can be converted into an ordering index r within a given group, for example, using the following expression: 
         r =mod(preambleIdx,totalNumerof2stepRA_Preambles/ K ); 
     r=0, 1, 2, . . . R−1; 
     where preambleIdx denotes original preamble index numbers associated with the RO  520   a  or the group RO  530   b . The expression totalNumerof2stepRA_Preambles/K corresponds to a starting point. The totalNumerof2stepRA_Preambles is determined by the BS  200 , and corresponds to M. K denotes SSBperRO. 
     CDM group index g can be determined based on r, for example, using the following expression: 
         g =mod( r,G ); 
     where: r=n*G+g;
 
and G is a number of total CDM groups, and n is the index number for the PO. In one example, n can be determined using the following expression:
 
         n =floor( r,G ); 
     n=0, 1, 2 . . . , N−1;
 
g=0, 1, 2, . . . , G−1;
 
l=k;
 
k=0, 1, 2, . . . , K−1;
 
     The determination of l, g, n can be used to determine the PUSCH resource unit or a location thereof corresponding to the preamble. Accordingly, the preambles associated with the same SSB (beam) can be prioritized to be associated with DMRSs from different CDM groups. For the remaining preambles and PUSCH resource units, the increasing order of index/frequency/time can be pursued. 
     In a fifth example mapping scheme, a mapping formula is used for mapping as described herein, where the mapping formula has an upper bound for a number of SSBs associated with PO groups. In an illustrative example, suppose ssbperRO=4, and R preambles (e.g., M/4=R) are associated with each SSB  501   a - 504   a  or  501   b - 504   b . The R preambles are mapped to the DMRS from different CMD groups first with the increase of preamble index. In the second example, due to latency requirement, at most W beams (W SSBs) are allowed within a PO. An example formulation for the mapping may be based on the following: 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 (SSB, preamble) 
                 (PO, DMRS pattern, CDM Group) 
               
               
                   
                   
               
             
            
               
                   
                 (k, r) 
                 (n, l, g) 
               
               
                   
                   
               
            
           
         
       
     
     The preamble index (preambleIdx) can be converted into an ordering index r within a given group, for example, using the following expression: 
         r =mod(preambleIdx,totalNumerof2stepRA_Preambles/ K ); 
     r=0, 1, 2, . . . R−1; 
     where preambleIdx denotes original preamble index numbers associated with the RO  520   a  or the group RO  530   b . The expression totalNumerof2stepRA_Preambles/K corresponds to a starting point. The totalNumerof2stepRA_Preambles is determined by the BS  200 , and corresponds to M. K denotes SSBperRO. 
     CDM group index g can be determined based on r, for example, using the following expression: 
         g =mod( r,G ); 
     where: r=n*G+g;
 
and G is a number of total CDM groups, and n is the index number for the PO. In one example, n can be determined using the following expression:
 
         n =floor( r,G ); 
     n=0, 1, 2 . . . , N−1;
 
g=0, 1, 2, . . . , G−1;
 
l=k;
 
l=0, 1, 2, . . . , W−1;
 
     The determination of l, g, n can be used to define the PUSCH resource unit or a location thereof corresponding to the preamble. Accordingly, the preambles associated with the same SSB (beam) can be prioritized to be associated with DMRSs from different CDM groups. For the remaining preambles and PUSCH resource units, the increasing order of index/frequency/time can be pursued. 
     In a sixth example scheme, PUSCH resource units with different CDM groups are associated with a given beam with the following order 
     (1) in increasing CDM group indexes of the DMRS of the POs within the PO group; 
     (2) next, in increasing order of frequency resource indexes for frequency multiplexed POs; and 
     (3) next, in increasing order of time resource indexes for time multiplexed ROs. 
     The POs can be configured following the NR configured grant in principle. The mapping of preamble and PUSCH resources units could based on the criterion that the same beam is used. The mapping ratio could be configurable with values from{1,2,3}.In some examples, some variables are needed for associating the M preambles and N tot  PUSCH resource units. With respect to the relationship among such variables, the M preambles mapped to a PO or a PO group (including multiple POs) can correspond to one or multiple ROs. Multiple POs that are consecutive in the time domain and in the frequency domain belong to a PO group. Multiple ROs that are consecutive in the time domain and in the frequency domain belong to a RO group. In some examples, multiple ROs belong to a same PRACH slot. 
     In some examples, a number of preambles M can be determined using an expression such as: 
         M =( R*N   t   RA,slot   *N   f   RA,slot ); 
     where R is a number of preambles used for the 2-step RACH procedure  100   b  per RO, N t   RA,slot  and N f   RA,slot  are a number of time multiplexed ROs and a number of frequency multiplexed ROs configured in a RO group (including PRACH slot), respectively. 
     In some examples, a number of POs associated with the M preambles is referred to as Ng, and can be determined using an expression such as: 
         Ng =( N   p   *N   t   PO,group   *N   f   PO,group ); 
     where N p  is a number of PUSCH resource units per PO, N t   PO,group  and N f   PO,group  are a number of time multiplexed POs and a number of frequency multiplexed POs configured in a PO group, respectively. 
     In some examples, a number of total PUSCH resource units N tot  can be determined using an expression such as: 
         N   tot =Σ i=1   Ng   N   dmsr ( i );
 
     where Ng=1 included, and N dmsr  (i) can be determined using an expression such as: 
         N   dmsr ( i )= N   dmrs_cdm ( i )* N   dmrs_occ ( i )* N   dmrs_seq ( i ); 
     In some examples, N dmsr  (i) can be identical for all I, and signalling overhead reduction can be achieved. In an example in which N dmsr  (i) is identical for all i, N dmsr  (i) can be denoted as N dmrs . The minimum of Ng can be obtained from the following expression where M and the mapping ratio r can be described: 
         Ng =ceil( M /( N   dmsr   *r )); 
     where r can be broadcasted in the SI or in RRC messages, and the value of r can be defined as r={1, 2, 3}. 
     In some examples, Ng can be further defined using an expression such as: 
         Ng=Σ   i=1   N   Ni ; where 
     r=ceil (M/(Ng*N dmsr ));
 
In some examples, r can be derived from Ng. Ni denotes a number of POs of a given time and frequency resource size index f(i) that can either be fixed or broadcasted through SI (e.g. SIB 2 ) or RRC messages. The values of Ni can be identical or different with varying i. Alternatively, only N fdm  or N tdm  can be configured.
 
     The offset may not only be relative to the associated ROs. For example, the timing offset can also be configured separately from the ROs. 
     In some examples, the number of POs can be determined from the number of POs of any given time and frequency resource sizes as shown in  FIGS. 6A and 6B .  FIG. 6A  is a diagram illustrating FDM POs  600   a  occupying consecutive time and frequency resources, in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-6A , the POs  600   a  belong to a PO group, or the POs  600   a  include one or more POs associated with an RO or RO group. N 1  denotes a number (e.g., 2) of POs of a given time and frequency resource size index f( 1 ), and corresponds to DMRSs  601   a  and  602   a . N 2  denotes a number (e.g., 2) of POs of a given time and frequency resource size index f( 2 ), and corresponds to DMRSs  603   a  and  604   a . N 3  denotes a number (e.g., 2) of POs of a given time and frequency resource size index f( 3 ), and corresponds to DMRSs  605   a  and  606   a . The POs  600   a  are defined by corresponding Nfdm and Ntdm values as shown. Accordingly, the PO pattern and number of POs can be determined from Nfdm and Ntdm. 
       FIG. 6B  is a diagram illustrating TDM and FDM POs  600   b , in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-6B , the POs  600   b  belong to a PO group, or the POs  600   b  include one or more POs associated with an RO or RO group. N 1  denotes a number (e.g., 2) of POs of a given time and frequency resource size index f( 1 ), and corresponds to DMRSs  601   b  and  602   b . N 2  denotes a number (e.g., 2) of POs of a given time and frequency resource size index f( 2 ), and corresponds to DMRSs  603   b  and  604   b . N 3  denotes a number (e.g., 2) of POs of a given time and frequency resource size index f( 3 ), and corresponds to DMRSs  605   b  and  606   b . The POs  600   b  are defined by corresponding Nfdm and Ntdm values as shown. 
     In some examples, the PO pattern and number of POs can be determined from starting/ending timing frequency/offsets for each PO.  FIG. 6C  is a diagram illustrating POs  600   c  occupying non-consecutive time and frequency resources, in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-6C , as shown, the non-consecutive time and frequency resources are indicated by the offsets only. The offsets can follow either a configured grant principle or a relative location the associated ROs  610   c . The ΔTs and ΔFs as shown can be configured following a configured grant principle or relative to the one or more ROs  610   c  associated with the POs  600   c.    
     In some examples, the OCC pattern can be determined from a starting time/frequency offsets for consecutive POs.  FIG. 6D  is a diagram illustrating POs  600   d  occupying time/frequency resources indicated by starting offsets and ending offsets of a boundary of non-consecutive time/frequency resources, in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-6D , as shown, the offsets can include an ending part of some boundary between non-consecutive POs. The ΔT and ΔF as shown can be configured following a configured grant principle or relative to the one or more ROs  610   d  associated with the POs  600   d.    
     In some examples, the PO pattern and number of POs can be determined from a starting timing/frequency offset plus the Ni assigned.  FIG. 6E  is a diagram illustrating POs  600   e  occupying time/frequency resources indicated by starting offsets together with a number of the POs  600   e , in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-6E , in one example, the Ni assignment can follow the SSB to RO association rule in TR 38.213. 
     In some examples, the offset for the ending point of each PO can be saved if the PO time/frequency resource are broadcast or fixed in the specification. For the scenario where The POs are separately configured from the RO occasions, the offset can be configured following NR configured grant in principle. To save signaling, the number of each PO of different time and frequency resources can be fixed to be the same in the specification. 
       FIG. 7  illustrates a flow chart for a method  700  for managing data transmission (including a preamble and a payload) between the wireless communication device  300  and the BS  200 , in accordance with some embodiments of the present disclosure. Referring to  FIGS. 1B-7 , the method  700  is performed by the BS  200  and corresponds to the UE-side method  400 . The method  700  involves identifying the channel resource unit using the mapping determined by the wireless communication device  300  (e.g., in the method  400 ). 
     At  710 , the communication module  216  of the BS  200  receives, from the wireless communication device, data including a preamble of a plurality of preambles, a payload of a plurality of payloads, and a mapping that associates the plurality of preambles to a plurality of channel resource units used to carry the plurality of payloads associated with the plurality of preambles. A set of preambles of the plurality of preambles is associated with a same beam. The set of preambles is prioritized to be mapped to reference signals of the plurality of channel resource units corresponding to different CDM groups. 
     At  720 , the mapping module  218  identifies a channel resource unit of the plurality of channel resource units based on the mapping. The channel resource unit is used to carry the payload. 
     While various embodiments of the present solution have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. Likewise, the various diagrams may depict an example architectural or configuration, which are provided to enable persons of ordinary skill in the art to understand example features and functions of the present solution. Such persons would understand, however, that the solution is not restricted to the illustrated example architectures or configurations, but can be implemented using a variety of alternative architectures and configurations. Additionally, as would be understood by persons of ordinary skill in the art, one or more features of one embodiment can be combined with one or more features of another embodiment described herein. Thus, the breadth and scope of the present disclosure should not be limited by any of the above-described illustrative embodiments. 
     It is also understood that any reference to an element herein using a designation such as “first,” “second,” and so forth does not generally limit the quantity or order of those elements. Rather, these designations can be used herein as a convenient means of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must precede the second element in some manner. 
     Additionally, a person having ordinary skill in the art would understand that information and signals can be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits and symbols, for example, which may be referenced in the above description can be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. 
     A person of ordinary skill in the art would further appreciate that any of the various illustrative logical blocks, modules, processors, means, circuits, methods and functions described in connection with the aspects disclosed herein can be implemented by electronic hardware (e.g., a digital implementation, an analog implementation, or a combination of the two), firmware, various forms of program or design code incorporating instructions (which can be referred to herein, for convenience, as “software” or a “software module), or any combination of these techniques. To clearly illustrate this interchangeability of hardware, firmware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware, firmware or software, or a combination of these techniques, depends upon the particular application and design constraints imposed on the overall system. Skilled artisans can implement the described functionality in various ways for each particular application, but such implementation decisions do not cause a departure from the scope of the present disclosure. 
     Furthermore, a person of ordinary skill in the art would understand that various illustrative logical blocks, modules, devices, components and circuits described herein can be implemented within or performed by an integrated circuit (IC) that can include a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, or any combination thereof. The logical blocks, modules, and circuits can further include antennas and/or transceivers to communicate with various components within the network or within the device. A general purpose processor can be a microprocessor, but in the alternative, the processor can be any conventional processor, controller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other suitable configuration to perform the functions described herein. 
     If implemented in software, the functions can be stored as one or more instructions or code on a computer-readable medium. Thus, the steps of a method or algorithm disclosed herein can be implemented as software stored on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that can be enabled to transfer a computer program or code from one place to another. A storage media can be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. 
     In this document, the term “module” as used herein, refers to software, firmware, hardware, and any combination of these elements for performing the associated functions described herein. Additionally, for purpose of discussion, the various modules are described as discrete modules; however, as would be apparent to one of ordinary skill in the art, two or more modules may be combined to form a single module that performs the associated functions according embodiments of the present solution. 
     Additionally, memory or other storage, as well as communication components, may be employed in embodiments of the present solution. It will be appreciated that, for clarity purposes, the above description has described embodiments of the present solution with reference to different functional units and processors. However, it will be apparent that any suitable distribution of functionality between different functional units, processing logic elements or domains may be used without detracting from the present solution. For example, functionality illustrated to be performed by separate processing logic elements, or controllers, may be performed by the same processing logic element, or controller. Hence, references to specific functional units are only references to a suitable means for providing the described functionality, rather than indicative of a strict logical or physical structure or organization. 
     Various modifications to the implementations described in this disclosure will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other implementations without departing from the scope of this disclosure. Thus, the disclosure is not intended to be limited to the implementations shown herein, but is to be accorded the widest scope consistent with the novel features and principles disclosed herein, as recited in the claims below.